Peripheral fuel injection with rate shaping to improve efficiency, emissions, and noise signatures in diesel engines

Abstract

A system may include an engine head including surface configured to be disposed adjacent the hollow cylinder of the engine head. The system may further include one or more fuel injectors disposed adjacent the surface, the fuel injectors including an outlet configured to be disposed adjacent a cylinder periphery of the hollow cylinder of the engine. The system may further include a controller in communication with the one or more fuel injectors. The controller may be configured to operate the one or more fuel injectors to (i) dispense a first volume of fuel at a first time and for a first duration from a first fuel injector, and (ii) dispense a second volume of fuel at a second time and for a second duration from a second fuel injector.

Description

Attorney Docket No. 10025-342W01PERIPHERAL FUEL INJECTION WITH RATE SHAPING TO IMPROVE EFFICIENCY, EMISSIONS, AND NOISE SIGNATURES IN DIESEL ENGINES CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to and the benefit of U.S. Provisional Patent Application No. 63 / 751,562, filed January 30, 2025, the entirety of which is hereby incorporated by reference.BACKGROUND

[0002] In current fuel injection designs, fuel is injected radially outwards at predetermined start times and injection durations (with respect to the top dead center or TDC) depending upon the engine load. The injected fuel exits from a plurality (typically four to eight) of equally spaced holes around the injector tip, in the form of high-speed liquid jets, and into the space between the stationary cylinder head and moving piston head. The space between the stationary cylinder and the moving piston head contains hot, compressed gas (oxidizer) which is typically air or, in the case of exhaust gas recirculation (EGR), a mixture of air and exhaust products. Liquid fuel expelled from each hole atomizes and evaporates, while ambient gas is entrained into the vaporized fuel to produce a rich fuel-oxidizer mixture. This mixture auto¬ ignites, and combustion proceeds in two steps. First, the fuel-rich mixture burns in premixed mode at some axial distance away from the injector tip. Second, the remaining fuel and / or fuel products find additional oxidizer to burn in non-premixed mode. This existing method of fuel injection produces large amounts of particulate matter (PM), nitric oxides (NOx), carbon monoxide (CO), and unburnt hydrocarbon (UHC) emissions. Presently, engines (e.g., diesel engines) utilize aftertreatment systems to reduce airborne emissions to acceptable levels, but such systems incur efficiency penalties, and increase weight and cost.

[0003] Furthermore, in existing systems, the outward-moving fuel jet is surrounded by a flame that necessarily impinges and spreads on the outer wall of the cylindrical combustion chamber. These unavoidable flame-wall interactions quench combustion reactions and produce high PM, UHC, and CO emissions. In addition, the flame heats the cylinder wall, which requires cooling to maintain its temperature and structural rigidity. The heat from the flame removed by the coolant is an unavoidable parasitic loss in current engines.Attorney Docket No. 10025-342W01Furthermore, at low loads, the liquid fuel jet itself could impinge on the wall and cause wall¬ wetting, which results in excessive PM, UHC, and CO emissions. Second, at low loads, the quantity of injected fuel is decreased by decreasing the fuel supply pressure, Lower fuel velocity at these low pressures restricts the entrainment of the oxidizer into the vaporized fuel. Inadequate access to the oxidizer in turn leads to significantly high PM, UHC, and soot emissions at low loads.

[0004] Therefore, a need exists for more efficient fuel injection systems that reduce emissions.SUMMARY

[0005] One implementation of the present disclosure is a system including an engine head of an engine including a hollow cylinder. The engine head includes a surface configured to be disposed adjacent the hollow cylinder of the engine head. The surface defines a piston cylinder mating area having a center and a mating area periphery radially spaced apart from the center. The mating area periphery is configured to align with a cylinder periphery of the hollow cylinder of the engine disposed adjacent the surface. The engine head further includes a first fuel injector disposed adjacent to the surface, the first fuel injector including a first outlet configured to be disposed adjacent the cylinder periphery of the hollow cylinder. The first outlet is disposed at a first angle greater than 0 degrees with respect to a radial axis extending through the first outlet and the center of the piston cylinder mating area. The first outlet is disposed at a second angle greater than 0 degrees with respect to a plane parallel to the surface of the engine head. The engine head further includes a second fuel injector disposed adjacent to the surface. The second fuel injector includes a second outlet configured to be disposed adjacent the cylinder periphery of the hollow cylinder and circumferentially spaced apart from the first outlet of the first fuel injector. The second outlet is disposed at a first angle greater than 0 degrees with respect to a radial axis extending through the second outlet and the center of the piston cylinder mating area. The second outlet is disposed at a second angle greater than 0 degrees with respect to a plane parallel to the surface of the engine head. The system further includes a controller in electrical communication with each of the first fuel injector and the second fuel injector. The controller includes a processor and a memory, the memory having instructions stored thereon that, when executed by the processor, cause the controller to: operate the first fuel injector to eject a first volume of fuelAttorney Docket No. 10025-342W01from the first outlet at a first time and for a first duration, and operate the second fuel injector to eject a second volume of fuel from the second outlet at a second time that is different from the first time and for a second duration.

[0006] In some implementations, the first angle of the first outlet is equal to the first angle of the second outlet, and the second angle of the first outlet is equal to the second angle of the second outlet.

[0007] In some implementations, the engine head further includes a third fuel injector disposed adjacent to the surface. The third fuel injector includes a third outlet configured to be disposed adjacent the cylinder periphery of the hollow cylinder and circumferentially space apart from each of the first outlet of the first fuel injector and the second outlet of the second fuel injector. The third outlet is disposed at a first angle greater than 0 degrees with respect to a radial axis extending through the third outlet and the center of the piston cylinder mating area. The third outlet is disposed at a second angle greater than 0 degrees with respect to a plane parallel to the surface of the engine head. The controller is further configured to operate the third fuel injector to eject a third volume of fuel from the third outlet at a third time that is different from the first time and the second time and for a third duration.

[0008] In some implementations, the first volume of fuel is equal to the second volume of fuel. In some implementations, the first volume of fuel is different than the second volume of fuel. In some implementations, the first duration is equal to the second duration. In some implementations, the first duration is different than the second duration.

[0009] In some implementations, the first volume of fuel is expelled from the first outlet at a first flow rate and the second volume of fuel is expelled from the second outlet at a second flow rate. In some implementations, the first flow rate is different than the second flow rate. In some implementations, the first flow rate is equal to the second flow rate.

[0010] In some implementations, the first angle of the first and second outlets is in a range of 30 degrees to 50 degrees. In some implementations, the second angle of the first and second outlets is in a range of 5 to 20 degrees.

[0011] In some implementations, the engine head includes 3 to 7 fuel injectors, each fuel injector having outlets arranged circumferentially adjacent the mating area periphery.

[0012] In some implementations, the first fuel injector and the second fuel injector are each coupled to and in fluid communication with a common rail injector.Attorney Docket No. 10025-342W01

[0013] In some implementations, the first angle and the second angle of the first outlet and the second outlet are arranged such that the first volume of fuel ejected from the first outlet of the first fuel injector and the second volume of fuel ejected from the second outlet of the second fuel injector avoid direct physical contact before and during combustion.

[0014] In some implementations, the first angle and the second angle of the first outlet and the second outlet are arranged such that the first volume of fuel ejected from the first outlet of the first fuel injector and the second volume of fuel ejected from the second outlet of the second fuel injector avoid direct physical contact with a sidewall of the hollow cylinder before and during combustion.

[0015] In some implementations, a diameter of the piston cylinder mating area of the engine head is 4 inches to 40 inches. In some implementations, the fuel is diesel fuel.

[0016] In some implementations, an overall fueling rate of the hollow cylinder is at a maximum when a crank angle associated with the hollow cylinder is more than 5 degrees past top dead center.

[0017] In some implementations, an overall heat release rate of the fuel in the hollow cylinder is at a maximum when a crank angle associated with the hollow cylinder is more than 10 degrees past top dead center. In some implementations, a maximum pressure in the hollow cylinder occurs when a crank angle associated with the hollow cylinder is more than 10 degrees past top dead center. In some implementations, a maximum temperature in the hollow cylinder occurs when a crank angle associated with the hollow cylinder is more than 10 degrees past top dead center.

[0018] According to another implementation, a method of fuel injection is disclosed. The method includes providing an engine having a hollow cylinder and an engine head. The engine head includes a surface configured to be disposed adjacent the hollow cylinder of the engine head. The surface defines a piston cylinder mating area having a center and a mating area periphery radially spaced apart from the center. The mating area periphery is configured to align with a cylinder periphery of the hollow cylinder of the engine disposed adjacent the surface. The engine head further includes a first fuel injector disposed adjacent to the surface, the first fuel injector including a first outlet configured to be disposed adjacent the cylinder periphery of the hollow cylinder. The first outlet is disposed at a first angle greater than 0 degrees with respect to a radial axis extending through the first outlet and the center of the piston cylinder mating area. The first outlet is disposed at a second angle greater than 0Attorney Docket No. 10025-342W01degrees with respect to a plane parallel to the surface of the engine head. The engine head further includes a second fuel injector disposed adjacent to the surface, the second fuel injector including a second outlet configured to be disposed adjacent the cylinder periphery of the hollow cylinder and circumferentially spaced apart from the first outlet of the first fuel injector. The second outlet is disposed at a first angle greater than 0 degrees with respect to a radial axis extending through the second outlet and the center of the piston cylinder mating area. The second outlet is disposed at a second angle greater than 0 degrees with respect to a plane parallel to the surface of the engine head. The method further includes providing a controller in electrical communication with each of the first fuel injector and the second fuel injector, the controller including a processor and a memory, the memory having executable instruction stored thereon. The method further includes operating, via the controller, the first fuel injector to eject a first volume of fuel from the first outlet at a first time and for a first duration. The method further includes operating, via the controller, the second fuel injector to eject a second volume of fuel from the second outlet at a second time that is different from the first time and for a second duration.

[0019] In some implementations, the first angle and the second angle of the first outlet and the second outlet are arranged such that the first volume of fuel ejected from the first outlet of the first fuel injector and the second volume of fuel ejected from the second outlet of the second fuel injector avoid direct physical contact before and during combustion.

[0020] In some implementations, the first angle and the second angle of the first and second outlets are arranged such that the first and second volumes of fuel are spaced apart from and avoid direct contact with a sidewall of the hollow cylinder before and during combustion.

[0021] In some implementations, the first volume of fuel is equal to the second volume of fuel. In some implementations, the first volume of fuel is different than the second volume of fuel.

[0022] In some implementations, the first duration is equal to the second duration. In some implementations, the first duration is different than the second duration.

[0023] In some implementations, the first volume of fuel is expelled from the first outlet at a first flow rate and the second volume of fuel is expelled from the second outlet at a second flow rate. In some implementations, the first flow rate is different than the second flow rate. In some implementations, the first flow rate is equal to the second flow rate.Attorney Docket No. 10025-342W01

[0024] In some implementations, the first angle is in a range of 30 degrees to 50 degrees. In some implementations, the second angle is in a range of 5 degrees to 20 degrees.

[0025] This summary is illustrative only and is not intended to be in any way limiting. Other aspects, features, and advantages of the devices or processes described herein will become apparent in the detailed description set forth herein, taken in conjunction with the accompanying figures, wherein like reference numerals refer to like elements.BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIG. 1A shows a cross-sectional diagram of an engine head, according to one implementation.

[0027] FIG. 1B shows a cross-section of FIG. 1A along line B-B, showing a view normal to the piston cylinder mating area.

[0028] FIG. 1C shows a diagram of an engine head further including a controller coupled to each of the fuel injectors, according to one implementation.

[0029] FIG. 2A shows a perspective view model of a modified engine head installed on an experimental engine apparatus, according to one implementation.

[0030] FIG. 2B shows a cross-section of FIG. 2 A along line 2-2.

[0031] FIG. 2C provides a view of the piston cylinder mating area for an engine head having (i) only a centralized fuel injector and (ii) only peripheral fuel injectors, according to one implementation.

[0032] FIG. 3 provides an image of an experimental engine head having a centralized injector, according to one implementation.

[0033] FIG. 4 provides illustrations of injector layouts for conventional diesel and peripheral fuel injector approaches, according to one implementation.

[0034] FIG. 5 shows a series of experimental images of the spray boundary iso-surfaces viewed from the top of the chamber and colored by temperature contours for each of a centrally located six-hole injector and a peripheral fuel injector at a 15 -degree angle and a 37.5-degree angle, according to one implementation.Attorney Docket No. 10025-342W01

[0035] FIG. 6 shows a series of experimental images of the flame boundary iso-surfaces viewed from the top of the chamber and colored by OH mass fraction contours for each of a centrally located six-hole injector and a peripheral fuel injector at a 15-degree angle and a 37.5-degree angle, according to one implementation.

[0036] FIG. 7 presents an isometric view of heat flux contours at the periphery, top, and bottom walls of the combustion chamber at 2.5 ms aSOI for conventional diesel combustion, peripheral fuel injection at 15 degrees (PeFI-15), and peripheral fuel injection at 37.5 degrees (PeFl-37.5), according to one implementation.

[0037] FIGS. 8A-8C show a cold flow experimental setup for an experimental test chamber, according to one implementation.

[0038] FIGS. 9 A shows a diagram of a high-pressure fuel cart piping and instrumentation for injecting fuel into the test chamber, according to one implementation.

[0039] FIG. 9B shows a diagram of an injector circuit and current, according to one implementation.

[0040] FIG. 10A shows a graph of raw light intensity vs radius in the test chamber, along with the correction factor, according to one implementation.

[0041] FIG. 10B shows a graph of the boundary detection of a jet, according to one implementation.

[0042] FIG. 10C shows a graph of local jet width vs distance to the tip, according to one implementation.

