Stratified charge engine with intake pipe injection and method for it

Abstract

Internal combustion engine (100) which has the following features: a combustion chamber (210) defined at least partially within a bore (204) of a cylinder (108) by a reciprocating piston (202) with a piston crown; wherein the piston crown has a concave recess (218); an inlet air space (120) which can be connected to the combustion chamber (210) via a first inlet pipe (116) and a second inlet pipe (118) in a fluid-mediated manner, a first inlet valve (122) which is arranged in the first inlet pipe (116) and is configured to selectively connect the inlet air space (120) to the combustion chamber (210) by flow means in order to supply a lean air / fuel mixture to the combustion chamber, a second inlet valve (124) which is arranged in the second inlet pipe (118) and is configured to selectively connect the inlet air space (120) to the combustion chamber (210) by means of a flow path, a fuel injection device (126) which is arranged in the second inlet pipe (118) and is operable to supply a preselected quantity of fuel (219) therein when the second inlet valve (124) is open, in order to supply a rich air / fuel mixture into the combustion chamber (210), an ignition device (114) configured to selectively ignite an air / fuel mixture in the combustion chamber (210), wherein the concave recess (218) is aligned with the second inlet pipe (118) to direct an incoming flow of the rich air / fuel mixture to the ignition device (114), so that a stratified air / fuel mixture is present in the combustion chamber (210) prior to combustion.

Description

Technical field

[0001] This patent publication relates generally to internal combustion engines and in particular to spark-ignition internal combustion engines with port fuel injection or intake manifold injection. background

[0002] Spark-ignition engines, such as natural gas-burning engines, are typically four-stroke engines operating in an Otto or Miller combustion cycle. Given the relatively low energy content of natural gas compared to other fuels like gasoline or diesel, natural gas-burning engines with reciprocating pistons can produce emissions of unburned hydrocarbons and exhibit a tendency to knock during operation. As is known, engine knock, a phenomenon also commonly referred to as pinging or rattling, occurs in spark-ignition combustion engines when the combustion of the air / fuel mixture in the cylinder does not complete in a single combustion event.More precisely, in a typical knocking situation in a combustion cylinder, the air / fuel mixture will initiate combustion in response to ignition by the spark plug; however, one or more pockets or combustion nuclei of the air / fuel mixture will burn outside the envelope of normal combustion or the flame front. These secondary or additional combustion areas occurring within a combustion cylinder can generate pressure waves within the cylinder, which can dramatically increase cylinder pressure. Such increases in cylinder pressure can be detrimental to the service life and durability of various engine components because they increase the stresses and loads on these components.

[0003] US 6,612,285 B2 discloses a combustion system for gasoline engines that adapts the classic four-valve pentroof combustion chamber geometry to stratified charge operation by (1) restricting the fuel supply to one of the two intake ports per combustion chamber and (2) initiating combustion at an offset spark plug position with sufficient ignition lead time to force the fuel-air mixture close to a central spark plug before it is ignited at a second ignition point with less lead time. In a broad range of higher BMEP (BMW Efficiency Power), transitioning to homogeneous charge operation, central fuel metering components become active, and the engine's throttle valve remains, at least effectively, wide open.

[0004] DE 34 44 356 C2 refers to an internal combustion engine for operation with lean fuel-air mixtures.

[0005] US 5 228 423 A discloses a dual-fuel internal combustion engine that can optionally use either liquid fuel such as gasoline or gaseous fuel such as compressed natural gas (CNG), in particular such a dual-fuel internal combustion engine with a fuel intake system and valve actuation mechanism.

[0006] The present invention is aimed at overcoming one or more of the problems or disadvantages associated with the prior art. Summary

[0007] The object of the present invention is achieved by an internal combustion engine according to claim 1 and by a method for operating an internal combustion engine according to claim 7. The dependent claims relate to preferred embodiments of the invention.

[0008] The revelation describes in one aspect an internal combustion engine. The internal combustion engine has a combustion chamber, which is defined at least partially within a cylinder bore by a reciprocating piston that has a piston crown. An intake air space is fluidically connected to the combustion chamber, and at least one intake port or intake pipe is configured to fluidically connect the intake air space to the combustion chamber. At least one intake valve is configured to selectively fluidically connect the intake air space to the combustion chamber. The combustion chamber is configured to receive a lean air / fuel mixture to substantially fill the combustion chamber. The combustion chamber is further configured to receive a rich air / fuel mixture, resulting in a stratified air / fuel mixture within the combustion chamber.

