The determination of pressure profiles in oil ring seals considering the influence of temperature gradients in the sealing fluid

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Virginia Tech

The analysis of ring type seals is of great concern for the designer of high speed and high pressure centrifugal compressors. Computers now play a major role in allowing for a quick evaluation of the floating ring seal. Since the accuracy of the rotor shaft stability evaluation depends on the validity of the dynamic seal characteristics, every step in the evaluation must be carefully scrutinized and updated to include the latest in theory and practical operating experience. This thesis presents the theory and results of one such extension to the current published analysis of oil ring seals. The new analysis includes the influence of the sealing fluid temperature gradients on the leakage flow rate and seal dynamic characteristics for multi-ring and/or multi-land ring configurations. Using classical short bearing theory but allowing for temperature and pressure dependent viscosity variations across the seal, the resulting pressure profiles have been determined numerically utilizing a finite difference solution technique. This thesis discusses the method used to calculate the flow and pressure profiles for oil seals, their influence on the seal dynamic characteristics, and the importance of their consideration on actual turbomachinery stability.