A simple method, for both estimating circumferential pressure variation in a turbine, and using this method to calculate the annulus flow ingested across a rim seal into the disc cavity, is presented. This method is compared with test data from 2 separate experimental programmes. The model is shown to collapse the majority of the test data well; with calibration it could form the basis of a preliminary design methodology. The model does not collapse data where unsteady pressure fluctuations were measured in the cavity, suggesting these fluctuations, when present, play an important role in determining how much annulus gas is ingested into the cavity.
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