诱导轮进口轮毂比对离心泵空化性能的影响

以某型LNG电动超低温潜液泵作为模型泵,基于数值计算和试验,研究了诱导轮进口轮毂比对空化性能的影响规律.采用RNG k-ε湍流模型和Rayleigh-Plesset空化模型对模型泵进行全三维数值计算,试验验证了数值计算的准确性,并选取诱导轮进口轮毂比分别为0.260,0.274,0.289,0.303和0.318的5组离心泵设计方案,对比分析了诱导轮和叶轮内空化发展过程、静压分布规律及离心泵的空化特性曲线.结果表明:采用不同诱导轮进口轮毂比的离心泵,其诱导轮和叶轮流道内的空化发展过程基本一致,空化首先发生在诱导轮进口轮缘处的低压区;增大诱导轮进口轮毂比会提高诱导轮轮缘处液流的进口轴面速度,致使叶片进口冲角降低,在叶片吸力面产生脱流,并且低压分布区域的面积逐渐扩大,离心泵的空化性能下降.因此,在诱导轮的设计过程中,为了获得更高的离心泵空化性能,可在适当范围内降低诱导轮进口轮毂比.

Effect of inducer inlet hub ratio on suction performance of a centrifugal pump

Based on numerical simulation and experiment, the influence of inducer inlet hub ratio on suction performance was investigated in terms of a type of submersible electric cryogenic LNG pump. Three-dimensional, steady, turbulent, cavitating flows in the pump were simulated by using the RNG k-ε turbulence model along with the full cavitation model, and the accuracy of simulations was validated with experiment on a model pump. Five pumps were designed with five inlet hub ratios such as 0.260, 0.274, 0.289, 0.303 and 0.318, respectively. The cavitation developing process, static pressure distribution in the inducer and impeller and suction performances curve of these pumps were analyzed and compared. The results showed that the cavitation developing processes in the inducer and impeller are basically identical, i.e. a cavity always occurs firstly in the low-pressure zone at the inducer inlet tip regardless of inlet hub ratio. An increasing inducer inlet hub ratio can result in an increased meridian velocity at the inlet, and reduce the angle of attack. As a result, flow separation occurs on the blade suction side, and the low-pressure zone expands gradually; eventually the pump suction perfor-mance is impaired. Therefore, in order to obtain a better suction performance, the inducer inlet hub ratio can be reduced in a proper range.