Unsteady flow characteristics and their control of a centrifugal fan in a commercial air conditioner

Abstract

In this study, unsteady flow characteristics of a centrifugal fan in a commercial air conditioner are investigated and flow control ideas are suggested to develop a low noise fan. The experiment is conducted at the operation condition where the fan rotational speed is 580 rpm and the Reynolds number is 167,000 based on the blade tip velocity and chord length. The instantaneous velocity fields are acquired using a particle image velocimetry. Fluctuating flow appears at the leading edge showing intermittent separation, whereas vortex shedding occurs at the trailing edge. Particularly, intermittent reverse flow appear near the shroud having a high Reynolds stress level. To control these flow structures, we modify the shapes of the blade leading edge and shroud of the centrifugal fan, which results in noise reduction. The flow fields of the base and modified fans are compared and discussed.