Browse Publications Technical Papers 2019-26-0082
2019-01-19

Prediction of Oil Flow inside Tractor Transmission for Splash Type Lubrication 2019-26-0082

Automotive transmissions convert power from the engine into the optimum drive force and engine speed, and to transmit this drive force to the driveshaft. Structural components of the transmission get damaged or degraded due to wear and heat. Effective lubrication prevents this metal to metal contact. In addition, the lubricants also act as a thermal medium to effectively dissipate the heat produced due to frictional resistances. In many cases, it is not possible to adequately study oil flow even in physical tests due to the adherence of oil to the internal walls of the housing, excessive foaming of the oil and the obscuring of the flow by parts. Simulations provides an insight to the designer about the lubrication pattern, around the gear and housings otherwise challenging to analyze during actual test. This paper, provides a rapid and accurate methodology for tractor transmission to visualize the splashing pattern & oil reach to the bearing. 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. VOF multi-phase flow model and dynamic meshing to simulate the fluid flow during dip (splash) lubrication within a mating gear box. Lubrication oil dynamics and oil surface interaction with the air is modeled using VOF multi-phase approach. The gear motion is imparted through dynamic mesh technique, it automatically re configures the mesh for the space in accordance with the rotation of physical objects For high speed forward boundary condition, volume fraction of oil at the at the oil pockets that carry the oil of the bush & the gear sitting interface, reveled two locations on drive shaft and driven shaft. By volume the quantity was very less or next to negligible when compared to the other gear. The supply of lubricant to the sleeves depends on the location of oil supply hole and teeth helix. In actual testing after running the transmission for 150 hrs. in 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 sleeve. Estimating the lubrication in advance during the design step helps reduce the development period, to reduce expenses for prototypes. Furthermore, the information about the internal fluid dynamics of the differential system should help the designers in the optimization of not only the lubrication but also the heat dissipation. Simulation result were in good agreement with the test results.

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