Systems and methods for application of heat for ignition of low cetane fuels

Abstract

Embodiments described herein relate to combustion of low cetane fuels in compression ignition engine architectures. In some embodiments, a method of operating a compression ignition engine can include activating a first heating device. In some embodiments, the first heating device can include a first glow plug. After a first preheating period of between about 3 seconds and about 7 seconds, the method further includes activating a second heating device. In some embodiments, the second heating device can include a second glow plug. In some embodiments, the second glow plug can be located inside of a flame plug. After a second preheating period of between about 5 seconds and about 10 seconds, a volume of air is drawn into a combustion chamber via the intake flow path.

Description

SYSTEMS AND METHODS FOR APPLICATION OF HEAT FOR IGNITION OF LOW CETANE FUELSCross-Reference to Related Applications

[0001] This application claims priority to and the benefit of U.S. Provisional Application No. 63 / 558,268, filed February 27, 2024, and entitled “SYSTEMS AND METHODS FOR APPLICATION OF HEAT FOR IGNITION OF LOW CETANE FUELS,” the disclosure of which is incorporated by reference herein in its entirety.Technical Field

[0002] Embodiments described herein relate to ignition of low cetane fuels at low environmental temperatures.Background

[0003] Burning ethanol, methanol, and other low cetane, small-molecule fuels in a mixing- controlled compression ignition (MCCI) engine requires significantly higher temperature to start combustion than diesel and other readily igniting traditional MCCI fuels. The most significant difficulty is providing enough heat to the fuel and / or the air in the engine to achieve ignition. Achieving ignition is particularly difficult in a cold environment.Summary

[0004] Embodiments described herein relate to combustion of low cetane fuels in compression ignition engine architectures. In some embodiments, a method of operating a compression ignition engine can include activating a first heating device. In some embodiments, the first heating device can include a first glow plug. After a first preheating period of between about 3 seconds and about 7 seconds, the method further includes activating a second heating device. In some embodiments, the second heating device can include a second glow plug. In some embodiments, the second glow plug can be located inside of a flame plug. After a second preheating period of between about 5 seconds and about 10 seconds, a volume of air is drawn into a combustion chamber via the intake flow path. The method further includes initiating injection of a first pilot amount of a fuel into the combustion chamberbetween about 35 CAD and about 25 CAD bTDC, such that the first pilot amount of fuel ignites at a location no more than about 5 mm from a surface of the first glow plug, the fuel having a cetane number of less than about 40. The method further includes initiating injection of a second pilot amount of the fuel into the combustion chamber between about 20 CAD and about 15 CAD bTDC such that the second pilot amount of the fuel ignites at a location at least about 10 mm from the surface of the first glow plug. The method further includes initiating injection of a combustion amount of the fuel into the combustion chamber between about 12 CAD bTDC and about 5 CAD bTDC. The method includes combusting the combustion amount of the fuel, and injecting an amount of a flame plug fuel into the intake flow path via the flame plug, such that the flame plug ignites.Brief Description of the Drawings

[0005] FIG. l is a block diagram of a compression ignition engine used for combustion of a low-cetane fuel, according to an embodiment.

[0006] FIG. 2 is a flow diagram of a method for starting a compression ignition engine with a low-cetane fuel, according to an embodiment.

[0007] FIG. 3 is a sample depiction of injection events and bum rates in a compression ignition engine with a glow plug included therein, according to an embodiment.

[0008] FIG. 4 is an illustration of a combustion chamber, according to an embodiment.

[0009] FIGS. 5A-5D are illustrations of a flame plug and connected instrumentation, according to an embodiment.

[0010] FIG. 6 is an illustration of an intake flow path and connected instrumentation, according to an embodiment.

[0011] FIGS. 7A-7B are photographs of connections between flame plugs and an intake flow path, according to an embodiment.

[0012] FIGS. 8A-8B are photographs of connections between flame plugs and an intake flow path, according to an embodiment.Detailed Description

[0013] Embodiments described herein relates to starting compression engines with low- cetane fuels, particularly in cold environments. Startup of such engines is especially difficult.Glow plugs can be employed to provide a large amount of localized heat to achieve ignition of a low cetane fuel. Additional glow plugs at multiple locations of an engine can generally lead to a greater certainty of ignition. However, glow plugs are often powered electrically. Therefore, a larger number of plugs in an engine can cause a greater drain on a vehicle’ s battery or may require supplementary batteries in the vehicle. Such an implementation can also push the alternator to its handling limit. Running at its limit can shorten its life due to heat overload of the associated electronic components.

[0014] Embodiments described herein combine the use of a glow plug to provide immediate localized heat inside a combustion chamber to fire the first few cycles and a flame plug outside of the combustion chamber to heat later cycles. In other words, a combination of close-coupled heat to start the engine and a source of significant intake air heating can accomplish satisfactory starting and operation of low cetane fuels. The close coupled heating can be in the form of glow plugs in the engine cylinders or heaters directly in or just upstream of the intake ports. A combination of glow plugs that are located near the flame deck of the cylinder head and a proper fuel injection scheme can enable initial startup of an engine with a low cetane fuel in a cold environment. Significant intake heating can then be provided via flame plugs, and / or other forms of fuel-based heater or any other electrical or other heat source in the intake path. Flame plugs can be modified to allow operation of a compression ignition engine with ethanol or any other low-cetane fuels or combinations thereof.

[0015] Examples of thermal management systems used in compression ignition engines can be found in U.S. patent No. 9,903,262 (“the ‘262 patent”), filed Apr. 6, 2015, entitled “STOICHIOMETRIC HIGH-TEMPERATURE DIRECT-INJECTION COMPRESSIONIGNITION ENGINE,” International Patent Application No. PCT / US2020 / 032961 (“the ‘961 application”), filed May 14, 2020, entitled “COLD START FOR HIGH-OCTANE FUELS IN A DIESEL ENGINE ARCHITECTURE,” U.S. Patent No. No. 11,428,186 (“the ‘ 186 patent”), filed September 16, 2021, entitled ’’FUEL AGNOSTIC COMPRESSION IGNITION ENGINE,” U.S. Patent Publication No. 2022 / 0018297 (“the ‘297 publication”), filed September 30, 2021 and titled “SYSTEMS AND METHODS OF CYLINDER DEACTIVATION IN HIGH-TEMPERATURE MIXING-CONTROLLED ENGINES,” and U.S. Provisional Patent Application No. 63 / 400,702 (“the ‘702 application”), filed August 24, 2022 and titled “FUEL-BASED HEATING TO ENABLE MIXING-CONTROLLED COMBUSTION OF SMALL MOLECULE FUELS,” the disclosures of which are hereby incorporated by reference in their entireties.

[0016] FIG. 1 is a block diagram of a compression ignition engine 100, according to an embodiment. As shown, the compression ignition engine 100 includes a combustion chamber 110, a glow plug 120, an intake flow path 130, a flame plug 140, a filter 150, and a conduit 160 fluidically coupling the filter 150 and the flame plug 140. As shown, solid line connections represent fluidic coupling between elements. In some embodiments, the compression ignition engine 100 can include a four-stroke engine. In some embodiments, the compression ignition engine 100 can include a two-stroke engine. In some embodiments, the compression ignition engine 100 can include a five-stroke engine. In some embodiments, the compression ignition engine 100 can include a six-stroke engine. In some embodiments, the compression ignition engine 100 can include a free-piston engine. In some embodiments, the compression ignition engine 100 can include a free piston engine linear. In some embodiments, the compression ignition engine 100 can include a rotary engine. In some embodiments, the compression ignition engine 100 can include a Wankel rotary engine.

[0017] The combustion chamber 110 provides a volume, in which compression ignition of the fuel occurs. The combustion chamber 110 can be situated inside a cylinder. The outside boundaries of the combustion chamber 110 can be defined by intake valves, exhaust valves, pistons, and a head deck. The piston can move up and down due to crankshaft motion, thereby expanding and contracting the volume of the combustion chamber 110. In some embodiments, the compression ignition engine 100 can include about 1, about 2, about 3, about 4, about 5, about 6, about 7, about 8, about 9, about 10, about 11, about 12, about 13, about 14, about 15, about 16, about 17, about 18, about 19, about 20, about 21, about 22, about 23, about 24, about 25, about 26, about 27, about 28, about 29, about 30, about 31, or about 32 combustion chambers 110 and / or cylinders that house combustion chambers 110.

[0018] As shown, the glow plug 120 is disposed in the combustion chamber 110. In some embodiments, the glow plug 120 can be disposed in the squish region of the combustion chamber 110. In some embodiments, the glow plug 120 can be disposed in the bowl region of the combustion chamber 110. In some embodiments, the glow plug 120 can be replaced by another close-coupled heating device, such as a plasma heater. In some embodiments, multiple close-coupled heating devices can be placed in the combustion chamber 110. In some embodiments, the combustion chamber 110 can include about 1, about 2, about 3, about 4, about 5, about 6, about 7, about 8, about 9, or about 10 glow plugs 120.

[0019] The intake flow path 130 is a conduit for movement of air into the combustion chamber 110. In some embodiments, the intake flow path 130 can be fluidically coupled to anintake valve (not shown) of the combustion chamber 110. In some embodiments, an intake manifold (not shown) can be placed in the flow path of be placed between the intake flow path 130 and multiple combustion chambers 110.

[0020] The flame plug 140 heats intake gas that enters the combustion chamber 110 via the intake flow path 130. The flame plug 140 is fluidically coupled to a fuel source. In some embodiments, the flame plug 140 can include a glow plug disposed therein. The glow plug disposed in the flame plug 140 can initiate combustion of a fuel fed through the flame plug 140. In some embodiments, the flame plug 140 can include openings for oxygen inflow to facilitate combustion. In some embodiments, the fuel combusted in the flame plug 140 can be the same as the fuel combusted in the combustion chamber 110. In some embodiments, the flame plug 140 can be angled in the intake flow path 130. The angling of the flame plug 140 can maximize exposure of the intake gas to the flame of the flame plug 140.

[0021] The filter 150 filters out dirt, particulates, and other impurities in the fuel and prevents them from entering the intake flow path. The filter 150 is separated from the flame plug 140 via the conduit 160. The conduit provides a separation between the filter 150 and the flame plug 140 so as to prevent buildup of dirt, particulates, or other impurities in the filter 150. The conduit 160 is fluidically coupled to the filter 150 and the flame plug 140.

[0022] FIG. 2 is a flow diagram of a method 10 for starting a compression ignition engine with a low-cetane fuel, according to an embodiment. As shown, the method 10 includes activating a first heating device disposed in a combustion chamber at step 11, activating a second glow plug disposed in a flame plug disposed in an intake flow path at step 12, drawing a volume of intake gas into a combustion chamber via an intake flow path at step 13, and injecting a first pilot amount of fuel into a combustion chamber at step 14. The method 10 optionally includes injecting a second amount of fuel into the combustion chamber at step 15. The method 10 further includes injecting a combustion amount of fuel into the combustion chamber at step 16, combusting the combustion amount of fuel at step 17, and optionally feeding an amount of flame plug fuel into the intake flow path via the flame plug at step 18. The method 10 optionally includes detecting a flame emerging from the flame plug at step 19 and suppressing the fuel feed from the flame plug at step 21.

[0023] Step 11 includes activating a first heating device disposed in the combustion chamber. In some embodiments, the first heating device can include a first glow plug. In some embodiments, the first glow plug can include a catalytic glow plug. In some embodiments, thefirst glow plug can be disposed in the bowl region of the combustion chamber. In some embodiments, the first glow plug can be disposed in the squish region of the combustion chamber. In some embodiments, the first glow plug can be activated before the engine begins cranking. In some embodiments, the first glow plug can be replaced with another close- coupled heating implement, such as a heater directly in or just upstream of the intake port.

[0024] Step 12 includes activating a second heating device disposed in the intake flow path. In some embodiments, the second heating device can include a second glow plug. In some embodiments, the second glow plug can include a catalytic glow plug. In some embodiments, the second glow plug can be disposed in a flame plug. The flame plug can be disposed in the intake flow path. The activation of the second glow plug can occur before feeding fuel to the flame plug. In other words, the second glow plug can initially activate without inducing ignition. In some embodiments, the activation of the second glow plug can be after the first glow plug has been active for a first preheating period. In other words, only the first glow plug is active during the first preheating period. In some embodiments, the second heating device can include a burner, a block heater, an electric grid heater, a heat exchanger with a hot fluid, an intake heater-cartridge system, an external cartridge heater, an intake heater, a fuel-powered burner, a fuel powered reactor, and / or a power relay grid heater.

