Aerodynamic aspects of the sealing of gas-turbine rotor-stator systems

Phadke, U. P.; Owen, J. Michael

doi:10.1016/0142-727x(88)90061-6

Cited by 70 publications

(11 citation statements)

References 2 publications

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“…In the open literature, Abe et al [8] were the first to recognise the relevance of the pressure asymmetries in the annulus gas path in driving hot gas ingestion. Further to this, Phadke and Owen [4] and [9] defined two regimes based on the dominating mechanism in hot gas ingestion: rotationally-induced ingestion would occur at low when the disc pumping effects prevail, whilst externally-induced ingestion would take place when the ratio is large and the external pressure asymmetries govern ingress. The latter scenario would imply predominance of and independence (or negligible effect) of , expected to be a few orders of magnitude lower.…”

Section: Literature Reviewmentioning

confidence: 99%

Performance of a Turbine Rim Seal Subject to Rotationally-Driven and Pressure-Driven Ingestion

Revert

Beard

Chew

et al. 2021

Journal of Engineering for Gas Turbines and Power

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This experimental study considered the performance of a chute rim seal downstream of turbine inlet guide vanes (but without rotor blades). The experimental set up reproduced rotationally-driven ingestion without vanes and conditions of pressure-driven ingestion with vanes. The maximum rotor speed was 9000 rpm corresponding to a rotational Reynolds number of 3.3x106 with a flow coefficient of 0.485. Measurements of mean pressures in the annulus and the disc rim cavity as well as values of sealing effectiveness deduced from gas concentration data are presented. At high values of flow coefficient (low rotational speeds), the circumferential pressure variation generated by the vanes drove relatively high levels of ingestion into the disc rim cavity. For a given purge flow rate, increasing the disc rotational speed led to a reduction in ingestion, shown by higher values of sealing effectiveness, despite the presence of upstream vanes. At U_ax/((Ob))="0.485" , the sealing effectiveness approached that associated with purely rotationally-driven ingestion. A map of sealing effectiveness against non-dimensional purge flow summarises the results and illustrates the combined rotational and pressure-driven effects on the ingestion mechanism. The results imply that flow coefficient is an important parameter in rim sealing and that rotational effects are important in many applications, especially turbines with low flow coefficient

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Section: Literature Reviewmentioning

confidence: 99%

Performance of a Turbine Rim Seal Subject to Rotationally-Driven and Pressure-Driven Ingestion

Revert

Beard

Chew

et al. 2021

Journal of Engineering for Gas Turbines and Power

View full text Add to dashboard Cite

show abstract

“…Ingestion has not only been shown to be affected by rotational effects but has also been shown to be affected by the main gas path flow, especially the vane exit pressure field. Phadke and Owen [5] performed experiments for several rim seal geometries at a variety of main gas path conditions. Although the study did not include airfoils, they showed that at low main gas path velocities (related to low airfoil Reynolds numbers), ingestion was driven by rotational effects, such as disk pumping, but at higher main gas path velocities (related to high airfoil Reynolds numbers) ingestion was driven by the nonaxisymmetric pressure difference in the main gas path.…”

Section: Introductionmentioning

confidence: 99%

Effects of Purge Flow Configuration on Sealing Effectiveness in a Rotor–Stator Cavity

Clark

Barringer

Johnson

et al. 2018

Journal of Engineering for Gas Turbines and Power

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Secondary air is bled from the compressor in a gas turbine engine to cool turbine components and seal the cavities between stages. Unsealed cavities can lead to hot gas ingestion, which can degrade critical components or, in extreme cases, can be catastrophic to engines. For this study, a 1.5 stage turbine with an engine-realistic rim seal was operated at an engine-relevant axial Reynolds number, rotational Reynolds number, and Mach number. Purge flow was introduced into the interstage cavity through distinct purge holes for two different configurations. This paper compares the two configurations over a range of purge flow rates. Sealing effectiveness measurements, deduced from the use of CO2 as a flow tracer, indicated that the sealing characteristics were improved by increasing the number of uniformly distributed purge holes and improved by increasing levels of purge flow. For the larger number of purge holes, a fully sealed cavity was possible, while for the smaller number of purge holes, a fully sealed cavity was not possible. For this representative cavity model, sealing effectiveness measurements were compared with a well-accepted orifice model derived from simplified cavity models. Sealing effectiveness levels at some locations within the cavity were well-predicted by the orifice model, but due to the complexity of the realistic rim seal and the purge flow delivery, the effectiveness levels at other locations were not well-predicted.

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“…This implied the stator wake to be more dominant than the blade bow wave when cavity ingestion is under investigation. The authors also reported the applicability of design correlations corresponding to the rotational induced versus mainstream pressure asymmetry ingestion mechanisms reported earlier by Phadke and Owen [9,10].…”

Section: Introductionmentioning

confidence: 86%

Unsteady 360 Computational Fluid Dynamics Validation of a Turbine Stage Mainstream/Disk Cavity Interaction

Mirzamoghadam

Kanjiyani

Riahi

et al. 2014

Journal of Turbomachinery

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The amount of cooling air assigned to seal high pressure turbine (HPT) rim cavities is critical for performance as well as component life. Insufficient air leads to excessive hot annulus gas ingestion and its penetration deep into the cavity compromising disk or cover plate life. Excessive purge air, on the other hand, adversely affects performance. Experiments on a rotating turbine stage rig which included a rotor-stator forward disk cavity were performed at Arizona State University (ASU). The turbine rig has 22 vanes and 28 blades, while the cavity is composed of a single-tooth lab seal and a rim platform overlap seal. Time-averaged static pressures were measured in the gas path and the cavity, while mainstream gas ingestion into the cavity was determined by measuring the concentration distribution of tracer gas (carbon dioxide) under a range of purge flows from 0.435% (C w ¼ 1540) to 1.74% (C w ¼ 6161). Additionally, particle image velocimetry (PIV) was used to measure fluid velocity inside the cavity between the lab seal and the rim seal. The data from the experiments were compared to time-dependent computational fluid dynamics (CFD) simulations using FLUENT CFD software. The CFD simulations brought to light the unsteadiness present in the flow during the experiment which the slower response data did not fully capture. An unsteady Reynolds averaged Navier-Stokes (RANS), 360-deg CFD model of the complete turbine stage was employed in order to increase the understanding of the swirl physics which dominate cavity flows and better predict rim seal ingestion. Although the rotor-stator cavity is geometrically axisymmetric, it was found that the interaction between swirling flows in the cavity and swirling flows in the gas path create nonperiodic/time-dependent unstable flow patterns which at the present are not accurately modeled by a 360 deg full stage unsteady analysis. At low purge flow conditions, the vortices that form inside the cavities are greatly influenced by mainstream ingestion. Conversely at high purge flow conditions the vortices are influenced by the purge flow, therefore ingestion is minimized. The paper also discusses details of meshing, convergence of time-dependent CFD simulations, and recommendations for future simulations in a rotor-stator disk cavity such as assessing the observed unsteadiness in the frequency domain in order to identify any critical frequencies driving the system.

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Aerodynamic aspects of the sealing of gas-turbine rotor-stator systems

Cited by 70 publications

References 2 publications

Performance of a Turbine Rim Seal Subject to Rotationally-Driven and Pressure-Driven Ingestion

Performance of a Turbine Rim Seal Subject to Rotationally-Driven and Pressure-Driven Ingestion

Effects of Purge Flow Configuration on Sealing Effectiveness in a Rotor–Stator Cavity

Unsteady 360 Computational Fluid Dynamics Validation of a Turbine Stage Mainstream/Disk Cavity Interaction

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