[0009] According to another aspect, the disclosure describes an internal combustion engine comprising a plurality of cylinders, each containing a reciprocating piston with a piston crown and defining a combustion chamber. Each combustion chamber is fluidically connected to an intake air space via a first intake port or intake pipe with a first intake valve and to a second intake air space with a second intake valve. The first and second intake valves are configured to selectively fluidically connect the combustion chamber to the intake air space. The engine further comprises a fuel injection device associated with the second intake pipe and configured to selectively supply a gaseous fuel into the second intake pipe.The fuel mixes with air passing through the second intake port to form a rich air / fuel mixture, which enters the combustion chamber when the second intake valve is at least partially open. An ignition device protrudes into the combustion chamber. A piston bowl defined in the piston crown is configured to direct the rich air / fuel mixture to the ignition device. The first intake valve is configured to operate independently of the second intake valve, so that air or a lean air / fuel mixture is supplied to fill the combustion chamber through the first intake port when the first intake valve is open. The rich air / fuel mixture supplied to the combustion chamber when the second intake valve is open is directed through the piston bowl to the ignition device to create a stratified air / fuel charge in the combustion chamber prior to ignition.

[0010] According to yet another aspect, the disclosure describes a method for operating an internal combustion engine. The method involves opening a first intake valve to fluidically connect an intake air space of the engine to a combustion chamber via a first intake port or intake pipe. Air or a lean air / fuel mixture is supplied to the combustion chamber via the first intake pipe. A second intake valve is opened to fluidically connect the intake air space to the combustion chamber via a second intake pipe. A fuel injection device, configured to inject a gaseous fuel into the second intake pipe, is activated such that air passing through the second intake pipe mixes with fuel injected into the second intake pipe to form a rich air / fuel mixture.The rich air / fuel mixture is supplied to the combustion chamber via the second intake pipe when the second intake valve is at least partially open. The first and second intake valves close before the fuel / air mixture already present in the combustion chamber is ignited. Brief description of the drawings Fig. Figure 1 is a block diagram of an internal combustion engine with a configuration for injecting fuel into an inlet pipe according to the disclosure. Fig. Figures 2-4 are cross-sections of a configuration of an internal combustion cylinder under different operating conditions according to the disclosure. Fig. Figure 5 is a block diagram for a control device according to the disclosure. Fig. Figure 6 is an intake valve timing diagram according to the disclosure. Fig. Figure 7 is a flowchart for a method for operating an internal combustion engine according to the disclosure. Detailed description

[0011] Fig. Figure 1 is a block diagram representation of an internal combustion engine 100 according to the disclosure. As shown, the engine 100 is a stationary engine that is part of a generator set. Thus, the engine 100 has an output shaft 102 that is connected to a generator 104. During operation, the engine 100 can operate at a nearly constant engine speed but with a varying load, depending on the electrical power or current output of the generator 104. A control device 105 can be operationally associated with various engine and / or generator systems. In the illustrated embodiment, the control device 105 has operational connections to various sensors and systems of the engine 100 and the generator 104 and is configured to receive information regarding their operating parameters, as well as to send commands to various actuating devices and systems through the connections.

[0012] The Motor 100 can have various components and systems, such as lubrication systems and electrical systems, which are simplified from Fig. 1 have been omitted. Relevant for the present disclosure is that the engine 100 has a crankcase 106 with one or more combustion cylinders formed therein. Although six cylinders 108 are shown in an in-line configuration, any other number of cylinders can be used, arranged in other configurations, such as a “V-configuration”.

[0013] Each cylinder 108 has a reciprocating piston that defines a combustion chamber, which can be connected to an intake manifold 110 and an exhaust manifold 112. Each cylinder 108 has a spark plug 114. The spark plugs 114 are configured to generate one or more sparks in each combustion chamber in response to appropriate commands from the control device 105 during engine operation. For example, the control device 105 can be configured to receive timing information from the engine 100, which is used to determine the appropriate ignition timing for each combustion cylinder.

