Effects of Incidence Angle on the Performance of Lightly Loaded Turbine Guide Vanes

Aero-performance and heat transfer measurements have been acquired in a lightly loaded vane cascade to investigate the influence of incidence angle on vane performance. Measurements were conducted at a nominal exit Mach number of 0.7 and an exit chord Reynolds number of 1,200,000. Inlet conditions included 4.5% to 5.5% grid generated turbulence levels and incidence angles ranging from -10° degrees to +10° in 5° increments. Losses have been estimated based on full and half span exit surveys across two passages with a 15° 5-hole cone probe. The measurements were acquired in a warm compressible flow rig designed and built for the present tests to be used in an existing flow facility. The flow rig included an inlet heat exchanger to reduce the effect of humidity, a flow control device to allow variation of Reynolds number, and a slanted square-mesh grid to produce a turbulence level of 4.5% to 5.5%. The measurements were taken across two passages downstream from a 6-vane, 5passage linear cascade using a 5-hole cone probe. The measurements provide a picture of the influence of inlet angle on cascade losses, turning angle and flow rate. Vane midspan pressure and heat transfer distributions were also acquired to provide an indication of loading and the state of the boundary layers.