开式燃油离心叶轮汽蚀特性非定常仿真及分析

Unsteady simulation of cavitation characteristics of open fuel centrifugal impeller

为了明确开式燃油离心叶轮汽蚀特性的非定常演变规律,在不同进口压力下进行汽蚀非定常仿真,重点分析叶轮及蜗壳关键流动区域内非定常流动特点、气液两相分布特点及压力脉动时频特性。确定汽蚀非定常仿真边界,对不同仿真步长及汽蚀模型进行相关性检验。将数值仿真预测结果与其性能试验结果对比,结果表明扬程和效率最大误差均小于5%,即所采用的仿真方法有效。仿真结果表明:不同进口压力下,叶轮进口区域均会产生一定的空化区域,而低进口压力下该区域会发生扩张,从叶片吸力面延伸至相邻叶片压力面,并逐渐扩展至叶片出口区域。另外,叶轮流道内主频为转频f_n,汽蚀的产生影响了进口区域的压力脉动幅值,仍会存在一定的非定常强度;部分位置出现了其他倍频,而蜗壳流道内主频仍为叶频fb。

To clarify the unsteady evolution of cavitation characteristics of open fuel centrifugal impeller,the unsteady cavitation simulation was carried out under different inlet pressures,the characteristics of unsteady flow,gas-liquid two-phase distribution and time-frequency characteristics of pressure pulsation in the key flow regions of impeller and volute were emphatically analyzed.The unsteady cavitation simulation boundary was determined,and the correlation between different simulation steps and cavitation models was tested.By comparing the results of numerical simulation predictions and performance tests,it was found that the maximum errors for both head and efficiency were less than 5%,which indicates that the adopted simulation method is effective.The simulation results show that the cavitation zone will appear in the inlet area of the impeller under different inlet pressures.At low inlet pressure,this area will expand from the suction surface of the blade to the pressure surface of the adjacent blade,and gradually expand to the exit area of the blade.In addition,the main frequency in the impeller channel is the rotation frequency fn,the cavitation affects the amplitude of the pressure fluctuation in the inlet region,and there is still a certain unsteady strength.Other frequency multiplications appear in some positions within the impeller flow path,but the main frequency in the volute channel is still the blade frequency fb.