Work vehicle compression ignition power system having thermally stratified engine combustion chambers
A power system includes an intake arrangement and a compression ignition engine including piston-cylinder sets. Each piston-cylinder set includes: a cylinder; a piston positioned within the cylinder to form a combustion chamber in between; an intake valve configured to open and close the intake port; an exhaust valve configured to open and close the exhaust port; and a fuel injector. During an exhaust stroke, the exhaust valve is opened to enable exhaust gas to flow out; during an initial portion of an intake stroke, the intake valve is opened to enable the intake air to flow into the combustion chamber, and during a further portion of the intake stroke, the intake valve is closed and the exhaust valve is opened to enable a portion of the exhaust gas to flow back into the combustion chamber in order to create thermally stratified layers of intake gas and exhaust gas.
1 . An engine control system for a compression ignition engine including a plurality of piston-cylinder sets with an intake port and an intake valve, an exhaust port and an exhaust valve, and a piston positioned at least partially within a cylinder to form a combustion chamber in communication with the intake port and the exhaust port, the engine control system having processing architecture executing programmed instructions to selectively command the intake valve and the exhaust valve such that:
during an exhaust stroke of the piston, the exhaust valve is opened to enable exhaust gas to flow out of the combustion chamber;
during an initial portion of an intake stroke of the piston, the intake valve is opened to enable intake air to flow into the combustion chamber; and
during a further portion of the intake stroke of the piston, the intake valve is closed and the exhaust valve is opened to enable a portion of the exhaust gas to flow back into the combustion chamber to create thermally stratified layers of intake gas and exhaust gas within the combustion chamber.
2 . The engine control system of claim 1 , wherein the compression ignition engine is configured to operate with a low cetane fuel.
3 . The engine control system of claim 2 , wherein the compression ignition engine is configured to operate with fuel having a cetane value of less than 40.
4 . The engine control system of claim 1 , wherein the thermally stratified layers of intake gas and exhaust gas include a layer with a temperature of at least 800° C.
5 . The engine control system of claim 1 , wherein the processing architecture executes programmed instructions to manipulate a pressure difference between an exhaust side of the compression ignition engine and an intake side of the compression ignition engine to increase an impact of the portion of the exhaust gas flowing back into the combustion chamber during the further portion of the intake stroke.
6 . The engine control system of claim 1 , wherein during the initial portion of the intake stroke, the intake valve is commanded to open to admit intake air through the intake port into the combustion chamber such that gas within the combustion chamber is at a first temperature.
7 . The engine control system of claim 6 , wherein during the further portion of the intake stroke, one of the stratified layers at a top end of the combustion chamber adjacent the exhaust port is at a second temperature higher than the first temperature.
8 . The engine control system of claim 7 , wherein the further portion of the intake stroke is an end portion of the intake stroke at which the piston is at bottom dead center.
9 . The engine control system of claim 7 , wherein during a portion of a compression stroke, the gas at the first temperature is increased to a third temperature higher than the second temperature and the gas in the stratified layer at the top end of the combustion chamber is increased to a fourth temperature higher than the third temperature.
10 . The engine control system of claim 9 , wherein during an end portion of a compression stroke, the gases are at higher temperatures than their respective third and fourth temperatures.
11 . The engine control system of claim 10 , wherein at the end portion of the compression stroke the piston is at top dead center.
12 . A work vehicle, comprising:
a chassis;
a compression ignition engine supported by the chassis and including a plurality of piston-cylinder sets with an intake port and intake valve and with an exhaust port an exhaust valve and a piston positioned at least partially within a cylinder to form a combustion chamber in communication with the intake port and the exhaust port; and
an engine control system for the compression ignition engine, the engine control system having processing architecture executing programmed instructions to selectively command the intake valve and the exhaust valve such that:
during an exhaust stroke of the piston, the exhaust valve is opened to enable exhaust gas to flow out of the combustion chamber;
during an initial portion of an intake stroke of the piston, the intake valve is opened to enable intake air to flow into the combustion chamber; and
during a further portion of the intake stroke of the piston, the intake valve is closed and the exhaust valve is opened to enable a portion of the exhaust gas to flow back into the combustion chamber to create thermally stratified layers of intake gas and exhaust gas within the combustion chamber.
13 . The work vehicle of claim 12 , wherein the compression ignition engine is configured to operate with a fuel having a cetane value of less than 40 .
14 . The work vehicle of claim 12 , wherein the thermally stratified layers of intake gas and exhaust gas include a layer with a temperature of at least 800° C.
15 . The work vehicle of claim 12 , wherein the processing architecture executes programmed instructions to manipulate a pressure difference between an exhaust side of the compression ignition engine and an intake side of the compression ignition engine to increase an impact of the portion of the exhaust gas flowing back into the combustion chamber during the further portion of the intake stroke.
16 . The work vehicle of claim 12 , wherein during the initial portion of the intake stroke, the intake valve is commanded to open to admit intake air through the intake port into the combustion chamber such that gas within the combustion chamber is at a first temperature.
17 . The work vehicle of claim 16 , wherein during the further portion of the intake stroke, one of the stratified layers at a top end of the combustion chamber adjacent the exhaust port is at a second temperature higher than the first temperature.
18 . The work vehicle of claim 17 , wherein during a portion of a compression stroke, the gas at the first temperature is increased to a third temperature higher than the second temperature and the gas in the stratified layer at the top end of the combustion chamber is increased to a fourth temperature higher than the third temperature.
19 . The work vehicle of claim 18 , wherein during an end portion of a compression stroke, the gases are at higher temperatures than their respective third and fourth temperatures.
20 . The work vehicle of claim 19 , wherein the further portion of the intake stroke is an end portion of the intake stroke at which the piston is at bottom dead center; and
wherein at the end portion of the compression stroke the piston is at top dead center.