液环泵叶片形状对叶轮进口回流及其外特性的影响

Influence of blade shape of liquid-ring pump on inlet reverse flow and its hydraulic characteristics

为减小液环泵叶片进口回流及冲击,基于非稳态气液两相流数值模拟方法,分别从叶片进口扭曲设计及叶片型线2个方面分析叶片形状对液环泵进口回流结构及其外特性的影响规律.研究结果表明:液环泵进口扭曲叶片设计能够有效抑制进口冲击引起的脱流,但叶片进口扭曲引起叶轮流道位置相对后移,吸气口始端叶轮流道内气液界面运动引起的相对体积扩充率降低,叶轮进口回流现象加剧;由于流道周向不对称,吸气区叶轮流道在进口产生真空的能力各不相同,由气液分界面运动引起的相对体积扩充率能够清楚地解释叶轮进口压力分布特性及回流结构;在叶片进口扭曲的基础上,控制叶片非吸入侧前弯能够有效提升吸气口始端流道的相对体积扩充率,θ=6°的进口扭曲叶型非吸入侧前弯设计叶片使得液环泵进口回流强度得到进一步的抑制,泵效率从15.46%提升至16.20%;叶型包角对进口真空度及进口回流强度的影响显著大于叶片出口安放角,增大叶型包角能够使吸气口始端叶轮流道沿旋转方向前移,增大流道内相对体积扩充率,降低回流强度,进而提高液环泵的真空度以及效率.

To reduce the flow impact and suppress the reverse flow at the blade inlet of the liquid-ring pump,the transient gas-liquid two-phase flow was simulated using numerical methods.The effects of blade shape on the inlet reverse flow and its hydraulic performance of the liquid-ring pump were analyzed in terms of the blade profile and the distortion of the blade inlet.The research results indicate that the inlet twisted blade of a liquid-ring pump can effectively suppress the flow separation caused by inlet flow impact.However,the inlet twisted blade causes the backward movement of the vane channel,which results in the decrease of the first channel volume expansion for the movement of the gas-liquid interface,and the reverse flow of the blade inlet aggravates.Due to the circumferential asymmetry of the flow channel,the vacuum generated at the inlet of each channel in the suction area is different.By introducing the relative volume expansion rate caused by the movement of the gas-liquid interface,the pressure distribution of the impeller inlet and reverse flow structure can be properly explained.Based on the inlet distorted blade design,the non-suction side forward bending can effectively improve the relative volume expansion rate of the flow channel at the beginning of the suction port.For the non-suction side forward bending design of the 6°inlet distorted blade liquid-ring pump,the reverse flow near the inlet is further suppressed,and the pump efficiency is increased from 15.46%to 16.20%.The influence of the blade wrap angle on the inlet vacuum and inlet reverse flow strength is significantly greater than that of the blade setting angle.With the increase of the blade wrap angle,the vane channel at the beginning of the suction port moves forward along the rotation direction of the impeller,which causes the increase of the volume expansion rate in this channel.Then,the reverse flow near the impeller inlet is suppressed,as a result,the vacuum and efficiency of the liquid-ring pump are improved.