Advancements in Wall Film Thickness Measurement Under High Pressure and High Temperature Conditions for Gas Turbine Applications

In pursuit of quantitative measurements of liquid wall film thickness under high-pressure and -temperature conditions, a novel image processing approach in combination with a standard laser-shadowgraphy setup was developed and demonstrated for the first time at the high-pressure combustion test rig (HBKS). The wall-film extraction technique was validated against a laser triangulation sensor under laboratory conditions for film thicknesses in the range of 100–800 μm. It was then applied to detailed shadow images of liquid fuels (kerosene and light heating oil) and water spray impingement onto a long metal plate in a jet-in-crossflow configuration at 10 bar. After reaching a maximum thickness of about 680 μm, the kerosene film diminished completely prior to reaching the end of the metal plate. In comparison, the water film exhibited a delayed onset on the metal plate but grew steadily and persisted at a thickness of above 600 μm. Injection of kerosene emulsified with water at a 1:1 mass ratio also resulted in a persisting liquid film until the end of the metal plate. In the latter two cases, substantial quantity of liquid exited the spray chamber in the form of film and spray particles.