High Intensity, Large Length-Scale Freestream Turbulence Generation in a Transonic Turbine Cascade

Heat transfer predictions in gas turbine engines have focused on cooling techniques and on the effects of various flow phenomena. The effects of wakes, passing shock waves and freestream turbulence have all been of primary interest to researchers. The focus of the work presented in this paper is to develop a turbulence grid capable of generating high intensity, large-scale turbulence for use in experimental heat transfer measurements in a transonic facility. The grid is desired to produce freestream turbulence characteristic of the flow exiting the combustor of advanced gas turbine engines. A number of techniques are discussed in this paper to generate high intensity, large length-scale turbulence for a transonic facility. Ultimately, the passive grid design chosen is capable of producing freestream turbulence with intensity of approximately 10–12% near the entrance of the cascade passages with an integral length-scale of 2 cm.