| With the high-speed rotation of the impeller,the gas-liquid two phase flow in the liquid-ring pump presents a gas-liquid separation state,forming a free interface.Because of the pressure difference between the impeller and the lateral cover plate,there will form gas-liquid two phase leakage flow.The leakage flow interacts with the main flow,reducing the hydraulic performance of the pump.Due to the asymmetric characteristics of the pressure field distribution along the circumferential direction,the tip clearance leakage flow has complex spatiotemporal characteristics.For the above reasons,this paper analyzes in detail the leakage flow structure and its complex spatiotemporal distribution characteristics of the liquid-ring pump axial tip clearance based on numerical simulation methods and experimental verification.The designs such as micro-jet,winglet,squealer,winglet-jet composite tip and winglet-squealer composite tip were introduced into the axial blade tip.The suppression effect and mechanism of different blade tip structures on leakage flow were studied,and the best method to suppress axial clearance leakage flow was found.The main work and research results are as follows:1.The liquid-ring pump experimental setup was built,and the accuracy of the numerical simulation method was verified by the hydraulic performance of the liquid-ring pump and the experimental results of high-speed camera.Based on this numerical simulation method,the gas-liquid two phase leakage flow under the design condition of the gas mass flow rate of 0.07kg/s was studied and analyzed.The results show that the gas-liquid two phase leakage flow of the liquid-ring pump has complex spatiotemporal distribution characteristics along the circumferential direction.In the suction zone,the leakage flow gradually decreases from hub to rim,and the leakage flow intensity gradually increases along the rotation direction of the impeller.The gas leakage velocity of compression zone is the highest,and the leakage flow intensity gradually increases along the rotation direction of the impeller.In the exhaust zone and the transition zone,the reverse leakage flow is formed near the hub,which flows from the clearance suction side to the pressure side.The intensity of leakage flow decreases gradually from the hub to the rim.Near the rim,the leakage flow direction changes,flowing from pressure side to suction side.The liquid leakage flow amount at the end of the suction zone and the exhaust zone of the liquid-ring pump is the largest.The intensity distribution of pressure pulsation in the axial clearance is similar to leakage flow.The low-frequency energy value in the axial clearance is larger at the end of the suction zone and the beginning of the exhaust zone.2.The micro-jet design was introduced into the axial blade tip of the liquid-ring pump.The micro-jet was used to suppress the axial clearance leakage flow,and its suppression mechanism was analyzed.The results show that the high-pressure fluid on the pressure surface of the blade will flow into the clearance flow channel through the jet hole at an angle perpendicular to the leakage flow after introducing the micro-jet design.The leakage flow occupies part of the axial clearance flow channel and blocks the clearance flow channel,thus reducing the intensity of the leakage flow in the axial clearance of the liquidring pump.Compared with the numerical simulation results of the prototype pump,under the three working conditions of 0.02 kg/s,0.04 kg/s and 0.07 kg/s,the total liquid leakage flow amount of the micro-jet liquid-ring pump decreased by 7.9%,8.4% and 10.5%respectively,and the inlet vacuum increased by 2.2%,2.4% and 3.8% respectively.3.The blade tip squealer was introduced into the axial blade tip of the liquid-ring pump.The flow structure in the squealer and its suppression mechanism on the leakage flow were studied.The results show that the leakage flow interacts with the low-velocity fluid in the squealer,forming pressure side squealer corner vortex and squealer vortex with opposite rotation directions in the squealer.The pressure side squealer corner vortex and the squealer vortex have strong shear effects,blocking the axial clearance flow channel,thus suppressing leakage flow.For liquid leakage flow,with the leakage flow velocity gradually decreases,the intensity of the pressure side squealer corner vortex gradually decreases.The intensity of the squealer vortex gradually increases,and the shear effect between the pressure side squealer corner vortex and the squealer vortex increases,which improves the suppression effect of the squealer on liquid leakage flow.Compared with the prototype pump,the total liquid leakage flow amount of the squealer liquid-ring pump decreased by 10.7%,12.4% and 13.8% respectively,and the inlet vacuum increased by2.4%,2.9% and 4.1% respectively under three working conditions.4.The winglet design was introduced into the axial blade tip of the liquid-ring pump.The impact of different installation positions on its leakage flow suppression effect and the suppression mechanism were analyzed.The results show that the winglet extends the flow channel of axial clearance and reduces the pressure difference between the two sides of the clearance,thus suppressing the leakage flow.After flowing out of the clearance,the leakage flow of the suction surface winglet interacts with the boundary layer fluid under the winglet,forming the wing corner vortex under the winglet,which causes additional losses.Compared with the prototype pump,the total liquid leakage flow amount of the suction surface winglet liquid-ring pump decreased by 8.7%,9.2% and 11.2% respectively,and the inlet vacuum increased by 2.4%,2.9% and 4.1% respectively under three working conditions.The total liquid leakage flow amount of the pressure surface winglet liquidring pump decreased by 13.1%,14.0% and 16.5% respectively,and the inlet vacuum increased by 2.7%,3.2% and 4.7% respectively.The hydraulic performance of the pump is improved more obviously by the pressure surface winglet.5.The winglet-jet composite tip and winglet-squealer composite tip were introduced into the axial blade tip of the liquid-ring pump.The interaction of different blade tip structures was analyzed.The results show that for the winglet-jet composite tip,the jet hole directly leads the high-pressure fluid on the blade pressure surface into the axial clearance,which weakens the effect of the winglet on extending the clearance flow channel and reducing the pressure difference between the two sides of the clearance.Although the winglet reduces the mixing loss between the micro-jet and the leakage flow,weakening the suppression effect of the micro-jet on the leakage flow,the winglet has weakened the intensity of the leakage flow,making its suppression effect better than that of the microjet.Therefore,compared with the prototype pump,the total liquid leakage flow amount of the winglet-jet composite tip liquid-ring pump decreased by 10.2%,11.6% and 14.3%respectively,and the inlet vacuum increased by 2.4%,2.7% and 4.2% respectively under three working conditions.Its effect is better than that of micro-jet,but weaker than that of winglet.The winglet of the winglet-squealer composite tip extends the clearance flow channel and reduces the pressure difference between the two sides of the clearance.The decrease of the liquid leakage velocity makes the squealer have a stronger suppression effect on the leakage flow,thus further reducing the leakage flow velocity.Therefore,the total liquid leakage flow amount of the winglet-squealer composite tip liquid-ring pump decreased by 17.8%,18.4% and 19.8% respectively,and the inlet vacuum increased by3.5%,3.9% and 5.3% respectively under three working conditions.The winglet-squealer composite tip can reduce the pressure pulsation intensity near the axial clearance and improve the operation stability of the liquid-ring pump. 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