[0025] In some embodiments, the first preheating period can have a duration of at least about 0.5 seconds, at least about 1 second, at least about 1.5 seconds, at least about 2 seconds, at least about 2.5 seconds, at least about 3 seconds, at least about 3.5 seconds, at least about 4 seconds, at least about 4.5 seconds, at least about 5 seconds, at least about 5.5 seconds, at least about 6 seconds, at least about 6.5 seconds, at least about 7 seconds, at least about 7.5 seconds, at least about 8 seconds, at least about 8.5 seconds, at least about 9 seconds, at least about 9.5 seconds, at least about 10 seconds, at least about 10.5 seconds, at least about 11 seconds, at least about 11.5 seconds, at least about 12 seconds, at least about 12.5 seconds, at least about 13 seconds, at least about 13.5 seconds, at least about 14 seconds, at least about 14.5 seconds, at least about 15 seconds, at least about 16 seconds, at least about 17 seconds, at least about 18 seconds, at least about 19 seconds, at least about 20 seconds, at least about 21 seconds, at least about 22 seconds, at least about 23 seconds, at least about 24 seconds, at least about 25 seconds, at least about 26 seconds, at least about 27 seconds, at least about 28 seconds, or at least about 29 seconds. In some embodiments, the first preheating period can have a duration of no more than about 30 seconds, no more than about 29 seconds, no more than about 28 seconds, no more than about 27 seconds, no more than about 26 seconds, no more than about 25 seconds, nomore than about 24 seconds, no more than about 23 seconds, no more than about 22 seconds, no more than about 21 seconds, no more than about 20 seconds, no more than about 19 seconds, no more than about 18 seconds, no more than about 17 seconds, no more than about 16 seconds, no more than about 15 seconds, no more than about 15 seconds, no more than about 14.5 seconds, no more than about 14 seconds, no more than about 13.5 seconds, no more than about 13 seconds, no more than about 12.5 seconds, no more than about 12 seconds, no more than about 11.5 seconds, no more than about 11 seconds, no more than about 10.5 seconds, no more than about 10 seconds, no more than about 9.5 seconds, no more than about 9 seconds, no more than about 8.5 seconds, no more than about 8 seconds, no more than about 7.5 seconds, no more than about 7 seconds, no more than about 6.5 seconds, no more than about 6 seconds, no more than about 5.5 seconds, no more than about 5 seconds, no more than about 4.5 seconds, no more than about 4 seconds, no more than about 3.5 seconds, no more than about 3 seconds, no more than about 2.5 seconds, no more than about 2 seconds, no more than about 1.5 seconds, or no more than about 1 second. Combinations of the above-referenced durations of the first preheating period are also possible (e.g., at least about 0.5 seconds and no more than about 30 seconds or at least about 5 seconds and no more than about 10 seconds), inclusive of all values and ranges therebetween. In some embodiments, the first preheating period can have a duration of about 0.5 seconds, about 1 second, about 1.5 seconds, about 2 seconds, about 2.5 seconds, about 3 seconds, about 3.5 seconds, about 4 seconds, about 4.5 seconds, about 5 seconds, about 5.5 seconds, about 6 seconds, about 6.5 seconds, about 7 seconds, about 7.5 seconds, about 8 seconds, about 8.5 seconds, about 9 seconds, about 9.5 seconds, about 10 seconds, about 10.5 seconds, about 11 seconds, about 11.5 seconds, about 12 seconds, about 12.5 seconds, about 13 seconds, about 13.5 seconds, about 14 seconds, about 14.5 seconds, about 15 seconds, about 16 seconds, about 17 seconds, about 18 seconds, about 19 seconds, about 20 seconds, about 21 seconds, about 22 seconds, about 23 seconds, about 24 seconds, about 25 seconds, about 26 seconds, about 27 seconds, about 27 seconds, about 28 seconds, about 29 seconds, or about 30 seconds.

[0026] Step 13 includes drawing a volume of intake gas into the combustion chamber. In some embodiments, drawing the volume of intake gas can be via cranking the engine (i.e., turning a crank shaft, such that cams allow the intake valve to be opened). In some embodiments, the cranking speed can be at least about 50 rpm, at least about 100 rpm, at least about 150 rpm, at least about 200 rpm, at least about 250 rpm, at least about 300 rpm, at least about 350 rpm, at least about 400 rpm, or at least about 450 rpm. In some embodiments, thecranking speed can be no more than about 500 rpm, no more than about 450 rpm, no more than about 400 rpm, no more than about 350 rpm, no more than about 300 rpm, no more than about 250 rpm, no more than about 200 rpm, no more than about 150 rpm, or no more than about 100 rpm. Combinations of the above-referenced cranking speeds are also possible (e.g., at least about 50 rpm and no more than about 500 rpm or at least about 200 rpm and no more than about 400 rpm), inclusive of all values and ranges therebetween. In some embodiments, the cranking speed can be about 50 rpm, about 100 rpm, about 150 rpm, about 200 rpm, about 250 rpm, about 300 rpm, about 350 rpm, about 400 rpm, about 450 rpm, or about 500 rpm.

[0027] In some embodiments, the drawing of the volume of intake gas into the combustion chamber can be after the first glow plug and the second glow plug have been active for a second preheating period. In other words, only the first glow plug is active during the first preheating period and the first glow plug and the second glow plug are active during the second preheating period. In some embodiments, the second preheating period can have a duration of at least about 0.5 seconds, at least about 1 second, at least about 1.5 seconds, at least about 2 seconds, at least about 2.5 seconds, at least about 3 seconds, at least about 3.5 seconds, at least about 4 seconds, at least about 4.5 seconds, at least about 5 seconds, at least about 5.5 seconds, at least about 6 seconds, at least about 6.5 seconds, at least about 7 seconds, at least about 7.5 seconds, at least about 8 seconds, at least about 8.5 seconds, at least about 9 seconds, at least about 9.5 seconds, at least about 10 seconds, at least about 11 seconds, at least about 12 seconds, at least about 13 seconds, at least about 14 seconds, at least about 15 seconds, at least about 16 seconds, at least about 17 seconds, at least about 18 seconds, at least about 19 seconds, at least about 20 seconds, at least about 21 seconds, at least about 22 seconds, at least about 23 seconds, at least about 24 seconds, at least about 25 seconds, at least about 26 seconds, at least about 27 seconds, at least about 28 seconds, or at least about 29 seconds. In some embodiments, the second preheating period can have a duration of no more than about 30 seconds, no more than about 29 seconds, no more than about 28 seconds, no more than about 27 seconds, no more than about 26 seconds, no more than about 25 seconds, no more than about 24 seconds, no more than about 23 seconds, no more than about 22 seconds, no more than about 21 seconds, no more than about 20 seconds, no more than about 19 seconds, no more than about 18 seconds, no more than about 17 seconds, no more than about 16 seconds, no more than about 15 seconds, no more than about 14 seconds, no more than about 13 seconds, no more than about 12 seconds, no more than about 11 seconds, no more than about 10 seconds, no more than about 9.5 seconds, no more than about 9 seconds, no more than about 8.5 seconds, no more than about 8seconds, no more than about 7.5 seconds, no more than about 7 seconds, no more than about6.5 seconds, no more than about 6 seconds, no more than about 5.5 seconds, no more than about 5 seconds, no more than about 4.5 seconds, no more than about 4 seconds, no more than about 3.5 seconds, no more than about 3 seconds, no more than about 2.5 seconds, no more than about 2 seconds, no more than about 1.5 seconds, or no more than about 1 second. Combinations of the above-referenced durations of the second preheating period are also possible (e.g., at least about 0.5 seconds and no more than about 30 seconds or at least about 3 seconds and no more than about 7 seconds), inclusive of all values and ranges therebetween. In some embodiments, the second preheating period can have a duration of about 0.5 seconds, about 1 second, about 1.5 seconds, about 2 seconds, about 2.5 seconds, about 3 seconds, about3.5 seconds, about 4 seconds, about 4.5 seconds, about 5 seconds, about 5.5 seconds, about 6 seconds, about 6.5 seconds, about 7 seconds, about 7.5 seconds, about 8 seconds, about 8.5 seconds, about 9 seconds, about 9.5 seconds, about 10 seconds, about 11 seconds, about 12 seconds, about 13 seconds, about 14 seconds, about 15 seconds, about 16 seconds, about 17 seconds, about 18 seconds, about 19 seconds, about 20 seconds, about 21 seconds, about 22 seconds, about 23 seconds, about 24 seconds, about 25 seconds, about 26 seconds, about 27 seconds, about 27 seconds, about 28 seconds, about 29 seconds, or about 30 seconds.

[0028] In some embodiments, the intake gas can include air. In some embodiments, the intake gas can include ambient air. In some embodiments, the intake gas can have an oxygen content of at least about 5 vol%, at least about 10 vol%, at least about 15 vol%, at least about 20 vol%, at least about 25 vol%, at least about 30 vol%, at least about 35 vol%, at least about 40 vol%, or at least about 45 vol%. In some embodiments, the intake gas can have an oxygen content of no more than about 50 vol%, no more than about 45 vol%, no more than about 40 vol%, no more than about 35 vol%, no more than about 30 vol%, no more than about 25 vol%, no more than about 20 vol%, no more than about 15 vol%, or no more than about 10 vol%.

[0029] In some embodiments, the temperature of the volume of intake gas can be measured as the mass-average temperature of the volume of intake gas as the volume of intake gas passes through the intake valve. In some embodiments, the temperature of the volume of intake gas can be measured as the mass-average temperature of the volume of intake gas as the volume of intake gas exits the intake manifold after EGR has been applied. In some embodiments, heaters can be used to approximate the temperature of the intake valves. In other words, the intake valves can be assumed to have the same or substantially similar temperature to the heaters. In some embodiments, the temperature of the volume of intake gas can be at least about -150 °C,at least about -140 °C, at least about -130 °C, at least about -120 °C, at least about -110 °C, at least about -100 °C, at least about -90 °C, at least about -80 °C, at least about -70 °C, at least about -60 °C, at least about -50 °C, at least about -40 °C, at least about -30 °C, at least about - 20 °C, at least about -10 °C, at least about 0 °C, at least about 10 °C, at least about 20 °C, at least about 30 °C, at least about 40 °C, at least about 50 °C, at least about 60 °C, at least about 70 °C, at least about 80 °C, at least about 90 °C, at least about 100 °C, at least about 110 °C, at least about 120 °C, at least about 130 °C, at least about 140 °C, at least about 150 °C, at least about 160 °C, at least about 170 °C, at least about 180 °C, at least about 190 °C, at least about 200 °C, at least about 210 °C, at least about 220 °C, at least about 230 °C, at least about 240 °C, at least about 250 °C, at least about 260 °C, at least about 270 °C, at least about 280 °C, or at least about 290 °C. In some embodiments, the temperature of the volume of intake gas can be no more than about 300 °C, no more than about 290 °C, no more than about 280 °C, no more than about 270 °C, no more than about 260 °C, no more than about 250 °C, no more than about 240 °C, no more than about 230 °C, no more than about 220 °C, no more than about 210 °C, no more than about 200 °C, no more than about 190 °C, no more than about 180 °C, no more than about 170 °C, no more than about 160 °C, no more than about 150 °C, no more than about 140 °C, no more than about 130 °C, no more than about 120 °C, no more than about 110 °C, no more than about 100 °C, no more than about 90 °C, no more than about 80 °C, no more than about 70 °C, no more than about 60 °C, no more than about 50 °C, no more than about 40 °C, no more than about 30 °C, no more than about 20 °C, no more than about 10 °C, no more than about 0 °C, no more than about -10 °C, no more than about -20 °C, no more than about - 30 °C, no more than about -40 °C, no more than about -50 °C, no more than about -60 °C, no more than about -70 °C, no more than about -80 °C, no more than about -90 °C, no more than about -100 °C, no more than about -110 °C, no more than about -120 °C, no more than about - 130 °C, or no more than about -140 °C. Combinations of the above-referenced temperatures are also possible (e.g., at least about -150 °C and no more than about 300 °C or at least about 0 °C and no more than about 100 °C), inclusive of all values and ranges therebetween. In some embodiments, the temperature of the volume of intake gas can be about -150 °C, about -140 °C, about -130 °C, about -120 °C, about -110 °C, about -100 °C, about -90 °C, about -80 °C, about -70 °C, about -60 °C, about -50 °C, about -40 °C, about -30 °C, about -20 °C, about -10 °C, about 0 °C, about 10 °C, about 20 °C, about 30 °C, about 40 °C, about 50 °C, about 60 °C, about 70 °C, about 80 °C, about 90 °C, about 100 °C, about 110 °C, about 120 °C, about 130 °C, about 140 °C, about 150 °C, about 160 °C, about 170 °C, about 180 °C, about 190 °C,about 200 °C, about 210 °C, about 220 °C, about 230 °C, about 240 °C, about 250 °C, about 260 °C, about 270 °C, about 280 °C, about 290 °C, or about 300 °C.

