Experimental Investigation and Numerical Simulation of Gas Flow Through Wastegated Turbine of Gasoline Turbocharger

Abstract

Turbochargers are generally used in the combustion engine due to their capability to increase the specific power. This paper investigates the performance of the turbocharger turbine, which is mounted in a gasoline engine. Different working points, including close and open wastegate positions, are studied in a steady-state condition. The experimental test of this article has been performed on an engine test cell. The movement of the wastegate linkage in different working conditions of the engine was measured in the test cell. Furthermore, the static pressure was measured at the different positions of the turbine housing. Simulation results show that as the wastegate starts to open, maximum loading happens. However, increasing the wastegate opening angle will decrease the force, which is caused by the passing gas. It was found that at 2 degrees opening angle of the wastegate, there is an 80 kPa pressure difference between two sides of the wastegate valve. When the wastegate has a small opening angle, the pressure distribution on the flat surface of the valve is not symmetric, which means the gas does not provide a 360° flow distribution around the valve. Moreover, streamlines show that the high-speed flow passing bypass passage disturbs the flow exiting the turbine blades. Results show that the opening of the wastegate flap can reduce the turbine's power. The 6 degrees opening of the wastegate causes a 30 percent power reduction. Moreover, the simulation results of the turbine's map show that at the constant mass flow rate, the opening of the wastegate from the closed position to 6 degrees causes the pressure ratio to decrease 26 percent.