Use of Pressure Measurements to Determine Effectiveness of Turbine Rim Seals

The ingress of hot gas through the rim seal of a gas turbine depends on the pressure difference between the mainstream flow in the turbine annulus and that in the wheel-space radially inward of the rim seal. In this paper, a previously published orifice model is modified so that the sealing effectiveness ec determined from concentration measurements in a rig could be used to determine ep, the effectiveness determined from pressure measurements in an engine. It is assumed that there is a hypothetical “sweet spot” on the vane platform where the measured pressures would ensure that the calculated value of ep equals ec, the value determined from concentration measurements. Experimental measurements for a radial-clearance seal show that, as predicted, the hypothetical pressure difference at the sweet spot is linearly related to the pressure difference measured at an arbitrary location on the vane platform. There is good agreement between the values of ep determined using the theoretical model and values of ec determined from concentration measurements. Supporting computations, using a 3D steady computational fluid dynamics (CFD) code, show that the axial location of the sweet spot is very close to the upstream edge of the seal clearance. It is shown how parameters obtained from measurements of pressure and concentration in a rig could, in principle, be used to calculate the sealing effectiveness in an engine.

[1]  Dieter Bohn,et al.  Experimental and Numerical Investigation of the Influence of Rotor Blades on Hot Gas Ingestion Into the Upstream Cavity of an Axial Turbine Stage , 2000 .

[2]  Dieter Bohn,et al.  Experimental and Numerical Investigations of Aerodynamic Aspects of Hot Gas Ingestion in Rotor-Stator Systems With Superimposed Cooling Mass Flow , 1995 .

[3]  Roy Teuber,et al.  Experimental Measurements of Ingestion Through Turbine Rim Seals: Part 4 — Off-Design Conditions , 2013 .

[4]  A. B. Turner,et al.  Ingestion Into the Upstream Wheelspace of an Axial Turbine Stage , 1992 .

[5]  U. P. Phadke,et al.  Aerodynamic aspects of the sealing of gas-turbine rotor-stator systems: Part 3: The effect of nonaxisymmetric external flow on seal performance , 1988 .

[6]  Michael Wilson,et al.  Experimental Measurements of Ingestion Through Turbine Rim Seals—Part I: Externally Induced Ingress , 2013 .

[7]  Bruce V. Johnson,et al.  Rim Seal Ingestion Characteristics for Axial Gap Rim Seals in a Closely-Spaced Turbine Stage From a Numerical Simulation , 2006 .

[8]  John W. Chew,et al.  Rim sealing of rotor-stator wheelspaces in the presence of external flow , 1991 .

[9]  Michael Wilson,et al.  Prediction of Ingress Through Turbine Rim Seals—Part I: Externally Induced Ingress , 2012 .

[10]  Kunyuan Zhou,et al.  Statistical and Theoretical Models of Ingestion Through Turbine Rim Seals , 2013 .

[11]  Roy Teuber,et al.  Computational extrapolation of turbine sealing effectiveness from test rig to engine conditions , 2013 .

[12]  J. Michael Owen,et al.  Prediction of Ingestion Through Turbine Rim Seals—Part I: Rotationally Induced Ingress , 2011 .

[13]  Dieter Bohn,et al.  A Method for Estimating the Influence of Time-Dependent Vane and Blade Pressure Fields on Turbine Rim Seal Ingestion , 2009 .

[14]  J. Michael Owen.  Prediction of Ingestion Through Turbine Rim Seals—Part II: Externally Induced and Combined Ingress , 2011 .

[15]  Gary D. Lock,et al.  Experimental Measurements of Ingestion Through Turbine Rim Seals—Part III: Single and Double Seals , 2013 .

[16]  Kenneth Moore,et al.  A New 1.5-Stage Turbine Wheelspace Hot Gas Ingestion Rig (HGIR): Part I — Experimental Test Vehicle, Measurement Capability and Baseline Results , 2013 .

[17]  R. P. Roy,et al.  Main Gas Ingestion in a Turbine Stage for Three Rim Cavity Configurations , 2011 .

[18]  Nicholas J. Hills,et al.  Measurement and Analysis of Ingestion Through a Turbine Rim Seal , 2003 .

[19]  Bruce V. Johnson,et al.  The Flow Field and Main Gas Ingestion in a Rotor-Stator Cavity , 2007 .