Preliminary investigations of the HCCI combustion system in a single cylinder research engine

This paper describes the results of the preliminary experimental research of the HCCI combustion system in a single cylinder research engine fuelled by means of natural gas containing 95% methane. In this research, influence of the initial temperature of the charge and mixture composition on the maximum combustion pressure, maximum speed of pressure growth, selfignition delay time, combustion time, maximum combustion temperature, heat release and combustion efficiency have been studied. The paper contains: description of the engine modification to adopt it for HCCI operation requirements, applied measurements equipment, selected results of the experimental research. The results shows that initial charge temperature and mixture composition (relative air/fuel ratio coefficient) have essential influence on the engine operating results. The experimental research has been conducted for the varied initial charge temperature from 140 centigrade up to 210 centigrade and for varied relative air/fuel ratio coefficient 1=1; 1=1.5; 1=1.7; 1=2. Maximum charge pressure, maximum speed of pressure growth selfignition delay time was rather unaffected on the initial charge temperature increase beyond 200 centigrade. Previous and current author's research works have indicated that extremely low emissions and high combustion efficiencies are possible to reach if homogeneous charge compression ignition is applied.