Discrete noise control of cooling fan module: Stator and rotor interaction

Abstract

With the development of automobile industry and the continuous demand for driving comfort, discrete noise level of the automobile cooling fan module (CFM) should be controlled. In this study, a non-uniform rotor blade design is developed, and the methods for predicting discrete noise are theoretically expounded using a simplified model. The lobe modes of the stator and rotor interaction (SRI) and their influence on the sound power of orders are evaluated. Using above methods, a specific discrete noise control method is proposed for a CFM with seven rotor-blades (RBs) and eight stator-vanes (SVs). Subsequently, on combination with numerical simulation, the pulsation characteristics of the RBs and SVs with non-uniform circumferential distribution in free air are analyzed. From the results, the pulsation sources of discrete components and the SRI mechanisms are examined. Finally, samples are fabricated to analyze the discrete characteristics of the CFM acoustic spectrum through acoustic experiments to verify the effectiveness and applicability of present methods. It is shown that the circumferential non-uniform design changes distribution characteristics of the pulsating force on the RB and SV surfaces as well as the SRI lobe pattern, which greatly affects the amplitude distribution of discrete components in the CFM acoustic spectrum. This method can effectively and quickly predict and control discrete noise in the early stages of CFM design.