Turbochargers are indispensable for improving the power-weight ratio, emissions and fuel consumption of diesel engines. Especially, high response is demanded for turbochargers for automotive use. High performance turbochargers with ceramic or TiAl turbines and variable nozzles have since been commercialized.

We have developed a variable geometry turbocharger that has involves technical items as follows: (1) A compressor with Variable Inlet Guide Vanes (VIGV) and an impeller having convex blades. (2) A mixed flow turbine with a half vane-type variable nozzle (HVN) that has variable vanes located mutually between fixed vanes. (3) Lightweight and high strength materials used for rotating parts.

The VIGV and convex blade impeller improve the surge limit and adiabatic efficiency of the compressor. HVN has the merit of minimizing the clearance between the variable vane and the wall of housing and thus, improves the turbine efficiency. The TiAl turbine wheel, magnesium impeller and high modulus steel for the shaft improve the response and rotating vibration of turbochargers.

Through numerical aerodynamic analysis, stress and blade vibration analysis, rotating vibration analysis and the technology of materials, variable geometry turbocharger with high efficiency, a wide flow range and high response has been developed.
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