Indirect Turbulence Measurement in Gas Turbine Stages Using Heat Flux Probe Free

An experimental study with the application of a custom designed heat flux probe and a modified Kiel probe to measure the turbulence intensity along the turbine gas path downstream of the combustor was performed in an industrial gas turbine engine. The probes were calibrated in a hot-cascade facility test rig which closely emulates engine operating conditions, particularly Re number and Mach number. Correlations based on the test results were compared with the data available in the literature. Indirect turbulence measurements performed in gas turbine engines show that the turbulence intensity at the combustor exit for different combustors can vary from 8% to 12% and the turbulence intensities (combined mainstream and wake generated turbulence) downstream from first and second stage blades can reach 12% to 18%. The results show that the unsteady wakes generated from upstream blade trailing edge play a major role in the turbulence augmentation on downstream nozzle heat transfer. A similar effect is expected in the turbine blade leading edge with a wake turbulence generated by the trailing edge of the upstream vane. An established correlation allows the prediction of a combined turbulence intensity along the gas path when initial combustor mainstream turbulence intensity and engine design parameters are defined (rotating speed, number of airfoils, trailing edge diameter, mainstream velocity, etc.).