초록 ▼

A strategy to cold-start an opposed-piston engine includes, before injecting fuel, preventing air flow through the engine while cranking the engine to heat air retained in the engine, followed by controlling mass air flow through and fuel injection into a cylinder of the engine according to cold-sta

A strategy to cold-start an opposed-piston engine includes, before injecting fuel, preventing air flow through the engine while cranking the engine to heat air retained in the engine, followed by controlling mass air flow through and fuel injection into a cylinder of the engine according to cold-start schedules so as to create and preserve heat for stable engine firing and transition to an idling state of operation.

대표청구항 ▼

1. A method of operating an opposed-piston engine with one or more cylinders, in which each cylinder has a piston-controlled exhaust port coupled to an exhaust subsystem and a piston-controlled intake port coupled to a charge air subsystem, a pair of pistons disposed for opposing movement in a bore

1. A method of operating an opposed-piston engine with one or more cylinders, in which each cylinder has a piston-controlled exhaust port coupled to an exhaust subsystem and a piston-controlled intake port coupled to a charge air subsystem, a pair of pistons disposed for opposing movement in a bore of the cylinder, and one or more fuel injectors disposed for injecting fuel into the cylinder, the method comprising: receiving a signal to start the engine;detecting a cold-start condition, followed by:before fuel is injected, limiting charge air flow through the cylinder and heating air retained in the cylinder by cranking the engine;in which limiting charge air flow through the cylinder includes either the step of reducing or blocking gas flow through the exhaust subsystem and the charge air subsystem, or the steps of reducing or blocking gas flow through the exhaust subsystem and providing charge air to the cylinder at a target boost pressure; and then,injecting fuel into a combustion space between opposing end surfaces of pistons in the cylinder according to a cold-start schedule;providing a progressively increasing flow of charge air through the cylinder until an engine idling state is reached; and,injecting fuel into the combustion space according to an idling schedule. 2. The method of claim 1, in which the charge air subsystem includes a supercharger having an input and an output, an intake manifold coupled to the output of the supercharger and in fluid communication with the intake port, and a recirculation path coupling the output of the supercharger to the input of the supercharger, and reducing or blocking gas flow through the charge air subsystem includes increasing charge air flow through the recirculation path. 3. The method of claim 2, in which the charge air subsystem further includes a cooling device coupled in series between the output of the supercharger and an input to the recirculation path, further including, while cranking the engine, bypassing the cooling device by coupling the output of the supercharger directly to the input of the recirculation path until the idling state is reached. 4. The method of claim 1, in which the exhaust subsystem includes a backpressure valve for adjusting gas flow through the exhaust subsystem, and reducing or blocking gas flow through the exhaust subsystem includes closing the backpressure valve. 5. The method of claim 4, in which the charge air subsystem includes a supercharger having an input and an output, an intake manifold coupled to the output of the supercharger and in fluid communication with the intake port, and a recirculation path coupling the output of the supercharger to the input of the supercharger, and reducing or blocking gas flow through the charge air subsystem includes increasing charge air flow through the recirculation path. 6. The method of claim 5, in which providing an increasing flow of charge air through the cylinder includes progressively opening the backpressure valve and progressively reducing charge air flow through the recirculation path, according to a cold start schedule until the idling state is reached. 7. The method of claim 6, in which the engine further includes an EGR channel coupling the exhaust subsystem to the charge air subsystem, and the step of receiving the start signal is preceded by: receiving an engine shut-down signal, followed by:pre-conditioning air includes blocking the flow of exhaust gas through the EGR channel, followed by opening the exhaust subsystem and the charge air subsystem. 8. The method of claim 7, further comprising blocking circulation of liquid coolant to the cylinders or the pistons until the engine idling state is reached. 9. A cold-start system for an opposed-piston engine with one or more cylinders, in which each cylinder has a piston-controlled exhaust port coupled to an exhaust subsystem and a piston-controlled intake port coupled to a charge air subsystem, a pair of pistons disposed for opposing movement in a bore of the cylinder, and one or more fuel injectors disposed for injecting fuel into the cylinder, comprising: a starter motor operable to crank the engine during start-up;a backpressure valve in the exhaust subsystem;the charge air subsystem including a supercharger having an input and an output, an intake manifold coupled to the output of the supercharger and in fluid communication with the intake port, and a recirculation path coupling the output of the supercharger to the input of the supercharger; and,an engine control mechanization operable to detect a cold-start condition and to operate the starter motor, the backpressure valve, the recirculation path, and the fuel injectors in response to the cold-start condition by: closing the backpressure valve and opening the recirculation path to reduce or block charge air flow through the cylinder and cranking the engine to heat air by compression in the cylinder before fuel is injected, followed by:causing the fuel injectors to inject fuel into a combustion space defined between opposing end surfaces of pistons in the cylinder according to a cold-start schedule, and progressively opening the backpressure valve and closing the recirculation path to increase the flow of charge air through the cylinder until an engine idling state is reached. 10. The cold-start system of claim 9, further including an EGR channel coupling the exhaust subsystem to the charge air subsystem, and wherein the engine control mechanization is operable to limit the flow of exhaust gas through the EGR channel until the idling state is reached. 