Experimental and Numerical Investigation of the Influence of Rotor Blades on Hot Gas Ingestion Into the Upstream Cavity of an Axial Turbine Stage

Bohn, Dieter; Rudzinski, Bernd; Sürken, Norbert; Gärtner, Wolfgang

doi:10.1115/2000-gt-0284

Cited by 52 publications

(27 citation statements)

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“…Chew et al reported both experimental and 3D computational fluid dynamics (CFD) results and concluded that inertial effects associated with the swirl component of velocity had an important influence on the flow. The combined influence of pressure asymmetries due to stationary vanes and rotating blades was noted by Green and Turner [8] and Bohn et al [9] who measured ingestion with both vanes and blades present. Bohn et al also presented unsteady CFD solutions showing some qualitative agreement with their data.…”

Section: Introductionmentioning

confidence: 81%

Measurement and Analysis of Ingestion Through a Turbine Rim Seal

Gentilhomme

Hills

Turner

et al. 2003

Journal of Turbomachinery

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Experimental measurements from a new single stage turbine are presented. The turbine has 26 vanes and 59 rotating blades with a design point stage expansion ratio of 2.5 and vane exit Mach number of 0.96. A variable sealing flow is supplied to the disc cavity upstream of the rotor and then enters the annulus through a simple axial clearance seal situated on the hub between the stator and rotor. Measurements at the annulus hub wall just downstream of the vanes show the degree of circumferential pressure variation. Further pressure measurements in the disc cavity indicate the strength of the swirling flow in the cavity, and show the effects of mainstream gas ingestion at low sealing flows. Ingestion is further quantified through seeding of the sealing air with nitrous oxide or carbon dioxide and measurement of gas concentrations in the cavity. Interpretation of the measurements is aided by steady and unsteady computational fluid dynamics solutions, and comparison with an elementary model of ingestion.

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Section: Introductionmentioning

confidence: 81%

Measurement and Analysis of Ingestion Through a Turbine Rim Seal

Gentilhomme

Hills

Turner

et al. 2003

Journal of Turbomachinery

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“…At engine conditions density differences are likely to be significant, so momentum or mass flux ratios may eventually prove more useful in correlating results. Some experiments including both rotor and stator blade rows have been reported by Green and Turner (1992) and Bohn et al (2000). Both sets of workers found evidence that the presence of rotor blades could improve sealing effectiveness, but Bohn et al found the opposite trend for a different seal design, and their blades had a surprisingly large effect on the pressure asymmetry due to the vanes.…”

Section: Introductionmentioning

confidence: 99%

“…Roy et al (2000) have also shown some agreement between steady CFD solutions and measurement from pressure tappings for a rim sealing rig including vanes and rotating blades. In another very recent paper Bohn et al (2000) included 3D, unsteady CFD calculations including both vanes and blades. They showed some differences in the calculated and measured levels of ingestion but obtained some qualitative agreement.…”

Section: Introductionmentioning

confidence: 99%

Computational and Mathematical Modeling of Turbine Rim Seal Ingestion

Hills

Chew

Turner

2002

Journal of Turbomachinery

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Understanding and modelling of main annulus gas ingestion through turbine rim seals is considered and advanced in this paper. Unsteady 3-dimensional computational fluid dynamics (CFD) calculations and results from a more elementary model are presented and compared with experimental data previously published by Hills et al (1997). The most complete CFD model presented includes both stator and rotor in the main annulus and the inter-disc cavity. The k-ε model of turbulence with standard wall function approximations is assumed in the model which was constructed in a commercial CFD code employing a pressure correction solution algorithm. It is shown that considerable care is needed to ensure convergence of the CFD model to a periodic solution. Compared to previous models, results from the CFD model show encouraging agreement with pressure and gas concentration measurements. The annulus gas ingestion is shown to result from a combination of the stationary and rotating circumferential pressure asymmetries in the annulus. Inertial effects associated with the circumferential velocity component of the flow have an important effect on the degree of ingestion.The elementary model used is an extension of earlier models based on orifice theory applied locally around the rim seal circumference. The new model includes a term accounting for inertial effects. Some good qualitative and fair quantitative agreement with data is shown.

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“…Green et al 17 showed the blades to have a positive effect in reducing ingestion. By contrast, Bohn et al 18 found the opposite effect, which was attributed to the increase of average static pressure asymmetry in the annulus due to the presence of the blades. The latter is more consistent with the findings of the present work.…”

Section: Introductionmentioning

confidence: 91%

Computation of ingestion through gas turbine rim seals

Zhou

Wilson

Owen

et al. 2012

Proceedings of the Institution of Mechanical Engineers, Part G:

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Three-dimensional unsteady computational fluid dynamics is applied to the ingestion of fluid from a non-uniform mainstream annulus flow via a rim-seal into a rotor-stator wheel-space. The results provide understanding of the complex flow and information for the development of more efficient computational models and analytical 'orifice models'. The commercial computational fluid dynamics code CFX has been used to carry out unsteady Reynolds-averaged Navier-Stokes computations with an shear stress transport turbulence model. A scalar equation is employed to represent the seeded tracer gas that can be used in experiments to determine sealing effectiveness, and the variation of effectiveness with sealing flow rate is determined for a simple axial clearance seal and one combination of axial and rotational Reynolds numbers. The computational domain comprises one pitch in a row of stator vanes and rotor blades. The rotating blade is accounted for by a sliding interface between the stationary and rotating sections of the model, located downstream of the seal clearance. The unsteady computations confirm that the magnitude of the peak-to-trough pressure difference in the annulus is the principal driving mechanism for ingestion (or ingress) into the wheel-space. This pressure difference is used in orifice models to predict sealing effectiveness; its magnitude however depends on the locations in the annulus and the wheel-space that are chosen for its evaluation as well as the sealing flow rate. The computational fluid dynamics is used to investigate the appropriateness of the locations that are often used to determine the pressure difference. It is shown that maximum ingestion occurs when the static pressure peak produced by the vane combines with that produced by the blade, and that highly swirled ingested flow could contact both the stator and rotor disk when little sealing flow is provided. The relationships between the unsteady simulations and simplified, more computationally efficient steady computations are also investigated. For the system considered here, ingress is found to be dictated principally by the pressure distribution caused by the vane. The effect of the rotating blade on the pressure distribution in the annulus is investigated by comparing the unsteady results with those for steady models that do not involve a blade. It is found that the presence of the blade increases the pressure asymmetry in the annulus. Although the pressure asymmetry predicted by unsteady and steady models have a similar magnitude, the sealing effectiveness is over-predicted considerably for the corresponding steady model. If a 'thin seal' geometric approximation is used in the steady model, however, similar effectiveness results compared with the unsteady model may be obtained much more economically.

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Experimental and Numerical Investigation of the Influence of Rotor Blades on Hot Gas Ingestion Into the Upstream Cavity of an Axial Turbine Stage

Cited by 52 publications

References 0 publications

Measurement and Analysis of Ingestion Through a Turbine Rim Seal

Measurement and Analysis of Ingestion Through a Turbine Rim Seal

Computational and Mathematical Modeling of Turbine Rim Seal Ingestion

Computation of ingestion through gas turbine rim seals

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