Optimization And Control Of Combustion Modes On Hybrid Engine

Key technical trends to save energy and reduce emission of internal combustion engines are the advanced combustion modes with new fuel and the hybrid powertrain technology.The Hybrid Engine system integrates new fuel,advanced combustion modes and the hybrid powetrain and structs a comprehensive technical system for future automotive powertrain systems.This dissertation utilizes technologies of the Hybrid Engine system to control and optimize the advanced combustion modes with low octane number fuel.Combustion modes under typical operation conditions are studied through engine experiments,while new engine assisting measures are deployed to improve combustion characteristics and to expand the operating range of advanced combustion modes.A low-pressure exhaust gas recirculation(EGR)loop,an in-cylinder heating system and an ISG motor are developed and installed on the original diesel engine platform.The closed-loop control algorithm of EGR rate is realized based on the self-developed engine control system.The in-cylinder heating control algorithm based on the pressure sensor glow-plug(PSG)is developed.And the motor active torque compensation algorithm is developed and validated.Low-octane fuel G70D30 and G50D50 are prepared by mixing standard gasoline and diesel.Partially premixed compression ignition(PPCI)and late-injection low temperature combustion(L-LTC)are realized by adjusting injection parameters and EGR rates.In order to avoid the deterioration of pollutant emissions at high load conditions under PPCI,L-LTC is used to expand the upper load limit of clean combustion.And a multi-mode combustion strategy is proposed as the optimized option for the whole load range.In order to improve combustion instability of PPCI at low load conditions,the incylinder heating system is utilized.And a new combustion mode is realized and named as glow-plug Assisted Compression Ignition(GA-CI).Under GA-CI,the combustion efficiency and stability are effectively improved,while the emissions of particulate matters,hydrocarbons and carbon monoxide are reduced.For the ignition problem of new fuel under cold conditions,the motor active torque compensation strategy is realized on the ISG parallel hybrid system and been used as an assisting method to improve the combustion process under cold conditions.The cylinder-to-cylinder variation is another critical issue.Previous combustion states detecting method with one in-cylinder pressure sensor in each cylinder is costly,while the traditional model-based combustion state prediction method requires complicated algorithm and has poor precision.In this paper,a novel combustion state parameters estimation method combining one in-cylinder pressure sensor and the combustion model is proposed and validated.The method could reduce both system setup cost and algorithm complexity.Furthermore,motor active torque compensation strategy and in-cylinder heating control strategy are used to decrease the cylinder-to-cylinder variation.