Downspeeding the Diesel Engine – A Performance Analysis

Abstract

Owing to the high overall efficiency, truck manufacturers stick to diesel engines particularly in the case of long haul heavy duty trucks. In the ever increasing demand to increase the efficiency and to decrease the emission levels of the internal combustion engines an attempt is made in this thesis work to increase the fuel efficiency. There are many ways to increase the fuel efficiency like varying compression ratio, downsizing, down speeding, advanced combustion concepts (PCCI, HCCI) etc. but each of the mentioned method comes with challenges. In this thesis work an effort is made to study downspeeding by means of extensive simulation using commercial software GT-Power. By down speeding, the engine is made to run at low speeds and with high torques. For the same power the engine is operated at higher specific load (BMEP) which results in higher efficiency and reduced fuel consumption (BSFC). The reasons for increased fuel efficiency are reduced engine friction due to low piston speeds, reduced relative heat transfer and increased thermodynamic efficiency. Since this is a conceptual study and experiments may require a new engine design altogether, scope of the study is limited to simulation results and no validation is done.