Realization method of cai combustion based on engine controllable exhaust back pressure valve

Abstract

The invention relates to an engine-based method for realizing CAI (Controlled Auto Ignition) combustion through a controllable exhaust back-pressure valve. 50 DEG CA VVT (Variable Valve Timing) is adopted to fully meet the internal residual exhaust gas conditions required by CAI combustion, at the same time, the exhaust back-pressure of an engine is increased, and the internal residual exhaust gas is forcedly retained in a cylinder to directly control the quantity of internal residual exhaust gas so as to control the CAI combustion load; and mixed gas in the cylinder is heated through re-suction of exhaust gas to increase the temperature of the mixed gas. The direct benefit of the increase of compression ratio lies in the improvement of fuel oil economy of the engine, meanwhile, with the adoption of high compression ratio, the temperature of mixed combustible gas before top dead center of compression can be further increased so as to be favorable for the realization of CAI combustion. In addition, by utilizing the EGR (Exhaust Gas Recirculation) strategy, the quantity of discharged NOX in the exhaust gas can also be reduced.

Description

technical field [0001] The invention belongs to the technical field of engines, and specifically relates to an engine-based controllable exhaust back pressure by changing the VVT ​​change angle, exhaust back pressure and compression ratio to control the thermal state of the mixture in the engine cylinder so as to realize CAI combustion. A method for realizing valve CAI combustion. Background technique [0002] Controlled Auto Ignition (CAI) of gasoline engine is a new combustion method through the mixture of compressed air and fuel (including recirculated exhaust gas) until it ignites. Its essence is the combination of the two combustion methods of diesel engine and gasoline engine. The improvement of the method has high theoretical research value and is a research hotspot in recent years, and it is also an increasingly mature combustion method. [0003] At present, the main methods to achieve CAI combustion at home and abroad are: direct intake heating, using high compress...

AI Technical Summary

Problems solved by technology

[0005] For the control strategy of internal exhaust gas recirculation (i-EGR), the VVT ​​of the existing direct injection engine technology platform of Changan Automobile Company adopts the valve control strategy of the positive overlap angle of the intake and exhaust valves, but the maximum internal EGR rate is 29%. It cannot meet the minimum internal EGR rate requirement of about 40% required to realize CAI combustion, and cannot realize CAI combustion

In addition, for the ICCS engine, by increasing the overlap angle of the intake and exhaust valves, although a certain amount of internal residual exhaust gas can be obtained, but limited by the cam profile and VVT change angle (30oCA VVT phase adjustment range), simply Depending on the change of intake and exhaust valve phases, a sufficient proportion of internal residual exhaust gas cannot be obtained, so the conditions required for CAI combustion cannot be achieved

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