Investigation of efficient film cooling configurations in realistically turbulent main flow

• Applicant: Professor Dr. Michael Pfitzner
• Subject Area: Fluid Mechanics
• Term: from 2017 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 324866747

The development of future, low emission gas turbine combustors requires efficient cooling concepts, which allow a wide range of options to control the combustion process due to a minimum consumption of cooling air. Applying new cooling configurations like the trench cooling, where the cooling air from the effusion jet is distributed laterally, the resulting film cooling efficiency can be considerably improved by up to one order of magnitude compared to simple effusion cooling. Up to now measurements were conducted at a main flow turbulence intensity of Tu = 1%. When exposing the trench geometry to the higher turbulence level of a real combustion chamber, the cooling efficiency might be reduced due to increased liftoff of the cooling air from the surface and premature mixing with the main flow.The main goal of the proposed research project is to achieve a deeper physical understanding of the detailed flow and heat transfer phenomena that occur in effusion cooling as compared to trench film cooling configurations through experimental and numerical investigations. The focus is on study of cooling films in a main flow of high turbulence characteristic for flows in real gas turbine combustion chambers. The effect of this increased main flow turbulence on the complex unsteady flow, mixing and heat transfer processes, as well as the resulting heat transfer coefficients and film cooling effectiveness will be studied experimentally and numerically.The experimental studies will use optical non-intrusive measurement technology. Besides standard techniques such as LDA and high speed PIV, novel measurement techniques will be optimized and applied. Using a combination of infrared and phosphorescence measurement techniques for measuring temperature boundary conditions, the distribution of the local heat transfer coefficient can be determined. Applying thermographic high speed PIV to the film cooling setup, time resolved simultaneous temperature and velocity distributions in the flow field can be measured. This allows the detailed examination of the complex unsteady flow structures and of the turbulent fluxes. The CFD simulations accompanying the experiment are performed using the commercial CFD code ANSYS Fluent with realizable k-epsilon model. For the detailed numerical studies of the effect of large eddies on the film structure and on the turbulent mixing, large eddy simulations will be performed using the open source CFD code OpenFOAM.

• DFG Programme: Research Grants