[0030] Step 14 includes injecting a first pilot amount of fuel into the combustion chamber. In some embodiments, the fuel can be injected via a fuel injector. Fuel injected in the early stages of engine warmup can have a long physical ignition delay as the fuel advances along the floor of the combustion chamber and then up the side of the bowl of the combustion chamber (i.e., to contact the first glow plug). In some embodiments, the fuel injector can be disposed inside the combustion chamber. In some embodiments, the fuel injector can be disposed just outside of the combustion chamber. In some embodiments, the fuel injector can be aimed at the first glow plug. In some embodiments, a plume of fuel can move toward the glow plug upon injection. In some embodiments, initiation of the pilot amount of fuel can initiate on the surface of the first glow plug. In some embodiments, ignition of the first pilot amount of fuel can initiate at a location within about 2 cm, within about 1.5 cm, within about 1 cm, within about 9 mm, within about 8 mm, within about 7 mm, within about 6 mm, within about 5 mm, within about 4 mm, within about 3 mm, within about 2 mm, within about 1 mm, or within about 0.5 mm of a surface of the first glow plug. The ignition of the first pilot amount of fuel releases heat and can create hot spots within the combustion chamber. In some embodiments, the first pilot amount of fuel can travel across the combustion chamber and along the floor of the piston bowl, such that the first pilot amount of fuel reaches the glow plug and ignites just as the combustion amount of fuel is injected into the combustion chamber (i.e., step 16), or during the ignition delay of the combustion amount of fuel.

[0031] In some embodiments, initiation of injection of the first pilot amount of fuel can occur no earlier than about 35 crank angle degrees (CAD) before top-dead-center (bTDC), no earlier than about 34 CAD bTDC, no earlier than about 33 CAD bTDC, no earlier than about 32 CAD bTDC, no earlier than about 31 CAD bTDC, no earlier than about 30 CAD bTDC, no earlier than about 29 CAD bTDC, no earlier than about 28 CAD bTDC, no earlier than about 27 CAD bTDC, or no earlier than about 26 CAD bTDC. In some embodiments, initiation of injection of the first pilot amount of fuel can occur no later than about 25 CAD bTDC, no later than about 26 CAD bTDC, no later than about 27 CAD bTDC, no later than about 28 CAD bTDC, no later than about 29 CAD bTDC, no later than about 30 CAD bTDC, no later than about 31 CAD bTDC, no later than about 32 CAD bTDC, no later than about 33 CAD bTDC, or no later than about 34 CAD bTDC. Combinations of the above-referenced injection timings are also possible (e.g., no earlier than about 35 CAD bTDC and no later than about 25 CAD bTDC orno earlier than about 33 CAD bTDC and no later than about 27 CAD bTDC), inclusive of all values and ranges therebetween. In some embodiments, initiation of injection of the first pilot amount of fuel can occur at about 35 CAD bTDC, about 34 CAD bTDC, about 33 CAD bTDC, about 32 CAD bTDC, about 31 CAD bTDC, about 30 CAD bTDC, about 29 CAD bTDC, about 28 CAD bTDC, about 27 CAD bTDC, about 26 CAD bTDC, or about 25 CAD bTDC.

[0032] In some embodiments, the injection of the first pilot amount of fuel can have a duration of at least about 0.5 CAD, at least about 1 CAD, at least about 1.5 CAD, at least about 2 CAD, at least about 2.5 CAD, at least about 3 CAD, at least about 3.5 CAD, at least about 4 CAD, at least about 4.5 CAD, at least about 5 CAD, at least about 5.5 CAD, at least about 6 CAD, at least about 6.5 CAD, at least about 7 CAD, at least about 7.5 CAD, at least about 8 CAD, at least about 8.5 CAD, at least about 9 CAD, or at least about 9.5 CAD. In some embodiments, the injection of the first pilot amount of fuel can have a duration of no more than about 10 CAD, no more than about 9.5 CAD, no more than about 9 CAD, no more than about 8.5 CAD, no more than about 8 CAD, no more than about 7.5 CAD, no more than about 7 CAD, no more than about 6.5 CAD, no more than about 6 CAD, no more than about 5.5 CAD, no more than about 5 CAD, no more than about 4.5 CAD, no more than about 4 CAD, no more than about 3.5 CAD, no more than about 3 CAD, no more than about 2.5 CAD, no more than about 2 CAD, no more than about 1.5 CAD, or no more than about 1 CAD. Combinations of the above-referenced injection durations are also possible (e.g., at least about 0.5 CAD and no more than about 10 CAD or at least about 3 CAD and no more than about 7 CAD), inclusive of all values and ranges therebetween. In some embodiments, the injection of the first pilot amount of fuel can have a duration of about 0.5 CAD, about 1 CAD, about 1.5 CAD, about 2CAD, about 2.5 CAD, about 3 CAD, about 3.5 CAD, about 4 CAD, about 4.5 CAD, about 5CAD, about 5.5 CAD, about 6 CAD, about 6.5 CAD, about 7 CAD, about 7.5 CAD, about 8CAD, about 8.5 CAD, about 9 CAD, about 9.5 CAD, or about 10 CAD.

[0033] In some embodiments, the first pilot amount of fuel can have a mass of at least about 5 mg, at least about 10 mg, at least about 20 mg, at least about 30 mg, at least about 40 mg, at least about 50 mg, at least about 60 mg, at least about 70 mg, at least about 80 mg, at least about 90 mg, at least about 100 mg, at least about 200 mg, at least about 300 mg, at least about 400 mg, at least about 500 mg, at least about 600 mg, at least about 700 mg, at least about 800 mg, at least about 900 mg, at least about 1 g, at least about 1.5 g, at least about 2 g, at least about 2.5 g, at least about 3 g, at least about 3.5 g, at least about 4 g, or at least about 4.5 g. In some embodiments, the first pilot amount of fuel can have a mass of no more than about 5 g,no more than about 4.5 g, no more than about 4 g, no more than about 3.5 g, no more than about 3 g, no more than about 2.5 g, no more than about 2 g, no more than about 1.5 g, no more than about 1 g, no more than about 900 mg, no more than about 800 mg, no more than about 700 mg, no more than about 500 mg, no more than about 400 mg, no more than about 300 mg, no more than about 200 mg, no more than about 100 mg, no more than about 90 mg, no more than about 80 mg, no more than about 70 mg, no more than about 60 mg, no more than about 50 mg, no more than about 40 mg, no more than about 30 mg, no more than about 20 mg, or no more than about 10 mg. Combinations of the above-referenced amounts of fuel are also possible (e.g., at least about 5 mg and no more than about 5 g or at least about 50 mg and no more than about 500 mg), inclusive of all values and ranges therebetween. In some embodiments, the first pilot amount of fuel can have a mass of about 5 mg, about 10 mg, about 20 mg, about 30 mg, about 40 mg, about 50 mg, about 60 mg, about 70 mg, about 80 mg, about 90 mg, about 100 mg, about 200 mg, about 300 mg, about 400 mg, about 500 mg, about 600 mg, about 700 mg, about 800 mg, about 900 mg, about 1 g, about 1.5 g, about 2 g, about 2.5 g, about 3 g, about 3.5 g, about 4 g, about 4.5 g, or about 5 g.

[0034] In some embodiments, the first pilot amount of fuel can include a low-cetane fuel. In some embodiments, the fuel can have a cetane number of at least about -10, at least about -5, at least about 0, at least about 5, at least about 10, at least about 15, at least about 20, at least about 25, at least about 30, or at least about 35. In some embodiments, the fuel can have a cetane number of no more than about 40, no more than about 35, no more than about 30, no more than about 25, no more than about 20, no more than about 15, no more than about 10, no more than about 5, no more than about 0, or no more than about -5. Combinations of the above-referenced cetane numbers of the fuel are also possible (e.g., at least about -10 and no more than about 40 or at least about 10 and no more than about 20), inclusive of all values and ranges therebetween. In some embodiments, the fuel can have a cetane number of about -10, about -5, about 0, about 5, about 10, about 15, about 20, about 25, about 30, about 35, or about 40.

[0035] In some embodiments, the fuel can have a flash point of at least about -50 °C, at least about -40 °C, at least about -30 °C, at least about -20 °C, at least about -10 °C, at least about 0 °C, at least about 5 °C, at least about 10 °C, at least about 15 °C, at least about 20 °C, at least about 25 °C, at least about 30 °C, at least about 35 °C, at least about 40 °C, or at least about 45 °C. In some embodiments, the fuel can have a flash point of no more than about 50 °C, no more than about 45 °C, no more than about 40 °C, no more than about 35 °C, no more than about 30°C, no more than about 25 °C, no more than about 20 °C, no more than about 15 °C, no more than about 10 °C, no more than about 5 °C, no more than about 0 °C, no more than about -10 °C, no more than about -20 °C, no more than about -30 °C, or no more than about -40 °C, Combinations of the above-referenced flash points of the fuel are also possible (e.g., at least about -50 °C and no more than about 50 °C or at least about 10 °C and no more than about 40 °C, inclusive of all values and ranges therebetween. In some embodiments, the fuel can have a flash point of about -50 °C, about -40 °C, about -30 °C, about -20 °C, about -10 °C, about 0 °C, about 5 °C, about 10 °C, about 15 °C, about 20 °C, about 25 °C, about 30 °C, about 35 °C, about 40 °C, about 45 °C, or about 50 °C.

[0036] In some embodiments, the fuel can include naphtha, gasoline, alcohol, butanol, propanol, ethanol, methanol, a gasoline / ethanol mixture, a gasoline / methanol mixture, methanol / ethanol mixture, a denatured alcohol, hydrous alcohol, gaseous hydrocarbons, natural gas, methane, ethane, propane, butane, hexane, alternative fuels, hydrogen, ammonia, syngas, and / or CO. In some embodiments, the fuel can have a low amount of additives that result in a substantial change in cetane number. In some embodiments, the fuel can include less than about 5,000 ppm, less than about 4,000 ppm, less than about 3,000 ppm, less than about 2,000 ppm, less than about 1,000 ppm, less than about 900 ppm, less than about 800 ppm, less than about 700 ppm, less than about 600 ppm, or less than about 500 ppm by weight of additives that result in a substantial change in cetane number. In some embodiments, the fuel can be substantially free of additives that result in a substantial change in cetane number.

[0037] In some embodiments, the fuel can have an octane number (i.e., calculated via (R0N+M0N) / 2 method) of at least about 50, at least about 55, at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, at least about 90, at least about 95, at least about 100, at least about 105, at least about 110, at least about 115, at least about 120, at least about 125, at least about 130, at least about 135, at least about 140, or at least about 145. In some embodiments, the fuel can have an octane number of no more than about 150, no more than about 145, no more than about 140, no more than about 135, no more than about 130, no more than about 125, no more than about 120, no more than about 115, no more than about 110, no more than about 105, no more than about 100, no more than about 95, no more than about 90, no more than about 85, no more than about 80, no more than about 75, no more than about 70, no more than about 65, no more than about 60, or no more than about 55. Combinations of the above-referenced octane numbers are also possible (e.g., at least about 50 and no more than about 150 or at least about 80 and no more than about 120), inclusive ofall values and ranges therebetween. In some embodiments, the fuel can have an octane number of about 50, about 55, about 60, about 65, about 70, about 75, about 80, about 85, about 90, about 95, about 100, about 105, about 110, about 115, about 120, about 125, about 130, about 135, about 140, about 145, or about 150.

[0038] In some embodiments, the fuel can include a fuel with 1 carbon atom per molecule (e.g., methane, methanol). In some embodiments, the fuel can be free of carbon atoms (e.g., hydrogen). In some embodiments, the fuel can include a fuel with at least about 1 carbon atom per molecule, at least about 2 carbon atoms per molecule, at least about 3 carbon atoms per molecule, at least about 4 carbon atoms per molecule, at least about 5 carbon atoms per molecule, at least about 6 carbon atoms per molecule, at least about 7 carbon atoms per molecule, at least about 8 carbon atoms per molecule, or at least about 9 carbon atoms per molecule. In some embodiments, the fuel can include a fuel with no more than about 10 carbon atoms per molecule, no more than about 9 carbon atoms per molecule, no more than about 8 carbon atoms per molecule, no more than about 7 carbon atoms per molecule, no more than about 6 carbon atoms per molecule, no more than about 5 carbon atoms per molecule, no more than about 4 carbon atoms per molecule, no more than about 3 carbon atoms per molecule, or no more than about 2 carbon atoms per molecule. Combinations of the above-referenced numbers of carbon atoms per molecule are also possible (e.g., at least about 1 carbon atom per molecule and no more than about 10 carbon atoms per molecule or at least about 1 carbon atom per molecule and no more than about 3 carbon atoms per molecule), inclusive of all values and ranges therebetween. In some embodiments, the fuel can include a fuel with about 1 carbon atom per molecule, about 2 carbon atoms per molecule, about 3 carbon atoms per molecule, about 4 carbon atoms per molecule, about 5 carbon atoms per molecule, about 6 carbon atoms per molecule, about 7 carbon atoms per molecule, about 8 carbon atoms per molecule, about 9 carbon atoms per molecule, or about 10 carbon atoms per molecule.

