多翼离心风机跨叶轮流动数值模拟研究

Investigation on numerical simulation of impeller-across flow structure in multi-blade centrifugal fan

为准确模拟多翼离心风机各工况内流特性,将定常和非定常数值计算的结果与试验数据进行了对比,结果显示：非定常计算的结果比定常计算更准确,收敛性也更好.对于高效工况及大流量工况,定常计算足以准确预测风机的性能;但对于小流量工况,则须进行非定常计算以捕捉可靠的流场.不同工况下风机内流场的进一步分析表明：部分气体在出口背压的作用下,于蜗舌处反向穿过叶道并在下游重新进入叶轮形成跨叶轮流,其规模和强度随风机流量的减小逐渐增强.该跨叶轮流动不仅封锁住部分叶轮段,改变叶轮进出口处的压力脉动特性,还进一步影响风机进气室内的流动状态.

To accurately simulate the internal flow characteristics of the multi-blade centrifugal fan,the steady calculated results and transient calculated results with the experimental data were compared.The results show that transient calculations are more accurate with better convergence than steady calculations,and results of steady calculations are accurate enough when predicting the fan pressure on high-efficiency conditions and high flow rate conditions.But transient calculations are required in order to capture the reliable fan flow field under low flow rate conditions.The fan flow fields under different conditions were further analyzed,which demonstrates that part of airflow reversely pass across the impeller near the tongue under the effect of the outlet back pressure and then re-enters the impeller at some place downstream,and the range and intensity of this flow pattern,named as＂impeller-across flow＂,both increase gradually as the fan flow rate decreasing.Impeller-across flow not only＂blockade＂part of the impeller,change the pressure pulsations near impeller,but also affect the flow patterns in the fan suction chamber.