11. The cold-start system of claim 10, further including one or more of a variable geometry turbine in the exhaust subsystem, a charge air cooler bypass path in the charge air subsystem, and an EGR cooler bypass path in the EGR channel, and wherein the control mechanization is further operable to perform one or more of: configuring the variable geometry turbine to limit the flow of gas until the idling state is reached;enabling charge air flow through the charge air cooler bypass path until the idling state is reached; and,enabling exhaust flow through the EGR cooler bypass path until the idling state is reached. 12. A method of operating an opposed-piston engine with an exhaust subsystem, a charge air subsystem, an EGR channel coupling the exhaust subsystem to the charge air subsystem, and one or more cylinders, in which each cylinder has a piston-controlled exhaust port coupled to the exhaust subsystem and a piston-controlled intake port coupled to the charge air subsystem, a pair of pistons disposed for opposing movement in a bore of the cylinder, and one or more fuel injectors disposed for injecting fuel into the cylinder, the method comprising: receiving an engine start signal;detecting a cold-start condition and responding to the cold-start condition by:blocking the flow of exhaust gas through the EGR channel; and then,before fuel is injected, limiting charge air flow through a cylinder and heating conditioned air in the cylinder by cranking the engine, followed by:ceasing cranking while injecting a cold-start sequence of fuel pulses into the cylinder and increasing the flow of charge air through the cylinder, until an engine idling state is reached; and,injecting an idling sequence of fuel pulses into the cylinder. 13. The method of claim 12, further including blocking circulation of liquid coolant to the cylinders or the pistons until the engine idling state is reached. 14. The method of claim 12, in which limiting charge air flow through the cylinders includes the step of blocking exhaust flow through the exhaust subsystem, and either the step of blocking charge air flow through the charge air subsystem, or the step of causing charge air to flow to the cylinder at a target boost pressure. 15. The method of claim 14, in which the charge air subsystem includes a supercharger having an input and an output, an intake manifold coupled to the output of the supercharger and in fluid communication with the intake port, and a recirculation path coupling the output of the supercharger to the input of the supercharger, and blocking charge air flow through the charge air subsystem includes increasing charge air flow through the recirculation path. 16. The method of claim 15, in which the exhaust subsystem includes a backpressure valve for adjusting gas flow through the exhaust subsystem, and blocking gas flow through the exhaust subsystem includes closing the backpressure valve. 17. The method of claim 16, in which providing an increasing flow of charge air through the cylinder includes progressively opening the backpressure valve and progressively reducing charge air flow through the recirculation path according to a cold-start schedule until the idling state is reached. 18. A method of operating an opposed-piston engine with an exhaust subsystem, a charge air subsystem, an EGR channel coupling the exhaust subsystem to the charge air subsystem, and one or more cylinders, in which each cylinder has a piston-controlled exhaust port coupled to the exhaust subsystem and a piston-controlled intake port coupled to the charge air subsystem, a pair of pistons disposed for opposing movement in a bore of the cylinder, and one or more fuel injectors disposed for injecting fuel into the cylinder, the method comprising: during shut-down of the engine, closing the EGR channel, and then ceasing fuel injection into the cylinder and flushing exhaust products from the cylinder; followed by,detecting a cold-start condition in response to an engine start signal and responding to the cold-start condition by:closing the EGR channel; followed by,before fuel is injected, closing the exhaust subsystem and providing pressurized charge air to a cylinder and heating the pressurized charge air in the cylinder by cranking the engine, followed by:injecting a cold-start sequence of fuel pulses into the cylinder while progressively increasing the flow of exhaust gas through the exhaust subsystem and progressively increasing the flow of charge air to the cylinder, until an engine idling state is reached; and then,injecting an idling sequence of fuel pulses into the cylinder. 19. A method of operating an opposed-piston engine with one or more cylinders, in which each cylinder has a piston-controlled exhaust port coupled to an exhaust subsystem and a piston-controlled intake port coupled to a charge air subsystem, a pair of pistons disposed for opposing movement in a bore of the cylinder, and one or more fuel injectors disposed for injecting fuel into the cylinder, in which the engine further includes an EGR channel coupling the exhaust subsystem to the charge air subsystem, the method comprising: receiving an engine shut-down signal;preconditioning air retained in the engine by blocking the flow of exhaust gas through the EGR channel, followed by opening the exhaust subsystem and the charge air subsystem; and then,receiving a signal to start the engine;detecting a cold-start condition, followed by:before fuel is injected, limiting charge air flow through the cylinder and heating air retained in the cylinder by cranking the engine; and then,injecting fuel into a combustion space between opposing end surfaces of pistons in the cylinder according to a cold-start schedule;providing a progressively increasing flow of charge air through the cylinder until an engine idling state is reached; and,injecting fuel into the combustion space according to an idling schedule. 20. A method of operating an opposed-piston engine with one or more cylinders, in which each cylinder has a piston-controlled exhaust port coupled to an exhaust subsystem and a piston-controlled intake port coupled to a charge air subsystem, a pair of pistons disposed for opposing movement in a bore of the cylinder, and one or more fuel injectors disposed for injecting fuel into the cylinder, the method comprising: receiving a signal to start the engine;detecting a cold-start condition, followed by:before fuel is injected, limiting charge air flow through the cylinder and heating air retained in the cylinder by cranking the engine; and then,injecting fuel into a combustion space between opposing end surfaces of pistons in the cylinder according to a cold-start schedule;providing a progressively increasing flow of charge air through the cylinder and blocking circulation of liquid coolant to the cylinders or the pistons until an engine idling state is reached; and,injecting fuel into the combustion space according to an idling schedule.