[0039] Step 15 is optional and includes injecting a second pilot amount of fuel into the combustion chamber. In some embodiments, the second pilot amount of fuel can have the same composition as the first pilot amount of fuel. In some embodiments, the second pilot amount of fuel can have a different composition from the first pilot amount of fuel. In some embodiments, the second pilot amount of fuel can be injected into the combustion chamber via a fuel injector. In some embodiments, the second pilot amount of fuel can be injected into the combustion chamber via the same fuel injector as the first pilot amount of fuel. In some embodiments, the second pilot amount of fuel can be aimed in the same radial direction as thefirst pilot amount of fuel. In some embodiments, the flow path of the second pilot amount of fuel can be guided differently compared to the first pilot amount of fuel because the floor of the combustion chamber is in a different position from where it was during the injection of the first pilot amount of fuel (due to the movement of the piston toward TDC).

[0040] The second pilot amount of fuel can initiate combustion at a second location in the combustion chamber, different from where the first pilot amount of fuel combusted. This can be due to a hot spot created by the combustion of the first pilot amount of fuel that enables easier ignition of the second pilot amount of fuel. In some embodiments, the injection of the second pilot amount of fuel can facilitate the momentum of the first pilot amount of fuel. In other words, the injection of the second pilot amount of fuel can keep up the momentum of the first pilot amount of fuel, such that the first pilot amount of fuel reaches the glow plug in a desired timeframe. In some embodiments, the ignition of the second pilot amount of fuel can initiate at a location at least about 3 mm, at least about 4 mm, at least about 5 mm, at least about 6 mm, at least about 7 mm, at least about 8 mm, at least about 9 mm, at least about 1 cm, at least about 1.5 cm, at least about 2 cm, at least about 2.5 cm, at least about 3 cm, at least about 3.5 cm, at least about 4 cm, at least about 4.5 cm, at least about 5 cm, at least about 5.5 cm, at least about 6 cm, at least about 6.5 cm, at least about 7 cm, at least about 7.5 cm, at least about 8 cm, at least about 8.5 cm, at least about 9 cm, at least about 9.5 cm, or at least about 10 cm from the nearest surface of the first glow plug.

[0041] In some embodiments, the second pilot amount of fuel can be injected into the combustion chamber during the same piston crank cycle as the first pilot amount of fuel (i.e., about 10 CAD to about 20 CAD later in the same cycle). In some embodiments, initiation of injection of the second pilot amount of fuel can occur no earlier than about 20 CAD bTDC, no earlier than about 19 CAD bTDC, no earlier than about 18 CAD bTDC, no earlier than about 17 CAD bTDC, no earlier than about 16 CAD bTDC, no earlier than about 15 CAD bTDC, no earlier than about 14 CAD bTDC, no earlier than about 13 CAD bTDC, no earlier than about 12 CAD bTDC, or no earlier than about 11 CAD bTDC. In some embodiments, initiation of injection of the second pilot amount of fuel can occur no later than about 10 CAD bTDC, no later than about 11 CAD bTDC, no later than about 12 CAD bTDC, no later than about 13 CAD bTDC, no later than about 14 CAD bTDC, no later than about 15 CAD bTDC, no later than about 16 CAD bTDC, no later than about 17 CAD bTDC, no later than about 18 CAD bTDC, or no later than about 19 CAD bTDC. Combinations of the above-referenced injection timings are also possible (e.g., no earlier than about 20 CAD bTDC and no later than about 10CAD bTDC or no earlier than about 18 CAD bTDC and no later than about 12 CAD bTDC), inclusive of all values and ranges therebetween. In some embodiments, initiation of injection of the second pilot amount of fuel can occur at about 20 CAD bTDC, about 19 CAD bTDC, about 18 CAD bTDC, about 17 CAD bTDC, about 16 CAD bTDC, about 15 CAD bTDC, about 14 CAD bTDC, about 13 CAD bTDC, about 12 CAD bTDC, about 11 CAD bTDC, or about 10 CAD bTDC.

[0042] In some embodiments, the injection of the second pilot amount of fuel can have a duration of at least about 0.5 CAD, at least about 1 CAD, at least about 1.5 CAD, at least about 2 CAD, at least about 2.5 CAD, at least about 3 CAD, at least about 3.5 CAD, at least about 4 CAD, at least about 4.5 CAD, at least about 5 CAD, at least about 5.5 CAD, at least about 6 CAD, at least about 6.5 CAD, at least about 7 CAD, at least about 7.5 CAD, at least about 8 CAD, at least about 8.5 CAD, at least about 9 CAD, or at least about 9.5 CAD. In some embodiments, the injection of the second pilot amount of fuel can have a duration of no more than about 10 CAD, no more than about 9.5 CAD, no more than about 9 CAD, no more than about 8.5 CAD, no more than about 8 CAD, no more than about 7.5 CAD, no more than about 7 CAD, no more than about 6.5 CAD, no more than about 6 CAD, no more than about 5.5 CAD, no more than about 5 CAD, no more than about 4.5 CAD, no more than about 4 CAD, no more than about 3.5 CAD, no more than about 3 CAD, no more than about 2.5 CAD, no more than about 2 CAD, no more than about 1.5 CAD, or no more than about 1 CAD. Combinations of the above-referenced injection durations are also possible (e.g., at least about 0.5 CAD and no more than about 10 CAD or at least about 3 CAD and no more than about 7 CAD), inclusive of all values and ranges therebetween. In some embodiments, the injection of the second pilot amount of fuel can have a duration of about 0.5 CAD, about 1 CAD, about 1.5 CAD, about 2 CAD, about 2.5 CAD, about 3 CAD, about 3.5 CAD, about 4 CAD, about 4.5 CAD, about 5 CAD, about 5.5 CAD, about 6 CAD, about 6.5 CAD, about 7 CAD, about 7.5 CAD, about 8 CAD, about 8.5 CAD, about 9 CAD, about 9.5 CAD, or about 10 CAD.

[0043] In some embodiments, the second pilot amount of fuel can have a mass of at least about 2 mg, at least about 3 mg, at least about 4 mg, at least about 5 mg, at least about 10 mg, at least about 20 mg, at least about 30 mg, at least about 40 mg, at least about 50 mg, at least about 60 mg, at least about 70 mg, at least about 80 mg, at least about 90 mg, at least about 100 mg, at least about 200 mg, at least about 300 mg, at least about 400 mg, at least about 500 mg, at least about 600 mg, at least about 700 mg, at least about 800 mg, at least about 900 mg, at least about 1 g, at least about 1.5 g, at least about 2 g, at least about 2.5 g, at least about 3 g, atleast about 3.5 g, at least about 4 g, or at least about 4.5 g. In some embodiments, the second pilot amount of fuel can have a mass of no more than about 5 g, no more than about 4.5 g, no more than about 4 g, no more than about 3.5 g, no more than about 3 g, no more than about 2.5 g, no more than about 2 g, no more than about 1.5 g, no more than about 1 g, no more than about 900 mg, no more than about 800 mg, no more than about 700 mg, no more than about 500 mg, no more than about 400 mg, no more than about 300 mg, no more than about 200 mg, no more than about 100 mg, no more than about 90 mg, no more than about 80 mg, no more than about 70 mg, no more than about 60 mg, no more than about 50 mg, no more than about 40 mg, no more than about 30 mg, no more than about 20 mg, no more than about 10 mg, no more than about 5 mg, no more than about 4 mg, or no more than about 3 mg. Combinations of the above-referenced amounts of fuel are also possible (e.g., at least about 2 mg and no more than about 5 g or at least about 50 mg and no more than about 500 mg), inclusive of all values and ranges therebetween. In some embodiments, the second pilot amount of fuel can have a mass of about 2 mg, about 3 mg, about 4 mg, about 5 mg, about 10 mg, about 20 mg, about 30 mg, about 40 mg, about 50 mg, about 60 mg, about 70 mg, about 80 mg, about 90 mg, about 100 mg, about 200 mg, about 300 mg, about 400 mg, about 500 mg, about 600 mg, about 700 mg, about 800 mg, about 900 mg, about 1 g, about 1.5 g, about 2 g, about 2.5 g, about 3 g, about 3.5 g, about 4 g, about 4.5 g, or about 5 g.

[0044] In some embodiments, the mass of the second pilot amount of fuel can be less than the mass of the first pilot amount of fuel. In some embodiments, the mass of the second pilot amount of fuel can be greater than the mass of the first pilot amount of fuel. In some embodiments, the mass of the second pilot amount of fuel can be approximately equal to the mass of the first pilot amount of fuel. In some embodiments, the mass ratio of the first pilot amount of fuel can be at least about 1 : 10, at least about 1 :9, at least about 1 :8, at least about 1 :7, at least about 1 :6, at least about 1 :5, at least about 1 :4, at least about 1 :3, at least about 1 :2, at least about 1 : 1, at least about 2: 1, at least about 3: 1, at least about 4: 1, at least about 5: 1, at least about 6: 1, at least about 7: 1, at least about 8: 1, or at least about 9: 1. In some embodiments, the mass ratio of the first pilot amount of fuel can be no more than about 10: 1, no more than about 9:1, no more than about 8: 1, no more than about 7: 1, no more than about 6: 1, no more than about 5: 1, no more than about 4: 1, no more than about 3: 1, no more than about 2: 1, no more than about 1 : 1, no more than about 1 :2, no more than about 1 :3, no more than about 1 :4, no more than about 1 :5, no more than about 1 :6, no more than about 1 :7, no more than about 1 :8, or no more than about 1 :9. Combinations of the above-referenced mass ratios are alsopossible (e.g., at least about 1 :10 and no more than about 10: 1 or at least about 1 :5 and no more than about 5: 1), inclusive of all values and ranges therebetween. In some embodiments, the mass ratio of the first pilot amount of fuel can be about 1 : 10, about 1 :9, about 1 :8, about 1 :7, about 1 :6, about 1 :5, about 1 :4, about 1 :3, about 1 :2, about 1 : 1, about 2: 1, about 3: 1, about 4: 1, about 5:1, about 6: 1, about 7: 1, about 8: 1, about 9: 1, or about 10: 1.

[0045] In some embodiments, a third pilot amount of fuel can be injected into the combustion chamber. In some embodiments, a fourth pilot amount of fuel can be injected into the combustion chamber. In some embodiments, a fifth pilot amount of fuel can be injected into the combustion chamber. In some embodiments, a sixth pilot amount of fuel can be injected into the combustion chamber. In some embodiments, a seventh pilot amount of fuel can be injected into the combustion chamber. In some embodiments, a eighth pilot amount of fuel can be injected into the combustion chamber. In some embodiments, a ninth pilot amount of fuel can be injected into the combustion chamber. In some embodiments, a tenth pilot amount of fuel can be injected into the combustion chamber. In some embodiments, the third, fourth, fifth, sixth, seventh, eighth, ninth, and / or tenth pilot amount of fuel can have any of the properties of the second pilot amount of fuel.

[0046] Step 16 includes injecting a combustion amount of fuel into the combustion chamber. The combustion amount of fuel can be the primary amount of fuel for starting the engine. In some embodiments, the injection of the combustion amount of fuel can be via a fuel injector. In some embodiments, the fuel injector can be disposed in the combustion chamber. In some embodiments, the fuel injector can be disposed just outside the combustion chamber. In some embodiments, the fuel injector that injects the first pilot amount of fuel and / or the second pilot amount of fuel can be the same as the fuel injector that injects the combustion amount of fuel. In some embodiments, the fuel injected as the combustion amount of fuel can be the same fuel as the first pilot amount of fuel and / or the second pilot amount of fuel. In some embodiments, the fuel injector can be aimed in the same radial direction during injection of the combustion amount of fuel as it was aimed during the injection of the first pilot amount of fuel and / or the second pilot amount of fuel. In some embodiments, the combustion amount of fuel can be guided differently from the first pilot amount of fuel and / or the second pilot amount of fuel due to the different position of the piston and the floor of the combustion chamber. In some embodiments, the first pilot amount of fuel can begin to combust right when the injection of the combustion amount of fuel begins (i.e., these two events occur within about 100 ms, within about 90 ms, within about 80 ms, within about 70 ms, within about 60 ms, within about 50 ms,within about 40 ms, within about 30 ms, within about 20 ms, within about 10 ms, within about 9 ms, within about 8 ms, within about 7 ms, within about 6 ms, within about 5 ms, within about4 ms, within about 3 ms, within about 2 ms, within about 1 ms, within about 0.9 ms, within about 0.8 ms, within about 0.7 ms, within about 0.6 ms, within about 0.5 ms, within about 0.4 ms, within about 0.3 ms, within about 0.2 ms, within about 0.1 ms of each other).

