The aim of this study is to analyze the effect of changes in the surface area to volume ratio of the piston crown on the performance and emissions of the HCCI engine with a mixture of methane and diesel fuel under different conditions and samples I, II, III, IV with a compression ratio of 18:1 and acceptable validation with the behavior of the TD43 laboratory engine have been investigated.

The results show that by reducing the surface area to volume ratio of the piston crown, the temperature inside the cylinder increases significantly. Research shows that in model I, which has the highest surface area to volume ratio, the temperature inside the cylinder is about 1800K, while in model IV, which has the lowest surface area to volume ratio, the temperature inside the cylinder is about 2200K. Therefore, for a 7-unit increase in the surface area to volume ratio, the temperature inside the cylinder increases by 400K, which is a significant amount. Such a temperature difference can cause a sharp increase in the production of hazardous pollutants.

The changes in the production of NOX pollutants in each of the simulated engines can be said to have a direct effect on increasing the production of NOX pollutants in the engine by reducing the surface area to volume ratio of the piston crown. It can also be stated that the production of NOX pollutants in model I is almost zero, which is a major advantage for this engine.