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Research Papers: Gas Turbines: Structures and Dynamics

Re-Ingestion of Upstream Egress in a 1.5-Stage Gas Turbine Rig

[+] Author and Article Information
James A. Scobie

Department of Mechanical Engineering,
University of Bath,
Bath BA2 7AY, UK
e-mail: j.a.scobie@bath.ac.uk

Fabian P. Hualca

Department of Mechanical Engineering,
University of Bath,
Bath BA2 7AY, UK
e-mail: f.hualca@bath.ac.uk

Marios Patinios

Department of Mechanical Engineering,
University of Bath,
Bath BA2 7AY, UK
e-mail: m.patinios@bath.ac.uk

Carl M. Sangan

Department of Mechanical Engineering,
University of Bath,
Bath BA2 7AY, UK
e-mail: c.m.sangan@bath.ac.uk

J. Michael Owen

Department of Mechanical Engineering,
University of Bath,
Bath BA2 7AY, UK
e-mail: j.m.owen@bath.ac.uk

Gary D. Lock

Department of Mechanical Engineering,
University of Bath,
Bath BA2 7AY, UK
e-mail: g.d.lock@bath.ac.uk

Contributed by the Structures and Dynamics Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received July 10, 2017; final manuscript received August 31, 2017; published online April 16, 2018. Editor: David Wisler.

J. Eng. Gas Turbines Power 140(7), 072507 (Apr 16, 2018) (10 pages) Paper No: GTP-17-1331; doi: 10.1115/1.4038361 History: Received July 10, 2017; Revised August 31, 2017

In gas turbines, rim seals are fitted at the periphery of stator and rotor discs to minimize the purge flow required to seal the wheel-space between the discs. Ingestion (or ingress) of hot mainstream gases through rim seals is a threat to the operating life and integrity of highly stressed components, particularly in the first-stage turbine. Egress of sealing flow from the first-stage can be re-ingested in downstream stages. This paper presents experimental results using a 1.5-stage test facility designed to investigate ingress into the wheel-spaces upstream and downstream of a rotor disk. Re-ingestion was quantified using measurements of CO2 concentration, with seeding injected into the upstream and downstream sealing flows. Here, a theoretical mixing model has been developed from first principles and validated by the experimental measurements. For the first time, a method to quantify the mass fraction of the fluid carried over from upstream egress into downstream ingress has been presented and measured; it was shown that this fraction increased as the downstream sealing flow rate increased. The upstream purge was shown to not significantly disturb the fluid dynamics but only partially mixes with the annulus flow near the downstream seal, with the ingested fluid emanating from the boundary layer on the blade platform. From the analogy between heat and mass transfer, the measured mass-concentration flux is equivalent to an enthalpy flux, and this re-ingestion could significantly reduce the adverse effect of ingress in the downstream wheel-space. Radial traverses using a concentration probe in and around the rim seal clearances provide insight into the complex interaction between the egress, ingress and mainstream flows.

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References

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Figures

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Fig. 1

Typical rim seal in a high-pressure turbine

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Fig. 2

Flow structure demonstrating re-ingestion

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Fig. 3

Simplified representation of mass flow rates and concentrations

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Fig. 4

Representation of CV

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Fig. 5

Test section and instrumentation

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Fig. 6

Radial-clearance seal configuration in the upstream and downstream wheel-spaces

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Fig. 7

Distributions of concentration effectiveness, ingress and egress flow ratios with nondimensional sealing flow rate in the upstream wheel-space (symbols denote data; lines are theoretical orifice-model fits)

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Fig. 8

Measurements of upstream concentration effectiveness in the annulus either side of the rotor blades (Φ0,u = Φmin,u)

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Fig. 9

Effect of downstream sealing flow rate on radial distribution of re-ingestion in the downstream annulus and wheel-space for Φ0,u = Φmin,u (squares: stator-wall; diamonds: rotating-core; circles: probe measurements)

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Fig. 10

Effect of upstream sealing flow rate on radial distribution of re-ingestion in the downstream annulus and rim seal region for Φ0,d = 0

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Fig. 11

Distributions of downstream concentration effectiveness, ingress and egress flow ratios for the datum case without upstream sealing flow (symbols denote data; lines are theoretical orifice-model fits)

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Fig. 12

Downstream measurements of concentration effectiveness with sealing flow rate for four values of unseeded upstream sealing flow (symbols denote data; line is theoretical orifice-model fit)

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Fig. 13

Downstream measurements of concentration effectiveness with sealing flow rate for four values of seeded upstream sealing flow (symbols denote data; line is theoretical orifice model fit)

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Fig. 14

Measured variation of χ with downstream sealing flow rate for three values of seeded upstream sealing flow rate

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Fig. 15

Measured variation of χ with nondimensional downstream concentration effectiveness for three values of upstream sealing flow rate

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