口环间隙对诱导轮离心泵空化流动和性能的影响

为了研究口环间隙对前置诱导轮离心泵空化性能的影响,基于RNG k-ε湍流模型和Rayleigh-Plesset方程均相流空化模型,以前置诱导轮离心泵为研究对象,选取口环间隙为0.15,0.25,0.40和0.60 mm这4种方案对其进行空化流动数值计算,并与试验结果对比分析.研究结果表明,口环间隙大小对诱导轮离心泵的外特性和空化性能影响较大,随着口环间隙的增大,总扬程效率和叶轮扬程效率均减小,与口环间隙为0.15 mm时相比,总扬程效率和叶轮扬程效率分别降低了0.60%和4.21%,效率分别下降了6.50%和9.32%;而口环间隙的增大使得诱导轮扬程和效率均增加,分别增大了29.86%和28.40%.另外,随着口环间隙的增大,空化性能曲线出现波动现象,间隙越大,波动越明显;离心泵主叶轮工作面靠近前盖板出现云状空泡分布,空化不稳定,间隙越大,空化越不稳定,临界空化数越大.经分析,引起空化不稳定性的因素可能有: 口环间隙出口处泄漏高压流体对主流的冲击;口环附近空化的发生以及诱导轮空化引起叶片出口液流角的变化.

Effect of wear-ring clearance on cavitation flow and performance of centrifugal pump with inducer

In order to investigate the effect of wear-ring clearance on the cavitation performance of the centrifugal pump with THE pre-positioned inducer, the cavitation flow and performance in the centrifugal pump with the pre-positioned inducer were numerically simulated with four different projects which were 0.15,0.25,0.40 mm and 0.60 mm based on the RNG k-ε turbulent model combined with Rayleigh-Plesset Homogeneous cavitation model,and compared with experimental results. The results show that the size of the wear-ring clearance has a greater influence on the external performance and cavitation performance; with the increase of the wear-ring clearance, compared with 0.15 mm, the total head efficiency and the head efficiency of the impeller decrease, the changes of the head are up to 0.60%,4.21%,and the changes of the efficiency are up to 6.50%,9.32%. Moreover, the head and efficiency of the inducer increase, and they are up to 29.86%,28.40%.The cavitation curves wave with the increase of the wear-ring clearance and the decrease of the cavitation number, and the wider the clearanceis, the more obvious the flactuationis. The cloudy cavitation bubbles are distributed on the pressure surface that is close to the front shroud, which causes cavitation instability, and the wider the clearanceis, the more the cavitaionis,the greater the critical cavitation numberis. It is found that the factors that influence the cavitation instability of the pump are possibly related to the impact of leakage high-pressure fluid of the wear-ring outlet on the main flow,the occurrence of cavitation at the intersection of impeller inlet and wear-ring clearance outlet and the change of the outlet flow angel caused by cavitating in the pre-positioned inducer.