Turbine Nozzle Endwall Film Cooling Study Using Pressure-Sensitive Paint

Abstract

Endwall surface film cooling effectiveness was measured on a turbine vane endwall surface using the pressure-sensitive paint (PSP) technique. A double staggered row of holes and a single row of discrete slots were used to supply film cooling in front of the nozzle cascade leading edges. Nitrogen gas was used to simulate film cooling flow as well as a tracer gas to indicate oxygen concentration such that film effectiveness by the mass transfer analogy could be obtained. Cooling mass flow was controlled to be 0.5 to 3.0 percent of the mainstream mass flow. The free-stream Reynolds number was about 283,000 and Mach number was about 0.11. The free-stream turbulence intensity was kept at 6.0 percent for all the tests, measured by a thermal anemometer. The PSP was calibrated at various temperatures and pressures to obtain better accuracy before being applied to the endwall surface. Film effectiveness distributions were measured on a flat endwall surface for five different mass flow rates. The film effectiveness increased nonlinearly with mass flow rate, indicating a strong interference between the cooling jets and the endwall secondary flows. At lower mass flow ratios, the secondary flow dominated the near wall flow field, resulting in a low film effectiveness. At higher mass flow ratios, the cooling jet momentum dominated the near wall flow field, resulting in a higher film effectiveness. The comparison between hole injection and slot injection was also made.

Turbine Blade Film Cooling Using PSP Technique

“…A less cumbersome non-contact mass transfer analogy based on Pressure Sensitive Paint (PSP) has been proposed by Zhang and Fox (1999) and Zhang and Jaiswal (2001). This method has been used to arrive at detailed effectiveness contours at the Turbine Heat Transfer Lab in Texas A&M University.…”

“…The effectiveness corresponding to the film coolant discharged through the the rotor-stator gap has been studied by Burd et al (2000), Oke et al (2002) and Zhang and Jaiswal (2001). Difficult to cool areas such as the blade leading edge-end-wall junction can be cooled using this approach.…”

“…(e.g. Zhang and Jaiswal (2001), Mhetras et al (2007), Ahn et al (2006)). When a coolant with a different density is injected through the film cooling holes (to simulate realistic density ratios), the above equation needs to be modified.…”

Experimental investigations on complex vortex flows using advanced flow diagnostic techniques

“…Pressure sensitive paints (PSP) have recently been applied to film cooling applications [52][53][54][55]. PSP was first used in aerospace applications to obtain detailed surface pressure distributions [56].…”

An Experimental Investigation on the Trailing Edge Cooling of Turbine Blades by using PIV and PSP Techniques

“…Instead of conducting temperature measurements on the surface of interest, it becomes more and more popular to quantify the effectiveness of turbine blade cooling designs by conducting "cold" experiments with the Pressure Sensitive Painting (PSP) technique [15,16]. The PSP technique used for film cooling effectiveness measurements is based on mass transfer analogy, which is free from heat conduction related measurement errors frequently encountered in the temperature-based experiments.…”