[0047] In some embodiments, the combustion amount of fuel can be injected into the combustion chamber during the same piston crank cycle as the first pilot amount of fuel (i.e., about 20 to about 30 CAD later in the same cycle) and / or the second pilot amount of fuel (i.e., about 10 to about 20 CAD later in the same cycle). In some embodiments, initiation of inj ection of the combustion amount of fuel can occur no earlier than about 15 CAD bTDC, no earlier than about 14 CAD bTDC, no earlier than about 13 CAD bTDC, no earlier than about 12 CAD bTDC, no earlier than about 11 CAD bTDC, no earlier than about 10 CAD bTDC, no earlier than about 9 CAD bTDC, no earlier than about 8 CAD bTDC, no earlier than about 7 CAD bTDC, no earlier than about 6 CAD bTDC, no earlier than about 5 CAD bTDC, no earlier than about 4 CAD bTDC, no earlier than about 3 CAD bTDC, no earlier than about 2 CAD bTDC, or no earlier than about 1 CAD bTDC. In some embodiments, initiation of injection of the combustion amount of fuel can occur no later than about 5 CAD bTDC, no later than about 6 CAD bTDC, no later than about 7 CAD bTDC, no later than about 8 CAD bTDC, no later than about 9 CAD bTDC, no later than about 10 CAD bTDC, no later than about 11 CAD bTDC, no later than about 12 CAD bTDC, no later than about 13 CAD bTDC, or no later than about 14 CAD bTDC. Combinations of the above-referenced injection timings are also possible (e.g., no earlier than about 15 CAD bTDC and no later than about 0 CAD bTDC or no earlier than about 12 CAD bTDC and no later than about 6 CAD bTDC), inclusive of all values and ranges therebetween. In some embodiments, initiation of injection of the combustion amount of fuel can occur at about 15 CAD bTDC, about 14 CAD bTDC, about 13 CAD bTDC, about 12 CAD bTDC, about 11 CAD bTDC, about 10 CAD bTDC, about 9 CAD bTDC, about 8 CAD bTDC, about 7 CAD bTDC, about 6 CAD bTDC, about 5 CAD bTDC, about 4 CAD bTDC, about 3 CAD bTDC, about 2 CAD bTDC, about 1 CAD bTDC, or about 0 CAD bTDC.

[0048] In some embodiments, injection of the combustion amount of fuel can last at least about 1 CAD, at least about 2 CAD, at least about 3 CAD, at least about 4 CAD, at least about5 CAD, at least about 6 CAD, at least about 7 CAD, at least about 8 CAD, at least about 9 CAD, at least about 10 CAD, at least about 11 CAD, at least about 12 CAD, at least about 13 CAD, at least about 14 CAD, at least about 15 CAD, at least about 16 CAD, at least about 17CAD, at least about 18 CAD, or at least about 19 CAD. In some embodiments, injection of the combustion amount of fuel can last no more than about 20 CAD, no more than about 19 CAD, no more than about 18 CAD, no more than about 17 CAD, no more than about 16 CAD, no more than about 15 CAD, no more than about 14 CAD, no more than about 13 CAD, no more than about 12 CAD, no more than about 11 CAD, no more than about 10 CAD, no more than about 9 CAD, no more than about 8 CAD, no more than about 7 CAD, no more than about 6 CAD, no more than about 5 CAD, no more than about 4 CAD, no more than about 3 CAD, or no more than about 2 CAD. Combinations of the above-referenced durations are also possible (e.g., at least about 1 CAD and no more than about 20 CAD or at least about 5 CAD and no more than about 15 CAD), inclusive of all values and ranges therebetween.

[0049] In some embodiments, the mass of the combustion amount of fuel can be at least about 3 mg, at least about 4 mg, at least about 5 mg, at least about 6 mg, at least about 7 mg, at least about 8 mg, at least about 9 mg, at least about 10 mg, at least about 15 mg, at least about 20 mg, at least about 30 mg, at least about 40 mg, at least about 50 mg, at least about 60 mg, at least about 70 mg, at least about 80 mg, at least about 90 mg, at least about 100 mg, at least about 200 mg, at least about 300 mg, at least about 400 mg, at least about 500 mg, at least about 600 mg, at least about 700 mg, at least about 800 mg, at least about 900 mg, at least about 1 g, at least about 2 g, at least about 3 g, at least about 4 g, at least about 5 g, at least about 6 g, at least about 7 g, at least about 8 g, at least about 9 g, at least about 10 g, at least about 11 g, at least about 12 g, at least about 13 g, at least about 14 g, at least about 15 g, at least about 16 g, at least about 17 g, at least about 18 g, or at least about 19 g. In some embodiments, the mass of the combustion amount of fuel can be no more than about 20 g, no more than about 19 g, no more than about 18 g, no more than about 17 g, no more than about 16 g, no more than about 15 g, no more than about 14 g, no more than about 13 g, no more than about 12 g, no more than about 11 g, no more than about 10 g, no more than about 9 g, no more than about 8 g, no more than about 7 g, no more than about 6 g, no more than about 5 g, no more than about 4 g, no more than about 3 g, no more than about 2 g, no more than about 1 g, no more than about 900 mg, no more than about 800 mg, no more than about 700 mg, no more than about 600 mg, no more than about 500 mg, no more than about 400 mg, no more than about 300 mg, no more than about 200 mg, no more than about 100 mg, no more than about 90 mg, no more than about 80 mg, no more than about 70 mg, no more than about 60 mg, no more than about 50 mg, no more than about 40 mg, no more than about 30 mg, no more than about 20 mg, no more than about 15 mg, no more than about 10 mg, no more than about 9 mg, no more than about 8 mg,no more than about 7 mg, no more than about 6 mg, no more than about 5 mg, or no more than about 4 mg. Combinations of the above-referenced masses are also possible (e.g., at least about 3 mg and no more than about 20 g or at least about 3 g and no more than about 10 g), inclusive of all values and ranges therebetween. In some embodiments, the mass of the combustion amount of fuel can be about 3 mg, about 4 mg, about 5 mg, about 6 mg, about 7 mg, about 8 mg, about 9 mg, about 10 mg, about 15 mg, about 20 mg, about 30 mg, about 40 mg, about 50 mg, about 60 mg, about 70 mg, about 80 mg, about 90 mg, about 100 mg, about 200 mg, about 300 mg, about 400 mg, about 500 mg, about 600 mg, about 700 mg, about 800 mg, about 900 mg, about 1 g, about 2 g, about 3 g, about 4 g, about 5 g, about 6 g, about 7 g, about 8 g, about 9 g, about 10 g, about 11 g, about 12 g, about 13 g, about 14 g, about 15 g, about 16 g, about 17 g, about 18 g, about 19 g, or about 20 g.

[0050] In some embodiments, a delay between the initial injection of the combustion amount of fuel into the combustion chamber and the onset of combustion of the combustion amount of fuel can be less than about 5 ms, less than about 4.9 ms, less than about 4.8 ms, less than about 4.7 ms, less than about 4.6 ms, less than about 4.5 ms, less than about 4.4 ms, less than about 4.3 ms, less than about 4.2 ms, less than about 4.1 ms, less than about 4 ms, less than about 3.9 ms, less than about 3.8 ms, less than about 3.7 ms, less than about 3.6 ms, less than about 3.5 ms, less than about 3.4 ms, less than about 3.3 ms, less than about 3.2 ms, less than about 3.1 ms, less than about 3 ms, less than about 2.9 ms, less than about 2.8 ms, less than about 2.7 ms, less than about 2.6 ms, less than about 2.5 ms, less than about 2.4 ms, less than about 2.3 ms, less than about 2.2 ms, less than about 2.1 ms, less than about 2 ms, less than about 1.9 ms, less than about 1.8 ms, less than about 1.7 ms, less than about 1.6 ms, less than about 1.5 ms, less than about 1.4 ms, less than about 1.3 ms, less than about 1.2 ms, less than about 1.1 ms, less than about 1 ms, less than about 0.9 ms, less than about 0.8 ms, less than about 0.7 ms, less than about 0.6 ms, or less than about 0.5 ms, inclusive of all values and ranges therebetween.

[0051] Step 17 includes combusting the combustion amount of fuel. In some embodiments, a flame front from the ignition of the combustion amount of fuel can emanate through the entire plume of the combustion amount of fuel. In some embodiments, the combustion can include combusting all or substantially all of the combustion amount of fuel. In some embodiments, at least about 50 wt%, at least about 55 wt%, at least about 60 wt%, at least about 65 wt%, at least about 70 wt%, at least about 75 wt%, at least about 80 wt%, at least about 85 wt%, at least about 90 wt%, or at least about 95 wt% of the combustion amount of fuel can be combusted. In some embodiments, no more than about 100 wt%, no more than about 95 wt%, no more thanabout 90 wt%, no more than about 85 wt%, no more than about 80 wt%, no more than about 75 wt%, no more than about 70 wt%, no more than about 65 wt%, no more than about 60 wt%, or no more than about 55 wt% of the fuel can be combusted. Combinations of the abovereferenced weight percentages are also possible. In some embodiments, about 50 wt%, about 55 wt%, about 60 wt%, about 65 wt%, about 70 wt%, about 75 wt%, about 80 wt%, about 85 wt%, about 90 wt%, about 95 wt%, or about 100 wt% of the combustion amount of fuel is combusted.

[0052] Step 18 is optional and includes feeding an amount of flame plug fuel into the intake flow path via the flame plug. In other words, the flame plug fuel moves through the flame plug and is ignited by the glow plug inside the flame plug, creating a flame that warms the intake flow path. In some embodiments, the flame plug fuel can include a steady stream of flame plug fuel to heat the intake gas that enters the combustion chamber. In some embodiments, the flame plug fuel can be the same as the fuel injected into the combustion chamber. In some embodiments, the flame plug fuel can be different from the fuel injected into the combustion chamber. In some embodiments, the flame plug fuel can have a higher cetane number than the fuel injected into the combustion chamber. In some embodiments, the flame plug fuel can have a cetane number of at least about 35, at least about 40, at least about 45, at least about 50, at least about 55, at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, at least about 90, at least about 95, or at least about 100. In some embodiments, the flame plug can be ignited before activating the first glow plug (i.e., before step 11). This can allow a longer warmup time for the flame plug. In some embodiments, the flame plug can be ignited at approximately the same time (i.e., within about 5 seconds, within about 4 seconds, within about 3 seconds, within about 2 seconds, within about 1 second, within about 900 ms, within about 800 ms, within about 700 ms, within about 600 ms, within about 500 ms, within about 400 ms, within about 300 ms, within about 200 ms, within about 100 ms, within about 90 ms, within about 80 ms, within about 70 ms, within about 60 ms, within about 50 ms, within about 40 ms, within about 30 ms, within about 20 ms, within about 10 ms, within about 9 ms, within about 8 ms, within about 7 ms, within about 6 ms, within about 5 ms, within about 4 ms, within about 3 ms, within about 2 ms, or within about 1 ms) of the first glow plug. In other words, steps 12 and / or 18 can occur before or approximately simultaneously with step 11.

[0053] In some embodiments, the injection of the flame plug fuel through the flame plug can occur after increasing the rotation speed of the crankshaft to idle speed. In some embodiments,when the flame plug fuel is initially injected through the flame plug, the crankshaft can rotate at a speed of at least about 300 rpm, at least about 350 rpm, at least about 400 rpm, at least about 450 rpm, at least about 500 rpm, at least about 550 rpm, at least about 600 rpm, at least about 650 rpm, at least about 700 rpm, at least about 750 rpm, at least about 800 rpm, at least about 850 rpm, at least about 900 rpm, at least about 950 rpm, at least about 1,000 rpm, at least about 1,050 rpm, at least about 1,100 rpm, at least about 1,150 rpm, at least about 1,200 rpm, at least about 1,250 rpm, at least about 1,300 rpm, at least about 1,350 rpm, at least about 1,400 rpm, or at least about 1,450 rpm. In some embodiments, when the flame plug fuel is initially injected through the flame plug, the crankshaft can rotate at a speed of no more than 1,500 rpm, no more than 1,450 rpm, no more than 1,400 rpm, no more than 1,350 rpm, no more than 1,300 rpm, no more than 1,250 rpm, no more than 1,200 rpm, no more than 1,150 rpm, no more than 1,100 rpm, no more than 1,050 rpm, no more than 1,000 rpm, no more than 950 rpm, no more than 900 rpm, no more than 850 rpm, no more than 800 rpm, no more than 750 rpm, no more than 700 rpm, no more than 650 rpm, no more than 600 rpm, no more than 650 rpm, no more than about 600 rpm, no more than about 550 rpm, no more than about 500 rpm, no more than about 450 rpm, no more than about 400 rpm, or no more than about 350 rpm. Combinations of the above-referenced crankshaft speeds are also possible (e.g., at least about 300 rpm and no more than about 1,500 rpm or at least about 500 rpm and no more than about 900 rpm), inclusive of all values and ranges therebetween. In some embodiments, when the flame plug fuel is initially injected through the flame plug, the crankshaft can rotate at a speed of about 300 rpm, about 350 rpm, about 400 rpm, about 450 rpm, about 500 rpm, about 550 rpm, about 600 rpm, about 650 rpm, about 700 rpm, about 750 rpm, about 800 rpm, about 850 rpm, about 900 rpm, about 950 rpm, about 1,000 rpm, about 1,050 rpm, about 1,100 rpm, about 1,150 rpm, about 1,200 rpm, about 1,250 rpm, about 1,300 rpm, about 1,350 rpm, about 1,400 rpm, about 1,450 rpm, or about 1,500 rpm.

