Abstract
To study the influence of different hole length ratios on the flow structure and film cooling efficiency, a calculation model of fan-shaped hole was constructed and numerically studied. The effect of different hole length ratios on the cooling efficiency under different blowing ratios was compared and analyzed. The results showed that as the blowing ratio increases, the overall average efficiency of most of the hole length ratio cases first increases and then decreases. Only in the case with a cylindrical part length/total length ratio of 0.5 did the efficiency continue to increase. When the blowing ratio is small, the spanwise average efficiency of each hole length ratio case is closer, but the flow structure and efficiency distribution are quite different. For the medium blowing ratio, the overall average efficiency of the small hole length ratio case is higher, and the efficiency decreases as the hole length ratio increases. When the cylindrical part length/total length ratio is further increased to 1, the cooling efficiency region basically converges into a spanwise narrow region. For larger blowing ratio conditions, after 10D after the hole outlet, the case with a cylindrical part length/total length of 0.5 is more efficient.
Highlights
As the turbine inlet temperature increases, the thermal load of the turbine blades increases and higher requirements are put forward for the cooling of the turbine
1) As the blowing ratio increased from small to medium, the overall average efficiency of most cylindrical part length/total length ratio cases increased; only in the case with a cylindrical part length/total length ratio of 1 did the overall average efficiency first increase and decrease
When the blowing ratio was further increased to a larger condition, the overall average efficiency continued to increase in only the case with a cylindrical part length/total length ratio of 0.5
Summary
As the turbine inlet temperature increases, the thermal load of the turbine blades increases and higher requirements are put forward for the cooling of the turbine. Wright et al, 2011 used pressure-sensitive paint technology to conduct experimental research on the film cooling efficiency of cylindrical holes, fanshaped holes, and laidback fan-shaped holes and found that in all hole-type cases, as the freestream turbulence intensity increases, the film effectiveness decreases. Saumweber and Schulz, 2012 conducted an experimental study on the film cooling efficiency of two fan-shaped holes with L/D 6 and 10 and found that under the small blowing ratio condition, the cooling efficiency of the long hole length case was slightly higher. Under the condition of ensuring that the inlet and outlet of the film cooling hole remain unchanged, the ratio of the hole length of the film cooling hole is controlled by adjusting the position of the interface (b–b plane in the figure) between the cylindrical part and the fan-shaped part. The distribution of the spanwise average cooling efficiency in different grid numbers along the flow direction is
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