Simulation of intake and exhaust valve timing on internal combustion engine

Abstract

Internal combustion engine in automotive industry is widely researched to increase its efficiency and power output. Valve system in modern internal combustion engine controls the opening and closing timing of intake and exhaust stroke. Its duration affects the performance of the engine at both power output and fuel efficiency. Therefore, this study discusses about the Miller cycle concept that alters the duration of both intake and exhaust valve opening and closing characteristics. The study focuses mainly on finding the optimum timing characteristics on Proton Iriz gasoline engine. A 1-dimensional model has been built using a commercial software called GT-POWER for engine simulation purpose. The engine is then calibrated with the simulation model. The optimization was run in this software to find the best optimum timing of intake and exhaust valve for two categories which are targeting performance and fuel consumption. The results show positive trends in the BSFC results with the maximum percentage difference of 26.27% at 6,250 rpm. The average percentage difference in the BSFC results is 14.12%. For targeting performance, the overall results show an increasing trend in the brake torque curves with maximum percentage difference is 9.83%. The average percentage difference in brake torque is found to be 3.12%. Therefore, this paper concludes that Miller cycle implementation gives minimal performance increment. The targeting performance and fuel consumption optimization can also be implemented for changing mode of driving. However, the increase compression ratio would also give adverse effects on engine performance and endurance. The Miller cycle is also more suitable to be implemented on force induction system.