A study on the effect of operating condition and piston head geometry on engine performance of converted CNG engine

Abstract

      Natural gas has known as a potential alternative fuel of internal combustion engines because of its advantages such as the research octane number is higher than that of gasoline, the low heat value is higher in comparision with gasoline and diesel, the safety in use. This paper presents a study on the influence of working conditions and the shape of the piston top on the performance of a natural gas engine. The obtained results show that it is necessary to reduce the compression ratio to  = 10 for the engine to work safely in the speed range n = 1000 - 2200 rpm when converting Diesel engines into natural gas engines. However, in order to improve the thermal efficiency of the post-conversion engine, it is necessary to change the shape of the piston top. The influence of the piston top shape on the squish velocity is very large, so that the turbulent kinetic energy of the gas at the end of the compression is greatly increased. As a result, torque increases compared to flat top pistons, CO emissions tend to decrease but NOx emissions increase