Aerodynamic Performance Improvement and Noise Control for the Multi-Blade Centrifugal Fan in Air Conditioner by Using Concave Volute Tongue

The structural formation of the multi-blade centrifugal fan’s volute tongue results in a complex flow pattern. This study focuses on the design of a concave volute tongue structure to address the issues of volute tongue backflow and blade path backflow. A Bezier curve with five control points was utilized to accurately shape the profile of the concave volute tongue. Five different solutions for the concave volute tongue were developed. Comparative analysis results show that the depth of the volute tongue depression has minimal impact on the fan’s efficiency performance. However, the amplitude of noise reduction initially increases and then decreases as the depth of the volute tongue depression increases. Experimental tests and numerical simulations indicate that the implementation of the concave volute tongue structure effectively suppresses volute tongue backflow and blade channel backflow at the impeller outlet, resulting in a maximum reduction in aerodynamic noise of 0.8 dB. The sound pressure level of the multi-blade centrifugal fan with the concave volute tongue structure is lower in most frequency band under low static pressure conditions compared to its original design. The V3 multi-blade centrifugal fan demonstrates better static pressure performance across all working conditions, particularly at high flow rates. The V3 multi-blade centrifugal fan exhibits a 10.1 Pa increase in the maximum static pressure level compared to its original design. These improvements in static pressure and flow capacity of the multi-blade centrifugal fan contribute to energy savings and a reduction in pollutant emissions.