Effect of Rotor Tip Casing Treatment on the Performance and Stability of a Transonic Axial Compressor Stage&nbsp;Subbaramu S., and Mahesh K. VarpeDepartment of Aerospace Engineering&nbsp;Ramaiah University of Applied Sciences, Bangalore 560058*Corresponding author (&nbsp;&nbsp; e-mail:&nbsp; ssubbaramu.aae.et@msruas.ac.in/ ssubbaramu@gmail.comMobile #: 08197302795)&nbsp;Abstract:In aero gas turbine engines major problems associated with highly efficient transonic axial compressor are stall and surge, flow losses, pressure and efficiency loss. &nbsp;Tip leakage flow and secondary flows are known to have considerable influence on the performance of axial compressors. The inception of stall, flow blockage and total pressure loss are influenced by tip leakage and secondary flows interaction. Both tip clearance losses and secondary flow losses are influenced by the aerodynamic and geometric parameters of the blade rows, like flow coefficient, rotor blade tip gap, blade aspect ratio, blade solidity and blade stagger angle.&nbsp;&nbsp;&nbsp;&nbsp; From the literature review, it is revealed that active and passive stall control techniques are used in transonic compressor to control rotor tip leakage flow interaction with end wall boundary layer and blade passage shock wave. Rotor casing treatment is one such passive stall control technique. Rotor casing treatments consists of slots, grooves or cavities on rotor casing, and recirculation type slots also. From experimental and numerical investigation, it is found that certain configuration of rotor casing treatment improves stall margin and efficiency&nbsp;&nbsp;&nbsp; The main objective of the present research is to understand effect of rotor casing treatment geometry on rotor passage tip leakage flow and associated losses. In the current work, a baseline NASA37 transonic axial compressor stage is modelled using CATIA 3D software and computational grid is generated using ANSYS-ICEMCFD software. Flow simulation of the baseline compressor stage is carried out at 100% design speed using ANSYS-CFX software, with k-ω SST turbulence model. Numerically predicted performance results are validated against available / published experimental and numerical data. Structured grid with hexahedral cells is created for both stator and rotor domain with wall y+ value less than 10. From grid independence study, an optimum grid size of 1.2 million cells is selected for further investigation.&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Further numerical investigation of NASA 37 compressor stage was carried out with casing treatment slot along rotor tip mean camber line. Intention of casing treatment is to mitigate tip leakage flow interaction with the endwall boundary layer, passage shock and secondary flows. Few parametric studies were performed by changing the number of casing treatment slots. Emphasis will be laid to understand the flow physics through the blade passages and quantifying the stall margin and percentage of loss in compressor without and with rotor tip casing treatment. From CFD post processing results of NASA 37 compressor stage without and with rotor casing treatment, it was evident that particular configuration of rotor tip casing treatment was able to improve compressor operating range by 35%. Stall mass flow rate was improved by 3% against baseline NASA37 stage. &nbsp;In stage with rotor tip casing treatment adiabatic efficiency is decreased by 0.9%. Further parametric studies will be performed to arrive at optimum configuration of rotor tip casing treatment, which improves NASA37 compressor stage performance and stability margin.

Effect of Rotor Tip Casing Treatment on the Performance and Stability of a Transonic Axial Compressor

Paper Proceedings: https://asmedigitalcollection.asme.org/GTINDIA/GTINDIA2021/volume/85536

ASME 2021 Gas Turbine India Conference (GTINDIA2021)

Supporting the need among researchers worldwide for additional online and multimedia content, ASME now offers the ASME Conference Video Collection. This platform will collect and provide long-term access to conference presentation videos, encompassing all technology areas within ASME's technical conference and events program. About 30,000-40,000 engineers across all mechanical engineering and related disciplines participate in ASME conferences each year. This includes authors of approximately 6,000 to 8,000 technical papers published by ASME, the majority of whom also submit video presentations for our virtual conferences. The video collection will be available as an add-on to existing product packages or as a separate subscription.