A Turbocharger Selection Computer Model

A variable turbine vane angles turbocharger selection model was developed. The model, which is based on a single entry fixed vanes angle turbocharger matching model developed in earlier study, is of a modular structure and designed to run on a personal computer. It is based on the principles of conservation of mass, energy and momentum in one dimension. A heat transfer sub-model was incorporated to account for the exhaust manifold losses and to overcome undesirable turbine-inlet temperature profile. Non-isentropic flow was assumed through the compressor using one-dimensional, semi-empirical loss calculation formula to improve the prediction accuracy of the model at the compressor exit.

The model was verified by comparing the calculated results with the test data of a Rover 2.4 litter direct injection diesel engine fitted with a “3K-K24” type single entry turbocharger. The engine was coupled to an Eddy-current dynamometer and provided with facilities to assess its performance under various running conditions. The verification procedure revealed substantial improvements in the model's accuracy, as compared with the previous model, and a more definitive understanding of its limitations. The benefit of modeling the heat losses from the exhaust manifold was clearly demonstrated. Comparison of the predicted and measured results also revealed that the model could provide a valuable tool in predicting the performance of a variable geometry turbocharger. This in turn confirmed the viability of the improved model and strongly indicated to its suitability in the initial stages of turbocharger matching and design.