Amir Nejat - School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran
Ali Izadi - Senior researcher, Vehicle, Fuel and Environment Research Institute, University of Tehran, Iran
Vahid Esfahanian - School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran

Tip leakage loss introduces major part of losses of the rotor in axial gas turbines.Therefore, the rotor blade tip has a considerable effect on rotor efficiency. To understand the flow physics of the rotor tip leakage, we solve the flow field for different tip platforms (passive flow control) and by considering coolant tip injection (active flow control). Various blade tip configurations such as squealers and extensions on both pressure andsuction sides, partial PS-squealer and flat tip with various tip clearances are generated.The computational domains are generated using unstructured prism layers for boundarylayer resolution and unstructured, tetrahedral mesh for main flow. By using a finite volume CFD solver capable of solving RANS equations in an unstructured domain, the transonic compressible flow in the domain is solved. To capture the turbulent field inblade tip, shear stress transport (SST) k-ω model is employed. By using mixing plane approach, it is possible to couple outlet boundary of stator and inlet boundary of rotorand investigate the stator-rotor interaction in the rotor flow field and its consequence tip leakage flow. To investigate the combined effects of active and passive flow control measures in blade tip region, we simulate baseline geometry with and without tip coolant to show the effects of geometrical features of the rotor tip as well as the effect of tip coolant mass flow rate. Taking into account various rotor tip configurations and their tip leakage losses, it is possible to propose an optimum configuration

Active and Passive Flow Controls, CFD, Tip Leakage Flow