Abstract: The free acceleration smoke is eliminated by cascading with an alternating current electric supercharger(ES) in a pressurization gas path of a turbocharged inter-cooled bus. The quantity of the fresh air in cylinder, angle acceleration of the turbocharger and its dynamic response can be increased rapidly with the ES working at a free acceleration of the diesel engine, simultaneously the characteristics of the diesel engine at low speed are improved. Experimental results about the flow and current characteristics of different types of ES and road test results have been both achieved, which confirm that an increase in impeller diameter of the ES will bring about a higher air intake flow and dynamic response of the turbocharger. Mathematical expressions of a compressor’s characteristic parameters are introduced to analyze the influence on the turbocharger and its dynamic response when using an ES for auxiliary pressurization. Angle acceleration of the turbocharger at free acceleration can be promoted when using an ES. The more the mass flow of the ES is, the more angle acceleration of the turbocharger and power consumed by an ES will be increased. The value of the free acceleration smoke for the original engine has been reduced by 54% with an ES of which the impeller diameter is 90 mm.

Key words: Alternating current electric supercharger, Electric auxiliary pressurization, Smoke emission at a free acceleration, Turbocharged inter-cooled diesel engine