[0014] The spark supplied by each spark plug 114 causes the combustion of the air / fuel mixture present in a compressed state in each cylinder 108. Each cylinder 108 is configured to selectively draw air from the intake manifold 110, which in a naturally aspirated engine may be at or below atmospheric pressure, or alternatively, in a turbocharged or supercharged engine, at positive pressure. In the illustrated embodiment, the engine 100 has a turbocharger (not shown) which is fluidically connected in the known configuration between the intake and exhaust manifolds 110 and 112.

[0015] During operation, air is supplied from the intake manifold 110 to each cylinder 108 via first and second intake pipes 116 and 118, respectively. The first and second intake pipes 116 and 118 of each cylinder 108 can be directly connected to an intake air volume 120 of the intake manifold 110 or, alternatively, can be branches of an intake port or intake pipe (not shown) that is fluidically open to the intake air volume 120. A first intake valve 122 is arranged such that it fluidly isolates the cylinder 108 from the first intake pipe 116, and a second intake valve 124 is arranged similarly so that it fluidly isolates the cylinder 108 from the second intake port or intake pipe 118.When the first and second intake valves 122 and 124 are closed, as is the case, for example, during the combustion of the air / fuel mixture in cylinder 108, a fluid connection between each respective cylinder 108 and the intake manifold 110 is blocked. Similarly, at least partial opening of either the first and / or the second intake valve (the intake valves) 122 and 124 allows the fluid connection of cylinder 108 with the intake air volume 120, so that air 125 can enter cylinder 108.

[0016] Fuel is supplied to each cylinder 108 by a corresponding fuel injection device 126. In the illustrated embodiment, each cylinder 108 is associated with a dedicated fuel injection device 126; however, alternatively, a single fuel injection device or fewer fuel injection devices can be used. As shown, each fuel injection device 126 is arranged to supply fuel to each corresponding secondary inlet pipe 118 of each cylinder 108. The fuel injection devices 126 are configured to supply a predetermined mass or volume of fuel, such as fuel in a gaseous phase, to the secondary inlet pipes 118 as air flows through them.The fuel injection devices 126 are associated with a fuel line 128, which is arranged to supply fuel 130 to the injection devices at a predetermined pressure. The duration of each injection event, and thus the amount of fuel injected, is configured to respond to a fuel supply command sent by the electronic control device 105 to each injection device 126 via a suitable communication line (not shown).

[0017] When a special injection device 126 is activated to deliver a predetermined amount of fuel, the delivered fuel is carried into cylinder 108 by an airflow passing through each respective inlet pipe 118 while the second inlet valve 124 is open. The air / fuel mixture entering cylinder 108 through each second inlet pipe 118, which may be rich, combusts in addition to a relatively lean air / fuel mixture entering cylinder 108 through the first inlet pipe 116 when a spark is delivered by the corresponding spark plug 114. The combustion, as is known, generates power, which is transferred to the output shaft 102 to drive the generator 104.

[0018] Exhaust gas remaining after the combustion of the fuel from each injection device 126 with the air from the first and second intake pipes 122 and 124 in each cylinder 108 is evacuated and collected in the exhaust manifold 112. In the illustrated embodiment, each cylinder 108 is fluidically connected to an exhaust air volume 132 via two exhaust ports or exhaust pipes 134. Each exhaust pipe 134 can be fluidically isolated or cut off from the cylinder 108 by a corresponding exhaust valve 136. The collected exhaust gas 138 is removed from the exhaust manifold 112. Although two exhaust valves 136 are shown, corresponding to each cylinder 108, a single exhaust valve can be used, arranged in a single exhaust pipe per cylinder 108.

[0019] Fig. 2 is a cross-section of a cylinder 108. The Fig. 3 and Fig. Figure 4 shows cross-sections of the cylinder 108 under two different operating conditions, as discussed in more detail below. In the following description, structures or elements that are the same as, or similar to, corresponding structures and elements already described are designated with the same reference numerals as previously used. Accordingly, each cylinder 108 has a piston 202 configured to move back and forth within a bore 204 formed in an engine crankcase 206. A cylinder head 208 is arranged above the open end of the bore 204 to define a combustion chamber 210.The reciprocating motion of the piston 202 changes the volume of the combustion chamber 210, which is at its maximum when the piston 202 is at its lowest position or bottom dead center (BDC), and at its minimum when the piston 202 is at its highest position or top dead center (TDC). The bottom dead center and top dead center positions of the piston 202 are determined based on the relative position of a connecting rod 212 on an eccentric pin of a crankshaft (not shown). The connecting rods 212 are pivotally connected to the pistons 202 to convert the reciprocating motion of the pistons 202 into a rotary motion of the crankshaft in a known manner.

