An Investigation of Ingress for an “Air-Cooled” Shrouded Rotating Disk System With Radial-Clearance Seals

1983 ◽  
Vol 105 (1) ◽  
pp. 178-182 ◽  
Author(s):  
U. P. Phadke ◽  
J. M. Owen
Keyword(s):  
Rotating Disk ◽  
Turbine Rotor ◽  
Radial Clearance ◽  
Pressure Measurements ◽  
Clearance Ratio ◽  
Disk System ◽  
Hot Gas ◽  
Isothermal Plane ◽  
Axial Clearance ◽  
Equivalent Conditions

In order to model the flow between an air-cooled gas turbine rotor and its stationary casing, a simple isothermal plane rotating disk and stator are used. In tests reported earlier, the cavity between the rotor and stator was sealed by a stationary cylindrical shroud, and the dimensionless minimum amount of “coolant,” Cw, min, necessary to prevent a radial inflow (or ingress) of “hot gas” through the axial clearance between the shroud and the rotor, was determined. In the current tests, a number of seals with a radial clearance between the cylindrical shroud and the rotor are tested. Unlike their axial-clearance counterparts, radial-clearance seals can exhibit a pressure-inversion effect, where the pressure inside the cavity increases, rather than decreases, with increasing rotational speed. Using pressure measurements and flow visualization, correlations showing the variation of Cw, min with clearance ratio and rotational Reynolds number are presented, and it is shown that — under equivalent conditions — a seal with a radial clearance can be much more effective than one with an axial clearance.

Experimental Measurements of Ingestion Through Turbine Rim Seals—Part II: Rotationally Induced Ingress

2012 ◽  
Vol 135 (2) ◽  
Author(s):  
Carl M. Sangan ◽  
Oliver J. Pountney ◽  
Kunyuan Zhou ◽  
J. Michael Owen ◽  
Mike Wilson ◽  
...  
Keyword(s):  
Experimental Results ◽  
Radial Clearance ◽  
Rotating Fluid ◽  
Flow Rates ◽  
Hot Gas ◽  
Wide Range ◽  
The Common ◽  
Axial Clearance ◽  
Better Than ◽  
Good Agreement

Part I of this two-part paper presented experimental results for externally-induced (EI) ingress, where the ingestion of hot gas through the rim seal into the wheel-space of a gas turbine is controlled by the circumferential variation of pressure in the external annulus. In Part II, experimental results are presented for rotationally-induced (RI) ingress, where the ingestion is controlled by the pressure generated by the rotating fluid in the wheel-space. Although EI ingress is the common form of ingestion through turbine rim seals, RI ingress or combined ingress (where EI and RI ingress are both significant) is particularly important for double seals, where the pressure asymmetries are attenuated in the annular space between the inner and outer seals. In this paper, the sealing effectiveness was determined from concentration measurements, and the variation of effectiveness with sealing flow rate was compared with theoretical curves for RI ingress obtained from an orifice model. Using a nondimensional sealing parameter Φ0 the data could be collapsed onto a single curve, and the theoretical variation of effectiveness with Φ0 was in very good agreement with the data for a wide range of flow rates and rotational speeds. It was shown that the sealing flow required to prevent RI ingress was much less than that needed for EI ingress, and it was also shown that the effectiveness of a radial-clearance seal is significantly better than that for an axial-clearance seal for both EI and RI ingress.

Use of Pressure Measurements to Determine Effectiveness of Turbine Rim Seals

2014 ◽  
Vol 137 (3) ◽  
Author(s):  
J. Michael Owen ◽  
Kang Wu ◽  
James A. Scobie ◽  
Carl M. Sangan ◽  
GeonHwan Cho ◽  
...  
Keyword(s):  
Pressure Difference ◽  
Radial Clearance ◽  
Pressure Measurements ◽  
Sweet Spot ◽  
Hot Gas ◽  
Mainstream Flow ◽  
Computational Fluid Dynamics Cfd ◽  
Concentration Measurements ◽  
Arbitrary Location ◽  
Good Agreement

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 εc determined from concentration measurements in a rig could be used to determine εp, 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 εp equals εc, 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 εp determined using the theoretical model and values of εc 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.

scholarly journals An Investigation of Ingress for a Simple Shrouded Rotating Disc System With a Radial Outflow of Coolant

