Gearbox power transfer efficiency is a major factor in overall powertrain efficiency of a passenger vehicle. With rapidly changing emission and fuel efficiency regulations, there is a push to increase the gearbox efficiency to improve the overall fuel economy of the vehicle. In case of an existing gearbox, efficiency can be improved by using the low viscosity lubrication oil.
Despite a benefit in increasing the gearbox efficiency, lowering down the viscosity of lubrication oil gives rise to few challenges with respect to its performance. One of these challenges is breather performance which defines that transmission oil should not come out of breather pipe in some pre-defined conditions during gearbox operation. As this validation is being carried out on proto parts when the complete system is ready, failure to satisfy the defined criteria for breather performance can lead to multiple trials. This further leads to extended design cycles for launching new passenger vehicles with better transmission efficiency and fuel economy into the market. Design cycle time can be reduced by using CFD simulation techniques for oil flow simulation to predict the breather performance in the early design stage.
Current paper describes a CFD simulation method developed for virtual validation of gearbox lubrication oil breather performance using ParticleWorks software. Simulation model consists of complete gearbox system with all the gears rotating, shift system, oil flow galleries and transmission housings. Input conditions to the CFD Model are as per the actual test conditions. CFD Simulation model is validated by correlating it with the actual oil flow using cut-section into the gearbox housing. Validated model is being used to carry out virtual validation of lubrication breather system of new design.