The mainstream flow past the stationary nozzle guide vanes and rotating turbine blades in a gas turbine creates an unsteady nonaxisymmetric variation in pressure in the annulus, radially outward of the rim seal. The ingress and egress occur through those parts of the seal clearance where the external pressure is higher and lower, respectively, than that in the wheel-space; this nonaxisymmetric type of ingestion is referred to here as externally induced (EI) ingress. Another cause of ingress is that the rotating air inside the wheel-space creates a radial gradient of pressure so that the pressure inside the wheel-space can be less than that outside; this creates rotationally induced (RI) ingress, which—unlike EI ingress—can occur, even if the flow in the annulus is axisymmetric. Although the EI ingress is usually dominant in a turbine, there are conditions under which both EI and RI ingress are significant, these cases are referred to as combined ingress. In Part I of this two-part paper, the so-called orifice equations are derived for compressible and incompressible swirling flows, and the incompressible equations are solved analytically for the RI ingress. The resulting algebraic expressions show how the nondimensional ingress and egress vary with , which is the ratio of the flow rate of sealing air to the flow rate necessary to prevent ingress. It is shown that , the sealing effectiveness, depends principally on , and the predicted values of are in mainly in good agreement with the available experimental data.
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July 2011
Research Papers
Prediction of Ingestion Through Turbine Rim Seals—Part I: Rotationally Induced Ingress
J. Michael Owen
J. Michael Owen
Department of Mechanical Engineering,
University of Bath
, Bath BA2 7AY, UK
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J. Michael Owen
Department of Mechanical Engineering,
University of Bath
, Bath BA2 7AY, UKJ. Turbomach. Jul 2011, 133(3): 031005 (9 pages)
Published Online: November 12, 2010
Article history
Received:
July 23, 2009
Revised:
August 7, 2009
Online:
November 12, 2010
Published:
November 12, 2010
Connected Content
A companion article has been published:
Prediction of Ingestion Through Turbine Rim Seals—Part II: Externally Induced and Combined Ingress
Citation
Owen, J. M. (November 12, 2010). "Prediction of Ingestion Through Turbine Rim Seals—Part I: Rotationally Induced Ingress." ASME. J. Turbomach. July 2011; 133(3): 031005. https://doi.org/10.1115/1.4001177
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