Unsteady Computation of Ingress Through Turbine Rim Seals

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

In high-pressure turbines, cool air is purged through rim
seals at the periphery of wheel-spaces between the stator and rotor discs. The purge suppresses the ingress of hot gas from the annulus but superfluous use is inefficient. In this paper the interaction between the ingress, purge and mainstream flow is studied using unsteady numerical simulations based on the DLR TRACE solver. The computations are compared to experimental measurements from a one-and-a-half stage
axial-turbine rig operating with engine-representative blade and vane geometries, and overlapping rim seals. Radial traverses using a miniature CO2 concentration probe quantified the penetration of ingress into the rim seal and the outer portion of the wheel-space. Unsteady pressure measurements from circumferentially-positioned transducers on the stator disc identified distinct frequencies in the wheelspace,
and the computations reveal these are associated with
large-scale flow structures near the outer periphery rotating at just less than the disc speed. It is hypothesised that the physical origin of such phenomenon is driven by Kelvin-Helmholtz instabilities caused by the tangential shear between the annulus and egress flows, as also postulated by previous authors. The presence and intensity of these rotating structures are strongly dependent on the purge flow rate.
While there is general qualitative agreement between
experiment and computation, it is speculated that the underprediction by the computations of the measured levels of ingress is caused by deficiencies in the turbulence modelling.
LanguageEnglish
Title of host publicationProceedings of ASME Turbo Expo 2018: Turbine Technical Conference and Exposition
StatusPublished - 11 Jun 2018

Fingerprint

turbines
rims
stators
annuli
wheels
turbine wheels
egress
Kelvin-Helmholtz instability
vanes
high temperature gases
pressure measurement
blades
engines
transducers
penetration
flow velocity
turbulence
shear
probes
air

Cite this

Horwood, J., Hualca Tigsilema, F. P., Wilson, M., Scobie, J., Sangan, C., & Lock, G. (2018). Unsteady Computation of Ingress Through Turbine Rim Seals. In Proceedings of ASME Turbo Expo 2018: Turbine Technical Conference and Exposition [GT2018-75321]

Unsteady Computation of Ingress Through Turbine Rim Seals. / Horwood, Joshua; Hualca Tigsilema, Fabian Patricio; Wilson, Michael; Scobie, James; Sangan, Carl; Lock, Gary.

Proceedings of ASME Turbo Expo 2018: Turbine Technical Conference and Exposition. 2018. GT2018-75321.

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Horwood, J, Hualca Tigsilema, FP, Wilson, M, Scobie, J, Sangan, C & Lock, G 2018, Unsteady Computation of Ingress Through Turbine Rim Seals. in Proceedings of ASME Turbo Expo 2018: Turbine Technical Conference and Exposition., GT2018-75321.
Horwood J, Hualca Tigsilema FP, Wilson M, Scobie J, Sangan C, Lock G. Unsteady Computation of Ingress Through Turbine Rim Seals. In Proceedings of ASME Turbo Expo 2018: Turbine Technical Conference and Exposition. 2018. GT2018-75321
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abstract = "In high-pressure turbines, cool air is purged through rimseals at the periphery of wheel-spaces between the stator and rotor discs. The purge suppresses the ingress of hot gas from the annulus but superfluous use is inefficient. In this paper the interaction between the ingress, purge and mainstream flow is studied using unsteady numerical simulations based on the DLR TRACE solver. The computations are compared to experimental measurements from a one-and-a-half stageaxial-turbine rig operating with engine-representative blade and vane geometries, and overlapping rim seals. Radial traverses using a miniature CO2 concentration probe quantified the penetration of ingress into the rim seal and the outer portion of the wheel-space. Unsteady pressure measurements from circumferentially-positioned transducers on the stator disc identified distinct frequencies in the wheelspace,and the computations reveal these are associated withlarge-scale flow structures near the outer periphery rotating at just less than the disc speed. It is hypothesised that the physical origin of such phenomenon is driven by Kelvin-Helmholtz instabilities caused by the tangential shear between the annulus and egress flows, as also postulated by previous authors. The presence and intensity of these rotating structures are strongly dependent on the purge flow rate.While there is general qualitative agreement betweenexperiment and computation, it is speculated that the underprediction by the computations of the measured levels of ingress is caused by deficiencies in the turbulence modelling.",
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AU - Horwood, Joshua

AU - Hualca Tigsilema, Fabian Patricio

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AU - Sangan, Carl

AU - Lock, Gary

PY - 2018/6/11

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N2 - In high-pressure turbines, cool air is purged through rimseals at the periphery of wheel-spaces between the stator and rotor discs. The purge suppresses the ingress of hot gas from the annulus but superfluous use is inefficient. In this paper the interaction between the ingress, purge and mainstream flow is studied using unsteady numerical simulations based on the DLR TRACE solver. The computations are compared to experimental measurements from a one-and-a-half stageaxial-turbine rig operating with engine-representative blade and vane geometries, and overlapping rim seals. Radial traverses using a miniature CO2 concentration probe quantified the penetration of ingress into the rim seal and the outer portion of the wheel-space. Unsteady pressure measurements from circumferentially-positioned transducers on the stator disc identified distinct frequencies in the wheelspace,and the computations reveal these are associated withlarge-scale flow structures near the outer periphery rotating at just less than the disc speed. It is hypothesised that the physical origin of such phenomenon is driven by Kelvin-Helmholtz instabilities caused by the tangential shear between the annulus and egress flows, as also postulated by previous authors. The presence and intensity of these rotating structures are strongly dependent on the purge flow rate.While there is general qualitative agreement betweenexperiment and computation, it is speculated that the underprediction by the computations of the measured levels of ingress is caused by deficiencies in the turbulence modelling.

AB - In high-pressure turbines, cool air is purged through rimseals at the periphery of wheel-spaces between the stator and rotor discs. The purge suppresses the ingress of hot gas from the annulus but superfluous use is inefficient. In this paper the interaction between the ingress, purge and mainstream flow is studied using unsteady numerical simulations based on the DLR TRACE solver. The computations are compared to experimental measurements from a one-and-a-half stageaxial-turbine rig operating with engine-representative blade and vane geometries, and overlapping rim seals. Radial traverses using a miniature CO2 concentration probe quantified the penetration of ingress into the rim seal and the outer portion of the wheel-space. Unsteady pressure measurements from circumferentially-positioned transducers on the stator disc identified distinct frequencies in the wheelspace,and the computations reveal these are associated withlarge-scale flow structures near the outer periphery rotating at just less than the disc speed. It is hypothesised that the physical origin of such phenomenon is driven by Kelvin-Helmholtz instabilities caused by the tangential shear between the annulus and egress flows, as also postulated by previous authors. The presence and intensity of these rotating structures are strongly dependent on the purge flow rate.While there is general qualitative agreement betweenexperiment and computation, it is speculated that the underprediction by the computations of the measured levels of ingress is caused by deficiencies in the turbulence modelling.

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M3 - Conference contribution

BT - Proceedings of ASME Turbo Expo 2018: Turbine Technical Conference and Exposition

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