Abstract: A testing rig, consisting of two electric superchargers and a check valve, used to simulate and investigate the air flow direction affected by check valve in pressurization gas path is built. Through this way higher fill gas efficiency of electric supercharger can be achieved, which will give rise to more air inflow of diesel engine at its working condition mutation, improving transient FSN. By setting the speed of the two electric Superchargers respectively, one is used to simulate the turbocharger of the diesel engine of a bus and the other is used to simulate electric supercharger which supplys additional air for a sharp acceleration, to study the air flow direction affected by check valve in pressurization gas path. Testing results indicate that without the check valve, when the flow rate of the electric supercharger is larger than that of the turbocharger, the total flow rate is equal to that of the turbocharger, and it will not increase while increasing flow rate of the supercharger, for the fill gas efficiency of the electric supercharger is low and air inflow is not increased.With the check valve, the total flow rate will increase while increasing flow rate of the supercharger, for higher fill gas efficiency of the electric supercharger is achieved and air inflow is increased. When the flow rate of the electric supercharger is smaller than that of the turbocharger, the total flow rate will not be affected by the electric supercharger while using the check valve and a by-pass comparing to the total flow rate while using a by-pass only, which means the air inflow will not be decreased by the electric supercharger when it stops.

Key words: Check valve, Gas flow direction, Pressurizing gas path consists of two electric superchargers