1980 ◽  
Author(s):  
J. M. Owen ◽  
U. P. Phadke
Keyword(s):  
Complex Geometry ◽  
Reynolds Numbers ◽  
Turbine Rotor ◽  
Pressure Measurements ◽  
Rotating Disc ◽  
Clearance Ratio ◽  
Gap Ratio ◽  
Radial Outflow ◽  
Cooling Air ◽  
Theoretical Considerations

A plane rotating disc and a plane stator with a cylindrical shroud are used to model the more complex geometry of an air-cooled gas turbine rotor. “Cooling” air, which is supplied to the center of the stator, leaves radially through the clearance between the rotating disc and a stationary shroud, and flow visualization and pressure measurements are used to determine the minimum dimensionless mass flow rate, Cw,min, of cooling air necessary to prevent the ingress of external fluid at the periphery of the system. From theoretical considerations, the results are correlated (for a gap ratio of G = 0.1, shroud clearance ratio between Gc = 0.0025 and Gc = 0.04, and rotational Reynolds numbers between Reθ = 2 × 105 and Reθ = 106) by Cw,min = cGcnReθ

Effect of Ingestion on Temperature of Turbine Disks

2013 ◽  
Vol 135 (5) ◽  
Author(s):  
Oliver J. Pountney ◽  
Carl M. Sangan ◽  
Gary D. Lock ◽  
J. Michael Owen
Keyword(s):  
Heat Transfer ◽  
Flow Rate ◽  
Rotating Disk ◽  
Thermochromic Liquid Crystal ◽  
Hot Gas ◽  
Nusselt Numbers ◽  
Turbine Disks ◽  
Adiabatic Effectiveness ◽  
Axial Clearance ◽  
First Time

This paper describes experimental results from a research facility which experimentally models hot-gas ingress into the wheel-space of an axial turbine stage with an axial-clearance rim seal. Thermochromic liquid crystal (TLC) was used to determine the effect of ingestion on heat transfer to the rotating disk; as far as the authors are aware, this is the first time that the measured effects of ingestion on adiabatic temperature have been published. An adiabatic effectiveness for the rotor was defined, and this definition was used to determine when the effect of ingress was first experienced by the rotor. Concentration measurements on the stator were used to determine the sealing effectiveness of the rim seal, and transient heat transfer tests with heated sealing air were used to determine the adiabatic effectiveness of the rotor. The thermal buffer ratio, which is defined as the ratio of the sealing flow rate when ingress first occurs to that when it is first experienced by the rotor, was shown to depend on the turbulent flow parameter. The local Nusselt numbers, Nu, which were measured on the rotor, were significantly smaller than those for a free disk; they decreased as the sealing flow rate decreased and as the ingress correspondingly increased. The values of Nu and adiabatic effectiveness obtained in these experiments provide data for the validation of CFD codes but caution is needed if they (particularly the values of Nu) are to be extrapolated to engine conditions.

Experimental Measurements of Ingestion Through Turbine Rim Seals: Part 2—Rotationally-Induced Ingress

2011 ◽  
Author(s):  
Carl M. Sangan ◽  
Kunyuan Zhou ◽  
J. Michael Owen ◽  
Oliver J. Pountney ◽  
Mike Wilson ◽  
...  
Keyword(s):  
Experimental Results ◽  
Radial Clearance ◽  
Rotating Fluid ◽  
Flow Rates ◽  
Hot Gas ◽  
Wide Range ◽  
The Common ◽  
Axial Clearance ◽  
Better Than ◽  
Good Agreement

Part 1 of this two-part paper presented experimental results for externally-induced (EI) ingress, where the ingestion of hot gas through the rim seal into the wheel-space of a gas turbine is controlled by the circumferential variation of pressure in the external annulus. In Part 2, experimental results are presented for rotationally-induced (RI) ingress, where the ingestion is controlled by the pressure generated by the rotating fluid in the wheel-space. Although EI ingress is the common form of ingestion through turbine rim seals, RI ingress or combined ingress (where EI and RI ingress are both significant) is particularly important for double seals, where the pressure asymmetries are attenuated in the annular space between the inner and outer seals. In this paper, the sealing effectiveness was determined from concentration measurements, and the variation of effectiveness with sealing flow rate was compared with theoretical curves for RI ingress obtained from an orifice model. Using a nondimensional sealing parameter, Φ0, the data could be collapsed onto a single curve, and the theoretical variation of effectiveness with Φ0 was in very good agreement with the data for a wide range of flow rates and rotational speeds. It was shown that the sealing flow required to prevent RI ingress was much less than that needed for EI ingress, and it was also shown that the effectiveness of a radial-clearance seal is significantly better than that for an axial-clearance seal for both EI and RI ingress.

