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research-article

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 United Kingdom
j.a.scobie@bath.ac.uk

Fabian P. Hualca

Department of Mechanical Engineering University of Bath Bath, BA2 7AY United Kingdom
f.hualca@bath.ac.uk

Marios Patinios

Department of Mechanical Engineering University of Bath Bath, BA2 7AY United Kingdom
m.patinios@bath.ac.uk

Carl M. Sangan

Department of Mechanical Engineering University of Bath Bath, BA2 7AY United Kingdom
c.m.sangan@bath.ac.uk

J Michael Owen

Department of Mechanical Engineering University of Bath Bath, BA2 7AY United Kingdom
j.m.owen@bath.ac.uk

Gary D. Lock

Department of Mechanical Engineering University of Bath Bath, BA2 7AY United Kingdom
g.d.lock@bath.ac.uk

1Corresponding author.

ASME doi:10.1115/1.4038361 History: Received July 10, 2017; Revised August 31, 2017

Abstract

In gas turbines, rim seals are fitted at the periphery of stator and rotor discs to minimise 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 disc. 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.

Copyright (c) 2017 by ASME
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