Journal of the Faculty of Engineering and Architecture of Gazi University 38:1 (2023) 357-369 Numerical analysis of secondary flow loss reduction in axial turbine blades using a combined endwall fence and casing groove method Emre Yıldırım* , Levent A. Kavurmacıoğlu Department of Mechanical Engineering, Faculty of Mechanical Engineering, İstanbul Technical University, 34437, Gümüşsuyu-Beyoğlu, Highlights: Graphical/Tabular Abstract  Analysing of secondary flows  Assessment of secondary flow losses  Secondary flow loss reducing In this study, five different fence geometries which are 2, 3, 5, 7 and 10 x 1.7 mm (height x width) are applied to blades region, respectively. After that, 3.0x1.7 mm (depth x width, narrow) and 1.5 x 5.2 mm (depth x width, wide) sized groove geometries are added to the solution domain together with each fences. It is shown in Figure A. on the upper line the coefficients obtained for rotor (no fence and no groove) and for rotor with each fence, on the middle line the coefficients obtained for rotor with each fence and the narrow groove together and on the bottom line the coefficients obtained for rotor with each fence and the wide groove together. As indicated in literature total pressure loss is decreased both by each fence alone and fences with grooves [8-15]. Figure A. Variation of total pressure loss coefficient Purpose: Three-dimensional and complex flow structure in axial turbines leads to aerodynamic losses and exergy destruction increase [1, 2]. The study is aimed to specify whether or not to be able to reduce secondary flow related aerodynamic losses in a gas turbine blade channel by using two different passive loss reduction methods. These methods are endwall fencing used mostly in axial turbine and casing groove mostly applied to tip region of compressor blades. Theory and Methods: In a process without heat transfer, entropy generation can be evaluated by total pressure loss point of view [22]. The total pressure losses are specified by calculating mass averaged total pressure loss coefficient at the blades outlet crosssections. Flow between blades is solved by incompressible N-S equations. Different fence and casing groove geometries are implemented to the blades passage to determine loss reduction levels. Results: The least coefficient is achieved by use 2.0x1.7 mm fence with 5.2x1.7 mm wide groove together. It is obtained 3 % reduction in total pressure loss coefficient compared to rotor case. This means lower total pressure losses and entropy generation level in blades with fences and grooves compared to rotor. Conclusion: It should also be considered compressibility and temperature effects. Furthermore, it should be performed an optimization process between fence and groove geometries to be able to decrease losses more. Keywords:  Secondary flow  Axial flow turbine  Secondary flow loss  Fence  Groove Article Info: Research Article Received: 07.02.2020 Accepted: 11.02.2022 DOI: 10.17341/gazimmfd.686234 Correspondence: Author: Emre Yıldırım e-mail: yildirimemre@itu.edu.tr phone: +90 212 293 1300