Methodology for the estimation of head inner surface temperature in an air-cooled engine

This paper proposes a methodology for the estimation of the mean temperature of the head inner surface in an air-cooled internal combustion engine. Knowledge of this temperature is necessary to determine the heat flux from the combustion chamber to the head wall. Along with the heat transfer coefficient from combustion gases to engine head, this temperature also allows the calculation of head engine heat losses, which are almost 50% of the whole engine heat losses. The temperature is relatively easy to determine for water-cooled engines but this is not in case of air-cooled engines. The methodology described here combines numerical simulations based on FEM models and experimental procedures based on the use of thermocouples and infrared thermography. The proposed methodology has been successfully applied to an air-cooled four-stroke direct-injection diesel engine and it allows the estimation of the head mean inner surface temperature and head-cooling air heat transfer coefficient.