Experimental Investigation of Gas Turbine Aerodynamics using Planar Laser-Induced Fluorescence (PLIF).

An experimental PhD programme will be conducted with the aim of investigating the aerodynamics in a gas turbine, specifically the effect of purge flow on the mainstream flow aerodynamics. Due to the high temperatures found in turbines any hot air that flows into the disc cavity, the space between the stationary components and rotating components of the turbine, can cause serious damage to the turbine and also results in a loss of efficiency, this flow is called ingress. To counteract this cooling air/purge flow is introduced through the disc cavity to cool the ingress flow, this is called egress flow. Egress flow causes aerodynamic losses when introduced into the mainstream flow resulting in a reduced turbine efficiency. The design technique in modern gas turbines of end wall contouring (EWC) which alters the static pressure field between the stator vanes and rotor blades has been investigated by several researchers in recent years mainly by Dr Martin G Rose. EWC if done correctly could theoretically be used to reintroduce egress flow more efficiently by reducing the vortices and crossflow formed around the rotor blades. Also EWC could reduce the amount of egress flow by reducing the static pressure difference across the stator and rotor, resulting in a lower pressure of the purge flow and as a result a lower flowrate. This will be researched by using the newly constructed large annulus rig (LAR) at the University of Bath and using planar laser-induced fluorescence (PLIF) techniques to examine the flow trajectory. This will complement the PIV (three component Volumetric Velocimetry) measurements which examine the velocity field, to give a clear picture of the effect of the purge flow on the mainstream flow aerodynamics. The project will investigate different EWC profiles to determine their effectiveness at reducing egress flow, reducing the aerodynamic losses from the mixing of the purge flow with the mainstream flow and the secondary flow losses. The overall aim of the project is to improve the aerodynamic efficiency in a gas turbine by a combined design of rim seal exit geometry and EWC. The project is also in association with Siemens and will draw on their extensive experience.