| The variable transmission mechanism is the core transmission component of a helicopter configuration.There are various kinematic pairs in the system such as gears and bearings.To reduce the friction and wear of the kinematic pairs and carry away heat in time,a reasonable lubrication system needs to be designed.For the transmission system with planetary structure and high speed,jet lubrication is usually adopted and the performance of the lubrication system will directly affect the working performance of the transmission system.Therefore,it is of great significance to carry out relevant researches on the design of the lubrication system of the planetary transmission system and the performance analysis of the lubrication system for improving the lubrication effect of the variable transmission system.In this paper,the planetary transmission mechanism of a helicopter is taken as the research object,the type of friction pairs inside the mechanism is analyzed,according to the heat generation of the friction pairs and the structural characteristics of the mechanism,the lubrication system is designed.CFD software Fluent is used to conduct relevant simulation researches on the flow field characteristics of the rotating oil passage in the lubrication system and the performance of the sealing structure of the rotating feed-through,and the structure is optimized according to the results.The main research contents are as follows:(1)The friction pairs inside the variable transmission system are analyzed,the power losses and heat generation for different types of friction pairs are studied,then the demand amount of lubricating oil of each friction pair is calculated according to the heat generation.Based on the oil demand and structural characteristics of the transmission mechanism,the lubrication scheme is preliminarily designed.The calculation process is parametrically programmed using Python language,and the corresponding GUI calculation interface is designed.(2)The simulation model of the rotating oil passage is established,and monitoring surfaces are set to monitor the oil flow rate at the inlet and outlet of the oil passage.The structure of the initially determined lubrication scheme is optimized through simulations to meet the oil requirements of each friction pair.Simulations are carried out for different working conditions and the change curves of oil flow rate and velocity distribution of each inlet and outlet are obtained.The effects of rotational speed and oil supply pressure on the oil flow rate and velocity distribution of each inlet and outlet of the rotating oil passages are analyzed.(3)The structure of the rotating feed-through is designed to realize the oil supply from the external oil tank to the rotating oil passage and the simulation model of the sealing structure of the rotating feed-through is established.The structural parameters and working conditions of the rotating feed-through are changed respectively,and the influences of the sealing clearance,sealing length,sealing diameter,oil supply pressure and rotating speed on the leakage amount of the seal are obtained and analyzed.The related optimizations are carried out for the improvement of uneven pressure distribution inside the seal structure.(4)A test platform for the lubrication performance test of the rotating oil passage is designed and built.The lubricating oil of each outlet of the oil passage is collected through the oil collecting device.By changing the oil supply pressure and rotation speed respectively,the curves of oil flow rate of each outlet under different working conditions are obtained,which are compared with the corresponding simulation results to verify the feasibility of the simulation method and the correctness of the results,and the average error is less than 15%. |
