Comparison of heat flux sensors for internal combustion engines on two hot air gun test rigs and a test engine

Abstract

Paper presented at the 9th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Malta, 16-18 July, 2012.The heat transfer that occurs in the cylinder of internal combustion engines has a great influence on the efficiency, power output and emissions. Development of a model that is able to predict the heat transfer is needed in order to be able to use simulations for optimization of these three properties. Prior to developing a model, the heat transfer phenomenon has to be thoroughly investigated by performing measurements inside an engine. This allows for a detailed understanding of the process and for a validation of model predictions. In previous works, a commercially available thermopile has been used to measure the heat transfer in a hydrogen combustion engine. The use of this sensor as a heat flux sensor has already been positively evaluated in a previous paper. Its dimensions, however, limit its usability for engine measurements, as it is too large to mount in production type engines. Therefore, a comparison with two alternative sensors was performed to select the best one for engine heat transfer research. Two variations of a calibration rig were used, one with a fast opening shutter and one with a chopper with adjustable speed. This paper presents a comparison of the rise time based on measurements on both test rigs. Furthermore, measurements were carried out on a test engine to evaluate the capability of the sensors to determine the heat transfer to the cylinder walls.