With the recognition that seal faces are not perfectly flat and/or that nonaxisymmetric seal loading will cause seal faces to distort, there is a need to predict whether or not a leakage gap will result. If a gap does occur, it is then necessary to predict its size and circumferential variation. In this paper, a tool for predicting seal gap is developed. The method is general. Initial face profiles are arbitrary. Ring cross-sections and seal loading may vary circumferentially. The model uses the stiffness properties of a general ring finite element and couples the two rings by a series of springs which represent contact at the face. The entire problem is solved using a finite element method. The seal load is incremented so that as deflection increases, springs representing face contact are included in the problem as required. The final result is seal gap as a function of angular position or contact pressure at points where the faces touch. The model has been verified experimentally using two rings with an eccentric load which causes a gap to develop. Agreement with the experiment is good. The model is also used to predict leakage gap in some magnetically loaded commercial seals. A comparison between predicted leakage and measured leakage is made and the comparison is good. The model should find wide application in providing accurate analysis for seal leakage problems. It can be used to establish flatness guidelines as well as to show the effects of nonaxisymmetric loading on seal leakage.

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