基于CFD的混流泵空化特性研究

Cavitation performance research of mixed-flow pump based on CFD

应用剪切应力输运(SST)湍流模型和基于Rayleigh-Plesset方程的混合物均相流空化模型,求解雷诺时均Navier-Stokes方程,对某混流泵在设计工况时的流场进行数值模拟.根据计算结果获取了泵的扬程衰减曲线,捕捉到泵内空化的发生、发展过程,对轻微空化、临界空化和严重空化3种工况下叶轮内空泡体积分布特性做对比分析.模拟结果表明:该泵空化性能满足设计要求;叶轮内空泡最初发生在叶片吸力面进水边靠近轮缘处,该空泡区随汽蚀余量降低逐渐向轮毂方向和叶轮出口方向延伸;轮缘空泡初生于叶片进水边,沿着叶缘翼型逐渐发展成一条长带;轮毂空泡集中于叶根翼型尾部,轮毂空泡体积分数明显大于轮缘;叶片各通道间空泡分布相似,严重空化时空泡造成叶片通道严重阻塞致使泵扬程急剧下降.

The cavitating flow in a mixed-flow pump under the design working condition was simulated numerically with the SST turbulence model and homogeneous mixture cavitation model based on the Rayleigh - Plesset equations by solving the time-averaged Navier - Stokes equations. The NPSH-H curve was extracted from the results, the cavitation inception and development were captured as well. The features of vapour volume fraction distribution in the impeller were comparatively analyzed under the slight, critical and severe cavitation conditions. The results show that this pump has met the requirement on its cavitation performance. A cavity appears firstly on the blade suction surface near the leading edge and the shroud, as NPSH is reduced, it extends towards the hub and trailing edge. The tip cavity originates from the blade leading edge and develops into a strip along a blade contour on the shroud. The hub cavity accumulates near the blade trailing edge on the hub, further the vapour volume fraction on the hub is evidently larger than on the shroud. A similar cavity distribution is indentified in all the impeller passages, and the serious blockage due to cavity in the flow passages results in a sharp reduction in pump head under the sever cavitation condition.