对旋轴流式喷水推进泵的进口预旋

Inlet pre-whirl for contrarotating axial-flow water-jet pump

为了研究喷水推进泵在小流量下效率下降较快的原因,应用计算流体动力学方法对不同工况下的喷水推进泵进行数值模拟,研究进口预旋的产生和发展,分析进口预旋对效率的影响以及转速对进口预旋的作用.结果表明:在设计工况Q_d时,首级叶轮进口的绝对速度圆周分量vu接近0,基本不随流道半径的变化而变化,进口预旋可以忽略;0.8Q_d时,vu随流道半径的增加出现小幅增大,仅仅在轮缘处有较小的正预旋;从0.6Q_d开始,预旋变化明显,流量越小,预旋变化越大.小流量下,降低首级叶轮的转速,可以有效地改善进口预旋,提高泵的效率;通过调节叶轮转速,可以有效地改善泵内部的流动状态并通过比较分析出小流量相对较优的转速.研究结果对于其他比转数的喷水推进泵的进口预旋分析具有重要的指导意义.

To study the reason why water-jet propulsion pump efficiency at a small flow rate decreased rapidly,the computational fluid dynamics method was applied to the numerical simulation of water-jet pump at a small flow rate. Based on different flow rates and rotation rate control methods,the emergence and development of inlet pre-whirl was studied and the relationship between the rotation rate and the inlet pre-whirl was analyzed. The results show that under the working condition,circumferential component of the absolute velocity of the front inlet impeller is close to 0 and changes hardly following the flow channel,and the inlet pre-whirl can be neglected. At the 0. 8Q_dworking condition,the increasing along with the change of flow channel is very small,there is a small pre-whirl only at the rim.At the beginning of 0. 6Q_d,the change in inlet pre-whirl becomes obvious,the lower the flow is,the greater the change is. Under the low flow condition,reducing the front impeller speed can effectively improve the inlet pre-whirl and also can improve the efficiency of the pump. Regulating the impeller speed can effectively improve the inner flow of the pump. The results are of important guide signifi-cance to the inlet pre-whirl analysis of other specific speed water-jet propulsion pumps.