Optimization of operating conditions in a homogeneous charge compression ignition engine with variable compression ratio

In this study, the performance and exhaust emissions of homogeneous charge compression ignition engine fueled by gasoline fuel were modeled by using the response surface method. The effect of independent variables—compression ratio, engine speed inlet air temperature, lambda value, and research octane number value—on responses such as indicated mean effective pressure, indicated thermal efficiency, maximum pressure rise rate, specific fuel consumption, cyclic differences was studied together; unburned hydrocarbons, carbon monoxide, and nitrogen oxide are predicted by multi-regression. The desirability function was used to define an optimum combination of engine operating conditions. High desirability of 77% was achieved at the compression ratio of 12, intake air temperature of 333 K, lambda value of 1.8, engine speed of 935 rpm, and RON40. This homogeneous charge compression ignition engine operating condition was suggested as the optimum independent variables. At this point, 5.08 of indicated mean effective pressure, 35% of indicated thermal efficiency, 243.28 g/kWh of specific fuel consumption, 4.43 bar/CA of maximum pressure rise rate, and 3% of COVimep were achieved as responses. Additionally, the optimum values of engine emissions were found to be 355.586 ppm for unburned hydrocarbons, 3% for carbon monoxide, and 0 ppm for nitrogen oxide. This study showed that changes in performance and exhaust emissions of a homogeneous charge compression ignition engine could be successfully predicted using the response surface method. This study, which was carried out with the RSM technique, reduced the hundreds of data points needed, and all variables could be examined with only 60 data points.