This study introduces a method to examine the flow path of the lubricant inside a transmission housing of a tractor. A typical gearbox has several loads bearing elements which are in relative sliding motion to each other which causes heat to be released. The major sources of friction as well as heat are the meshing teeth between gears (sun/planet, planet/ring & power/range drive gear), thrust washers, thrust bearings and needle roller bearings. The churning of oil performs the vital function of both lubricating these sliding interfaces and cooling these sources of heat, thereby preventing failure of the gearbox.
In this paper, we have applied VOF multiphase flow model and sliding meshing to simulate the fluid flow during splashed lubrication within a mating gear box. Lubrication oil dynamics and oil surface interaction with the air is modeled using VOF multiphase approach. The gear motion is imparted through sliding mesh technique, it automatically reconfigures the mesh for the space in accordance with the rotation of physical objects, which divides the space around the gears, centering on the axis of rotation to simulate the motion of the gears. The method captures the effect of rotation of the gears and shaft in a transmission. The entire transmission unit is considered for the analysis to study the cumulative effect of the motion of all the gears on the oil flow against the general practice of studying the local effect.
After solving for 3 seconds in high speed forward boundary condition, volume fraction of oil at the at the oil holes that carry the oil to the bush & the gear interface, reveled two locations one on the fourth gear of drive shaft and another at the first gear of the driven shaft. By volume the quantity was very less when compared to the other gear. The supply of lubricant to the bush & gear interface depends on the location of oil supply hole on the gears and shafts. After running the transmission for 150 hours on test bed scoring marks were observed between the gears inner diameter & bush outer diameter due the relative motion between the inner surfaces. This failure was attributed to scarcity & delay of oil to bush. Estimating the lubrication in advance during the design step helps reduce the development period & expenses for prototypes. This paper explains how the CFD simulation can we used to understand the lubrication flow inside the tractor transmission.