[0054] In some embodiments, injection into any of the combustion chambers can be stopped during idling in order to confine heat in a limited number of cylinders. In other words, injection to a portion of the cylinders can be suspended to concentrate heat just a few combustion chambers of the engine. In some embodiments, the method 10 can include increasing load to the combustion chamber and deactivating the second glow plug (and the flame plug) once the engine reaches a steady state operating temperature. In some embodiments, the second glow plug can be gradually shut off as the flame becomes self-sustaining.

[0055] In some embodiments, the flowing of fuel through the flame plug to create a flame can occur after at least about 1 cycle, at least about 2 cycles, at least about 3 cycles, at least about 4 cycles, at least about 5 cycles, at least about 6 cycles, at least about 7 cycles, at least about 8 cycles, at least about 9 cycles, at least about 10 cycles, at least about 20 cycles, at least about 30 cycles, at least about 40 cycles, at least about 50 cycles, at least about 60 cycles, at least about 70 cycles, at least about 80 cycles, or at least about 90 cycles of cranking. In some embodiments, the flowing of fuel through the flame plug to create a flame can occur after no more than about 100 cycles, no more than about 90 cycles, no more than about 80 cycles, no more than about 70 cycles, no more than about 60 cycles, no more than about 50 cycles, no more than about 40 cycles, no more than about 30 cycles, no more than about 20 cycles, no more than about 10 cycles, no more than about 9 cycles, no more than about 8 cycles, no more than about 7 cycles, no more than about 6 cycles, no more than about 5 cycles, no more than about 4 cycles, no more than about 3 cycles, or no more than about 2 cycles of cranking. Combinations of the above-referenced delays are also possible (e.g., at least about 1 cycle and no more than about 100 cycles or at least about 5 cycles and no more than about 30 cycles), inclusive of all values and ranges therebetween. In some embodiments, the flowing of fuel through the flame plug to create a flame can occur after about 1 cycle, about 2 cycles, about 3 cycles, about 4 cycles, about 5 cycles, about 6 cycles, about 7 cycles, about 8 cycles, about 9 cycles, about 10 cycles, about 20 cycles, about 30 cycles, about 40 cycles, about 50 cycles, about 60 cycles, about 70 cycles, about 80 cycles, about 90 cycles, or about 100 cycles of cranking.

[0056] In some embodiments, the initial feeding of flame plug fuel can occur at least about 2 seconds, at least about 2.5 seconds, at least about 3 seconds, at least about 3.5 seconds, at least about 4 seconds, at least about 4.5 seconds, at least about 5 seconds, or at least about 5.5 seconds after the onset of cranking. In some embodiments, the initial injection of flame plug fuel can occur no more than about 6 seconds, no more than about 5.5 seconds, no more than about 5 seconds, no more than about 4.5 seconds, no more than about 4 seconds, no more than about 3.5 seconds, no more than about 3 seconds, or no more than about 2.5 seconds after the onset of cranking.

[0057] Step 19 is optional and includes detecting a flame emerging from the flame plug. In some embodiments, the detection can be via a flame sensor or a temperature sensor installed near the flame plug. In some embodiments, the temperature sensor can be installed slightly downstream of the flame plug. Step 21 is optional and includes suppressing the fuel feed tothe flame plug. This can be in response to not detecting a flame via the flame sensor. Shutting off the fuel feed to the flame plug can prevent fuel buildup in the intake flow path. Once a steady state temperature is reached throughout the engine, fuel paths that were shut off can be re-opened and corresponding fuel injection can be resumed.

[0058] FIG. 3 is a sample depiction of injection events and bum rates in a compression ignition engine with a glow plug included therein. The x-axis represents CAD in relation to TDC, while qualitative injection events and heat release are depicted along the y-axis. The blue curve represents fuel injection events, while the orange curve represents heat release from ignition and injected fuel combustion. A first pilot fuel injection event begins around 31 CAD bTDC and ends around 27 CAD bTDC. Heat is released from that first injection event starting around 15 bTDC. A second pilot fuel injection event begins around 17 CAD bTDC and ends around 15 CAD bTDC. A combustion amount of fuel is injected starting around 10 CAD bTDC and continuing until around 4 CAD after TDC (aTDC). A major heat release initiated by the second pilot injection event and the main combustion event begins around 3bTC and lasts until about 9 CAD aTDC. The onset of this major heat release can be initiated by the second pilot injection event, and it induces a quicker combustion (and therefore a quicker heat release) from the combustion of the combustion amount of fuel.

[0059] FIG. 4 is an illustration of a combustion chamber 210 and surrounding areas, according to an embodiment. As shown, the combustion chamber 210 includes a glow plug 220. In some embodiments, the combustion chamber 210 and the glow plug 220 can be the same or substantially similar to the combustion chamber 110 and the glow plug 120, as described above with reference to FIG. 1. Thus, certain aspects of the combustion chamber 210 and the glow plug 220 are not described in greater detail herein. As shown, the combustion chamber 210 includes a fuel injector 212 disposed therein, an intake valve 213, an exhaust valve 215, and a head deck 217. A piston 216 expands and contracts the combustion chamber 210.

[0060] As shown, the fuel injector 212 injects fuel into the combustion chamber 210 in in a first pilot amount Pl, a second pilot amount P2, and a combustion amount C. The streams of fuel move along the floor of the combustion chamber 210 toward the glow plug 220 to initiate ignition and combustion of the streams of fuel. In some embodiments, the streams of fuel can move through the combustion chamber 210 in the form of plumes. The combustion of the first pilot amount Pl creates a hot spot in the combustion chamber 210. In some embodiments, the first pilot amount Pl, the second pilot amount P2, and the combustion amount C can be injectedin different radial directions. The intake valve 213 allows intake gas into the combustion chamber 210 for combustion. The exhaust valve 214 expels exhaust from the combustion chamber 210. In some embodiments, the exhaust can include combusted fuel (e.g., CO2), intake gas, and uncombusted fuel.

[0061] FIGS. 5A-5D are illustrations of a flame plug 340 and connected instrumentation, according to an embodiment. As shown, the flame plug 340 includes vent holes 342, a glow plug 344, and an inlet fitting 346 and is fluidically coupled to a filter 350 via an orifice 355 and a conduit 360. FIG. 5A shows the components disconnected from each other. FIG. 5B shows an overhead view of the flame plug 340. FIG. 5C shows the components coupled to each other, while FIG. 5D shows the flame plug 340 in operation.

[0062] As shown, the flame plug 340 has a circular cross section. In some embodiments, the flame plug 340 can have an elliptical cross section. The vent holes 342 allow for oxygen to reach the fuel moving through the flame plug 340 more easily and bum near the glow plug 344. In some embodiments, the vent holes 342 can extend around the entire circumference or perimeter of the flame plug 340. In some embodiments, the vent holes 342 can extend around a portion of the circumference or the perimeter of the flame plug 340. In some embodiments, the glow plug 344 can be the same or substantially similar to the glow plug in the combustion chamber. In some embodiments, the glow plug 344 can be larger than the glow plug in the combustion chamber. In some embodiments, the glow plug 344 can be smaller than the glow plug in the combustion chamber. As shown, the glow plug 344 includes an electrical connection.

[0063] The inlet fitting 346 serves as a connection point for the conduit 360. In some embodiments, the inlet fitting 346 can be threaded. In some embodiments, the inlet fitting 346 can be bonded to the body of the flame plug 340 via an adhesive. The filter 350 prevents particulates of fuel from entering the flame plug and the intake flow path. In some embodiments, the filter 350 can be composed of a metal (e.g., stainless steel, brass). In some embodiments, the filter 350 can be composed of sintered metal. In some embodiments, the filter 350 can have a mesh configuration.

[0064] The conduit 360 provides a separation distance between the orifice 355 and the heat generated by the combustion of the flame plug fuel. High temperatures can cause dirt, particulates, grime, and other undesired substances to accumulate in the filter 350. This is of particular concern with the combustion of ethanol or other low-cetane fuels. By separatingfilter 350 spatially from the inlet fitting, the buildup of heat in the filter 350 and clogging of the filter 350 can be prevented. As shown, the conduit 360 creates a distance d between the outer surface of the body of the flame plug 340 and the filter 350. In some embodiments, the distance d can be at least about 5 mm, at least about 1 cm, at least about 2 cm, at least about 3 cm, at least about 4 cm, at least about 5 cm, at least about 6 cm, at least about 7 cm, at least about 8 cm, at least about 9 cm, at least about 10 cm, at least about 20 cm, at least about 30 cm, at least about 40 cm, at least about 50 cm, at least about 60 cm, at least about 70 cm, at least about 80 cm, at least about 90 cm, at least about 1 m, at least about 1.5 m, at least about 2 m, at least about 3 m, at least about 3.5 m at least about 4 m, or at least about 4.5 m. In some embodiments, the distance d can be no more than about 5 m, no more than about 4.5 m, no more than about 4 m, no more than about 3.5 m, no more than about 3 m, no more than about 3.5 m, no more than about 3 m, no more than about 2.5 m, no more than about 2 m, no more than about 1.5 m, no more than about 1 m, no more than about 90 cm, no more than about 80 cm, no more than about 70 cm, no more than about 60 cm, no more than about 50 cm, no more than about 40 cm, no more than about 30 cm, no more than about 20 cm, no more than about 10 cm, no more than about 9 cm, no more than about 8 cm, no more than about 7 cm, no more than about 6 cm, no more than about 5 cm, no more than about 4 cm, no more than about 3 cm, no more than about 2 cm, no more than about 1 cm, no more than about 9 mm, no more than about 8 mm, no more than about 7 mm, or no more than about 6 mm. Combinations of the above-referenced distances d are also possible (e.g., at least about 5 mm and no more than about 5 m or at least about 5 cm and no more than about 50 cm), inclusive of all values and ranges therebetween. In some embodiments, the distance d can be about 5 mm, about 1 cm, about 2 cm, about 3 cm, about 4 cm, about 5 cm, about 6 cm, about 7 cm, about 8 cm, about 9 cm, about 10 cm, about 20 cm, about 30 cm, about 40 cm, about 50 cm, about 60 cm, about 70 cm, about 80 cm, about 90 cm, about 1 m, about 1.5 m, about 2 m, about 3 m, about 3.5 m about 4 m, about 4.5 m, or about 5 m. In some embodiments, the conduit 360 can include a flexible hose. In some embodiments, the conduit 360 can be composed of Teflon (PTFE) tubing with a braided stainless steel sheath.

[0065] The orifice 355 allows for the metering of the flame plug fuel therethrough. In some embodiments, the orifice 355 can limit the passage of flame plug fuel. In some embodiments, the orifice 355 can include a valve for suppression of movement of flame plug fuel. In some embodiments, a valve can be placed on any portion of the fluidic pathway of the flame plug fuel. In some embodiments, the orifice 355 can have an inner diameter of at least about 50 pm,at least about 60 pm, at least about 70 pm, at least about 80 pm, at least about 90 pm, at least about 100 pm, at least about 200 pm, at least about 300 pm, at least about 400 pm, at least about 500 pm, at least about 600 pm, at least about 700 pm, at least about 800 pm, at least about 900 pm, at least about 1 mm, at least about 2 mm, at least about 3 mm, at least about 4 mm, at least about 5 mm, at least about 6 mm, at least about 7 mm, at least about 8 mm, or at least about 9 mm. In some embodiments, the orifice 355 can have an inner diameter of no more than about 1 cm, no more than about 9 mm, no more than about 8 mm, no more than about 7 mm, no more than about 6 mm, no more than about 5 mm, no more than about 4 mm, no more than about 3 mm, no more than about 2 mm, no more than about 1 mm, no more than about 900 pm, no more than about 800 pm, no more than about 700 pm, no more than about 600 pm, no more than about 500 pm, no more than about 400 pm, no more than about 300 pm, no more than about 200 pm, no more than about 100 pm, no more than about 90 pm, no more than about 80 pm, no more than about 70 pm, or no more than about 60 pm. Combinations of the above-referenced inner diameters are also possible (e.g., at least about 50 pm and no more than about 1 cm or at least about 500 pm and no more than about 3 mm), inclusive of all values and ranges therebetween. In some embodiments, the orifice 355 can have an inner diameter of about 50 pm, about 60 pm, about 70 pm, about 80 pm, about 90 pm, about 100 pm, about 200 pm, about 300 pm, about 400 pm, about 500 pm, about 600 pm, about 700 pm, about 800 pm, about 900 pm, about 1 mm, about 2 mm, about 3 mm, about 4 mm, about 5 mm, about 6 mm, about 7 mm, about 8 mm, about 9 mm, or about 1 cm.

