【摘要】 提出的在离心风机轮盖上靠近叶片吸力面处开孔的方法,可利用蜗壳内的高压气体产生射流,从而直接给叶轮内的低速或分离流体提供能量,以减弱由叶轮内二次流所导致的射流-尾迹结构,并可用于消除或解决部分负荷时常发生的离心叶轮的积灰问题.通过对离心风机整机的数值实验发现,轮盖开孔后,在设计点附近的风机压力提高了约2%,全压效率提高了1%以上,小流量时压力提高了1.5%,全压效率提高了2.1%.进一步的流场分析表明,在设计流量和小流量时,由于轮盖开孔形成的射流可以明显改善叶轮出口的分离流动,减小低速区域,降低叶轮出口处的最高速度和速度梯度,从而减弱离心叶轮出口处的射流-尾迹结构.此外,沿叶片表面流动分离区域减小,压力增加更有规律.所提方法可以提高设计流量和小流量下的闭式离心叶轮性能和整机性能,结合其他离心叶轮自适应边界层控制技术,可全面提高离心叶轮的性能.更多还原

【Abstract】 A new method of drilling through-holes near the blade suction surfaces in the shroud of a centrifugal impeller is proposed,where pressurized air in the volute casing generates jet flows to directly supply additional energy to the flow characterized by low velocity or separation inside the impeller.Consequently the jet-wake flow caused by secondary flows in the impeller is weakened,and the often encountered problem of dust or ash accumulated on the blades under partial loads is expected to be solved to some extent.The computational results show that the total pressure rise of the fan with holes in the shroud increases by 2% and efficiency over 1% at designed flow rate while the increase in the total pressure rise reaches to 1.5% and efficiency 2.1% at lower flow rate.Furthermore,the change of the internal flow fields indicates that the separated flows at the exit of the impeller are improved obviously due to the jet flows through the holes at designed and lower flow rates.In addition,the area with low velocity and the peak values of the radial velocity as well as the radial velocity gradient are also reduced reasonably,which leads to weakened jet-wake flows at the exit of the impeller.Along the blades the separation regions become smaller and the increases in the static pressure become more regular.As a result,better performance of the shrouded impeller and of the fan can be achieved by drilling through-holes in the shroud,and this new method can be used in combination with other adaptive boundary control technique in the centrifugal impeller to totally improve the performance of the fan.更多还原