[0020] In the illustrated embodiment, the intake manifold 110 is shown connected to a side surface of the cylinder head 208, so that the intake air volume 120 is in fluid communication with the first and second intake pipes 116 and 118. The first intake pipe 116 is selectively blocked from fluid communication with the combustion chamber 210 by the first intake valve 122. Similarly, the second intake valve 124 selectively blocks the combustion chamber 210 from the second intake pipe 118. As previously described, the fuel injection device 126 is configured to inject fuel into the second intake pipe 118.In the illustrated embodiment, the fuel injection device 126 has a tip 214 which has one or more (not shown) nozzle openings which can supply fuel, for example in gaseous phase, for mixing with an air flow which passes through the second inlet pipe 118 and enters the combustion chamber 210 when the second inlet valve 124 is at least partially open.

[0021] As shown, the first and second inlet pipes 116 and 118 are fluidically connected to the inlet air space volume 120 and extend in a parallel circuit configuration between the inlet air space volume 120 and the combustion chamber 210. The first and second inlet valves 122 and 124 are operated independently to selectively admit either air or a very lean air / fuel mixture into the combustion chamber 210 through the first inlet pipe 116, and a very rich air / fuel mixture into the combustion chamber 210 through the second inlet pipe 118 when the fuel injection device 126 is active. In this way, the total amount of fuel and air present in the mixture in the combustion chamber 210 can be arranged or adjusted to provide an almost stoichiometric combustion with layered layers or areas of mixtures with different air / fuel concentrations within the combustion chamber 210.A partition wall 216 may be provided to separate at least a portion of each of the first and second inlet pipes 116 and 118, so that fuel injected into the second inlet pipe 118 by the fuel injection device 126 is substantially prevented from overflowing, splashing, or otherwise entering the first inlet pipe 116.

[0022] In the illustrated embodiment, the bottom part of the piston 202 further features a concave-shaped feature or recess 218. The recess 218 is configured to direct the rich air / fuel mixture entering the combustion chamber 210 through the second intake pipe 118 to a region 220 located adjacent to or around the tip of the spark plug 114. Generally, the shape of the recess 218 will depend on the specific engine configuration as well as on the shape of other surrounding features and components, such as the shape of the first and second intake pipes 116 and 118.In other words, the shape of the first and second intake pipes 116, the shape of the recess 218, the arrangement and orientation of the spark plug 114, the position of the piston 202 within the bore 204, and other parameters can be optimized to jointly provide a layering of the rich air / fuel mixture entering the combustion chamber 210 from the second intake pipe 118. The rich air / fuel mixture can thus be forced to occupy the area 220 of the combustion chamber surrounding the spark from the spark plug 114. As will be clear, the unique conditions present in each engine application will require at least some analysis to determine various parameters, such as combustion swirl and turbulence within the combustion chamber 210, so that the layering of the air / fuel mixture can be optimized.However, in comparison to direct injection engines, the embodiments disclosed here are advantageously configured to facilitate the layering of the air / fuel mixture in the combustion chamber 210.

[0023] In particular, each of the first and second intake valves 122 and 124 can be configured to operate independently. Their operation can be carried out according to a predetermined relationship, or the operation of each can be determined independently and variably based on various engine operating parameters, such as fuel quality, temperature, engine speed, engine load, and other parameters.

[0024] A qualitative diagram of the valve timing control for the first and second valves 116 and 118 is in Fig. Figure 6 is shown. In this diagram, a horizontal axis represents the crankshaft angle 502, with the top and bottom dead center positions of a piston marked. The valve opening degree or valve opening 504 is shown along the vertical axis. A complete standard combustion cycle, comprising an intake stroke 506, a compression stroke 508, a combustion or power stroke 510, and an exhaust stroke 512, is shown in the diagram for illustrative purposes; however, these designations should not be understood as restricting or simply describing the process occurring within the combustion chamber 210.

