Which cooling method is described as coolant permeating through the blade from inside to provide internal cooling?

Which cooling method is described as coolant permeating through the blade from inside to provide internal cooling?

• A. Transpiration cooling
• B. Film cooling
• C. External air cooling only
• D. Liquid nitrogen immersion

Answer: (A)

Transpiration cooling works by forcing coolant through the blade’s porous walls or internal passages so it seeps out through the surface. This provides cooling from the inside as the coolant exits the pores, helping to remove heat directly from the blade material. It’s different from film cooling, where coolant is injected through holes to form a protective external film on the surface without permeating the wall. External air cooling only cools from the outside surface, not through the blade material, and liquid nitrogen immersion isn’t a practical turbine blade cooling method.

Transpiration cooling works by forcing coolant through the blade’s porous walls or internal passages so it seeps out through the surface. This provides cooling from the inside as the coolant exits the pores, helping to remove heat directly from the blade material. It’s different from film cooling, where coolant is injected through holes to form a protective external film on the surface without permeating the wall. External air cooling only cools from the outside surface, not through the blade material, and liquid nitrogen immersion isn’t a practical turbine blade cooling method.