[0043] FIG. 11 shows a table of injection visualization cases for each of a central injector and three differently angled peripheral injectors from 0.5ms after injection to 2.0ms after injection, according to one implementation.

[0044] FIG. 12A shows a graph of the rate of fuel injection for a multi-hole injector (solid line) vs a single-hole injector (dashed line), according to one implementation.

[0045] FIG. 12B shows a graph of cumulative fuel volume injected for a multi-hole injector (solid line) vs a single-hole injector (dashed line), according to one implementation.

[0046] FIG. 13A shows a plot of the axial distance of a fuel jet from a single-hole peripheral injector over time, according to one implementation.Attorney Docket No. 10025-342W01

[0047] FIG. 13B shows a plot of the axial distance of a fuel jet from a multi-hole centralized injector over time, according to one implementation.

[0048] FIG. 13C provides a plot comparing the difference between the two plots of FIGS.8 A and 8B.

[0049] FIG. 14A shows a graph of efficiency vs rail pressure at the start of injection (SOI) operating point of highest efficiency for both conventional diesel combustion (CDC) and peripheral fuel injection (PeFI) configurations, according to one experimental implementation.

[0050] FIG. 14B shows a graph of heat loss through exhaust vs rail pressure at the start of injection (SOI) operating point of highest efficiency for both conventional diesel combustion (CDC) and peripheral fuel injection (PeFI) configurations, according to one experimental implementation.

[0051] FIG. 15A shows a graph of smoke (filtered smoke number) vs rail pressure (bar) at the start of injection (SOI) operation point of highest efficiency for both conventional diesel combustion (CDC) and peripheral fuel injection (PeFI) configurations, according to one experimental implementation.

[0052] FIG. 15B shows a graph of carbon monoxide (CO in g / kW-hr) vs rail pressure (bar) at the start of injection (SOI) operation point of highest efficiency for both conventional diesel combustion (CDC) and peripheral fuel injection (PeFI) configurations, according to one experimental implementation.

[0053] FIG. 16A shows a graph of cylinder pressure, apparent heat release rate (aHRR), 5, 10, 50, 90% mass of burnt fuel (MBF), and injection current profile (no actual scale) vs crank angle at -18 degrees after top dead center (aTDC) and 800 bar rail pressure for CDC injection configurations, according to one experimental implementation.

[0054] FIG. 16B shows a graph of cylinder pressure, aHRR, 5, 10, 50, 90% MBF, and injection current profile (no actual scale) vs crank angle at -18 degrees aTDC and 800 bar rail pressure for peripheral fuel injection (PeFI) configurations, according to one experimental implementation.

[0055] FIG. 17 shows a graph illustrating Load vs Number of Injectors for CDC and PeFI (6) through PeFI (2) configurations, according to an experimental implementation.Attorney Docket No. 10025-342W01

[0056] FIG. 18A and 18B illustrate experimental results including fuel mass flow rate for short and long fuel injection operations for a peripheral fuel injector system, according to various implementations.

[0057] FIGS. 19A-19D illustrate experimental results comparing a single-cylinder engine for conventional (CDC), standard PeFI, and PeFI with rate shaping method, according to various implementations. Results include fueling rate (A), heat release rate (B), cylinder pressure (C), and gas temperature (D) during the combustion event at an identical engine load and engine speed.

[0058] FIG. 20 illustrates soot absorptance and NOx emissions for experimental single¬ cylinder engine tests wherein PeFI and rate shaping simultaneously reduce soot and NOx emissions compared to the CDC case, according to various implementations.

[0059] FIG. 21 shows a schematic overview of an experimental engine test cell, according to an experimental implementation.

[0060] FIG. 22 shows a graph with a comparison of bulk cylinder pressure among CDC, PeFI-Sim, and PeFI-RS, according to an experimental implementation.

[0061] FIGS. 23A-23C show graphs with a comparison of estimated injection rate, heat release rate, and mass fraction burned among CDC, PeFI-Sim, and PeFI-RS, according to an experimental implementation.

[0062] FIG. 24 shows a graph with a comparison of the soot and NOx emissions among CDC, PeFI-Sim, and PeFI-RS, according to an experimental implementation.

[0063] FIG. 25 shows a graph depicting NOx-CO trade-off among CDC, PeFI-Sim, and PeFI-RS, according to an experimental implementation.

[0064] Various objects, aspects, features, and advantages of the disclosure will become more apparent and better understood by referring to the detailed description taken in conjunction with the accompanying drawings, in which like reference characters identify corresponding elements throughout. In the drawings, like reference numbers generally indicate identical, functionally similar, and / or structurally similar elements.Attorney Docket No. 10025-342W01DETAILED DESCRIPTION

[0065] Additional advantages will be set forth in part in the description that follows or may be learned by practice. The advantages will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive, as claimed.

[0066] The present disclosure relates to fuel injection methodology in internal combustion engines using multiple fuel injectors. The systems, methods, and devices of this disclosure increase the ability to control fuel injection timing and location(s) by utilizing multiple, single-hole fuel injectors located on the periphery of the cylinder head. In some examples, each fuel injector may be controlled electronically and independently through a common-rail system. All injectors are placed strategically around the periphery of the cylinder head. In some implementations, the disclosure applies to four- and two-stroke diesel engines of different physical dimensions used, for example, in marine, train, and trucking industries. In some implementations, the disclosure focuses particularly on the engine architecture with a reciprocating piston inside a cylinder and covered on the top by a cylinder head or engine head. In some implementations, the cylinder head houses air intake and exhaust ports, as well as an electronically controlled fuel injector(s).

[0067] The systems, methods, and devices of this disclosure increase the ability to control fuel injection timing and location(s) by utilizing multiple, single-hole fuel injectors located on the periphery of the cylinder head. Existing internal combustion engines can be retrofitted with this methodology using a redesigned cylinder head and fuel injection controller. For example, in some implementations, the systems, methods, and devices of this disclosure may be used in existing diesel engines. Similarly, new engines (e.g., diesel engines) may directly incorporate redesigned cylinder heads and fuel injection controllers. Thus, no other structural or design changes to the engine hardware are required to implement these designs. The systems, methods, and devices of this disclosure are entirely fuel agnostic such that they may be implemented into an internal combustion engine of any type with a variety of fuel types.

[0068] The injector placement may be described by two geometric parameters: (1) injector orientation angle is the angle between the injector hole axis and horizontal axis (normal to the direction of piston motion or parallel to the cylinder head), and (2) injector layout angle is the angle between the injector hole axis and combustion chamber radius (i.e., the angle of theAttorney Docket No. 10025-342W01injector downwards from the surface of the engine head). The injector orientation angle is chosen to ensure that each jet and associated flame is independent and that jets or flames do not interact with each other at any time. The injector layout angle is chosen to ensure that each jet / flame is sufficiently away from the outer wall, and again, no jet / flame interactions take place at any time.

[0069] In one example of a six-hole injector, each of the six, single-hole injectors is disposed on the periphery of the cylinder head (e.g., adjacent to the periphery or arranged along the periphery of the cylinder head). In this example, the injector placement requirements can be fulfilled by utilizing an injection orientation angle of greater than 10 degrees and an injector layout angle between 30 and 50 degrees. In other implementations, each of the peripheral fuel injectors includes more than one hole (e.g., 2, 3, or 4 holes).

[0070] This disclosure further includes a method to eliminate flame-wall and / or jet- wall interactions and prevent flame quenching. The systems, methods, and devices of this disclosure avoid wall-wetting scenarios that are normally associated with the existing centrally mounted multi-hole injectors - the same centrally mounted injectors that are responsible for excessive PM, UHC, and CO emissions in internal combustion engines (e.g., diesel engines). Additionally, heat loss to the coolant is reduced compared to existing systems since the flame makes no contact with the cylinder wall. This otherwise lost energy to the coolant is retained within the system to perform useful work, and increase indicated / break power output or thermal efficiency of the engine.

[0071] In some implementations, for a given fuel supply pressure, the single-hole injector provides a faster initial ramp-up rate of fuel compared to the currently employed multi-hole injector. The faster fuel ramp-up rate increases oxidizer entrainment into the vaporized fuel. Thus, leaner fuel-oxidizer mixtures are formed to reduce soot precursors in premixed combustion, and thus, less PM emissions are formed in the non-premixed combustion process. Geometrically, the periphery of the cylindrical chamber contains exponentially more oxidizer compared to that available near the center. Thus, the peripheral injection site of the present disclosure inherently increases access to the oxidizer and forms leaner fuel-oxidizer mixtures which reduce PM emissions. Additionally, implementing peripheral, single-hole fuel injectors - rather than the relatively larger, centralized, multi-hole injector - reduces the mounting space requirements for the system, reducing the overall system cost. The term “circumferential” is defined as the periphery of any shaped hollow prism (e.g., a hollow cylinder, rectangular prism, hexagonal prism, etc.).Attorney Docket No. 10025-342W01

[0072] Some implementations of the engine heads described herein have the ability to selectively turn off one or more fuel injectors to match the load. For example, half of the injectors can be turned off at half the load, and only one injector can be active when the engine is idling. This method eliminates the need to decrease the fuel supply pressure to reduce the fuel flow rate (or load), as in current systems. Thus, in some implementations, each active injector operates at the maximum fuel supply pressure and produces jet / flame and combustion processes similar to those at the full load. In this way, part-load or even idle operations do not increase emissions of PM, NOx, CO, and UHC as is the case with known fuel injection systems. Instead, the injector systems disclosed herein reduce emissions proportionally to the load or the number of active injectors.

[0073] Further disclosed are systems and methods for increasing compression ratio and providing higher fuel efficiency in diesel engines without increasing peak chamber pressure (PCP) and incurring high-pressure rise rate (PRR) or high engine-out nitric oxides (NOx) emissions. For example, some implementations of the present disclosure provide the ability to independently control each injector for fuel delivery. For example, in various implementations, each injector can have a hole of a different diameter, each injector can be turned on at a different time, the injection duration for each injector can be different, or some combination thereof. Varying one or more of these aspects provides a wide array of permutations and possibilities to modulate the fuel supply and fuel-oxidizer mixing in the combustion chamber to reduce emissions and improve engine performance.

[0074] In one aspect, injectors are turned on at different times in a sequential manner, for example, in a counterclockwise arrangement with reference to the direction of fuel injection. The injector timings can be adjusted to constrain the heat release rate or the pressure rise rate within prescribed limits. This method of fuel injection dramatically decreases the maximum pressure rise rate in the cylinder, which relates directly to noise and vibrations in internal combustion engines (e.g., diesel engines). The sequential fuel injection strategy of the present disclosure results in quieter engines.

[0075] In one example, current diesel engines operate far from the ideal diesel cycle that may benefit from a constant pressure heat addition process. In known fuel injection systems, the average operating pressure is far below the maximum pressure inside the chamber, dictated by the pressure rise rate during combustion. However, in one example, a sequential fuel injection strategy in some implementations disclosed herein can be modulated further to minimize (or eliminate) the pressure rise rate during the heat addition process and thus,Attorney Docket No. 10025-342W01approach an ideal diesel cycle. Such a cycle will provide high fuel efficiency when operated at the maximum pressure during heat addition, achieved by high compression ratios, by turbocharging, or both.

[0076] In another aspect, the sequential fuel injection strategy of this disclosure can include multiple injection events from each injector. For example, a fraction of the fuel can be injected during the compression stroke, and the rest is supplied near the top dead center (TDC) to ignite the fuel-oxidizer mixture charge and subsequently, to control the combustion process. This fuel injection strategy decreases the fuel fraction burnt in non-premixed combustion mode, which will decrease NOx emissions formed in the high-temperature region of such reactions.

[0077] In some implementations, fuel injection from multiple peripheral fuel injectors includes offset timing of fuel injection volumes. For example, a first volume of fuel may be dispensed or expelled from a first outlet of a first peripheral fuel injector at a first flow rate and / or for a first duration. Then, a second volume of fuel may be dispensed or expelled from a second outlet of a second peripheral fuel injector at a second flow rate and / or for a second duration. Thus, a sequential fuel injection strategy may include multiple fuel injection events having different fuel flow rates and / or durations of fuel injection. A controller (e.g., having instructions stored on a memory thereof that are executable via a processor) coupled to the one or more fuel injectors may be used to implement the sequential fuel injection and / or variable injection durations.

[0078] In some implementations, the sequential fuel injection disclosed herein provides control of combustion during the heat addition process, i.e., it allows control of “heat release rate shaping.” Existing diesel engines may vary combustion timing before and after TDC but are constrained by the PCP limit dictated by the structural design of the engine. This approach leads to several undesirable consequences: (a) PCP is attained by compression combined with combustion and hence, the PCP limits the maximum achievable compression ratio with a negative impact on the thermal efficiency, (b) the PRR must be limited to an acceptable value to avoid excessive noise and disastrous engine failure modes, and (c) high peak temperatures are produced early in the combustion process, which increases the residence time of gas at high temperatures to increase the NOx formation. By contrast, the disclosed methods herein achieve heat release rate shaping to attain one or more of the following additional benefits of PeFI injection: (a) reduction in NOx emissions by reducing gas temperatures and / or residence time of high-temperature reaction zones, (b)Attorney Docket No. 10025-342W01reduction / elimination of combustion noise and vibrations by decreasing PRR during the heat addition process to nearly zero, and (c) raising thermal efficiency by allowing engine operation at higher compression ratios for a given PCP. In some implementations, operating at a lower PCP reduces the structural and hardware requirements of the engine, reducing costs. In some implementations, heat addition takes place at nearly a constant pressure, primarily after the TDC, such that the PRR is negligible. In some implementations, the HRR increases after the TDC, which reduces the average cylinder gas temperatures and decreases residence time for high gas temperatures to curtail the engine-out NOx emissions.

