Simulation of piston and ring friction at the motoring condition and investigation effect of combustion and clearance between the piston and cylinder

One of the most important matters that have a great effect on engine efficiency is engine internal friction. In this article the friction model of piston-cylinder mechanism has been numerically simulated for a 4 cylinders spark ignition engine. The results were validated and the test results have been compared with simulation results. Consequently, the effect of combustion pressure and temperature, on the friction of ring and piston has been studied. Also, the impact of piston clearance on engine friction has been numerically investigated. The simulation results showed that at speeds of less than 3000 rpm varying the piston-liner clearance cannot significantly change the engine friction. But increasing clearance from the 30 to 80 microns at 6,000 rpm caused about 20% reduction in friction. It was also seen that the consideration of combustion pressure and temperature leads to a considerable increase in the engine friction.