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Although radial turbines are used in small turbochargers, real flow has never been conclusively cleared. Accordingly, we, the authors measured the internal flow of the rotating blades using a Laser Doppler Velocimeter (LDV) and a high frequency response pressure probe. The arising loss mechanism was examined, and comparison was done about analysis conducted by means of Computational Fluid Dynamics (CFD). The results of measurement with LDV and analysis by CFD are in good agreement, and the arising loss mechanism was found to consist of the accumulation of low energy fluid on shroud side suction surface of blade outlet.

To improve the performance of the centrifugal compressor for automotive turbocharger, it is essential to understand the complicated flow phenomena caused by its complex blade geometry. Authors carried out the detailed flow measurement of the centrifugal compressor impeller uisng Laser Doppler Velocimeter (LDV). The test impeller is a 9.1 times enlarged model of real turbocharger. In result authors found out the low velocity region is grown up at the suction surface of the inducer according to the reduction of flow rate. The experimental data are compared with the three dimensional (3D) viscous flow analysis and acceptable agreement was observed.

The exhaust emission gas regulations on truck diesel engines are becoming increasingly stringent in various countries in the coming years. The '94 EPA (U.S.A.) regulations include the entire working range of engines, including transient conditions; thus requiring a large-scale improvement in engine properties. For this reason, various engine components are now undergoing a series of improvements; in particular, the injection system has experienced a major renovation. However, the improvement of a naturally-aspirated engine has its own limit; and the turbocharged engine with inter-cooler becomes essential. Mitsubishi Heavy Industries has been pushing ahead with the development of turbochargers for use with the truck diesel engines. To assist the Diesel engine manufacture to meet these new emission regulations, we have developed various turbocharger options for improving engine performance, in addition to our continuing efforts for improving the aerodynamic properties.

To cope with che possible heat soak phenomenon occuring in turbochargers, an analytical system has been developed making it possible to interpret the soak phenomenon so an effective eqantitative improvement can be quickly determined. This system includes an input generator, which has been obtained by modeling, on the basis of the existing three-dimensional thermal conduction analysis, the physical form of each part of the turbocharger according to degree of its influence on the analysis, an iterative system of analysis and, output from which results can be consecutively estimated. This analytical system has been verified by comparison to bench test results. It can be expected that this system will become an effective means to improvement and development.