齿间间隙对双螺杆透平泄漏影响的数值模拟

为降低泄漏流对双螺杆液力透平效率的影响,以2/3齿双螺杆泵透平为例,根据双螺杆泵内齿间间隙的构成原理,首先建立其简化几何模型,利用透平腔内存在相对运动引起的剪切流动与各级腔室压差导致的压差流动理论,建立起齿间泄漏通道的数学模型.使用SCORG和Pumplinx软件对双螺杆液力透平进行全流场数值模拟,得到了双螺杆透平不同齿间间隙下的流场分布和流量变化规律.研究结果表明:不同间隙下螺杆的压力分布规律保持基本一致,每个密封腔室内的压力分布基本均匀,从进口到出口各相邻腔室的压力呈线性下降趋势;螺杆在齿间间隙附近出现多处泄漏通道,在各腔室压差的作用下,第一级腔内没有出现明显的高流速区域,从第二级腔内开始发生明显的高速泄漏;随着齿间间隙的不断增大,同一级腔内的齿侧间隙泄漏面积、泄漏速度以及流体从进口到出口的泄漏流量和容积损失都随之增大,当齿间间隙为0.04,0.08,0.12,0.16和0.20 mm时,由该间隙所造成的容积损失的值分别为4.03%,4.57%,5.00%,5.43%和5.72%.

Numerical simulation on influence of tooth clearance on twin screw turbine leakage

In order to reduce the effect of leakage flow on the twin screw hydraulic turbine efficiency,the two-thirds of tooth of double screw pump as turbine was selected.Firstly,simplified geometric mo-del was established according to the principle of twin screw pump inner clearance between teeth.A mathematical model of the leak path between the teeth was built by using the theory of the shear flow caused by relative motion in turbine cavity and differential pressure flow caused by differential pressure of the chamber at all levels.SCORG and Pumplinx software were used to conduct full flow field numerical simulation on the twin screw hydraulic turbine,and the flow field distribution and flow rate variation law were obtained under different tooth clearances of the twin screw turbine.The results show that the screw pressure distribution law under different clearances is basically consistent,the pressure distribution in each sealing chamber is basically uniform,and the pressure in each adjacent chamber from the inlet to the outlet presents a linear downward trend.There are several leakage channels near the clearance between the screw teeth.Under the action of the pressure difference of each chamber,there is no obvious high velocity zone in the first stage of the cavity,and obvious high-speed leakage occurs from the second stage of the cavity.With the increase of the gap between teeth,leakage area and leakage rate of tooth-side clearance in the same cavity increase.The fluid leakage from the inlet to the outlet and volume loss increase as well.When tooth clearance are 0.04 and 0.08,0.12,0.16 and 0.20 mm,the volume losses caused by the clearance are 4.03%,4.57%,5.00%,5.43%and 5.72%respectively.