Numerical Calculating On Axial Force And Cavitation Flow Analysis Of Liquid Oxygen Turbo Pump

Turbo pump offers propellant continuously to rocket engine with high rotating speed and is the key power device. Because of the high rotating speed, pump shaft would bear a great deal of axial force, which threats the safety of pump. Meanwhile due to the cryogenic characteristics of LOX, cavitation would have an obvious impact on pump fluid. This dissertation investigated the influence of balance piston axial clearance on axial force of a turbo pump with CFD method, revealed the initial reasons of flow field caused by structure changing to axial force and concluded the rule of axial clearance to axial force. In the analysis of cavitating flow, the effects on pump performance and flow of cavitation were shown based on comparison between different cavitation conditions. The main contents of this research are as follows.Firstly, pump flow states with different mass flow conditions at fixed axial clearance were simulated with SST turbulent model integrated in CFX commercial software. Based on the calculation results, rule of balance piston axial clearance to axial force was concluded and the flow factors such as velocity v ector, pressure were analyzed to display axial force changing characteristics.Secondly, the different axial forces at different axial clearance structure were calculated andthe axial force changing characteristics were compared due to axial clearance changing. This research showed the working principle of balance piston and law of axial force changing from aspects of velocity vector, pressure contour and eddy structure, which could guide axial force estimation.Finally, the Zwart-Gerber-Belamri cavitation model was adopted to regulate turbo pump cavitating flow, then the results of different cavitation conditions were compared. Based on the comparisons, the impacts of cavitating flow on pump flow field were displayed on the points of cavitation region, angle of attack and transient eddy structure.According to the research, some conclusions can be obtained. The component axial force on the back impeller shroud determines the direction and value of pump axial force. With Δ-0.3mm structure, high pressure clearance of balance piston widens while low pressure clearance narrows. So the pressure of balance chamber decreases overall and axial force orients to pump outlet mainly. When pump is Δ+0.3mm structure, the high pressure clearance narrows and low pressure clearance widens. On the contrary, the pressure of balance chamber increases then axial force orient to pump inlet. The direction changing of axial force is the reason why the balance piston realizes automatic balance of axial force. The analyses of cavitating flow demonstrate that distribution of cavitation is restricted to the leading edge of blades at first and then expands in suction chamber with extensive cavtiating flow. For angle of attack of blades, cavitation can soothe the impact of fluid. Analyzing of eddy structure illustrates cavitation could engender server swirling flow and this eddy consequence is one of important reasons affecting pump performance.