TR-PIV measurements of secondary flow characteristics in a linear high pressure turbine cascade

The temporal and time-mean characteristics of the secondary flow in a linear turbine cascade are investigated using an in-house time-resolved particle image velocimetry (TR-PIV) system and the analysis technique of power spectrum distribution (PSD). The experiments are carried out in a low-speed water tunnel, which is made of scaled-up GE-E3 high pressure blades to form a linear turbine cascade. The typical characteristics of the growth and development of horseshoe vortex (HV) and passage vortex (PV) in the cascade are exhibited with a statistical analysis based on successive 4000 instantaneous measurements over 13 cross sections. The shedding of the coherent vortex structure near leading edge is revealed by the PSD analysis. With the help of the high temporal resolution of the TR-PIV system, the typical movement modes of the unsteady HV near the leading edge are captured. The experimental data indicate that the low-frequency oscillation of the HV is a quasi-periodic process on low Reynolds number condition.