[0066] The filter 350 is upstream of the orifice 355 and protects the orifice 355 from particulates and degradation. In some embodiments, the filter 350 can be upstream of the orifice 355 by a distance of at least about 50 pm, at least about 60 pm, at least about 70 pm, at least about 80 pm, at least about 90 pm, at least about 100 pm, at least about 200 pm, at least about 300 pm, at least about 400 pm, at least about 500 pm, at least about 600 pm, at least about 700 pm, at least about 800 pm, at least about 900 pm, at least about 1 mm, at least about 2 mm, at least about 3 mm, at least about 4 mm, at least about 5 mm, at least about 6 mm, at least about 7 mm, at least about 8 mm, at least about 9 mm, at least about 1 cm, at least about 2 cm, at least about 3 cm, at least about 4 cm, at least about 5 cm, at least about 6 cm, at least about 7 cm, at least about 8 cm, at least about 9 cm, at least about 10 cm, at least about 20 cm, at least about 30 cm, at least about 40 cm, at least about 50 cm, at least about 60 cm, at least about 70 cm, at least about 80 cm, at least about 90 cm, at least about 1 m, at least about 2 m, at least about 3 m, at least about 4 m, at least about 5 m, at least about 6 m, at least about 7 m,at least about 8 m, or at least about 9 m. In some embodiments, the filter 350 can be upstream of the orifice 355 by a distance of no more than about 10 m, no more than about 9 m, no more than about 8 m, no more than about 7 m, no more than about 6 m, no more than about 5 m, no more than about 4 m, no more than about 3 m, no more than about 2 m, no more than about 1 m, no more than about 90 cm, no more than about 80 cm, no more than about 70 cm, no more than about 60 cm, no more than about 50 cm, no more than about 40 cm, no more than about 30 cm, no more than about 20 cm, no more than about 10 cm, no more than about 9 cm, no more than about 8 cm, no more than about 7 cm, no more than about 6 cm, no more than about 5 cm, no more than about 4 cm, no more than about 3 cm, no more than about 2 cm, no more than about 1 cm, no more than about 9 mm, no more than about 8 mm, no more than about 7 mm, no more than about 6 mm, no more than about 5 mm, no more than about 4 mm, no more than about 3 mm, no more than about 2 mm, no more than about 1 mm, no more than about 900 pm, no more than about 800 pm, no more than about 700 pm, no more than about 600 pm, no more than about 500 pm, no more than about 400 pm, no more than about 300 pm, no more than about 200 pm, no more than about 100 pm, no more than about 90 pm, no more than about 80 pm, no more than about 70 pm, no more than about 60 pm, no more than about 50 pm, no more than about 40 pm, no more than about 30 pm, or no more than about 20 pm. Combinations of the above-referenced distances are also possible (e.g., at least about 20 pm and no more than about 10 m or at least about 5 mm and no more than about 1 m), inclusive of all values and ranges therebetween. In some embodiments, the filter 350 can be upstream of the orifice 355 by a distance of about 50 pm, about 60 pm, about 70 pm, about 80 pm, about 90 pm, about 100 pm, about 200 pm, about 300 pm, about 400 pm, about 500 pm, about 600 pm, about 700 pm, about 800 pm, about 900 pm, about 1 mm, about 2 mm, about 3 mm, about 4 mm, about 5 mm, about 6 mm, about 7 mm, about 8 mm, about 9 mm, about 1 cm, about 2 cm, about 3 cm, about 4 cm, about 5 cm, about 6 cm, about 7 cm, about 8 cm, about 9 cm, about 10 cm, about 20 cm, about 30 cm, about 40 cm, about 50 cm, about 60 cm, about 70 cm, about 80 cm, about 90 cm, about 1 m, about 2 m, about 3 m, about 4 m, about 5 m, about 6 m, about 7 m, about 8 m, about 9 m, or about 10 m.

[0067] FIG. 6 is an illustration of an intake flow path 430 and connected instrumentation, according to an embodiment. As shown, four flame plugs 440a, 440b, 440c, 440d (collectively referred to as flame plugs 440) are disposed in the intake flow path 430. FIG. 6 also includes conduits 460a, 460b, 460c, 460d (collectively referred to as conduits 460), a fuel supply 470, solenoid valves 480a, 480b (collectively referred to as solenoid valves 480), and supply lines475a, 475b (collectively referred to as supply lines 475). FIG. 6 shows a cross-sectional view of the intake flow path 430. In some embodiments, the intake flow path 430, the flame plugs 440, and the conduits 460 can be the same or substantially similar to the intake flow path 330, the flame plug 340, and the conduit 360, as described above with reference to FIGS. 5A-5D. This, certain aspects of the intake flow path 430, the flame plugs 440, and the conduits 460 are not described in greater detail herein.

[0068] The conduits 460 join the solenoid valves 480 to the flame plugs 440. In some embodiments, the conduits 460 can include one or more flexible hoses. In some embodiments, the conduits 460 can include one or more steel braided hoses. The fuel supply 470 contains a fuel and the fuel is fed to the flame plugs 440. The fuel flows from the fuel supply 470 to the solenoid valves 480 via the supply lines 475 and then from the solenoid valves 480 to the flame plugs 440 via the conduits 460. In some embodiments, the supply lines 475 can be composed of Tygon®, rubber, Teflon, nylon, braided steel, an elastomer, or any other suitable material. In some embodiments, the supply lines 475 can be composed of the same material as the conduits 460. The solenoid valves 480 control the movement of fuel through the conduits 460 from the supply lines 475. As shown, each of the supply lines 475 feeds to a single solenoid valve 480 which feeds to two conduits 460. As shown, the solenoid valves 480 can be configured to feed to zero, one, or two conduits 460. For example, the solenoid 480a can be opened to feed to both the conduit 460a and the conduit 460b, only the conduit 460a, only the conduit 460b, or neither the conduit 460a nor the conduit 460b.

[0069] FIGS. 7A-7B are photographs of an intake flow path 530 and connected instrumentation, according to an embodiment. As shown, four flame plugs 540a, 540b, 540c, 540d (collectively referred to as flame plugs 540) are disposed in the intake flow path 530. FIG. 7A also includes conduits 560a, 560b (collectively referred to as conduits 560), a fuel supply 570, solenoid valve 580, and electrical wires 565a, 565b (collectively referred to as electrical wires 565). FIG. 7A shows an outside view of the intake flow path 530. FIG. 7B shows a close-up view of the solenoid valve 580 and associated filters 550a, 550b (collectively referred to as filters 550) and orifices 555a, 555b (collectively referred to as orifices 555) and a supply line 575. In some embodiments, the intake flow path 530, the flame plugs 540, the conduits 560, the fuel supply 570, the supply line 575, and the solenoid valve 580 can be the same or substantially similar to intake flow path 430, the flame plugs 440, the conduits 460, the fuel supply 470, the supply lines 475, and the solenoid valves 480, as described above with reference to FIG. 6. In some embodiments, the filters 550 and the orifices 555 can be the sameor substantially similar to the filter 350 and the orifice 355, as described above with reference to FIGS. 5A-5D. Thus, certain aspects of the intake flow path 530, the flame plugs 540, the filters 550, the orifices 555, the conduits 560, the fuel supply 570, the supply line 575, and the solenoid valve 580.

[0070] The electrical lines 565 provide power to the glow plugs (not shown) in the flame plugs 560. In some embodiments, the electrical lines 565 can be fed from a battery. In some embodiments, the electrical lines 565 can be fed from the same battery that powers other components of the vehicle. In some embodiments, the electrical lines 565 can be fed from a secondary battery or a backup battery.

[0071] FIGS. 8A-8B are photographs of an intake flow path 630 and connected instrumentation, according to an embodiment. As shown, flame plugs 640a, 640b, 640c, 640d (collectively referred to as flame plugs 640), flame sensors 647a, 647b, 647c, 647d (collectively referred to as flame sensors 647), and deflectors 648a, 648b, 648c, 648d (collectively referred to as deflectors 648). The flame plugs 640 include glow plugs 644a, 644b, 644c, 644d (collectively referred to as glow plugs 644). FIG. 8A shows a cross-sectional view of the intake flow path 630 looking upstream, while FIG. 8B shows a cross-sectional view of the intake flow path 630 looking downstream. In some embodiments, the flame plugs 640 and the glow plugs 644 can be the same or substantially similar to the flame plug 340 and the glow plug 344, as described above with reference to FIGS. 5A-5D. Thus, certain aspects of the flame plugs 640 and the glow plugs 644 are not described in greater detail herein.

[0072] The flame sensors 647 can detect whether the flame plugs 640 are producing flames. If the flame plugs 640 are not producing flames, the fuel feed to the flame plugs 640 can be shut off to prevent fuel waste and overcharging of fuel into the intake flow path 630. In some embodiments, the flame sensors 647 can include temperature sensors. In some embodiments, the flame sensors 647 can include ionization sensors, temperature sensors, and / or infrared (IR) sensors. The signal from UV and IR sensors can be correlated to determine whether a flame is present. The deflectors 648 prevent intake gas from blowing out the flames emerging from the flame plugs 640. In some embodiments, the deflectors 648 can be oriented tangentially to the inner wall of the intake flow path 630. In some embodiments, the deflectors 648 can form angles with the inner wall of the intake flow path 630 to minimize bending of the deflectors 648 as intake gas flows by the deflectors 648. In other words, the deflectors 648 can be angled away from the flow of the intake gas. In some embodiments, the deflectors 648 can form an angle with the inner wall of the intake flow path 630 of about 5 degrees, about 10 degrees,about 15 degrees, about 20 degrees, about 25 degrees, about 30 degrees, about 35 degrees, about 40 degrees, about 45 degrees, about 50 degrees, about 55 degrees, about 60 degrees, about 65 degrees, about 70 degrees, about 75 degrees, about 80 degrees, about 85 degrees, or about 90 degrees, inclusive of all values and ranges therebetween. In some embodiments, the deflectors 648 can be composed of metal. In some embodiments, the deflectors 648 can be welded to the inner wall of the intake flow path 630. In some embodiments, the intake flow path 630 can be absent of the deflectors 648.

[0073] In some embodiments, an engine can employ the strategies described herein in parallel. While independent use of each of these methods is possible, their combination is within the scope of this disclosure.

[0074] Various concepts may be embodied as one or more methods, of which at least one example has been provided. The acts performed as part of the method may be ordered in any suitable way. Accordingly, embodiments may be constructed in which acts are performed in an order different than illustrated, which may include performing some acts simultaneously, even though shown as sequential acts in illustrative embodiments. Put differently, it is to be understood that such features may not necessarily be limited to a particular order of execution, but rather, any number of threads, processes, services, servers, and / or the like that may execute serially, asynchronously, concurrently, in parallel, simultaneously, synchronously, and / or the like in a manner consistent with the disclosure. As such, some of these features may be mutually contradictory, in that they cannot be simultaneously present in a single embodiment. Similarly, some features are applicable to one aspect of the innovations, and inapplicable to others.

[0075] In addition, the disclosure may include other innovations not presently described. Applicant reserves all rights in such innovations, including the right to embodiment such innovations, file additional applications, continuations, continuations-in-part, divisionals, and / or the like thereof. As such, it should be understood that advantages, embodiments, examples, functional, features, logical, operational, organizational, structural, topological, and / or other aspects of the disclosure are not to be considered limitations on the disclosure as defined by the embodiments or limitations on equivalents to the embodiments. Depending on the particular desires and / or characteristics of an individual and / or enterprise user, database configuration and / or relational model, data type, data transmission and / or network framework, syntax structure, and / or the like, various embodiments of the technology disclosed herein maybe implemented in a manner that enables a great deal of flexibility and customization as described herein.

[0076] All definitions, as defined and used herein, should be understood to control over dictionary definitions, definitions in documents incorporated by reference, and / or ordinary meanings of the defined terms.

[0077] As used herein, in particular embodiments, the terms “about” or “approximately” when preceding a numerical value indicates the value plus or minus a range of 10%. Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limit of that range and any other stated or intervening value in that stated range is encompassed within the disclosure. That the upper and lower limits of these smaller ranges can independently be included in the smaller ranges is also encompassed within the disclosure, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the disclosure.

[0078] The phrase “and / or,” as used herein in the specification and in the embodiments, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Multiple elements listed with “and / or” should be construed in the same fashion, i.e., “one or more” of the elements so conjoined. Other elements may optionally be present other than the elements specifically identified by the “and / or” clause, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, a reference to “A and / or B”, when used in conjunction with open-ended language such as “comprising” can refer, in one embodiment, to A only (optionally including elements other than B); in another embodiment, to B only (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); etc.

[0079] As used herein in the specification and in the embodiments, “or” should be understood to have the same meaning as “and / or” as defined above. For example, when separating items in a list, “or” or “and / or” shall be interpreted as being inclusive, i.e., the inclusion of at least one, but also including more than one, of a number or list of elements, and, optionally, additional unlisted items. Only terms clearly indicated to the contrary, such as “only one of’ or “exactly one of,” or, when used in the embodiments, “consisting of,” will refer to theinclusion of exactly one element of a number or list of elements. In general, the term “or” as used herein shall only be interpreted as indicating exclusive alternatives (i.e., “one or the other but not both”) when preceded by terms of exclusivity, such as “either,” “one of,” “only one of,” or “exactly one of.” “Consisting essentially of,” when used in the embodiments, shall have its ordinary meaning as used in the field of patent law.