[0025] In the Fig. In the diagram shown, the piston travels from top dead center to bottom dead center in a movement that typically represents the intake stroke 506. During this time, the combustion chamber volume increases so that air or an air / fuel mixture can fill the combustion chamber. The diagram shows the first intake valve position curve to represent two different operating modes. As can be seen, the first intake valve, for example, the first intake valve 122, operates according to a Miller cycle. A late inlet closing (LIC) operating mode is represented by the LIC position curve 514 of the first intake valve (shown in solid lines), and an early inlet closing (EIC) operating mode is shown by the EIC position curve 516 for the first intake valve (shown in dashed lines).In LIC operating mode, the first intake valve opens late in the intake stroke 506 and remains open for part of the compression stroke 508, as qualitatively represented by the LIC position curve 514 for the first intake valve. Similarly, in EIC operating mode, the first intake valve may remain open during the exhaust stroke 512 and close early during an intake stroke 506. As previously described, the fluid entering the combustion chamber through the first intake pipe, such as the one in the... Fig. Inlet pipe 116 shown in 2-4, advantageously either air or a very lean air / fuel mixture enters, filling the combustion chamber 210 while the first inlet valve is open.

[0026] The second intake valve opens relatively briefly during the compression stroke 508, as shown by the position curve 518 for the second intake valve. This operation of the second intake valve can be the same or a similar operation, regardless of whether the first intake valve is LIC or EIC operating mode. It should be noted that during the time the second intake valve, for example, the one in the Fig. 2-4 Inlet valve 124 shown is open, the static pressure of the fluid within the corresponding inlet pipe, for example the second inlet pipe 118, is higher than the static pressure of fluids present in the combustion cylinder at that time.

[0027] The opening of the second intake valve 124 is configured to coincide, at least partially, with the injection of fuel from the injection device 126. As previously described, the injection device 126 is arranged to inject a predetermined quantity of fuel, which, together with the total quantity of air entering the combustion chamber 210 through the first and second intake valves 122 and 124, will produce an overall air / fuel mass ratio that is desirable for the specific engine, such as a stoichiometric mixture or a rich stoichiometric mixture. However, the mode or operating condition in which the fuel is distributed within the combustion chamber is stratified to promote more efficient combustion.

[0028] As especially in the Fig. 3 and Fig. As shown in Figure 4, the first inlet valve 122 can open first to admit a quantity of air into the combustion chamber 210. The operation of the first inlet valve 122 can be carried out according to a LIC or EIC Miller operating mode. The second valve 124 opens briefly to admit an additional quantity of air as well as a quantity of fuel 219 injected by the injection device 126. The first and second valves 122 and 124 can have an overlapping opening period, particularly when the first inlet valve 122 operates in a LIC operating mode, as shown, for example, by curve 514 in Figure 4. Fig. Figure 5 shows that the air entering the combustion chamber 210 through the second inlet pipe 118 is in a fuel-rich or rich air / fuel mixture. This mixture has been prevented from mixing with the air already present in the combustion chamber 210 by being directed appropriately through the shape of the second inlet pipe 118 to the recess 218. The recess 218 is optimized to direct the rich mixture to a region 220 located adjacent to the tip of the spark plug 114. As previously described, the spark plug 114 can be oriented and positioned so that it protrudes into the region 220 of the combustion chamber 210. In this way, the fuel-rich or rich mixture is better positioned for more complete combustion in a shorter period when ignition is provided. With reference to Fig. Figure 6 also shows that an ignition event 520 may follow shortly after the closing of the second inlet valve 124, so that insufficient time is provided for the rich mixture to mix with the air present in the combustion chamber 210 before ignition.

[0029] A block diagram for a 600 control system is in Fig. 6 shown. The control system can have one or more control algorithms, which are shown in the Fig. The control device 105 shown in Figure 1 operates as follows. The control device 105 can be a single control device or it can have more than one control device arranged or configured to control various functions and / or features of a motor 100 and / or a generator 104. For example, a master control device, which is used to control the overall operation and function of the system, can be configured to work in conjunction with a motor control device. In this embodiment, the term "control device" or "controller" is intended to refer to one, two, or more controllers associated with the system that can work together to control various functions and operations of the system. The operation of the control device while it is in Fig. 6. Conceptually shown for illustrative purposes only, the device can be implemented as hardware or components and / or software or programs, regardless of the discrete functionality shown. Accordingly, various interfaces of the control device are defined relative to the components of the device shown. Fig. The system shown in Figure 1 is described. Such interfaces are not intended to limit the type and number of components that are connected, nor the number of control devices that are described.

