Motoki Ebisu

Development of Two-Stage Turbocharger System with Electric Supercharger

To satisfy both environmental regulations and better drivability requirements, high-level control of automobile engines is currently in demand, and electrification is in progress. An electric supercharger, in which a supercharging compressor is driven by a high-speed motor instead of an exhaust turbine, improves the transient response of the turbocharger by due to the motor high-speed response. An engine with an electric supercharger offers comparable fuel consumption to a naturally aspirated engine, and is expected to facilitate the downsizing of engines. The electric supercharger prototype consists of a centrifugal compressor impeller and a high-speed motor rotor, supported by grease lubricated ball bearings. In this paper, we explained development of grease-lubricated electric supercharger and electric two-stage supercharger system combined with another turbocharger at 12 V power supply specifications. Specially, this paper introduces the result of the engine bench test and simulation using engine simulation tool (GT-Power). Moreover, we report the performance test results exhibiting a high-speed response of 0.7 s acceleration time to attain a compressor operating point rated at 2.4 kW, 90,000 rpm. As a result of engine test using a 1.5 L gasoline engine, the electric two-stage turbocharger demonstrated the 43 % improvement in a response time at 1,500 rpm as compared with normal two-stage turbocharger. Also, the electric two-stage supercharger was found to be effective in the catalytic activity of the cold start when the turbine outlet temperature over 100 °C higher than the two-stage turbocharger. We aim to accelerate technical development towards production, and to contribute ever tightening CO2 reduction with automobile engines from now on.