Influence of internal parallel and v-shaped ribs on the discharge coefficient of a cylindrical film cooling hole

Abstract

An experimental study has been conducted to investigate the discharge behaviour of cylindrical film cooling holes with the main focus on the effects of rib arrangement and crossflow velocity inside the internal cooling passage of a gas turbine blade. Two straight flow channels of rectangular cross-section simulate the crossflow situations present at the inlet and outlet of a film cooling hole. The two channels are connected by a single scaled-up film cooling hole with a diameter of 10 mm, an inclination angle of 30 , and a length-to-diameter ratio of 6. Measurements have been performed at various internal crossflow Mach numbers and rib geometries for both parallel and perpendicular orientations of internal and external crossflows. Parallel and v-shaped ribs with quadratic cross-section and four different angles with respect to the internal crossflow direction (45 , 60 , 75 , and 90 ) have been placed upstream and downstream of the entrance of the hole at one wall of the cooling passage. The rib height equals the hole diameter, the rib pitch to height ratio is 10. The internal crossflow Mach number has been varied between 0 and 0.37.The data show that placing ribs onto the wall of the coolant passage may result in reduced, unchanged, or even increased discharge coefficients. Internal crossflow Mach number and orientation of the coolant passage in respect to the hole axis have been identified as major influencing parameters.

Experimental Study on the Influence of the Streamwise Position of Film Hole Extraction in Internal Ribbed Cooling Channels of Turbine Blades

“…The relevance of these influences as well as favourable cooling hole positions in the rib segment are a matter of research interest. A detailed view on hole placement in relation to turbulators can be found in Bunker and Bailey (2001), Heneka et al (2011), Agata et al (2012) and Klavetter et al (2016) investigating the influence of the cooling hole position relative to the turbulator and the shape of the ribs on the discharge coefficient and film cooling effectiveness. Thurman and Poinsatte (2001) and Kunze and Vogeler (2013) investigated the internal heat transfer for 90°r ibs and revealed the position of cooling holes next to the upstream rib as superior to middle and downstream position.…”

Experimental Study on the Influence of the Streamwise Position of Film Hole Extraction in Internal Ribbed Cooling Channels of Turbine Blades

“…The relevance of these influences as well as favourable cooling hole positions in the rib segment are a matter of research interest. A detailed view on hole placement in relation to turbulators can be found in Bunker and Bailey (2001), Heneka et al (2011), Agata et al (2012) and Klavetter et al (2016) investigating the influence of the cooling hole position relative to the turbulator and the shape of the ribs on the discharge coefficient and film cooling effectiveness. Thurman and Poinsatte (2001) and Kunze and Vogeler (2013) investigated the internal heat transfer for 90° ribs and revealed the position of cooling holes next to the upstream rib as superior to middle and downstream position.…”