Numerical Simulation Of Inner Airflow And Structure Optimization On A Centrifugal Blower

The traditional centrifugal blower products in our country mostly take one-dimensional flow or two-dimensional flow theory when the blower’s structure was designed. While the actual flow field in blower is very complex with three-dimensional unsteady turbulent viscosity flow, resulting in the blower efficiency low in generally, which should be improved. This study was based on D250-11 type of centrifugal blower and used the commercial computational fluid dynamics software Fluent to complete a whole numerical simulation at all working conditions. Then the performance curve of the centrifugal blower was calculated out, according to the situation, the parameters of the impeller and the line of the volute type was optimized to improve the blower pressure ratio and efficiency. The results of our studies provided the basis for analyzing the factors which affect the blower and optimizing the design of the centrifugal blower. The methods and conclusions in this paper were as follows:1) The D250-11 type centrifugal blower with the volume flow rate 400 m3/min was investigated. The whole blower’s the fluid domain was divided into three parts including imported parts, impeller and volute. Soldworks was used to set up the three-dimensional geometry model, and then completed the mesh discretization through ICEM-CFD. The whole numerical calculation model was established.2) The commercial computational fluid dynamics software Fluent was used to perform the blower’s numerical calculation in all condition and the blower’s performance curve was drawn out. Compared with the performance curve of experimental test, the numerical simulation’s relative error of export static pressure was less than 3%; the relative error of the polytropic efficiency was less than 2%. So the rationality of the numerical model and reliability of the simulation results were verified.3) The numerical calculation model designed above was applied to calculate out the polytropic efficiency, the total pressure efficiency, and the effective power of the impeller in all conditions, and the performance of the blower in different impeller parameters’(blade numbers, blade outlet angle, rotate speed) aerodynamic performance under the whole working range was investigated.The optimization blade outlet angle was 57° for retrofit, at the design point of 400 m3/min, the centrifugal blower’s polytropic efficiency, outlet static pressure, the total pressure efficiency, shaft power improved by 1.239%,1846.OPa,0.532% and 11.83kW, respectively.4) The numerical calculation model designed above was applied, and the blower in the volute cross-section shape (circular cross section, eccentric volute, bezier curve volute) under the whole working range of aerodynamics performance was studied. After the modification of blower, the results showed that the performance curves were offset in the direction of large flow. Spiral cone angle 45°bezier curve at the design point of 400 m3/min was the optimized result, under which the centrifugal blower outlet static pressure increased by 1090.3Pa, polytropic efficiency improved by 4.212%, total pressure efficiency increased by 3.947%, and shaft power decreased by 3.85kW.