Research On Characteristics Of Axial Thrust Equalizing Mechanism For Cryogenic Submerged Pump

As a new type of pump to transfer cryogenic liquid, cryogenic submerged pump is widely used in industries like the liquefied natural gas industry, because of the advantages of safety, no leakage, high reliability with the special structure and working mode. The thrust equalizing mechanism (TEM) can ensure the reliability of the pump by eliminating axial thrust loads, which dramatically increase the life of bearing and other important components. To get a reliable TEM for cryogenic submerged pump, more technical problems should be concerned, such as the temperature change of liquid being handled and the axial stiffness of the TEM. This paper focused on the research of the balance performance of TEM, and the result can provide the basis theory guide for the optimization of TEM.Analysis and calculation of the axial force in cryogenic submerged pump are studied, and put forward the TEM with improved structure including the gap seal-balancing disk(GS-BD), labyrinth seal-balancing disk(LS-BD) and labyrinth seal-spiral grooved balancing disk(LS-BD). The internal flow characteristics of the three TEM were investigated employing the ANSYS-Fluent software. Physical parameters like pressure, velocity and temperature distribution, and performance parameters like anti axial thrust, axial stiffness, remained available anti axial thrust, leakage rate, etc. were studied. The results show that the LS-BD and GS-BD can reduce the leakage rate and increase the axial stiffness, which can increase the efficiency and stability of the pump. In addition, the LS-SGBD can generate significant axial stiffness and anti axial thrust in a certain axial gap range, which can avoid contacting and ensure the reliability of cryogenic submerged pump.The influence of structure parameters including labyrinth seal, spiral groove and the main part on balance performance were studied respectively. The result shows that, the parameters of the main part have the greatest influence on the balance performance under normal working condition, the parameters of labyrinth seal can optimize the balance performance, and the parameters of spiral groove have a decisive role on the hydrodynamic force when the axial gap is very small.Different TEM specimens for testing were designed and manufactured. The influence of parameters of labyrinth seal and working condition on balance performance were studied by experiment. The testing result is similar to the numerical result previously determined, which indicates that the numerical calculation is believable.The research on the balance performance of TEM in cryogenic submerged pump can provide the basis theory guide for the optimization of TEM.