[0079] In some implementations, the fuel injection approach of the present disclosure introduces a swirl in the ambient flow that is known to increase turbulence, improve access to the oxidizer, and produce shorter flames with lower emissions. In some implementations, the fuel injection approach of the present disclosure can be utilized without or with exhaust gas recirculation (EGR) if necessary to further reduce NOx emissions. In some implementations, the fuel injection approach of the present disclosure will reduce PM, NOx, CO, and UHC emissions at all loads, and thus, dramatically reduce the need for after-treatment systems and associated initial and operating costs.

[0080] Various additional aspects of this disclosure may be understood by the figures and their corresponding descriptions. Referring generally to the figures, an engine head comprising at least one fuel injector disposed around the periphery of the piston cylinder is shown, according to various implementations.Example Device #1

[0081] FIG. 1A shows a cross-sectional diagram of an engine head 100, according to one implementation. The engine head 100 of this example may be used in a variety of internal combustion engines (e.g., a diesel engine) with a variety of sizes or uses (e.g., a diesel engine powering a truck, or a marine engine powering a ship). The engine head 100 includes a surface 102 and at least one fuel injector including a first fuel injector 110 and a second fuel injector 112. The engine head 100 has a surface 102 (e.g., a bottom surface that may be coupled to an engine). The surface 102 defines a piston cylinder mating area 104 having a center 106 and a periphery 108 radially spaced from the center 106. FIG. 1B shows a cross-section of FIG. 1A along line B-B, showing a view normal to the piston cylinder mating area 104. The piston cylinder mating area 104 has a diameter of anyw'here from 4 inches to 40 inches. However, in other implementations, the piston cylinder mating area has a diameterAttorney Docket No. 10025-342W01smaller or larger than that range (e.g., 1, 2, or 3 inches in diameter, or 45, 50, 55, 60, 65, or 70 inches in diameter).

[0082] A hollow cylinder 120 of the engine is disposed adjacent to the surface 102 of the engine head 100. The hollow cylinder 120 has a sidewall extending around an inner volume. As shown in FIG. 1 A, the hollow cylinder 120 has a first side 122 and a second side 124 where each side is a portion of the same sidewall. The hollow cylinder 120 also includes a periphery 126. The periphery 108 of the engine head 100 is configured to align with the periphery 126 of the hollow cylinder 120.

[0083] A piston head 130 is shown inside the hollow cylinder 120. The hollow cylinder 120 may be, for example, the piston cylinder of an engine block, and the engine head 100 may be installed on top of the engine block.

[0084] The engine head 100 includes a first fuel injector 110 having an outlet 114 defined at one longitudinal end of the first fuel injector 110 (e.g., a bottom end). The second fuel injector 112 similarly has an outlet 116. Each of the outlet 114 and the outlet 116 are defined at the surface 102. In some implementations, each outlet may comprise a nozzle extending out from the surface of the engine head.

[0085] The outlets 114, 116 of the fuel injectors 110, 112 are disposed adjacent to the periphery 108 of the piston cylinder mating area 104. Additionally, the outlets 114, 116 of the fuel injectors 110, 112 are disposed adjacent to the periphery 126 of the hollow cylinder 120. The outlet 114 of the first fuel injector 110 is disposed adjacent to the first side 122 of the hollow cylinder 120, and the outlet 116 of the second fuel injector 112 is disposed adjacent to the second side 124 of the hollow cylinder 120. Thus, the outlet 114 of the first fuel injector 110 is circumferentially spaced apart from the outlet 116 of the second fuel injector 112.

[0086] Each outlet 114, 116 is disposed at one or more angles with respect to the engine head 100. For example, the outlet 114 of the first fuel injector 110 is disposed at a first angle (e.g., angle “9” in FIG. IB; or the “injector orientation angle”) being greater than 0 degrees with respect to a radial axis 105 extending through the outlet 114 and the center 106 of the piston cylinder mating area 104. The first angle “0” in FIG. IB is 40 degrees. However, in other implementations, the first angle is in a range of 30 degrees to 50 degrees.

[0087] Furthermore, the outlet 114 of the first fuel injector 110 is disposed at a second angle (e.g., angle “a” in FIG. 1A; or the injector layout angle) being greater than 0 degrees with respect to a plane parallel to the surface 102 of the engine head 100. The second angleAttorney Docket No. 10025-342W01“a” in FIG. 1A is 10 degrees. However, in other implementations, the second angle is in a range of 5 degrees to 20 degrees.

[0088] While FIGS. 1A and 1B depict two fuel injectors 110, 112, in other implementations, the engine head may have a greater number of fuel injectors. For example, an engine head may include 3, 4, 5, 6, 7, or more fuel injectors each having outlets arranged circumferentially around the periphery of the piston cylinder mating area. For example, in some implementations, the engine head includes a third fuel injector having an outlet disposed adjacent (or along) the periphery of the piston cylinder mating area, and the outlet of the third fuel injector is circumferentially spaced apart from each of the outlet of the first fuel injector and the outlet of the second fuel injector.

[0089] In use, each of the fuel injectors 110, 112 eject a volume of fuel into the inner volume defined by the hollow cylinder 120. For example, in a diesel engine, each of the fuel injectors 110, 112 would eject the volume of diesel fuel for use in a combustion operation which would force the piston head 130 away from the surface 102. While references are made to diesel fuel and diesel engines in connection with the example of FIG. 1A, the systems, methods, and devices of this disclosure are entirely fuel agnostic. In other words, a variety of fuel types and engine types may implement the systems, methods, and devices of this disclosure - not just diesel engines. Therefore, in other implementations, the fuel injectors of the engine head 100 use a different type of fuel and are implemented in a different type of internal combustion engine.

[0090] As shown in FIG. 1A, the first fuel injector 110 ejects a first volume of fuel 140, and the second fuel injector 112 ejects a second volume of fuel 142 (shown in FIG. 1B). In some implementations, the first volume of fuel 140 is the same as the second volume of fuel 142. In other implementations, the first volume of fuel 140 is different than the second volume of fuel 142. In some implementations, the first fuel injector 110 and the second fuel injector 112 are each coupled to and in fluid communication with a common rail injector.

[0091] The first and second angles are arranged such that the first volume of fuel 140 ejected from the outlet 114 of the first fuel injector 110 is spaced apart from, or avoids direct physical contact with, the second volume of fuel 142 ejected from the outlet 116 of the second fuel injector 112 before and during combustion. Furthermore, the first and second angles are arranged such that each of the first volume of fuel 140 ejected from the outlet 114 of the first fuel injector 110 and the second volume of fuel 142 ejected from the outlet 116 ofAttorney Docket No. 10025-342W01the second fuel injector 112 are spaced apart from, or avoid direct physical contact with, the sidewall of the hollow cylinder 120 before and during combustion. The resulting flames of each of the first and second volumes of fuel 140, 142 are also spaced apart from each other and from the side wall of the hollow cylinder 120.

[0092] The particular arrangement of the first and second angles of the outlets 114, 116 of each fuel injector 110, 112 ensures efficient and complete combustion of the fuel within the hollow cylinder 120. By avoiding fluidic interactions with each other and / or the sidewall of the hollow cylinder 120 each of the first and second volumes of fuel 140, 142 can combust quickly and completely, reducing unwanted byproducts. Additionally, the energy of combustion is directed more efficiently to pushing the piston head 130 (e.g., by avoiding heat loss to the sidewall).

[0093] In some implementations, the engine head 100 further includes a controller 150 coupled to each of the first fuel injector 110 and second fuel injector 112, as shown in FIG.1C. The engine head 100 of FIG. 1C also includes images of the fuel injectors 110, 112 for clarity. The controller 150 is configured to operate each of the first fuel injector 110 and the second fuel injector 112 to perform a fuel dispensing operation. During a fuel dispensing operation, the controller operates (e.g., activates a solenoid of the fuel injector) the first fuel injector 110 to eject a first volume of fuel 140 from the outlet 114 and / or the second fuel injector 112 to eject a second volume of fuel 142 from the outlet 116.

[0094] The controller 150 includes a memory 152 coupled to a processor 154. The processor 154 is configured to carry out the instruction from the memory 152. The memory 152 of the controller 150 may include one or more pre-configured sets of instructions for operating the one or more fuel injectors. For example, a set of instructions may activate the first fuel dispensing operation from the first fuel injector 110 at a first time and the second fuel dispensing operation from the second fuel injector 112 at a second time. In some implementations, the first time and the second time are the same. In other implementations, the first time and the second time are different.

[0095] In one example, the controller 150 operates only one of the fuel injectors (e.g., first fuel injector 110) for an amount of time. Operation of only one fuel injection may be used during an idle stage of the engine when the full power of combustion from a plurality of injected volumes of fuel is not necessary. Thus, the engine can remain idle while saving fuel and emitting fewer byproducts.Attorney Docket No. 10025-342W01

[0096] In another example, the controller 150 operates the fuel injectors in order around the periphery of the piston cylinder mating area 104. For example, the controller 150 may activate a first fuel dispensing operation of the first fuel injector 110, and then a second fuel dispensing operation of the second fuel injector 112. In some implementations, the controller 150 operates six different fuel injectors to individually perform a fuel dispensing operation at a different time such that each fuel injector is operated in order around the periphery of the piston cylinder mating area.

[0097] The timing of the fuel dispensing operations may be adjusted and customized as needed for a particular use case. Additionally, the volume of fuel dispensed may be adjusted for each fuel injector between each combustion operation, depending on the particular use case.

[0098] In another example, the controller 150 operates the fuel injectors to dispense fuel in a sequential manner (e.g., an offset dispensing pattern). For example, the controller 150 may operate the first fuel injector 110 to dispense a first volume of fuel from a first outlet of the first fuel injector 110 at a first time. The first volume of fuel may be dispensed at a first flow rate and / or for a first duration. Then, the controller 150 may operate the second fuel injector 112 to dispense a second volume of fuel from a second outlet of the second fuel injector 112 at a second time. The second volume of fuel may be dispensed at a second flow rate and / or for a second duration. The first and second volumes of fuel may be different or equal to each other depending on the application. The first and second times may be different or equal to each other depending on the application. The first and second flow rates may be different or equal to each other depending on the application. The first and second durations may be different or equal to each other depending on the application.

[0099] The controller 150 operating the fuel injectors in a sequential manner - or other patterns - may dispense the first volume of fuel at a first time for a first duration and the second volume of fuel at a second time that is later than the first time and for a second duration. In contrast to existing systems that dispense a single volume of fuel (or a single flow rate of fuel for a given operating pressure), implementations of the systems and methods disclosed herein can vary or slowly increase the volume of fuel dispensed into the cylinder. This pattern of fuel addition prevents high-pressure spikes and prevents high heat release rates that occur with simultaneous full-volume fuel dispensing operations from multiple fuel injector holes.Attorney Docket No. 10025-342W01Example Device #2

[0100] FIG. 2 A shows a perspective view model of a modified engine head 200 installed on an experimental engine apparatus, according to one implementation. The engine head 200 is similar to the engine head 100 of FIGS. 1A-1C such that like reference numbers denote like elements. However, the engine head 200 includes six peripheral fuel injectors. The peripheral fuel injectors each have an outlet circumferentially spaced around the piston cylinder mating area 104. A centralized fuel injector is shown in FIG. 2A-2C but is not included in the engine head 200. The centralized fuel injector is shown in FIG. 2A-2C as a point of comparison between the two systems (i.e., peripheral vs. centralized fuel injection). FIG. 2B shows a cross-section of FIG. 2A along line 2-2.

[0101] FIG. 2A shows each of the fuel injectors including a first fuel injector 202, second fuel injector 204, third fuel injector 206, fourth fuel injector 208, fifth fuel injector 210, and sixth fuel injector 212. Each of the fuel injectors 202-212 is disposed in the engine head 200. A hollow cylinder 120 is disposed underneath the engine head 200 with a piston head 130 therein. Additionally, the piston head 130 includes a piston shaft 232 coupled to the piston head 130 and a crankshaft 234 coupled to and being driven by the movement of the piston shaft 232.

[0102] FIG. 2B depicts a set of representative fuel volumes 140 dispensed from the outlets of the centralized fuel injectors 220. As shown, each fuel volume is ejected at a 10.5-degree angle with respect to the piston cylinder mating area 104.

[0103] FIG. 2C provides a view of the piston cylinder mating area 104 for an engine head 200 having (i) only a centralized fuel injector and (ii) only peripheral fuel injectors. FIG. 2C also provides diagrams corresponding to each fuel injector setup.Experimental Testing and Results #1 – Variable Injection Timing and Rate Shaping

[0104] A study was conducted to investigate variable fuel injection timing, injection duration, fuel flow rate, and injected fuel volume using a peripheral fuel injection system (e.g., using the modified engine head 100 of FIGS. 1A-1C or the modified engine head 200 of FIGS. 2A-2C). FIGS. 18A-18B illustrate two methods investigated to determine fuel injection timings to achieve a prescribed heat release rate shape. FIG. 18A illustrates one or more short injections, and FIG. 18B illustrates one or more longer injections of fuel from the peripheral fuel injectors (e.g., in a sequential pattern). The fueling rate of the fuel injector as a function of fuel supply pressure and fuel injection duration is measured in a rate of injectionAttorney Docket No. 10025-342W01(ROI) test rig. ROI test rig was developed for the study that provided precise measurements of fuel ROI during initial ramp-up, quasi-steady state, and ramp-down periods, and thus, for the total injection duration.

[0105] Next, a total fueling rate profile is prescribed to achieve the desired heat release rate shape. FIGS. 18A and 18B display the target fueling rate by the black dotted curve. In these examples, heat addition occurs at a constant pressure and thus, the fueling rate increases linearly with time as the piston moves downward to extract work. The start time of fuel injection can be shifted to an earlier time (or crank angle) than the TDC to account for a finite ignition delay time measured experimentally and to ensure that the combustion begins at TDC.

