A Study on the Engine Heat Transfer Characteristic through Stroke-to-Bore Ratio during Combustion Phase

Abstract

The internal combustion engine (ICE) converts fuels chemical energy into a usable form. However, it only converts one-third of the total chemical energy. The rest of energy is wasted in the form of heat transfer to cylinder walls and exhaust losses. Engine efficiency can be enhanced by reducing the heat transfer from gas to cylinder walls. Engine efficiency has received attention from academia and the vehicle industry in recent years as the regulations on CO2 emission have strengthened. An improvement in engine efficiency means the ICE can convert more energy from the same amount of the fuel and less CO2 emission. To reduce the in-cylinder heat transfer and to improve the engine fuel conversion efficiency, the concept of changing the stroke-to-bore ratio was studied. A GT-Power based 1D engine model to check the in-cylinder heat transfer characteristic was developed and evaluated. Engine geometry was assumed as a simple cylinder and Woschni correlation was adopted to predict the convection heat transfer coefficient. A comparison of the convection heat transfer coefficient with 3D simulation was also performed to verify the accuracy of Woschni correlation.