Thermal Analysis Of The Helicoper Main Gearbox System

The helicopter main speed reducer is the core part of helicopter’s power transmiting system, andit is also the main load-bearing parts in the system, it is directly under the force and torque whichcome from the rotor and passes them to the body of the helicopter. However, even under the goodlubricating conditions, the temperature rise of the main reducer is great because of compact innerspace, high rotational speed of axis and high power density. It could cause serious damages of thetranmiting system and then treats to the flight safety of helicopters. The temperature distributionanalysis and calculation of the gears, bearings and shells have great significance: it can provideoptimizations for the structural design of the main gear box and transmission-system design of thehelicopter; improve the lubrication system in order to raise the reliability; ultimately give some helpto promote China’s helicopter development, and manufacturing industry.This paper contains the following aspects of the research content: analysis and calculation of theheat sources which belong to the bearings and gears in the helicopter main gearbox. The present thesisis aim at the study on following topics, such as determinate the power density of fricational knematicpairs belong to the bearings and gears and other friction interface surface in the helicopter mainreducers. Different models of heat current power for the friction pairs are selected according to theloss of frictional power, and then the suitable using conditions are discussed. The models for gear’swindage loss and hydrodynamic loss are built too.The computational models for heat transfercoefficient in the surface of accessory based on the theory of heat transfer are established, includingthe ones between surface of gears and fuel-air mixture. The models for heat transfer coefficient ofconvection in the surface of components based on the theory of heat transfer are studied, such as thetransfer coefficient between boundary of gears and fuel-air mixture.The thermal network method andthe finite volume method are used to analyse the steady and transient temperature distribution of therings of high-speed rotating ball bearing, and then the load, speed and other influencing factors on thebearing temperature rise are discussed. On the basis of preceding study, the heating transfer among themain reducer is analysed, and then a thermal network for heat transfer in the reducer is established.An interactive interface and valuce calculating program are developed by the use of MATLABlanguage, by which the steady and transient temperature distribution of main reducer could becalculate. At last experimental work was carried out, temperatures of ball bearing are measured on aBL bearing dynamic performance testing rig. The results of experiment and theory are compared with each others and showed good agreement.