[0106] In the example of FIG. 18A, about 67.5 mg of fuel is injected at a linearly increasing rate in the total injection duration of about 3.5 ms. This example represents short injections for a relatively small engine load. These short injections will produce either fuel¬ rich or fuel-lean premixed flames. The equivalence ratio in these flames will depend upon the oxidizer entrainment in the near field, and with proper design, it might be possible to achieve lean premixed (LPM) combustion to virtually eliminate soot, NOx, CO, and UHC emissions. In some implementations, a rich premixed (RPM) combustion operation occurs, but at a lower fuel-rich equivalence ratio compared to that in conventional diesel combustion, which dramatically reduces soot emissions compared to existing systems.

[0107] In the example of FIG. 18B, about 96 mg of fuel is injected again at a linearly increasing rate in the total injection duration of about 4.0 ms. This example represents longer fuel injections for a modest engine load. These longer injections represent the typical diesel combustion behavior, i.e., RPM flame in the near field followed by a downstream mixing-controlled diffusion flame. This approach may be implemented at higher fueling rates (or higher engine loads) to ensure access to the oxidizer away from the near-field of the injector.

[0108] The start of injection and injection duration for each injector may be determined by an optimization algorithm that uses ROI data for each injector to achieve the prescribed fueling rate with minimal discrepancy. The optimization algorithm may be implemented on a controller of the system that is in communication with the fuel injectors and other portions of the engine head. For example, the controller may receive data from sensors coupled to different portions of the engine (e.g., the cylinder, an exhaust valve, or a drive train). In otherAttorney Docket No. 10025-342W01implementations, the optimization algorithm may be implemented within another controller or system that is in communication with the controller that is coupled to the fuel injectors.

[0109] FIGS. 18A-18B graphically illustrate the results for each injector shown in a different color. Tables 1A-1B summarize quantitative results in terms of the start of injection and injection duration for each injector. These results are shown for time prescribed in terms of milliseconds (ms) as well as crank angle duration for an engine operating at 1400 rotations per minute (RPM). Note that these examples illustrate a multitude of options available to sequence the fuel injection process depending on the heat release rate shape, engine load, and other operating parameters.Curve Start Time Com. Start Time Com. Mass (mg)(ms) Duration (CAD) Duration(ms) (CAD)Curve 1 1.88 0.50 15.02 4.00 11.05 Curve 2 1.84 0.50 14.75 4.00 11.05 Curve 3 0.02 0.50 0.12 4.00 11.05 Curve 4 0.24 0.50 1.95 4.00 11.05 Curve 5 1.93 0.50 15.42 4.00 11.05 Curve 6 1.61 0.72 12.85 5.73 12.42 Total Black Curve Mass 67.36Total Combined Curve Mass 67.67 Table 1A: Fuel injection timings for short injection caseCurve Start Time Com. Start Time Com. Mass (mg)(ms) Duration (CAD) Duration(ms) (CAD)Curve 1 -0.03 2.50 -0.24 20.00 27.46 Curve 2 0.52 2.00 4.20 16.00 23.36 Curve 3 1.13 1.50 9.01 12.00 19.26 Curve 4 1.78 1.00 14.26 8.00 15.15 Curve 5 2.43 0.50 19.45 4.00 11.05 Total Black Curve Mass 95.98Total Combined Curve Mass 96.28 Table 1B: Fuel injection timings for longer injection caseDemonstration in a Single-Cylinder Engine

[0110] The fuel injection scheme of this study was implemented in an operational singlecylinder engine (SCE) to acquire test data. FIGS. 19A-19D present test results from a SCE operated in different modes: conventional diesel combustion (CDC), standard PeFI, and twoAttorney Docket No. 10025-342W01examples of PeFI with rate shaping denoted as PeFI-Rate Shaping and PeFI-Rate Shaping +; during heat addition process, the overall increase in pressure for PeFI-Rate Shaping + is slightly greater than that for PeFI Rate Shaping. The engine was operated with an intake boost pressure of 1.70 bar, compression ratio of 14.2, a load of 4.9 bar gross indicated mean effective pressure (IMEP,g), and PCP of 80 bar. The PCP limit of 80 bar imposed in these early-stage prototype tests is far below the PCP limit of up to 200 bar in modern diesel engines. Thus, test conditions represent the low-end operation of commercial diesel engines. However, the results presented here are intended to illustrate the trends that are expected to remain the same in more realistic diesel engine operating conditions.

[0111] FIG. 19A shows plots of fueling rate vs. crank angle for the four test cases. The fueling rate for CDC and standard PeFI overlap each other with a slight phase shift between the two resulting from the shorter ignition delay time for the latter. However, the PeFI with rate shaping profiles shows a stepwise increase in the fueling rate and minor differences between the two cases.

[0112] FIG. 19B shows that the HRR profiles for CDC and standard PeFI are different from those for PeFI with rate shaping. In the first two cases, heat addition starts before TDC and continues to about 20° aTDC. In cases of PeFI with rate shaping, heat addition starts near the TDC and continues till about 25° aTDC. The HRR correlates well with the ramping up of the fueling rate (FIG. 19A) during the heat addition process. Note that the shift towards late combustion is enabled by the precisely and incrementally controlled fuel injection process with sequential PeFI injections as presented in this disclosure.

[0113] FIG. 19C shows that in cases of CDC and standard PeFI, combustion starts at about -10° before TDC (bTDC), which rapidly increases cylinder pressure from about 43 bar at -10° bTDC to nearly 80 bar at 5° aTDC. The maximum PRR during this process is about 3.80 bar / deg. The maximum PRR and PCP are nearly the same for CDC and standard PeFI operations because in both cases, the fueling rate is essentially the same, i.e., a given amount of fuel is injected at the same time / rate either by a single multi-hole injector for CDC or simultaneously by multiple single-hole injectors for standard PeFI. Note that these test cases are chosen to illustrate nearly identical cylinder pressure profiles for CDC and standard PeFI, not the best efficiency of each configuration.

[0114] FIG. 19C shows very different pressure profiles for PeFI with rate-shaping cases. In these cases, combustion starts just slightly before TDC, and pressure remains constant orAttorney Docket No. 10025-342W01increases only slightly during the heat addition process. Specifically, for PeFI with rate shaping, the pressure remains constant at 50 bar until about 5° aTDC and then increases to PCP of about 57 bar. The maximum PRR during heat addition is only 1.26 bar / deg which occurs during the compression stroke rather than during the heat addition process, and it is less than 1 / 3rd of that for the CDC case. The maximum PRR for CDC and standard PeFI cases will increase at higher loads, and thus, associated benefits of reduced combustion noise and vibrations will be increasingly greater for PeFI with the rate-shaping concept disclosed herein.

[0115] In FIG. 19C, the PCP of 57 bar for PeFI with rate shaping is far less than the PCP of 80 bar for CDC and standard PeFI cases. In the case of PeFI with rate shaping plus, the pressure increases slightly during the heat addition process to reach PCP of about 60 bar, with maximum PRR still occurring during compression rather than combustion. Note that the ability to sequentially inject fuel from multiple injectors has made it possible to realize the pressure profiles with rate shaping in FIG. 19C, which cannot be achieved with CDC or standard PeFI approaches. Overall, FIG. 19C supports some of the benefits of PeFI with rate shaping including, but not limited to: (a) negligible PRR during combustion which will reduce combustion noise and vibration, and (b) lower PCP for a given load, which will allow significantly higher compression ratios to further increase the thermal efficiency.

[0116] FIG. 19D shows the average gas temperature calculated using cylinder pressure measurements. The average gas temperature increases for two reasons: (a) indirectly by gas compression, i.e., an increase in gas temperature by heat addition during the compression stroke increases the gas pressure, which further increases the gas temperature, and (b) directly by heat addition in combustion. Both these phenomena are present in CDC and standard PeFI approaches. However, PeFI with rate shaping eliminates temperature rise associated with gas compression since heat addition takes place at nearly a constant pressure. Note that the peak average gas temperature for PeFI with rate shaping is at least 100 K less than that for CDC and standard PeFI cases. These lower average gas temperatures will reduce NOx emissions formed in the high-temperature flame zones. A second benefit of PeFI with rate shaping is evident in FIG. 19D. The peak temperatures occur later during the heat addition process. Thus, the residence time for NOx formation is reduced to further curtail engine-out NOx emissions. Lower gas temperatures for PeFI with rate shaping will further reduce heat loss to the coolant to augment heat loss benefits already realized by maintaining flames away from the cylinder periphery in the standard PeFI approach.Attorney Docket No. 10025-342W01

[0117] FIG. 20 shows a plot of absorbance versus NOx emissions for the four test cases, whereby absorbance on the y-axis is proportional to the soot concentration. Soot emissions for standard PeFI and PeFI with rate shaping approaches are several times less than those for the CDC case. These results demonstrate that the PeFI approach disrupts the soot-NOx trade¬ off observed typically in CDC engines. FIG. 20 shows that the standard PeFI yields NOx emissions greater than those for the CDC case. However, PeFI with rate shaping simultaneously reduced soot emissions by an order of magnitude and NOx emissions by a factor of three compared to those for the CDC case. PeFI with rate shaping plus slightly increased soot and NOx emissions compared to PeFI with rate shaping, but both these emissions are still lower by multiple times compared to those for the CDC case. These results demonstrate that simultaneous reductions in soot and NOx emissions are achieved by transitioning from the CDC case to PeFI with rate shaping.

[0118] Next, experimental data were analyzed to determine the thermal efficiency for the four test cases. In this case, the thermal efficiency for CDC and standard PeFI is 35.6% and 35.3%, respectively, or within measurement uncertainty. As elsewhere described, reduced heat loss with standard PeFI would increase the thermal efficiency, but it requires optimization of injection timings not pursued in these tests. However, this study showed that, for essentially identical cylinder pressure traces, standard PeFI reduces soot emission by¬ multiple factors compared to those for CDC case, without affecting thermal efficiency and with only a minor increase in NOx emissions. PeFI with rate shaping, however, decreased the thermal efficiency to 33.7% which is 2 percentage points less than that for CDC. However, PeFI with rate shaping plus increased the efficiency to 34.9% or only 1% less than that for the CDC case. The thermal efficiency for PeFI with rate shaping was reduced because the engine was operating at a PCP of < 60 bar compared to that of 80 bar for CDC.

[0119] In summary, the example case of PeFI with rate shaping yields significantly lower soot and NOx emissions, with only a minor reduction in thermal efficiency compared to those for the CDC case. These demonstrated reductions in soot and NOx emissions and similar thermal efficiency for PeFI with rate shaping are a significant benefit over existing CDC systems. Note that these benefits are achieved in addition to the expected reductions in combustion noise and vibrations because of the negligible PRR in the case of PeFI with rate shaping.

[0120] As noted previously, the PCP for PeFI with rate shaping is < 60 bar compared to the PCP of 80 bar for CDC and standard PeFI cases. In a diesel engine, thermal efficiencyAttorney Docket No. 10025-342W01depends upon the compression ratio, which in turn is dictated by the PCP depending upon the structural hardware design of the engine. In the above illustrations, PeFI with rate shaping achieves similar efficiency and lower emissions at very lower PCP compared to those for the CDC case. This feature of PeFI with rate shaping offers the opportunity to increase the compression ratio without raising the PCP above the structural limit. Increasing the compression ratio requires modifications to the engine hardware. This study analytically extrapolated experimental results for PeFI with rate shaping to higher compression ratios. The thermodynamic cycle analysis revealed that the thermal efficiency would increase by 3 percentage points if the compression ratio was increased to 17.0 and by 6 percentage points by increasing the compression ratio to 20.0; in both cases, the PCP remains within 80 bar. These results demonstrate that PeFI with rate shaping can provide significant improvements in thermal efficiency, although these benefits must be counter-balanced with expected increases in soot and NOx emissions.

[0121] Experimental test campaigns in SCE have so far been limited to relatively low PCPs (about 80 bar) and low loads (about 5 bar IMEP,g). This study focused on proof of concept at these relatively low ranges of test conditions. However, these concepts may be implemented at more realistic engine condition by integrating a robust cylinder head design to increase the PCP.

[0122] Overall, PeFI with rate shaping disrupts the typical soot-NOx tradeoff found in CDC engines and instead shifts it to a tradeoff between thermal efficiency and NOx emissions because the soot emissions are always low. This unique feature of PeFI with rate shaping can be exploited to significantly increase the thermal efficiency of diesel engines at the expense of NOx emissions that can be reduced to acceptable levels by the typical after- treatment system for NOx reduction.Experimental Testing and Results #2 - Computational Fluid Dynamics (CFD)

[0123] FIG. 3 provides an image of an experimental engine head having a centralized injector. Such an experimental setup mimics the fuel dispensing operation of - and provides a proof-of-concept for - the centralized fuel injector 220 of FIGS. 2A-2C. Additionally, the engine head of FIG. 3 formed the basis for further experiments to expand upon the advantages of peripherally dispersed fuel injectors and the angles of their outlets.

[0124] Additionally, a computational fluid dynamics (CFD) study was conducted using models of conventional internal combustion engines (e.g., conventional diesel combustion)Attorney Docket No. 10025-342W01and peripheral fuel injection engines. Once the CFD model was validated, it was applied to compare the combustion behavior and thermodynamic performance of the conventional diesel combustion (CDC) and peripheral fuel injection (PeFI) strategies. A centrally located six-hole injector is used for CDC and correspondingly, six single-hole injectors are used for PeFI. In both cases, fuel jets were oriented downwards at a constant angle of a = 10.5° from the top boundary of the chamber. For PeFI, simulations were performed for different layout angles with respect to the radius the chamber, i.e., 0 = 0, 15, 22.5, 30, and 37.5 degrees. In both CDC and PeFI cases, the six fuel jets were identical to each other, and thus, the domain was reduced to one-sixth of the cylindrical chamber to reduce the computational effort by imposing periodic conditions at the circumferential boundaries.Comparison of Centralized Fuel Injectors to Peripheral Fuel Injectors

[0125] FIG. 4 represents the pie-slice-shaped computational domain for CDC on the left side and PeFI on the right side (e.g., representative of one of the fuel injectors of the engine head 100 of FIG. 1A). The injector orientation angle is the angle between the top boundary wall and injector hole axis (e.g., angle a from the piston cylinder mating area 104). The injector layout angle (e.g., angle 0 from the radial axis) is zero degrees for the illustration on the right.

