Systems and methods for combusting unconventional fuel chemistries in a diesel engine architecture
Embodiments described herein relate to systems and methods of operating internal combustion (IC) engines by combusting various fuel chemistries therein. Specifically, engines described herein can operate a wide range of fuel chemistries with varying molecular formulas. The chemical compositions of the fuels described herein make them more difficult to ignite than long chain hydrocarbons (i.e., fuels that include 6 or more carbon atoms in a molecule). In some embodiments, engines described herein can combust fuels that have the chemical properties of alcohols. In some embodiments, engines described herein can combust fuels that include hydroxide groups. Examples of such fuels include methanol and/or ethanol. In some embodiments, engines described herein can combust natural gas. These fuel chemistries are difficult to ignite, particularly at low temperatures and during initial engine startup. Systems and methods described herein address these ignition difficulties, particularly in diesel engine architectures.
1 . A method of operating a compression ignition engine during a cold-start time period, the compression ignition engine defining a combustion chamber, the method comprising:
drawing a volume of air into the combustion chamber during the cold-start time period, the cold-start time period designated as a time period in which the volume of air has a mass-average temperature of less than about 50° C. at the moment the volume of air enters the combustion chamber;
compressing the volume of air at a compression ratio of between about 15 and about 25;
transferring a volume of a single, alcohol-based fuel having a cetane number of less than 20 into the combustion chamber, the volume of the single, alcohol-based fuel and the volume of air forming an air-fuel mix; and
igniting the air-fuel mix.
2 . The method of claim 1 , wherein compressing the volume of air includes moving a piston disposed in the combustion chamber from a bottom dead center position to a top dead center position.
3 . The method of claim 1 , wherein at least about 20% of the volume of the single, alcohol-based fuel is pre-mixed with the volume of compressed air immediately prior to ignition.
4 . The method of claim 3 , wherein at least about 50% of the volume of the single, alcohol-based fuel is pre-mixed with the volume of air immediately prior to ignition.
5 . The method of claim 1 , wherein the igniting causes all of the volume of the air-fuel mix to combust.
6 . The method of claim 1 , wherein the igniting is caused by an ignition-assist device, the ignition-assist device located in a bowl region of the combustion chamber.
7 . The method of claim 6 , wherein the ignition-assist device includes at least one of a glow plug, a spark plug, a plasma ignition device, and/or a cartridge heater.
8 . The method of claim 1 , wherein:
drawing the volume of air into the combustion chamber includes opening an intake valve coupled to the combustion chamber, and
the method further comprises:
prior to igniting the air-fuel mix, closing the intake valve at an engine crank angle between 175 and 255 degrees, and
opening the intake valve at an engine crank angle between 660 and 705 degrees during a second time period to draw air into the combustion chamber, the second time period after the cold-start time period.
9 . The method of claim 8 , further comprising:
closing the intake valve at an engine crank angle between about 175 and about 255 degrees during a third time period following the second time period.
10 . The method of claim 1 , wherein the volume of the single, alcohol-based fuel has a cetane number of less than about 10.
11 . The method of claim 10 , wherein the volume of the single, alcohol-based fuel has a cetane number of less than about 5.
12 . The method of claim 1 , wherein:
the compression ignition engine further comprises at least one of a turbocharger, a supercharger, or a turbo-compounding device, and
the method further comprises:
passing the volume of air through the at least one of the turbocharger, the supercharger, or the turbo-compounding device prior to drawing the volume of air into the combustion chamber.
13 . The method of claim 12 further comprising:
restricting at least a portion of a volume of exhaust from exiting the combustion chamber.
14 . A method of operating a compression ignition engine during a cold-start time period, the compression ignition engine defining a combustion chamber, the method comprising:
drawing a volume of air into the combustion chamber during the cold-start time period in which the volume of air has a mass-average temperature of less than about 50° C. at the moment the volume of air enters the combustion chamber;
compressing the volume of air in the combustion chamber at a compression ratio of between about 15 and about 25;
transferring, via a single fuel injection event, a volume of a single alcohol fuel into the combustion chamber, the volume of the single alcohol fuel and the volume of air forming an air-fuel mix; and
using an ignition-assist device to combust all of the volume of the single alcohol fuel.
15 . The method of claim 14 , wherein the ignition-assist device is located in a bowl region of the combustion chamber.
16 . The method of claim 14 , wherein the ignition-assist device includes at least one of a glow plug, a spark plug, a plasma ignition device, or a cartridge heater.
17 . The method of claim 14 , wherein at least about 20% of the volume of the single alcohol fuel is pre-mixed with the volume of air immediately prior to ignition.
18 . The method of claim 14 , wherein:
the compression ignition engine further includes an intake valve, and
the method further includes:
prior to combusting all of the volume of the single alcohol fuel, closing the intake valve.
19 . The method of claim 18 , wherein:
closing the intake valve is at an engine crank angle between 175 and 255 degrees, and
the method further comprises:
opening the intake valve at an engine crank angle between 660 and 705 degrees during a second time period after the cold-start time period to draw air into the combustion chamber.
20 . The method of claim 19 , further comprising:
closing the intake valve at an engine crank angle between about 175 and about 255 degrees during a third time period after the second time period.
21 . The method of claim 14 , wherein:
the compression ignition engine further comprises at least one of a turbocharger, a supercharger, or a turbo-compounding device, and
the method further comprises:
passing the volume of air through the at least one of the turbocharger, the supercharger, or the turbo-compounding device prior to drawing the volume of air into the combustion chamber.
22 . A method of operating a compression ignition engine during a cold-start time period, the compression ignition engine defining a combustion chamber, a piston disposed in and configured to move in the combustion chamber, the method comprising:
drawing a volume of air into the combustion chamber during the cold-start time period, the cold-start time period designated as a time period in which the volume of air has a mass-average temperature of less than about 50° C. at the moment the volume of air passes through an intake valve;
compressing, via the piston, the volume of air at a compression ratio of between about 15 and about 25;
transferring a volume of a single alcohol fuel having a cetane number of less than about 20 into the combustion chamber, the volume of the single alcohol fuel and the volume of air forming an air-fuel mix; and
igniting, via an ignition-assist device, all of the volume of the single alcohol fuel.
23 . The method of claim 22 , wherein the ignition-assist device is located in a bowl region of the combustion chamber.
24 . The method of claim 22 , wherein the ignition-assist device includes at least one of a glow plug, a spark plug, a plasma ignition device, or a cartridge heater.
25 . The method of claim 22 , wherein at least about 20% of the volume of the single alcohol fuel is pre-mixed with the volume of air immediately prior to ignition.
26 . The method of claim 22 , further comprising:
opening the intake valve at an engine crank angle between 660 and 705 degrees during a second time period after the cold-start time period to draw air into the combustion chamber.
27 . The method of claim 26 , further comprising:
closing the intake valve at an engine crank angle between about 175 and about 255 degrees during a third time period after the second time period.
28 . The method of claim 22 , wherein the single alcohol fuel has a cetane number of less than about 10.
29 . The method of claim 22 , wherein:
the compression ignition engine further comprises at least one of a turbocharger, a supercharger, or a turbo-compounding device, and
the method further comprises:
passing the volume of air through the at least one of the turbocharger, the supercharger, or the turbo-compounding device prior to drawing the volume of air into the combustion chamber.
30 . The method of claim 29 , further comprising:
restricting at least a portion of a volume of exhaust from exiting the combustion chamber.