Design of Combustor Cooling Slots for High Film Effectiveness: Part II—Film Initial Region

A heuristically based geometric grouping has been used to relate the geometry of practical film cooling slots of gas turbine engine combustors to the circumferential uniformity of axial velocity in the film and the average film effectiveness. To be satisfactory, the cooling performance of a slot has been shown to require a low value of this group. A study of film development has been extended to the initial region of the film where cooling performance is at its maximum. It is demonstrated that such a region exists for both practical slots and idealized two-dimensional slots, but that the character of the initial region flow is completely different for practical slots and cannot be described by the same methods as can be used for two-dimensional slots.