Turbulence Intensity Measurements in a High-Pressure Gas Turbine Stage

Abstract: This Thesis work focused on the acquisition and evaluation of data on mean velocity, turbulence intensity and length scales obtained via hot wire measurements in a high pressure single-stage land-based turbine available at the Department of Heat and Power Technology in KTH. Turbulence was generated by the use of grids and twoprobes, upstream and downstream of the turbine stage, were used. Different cases with different features were taken into consideration in this work: data were acquiredfor three different grids (I, II and III), two different blisks (5 and 6) and two operatingpoints. After post-processing all the information obtained from the anemometer, interesting comparisons between sub-cases could be made, and conclusions could bedrawn. In particular, it was found that Grid III generates a higher turbulence intensityupstream (around 13 %) with respect to Grid II (6 %) and I (3 %). Also, turbulenceintensity downstream did not seem to be affected by the conditions upstream butonly from the blisk type: turbulence levels were very similar when the same bliskwas mounted regardless of the type of grid upstream. Furthermore, the presence ofturbulence resulted in a slight decrease of the stage total-to-static efficiency ηT −S ofless than 0.5 % for Grid III while almost no change in efficiency was noticed when GridII or I were mounted. Furthermore, three different length scales were computed andanalyzed: Integral Length Scale, Taylor Microscale and Kolmogorov Microscale. Whilethe first two were found to be both in the order of 10−3 m, the last one -as expected- ismuch smaller, around 10−6 m.