气液两相流泵偏离设计工况，特别是在小流量工况下运行时，随进口含气率IGVF(Inlet gas volume fraction)的增加，泵增压能力会突然下降，并伴随剧烈振动。该文采用数值模拟方法研究了叶顶间隙分别为1。0 mm和1。7 mm的气液两相混流泵在偏工况下的气液两相流动规律，通过对比泵外特性和泄漏涡的数值模拟结果与试验结果，发现该数值模型可较准确地反应泵性能。小流量工况下，大叶顶间隙泵的熵产损失低于小叶顶间隙泵，随着IGVF增加，该差值越大;气液两相泵内的熵产主要由脉动速度引起，其次是壁面熵产，时均速度引起的熵产几乎可忽略。叶轮流道内的旋涡区、气相聚集区、高熵产区以及叶片正背面压差较小的区域位置一致，均位于叶轮叶片中间位置的压力面附近;在叶顶间隙射流的作用下，叶顶间隙越大，这些区域的面积越小。小IGVF时，两个不同叶顶间隙泵叶轮的面平均含气率大小接近;随着IGVF增加，小叶顶间隙泵的面平均含气率总是高于大叶顶间隙泵。因此，在气液两相泵中，叶顶间隙结构可在叶轮内形成高速射流，进而对流场内的不均匀气液两相流形成冲击，使流场混合得更加均匀，泵内介质可更加顺畅地流出叶轮，提高泵的运行稳定性。
Influence of Blade Tip Clearance on Gas-Liquid Two-phase Flow under Offset Load Conditions of Mixed Flow Pumps
When the gas-liquid two-phase flow pump deviates from the design conditions,especially when operating under low flow rate conditions,the boosting capacity suddenly decreases with the increase of inlet gas volume fraction(IGVF),and the pump accompanies by severe vibration.Numerical simulation is used to investigate the law of gas-liquid two-phase flow of three-stage multiphase pumps with blade tip clearances(BTC)of 1.0 mm and 1.7 mm under offset load conditions.The numerical simulation results of external characteristics and tip leakage vortices is compared with experiments,and it is found that the numerical model used in this study can accurately reflect the performance of the pump.Under low flow rate conditions,the entropy production loss of the large tip clearance pump is lower than that of the small tip clearance pump,and the difference in entropy production increases with the increase of IGVF.The entropy production in gas-liquid two-phase pumps is mainly caused by pulsating velocity,followed by wall entropy production,and the entropy production caused by time averaged velocity can be almost ignored.The positions of vortex zone,gas-phase accumulation zone,high entropy production zone and the area with lower pressure difference between the pressure surface and suction surface of the blade in the impeller flow channel are consistent,which are located near the pressure surface in the middle of the impeller blade.Under the action of jet flow in the tip clearance,the larger the tip clearance,the smaller the area of the unstable flow region.When the IGVF is small,the value of average GVF on the impeller cross-section of two pumps with different tip clearances is similar.As the IGVF increases,the value of average GVF of the small tip clearance pump is always higher than that of the large tip clearance pump.Therefore,in gas-liquid two-phase pumps,the blade tip clearance structure can create an impact on the non-uniform gas-liquid two-phase flow in the convection field through the high-speed jet formed inside the impeller,resulting in a more uniform mixing of the flow field,allowing the medium inside the pump to flow out of the impeller more smoothly and improving the stability of the pump operation.
Mixed flow pumpGas-liquid two-phase flowNumerical simulationTip clearance sizeFlow law
万方数据
维普
