The Leakage Gap Of Inlet And Performance Optimization Research Of Multi-blade Centrifugal Fan

Based on the cooperation project of a multi-blade centrifugal fan for ship air conditioner,this paper focuses on the problems such as missing the leakage gap of impeller inlet during the numerical simulation of prototype machine,which results in a sharp drop in performance at large flow rate and large deviation from experimental data,insufficient static pressure and limited size of fan.In order to solve the above problems,this paper studies the influence of different sizes of impeller inlet leakage clearance on fan performance,and compares the internal flow characteristics under with or without the leakage gap,and then improves the performance by using the methods such as installing the anti-vortex ring inside the volute and optimizing the impeller.Firstly,the prototype is simulated with constant flow rate and pressure boundary condition,and the validity of the calculation method is verified by the test data.The results of the internal flow field show that there is a cross-blade flow phenomenon in the impeller section at the tongue;Under the same working condition,with the increase of blade height,the greater the blocking area of the cross-blade flow to the impeller section at the outlet of the fan,the more severe the damage to the flow field,At the same blade height,with the decrease of flow rate,the phenomenon of cross-blade flow is more severe.Secondly,numerical simulation and analysis are carried out on the leakage gap model of impeller inlet with different sizes,the results show that when the leakage gap exists and the larger the size,the worse the performance of the fan and the larger the gap leakage,when the gap is neglected in the numerical simulation,the low speed and high static pressure zone formed in the shroud under the large flow rate causes the impeller outlet airflow to be squeezed by the air flow at the shroud,and the low static pressure zone is formed near the tongue at the shroud side,a large amount of reflux occurs under the action of outlet back pressure,which causes the fan performance to drop sharply,which deviates from the theoretical analysis results.Finally,the influence of simple anti-vortex and impeller on fan performance is studied and optimized,the results show that the simple anti-vortex ring and its length have different influence on the performance of the fan under different working conditions,and will form a larger scale eddy inside the volute,and then it affects the inside of the impeller and its intake state,resulting in the performance of the fan decline;By using the orthogonal test in the design of Taguchi methods to optimize the structural parameters of the impeller,the results show that the optimized fan impeller has better effect on airflow acceleration,more uniform circumferential velocity,stronger function and higher efficiency.,the static pressure at the rated operating point is about 10.3% higher than that of the prototype before the width optimization of the volute,and the static pressure whole working condition is greatly improved.