Session: 12-10: Film Cooling Computational Studies (III)

Paper Number: 154073

The Effect of Crossflow Velocity on the Film Cooling Effectiveness of Fan Shaped Holes 

Film cooling is an effective cooling method found in modern gas turbine engines, which has a critical role to keep turbine metal temperatures under the respective material service limits while satisfying life requirements. The coolant flow blown from a set of holes onto vane/blade surfaces, interacts with the main stream flow, creating complex flow structures that impact both the airfoil's wall temperatures, hence cooling effectiveness and aerodynamic performance. A typical film-cooling hole is a cylindrical drilled hole with nearly sharp edges both at the inside and outside of the metal, subjected to manufacturing constraints. The exit surface of these holes are generally aligned to match main-stream flow direction. Albeit its simplicity, one major drawback of the cylindrical holes is that with high flow rates, cooling performance is significantly de-graded due to the formation of high-momentum jet around hole exit. Fan shaped film holes on the other hand, offer a worthy alternative to standard cylindrical holes and are frequently used for contemporary cooling configurations subjected to elevated turbine inlet gas temperatures. In this configuration, the coolant flow is diffused near the discharge plane. This lower momentum flow adheres better to the airfoil surface, thereby improving cooling performance

Current article aims at fundamental investigation of a fan shaped hole, which has 7 degrees of lateral and laidback angles. Firstly, numerical method is validated against test data from the selected literature by Thole et al. in terms of laterally averaged film effectiveness for a generic 7-7-7 fan shaped hole configuration. Then, the effects of secondary flows on film cooling effectiveness of cylindrical and fan shaped holes are examined. Afterwards, specific models are generated to study the impact of coolant crossflow velocity (Mach numbers of 0 - 0.25) and pressure ratio (1.05, 1.1) across cooling hole for a generic configuration. Lateral & local film cooling effectiveness distributions and discharge coefficient values are compared. Results prove that controlled separation in the diffuser section of fan shaped hole is a desirable feature to acquire higher lateral spreading and film effectiveness. Also, it is found that fan shaped hole has the higher discharge coefficient than cylindrical hole because of diffusion effect on throat static pressure for same environment conditions. Fan shaped hole can adjust itself with lower static pressure at throat section, matching same exit mainstream condition. In this way, it utilizes higher dynamic pressure gain, which causes the greater amount of coolant flow until static pressure of inlet and throat equals to each other. Beyond this specific condition, inlet static pressure drops below the throat static pressure and blowing ratio decreases.

Presenting Author: Erinc Erdem TUSAS ENGINE INDUSTRIES

Presenting Author Biography: After graduating from aerospace engineering in Middle East Technical University (METU) in 2002, Dr. Erdem started working for Roketsan Missile Industries, Inc. as a propulsion engineer, focusing on internal aerodynamics of solid rocket motors. In 2005, Dr. Erdem obtained his research M.Sc. from von Karman Institute for Fluid Dynamics (VKI) on numerical and experimental investigation of internal flows inside a simplified Ariane 5 rocket motor geometry with slag accumulation. In 2006, he obtained his M.Sc. from mechanical engineering in METU on a subject called numerical investigation of secondary gas injection systems for thrust vectoring. In 2011, he obtained a Ph.D. from the University of Manchester on active flow control studies at Mach 5 involving detailed wind tunnel measurements with various measurement techniques and complementary computational effort. Afterwards he carried on pursuing active research as a postdoctoral associate in the same university on low speed flow control using different actuation mechanisms. During his Ph.D. and postdoc studies, several projects on high/low speed wind tunnel testing were completed involving partners such as ESA, DSTL and EU FR7. Upon finishing the studies, Dr. Erdem started working for GE Aviation in Turkey in 2013 as thermal systems design lead engineer specializing on engine bay cooling and rotor-stator cooling in gas turbine engines. As of 2015, he is working for TUSAS Engine Industries (TEI) Inc., responsible for mainly thermal systems design comprised of secondary air systems, thermal analysis and component cooling. In addition, he works on radial compressor aerodynamics and rig testing. Dr. Erdem’s role in Chief Engineers Office involves overseeing/reviewing technical activities for the indigenous Turboshaft Engine Development program related to his expertise.

Authors:

Semih Avcun TUSAS ENGINE INDUSTRIES (TEI)
Erinc Erdem TUSAS ENGINE INDUSTRIES (TEI)
Sinan Sal TUSAS ENGINE INDUSTRIES (TEI)
Tolga Yasa Whittle Laboratory