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Film Cooling Holes

This is a question about the film cooling holes used in turbomachinery. I would like to understand quantitatively the effect of errors in the positioning of the holes. Presumably, an error in the position of a row of holes causes higher surface temperatures which would lead to increased creep and oxidation of the material of the vane or blade, leading to reduced component lifetime and hence increased maintenance cost. Ideally, I would like to be able to judge if investment in reducing position errors in the cooling holes is worthwhile in terms of its impact on the component lifetime and hence cost.

Reply to
Stephen Blake
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The relative position of the holes is usually not highly critical from a cooling standpoint. The major concerns in positioning the holes are generally mechanical: ensuring the holes intersect the proper internal cavity, do not "backstrike" adjacent walls, and do not intersect with any adjancent holes. For small aero-engine blades these issues can be difficult to overcome, and improvements in hole position can be beneficial, but it would be difficult to quantify the benefit.

However, improving hole size tolerance generally has a much greater benefit. By reducing the flow variation, the average cooling flow can be reduced which benefits engine efficiency/output. It is fairly straight forward to calculate the benfit of reducing cooling air on engine performance.

D Parker

Reply to
Dave Parker

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