Effect of Ingress on Turbine Discs

Cho, GeonHwan; Sangan, Carl M.; Owen, J. Michael; Lock, Gary

doi:10.1115/gt2015-42324

Cited by 8 publications

(9 citation statements)

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“…In contrast to the purge flow, the ingested flow mainly stayed on the stator side of the rim seal. This type of flow pattern is typical of a rim cavity with a rotor due to disk pumping and the thermal buffering effect [19,20], however, it is interesting to note a consistent trend in this static rim seal where rotational effects have been removed.…”

Section: Sealing Effectiveness With Purge Flowmentioning

confidence: 75%

Effects of Purge Jet Momentum on Sealing Effectiveness

Clark

Barringer

Thole

et al. 2016

Journal of Engineering for Gas Turbines and Power

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Driven by the need for higher cycle efficiencies, overall pressure ratios for gas turbine engines continue to be pushed higher thereby resulting in increasing gas temperatures. Secondary air, bled from the compressor, is used to cool turbine components and seal the cavities between stages from the hot main gas path. This paper compares a range of purge flows and two different purge hole configurations for introducing the purge flow into the rim cavities. In addition, the mate face gap leakage between vanes is investigated. For this particular study, stationary vanes at engine-relevant Mach and Reynolds numbers were used with a static rim seal and rim cavity to remove rotational effects and isolate gas path effects. Sealing effectiveness measurements, deduced from the use of CO2 as a flow tracer, indicate that the effectiveness levels on the stator and rotor side of the cavity depend on the mass and momentum flux ratios of the purge jets relative to the swirl velocity. For a given purge flow rate, fewer purge holes resulted in better sealing than the case with a larger number of holes.

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Section: Sealing Effectiveness With Purge Flowmentioning

confidence: 75%

Effects of Purge Jet Momentum on Sealing Effectiveness

Clark

Barringer

Thole

et al. 2016

Journal of Engineering for Gas Turbines and Power

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“…Cho et al [5], using the same rig as that of Pountney et al [4], measured the transient surface temperature of the rotor using infra-red sensors instead of TLC. The variation of surface temperature with time was then used as a boundary condition for the numerical solution of Fourier's equation, from which 𝑇 𝑟,𝑎𝑑 was calculated.…”

Section: Brief Review Of Relevant Researchmentioning

confidence: 99%

Model of Effect of Hot Gas Ingress on Temperatures of Turbine Disks

Owen

Tang

Lock

2018

Journal of Engineering for Gas Turbines and Power

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Ingress is the leakage of hot mainstream gas through the rim-seal clearance into the wheel-space between the rotating turbine disk (the rotor) and the adjacent stationary casing (the stator). The high-pressure rotor is purged by a radial outflow of air from the high-pressure compressor, and this cooling air is also used to reduce the ingress. The engine designer needs to predict the stator and rotor temperatures as a function of cooling-flow rate. The sealing effectiveness determines how much air is needed to reduce or prevent ingress; although there are numerous theoretical and experimental papers on the effectiveness of different seal geometries, there are few papers on the effect of ingress on the temperature of the rotating disk. This is an unsolved problem of great practical importance: under high stress, a small increase in metal temperature can significantly reduce operating life. In this paper, conservation equations and control volumes are used to develop theoretical equations for the exchange of mass, concentration and enthalpy in an adiabatic rotor–stator system when ingress occurs. It is assumed that there are boundary layers on the rotor and stator, separated by an inviscid rotating core, and the fluid entrained from the core into the boundary layer on the rotor is recirculated into that on the stator. The superposed cooling flow protects the rotor surface from the adverse effects of hot-gas ingress, which increases the temperature of the fluid entrained into the rotor boundary layer. A theoretical model has been developed to predict the relationship between the sealing effectiveness on the stator and the adiabatic effectiveness on the rotor, including the effects of both ingress and frictional heating. The model involves the use of a nondimensional buffer parameter, Ψ, which is related to the relative amount of fluid entrained into the rotor boundary layer. The analysis shows that the cooling flow acts as a buffer, which attenuates the effect of hot gas ingress on the rotor, but frictional heating reduces the buffer effect. The theoretical effectiveness curves are in good agreement with experimental data obtained from a rotor–stator heat-transfer rig, and the results confirm that the buffer effect increases as the sealing effectiveness of the rim seals decreases. The analysis quantifies the increase in the adiabatic rotor temperature due to direct frictional heating, which is separate from the increase due to the combined effects of the ingress and the indirect frictional heating of the entrained fluid. These combined effects are reduced as Ψ increases, and Ψ = 1 at a critical flow rate above which there is no entrained fluid and consequently no indirect heating of the rotor. The model also challenges the conventional physical interpretation of ingress as, in general, not all the hot gas that enters the rim-seal clearance can penetrate into the wheel-space. The ingress manifests itself through a mixing of enthalpy, which can be exchanged even if no ingested fluid enters the wheel-space.

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“…The rig has been used extensively for measurements of heat transfer and fluid dynamics, validating a series of theoretical models (e.g. [11][12][13][14]. Recently the turbine stage was redesigned and reconfigured specifically for the introduction of leakage flows.…”

Section: Experimental Facilitymentioning

confidence: 99%

Influence of Leakage Flows on Hot Gas Ingress

Patinios

Ong

Scobie

et al. 2018

Journal of Engineering for Gas Turbines and Power

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One of the most important problems facing gas turbine designers today is the ingestion of hot mainstream gases into the wheel-space between the turbine disk (rotor) and its adjacent casing (stator). A rim seal is fitted at the periphery and a superposed sealant flow—typically fed through the bore of the stator—is used to prevent ingress. The majority of research studies investigating ingress do so in the absence of any leakage paths that exist throughout the engine's architecture. These inevitable pathways are found between the mating interfaces of adjacent pieces of hardware. In an environment where the turbine is subjected to aggressive thermal and centrifugal loading, these interface gaps can be difficult to predict and the resulting leakage flows which pass through them even harder to account for. This paper describes experimental results from a research facility which experimentally models hot gas ingestion into the wheel-space of an axial turbine stage. The facility was specifically designed to incorporate leakage flows through the stator disk; leakage flows were introduced axially through the stator shroud or directly underneath the vane carrier ring. Measurements of CO2 gas concentration, static pressure, and total pressure were used to examine the wheel-space flow structure with and without ingress from the mainstream gas-path. Data are presented for a simple axial-clearance rim-seal. The results support two distinct flow-structures, which are shown to be dependent on the mass-flow ratio of bore and leakage flows. Once the leakage flow was increased above a certain threshold, the flow structure is shown to transition from a classical Batchelor-type rotor-stator system to a vortex-dominated structure. The existence of a toroidal vortex immediately inboard of the outer rim-seal is shown to encourage ingestion.

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Effect of Ingress on Turbine Discs

Cited by 8 publications

References 0 publications

Effects of Purge Jet Momentum on Sealing Effectiveness

Effects of Purge Jet Momentum on Sealing Effectiveness

Model of Effect of Hot Gas Ingress on Temperatures of Turbine Disks

Influence of Leakage Flows on Hot Gas Ingress

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