Flow Field Simulation and Noise Control of a Twin-Screw Engine-Driven Supercharger

Abstract

With the advantages of good low-speed torque capability and excellent instant response performance, twin-screw superchargers have great potential in the automobile market, but the noise of these superchargers is the main factor that discourages their use. Therefore, it is important to study their noise mechanism and methods of reducing it. This study included a transient numerical simulation of a twin-screw supercharger flow field with computational fluid dynamics software and an analysis of the pressure field of the running rotor. The results showed that overcompression was significant in the compression end stage of the supercharger, resulting in a surge in airflow to a supersonic speed and the production of shock waves that resulted in loud noise. On the basis of these findings, optimization of the supercharger is proposed, including expansion of the supercharger exhaust orifice and creation of a slot along the direction of the rotor spiral normal line at the exhaust port, so as to reduce the compression end pressure, improve the exhaust flow channel, and weaken the source of the noise. Experimental results showed that the noise level value of the improved twin-screw supercharger was significantly lower at the same speed than the original model, with an average decrease of about 5 dB (A).