Aerodynamic and Aeroacoustic Study on the Cross Flow Fan with Block Stagger Impeller

Abstract

In order to reduce discrete frequency noise of cross flow fan (CFF) of indoor unit of air-conditioner, both aerodynamic and aeroacoustic performance of CFF with block stagger impeller is investigated by using experimental and theoretical method. Four CFF impellers with block stagger angle of 0°, 3.50°, 4.00° and 5.14° are adopted as research objects. It can be shown that the block stagger technique has little influence on the aerodynamic performance of CFF. However, the discrete tone noise levels could be effectively reduced, even though the broadband noise level is also kept constant. Based on the Lighthill’s acoustic analogy theory and Fourier transform character, discrete frequency noise prediction model of CFF is built and used to analyze the influence of different block stagger angles on the discrete frequency noise of CFF. Theoretical analysis results agree well with experimental results. The model can be used to analyze the relationship between stagger angle impeller and BPF noise together with its harmonics of CFF. Meanwhile, the design method of optimum stagger angle of block stagger impeller is also discussed.