Use of Pressure Measurements to Determine Effectiveness of Turbine Rim Seals

2014 ◽  
Author(s):  
J. Michael Owen ◽  
Kang Wu ◽  
James A. Scobie ◽  
Carl M. Sangan ◽  
GeonHwan Cho ◽  
...  
Keyword(s):  
Pressure Difference ◽  
Radial Clearance ◽  
Experimental Measurements ◽  
Pressure Measurements ◽  
Sweet Spot ◽  
Hot Gas ◽  
Mainstream Flow ◽  
Concentration Measurements ◽  
Arbitrary Location ◽  
Good Agreement

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 εc determined from concentration measurements in a rig could be used to determine εp 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 εp equals εc, 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 εp determined using the theoretical model and values of εc determined from concentration measurements. Supporting computations, using a 3D steady 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.

Numerical Characterization of Hot Gas Ingestion Through Turbine Rim Seals

2016 ◽  
Author(s):  
Riccardo Da Soghe ◽  
Cosimo Bianchini ◽  
Carl M. Sangan ◽  
James A. Scobie ◽  
Gary D. Lock
Keyword(s):  
Flow Rate ◽  
Numerical Study ◽  
Axial Flow ◽  
Radial Clearance ◽  
Buffering Effect ◽  
Hot Gas ◽  
Numerical Predictions ◽  
Wide Range ◽  
Thermal Buffering

This paper deals with a numerical study aimed at the characterization of hot gas ingestion through turbine rim seals. The numerical campaign focused on an experimental facility which models ingress through the rim seal into the upstream wheel-space of an axial-turbine stage. Single-clearance arrangements were considered in the form of axial- and radial-seal gap configurations. With the radial-seal clearance configuration, CFD steady-state solutions were able to predict the system sealing effectiveness over a wide range of coolant mass flow rates reasonably well. The greater insight of flow field provided by the computations illustrates the thermal buffering effect when ingress occurs: for a given sealing flow rate, the effectiveness on the rotor was significantly higher than that on the stator due to the axial flow of hot gases from stator to rotor caused by pumping effects. The predicted effectiveness on the rotor was compared with a theoretical model for the thermal buffering effect showing good agreement. When the axial-seal clearance arrangement is considered, the agreement between CFD and experiments worsens; the variation of sealing effectiveness with coolant flow rate calculated by means of the simulations display a distinct kink. It was found that the “kink phenomenon” can be ascribed to an over-estimation of the egress spoiling effects due to turbulence modelling limitations. Despite some weaknesses in the numerical predictions, the paper shows that CFD can be used to characterize the sealing performance of axial- and radial-clearance turbine rim seals.

Influence of Honeycomb Rubbing on the Labyrinth Seal Performance

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Daniel Frączek ◽  
Włodzimierz Wróblewski ◽  
Krzysztof Bochon
Keyword(s):  
Aircraft Engine ◽  
Labyrinth Seal ◽  
Turbine Rotor ◽  
Geometrical Model ◽  
Computational Effort ◽  
Radial Clearance ◽  
Leakage Flow ◽  
Leakage Flows ◽  
Full Structure ◽  
Sst Turbulence Model

The aircraft engine operates in various conditions. In consequence, the design of seals must take account of the seal clearance changes and the risk of rubbing. A small radial clearance of the rotor tip seal leads to the honeycomb rubbing in take-off conditions, and the leakage flow may increase in cruise conditions. The aim of this study is to compare two honeycomb seal configurations of the low-pressure gas turbine rotor. In the first configuration, the clearance is small and rubbing occurs. In the second,—the fins of the seal are shorter to eliminate rubbing. It is assumed that the real clearance in both configurations is the same. A study of the honeycomb geometrical model is performed to reduce the computational effort. The problem is investigated numerically using the RANS equations and the two-equation k–ω SST turbulence model. The honeycomb full structure is taken into consideration to show details of the fluid flow. Main parameters of the clearance and leakage flows are compared and discussed for the rotor different axial positions. An assessment of the leakage flow through the seal variants could support the design process.

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