A CFD Investigation of Heat Transfer in a Diesel Fueled PPC Engine Applying Design of Experiments

Due to the nature of the engine cycle, heat transfer has a significant role in the estimation of engine efficiency. The effects are quite well known in the classic combustion concepts, compression ignition (CI) and spark ignition (SI) combustion. But for the newer, low temperature combustion (LTC) concepts, these effects are not that well known. In this paper, a commercial computational fluid dynamics (CFD) code, AVL FIRE, is used to evaluate engine performance and emissions for different thermal settings in the engine cylinder of a LTC engine. Design of experiments (DoE) methodology is applied to model the response variables and quantify the effects from different model variables on the response. The results show that, within the parameter space chosen for this work, the strongest effect on the in-cylinder heat transfer and engine performance comes from the temperature and pressure at inlet valve closing, as well as the piston wall temperature. The values giving the best combination of low heat loss and high performance are high temperature walls along with cold inflowing air and high boost pressure.