[0030] In the illustrated embodiment, the control system accepts 600 different motor parameters and other operating parameters as inputs. As in the exemplary embodiment of the Fig. As shown in Figure 6, the control system 600 is arranged to receive signals indicating the engine speed 602, the engine load 604, the crankshaft position or crankshaft timing 606, the air temperature 608, the fuel quality 610, the intake manifold pressure 612, and various other parameters as required. Each of these parameters can be used in various calculations and other determinations to provide, where relevant to the present discussion, a timing 614 for the first intake valve, a timing 616 for the second intake valve, and an ignition timing 618, among other quantities. These parameters can be determined by any suitable method, for example, by a lookup table or...A map is used to determine the timing control based on the engine speed 602 and the engine load 604, with appropriate corrections applied based on other parameters, such as the crankshaft timing or crankshaft position 606, the air temperature 608, the fuel quality 610, the boost pressure 612, and / or other parameters. Accordingly, the control system 600 has a first subroutine 620, which provides the timing signal 614 for the first intake valve, a second subroutine 622, which provides the timing signal 616 for the second intake valve, and a third subroutine 624, which provides the ignition timing signal 618. The specific operating procedures within each subroutine are configured to achieve the desired intake valve timing control.The system provides the target intake valve timing for each of the independently controlled first and second intake valves, as well as a desired ignition timing, although other timing controls or timing values ​​can be determined, such as a desired fuel injection timing, etc.

[0031] In one embodiment, each of the first and second intake valves can be actuated either by dedicated camshafts or by a single camshaft with specially designed projections that provide the desired timing for opening and closing the intake valves. In an alternative embodiment, the first and second intake valves can be actuated by a dedicated or detachable intake camshaft capable of varying the initiation and termination events for actuating the intake valves. In yet another alternative embodiment, each intake valve can be actuated by dedicated actuating devices, such as an electric or hydraulic actuator with a wide range of selective opening and closing capabilities for each intake valve. Industrial applicability

[0032] This disclosure relates generally to spark-ignition internal combustion engines. The embodiments described herein relate in particular to stationary engines that operate on natural gas, liquefied propane or LPG (liquefied petroleum gas), biogas, or any other combustible fuel, and that are connected to electric generators to produce electrical power; however, any other type of engine may be used. Accordingly, the systems and methods described herein are also applicable to engines installed in large installations, such as locomotives or marine vessels, as well as engines installed in vehicles, such as in the truck or automotive industries, although an application with a stationary engine is described here.

[0033] The disclosed embodiments comprise a natural gas engine with port fuel injection or intake manifold injection, featuring two intake valves associated with each combustion cylinder. Each of the two intake valves operates independently of the other. During operation, one intake valve opens, which can operate according to a late-closing LIC Miller cycle or an early-closing ICE Miller cycle, to admit charge air from an intake port without fuel injection into a combustion cylinder of the engine. The second of the two intake valves opens late in the compression cycle of the engine to admit a relatively rich charge into the cylinder. This second valve is located in an intake port or intake port that has a fuel injection device configured to introduce fuel into the air entering the combustion cylinder.In one embodiment, the addition of the rich air / fuel mixture is provided just before ignition of the air / fuel mixture. Additionally, the position of the fuel injection device, the shape of the intake pipes, and the shape of the piston crown are all optimized and configured to deliver the rich air / fuel mixture to the vicinity of the spark plug. In this way, ignition of the air / fuel mixture is more efficient and prevents engine knocking, as well as ensuring more complete combustion of the fuel in the combustion chamber.

[0034] A flowchart for a procedure for operating an internal combustion engine is in Fig. Figure 7 shows that the engine may have one or more intake air volumes configured to supply air to one or more combustion chambers. The method involves opening a first intake valve associated with a special combustion chamber, so that air is supplied from the intake air volume to the combustion chamber at Figure 702. A first intake port or first intake pipe, fluidically connecting the intake air volume and the combustion chamber via the first intake valve, may advantageously be provided, although other configurations may be used. In an engine operating, for example, in an EIC-Miller cycle, a single intake valve may be arranged in a single intake pipe.In such a design, a fuel injection device, which may be located in the individual air space, can remain inactive during the intake of air or a very lean air / fuel mixture into the combustion chamber.

