Session: 05-11 Turbine Facility Sensors & Diagnostics

Paper Number: 124106

124106 - Comprehensive Experimental Assessment of Unsteady Pressure and Heat Flux in a Small-Core Turbine Over-Tip Shroud 

Tip leakage significantly impacts turbomachinery efficiency, causing pressure loss and generating regions of high thermal load on the blade and the shroud. The periodic passage of the rotor blades results in highly transient flows near the shroud and their effects are dependent on the tip clearance size. Small blade-to-blade tip clearance variations become extremely relevant with novel turbine designs that target small cores operating at high speeds with clearances below 0.5 mm. Therefore, the assessment of the impact of these complex flows is paramount to designing the new generation of small-core turbines. The limitations of URANS simulations in resolving unsteady detached and secondary flows in very tight clearance configurations, and the need for computational tool validation, justifies the necessity of complementary experimental studies. This manuscript provides an extensive experimental analysis of the shroud’s unsteady heat flux and static pressure, aiming to characterize the effects of the unsteady phenomena that govern the squealer tip clearance region of small-core turbines. To that end, Atomic Layer Thermopile  sensors and  fast response pressure transducers are used to perform high-frequency acquisitions at 2MHz. The instrumentation is mounted onto the STARR testing rig, the small-core two-stage high-speed turbine test section in the Purdue Experimental Turbine Aerothermal Lab, and measurements are taken at engine-representative conditions at various pressure ratios and tip clearance sizes. The recorded data is phase-locked averaged over the revolution period to account for slight variations in the rotational speed of the turbine rig. Further synchronization of the various signals allows the individual blade identification and the retrieval of each magnitude’s row signature for every condition studied. The resulting unsteady pressure and heat flux values are first analyzed independently throughout the rotational phase to understand the flow field generated by the passing squealer blade tips. The experimental measurements are then imposed in CFD computations to identify the related transient 3D tip leakage flow mechanisms. Afterward, the effect of tip clearance and pressure ratio on the unsteady phenomena is studied. Finally, the row signatures are evaluated against each other to analyze dependencies and governing phenomena between them.

Presenting Author: Antonio Castillo Sauca Purdue University

Presenting Author Biography: Antonio Castillo received his M.S. in Aeronautics & Astronautics from Purdue University in 2021. He is currently a PhD candidate in the Purdue Experimental Turbine Aerothermal Laboratory, focusing his doctoral research in the assessment of of tip leakage flows for small core turbines.

Authors:

Antonio Castillo Sauca Purdue University
Lakshya Bhatnagar Purdue University
Lukas Benjamin Inhestern Purdue University
Guillermo Paniagua Purdue University