[0126] The two domains are identical to each other except for the fuel injection location at the inlet boundary. All faces of the domain were set to wall boundary conditions except for the sides of the pie slice designated as periodic boundaries. The injectors were modeled using nozzle locations defined at the appropriate position and layout angle for the specific condition in the 3D space. For CDC, the protrusions of peripheral injectors are replaced by a flat face, and the opposite is true for PeFI, as shown in FIG. 4 marked by “Injector Cup.” The effect of this adjustment on mass / volume within the chamber was determined to be negligible.

[0127] CFD results were analyzed to determine the jet boundary representing the outer most surface where air entrainment is negligible. The jet boundary could be determined using different thresholds including density, equivalence ratio, or temperature. Tills study relied on local mixture composition based on nitrogen (N2) mass fraction in a local cell. A threshold of 99% or less of the ambient N2 mass fraction was used based on the sensiti vity analysis yielding minimum numerical errors.

[0128] FIG. 5 shows the isometric view of the jet from the top of the chamber at 1.0, 1.5, and 2.0 ms after the start of injection (aSOI). The jet boundary was determined using the N₂Attorney Docket No. 10025-342W01thresholding method, and the iso-surfaces are colored by the temperature in the cell. Note that the highest temperature at the jet boundary (about 1800 K) is much less than the expected flame temperature in the reaction zone. The contour map is clipped to 1500K to highlight differences along most of the jet boundary. The first row in Fig. 5 represents the CDC case, and two PeFI cases of 9 = 15 and 37.5 (PeFI-15 and PeFI-37.5) are shown, respectively, in the second and third rows. PeFI-15 represents the jet behavior at small layout angles (0, 15, and 22.5 degrees) while that for the high layout angles (30 and 37.5 degrees) is represented by PeFI-37.5

[0129] At 1.0 ms after the start of injection (aSOI), conventional diesel combustion (CDC) shows cooler, vaporized fuel jet in the near-field, high-temperature combustion products in the downstream region, and a well-established high-temperature jet head moving towards the outer wall of the chamber. This trend continues until about 1.5 ms aSOI, when the jet head nears direct contact with the outer wall. Thereafter, the jet head impinges on the wall, and the jet boundary takes on a nearly conical shape. Jet impingement has multiple negative effects: (a) contact between high-temperature products and low-temperature wall increases the heat loss to the wall, (2) reduced gas temperatures quench reactions in the adjacent diffusion flame zone, and (3) the fuel remaining in the jet is unable to access additional oxidizer for combustion. The overall outcome is reduced heat release rate (HRR), and high soot and UHC emissions.

[0130] Jet evolution for peripheral fuel injection at 37.5 degrees (PEFI-37.5) is shown in the third row of FIG. 5. In this case, jets are injected towards the outer radius of the chamber where a larger quantity of air mass is available as compared to that towards the center of the chamber. At 1.0 ms aSOI, each jet appears nearly independent, and its features are similar to those of the CDC case. Jets interact at 1.5 ms aSOI, but in this case, the incident jet minimally glances over the adjacent jet closer to the injector exit. These jet interactions amplify at 2.0 ms aSOI but indicate an absence of direct flame interactions, or competition for combustion air. Jet head interaction in the near field of the adjacent jet would dilute and preheat the reactants which could potentially benefit combustion and soot emissions. Overall, these results show that PeFI-37.5 outperforms all cases, in terms of producing independent jets with minimum interference to utilize air at larger radii of the combustor. Layout angles greater than 0 - 37.5 degrees are viable but were not explored in this study. Additionally, the jet inclination angle with respect to the top wall (a) was the same for each iteration of thisAttorney Docket No. 10025-342W01study. However, in other implementations, the inclination angle of the jets (e.g., adjacent jets) may be varied to further reduce jet interactions.

[0131] FIG. 6 shows isometric views of the flame boundary from the top of the chamber for all cases and times in the corresponding FIG. 5. The flame boundary is defined as the diffusion flame zone at an equivalence ratio of 1.0 and contours are colored by the OH mass fraction to highlight reaction zone. Geometric features of the flame boundary are similar to those of the jet boundary, but the former is slightly narrower and shorter as expected. For CDC, the first row in FIG. 6 shows the typical features of a reacting jet, but without peak OH mass fraction in the jet head at 1.5 ms aSOI. At 2.0 ms aSOI, the flame front with a high OH mass fraction is approaching the chamber wall. At 2.0 ms aSOI, the flame spreads out on the chamber wall, and quenching is evident by the reduction in the OH mass fraction in the flame region adjacent to the wall.

[0132] The flame structure for PeFl-15 matches that of CDC at 1.0 ms aSOI, but the OH mass fraction for the former case is much smaller in the mid-region, indicating a weaker flame. Interestingly at 1.5 ms aSOI, the local jet collisions and momentum exchange have caused the incident diffusion flame to wrinkle and fold into complex shapes, much different from the classic jet head. The OH mass fraction is low in the mid-region of the receiving jet indicating that the incident jet head is more effective in accessing air to produce the intense wrinkled flame with a high OH mass fraction. This behavior is exemplified at 2.0 ms aSOI by the alternating zones of high and low OH mass fraction originating, respectively, in the incident and receiving jets to produce the donut-shaped toroidal vortex. Again, PeFI-0 and PeFI-22.5 revealed similar features in varying degrees.

[0133] Increasing the layout angle of PeFI to 0 = 37.5 degrees produced significantly different flame behavior as shown in the third row of FIG. 6. In this case, the flame structure at 1.0 ms aSOI is similar to that of the CDC case. However, at 1.5 ms aSOI, the flame front in the jet head interacts with the receiving jet near the LOL as the injection event is ending. Indeed, dilution and preheating of reactants by the incident jet could reduce the equivalence ratio and increase the temperature at LOL in the receiving jet. These in turn will reduce the soot formation and increase the soot oxidation in the downstream non-premixed flame, although as discussed earlier, further investigation is necessary to quantify and optimize these effects. Interestingly, upstream jet interactions do not create competition for combustion air at later times. At 2.0 ms aSOI, each flame appears independent and robust with the highest overall OH mass fraction of cases.Attorney Docket No. 10025-342W01

[0134] Overall, PeFI-37.5 has no jet-wall interactions and minimal or potentially beneficial jet-to-jet interactions, and it produces independent, robust jet flames with sufficient access to combustion air at the outer radii of the chamber. Jet interactions are highly dependent on the layout angle and operating conditions. For example, parameters such as fuel injection pressure, injection duration, hole size, orientation angle (a), etc. would all play an important role in fuel-air mixing in the chamber and deserve further exploration to fully take advantage of the PeFI concept.

[0135] FIG. 7 presents an isometric view of heat flux contours at the periphery, top, and bottom walls of the combustion chamber at 2.5 ms aSOI for conventional diesel combustion (panel (a)), PeFI-15 (panel (b)), and PeFI-37.5 (panel (c)). The jet boundaries, defined by the N₂ threshold, were colored in white. The heat transfer model used in this simulation had a constant wall boundary temperature of 461 K with a law of the wall model and roughness constant of 0.5, all chosen based on prior studies. The heat transfer model provides a reasonable approach to estimate wall heat loss for relative comparison between CDC and PeFI concepts, although further improvements would be desirable in future studies. For CDC, bright red contours indicate high heat flux regions in FIG. 7 associated with jet / flame impingement. PeFI cases avoid this heat loss but introduce hot spots at the top and bottom walls of the chamber. The hot spots decrease noticeably with an increase in the injection inclination angle from 0 = 15 to 37.5 degrees.

[0136] For the PeFI-15 case, the hot spots coincide with the reaction zone in the middle of the chamber as localized hot products tend to move towards the top and bottom walls. The hot spots are more severe on the top wall since it is closer to the toroidal reaction zone compared to the bottom wall. For PeFI-30, each jet has a nearly independent reaction zone, and flame confinement is much less severe because combustion occurs in a larger volume, close to the chamber periphery. In practice, the reduced heat loss of PeFI cases will decrease the wall temperatures. However, the present simulations are performed using the same wall temperature for CDC and PeFI cases, and hence, they represent a conservative estimate for PeFI cases.

[0137] Next, computational results were analyzed to compute the total heat transfer from the outer, top, and bottom walls of the chamber versus time for CDC and each PeFI configuration. For CDC, the heat transfer to the outer wall increases linearly until about 1.5 ms aSOI. During this time, heat transfer is associated with the temperature difference between the ambient gas and the chamber wall. At / after 1.5 ms aSOI, the contact between theAttorney Docket No. 10025-342W01jet / flame interacts, and the wall increases the temperature difference and thus, the heat transfer. This sudden increase in heat transfer is absent in all PeFI cases, indicating that the high-temperature flame zones are sufficiently far away from the outer wall even for the largest layout angle of 0 = 37.5 degrees with flames closest to the outer wall. In this way, the PeFI concept is agnostic to the combustion process inside the chamber and approaches adiabatic combustion since the outer wall remains in contact only with the high-temperature ambient air during the entire test.

[0138] Considering all calculated heat transfer situations and all walls of the chamber, CDC had the worst performance with 53% greater heat transfer compared to the best performing PeFI-37.5 case. PeFI cases performed better as the layout angle increased, i.e., PeFI-0 performed the worst while PeFI-37.5 performed the best. The net heat transfer to the chamber walls for the CDC case was 14.4 J or 9.5% of the total heat released by the fuel. In comparison, the best-performing PeFI case had a net heat transfer of 6.8 J or 4.5% of the total heat released by the fuel, representing a reduction of 5 percentage points. Although the present simulations do not consider the moving boundaries of an actual engine, the results presented so far suggest that the PeFI approach offers a significant opportunity to reduce the heat loss and cooling needs of the engine.Experimental Setup

[0139] A test chamber and fuel injection hardware system were developed for this study (e.g., see the prototypical setup of FIG. 3). The objectives of this study included a demonstration of the PeFI concept via experiments in a cold flow facility replicating ambient densities relevant to diesel engines. Particularly, one goal of this study was to investigate (a) the effects of the layout angle (0) on the overall flow field and jet-to-jet interactions in the chamber, and (b) the jet behavior in the nearfield of the injectors to quantify the differences in air entrainment between CDC and PeFI concepts.

[0140] In this study, flow visualization experiments at ambient densities relevant to diesel engines were conducted in a non-reacting, cold flow chamber. Cold flow experiments offer insight into the flow field, especially in the near field, without the complex setup needed for hot fire, reacting, and engine experiments.

[0141] FIGS. 8A-8C show the cold flow experimental setup with an optical chamber made from Lexan with an inside diameter (ID) of 120.7 mm and a depth of 33.3 mm. The fuel injectors mounted horizontally are to the left side of the chamber with optical access on theAttorney Docket No. 10025-342W01right side in FIG. 8A. The optical window for image acquisition is parallel to the injector wall and has a diameter of 114.3 mm. 'The lighting system uses LED strips (R6060-IP20-CW) placed around the circumference of the chamber outer wall as shown in FIG. 8B. The test chamber can operate either with a standard six-hole injector mounted at the center (CDC) or with six different single-hole injectors located around the periphery (PeFI). FIG. 8C shows the Lexan disk on the view window with an example spray pattern.

[0142] FIG. 9A shows a schematic of the high-pressure fuel cart designed to inject fuel into the test chamber. Fuel is pressurized up to a limit of 1800 bar by a Bosch CP3 pump driven by a 15 HP electric motor connected via a drive shaft and bell housing assembly. The motor is controlled by a variable frequency drive set to 2.0 Hz. The inlet metering valve (IMV) on the CP3 pump was controlled in a closed loop using an embedded microcontroller system (Beaglebone Black). A plate heat exchanger using chilled water from the building was added to the fuel circuit to operate the fuel cart for an indefinite amount of time at diesel-relevant conditions. Without cooling, the low frequency of injection events in the test chamber (twice per minute) and partial fuel flow-based cooling of the CP3 pump would cause heating and vaporization in the fuel lines, thereby, presenting a safety hazard. Fuel temperatures at the inlet of the IMV and return line on the injector were monitored using K-type thermocouples. Fuel temperature in the return line is analogous to the temperature of the fuel injected into the test chamber as it leaves the injector nozzle. The fuel rail pressure was monitored using a pressure sensor from the original equipment manufacturer. In all cases, a total of seven fuel injectors (CDC and PeFI) were pressurized to maintain a consistent setup between central and peripheral injection experiments.

[0143] The injection event was controlled precisely by a custom-designed circuit board that can independently and simultaneously operate multiple injectors. A simplified schematic of this circuit board, which was replicated seven times (one for CDC and six for PeFI), is presented in FIG. 9B. The circuit was controlled using an in-house developed control code and an NI cRIO chassis. The low-level logic inputs represented by Vjnwere amplified using gate driver hardware to actuate the fast-switching MOSFET (QI). A snubber circuit (C2 and R2) was used to attenuate the oscillations found while actuating the circuit that would otherwise lead to hardware failure. A bank of four capacitors (Cl) was used to provide sufficient instantaneous power to the circuit. The injector was allowed to free-wheel to appropriately dissipate the current using diode (DI) when the MOSFET (QI) was turned off. The current across the injector was measured by the Hall Effect sensor and related to theAttorney Docket No. 10025-342W01output voltage signal (Vout) which was monitored at 1 Mhz speed by the control algorithm and cRIO. MOSFET duty cycle was modulated to control the injector current according to the prescribed limits using a peak and hold methodology with two hold stages. The bottom right of FIG. 9B shows an experimentally acquired injector current signal during operation. A fast-blow fuse (Fl) and metal oxide varistor (R3) were installed to protect the circuit from over-current and over-voltage faults, respectively.

