Flow Field Analysis And Optimization Of Ultra-low Temperature High Speed Heavy Load Ball Bearing Tester

Ultra-low temperature and high-load heavy-duty ball bearings are important parts in the large thrust liquid rockets in the aerospace field.At this stage,there are still some technical shortcomings in China to accurately study the internal flow and heat transfer of the flow field of the ultra-low temperature heavy-duty bearing tester from the perspective of numerical simulation.In view of the problems at this stage,this thesis established a finite element research model of the bearing tester to solve the known problems,predict the internal pressure and temperature distribution of the flow field,and improve the design of the bearing tester through the results of numerical simulation Provide evidence.The main research contents are as follows:(1)Establishment of finite element calculation model of bearing clearance flow field.The velocity field and pressure field are analyzed by numerical simulation results of bearing clearance flow field with different grid types.It is concluded that the hexahedral mesh can capture the vortices in the flow field more accurately than the tetrahedral mesh.However,the computation time is longer and the consumption is larger than the tetrahedral mesh flow field.Based on the standard k-epsilon turbulence model,the RNG k-epsilon turbulence model and realizable k-epsilon turbulence model of the three turbulence model of bearing clearance flow field numerical analysis of pressure field simulation results are basically the same,but the standard k-epsilon turbulence model for the flow field inside the speed of rotation and the analysis of the bending can't very good,and RNG k-epsilon turbulence model in three kinds of turbulence model in the simulation effect is better.(2)The structure of the flow guide area in the chamber of the tester was optimized.Taking the fluid guide cavity of the upper liquid nitrogen cavity in the ultra-low temperature high speed heavy load ball bearing tester as the object model,the fluid path and cavity structure in the guide area are improved and optimized finally,and the expected effect is achieved.The numerical simulation results show that the higher the position of the diversion head,the larger the diameter of the flow path and the larger the velocity in the flow field.However,the increase of velocity leads to vortex in the flow field,and the pressure in the flow field changes greatly.Under the condition that the side of the guide head is changed into a curve,the velocity in the flow field is basically the same as that in the straight line of the side of the guide head,and the vortex area in the flow field is relatively less,which not only ensures the speed of liquid nitrogen rushing through the bearing,but also makes the pressure change in the cavity smaller.Under the design principle of minimizing the negative pressure,the numerical simulation results of the middle position of the guide head and the curve structure on the side of the guide head are better.(3)The finite element model of the whole structure of the ultra-low temperature high speed heavy load ball bearing tester is established.The whole structure is divided into upper liquid nitrogen cavity and lower lubrication cavity.The velocity field,pressure field and temperature field of these two cavities are obtained,and the distribution law of the overall flow field is analyzed to some extent.It is concluded that the internal velocity field of liquid nitrogen cavity and lubricating cavity is greatly affected by the rotation of the axis in the intermediate region.The pressure field in the liquid nitrogen cavity is evenly distributed,and the pressure at the inlet of the flow field is large.However,when passing through the bearing clearance flow field,the pressure value is higher because the bearing clearance flow field shrinks.When passing through the bearing clearance flow field,the pressure will be reduced to a certain extent because of the labyrinth sealing structure in the cavity.The inlet pressure is large in the lubrication chamber,and then the pressure decreases steadily.(4)In the temperature field,the temperature field in the liquid nitrogen cavity is relatively uniform on the whole.However,when the liquid nitrogen flows near the bearing,the heat emitted by the bearing friction causes the cavity to start heating up to 224K,and the liquid nitrogen medium will move the bearing friction up to the tropics,so as to ensure that the ball heating will not lead to wear.In the lubrication chamber,the temperature of the lubricating oil flowing through the upper low temperature wall surface begins to decrease significantly,and the temperature drops as low as 225K.It does not reach the freezing point of the lubricating liquid and will not cause the phenomenon that the lubricating liquid solidifies and affects the lubrication.In this thesis,ANSYS FLUENT software is used to analyze the flow field of bearing clearance,the flow field of flow diversion area of bearing tester and the flow field of integral bearing tester by numerical simulation.The reliability of bearing clearance flow field is improved,and the efficiency is improved by improving the structure of guide area.The pressure and temperature fields of the flow field of the whole bearing tester are simulated,and the results are reasonable.