Prediction of Temperatures on Pistons with Cooling Gallery in Diesel Engines using CFD Tool 2003-01-0986
Thermal loading in pistons of diesel engines installed on commercial vehicles, such as trucks and buses, has been increased dramatically in recent years due to applications of technologies to meet low emission and high power requirements. It causes serious concerns on the reliability and durability of engines and engine components. Control of piston temperatures has become one of the determining factors in a successful engine design. Therefore, design optimization of pistons and cooling oil flow in the lubrication system at the concept design stage has become more and more important. For pistons under higher thermal loading, the adoption of a cooling gallery is a common practice. In this case, the heat flow into the cooling gallery has a significant influence on piston temperatures, similar as that caused by the heat flows from combustion. It is difficult to predict piston temperatures with sufficient accuracy in the past because the heat transfer coefficient in the cooling gallery can not be predicted accurately. To calculate the coefficient of heat transfer for the cooling gallery using CFD tool, a new approach for piston temperature prediction has been developed. Compared with conventional temperature estimation largely based on past experience, this approach improves prediction results and enables an optimum cooling condition to be successfully obtained at the design stage.