[0144] Test Procedure - Nitrogen pressurizes the chamber using fill and purge ports, each actuated using a solenoid valve. A pressure transducer and a K-type thermocouple measure, respectively, pressure and temperature in the chamber. Lab VIEW software monitors the relevant temperature and pressure data from the fuel cart. National Instruments cRIO chassis using NI 9401, 9212, 9201, 9482, and 9223 data acquisition modules control the complete operation of the experiment.

[0145] The nitrogen density in the chamber, controlled automatically to the set value for each repeated injection, is calculated from pressure and temperature readings. Experiments were performed with the diesel surrogate n-heptane supplied at 1500 bar for a commanded injection duration of 1.0 ms. The fuel supply temperature is controlled via a chilled water heat exchanger, as described previously, to a value of 337 K. Experiments were conducted for four different injection configurations: central injection (CDC) and PeFI with layout angles of 0 = 0, 15, and 30 degrees. For each test condition, 30 separate injections were performed to acquire high-speed video images, processed as discussed in the following section.

[0146] Data Processing - The overall injection process involving the spray as well as the region composed of fuel vapor and entrained ambient air is referred to as the “jet”. Acquired images were analyzed to determine jet tip penetration length, jet tip velocity, jet width, and total jet volume. Jet tip penetration length is the axial distance from the injector exit to the tip of the jet. Jet tip velocity is calculated as the time derivative of the jet penetration length. Jet width is the sum of radii on the left and right sides of the jet axis. Total jet volume is the sum of volumes calculated by the radii and pixel width of discrete jet segments in the axial direction. For each test condition, post-processing software extracts hue, saturation, and intensity data from the TIFF image. Next, the intensity of the first frame is subtracted from the current frame to remove the injector nozzle and other background structures. Finally, the image was binarized as discussed next.Attorney Docket No. 10025-342W01

[0147] In the present study, the differences in lighting between central and peripheral configurations introduced inconsistencies that required a correction procedure before quantitative image analysis. The test chamber is illuminated by multiple LEDs around the cylindrical window and as such light intensity is independent of the circumference but presents as a function of radius, reducing towards the center. FIG. 10A plots the radial profile of light intensity as a quadratic fit (solid black line) obtained by averaging background intensities in the circumferential direction at each radii using 50 background images acquired at 20 kHz and exposure time of 50 ps; sensitivity analysis at different exposure times led to similar results. The background intensity was normalized by the inverse of the quadratic fit, represented by the dashed green line in FIG. 10A to effectively produce intensity with a uniform radial distribution.

[0148] Image post-processing seeks to distinguish the jet from the background. In this study, the method relies on the mean intensity of the jet as it changes with time rather than the lowest luminosity distinguished from the background. Despite correcting the background intensity as discussed above, the threshold for the method still changed with time. Upper and lower bounds of threshold values were used to compare CDC and PeFI configurations. First, the standard method was used, after correcting for radial intensity variation, to determine the highest and lowest threshold values for all cases. 'Then, the image analysis was repeated for constant ‘low’ and constant ‘high’ threshold values to obtain the jet’s lower and upper bounds. The threshold value had minimum effect on jet tip penetration length and jet tip velocity, but it changed jet width and total jet volume even though the overall trends were similar for all cases.

[0149] FIG. 10B shows the binarized jet in green with its boundaries highlighted in red. let tip penetration length is determined by finding the farthest point from the injector body along the centerline. Local jet width is obtained by adding left and right radii (RL. I and RR, I) at a given axial location. FIG. 10C shows the local radii on the left and right sides of the jet and illustrates that the jet at this given instant is reasonably symmetric. Total jet volume occupation is determined from the radius on each half of the jet centerline where the jet width is reported. Assuming that each 2D image is a projection of the 3D jet, the areas of half circles on each side of the jet are summed at all axial locations to compute the total jet volume using Eq. 1.V = ^^dx + (1)Attorney Docket No. 10025-342W01Results and Discussion

[0150] Non-reacting experiments at fuel supply pressure of 1500 bar were performed to match the ambient density of well-studied ECN spray A condition at p = 23.0 kg / m3 and an additional dataset at p = 18.5 kg / m3. The study will focus first on the jet development and then, on fuel-air mixing at times relative to autoignition expected at reacting conditions. Flow visualizations with CDC and PeFI will be compared at different layout angles. The CDC case includes a six-hole injector supplying fuel radially outwards from the center to the wall of the chamber. PeFI uses six one-hole injectors supplying fuel inwards from the periphery of the chamber at layout angles of 0, 15, and 30 degrees. The analysis will focus on jet parameters in the near field to quantify jet development for different injector configurations. Observed trends will be explained by the ROT profiles for single and multi-hole injectors.

[0151] FIG. 11 shows visual images of the jets acquired by the high-speed video camera at three different times after the start of injection (aSOI), t = 0.5, 1.0, and 2.0 ms for all four cases. Here, time, t = 0.0 ms refers to the image frame just before the visual observation of the jet. The first row shows that at t = 0.5 ms, when autoignition is expected for a Spray A injector in a reacting environment, the central jets have penetrated about half-way radially into the chamber. All six jets show similar behavior although minor variations are often present. At t = 1.0 ms, the central jets have arrived near the chamber wall. In a reacting case, the flame is expected to have impinged on the wall by this time. At low loads, the liquid fuel jet itself could impinge on the wall to cause incomplete combustion and associated emissions. Finally, at t = 2.0 ms, the central jets have impinged and spread on the wall. In a reacting case, these flame-wall interactions would quench reactions and produce unwanted soot, UHC, and CO emissions. Additionally, heat loss to the cylinder wall will increase dramatically. Overall, these images provide a reference to compare with different PeFI cases presented next.

[0152] The second row in FIG. 11 shows jet images for PeFI with a layout angle of 0 degrees, i.e., PeFI-0 or purely radial inward injection. At t = 0.5 ms, all jets have penetrated more than halfway radially inwards, in contrast to the central injection which had a shorter penetration at this time. At t = 1.0 ms, the jets collided to form a cloud in the center of the chamber. At t = 2.0 ms, the fuel cloud at the center has homogenized and expanded radially as fuel injection continues. The flow structures in these images show that PeFI-0 case eliminates jet-wall interactions, but it introduces jet-to-jet interactions which can be equally problematic. In this case, jet interactions have resulted in fuel accumulation at the center ofAttorney Docket No. 10025-342W01the chamber where air is inherently in short supply. In a reacting case, this situation would cause incomplete combustion and a large amount of soot formation. Unfortunately, PeFI-0 case is unable to access the majority of the air mass available at the outer radii of the chamber.

[0153] The third row in FIG. 11 shows visual images of the jet for PeFI-15 case. At t = 0.5 ms, jets penetrate similarly to the PeFI-0 case as expected prior to jet interactions. At t = 1.0 ms, PeFI-15 case shows jet collisions that form a hexagonal shape structure away from the center of the chamber. At t = 2.0 ms, jets have interacted with each other’s 'ake to create a donut-shaped toroidal flow structure near the mid-radius of the chamber. In a reacting case, adjacent flames would compete for the oxidizer, i.e., PeFI-15 case would not produce flames without interruption.

[0154] The fourth row in FIG. 11 shows visual images of the spray for PeFI-30 case. Here, jets are closer to the outer wall, and they do not interact to form a toroidal structure at t = 1.0 ms. A careful observation will show that even at t = 2.0 ms, jets pass each other witli minimum interference. Note that each jet is moving away from the top wall (recall the orientation angle of 10.5°), and this movement is greater at the jet head than at the jet exit. Thus, the distance (normal to the paper) increases between jets at the location where the two jets would have met otherwise, and minimum interactions take place. For a majority of the time, jets remain in the outer radii of the chamber where most of the combustion air is present. In a reacting environment, the PeFI-30 case would encounter minimal flame interactions. Instead, the jet head from one jet would be close in proximity to the lift-off length (LOL) of the adjacent jet.

[0155] Flow visualization experiments demonstrate that the electronics system developed in this study can simultaneously and precisely control multiple jets. The experimental facility with chamber dimensions and ambient density matching with those of a typical diesel engine offers confidence in the PeFI concept for practical applications. PeFI eliminates completely the flame-wall interactions that increase heat loss to the cylinder wall and liquid wall wetting, potentially occurring at low loads. However, these benefits are realized only for layout angles of 30-degrees or greater when utilizing six peripheral injectors. Layout angles greater than 30-degrees would position the incident jet head closer to the exit of the neighboring jet, but vertically away from it, and eliminate completely the flame -to-flame interactions and competition for combustion air in a reacting case. Hypothetically, at large layout angles, the proximity of the incident jet head to the exit of the adjacent jet offers the potential forAttorney Docket No. 10025-342W01localized EGR-like behavior in a reacting environment. Note that the layout angle should be sufficiently less than its maximum value of 60-degrees, in the case of six injectors, to prevent jets from impinging on the outer wall and reintroducing the problem of jet-wall interactions.

[0156] Rate of Injection - FIGS. 12A and 12B show the instantaneous and cumulative ROI profiles for an injection pressure of 1500 bar. The injector is mounted at the entrance of a long tube filled with the injectant fluid, and the pressure wave near the injector exit is measured by a pressure transducer. The measured pressure profile is proportional to the mass flow rate at the injector exit. FIG. 12A shows that the ramp-up rate of the multi-hole injector is quite different from that of the single-hole injector. Constant and similar ROI at steady conditions is reached at about 0.2 ms. FIG. 12B shows that the cumulative fuel injection of the single-hole injector exceeds that of the multi-hole injector for a majority of the injection duration.

[0157] Jet Width and Total Jet Volume - Air entrainment after injection determines the radial spread of the jet. Jet cone angle can quantify this behavior, but spatial and temporal variations during injection make direct comparisons between configurations difficult. Thus, jet width as a function of both time (t) and jet Up penetration distance (z) was computed using 180 data sets representing six jets and thirty injections. FIGS. 13A and 13B show contour plots of jet width for the best performing PeFI-30 case and central case. In these contour plots, the black line traces the maximum jet width computed, but similar results were obtained with the high threshold.

[0158] FIGS. 13A-13B show that the jet width at a given time (i.e., along the vertical axis) increases with increasing tip penetration until reaching the maximum, and then, the jet width decreases as the jet converges towards the tip. FIGS. 13A-13B show greater jet tip penetration for PeFI-30 case compared to that for the CDC case. In addition, PeFI-30 jet is wider than the central case throughout, indicating more entrainment for PeFI-30 case. As discussed previously, higher air entrainment reduces soot formation in premixed combustion.

[0159] The contour plot in FIG. 13C plots the difference in jet width for the two configurations. Here, the white shade signifies no difference in measured jet width for both cases for majority of the tip penetration distance. The difference arises near the jet tip region where PeFI-30 case entrains more air to produce a wider jet. At these locations, PeFI-30 case can be as much as 4.0 mm wider than the central case, representing a 50% increase in jet width. These results show that the faster ramp-up rate of PeFI accompanies increased airAttorney Docket No. 10025-342W01entrainment near the jet tip. FIG. 13C shows that the increase in the jet width (or air entrainment) is greater at the downstream locations.Experimental Testing and Results #3 - Physical Model

[0160] A single-cylinder, four-stroke, naturally aspirated research engine, Caterpillar 3401, with a large cylinder bore was selected for this research. The basic specifications of the engine are listed in Table 2. A customized cylinder head featuring one centrally located injection port, six peripherally located injection ports, and one pressure transducer port was designed, manufactured, and integrated with the engine. Intake and exhaust valve layouts were modified slightly to avoid interference with the injectors. Proper positioning of the injectors on the periphery of the cylinder, while placing the rocker arm shaft at a location to match the original kinematics and timing of the valve train, required raising the rocker arm shaft 38.1 mm (1.50 in) above its original height. FIG. 3 shows the engine head assembly, showing the heightened rocker arm shaft, central injector, and peripheral injector locations. Aluminum side panels were used to enclose the oil-bathed valve train compartment with a Lexan lid for inspecting the motion and confirming thorough lubrication of the components.Feature DimensionBore 137.16 mm (5.4 in)Stroke 165.10 mm (6.5 in)Connecting Rod Length 261.62 mm (10.3 in)Compression Ratio 16.1:1, Naturally AspiratedTable 2: Caterpillar 3401 original specifications.

[0161] The custom engine head of FIG. 3 was designed to allow for seven injector ports, one located coaxially with the cylinder centerline and six equally spaced around the periphery of the cylinder. Bosch CRIN3 diesel injectors with either six or one 150 pm hole(s) arranged at an included (total) conical angle of 159 degrees were used for testing. The central injector has a six-hole configuration, whereas the periphery injectors have a single hole; five of the six holes on the injector were plugged for PeFL The peripheral jets had a layout angle of 30 degrees.

[0162] Experiments were conducted to compare the efficiency and emissions performance of CDC and PeFI schemes. Fuel rail pressure was varied from 400 bar to 1200 bar in steps of 200 bar. The start of injection (SOI) timing was varied from -22° to -14° after top dead center (al'DC) in intervals of 2° for each fuel rail pressure. The advancement limit of SOI wasAttorney Docket No. 10025-342W01chosen to limit the cylinder pressure rise rate (PRR) to 1000 kPa per crank angle degree (CAD). For SOI timings earlier than -22° a'l'DC, PRR could rise to potentially detrimental levels because of the rapid HRR imparting high impulse loads on the cylinder head and piston; the low boost pressure of nominally 1.3 bar was a limiting factor of the SOI advance. Injection beyond -14° aTDC was avoided because of poor efficiency with late combustion. For all tests, the engine speed was constant at 1400 rpm and the engine load was constant at nominally 5.0 bar IMEPn. The small compression ratio in this study resulted in a relatively small IMEPn although it is deemed appropriate to make direct comparison between the two injection schemes. At each operating point, 30 seconds of data were acquired after steady conditions were reached to perform time-averaged analysis.