[0080] As used herein in the specification and in the embodiments, the phrase “at least one,” in reference to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elements and not excluding any combinations of elements in the list of elements. This definition also allows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase “at least one” refers, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, “at least one of A and B” (or, equivalently, “at least one of A or B,” or, equivalently “at least one of A and / or B”) can refer, in one embodiment, to at least one, optionally including more than one, A, with no B present (and optionally including elements other than B); in another embodiment, to at least one, optionally including more than one, B, with no A present (and optionally including elements other than A); in yet another embodiment, to at least one, optionally including more than one, A, and at least one, optionally including more than one, B (and optionally including other elements); etc.

[0081] As used herein, “fuel” can refer to any material capable of producing an exothermic chemical reaction with an intake mixture, regardless of the fuel’s cetane number. This can include fuels and blends of: naphtha, gasoline, alcohol fuels (including butanol, propanol, ethanol, and methanol), gaseous hydrocarbons (including natural gas, methane, ethane, propane, butane, hexane, etc.) and alternative fuels such as hydrogen, ammonia, syngas, CO, etc.

[0082] As used herein, “plume” can refer to a mass of fuel spreading from an injection point, which may be entraining or mixing with the volume of intake charge as it progresses spatially and / or temporally during a fuel injection event.

[0083] As used herein, “intake charge” refers to a volume of material that enters a combustion chamber prior to a combustion event. The intake charge can include air,atmospheric air, humid air, air enriched with oxygen, air diluted with exhaust gas, air diluted with inert gas, fuel, uncombusted fuel, or any combination thereof.

[0084] As used herein, “small-molecule fuels” refers to fuels having less than or equal to four carbon atoms per molecule on average (including zero carbon atoms per molecule). This can include hydrogen, ammonia, carbon monoxide (CO), syngas, natural gas, methane, methanol, ethane, ethene, ethanol, di-methyl-ether, propane, propanol, butane, butanol, isobutanol, and other fuels and fuel blends meeting the criteria of less than or equal to four carbon atoms per molecule on average.

[0085] As used herein, “combustion efficiency” can refer to the degree to which air and fuel are fully combusted to form the products of complete combustion. As a non-limiting example, combustion efficiency can be calculated using lower heating value (LHV) of the fuel (e.g., ethanol, methanol, etc.) and combustion products (e.g., CO2, H2O, etc.), as set forth below:Where:^combustion is the combustion efficiency;LHVproductsis the LHV of the combustion products (MJ / kg); massproductsis the mass of the combustion products (kg);LHVfUei is the LHV of the fuel (MJ / kg); and massfueiis the mass of the fuel (kg).

[0086] As used herein, “efficiency,” “thermal efficiency,” or “LHV efficiency” can refer to the conversion of fuel energy to mechanical work, calculated as follows:Where: i] is the efficiency;Work is the amount of mechanical work achieved (J), which can be the indicated work calculated from the pressure in the engine cylinder, or the brake work, where the work ismeasured at the point of the rotating shaft going from the engine into a transmission or generator (i.e., the “brake thermal efficiency);LHVfUei is the LHV of the fuel (J / kg); and massfueiis the mass of the fuel (kg).

[0087] As used herein, a numerical definition of a “crank angle” or an “engine crank angle” should be understood as the crank angle relative to a fixed point in the engine cycle (as described below in Table 1 for the case of a four-stroke engine). In other words, in a four- stroke engine, the engine crank angle is 0° (or 720°) when the piston is in the TDC position between the exhaust stroke and the intake stroke. The engine crank angle is 360° when the piston is in the TDC position between the compression stroke and the expansion stroke. The engine crank angle is 540° when the piston is in the BDC position between the expansion stroke and the exhaust stroke. The engine crank angle is 180° when the piston is in the BDC position between the intake stroke and the compression stroke. Negative numbers can also be used to describe the crank angle relative to the TDC position between the exhaust stroke and the intake stroke. In other words, 540° can also be described as -180°, 360° can also be described as - 360°, and 180° can also be described as -540°.Table 1. Crank Angle Descriptions for a Four Stroke Engine

[0088] In some embodiments, the term “immediately prior to ignition” or “just prior to ignition” can refer to a temporal point, at which the engine crank angle is about 300°, about 305°, about 310°, about 315°, about 320°, about 325°, about 330°, about 335°, about 340°, about 345°, about 350°, about 355°, about 360°, about 365°, about 370°, about 375°, or about 380°, inclusive of all values and ranges therebetween.

[0089] In some embodiments, the term “immediately prior to ignition” or “just prior to ignition” can refer to a temporal point of approximately 50 ms, approximately 40 ms, approximately 30 ms, approximately 20 ms, approximately 10 ms, approximately 5 ms, approximately 2 ms, approximately 1 ms, approximately 0.5 ms, or approximately 0.1 ms, prior to ignition, inclusive of all values and ranges therebetween.

[0090] In some embodiments, the term “immediately prior to ignition” or “just prior to ignition” can refer to a temporal point preceding the time at which 5% of the fuel exothermicity is observed to have happened. In other words, the fuel can be considered to have ignited when a measurable deviation in pressure could be detected to indicate exothermic fuel oxidation is occurring.

[0091] In some embodiments, the term “immediately prior to ignition” or “just prior to ignition” can refer to a temporal point about 1 crank angle degree, about 2 crank angle degrees, about 3 crank angle degrees, about 4 crank angle degrees, about 5 crank angle degrees, about 6 crank angle degrees, about 7 crank angle degrees, about 8 crank angle degrees, about 9 crank angle degrees, about 10 crank angle degrees, about 11 crank angle degrees, about 12 crank angle degrees, about 13 crank angle degrees, about 14 crank angle degrees, about 15 crank angle degrees, about 16 crank angle degrees, about 17 crank angle degrees, about 18 crank angle degrees, about 19 crank angle degrees, or about 20 crank angle degrees prior to ignition, inclusive of all values and ranges therebetween.

[0092] In some embodiments, the term “immediately prior to ignition” or “just prior to ignition” can refer to a temporal point about 50 ms, about 40 ms, about 30 ms, about 20 ms, about 10 ms, about 5 ms, about 2 ms, or about 1 ms prior to onset of ignition, inclusive of all values and ranges therebetween.

[0093] In some embodiments, the term “immediately prior to fuel injection” or “just prior to fuel injection” can refer to a temporal point about 1 crank angle degree, about 2 crank angle degrees, about 3 crank angle degrees, about 4 crank angle degrees, about 5 crank angle degrees, about 6 crank angle degrees, about 7 crank angle degrees, about 8 crank angle degrees, about 9 crank angle degrees, about 10 crank angle degrees, about 11 crank angle degrees, about 12 crank angle degrees, about 13 crank angle degrees, about 14 crank angle degrees, about 15 crank angle degrees, about 16 crank angle degrees, about 17 crank angle degrees, about 18 crank angle degrees, about 19 crank angle degrees, or about 20 crank angle degrees prior to fuel injection, inclusive of all values and ranges therebetween.

[0094] In some embodiments, the term “immediately prior to fuel injection” or “just prior to fuel injection” can refer to a temporal point about 50 ms, about 40 ms, about 30 ms, about 20 ms, about 10 ms, about 5 ms, about 2 ms, or about 1 ms prior to fuel injection, inclusive of all values and ranges therebetween.

[0095] In some embodiments, the term “valve closing” (e.g., “intake valve closing” or “exhaust valve closing”) can refer to a temporal point, wherein the valve becomes fully seated (i.e., 0 mm valve lift). In some embodiments, the term “valve opening” (e.g., “intake valve opening” or “exhaust valve opening”) can refer to a temporal point, wherein the valve becomes unseated (i.e., >0 mm lift).

[0096] In the embodiments, as well as in the specification above, all transitional phrases such as “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” “holding,” “composed of,” and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases “consisting of’ and “consisting essentially of’ shall be closed or semi-closed transitional phrases, respectively, as set forth in the United States Patent Office Manual of Patent Examining Procedures, Section 2111.03.

[0097] In some embodiments, the novel, high-temperature mixing-controlled strategy described herein can be implemented in an opposed piston engine. This could include 2 or more pistons configured to compress an inducted charge, the engine potentially having no cylinder head. This could be a two-four-or other number of stroke design.

[0098] While specific embodiments of the present disclosure have been outlined above, many alternatives, modifications, and variations will be apparent to those skilled in the art. Accordingly, the embodiments set forth herein are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the disclosure. Where methods and steps described above indicate certain events occurring in a certain order, those of ordinary skill in the art having the benefit of this disclosure would recognize that the ordering of certain steps may be modified and such modification are in accordance with the variations of the invention. Additionally, certain of the steps may be performed concurrently in a parallel process when possible, as well as performed sequentially as described above. The embodiments have been particularly shown and described, but it will be understood that various changes in form and details may be made.

Claims

Claims1. A method of operating a compression ignition engine, the method comprising: activating a first heating device, the first heating device including a first glow plug; after a first preheating period of between about 3 seconds and about 7 seconds, activating a second heating device; drawing a volume of air into the combustion chamber via the intake flow path; initiating injection of a first pilot amount of a fuel in the combustion chamber between about 35 CAD and about 25 CAD bTDC, the fuel having a cetane number of less than about 40; initiating injection of a second pilot amount of the fuel into the combustion chamber between about 20 CAD and about 15 CAD bTDC such that the second pilot amount of the fuel ignites at a location at least about 10 mm from the surface of the first glow plug; initiating injection of a combustion amount of the fuel into the combustion chamber between about 12 CAD and about 5 CAD bTDC; and combusting the combustion amount of the fuel.

2. The method of claim 1, wherein the second heating device includes a second glow plug disposed in the intake flow path.

3. The method of claim 1, wherein the second heating device includes at least one of a burner, a block heater, an electric grid heater, a heat exchanger with a hot fluid, an intake heater-cartridge system, an external cartridge heater, an intake heater, a fuel-powered burner, a fuel powered reactor, or a power relay grid heater.

4. The method of claim 2, further comprising: metering an amount of a flame plug fuel into the intake flow path via a flame plug, such that the flame plug ignites via the second glow plug.

5. The method of claim 1, wherein the combustion amount of fuel is at least two times the first pilot amount of a fuel.

6. The method of claim 4, wherein the flame plug fuel is chemically the same as the fuel injected into the combustion chamber.

7. The method of claim 2, further comprising: increasing a load to the combustion chamber; and deactivating the second glow plug.

8. The method of claim 1, further comprising: recirculating an amount of exhaust back to the combustion chamber.

9. The method of claim 4, wherein the flame plug includes a fuel inlet and the compression ignition engine further includes an orifice and a conduit joining the fuel inlet and the orifice such that the fuel inlet and the orifice are separated by a distance of at least about 5 mm.

10. The method of claim 4, wherein injecting the amount of the flame plug fuel into the intake flow path occurs while the internal combustion engine rotates at idle speed.

11. The method of claim 10, wherein the internal combustion engine’s idle speed is at least about 500 rpm.

12. The method of claim 1, further comprising: detecting, via a flame sensor, the presence or absence of a flame emerging from the flame plug.

13. The method of claim 11, further comprising: upon detecting the absence of a flame emerging from the flame plug, discontinuing a flow of the flame plug fuel through the flame plug.

14. The method of claim 4, wherein injecting the amount of flame plug fuel occurs during a later engine cycle than activating the first glow plug.

15. The method of claim 1, wherein the first pilot amount of fuel ignites at a location no more than about 5 mm from a surface of the first glow plug.

16. A compression ignition engine, comprising: a combustion chamber;an intake flow path; a first glow plug disposed in the combustion chamber; a flame plug disposed in the intake flow path, the flame plug including a second glow plug and an inlet; a fuel filter; and a conduit fluidically coupling the fuel filter and the inlet, the conduit separating the fuel filter and the inlet by a distance of at least about 2 cm.

17. The compression ignition engine of claim 16, wherein the conduit separates the fuel filter and the inlet by a distance of at least about 5 cm.

18. The compression ignition engine of claim 16, wherein the conduit includes a hose.

19. The compression ignition engine of claim 16, further comprising: a solenoid valve coupled to the conduit and configured to regulate flow of the fuel through the conduit.

20. The compression ignition engine of claim 16, wherein the flame plug is a first flame plug, the compression ignition engine further comprising a second flame plug disposed in the intake flow path.

21. The compression ignition engine of claim 16, further comprising: a deflector disposed in the intake flow path and configured to block air from interacting with a flame emerging from the flame plug.

22. The compression ignition engine of claim 16, further comprising: a flame sensor disposed in the intake flow path and configured to detect whether a flame is emerging from the flame plug.

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