Analysis Of Multi-blade Centrifugal Fan On CFD And Noise Prediction

Multi-blade centrifugal fan has been widely used for air-conditional system because of its high flow coefficient, high pressure coefficient, small size and low noise. It has gradually been an important technical means to predict the internal flow structure of fan by using an existing, mature, commercial CFD package.Based on the analysis of the traditional design method of the multi-blade centrifugal fan, proposals are made to frame the blade model line with biquadratic Bezier curve. In addition, after profound understanding the commercial CFD software, we made the parameterized modeling program more perfect which helps to generate many kinds of multi-blade fans on short time.In this paper the inner flow field in the centrifugal fan is numerically simulated and its flow characteristics are analyzed using the parameterized modeling program. Calculation results disclose that the flow in the fan shows complicated three-dimensional characteristics. Any geometrical parameters of a multi-blade fan's changes can affect its inner flow and outer performance especially the blade outlet angle, the number of blades, the frame of inlet, electromotor and so on. In order to study the influence extent of these parameters impacting on the performance, the internal flow field and loss of the fans are predicted and discussed on many type of multi-blade fan with different parameters. Some instructive conclusions have been derived from the simulate results, which will be helpful to improve the performance of multi-blade centrifugal fan.A new method was proposed to analyses the intensity and location of dominant aerodynamic noise source and the type of the noise in a centrifugal fan. In this method, the numerical solution of aero-acoustic field was avoided because of the difficulties of solving the Green function in an irregular space. To find the noise source, the three-dimensional unsteady viscous flow in the centrifugal fan was calculated by applying finite volume method and high order discrete scheme. Then, the time-domain and frequency-domain analyses on fluctuating component of static pressure in the flow field were carried out. Based on these numerical results, the intensity and location of dominant aerodynamic noise source and the type of the noise were ascertained according to the acoustic principles and the characteristics of the sound propagation. Some instructive conclusions have been derived from the simulate results, which will be helpful to study the aero-acoustic performance of multi-blade centrifugal fan.