[0163] Fuel efficiency affected by coolant and exhaust heat losses is one of the primary indicators of an engine’s performance. FIG. 14A compares the highest efficiency values of CDC and PeFI schemes across the entire SOI span for all fuel rail pressures. Measurement uncertainties including the systematic and instrumentation bias errors are represented by the error bars in FIG. 14A. Results show that the CDC scheme has an efficiency of 41.2% at the lowest rail pressure of 400 bar, increasing to 42.7% at 800 bar, and then decreasing to 41.4%’ at 1200 bar. In contrast, the efficiency for PeFI scheme is nearly independent of the fuel rail pressure at 43.0% and is greater than that of the CDC efficiency at all fuel rail pressures. Detailed data not shown here indicated that the SOI variation had a smaller effect on efficiency for PeFI scheme compared to that for CDC scheme, even at the lowest rail pressure of 400 bar. 'These encouraging results are consistent with the numerical simulations showing that the inward-moving PeFI jets / flames reduce heat loss to the coolant compared to the outward-moving jets / flames of the CDC scheme. Thus, a greater percentage of the thermal energy is retained within the cylinder to generate power.

[0164] FIG. 14B shows coolant and exhaust heat loss as a percentage of the fuel energy input for all rail pressures at SOI operating points of the highest efficiency. The engine also experiences oil cooler heat loss and convective / radiant heat losses from various hot surfaces and coolant hoses between the engine head and reservoir return manifold. However, these losses are expected to be comparable for both schemes and thus, are not included specifically in FIG. 14B.

[0165] FIG. 14B reveals that the CDC scheme has a noticeably greater coolant heat transfer (about 13.3% of energy input) in comparison to the PeFI scheme (about 11.3% of energy input). FIG. 14B also shows that the injection scheme has a negligible effect on the exhaustAttorney Docket No. 10025-342W01heat loss, which is expected because the exhaust valve timing is the same for both cases. In summary, the higher fuel efficiency of PeFI scheme compared to that of the CDC scheme can be attributed to the lower coolant heat loss for the former case.

[0166] FIG. 15 A includes a graph of engine smoke, and FIG. 15B shows a graph of carbon monoxide (CO), for both PeFI and CDC for all rail pressures at SOI operating points providing the highest efficiency. FIG. 15A shows that PeFI results in filtered smoke number (FSN) of about 0.2 at the low rail pressures of 400 bar and 600 bar, but at higher rail pressures, the FSN is nearly zero, i.e., the smoke cannot be detected. FIG. 15A shows that FSN for CDC varies from a low of 0.8 at the mid-level rail pressure of 800 bar to a high of 1.7 at the lowest rail pressure of 400 bar. Evidently, smoke levels for CDC are up to an order of magnitude higher compared to those for PeFI. For the CDC scheme, however, the smoke levels increase when the rail pressure increases beyond 800 bar. At these high rail pressures, higher velocity fuel jets / flames tend to approach and impinge on the piston wall, which causes flame quenching inhibiting soot oxidation and thus, higher engine-out smoke emissions. This phenomenon is completely absent in the PeFI scheme.

[0167] FIG. 15B shows CO levels of both PeFI and CDC for all rail pressures at SOI operating points of the highest efficiency. Results show that CO levels for PeFI are, on average, half of those for CDC.

[0168] FIGS. 16 A and 16B display the injector current (without magnitude scale), cylinder pressure (in MPa) at motoring and fired conditions, and apparent heat release rate (aHRR in J / CAD) profiles versus crank angle for both CDC and PeFI. The motoring curve in FIGS. 16A and 16B shows a peak cylinder pressure of only about 3.60 MPa because of the relatively low compression ratio of the present research engine compared to most modern commercial diesel engines. At firing conditions, FIG. 16B shows a peak cylinder pressure (PCP) of 6.31 MPa for PeFI which is 6% greater than the PCP of 5.95 MPa for CDC in FIG.16A. For PeFI, the PCP is reached at 7 degrees a'l'DC which is slightly ahead of the PCP location of 8.5 degrees for CDC. Higher PCP for PeFI can be related to the faster apparent heat release rate (aHRR) and higher heat retention in the cylinder volume.

[0169] The apparent heat release rate (aHRR) curve for CDC in FIG. 16A shows commanded SOI at -18 degrees after top dead center (aTDC), and a brief ignition delay from -18 degrees aTDC to -10 degrees aTDC followed by a rapid increase in aHRR denoting ignition. The aHRR curve for PeFI in FIG. 16B is similar to FIG. 16A but displays subtleAttorney Docket No. 10025-342W01differences. In comparison to CDC, the ignition delay of PeFI is shorter by 1.3 degrees, the aHRR during the premixed combustion is steeper, fuel injection stops earlier by about 3 degrees, the peak aHRR of 160 J / CAD is 20% greater, and the peak aHRR occurs slightly earlier than that of CDC. For both CDC and PeFI, about 10% of the fuel is burnt at the time of peak aHRR.

[0170] These results provide unique insight into PeFI operation. First, the shorter fuel injection duration demonstrates, for the first time in an operational engine, a faster ROI of single-hole injectors for PeFI in comparison to the multi-hole injector for CDC. Second, the shorter ignition delay time for PeFI in comparison to CDC demonstrates, experimentally, the faster fuel-air mixing with single-hole injectors. Third, the steeper aHRR for PeFI compared to that for CDC is caused likely by the faster kinetics of the fuel-air mixture formed upstream, although higher gas temperatures inside the cylinder (recall reduced heat loss) could also contribute to this effect. Finally, the higher peak aHRR for PeFI compared to that for CDC can be attributed to the higher cylinder gas temperature since the burnt fuel at this peak location is about the same, i.e., 10% MBF. After peak aHRR location, combustion proceeds in diffusion mode, and unlike CDC, no distinct secondary peak is observed for PeFI.

[0171] Testing was conducted to explore the influence of different injection configurations on the combustion characteristics of the engine. The first set of tests consisted of sequentially deactivating injectors and acquiring engine data for injection configurations of 6, 5, 4, 3, and 2 peripheral injectors while maintaining a constant SOI timing and injection duration. The scalability of engine load control by manipulation of the number of active injectors is demonstrated in FIG. 17.

[0172] Starting with all six peripheral injectors, the load was set to a nominal indicated mean effect pressure (IMEPg) of 5.3 bar. Without altering the injection SOI or duration, injectors were disabled one at a time until only two injectors were actively injecting fuel, resulting in a load of approximately 1.6 bar. FIG. 17 reveals a linear relationship between the engine load and the number of active injectors as expected since each injector delivers nominally equal amounts of fuel. As a reference, the CDC configuration load, for the same SOI value of -16 degrees aTDC, is shown in FIG. 17.Attorney Docket No. 10025-342W01Experimental Testing and Results #4 - Emissions Reduction Comparison

[0173] FIG. 21 shows a schematic overview of an experimental setup including a modified engine head (e.g., similar to that of FIG. 2A) installed on an experimental engine apparatus. The test cell diagram in FIG. 21 shows the placement of various testing components, controls, and systems for the experimental study. According to one experimental implementation, a simulated boost was provided using compressed air fed into the test engine, which compensated for the reduced compression ratio. Single-cylinder engines typically experience significant flow pulsations, which are naturally damped in multi-cylinder engines. Thus, the experimental engine of FIG. 21 was equipped with intake and exhaust surge tanks, each sized to 50 times the engine's displacement.

[0174] An initial comparison between CDC and PeFI with simultaneous injector firing (PeFI Sim) was made to isolate the effect of PeFI without significant changes to bulk cylinder conditions. Thus, a peak pressure limit for a given load was imposed at the same start of injection (SOI) timing which resulted in very similar combustion phasing between different injectors. Although prior testing was performed at 4 bar IMEPg (compared to 5 bar in this study) the inclusion of this data provides context and shows sensitivity to primary control parameters.

[0175] FIG. 22 shows the ensemble average cylinder pressure for all three strategies as well as a motoring pressure curve. CDC and PeFI-Sim have similar bulk pressures with less than a 4% difference in peak pressure and a slight delay in phasing for CDC. For PeFI with rate shaping (PeFI-RS), the pressure is nearly constant during the heat addition process.

[0176] FIGS. 23A-23C shows profiles of estimated fuel rate of injection (based on measured ROI data), heat release rate, and mass fraction of fuel burned (MFB) data to illustrate differences among test cases. The profiles for CDC and PeFI-Sim cases are similar except for slight differences in initial peak heat release rate (due to faster ramp-up and slightly higher peak ROI of PeFI) and injection duration (due to efficiency differences) to match the load. Estimated ROI and mass of fuel injected are insightful in demonstrating rate shaping ability of PeFI. The temporal control of the total fuel injection rate is clear for PeFI-RS in which fueling rate slowly ramps up in a controlled manner to affect the heat release rate and MFB. Note that the heat release rate was set to zero once the value dropped below 3% of the maximum value and then used to calculate the MBF.Attorney Docket No. 10025-342W01

[0177] Rate shaping induced temperature reduction was achieved by a more gradual and delayed combustion phasing that approached isobaric combustion as shown in FIG. 22 and FIGS. 23A-23C. By sequencing the injection pulses around the periphery, a more gradually increasing heat release profile was achieved that resulted in a slight pressure -rise later in the cycle. This target was theorized to effectively reduce bulk temperatures and thus NOx formation near TDC while improving BTE compared to completely isobaric combustion for same total fuel, and while maintaining elevated temperatures later in the cycle for soot oxidation. A summary of the performance of all three strategies is provided in Table 3 below.Test PCP Eff,ig Comb A / F Opacity ISNOx ISCO ISTHC CA50(bar) (%) Eff. (%) (%) (g / kWh) (g / kWh) (g / kWh) (ATDC) CDC 78 38 98.74 40.8 3.18 12.02 1.67 0.758 2 PeFI-Sim 81 40 99.44 43.1 1.27 18.40 0.32 0.787 0 PeFI-RS 54 39 99.35 41.4 1.08 6.82 0.52 0.815 16Table 3. Summary of performance data for injection strategy

[0178] To achieve a bulk temperature reduction that could reduce NOx formation, combustion phasing (CA50) must be dramatically delayed compared to CDC or BTE optimal phasing as shown visually in FIGS. 23A-23C and quantitatively in Table 3 where the CA50 of PeFI-RS was 16 degrees later than that for PeFI-Sim. At such delayed phasing under CDC conditions, the engine would tend to produce dramatically higher levels of soot and CO compared to the traditional phasing and suffer an efficiency penalty, however, that was not the case with PeFI-RS.

[0179] In FIG. 24, CDC and PeFI-Sim depict the classic Soot-NOx tradeoff. FIG. 24 includes emissions data (smaller symbols) from prior study of SOI and injection rail pressure sweeps. In FIG. 24, CDC consistently has higher opacity, and depending on conditions, can yield lower NOx but not always. PeFI-RS indeed breaks the Soot-NOx tradeoff by simultaneously reducing soot and NOx relative to both PeFI-Sim and CDC. With PeFI-RS, soot was reduced by over 15% and NOx by 63% relative to PeFI-Sim and 66% and 43% relative to CDC (see Table 3 for specific numbers).

[0180] Simultaneous soot and NOx reduction has historically been accomplished by advanced combustion modes typically referred to as low temperature combustion (LTC). These methods can nearly eliminate soot and / or NOx, but they suffer from a deterioration in combustion and stability. FIG. 25 shows that for all three cases, ISNOx reduction wasAttorney Docket No. 10025-342W01accompanied by an increase in ISCO, which would be expected as high temperatures favor NOx formation and CO oxidation. FIG. 25 (and Table 3) also shows that CDC has 35% lower NOx, but 422% higher CO compared to PeFI-Sim. Though PeFI-RS increased ISCO relative to PeFI Sim, it remained less than that of CDC despite the severely delayed combustion phasing and at the same time maintained the large reduction in soot. Specifically, compared to CDC, PeFI-RS reduced NOx by 43% and at the same time reduced ISCO by 69% and soot by 66%.

[0181] Conclusions - In these studies, a peripheral fuel injection (PeFI) concept, using multiple single-hole injectors, is presented to greatly improve fuel distribution in the combustion chamber of diesel engines. PeFI and conventional diesel combustion (CDC), with a centrally located six-hole injector, are compared experimentally via high-speed imaging of the jets evolving in a non-reacting test chamber at diesel-relevant physical dimensions, ambient densities, and fuel supply pressure. Successful implementation and operation of the test chamber demonstrate that PeFI is indeed feasible in diesel engines, requiring modifications to the cylinder head and fuel injection systems. Flow visualizations provide a visual depiction of how PeFI would shift the combustion process away from the chamber wall to eliminate flame-wall and liquid-wall interactions to reduce heat loss, incomplete combustion, and related emissions. PeFI allows effective control of the fuel distribution away from but close to the chamber periphery by varying the injector inclination angle with respect to the radius of the chamber. Experiments suggest that an inclination angle of 30 degrees or more would minimize and / or eliminate jet-to-jet interactions completely. In a reacting system, the features of PeFI to increase access to combustion air without undesired competition or interference would yield faster reaction rates and lower emissions.

