Tribological Analyses and Designs of the Apex Seal-Housing  Interface in Rotary Engines

Liu, Zhong

doi:https://doi.org/10.21985/n2-gc4a-kk88

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Tribological Analyses and Designs of the Apex Seal-Housing Interface in Rotary Engines

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Lubrication is the most means for sliding interface failure prevention because it helps separate two interacting surfaces, reduce asperity contacts and thus extend the working life of the parts. Improving the tribological performance of lubricated interfaces is a challenging work, as several influence factors are involved, such as coating, plasticity, thermal effect, cavitation, and starvation. Surface texture and profile designs have been introduced to improve the tribological performances of interfaces. However, the interfacial physics behind those influence factors and the mechanisms for surface designs remain unclear. The research involved in this thesis aims to develop an advanced hydrodynamic lubrication modeling system to assist the simulation and surface designs of the apex seal-housing interface in rotary engines. This system includes: 1) the elasto-hydrodynamic lubrication model with the consideration of coating and real rough surfaces, 2) the plasto-elasto-hydrodynamic lubrication for the plastic deformation and wear analyses, 3) the thermal elasto-hydrodynamic lubrication model for the temperature analyses, and 4) the starved and cavitated elasto-hydrodynamic lubrication models for the starvation and cavitation analyses. In addition, the surface designs include 1) texture designs on the apex seal, and 2) profile designs on the housing. The major purposes of surface designs are to enhance lubrication, reduce friction, and extend the working life of the apex seal-housing interfaces in rotary engines. The major contributions of this work consist of the following: (1) film thickness and initial wear coefficient analyses for different coated surfaces, (2) a new thermal elasto-hydrodynamic lubrication model to analyze the temperature rise distribution in crowned roller contacts and a new formula to predict the optimal crown radius for minimizing the thermal effect, (3) a modified crowned roller contact elasto-hydrodynamic lubrication model that considers cavitation and starvation to investigate the influence of starved lubrication and the cavitation effect, (4) novel partial texture designs to enhance the minimum film thickness and reduce the friction coefficient in crowned roller contacts, (5) novel profile designs to obtain a more uniformly distributed film thickness and pressure, as well as an enhanced minimum film thickness in a crowned roller elasto-hydrodynamic lubrication case. The models and conclusions in this research can be used to improve the tribological performance of the apex seal-housing interface in rotary engines, and they can be applied to analyze other roller contact elasto-hydrodynamic lubrication cases. The numerical methods utilized in this work can be extended to investigate point-contact and line-contact elasto-hydrodynamic lubrication cases, and the design methods developed in this study can also be extended to other tribological applications

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