Heat Transfer Correction Model for Turbocharger Compressor Performance Maps

Turbochargers are still one of the most common solutions to improve internal combustion engines performance. The correct evaluation of turbochargers characteristic maps is one of the main issues to achieve a good matching with internal combustion engines. In a 1D procedure the accuracy of performance maps constitutes the basis of the turbocharger matching with the engine. The classical quasi-steady approach assumes that compressor and turbine characteristic maps are evaluated under the hypothesis of adiabatic turbocharger behavior. The aim of the paper is the investigation of the effect of heat transfer phenomena on the measured turbocharger maps. A model to correct compressor efficiency evaluated starting from measured data, thus removing the heat transfer effects, is proposed. The compressor steady flow behavior has been analyzed through specific tests performed at the test rig for components of propulsion systems of the University of Genoa, under various heat transfer conditions. The experimental campaign was conducted on a water-cooled turbocharger for spark ignition engines and on an uncooled turbocharger for diesel engines considering the effect of different heat transfer conditions. Then, measurements were carried out under quasi-adiabatic conditions, maintaining a constant temperature between the compressor - intermediate casing - turbine to validate the proposed model. Thanks to this specific campaign it was possible to validate the proposed model highlighting a high degree of accuracy. The main advantage of the method presented here compared to others developed by the authors or found in the open literature is its ease of use, thus requiring a small amount of geometric and physical information that can be obtained in a standard turbocharger test bench.