

Title of Thesis
Effects Of Cooling Hole Shapes On Film Cooling Effectiveness 
Author(s)
Fayyaz Hussain Asghar 
Institute/University/Department
Details Department Of Nuclear Engineering / Pakistan
Institute Of Engineering And Applied Sciences, Islamabad 
Session 2010 
Subject Nuclear Engineering 
Number of Pages 240 
Keywords (Extracted from title, table of contents and
abstract of thesis) Compressor, Effectiveness, Hole,
Results, Cooling, Effects, Ratio, Rows, Requirement, Numerical,
Angles, Film, Shapes, Spatially, Performance 
Abstract The present study is related to the numerical investigation of different hole shapes for
film cooling performance, which is widely used for cooling of high temperature gas turbines.The adiabatic film cooling effectiveness values are determined computationally, downstream of
30o inclined cooling holes.Different hole shapes compared are circular holes, two types of
triangular holes, and two types of semicircular holes. Semicircular1 hole, which has straight
edge towards windward direction and curved edge towards leeward side, is found to produce best
effectiveness results.This type of hole shows much higher values of laterally averaged
effectiveness at blowing ratios of 0.67 and 1.0 as compared to a full circular hole.At blowing
ratios of 1.33 and 1.67, the effectiveness results from semicircular1 hole are found similar to the
results of full circular hole.The semicircular2 holes (straight edge towards leeward direction
and curved edge towards windward side) show almost similar effectiveness results as the results
of a full circular hole.Same effectiveness results from either type of semicircular hole as for a
full circular hole, is still highly advantageous because semicircular hole requires half mass flow
of coolant as compared to the requirement for a full circular hole, to produce the same blowing
ratio. Hence the loss of thermal efficiency, due to the extraction of coolant from the compressor,
can be reduced by using semicircular1 or semicircular2 hole. Semicircular2 holes are further
investigated by arranging them in two inlined/ staggered rows.Two rows of semicircular holes
are equivalent to a single row of full circular holes because in both cases coolant cost or
requirement is same.Hence the results of two rows of semicircular2 holes are compared with a
single row of full circular holes.Result of spatially averaged effectiveness from two staggered
rows of semicircular2 holes is 200% or higher than that from a single row of full circular holes
at all blowing ratios tested.The lowest coolant jet heights are found for two staggered rows of
semicircular holes, also the counter rotating vortex pair for that case is the weakest one. In the
study of compound angle orientations of a single row of circular holes, two staggered rows of
semicircular1 holes and two staggered rows of semicircular2 holes, it is seen that for simple
inclination angle (i.e., for β = 0o), the two staggered rows of semicircular1 holes for blowing
ratio of 0.67 show almost 400% higher values of spatially averaged effectiveness as compared to
a single row of full circular holes. When compound angles are used, it is seen that semicircular
holes (either semicircular1 or semicircular2) shows much higher values of spatially averaged
effectiveness than single row of circular holes, especially at low orientation angles. Among two
types of semicircular holes, the two staggered rows of semicircular1 holes show higher spatially
averaged effectiveness as compared to two staggered rows of semicircular2 holes but this
difference decreases with increasing orientation angle (β).Also, the two staggered rows of
semicircular1 holes without any compound angle show better spatially averaged effectiveness
than from the single row of circular holes or two staggered rows of semicircular2 holes at all
orientation angles.Hence using semicircular1 holes in staggered rows, the need of compound
angles may be avoided.Finally it is recommended to use the semicircular1 holes instead of full
circular holes for much better effectiveness or for reduced coolant requirement.

