Investigation of the combined use of diesel and CNG fuels on an HCCI engine using Response Surface Methodology (RSM)

In this study, the effects of the combined use of diesel and Compressed Natural Gas (CNG) fuels on the performance, combustion and emissions were experimentally and statistically investigated in a Homogeneous Charged Compression Ignition (HCCI) engine. Diesel and CNG fuels were used at different ratios between 0% and 80% by mass, and tests were conducted at different engine loads. The experimental procedure was designed using the Response Surface Methodology (RSM) composite central design method. The experimental data were analyzed using MATLAB and entered into the RSM. In order to determine the response parameters predictably, model equations were created, counter graphs were drawn and optimization was carried out. Engine load and CNG ratio, which are the optimum input parameters, were determined as 68.36% and 2.864%, respectively. The response parameter values were obtained as 4.487 bar for Indicated Mean Effective Pressure (IMEP), 39.3% for Indicated Thermal Efficiency (ITE), 255.5 g/kWh for Brake Specific Fuel Consumption (BSFC), 3.343% for Coefficient of Variation of Indicated Mean Effective Pressure (COVIMEP), 0.247% for CO, 191.566 ppm for HC, 579.538 ppm for NOx and 1.393 m-1 for smoke. This study, in which a combined diesel and CNG fueled engine operating in HCCI combustion mode is examined with experimental and statistical methods, will fill an important gap in the literature and provide researchers with a new perspective. © 2025 Sharif University of Technology.