Multi Scale Simulation Model for Temparature Prediction of Radial Lip Seals

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Elastomeric radial lip seals are used to seal rotating shafts. During operation frictional heat is generated in the contact area between the radial lip seal and the shaft. The more frictional heat is generated and the poorer this heat is dissipated, the hotter the contact area gets. High temperatures are extremely harmful to the sealing system. They significantly accelerate the aging of the lip seal elastomer and the lubricant and cause faster failures of the sealing system.To provide the required reliability of the sealing system, the temperatures must stay in the allowed range during operation. Therefore designers have to be able to estimate the temperature in the sealing contact already in the development stage. Today the estimation is mostly based on experience and expertise.Considerable errors occur due to the multitude and the mutual interactions of the influencing factors on the generation and dissipation of the frictional heat. The consequences of those estimation errors are overdimensioned (this means uneconomic) sealing systems or massive failures.Therefore in this research project a simulation model is developed for simulating the production and dissipation of the frictional heat. With this simulation model the temperature distribution in the sealing system and its periphery can be calculated.A multi scale concept is used for the simulation model to solve the effects running on different length scales efficiently. The simulation model describes the production of the frictional heat on the micro scale and the dissipation of the frictional heat on the macro scale. A Fortran program is developed as micro model, which describes the fluid flow in the hydrodynamic sealing gap using the Reynolds equation. The simulation model uses real surface topographies of the radial lip seal and the shaft. An existing conjugate heat transfer model is used as macro model. This simulation model allows a combined fluid flow and heat simulation. The heat transfer is not only calculated for the fluid domains but also for the solid domains of the sealing system.To resolve the interaction of heat generation and heat dissipation, the macro and the micro model are coupled and are solved iteratively. The whole simulation model and its components are validated and optimized by comparing the simulation results with extensive test runs on a multi-purpose test rig.A parameter study is performed with the validated simulation model to identify the influencing coefficients and their interactions on the temperature in the contact area. Based on the results of the parameter study and the validation experiments, an approximation method is developed for predicting the contact temperature during the development stage.