液力减速器模型空化特性数值模拟及试验研究

Numerical simulation and experimental study on cavitation behavior of hydraulic retarder model

为了研究液力减速器内部流场空化特性,基于ANSYS CFX软件,采用RNG k-ε湍流模型和Zwart-Gerber-Belamri空化模型,选取液力减速器模型单个流道作为研究对象,对其在泵轮外环壁不同压力时进行数值模拟,并搭建减速器试验台,进行降压性能试验.将数值模拟结果与试验结果进行对比分析,验证了数值模拟方法对液力减速器空化特性预测是可靠的.研究结果表明:数值模拟方法获得的性能曲线与试验结果变化趋势一致,且可以捕捉到空化初生状态,数值模拟与试验结果平均误差为3.24%,可较好地反映液力减速器内部空化特性;随着泵轮外环壁压力不断降低,空化最先发生在泵轮叶片吸力面靠近轮毂的位置,之后向叶片中部扩大,直至占据叶片吸力面大部分区域;空泡分布在径向存在不均匀性,泵轮外环壁压力为0.25 MPa时,空化区域面积比(Sc/S)随着径向位置(r/R)的增大呈现先增大后减小的趋势,空化现象在流道靠近轮毂位置(r/R=0.3~0.5处)较为严重.

To study the cavitation behavior of hydraulic retarder, the RNG k - e turbulence model and Zwart - Gerber - Belamri cavitation model were chosen to simulate the cavitating flow in a single channel of a retarder model when the outer wall of the pump impeller was subject to different pressure levels based on ANSYS CFX. Additionally, a test stand was established to carry out performance tests at reduced pressure levels, and the predicted performance were compared with the measured values to validate the accuracy of numerical simulation. The results show that the error in prediction is 3.24%, indicating the retarder with a better internal cavitation characteristic. With the decrease of pressure on the outer wall of impeller, the vapor first occurs on the blade suction side close to the hub. and then develops toward the middle of blade till covers the most area of the suction side. The vapor is distributed in the radial direction unevenly. The dimensionless cavity area （S,/S） increases first and then decreases with the increase of radial position （r/R） when the external wall pressure is at 0.25 MPa. The cavitation near the hub position （ r/R = 0.3 - 0. 5 ） is more serious.