A Survey on the Geometry of Cylindrical Cooling Holes E.KIANPOUR 1a , NOR AZWADI CHE SIDIK 1b , Iman Golshokuh 2 1 Department of Thermo Fluid, Faculty of Mechanical Engineering University Technology of Malaysia 81310 Skudai, Johor MALAYSIA 2 Faculty of Mechanical Engineering Islamic Azad University of Izeh Branch Izeh, Khuzestan IRAN a ekianpour@gmail.com b azwadi@fkm.utm.my Abstract: - This study was done to extend database knowledge about the film cooling function at the end of combustor and inlet of turbine. The well-known Brayton cycle plays a key role to get higher engine efficiency in aero-engine turbine. But the high temperature of the combustor exit flow creates harsh environment. These conditions lead to a reduction in the life of critical parts. There are two separate ways for gas turbine cooling: internal cooling and external cooling. Film cooling is one of the most effective external cooling methods. In this system, a low temperature thin boundary layer which is formed by the cooling holes attached on the protected surface. Cooling holes are divided into several layouts. Cylindrical cooling holes are the most traditional and in this study, a literature survey was done on the limited researches that considered the effects of cylindrical cooling holes geometry variations on film cooling, particularly from the first of 21 th century. Key-Words: - Gas turbine- Film Cooling- Cylindrical cooling hole- Dilution jets- Slot- Row cooling holes 1 Introduction The famous Brayton cycle is a key to achieve higher turbine gas engine efficiency and power to weight ratio. To increase the efficiency, turbine industries try to increase the combustor outlet temperature [1]. However, this temperature is such above that all materials cannot resist against this value of temperature [2]. Also, turbine inlet temperature increase prepared harsh environment at the end of combustor and inlet of turbine. Such condition can destroy the critical components downstream the combustor. Therefore, a cooling technique must be applied to prevent the thermal degradation of turbine parts. Gas turbine cooling classified into two different schemes: internal cooling and external cooling. In the internal cooling method, coolant provided by the compressor, is forced into the cooling flow circuits inside turbine components. In the external way, the injected coolant is directly perfused from coolant manifold to save downstream components against hot gases. In the external cooling, coolant is used to quell the heat transfer from hot gas stream to a component. Film cooling is the most well-known method of external cooling preservation. In this system, a low temperature thin boundary layer such as buffer zone is formed by the cooling holes and attached on the protected surface. Cylindrical cooling hole is the simplest form of cooling holes. In this type of cooling holes, the coolant runs through the holes and spread into the main flow with no change. As shown in (Figure 1), the coolant was injected in the stream wise direction at an angle of α degree from the horizontal surface. Fig.1 A view of cylindrical cooling holes The change of geometry parameters of these holes is a topic which motivated researchers among years. Therefore, this investigation increases the basement knowledge about the film cooling and the effects of geometry characteristics variations on cooling performance. Computational Methods in Science and Engineering ISBN: 978-1-61804-174-6 157