US Patent 8057181 Multiple expansion film cooling hole for turbine airfoil

A film cooling hole for a turbine airfoil used in a gas turbine engine, where the film cooling hole is formed from a laser with smooth surfaces and without sharp corners, the film hole having a metering section of constant diameter, a first diffusion section having a conical shape, and a spreading section having a contoured clam shell cross sectional shape that opens onto the airfoil surface. The contoured clam shell shaped spreading section includes a raised middle portion with depressions on both sides, and slanted side walls that slant toward the hole opening. The laser cut film cooling hole can be formed after the TBC has been applied.