[0035] Following the opening of the first intake valve, air or a lean air / fuel mixture is admitted into the combustion chamber at 704 via the first intake pipe. If some fuel is present in the first intake pipe, for example, left over from a previous injection event, the air passing through the first intake pipe may carry some of this residual fuel into the combustion chamber, although the resulting air / fuel mixture will be relatively lean.

[0036] A second intake valve opens at 706 to connect the intake air space or the manifold within the combustion chamber via a second intake pipe. As previously described, in an embodiment with a single intake valve located in a single intake pipe, the first and second intake valves, as described here, simply represent the first and second opening events of the single intake valve. In engines with two intake valves for each combustion chamber, for example, in engine 100, which is described in Fig. As shown in Figure 1, an extra inlet pipe can be used, for example 116 and 118.

[0037] As in Fig.As shown in Figure 1, a fuel injection device 126 can be configured to selectively supply fuel to the second inlet pipe 118. In general, the method involves activating a fuel injection device at 708, which supplies fuel to the second inlet pipe simultaneously with or immediately following the opening of the second inlet valve. In this way, a relatively rich air / fuel mixture is supplied to the combustion chamber at 710 via the second inlet pipe.

[0038] The rich air / fuel mixture is directed to an ignition device, such as a spark plug, as it enters the combustion chamber to provide a stratified air / fuel mixture at 712°C in the combustion chamber. In other words, although the total amount of air and fuel in the combustion chamber following the addition of the rich air / fuel mixture may be close to a pre-selected air / fuel ratio, such as a ratio consistent with near-stoichiometric combustion, the air / fuel mixture in the combustion chamber is not homogeneous during and immediately after the introduction of the rich air / fuel mixture.More precisely, the second intake pipe and other engine features, such as the specially shaped combustion bowl in the piston crown, can be used to generally direct the rich air / fuel mixture to a region of the combustion chamber adjacent to the ignition source. Thus, rich and lean zones can exist in the combustion chamber before ignition occurs. This stratification of the air / fuel mixture in the combustion chamber, achieved through the staged and selectively controlled addition of air and fuel to the combustion cylinder, advantageously provides more complete combustion and improved fuel utilization for the engine.

[0039] Following the generation of the stratified air / fuel mixture as described herein, the first and second intake valves can be closed in a desired sequence and timing at 714, and the air / fuel mixture is ignited at 716. Although the opening of the second intake valve occurs after the opening of the first intake valve, the closing of each valve need not follow a specific sequence. In the illustrated embodiment, the first intake valve can operate in either a LIC or an EIC Miller cycle. During operation of the first intake valve in an EIC Miller cycle, the first intake valve may open before an intake stroke of the engine begins, and it may close before a compression stroke begins. Thus, the intake valve may be closed before the second intake valve opens.The second intake valve is intended to supply the rich air / fuel mixture, which is designed to maintain the stratification of the air / fuel mixture in the combustion chamber, and which advantageously provides for the opening and closing of the second intake valve entirely within the compression stroke of the engine, while the closing occurs as soon as possible before ignition.

[0040] It will be clear that the preceding description provides examples of the disclosed system and technology. However, it is acknowledged that other elaborations of the disclosure may differ in detail from the preceding examples. Any reference to the disclosure or to examples thereof is intended to pertain to the specific example discussed at this point and is not meant to imply any limitation regarding the scope of the disclosure in general. Any mention of a rejection or lesser preference for certain features is intended to indicate that these features are less favored, but is not intended to completely exclude such features from the scope of the disclosure, except where otherwise indicated.

[0041] The mention of value ranges here is intended only as a shorthand method of naming each separate value falling within the range, unless otherwise indicated here, and each separate value will be included in the description just as if it had been named individually. All procedures described herein may be performed in any suitable order, unless otherwise indicated here or clearly contradicted by the context.

