Investigation Of The Effects Of Incidence Angle And Film Hole Shape On Gas Turbine Vane Leading Edge Film Cooling

The leading edge of gas turbine blade is a crucial heat transfer area, film cooling is usually applied to protect this area in industry. Leading edge film cooling can lower high temperature oxidation, creep, corrosion, thermal fatigue, thus increase component's life span.Experiments and numerical simulation are conducted on a turbine vane leading edge model with three staggered cylindrical film holes. The experiment is carried out in a low speed wind tunnel at environmental temperature, we use the infrared camera to get the temperature of the test model's surface, apply the transient measurement technique to know the film cooling effectiveness and convective heat transfer coefficient; use the commercial CFD software FLUENT to analyze the film cooling effectiveness and flow field. The effect of shape of hole, incidence angle (0°/5°/10°)at different averaged blow ratio(0.5-2) on leading edge flow field and adiabatic film cooling effectiveness is investigated.Results show that shape of hole and incidence angle can greatly affect the leading edge flow field and cooling effectiveness:The shaped hole has better cooling effectiveness over cylindrical hole at high blowing ratio, at medium blowing ratio the two have the same performance, at low blowing ratio the latter is even better. The shaped hole weakens the vortices at the exit of film cooling hole.The variation of incidence angle has a great influence on the streamlines at the exit of film holes; can strongly affect the thermal protection while the averaged blowing ratio is 1 or less, but becomes less dominant at higher blowing ratio. The region between the central film holes and left and right film holes is very susceptive to incidence angle variation. Both shaped hole and cylindrical hole film cooling have similar performance with respect to this factor. The film cooling effectiveness of the region between the central and left holes is lowest at 5°incidence angle. With the increase of incidence, the effectiveness of the left side downstream decreases and the right side increases. When the averaged blowing ratio is 1, there's no monotonous relationship between the incidence angle and effectiveness.When the averaged blowing ratio is 1, the adiabatic effectiveness of cylindrical hole is highest, but no the case when the incidence angle changes, the shaped hole has the highest effectiveness at highest blowing ratio, the same case as the incidence angle changes. With the decrease of blowing ratio, the vortices at the exit of film holes become smaller and finally disappear.