Research On The Lubrication And Sealing Characteristics Of The Secondary Gearbox Of Rail Vehicles

As one of the core components of the transmission system,the gearbox plays an extremely important role in the smooth and safe operation of rail vehicles.When the gearbox is working,it will generate a lot of heat and unevenly distributed high-pressure gas-liquid mixture,which requires high lubrication and sealing performance of the gearbox.Rail vehicles have the characteristics of heavy load,wide driving speed range,and large changes in working conditions,which are likely to cause poor lubrication and seal failure of the gearbox.In recent years,the computational fluid dynamics(CFD)has become a popular method for the study of the internal flow field characteristics of the gearbox.The structure of the secondary gearbox of a certain type of rail vehicle studied in this paper is complex,and it has the characteristics of gear train rotation,two-phase flow and small gear meshing clearance.The traditional finite element method has many problems in model processing,algorithm selection,mesh division and computational workload.These make visual simulation analysis difficult.Based on full investigation and a large number of preliminary calculations and analysis,this paper proposes to use the moving particle semi-implicit method(MPS)to simulate and analyze the gearbox splash lubrication,carry out experimental verification and regular exploration,and provide guidance and reference for the evaluation and optimization of the lubrication system.Based on the Mixture two-phase flow model,the sealing characteristics of the input/output shaft of the gearbox are analyzed and studied with the small droplets of lubricating oil and the ideal gas mixture as the medium.Firstly,the basic principle of the MPS method is explained.Including control equations,kernel functions,gradient models and Laplace models,time step standards,boundary conditions,and algorithm flows.Based on the existing research on the exhausted gear transmission,the calculation model of the oil supply demand in the Hertz contact area of the gear transmission is derived and established.Secondly,taking the FZG gear efficiency test rig as the research object,the same geometric model is established,and the MPS method is used for numerical simulation.Comparing the simulation and test results,it is proved that the MPS method can well represent the detailed characteristics of the flow field flow,more accurately show the velocity distribution cloud map of the particles,and have a good predictive effect on the distribution of the lubricating oil flow field.For the gear churning power loss,the error between simulation and test results is not more than 30%,with a certain degree of accuracy,which can provide a new and convenient method for the prediction of torque loss.Thirdly,the MPS method was successfully applied to the visual simulation of splash lubrication of complex geometric model gearboxes,realizing the full model simulation analysis under the influence of multiple factors such as speed,initial lubricating oil volume,and temperature.The characteristics of the flow field in the gearbox are qualitatively analyzed by extracting the cloud map of velocity,pressure and trace distribution,and the unreasonable structure of the gearbox is optimized.Analyzed the time domain change of oil particle number in the gear meshing contact area and the oil supply state.It is found that the four vehicle conditions all meet the oil supply demand.The higher the initial liquid level,the more sufficient oil supply is.The lubrication effect is better under the temperature conditions of 40℃ and 60℃.Analyzed the gear churning power loss and the proportion of power loss of each gear,and found that the power loss increased with the increase of speed and initial oil volume,and decreased quickly with the rise of temperature.Under each working condition,the sum of the power loss of gear 1 and gear 2 dominates,reaching76-99.5% of the total power loss.Finally,for the gearbox input/output shaft sealing system,the sealing mechanism is simulated and analyzed.Taking seal leakage as an indicator,the influence of pressure difference,rotor speed,medium parameters,ambient temperature,and radial seal clearance on the performance of labyrinth seals is analyzed.The results show that the leakage of the labyrinth seal increases with the increase of the inlet and outlet pressure difference,and is approximately linear;with the increase of the rotor speed,it shows a downward trend.When the speed exceeds a certain threshold,the leakage gradually stabilizes.It increases with the increase of the volume fraction of the lubricating oil droplets,and the change of the droplet diameter basically has no effect on the leakage.It increases rapidly with the increase of operating temperature and radial seal gap.