A Study On Diesel HCCI Combustion Based On The Compound Control Of Multi-pulse Injection

Homogeneous Charge Combustion Ignition (HCCI) is an attractive advanced combustion process that offers the potential for substantial reductions in both NOx and PM, while providing high efficiencies. Although the potential benefits of HCCI combustion are great, there are still many problems that unsolved. Especially for the diesel-fueled HCCI engine, there are three aspects of difficulties, that is forming of a premixed homogeneous charge, controlling of the auto-ignition process and expanding of engine loads. In this paper, the MULINBUMP-HCCI compound combustion technology was developed based on the combustion strategies of combination of controlled premixed charge compression ignition (CPCCI) and lean diffusion combustion (LDC), which was presented by our research team. The MULINBUMP-HCCI compound combustion technology is an abbreviated form of MULti-INjection and BUMP combustion chamber for Diesel HCCI combustion. Through the Multi-pulse injection technology, the mixing process of the pre-injected fuel can be controlled. The results of engine experiments and CFD computer simulation show that by setting the parameters of multi-pulse injection the stratified temperature and concentration distribution can be controlled, especially, by setting the timing of multi-injection. Sequentially, the phase and rate of heat release can be controlled, and then the CPCCI combustion is achieved. In the CPCCI mode, the NOx and smoke emissions are extremely low, but the HC and CO emissions are high. As a result, combustion efficiency is deteriorated. In the compound combustion mode, the main injection fuel triggers the lean premixed charge and the combustion efficiency is improved. In this paper, the comparative study of various combustion modes was carried out. The dispersed heat release of a MULINBUMP working cycle reveals that its thermo-efficiency is proximately as high as a conventional diesel cycle and the emissions of NOx and soot are simultaneously reduced. The dispersed heat release mode has the best combustion efficiency in comparison with other modes of heat release.