Claims

[1] Internal combustion engine (100) comprising the following: a combustion chamber (210) defined at least partially within a bore (204) of a cylinder (108) by a reciprocating piston (202) with a piston crown; wherein the piston crown has a concave recess (218); an inlet air space (120) which can be connected to the combustion chamber (210) via a first inlet pipe (116) and a second inlet pipe (118) in a fluid-mediated manner, a first inlet valve (122) which is arranged in the first inlet pipe (116) and is configured to selectively connect the inlet air space (120) to the combustion chamber (210) by flow means in order to supply a lean air / fuel mixture to the combustion chamber, a second inlet valve (124) which is arranged in the second inlet pipe (118) and is configured to selectively connect the inlet air space (120) to the combustion chamber (210) by means of a flow path, a fuel injection device (126) which is arranged in the second inlet pipe (118) and is operable to supply a preselected quantity of fuel (219) therein when the second inlet valve (124) is open, in order to supply a rich air / fuel mixture into the combustion chamber (210), an ignition device (114) configured to selectively ignite an air / fuel mixture in the combustion chamber (210), wherein the concave recess (218) is aligned with the second inlet pipe (118) to direct an incoming flow of the rich air / fuel mixture to the ignition device (114), so that a stratified air / fuel mixture is present in the combustion chamber (210) prior to combustion. [2] Internal combustion engine (100) according to claim 1, wherein the at least one inlet valve (122) is configured to operate in a late-closing LIC Miller cycle and / or an early-closing EIC Miller cycle, wherein the at least one inlet valve (122) is arranged in the at least one inlet pipe (116), and wherein an opening operation of the at least one inlet valve (122) supplies the lean air / fuel mixture into the combustion chamber (210) by allowing air (125) from the inlet air space (120) to pass through the at least one inlet pipe (116) and enter the combustion chamber (210). [3] Internal combustion engine (100) according to claim 1, further comprising an electronic control device (105) which is operationally associated with the fuel injection device (126) and the ignition device, wherein the electronic control device (105) is configured to provide a fuel injection signal to the fuel injection device (126) and an ignition signal to the ignition device based on the at least one engine operating parameter. [4] Internal combustion engine (100) according to claim 3, wherein the at least one engine operating parameter comprises an engine speed (602) and / or an engine load (604) and / or a crankshaft timing control (606) and / or an air temperature (608) and / or a fuel quality (610) and / or a boost pressure (612). [5] Internal combustion engine (100) according to claim 1, wherein the fuel injection device (126) associated with the second inlet pipe (118) is configured to selectively supply a gaseous fuel (130) into the second inlet pipe (118), which mixes with air (125) passing through the second inlet pipe (118) to form a rich air / fuel mixture, which enters the combustion chamber (210) when the second inlet valve (124) is at least partially open, wherein the recess (218) of the piston (202) is configured to direct the rich air / fuel mixture to the ignition device, wherein the first inlet valve (122) is configured to operate independently of the second inlet valve (124) so ​​that air (125) and / or an air / fuel mixture is supplied through the first inlet pipe (116). is used to fill the combustion chamber (210) when the first inlet valve (122) is open, and wherein the rich air / fuel mixture,which is supplied to the combustion chamber (210) when the second inlet valve (124) is open, is directed through the piston bowl (218) to the ignition device in order to create a stratified air / fuel charge in the combustion chamber (210) prior to ignition. [6] Internal combustion engine (100) according to claim 5, wherein the first inlet valve (122) operates in a late-closing LIC Miller cycle or in an early-closing EIC Miller cycle. [7] Method for operating an internal combustion engine (100) according to one of the preceding claims, wherein the method comprises: Opening the first inlet valve (122) to connect the intake air space (120) of the engine (100) to the combustion chamber (210) via the first inlet pipe (116) by means of a fluid flow; Supplying air (125) or a lean air / fuel mixture into the combustion chamber (210) via the first inlet pipe (116); Opening a second inlet valve (124) to connect the air space for the inlet air (125) to the combustion chamber (210) via a second inlet pipe (118) in a fluid-mediated manner; Activating a fuel injection device (126) configured to inject a gaseous fuel (130) into the second inlet pipe (118); Mixing air (125) passing through the second inlet pipe (118) with fuel (130) injected into the second inlet pipe (118) to form a rich air / fuel mixture; Supplying the rich air / fuel mixture into the combustion chamber (210) via the second inlet pipe (118) when the second inlet valve (124) is at least partially open, while a homogeneous mixing of the rich air / fuel mixture with fluids already present in the combustion chamber (210) is hindered; Closing the first and second intake valves (122 and 124); and igniting the air / fuel mixture present in the combustion chamber (210).

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