Unsteady Endwall/Tip-Clearance Flows and Losses due to Turbine Rotor-Stator Interaction

Abstract

Unsteady static pressure on the tip endwall of a 1.5-stage lowspeed axial-flow turbine was measured in detail using a micro high-response pressure transducer to investigate effects of rotorstator interaction on the endwall and tip-clearance flows which play important roles in turbine loss generation process. In the present paper, distributions of the time-averaged and the timedependent pressures over the rust-stage rotor and the secondstage stator are presented. Also time-averaged and timedependent random fluctuations of the pressure were analyzed to understand unsteady behaviors of the flows and the associated losses over the endwall as well as inside the blade tip clearance. These unsteady characteristics were described for three rotor speeds with different incidences or loadings. Significantly large random fluctuations occur around the blade surfaces, particularly at the inlet and the outlet of the tip gap of the leakage flows, and in a flow separated region from the blade leading edge in a large negative incidence case A strong relation was found between the random fluctuation of the endwall static pressure and the total pressure loss inside the rotor, where large random fluctuation is attributed to high loss and vice versa. It can be seen clearly that the loss generation process is fairly unsteady due to the rotor-stator interaction.

Experimental Investigation of Blade-To-Blade Pressure Distribution in Contra-Rotating Axial Flow Pump

“…By means of the frequency spectrum analyses on the pressure data measured at the casing wall, Kameier et al investigated the tip clearance noises and related rotating instabilities for the axial turbomachines [10]. And Yamamoto et al researched the tip leakage flow and the rotor-stator interactions inside an axial flow turbine by measuring the casing wall pressure distribution using high response pressure transducers [11]. As our major experimental approach in the present researches, the static pressure on casing wall was measured from upstream to downstream of the both rotors to investigate the blade-to-bladepressure distribution under different rotational speed combinations.…”

Unsteady Numerical Investigation of Blade Tip Leakage, Part 1: Time-Averaged Results

“…Likewise, obtaining experimental measurements for heat transfer on the turbine shroud is extremely costly and difficult due to the high-temperature gradients as well as the size of the gap, as mentioned before. In the open literature, blade tip leakage flow has been studied over rotating blades [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. In addition, tip leakage flow has been investigated over stationary airfoils [16][17][18][19][20][21][22][23][24].…”

Tip Leakage Flow and Heat Transfer on Turbine Stage Tip and Casing: Effect of Unsteady Stator–rotor Interactions

“…Yamamoto et al (1994) studied the unsteadiness of the flows and associated losses in the blade tip clearance region.…”