Heat Transfer on a Turbocharger Under Constant Load Points

The processes occurring in turbo machinery applications are frequently treated as adiabatic. However, in a turbocharger significant heat transfer occurs, leading to a deficit of turbocharger performance. The overall objective of this experimental work is to improve the understanding of the heat transfer process taking place in a turbocharger when installed on an internal combustion engine. In order to do this, beyond the standard set of measurements needed to define the turbo operating point, a large number of thermocouples were installed on the turbocharger. The tests results allow the quantification of the temperatures within the turbocharger and revealed that a nonuniform temperature distribution exists on the compressor and turbine casings. This is partly attributed to the proximity of the turbocharger to the engine. This process plays a role on the deterioration of the compressor efficiency when compared to the corresponding adiabatic efficiency. A correlation that allows the calculation of the compressor exit temperature is proposed. The method uses the surface temperature of the bearing housing; it was validated against experimental data with deviations no larger than 3%. A simplified 1-dimensional heat transfer model was also developed and compared with experimental measurements. The algorithms calculate the heat transferred through the turbocharger, from the hot end to the cold end by means of lump masses. The compressor performance deterioration from the adiabatic map is predicted.