Multi Scale Simulation Model for Temparature Prediction of Radial Lip Seals

弹性径向唇形密封件用于密封旋转轴。在运行过程中，径向唇形密封与轴之间的接触区域会产生摩擦热。产生的摩擦热越多，散热越差，接触区域就越热。高温对密封系统危害极大。它们极大地加速了唇形密封弹性体和润滑剂的老化，并导致密封系统更快地失效。为了提供密封系统所需的可靠性，在运行期间温度必须保持在允许的范围内。因此，设计者必须能够估计已经处于开发阶段的密封触点的温度。目前的估算大多基于经验和专家经验，由于影响摩擦热产生和散热的因素众多且相互作用，因此会产生相当大的误差。这些估计误差的后果是密封系统尺寸过大(这意味着不经济)或大量故障。因此，在本研究项目中，开发了一个模拟摩擦热产生和散失的仿真模型。该仿真模型可以计算出密封系统及其周边的温度分布，并采用多尺度的概念，有效地解决了不同长度尺度上的影响。模拟模型在微观尺度上描述了摩擦热的产生，在宏观尺度上描述了摩擦热的散失。编制了FORTRAN程序作为微观模型，利用雷诺方程描述流体在动压密封间隙中的流动。仿真模型采用了径向唇形密封和轴的真实表面形貌。宏观模型采用现有的共轭换热模型。该模拟模型允许将流体流动和热模拟结合起来。对密封系统的流体区和固体区的换热进行了计算，采用宏微观模型耦合迭代求解的方法解决了产热与散热的相互作用。通过将仿真结果与多用途试验台上的大量试车结果进行比较，对整个仿真模型及其部件进行了验证和优化，并利用验证后的仿真模型进行了参数研究，以确定影响接触区温度的因素及其相互作用。在参数研究和验证实验结果的基础上，提出了一种预测发展阶段接触温度的近似方法。

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.