SUMMARY

The objective of this project is the development of a numerical model of a generalized reciprocating hydraulic rod seal, including mixed lubrication and surface roughness. Such model is capable of predicting the key seal performance characteristics, especially net leakage and friction force. It allows evaluation of potential seal designs, and would stimulate the development of new and innovative seal concepts. Since at least 1964, serious research on reciprocating rod seals have been performed, but the impact on the practical aspects of seal design is not significant. The reason for this is that all previous analytical seal models make two key assumptions: full film lubrication and perfectly smooth sealing surfaces. Experimental studies have shown, however, that mixed lubrication occurs over a wide range of conditions, and surface roughness plays an important role in the lubrication of these seals. Previous seal models do not take account of these important aspects. The proposed model is intended to be applicable to both elastomeric and non-elastomeric (e.g. PTFE) rod seals, and primarily simulates the physical processes in the sealing zone. Since the rod roughness is generally much smaller than the sealing element roughness, the surface of the rod is assumed as perfectly smooth while the surface of the sealing element is considered to be rough. Both full film lubrication and mixed lubrication are considered. The model is comprised of coupled steady state fluid mechanics analysis, deformation mechanics analysis, contact mechanics analysis and thermal analysis with an iterative computational procedure. The model is validated through comparisons of model predictions with experimental measurements and observations.