Control Of Diesel HCCI Combustion Using Internal-External EGR And Electric-Control Fuel Injection

Homogeneous Charge Compression Ignition (HCCI) has the potential to significantly reduce NO_x and smoke emissions simultaneously, while achieving high efficiency. The difficulties of homogeneous mixture preparation and combustion control are the key problems for diesel HCCI combustion. So, this paper presents a new diesel HCCI combustion system which is controlled by the internal and external EGR. In this system, fuel is injected in negative valve overlap (NVO) and the high-temperature residual gas benefits the fuel vaporization. All these can solve the problem of homogeneous mixture preparation. Then, the external cooled EGR is used to control the combustion phase and speed. Two-stage injection strategy which includes premix injection in NVO and auxiliary injection in the end of compression stroke is used to achieve high indicated efficiency and low emissions in middle-high load range. The control of combustion phase, speed and emissions of diesel HCCI combustion are studied, and the operation range enlarging problem is discussed.A program for diesel HCCI cycle simulation was developed, in order to understand the effects of NVO on the formation of homogeneous mixture and the combustion process. In this program, the HCCI combustion model coupled chemistry kinetics and experiential model. The effects of internal and external EGR on the combustion phase of diesel HCCI were studied.A diesel HCCI prototype engine was modified from a single-cylinder diesel engine. The variable valve timing (VVT) system, external EGR system and electrical-control common-rail multi-injection system were also developed. It was found that diesel HCCI can be achieved by fuel injection in NVO. In this HCCI combustion, the heat release showed low and high temperature stages, the NO_x emission was reduced about 90%~95% compared with the original diesel engine in the HCCI combustion operation range(below...