Engine designers continually strive to increase the air turbine-entry temperate of their engines to benefit from improved specific fuel consumption. The outcome of this is that first-stage turbine blades are exposed to the highest working temperatures and stresses in the engine.

Film and internal cooling strategies used in the blades make sure that metal temperatures stay within acceptable limits. Bleed off of cooling air from the compressor stage reduces the engine's efficiency. Engine designers need reliable data and models to design effective and efficient cooling strategies.

State-of-the-art flow visualisation techniques

The film cooling rig is our Centre's new test bench for studying film cooling flows. It uses state-of-the-art flow visualisation techniques:

• Carbon dioxide planar laser-induced fluorescence (CO2-PLIF)
• Volumetric 3-component velocimetry (V3V)

PLIF is an optical technique that uses a camera to track light emissions from fluorescing carbon dioxide species within a laser light sheet. V3V is a 3D version of classical particle imaging velocimetry (PIV). It uses three cameras to track tracers introduced in a flow illuminated by a laser cone. Using PLIF, we can trace the trajectory of the carbon dioxide coolant flow out of the film cooling holes. V3V will deliver component plots of velocity in 3D space.

The rig’s modular design allows us to test different flow conditions and film cooling geometries. As well as the PLIF and V3V measurements, we will also measure:

• Pressure
• Temperature
• Turbulence
• Boundary layer profiling
• Mass flow and concentration

These measurements will allow a full characterisation of the film cooling geometries under test in the rig. This will provide essential information to engine designers.