[0182] PeFI is also advantageous in the near field of the injector because of its inherently faster rate of injection (ROI) of fuel. Faster injection with PeFI increases jet tip penetration length, jet width, and total jet volume compared to the baseline central injection case. In a reacting system, these features signify higher air entrainment, low equivalence ratios at the lift-off length, and reduced soot formation in premixed combustion for PeFI. Results show that an increase in jet width (or total jet volume) versus time with PeFI occurs mainly near the jet tip. The increase in the total jet volume is observed even when plotting jet volume with respect to axial distance or fuel volume injected to isolate the ROI effects. Results suggest inherent differences in the near-field flow field with PeFI. Overall, this study has shown that the concept of peripheral injection is encouraging.Attorney Docket No. 10025-342W01Configuration of Certain Implementations

[0183] The construction and arrangement of the systems and methods as shown in the various implementations are illustrative only. Although only a few implementations have been described in detail in this disclosure, many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes, and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.). For example, the position of elements may be reversed or otherwise varied, and the nature or number of discrete elements or positions may be altered or varied. Accordingly, all such modifications are intended to be included within the scope of the present disclosure. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative implementations. Other substitutions, modifications, changes, and omissions may be made in the design, operating conditions, and arrangement of the implementations without departing from the scope of the present disclosure. Any dimensions shown in the drawings are described in the specification are exemplary only and are not meant to limit the scope of the disclosure.

[0184] Generally, a controller of this disclosure includes a processor and memory. The processor can be a general-purpose processor, an application-specific integrated circuit (ASIC), one or more field programmable gate arrays (FPGAs), a group of processing components, or other suitable electronic processing structures. In some implementations, the processor is configured to execute program code stored on the memory to cause a controller to perform one or more operations, as described below in greater detail. It will be appreciated that, in implementations where a controller is part of another computing device, the components of the controller may be shared with, or the same as, the host device. For example, if a controller is implemented via another computing device (e.g., the electronic control module (ECM) or electronic control unit (ECU) of a vehicle), then the controller may utilize the processing circuit, processor(s), and / or memory of another computing device to perform the functions described herein.

[0185] The memory of a controller of the present disclosure can include one or more devices (e.g., memory units, memory devices, storage devices, etc.) for storing data and / or computer code for completing and / or facilitating the various processes described in the present disclosure. In some implementations, memory includes tangible (e.g., non- transitory), computer-readable media that stores code or instructions executable by the processor. Tangible, computer-readable media refers to any physical media that is capable ofAttorney Docket No. 10025-342W01providing data that causes a controller to operate in a particular fashion. Example tangible, computer-readable media may include, but is not limited to, volatile media, non-volatile media, removable media and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data. Accordingly, memory can include RAM, ROM, hard drive storage, temporary storage, non-volatile memory, flash memory, optical memory, or any other suitable memory for storing software objects and / or computer instructions. Memory can include database components, object code components, script components, or any other type of information structure for supporting the various activities and information structures described in the present disclosure. Memory can be communicably connected to the processor, such as via a processing circuit, and can include computer code for executing (e.g., by the processor) one or more processes described herein.

[0186] While described above as individual components, it will be appreciated that the processor and / or memory of a controller can be implemented using a variety of different types and quantities of processors and memory. For example, the processor may be a single processing device or multiple processing devices. Similarly, memory may be a single memory device or multiple memory devices. Additionally, in some implementations, a controller may be implemented within a single computing device (e.g., one server, one housing, etc.). In other implementations, the controller may be distributed across multiple devices.

[0187] When information is transferred or provided over a network or another communications connection (either hardwired, wireless, or a combination of hardwired or wireless) to a machine, the machine properly views the connection as a machine -readable medium. Thus, any such connection is properly termed a machine-readable medium.Combinations of the above are also included within the scope of machine-readable media. Machine-executable instructions include for example, instructions and data which cause a general-purpose computer, special purpose computer, or special purpose processing machines to perform a certain function or group of functions.

[0188] Although the figures show a specific order of method steps, the order of the steps may differ from what is depicted. Also, two or more steps may be performed concurrently or with partial concurrence. Such variation will depend on the software and hardware systems chosen and on designer choice. All such variations are within the scope of the disclosure. Likewise, software implementations could be accomplished with standard programmingAttorney Docket No. 10025-342W01techniques with rule-based logic and other logic to accomplish the various connection steps, processing steps, comparison steps and decision steps.

[0189] It is to be understood that the methods and systems are not limited to specific synthetic methods, specific components, or to particular compositions. It is also to be understood that the terminology used herein is for the purpose of describing particular implementations only and is not intended to be limiting.

[0190] As used in the specification and the appended claims, the singular forms “a,” “an” and “the” include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from “about” one particular value, and / or to “about” another particular value. When such a range is expressed, another implementation includes from the one particular value and / or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particularvalue forms another implementation. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

[0191] “Optional” or “optionally” means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where said event or circumstance occurs and instances where it does not.

[0192] Throughout the description and claims of this specification, the word “comprise” and variations of the word, such as “comprising” and “comprises,” means “including but not limited to,” and is not intended to exclude, for example, other additives, components, integers or steps. “Exemplary” means “an example of” and is not intended to convey an indication of a preferred or ideal implementation. “Such as” is not used in a restrictive sense, but for explanatory purposes.

[0193] Disclosed are components that can be used to perform the disclosed methods and systems. These and other components are disclosed herein, and it is understood that when combinations, subsets, interactions, groups, etc. of these components are disclosed that while specific reference of each various individual and collective combinations and permutation of these may not be explicitly disclosed, each is specifically contemplated and described herein, for all methods and systems. This applies to all aspects of this application including, but not limited to, steps in disclosed methods. Thus, if there are a variety of additional steps that canAttorney Docket No. 10025-342W01be performed it is understood that each of these additional steps can be performed with any specific implementation or combination of implementations of the disclosed methods.

Claims

Attorney Docket No. 10025-342W01CLAIMS WHA T IS CL AIMED IS:

1. A system comprising:an engine head of an engine including a hollow cylinder, the engine head comprising:a surface configured to be disposed adjacent the hollow cylinder of the engine head, the surface defining a piston cylinder mating area having a center and a mating area periphery radially spaced apart from the center, wherein the mating area periphery is configured to align with a cylinder periphery of the hollow cylinder of the engine disposed adjacent the surface;a first fuel injector disposed adjacent to the surface, the first fuel injector including a first outlet configured to be disposed adjacent the cylinder periphery of the hollow cylinder, wherein the first outlet is disposed at a first angle greater than 0 degrees with respect to a radial axis extending through the first outlet and the center of the piston cylinder mating area, and wherein the first outlet is disposed at a second angle greater than 0 degrees with respect to a plane parallel to the surface of the engine head: anda second fuel injector disposed adjacent to the surface, the second fuel injector including a second outlet configured to be disposed adjacent the cylinder periphery of the hollow cylinder and circumferentially spaced apart from the first outlet of the first fuel injector, wherein the second outlet is disposed at a first angle greater than 0 degrees with respect to a radial axis extending through the second outlet and the center of the piston cylinder mating area, and wherein the second outlet is disposed at a second angle greater than 0 degrees with respect to a plane parallel to the surface of the engine head; anda controller in electrical communication with each of the first fuel injector and the second fuel injector, the controller comprising a processor and a memory, the memory having instructions stored thereon that, when executed by the processor, cause the controller to: operate the first fuel injector to eject a first volume of fuel from the first outlet at a first time and for a first duration; andoperate the second fuel injector to eject a second volume of fuel from the second outlet at a second time that is different from the first time and for a second duration.Attorney Docket No. 10025-342W011. The system of claim 1, wherein the first angle of the first outlet is equal to the first angle of the second outlet, and wherein the second angle of the first outlet is equal to the second angle of the second outlet.

3. The system of claim 1, the engine head further comprising:a third fuel injector disposed adjacent to the surface, the third fuel injector including a third outlet configured to be disposed adjacent the cylinder periphery of the hollow cylinder and circumferentially space apart from each of the first outlet of the first fuel injector and the second outlet of the second fuel injector, wherein the third outlet is disposed at a first angle greater than 0 degrees with respect to a radial axis extending through the third outlet and the center of the piston cylinder mating area, and wherein the third outlet is disposed at a second angle greater than 0 degrees with respect to a plane parallel to the surface of the engine head, wherein the controller is further configured to operate the third fuel injector to eject a third volume of fuel from the third outlet at a third time that is different from the first time and the second time and for a third duration.

4. The system of claim 1, wherein the first volume of fuel is equal to the second volume of fuel.

5. The system of claim 1, wherein the first volume of fuel is different than the second volume of fuel.

6. The system of claim 1, wherein the first duration is equal to the second duration.

7. The system of claim 1, wherein the first duration is different than the second duration.

8. The system of claim 1, wherein the first volume of fuel is expelled from the first outlet at a first flow rate and the second volume of fuel is expelled from the second outlet at a second flow rate.

9. The system of claim 8, wherein the first flow' rate is different than the second flow rate.

10. The system of claim 8, wherein the first flow rate is equal to the second flow rate.Attorney Docket No. 10025-342W0111. The system of claim 1, wherein the first angle of the first and second outlets is in a range of 30 degrees to 50 degrees.

12. The system of claim 1, wherein the second angle of the first and second outlets is in a range of 5 to 20 degrees.

13. The system of claim 1, wherein the engine head comprises 3 to 7 fuel injectors, each fuel injector having outlets arranged circumferentially adjacent the mating area periphery.

14. The system of claim 1, wherein the first fuel injector and the second fuel injector are each coupled to and in fluid communication with a common rail injector.

15. The system of claim 1, wherein the first angle and the second angle of the first outlet and the second outlet are arranged such that the first volume of fuel ejected from the first outlet of the first fuel injector and the second volume of fuel ejected from the second outlet of the second fuel injector avoid direct physical contact before and during combustion.

16. The system of claim 1, wherein the first angle and the second angle of the first outlet and the second outlet are arranged such that the first volume of fuel ejected from the first outlet of the first fuel injector and the second volume of fuel ejected from the second outlet of the second fuel injector avoid direct physical contact with a sidewall of the hollow cylinder before and during combustion.

17. The system of claim 1, wherein a diameter of the piston cylinder mating area of the engine head is 4 inches to 40 inches.

18. The system of claim 1, wherein the fuel is diesel fuel.

19. The system of claim 1, wherein an overall fueling rate of the hollow cylinder is at a maximum when a crank angle associated with the hollow cylinder is more than 5 degrees past top dead center.Attorney Docket No. 10025-342W0120. The system of claim 1, wherein an overall heat release rate of the fuel in the hollow cylinder is at a maximum when a crank angle associated with the hollow cylinder is more than 10 degrees past top dead center.

21. The system of claim 1, wherein a maximum pressure in the hollow cylinder occurs when a crank angle associated with the hollow cylinder is more than 10 degrees past top dead center.

22. The system of claim 1, wherein a maximum temperature in the hollow cylinder occurs when a crank angle associated with the hollow cylinder is more than 10 degrees past top dead center.

23. A method of fuel injection comprising:providing an engine having a hollow cylinder and an engine head, the engine head comprising:a surface configured to be disposed adjacent the hollow cylinder of the engine head, the surface defining a piston cylinder mating area having a center and a mating area periphery radially spaced apart from the center, wherein the mating area periphery is configured to align with a cylinder periphery of the hollow cylinder of the engine disposed adjacent the surface;a first fuel injector disposed adjacent to the surface, the first fuel injector including a first outlet configured to be disposed adjacent the cylinder periphery of the hollow cylinder, wherein the first outlet is disposed at a first angle greater than 0 degrees with respect to a radial axis extending through the first outlet and the center of the piston cylinder mating area, and wherein the first outlet is disposed at a second angle greater than 0 degrees with respect to a plane parallel to the surface of the engine head; anda second fuel injector disposed adjacent to the surface, the second fuel injector including a second outlet configured to be disposed adjacent the cylinder periphery of the hollow cylinder and circumferentially spaced apart from the first outlet of the first fuel injector, wherein the second outlet is disposed at a first angle greater than 0 degrees with respect to a radial axis extending through the second outlet and the center of the piston cylinder mating area, and wherein the second outlet is disposed atAttorney Docket No. 10025-342W01a second angle greater than 0 degrees with respect to a plane parallel to the surface of the engine head;providing a controller in electrical communication with each of the first fuel injector and the second fuel injector, the controller comprising a processor and a memory, the memory having executable instruction stored thereon;operating, via the controller, the first fuel injector to eject a first volume of fuel from the first outlet at a first time and for a first duration; andoperating, via the controller, the second fuel injector to eject a second volume of fuel from the second outlet at a second time that is different from the first time and for a second duration.

24. The method of claim 23, wherein the first angle and the second angle of the first outlet and the second outlet are arranged such that the first volume of fuel ejected from the first outlet of the first fuel injector and the second volume of fuel ejected from the second outlet of the second fuel injector avoid direct physical contact before and during combustion.

25. The method of claim 23, wherein the first angle and the second angle of the first and second outlets are arranged such that the first and second volumes of fuel are spaced apart from and avoid direct contact with a sidewall of the hollow cylinder before and during combustion.

26. The method of claim 23, wherein the first volume of fuel is equal to the second volume of fuel.

27. The method of claim 23, wherein the first volume of fuel is different than the second volume of fuel.

28. The method of claim 23, wherein the first duration is equal to the second duration.

29. The method of claim 23, wherein the first duration is different than the second duration.Attorney Docket No. 10025-342W0130. The method of claim 23, wherein the first volume of fuel is expelled from the first outlet at a first flow rate and the second volume of fuel is expelled from the second outlet at a second flow rate.

31. The method of claim 30, wherein the first flow rate is different than the second flow rate.

32. The method of claim 30, wherein the first flow rate is equal to the second flow rate.

33. The method of claim 30, wherein the first angle is in a range of 30 degrees to 50 degrees.

34. The method of claim 30, wherein the second angle is in a range of 5 degrees to 20 degrees.

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