HCCI combustion: Analysis and experiments

Homogeneous charge compression ignition (HCCI) is a new combustion technology that may develop as an alternative to diesel engines with high efficiency and low NO _x and particulate matter emissions. This paper describes the HCCI research activities being currently pursued at Lawrence Livermore National Laboratory and at the University of California Berkeley. Current activities include analysis as well as experimental work. On analysis, we have developed two powerful tools: a single zone model and a multi-zone model. The single zone model has proven very successful in predicting start of combustion and providing reasonable estimates for peak cylinder pressure, indicated efficiency and NO _x emissions. This model is being applied to develop detailed engine performance maps and control strategies, and to analyze the problem of engine startability. The multi-zone model is capable of very accurate predictions of the combustion process, including HC and CO emissions. The multi-zone model has applicability to the optimization of combustion chamber geometry and operating conditions to achieve controlled combustion at high efficiency and low emissions. On experimental work, we have done a thorough evaluation of operating conditions in a 4-cylinder Volkswagen TDI engine. The engine has been operated over a wide range of conditions by adjusting the intake temperature and the fuel flow rate. Satisfactory operation has been obtained over a wide range of operating conditions. Cylinder-to-cylinder variations play an important role in limiting maximum power, and should be controlled to achieve satisfactory performance.