Research Abstract
This paper presents experimental investigations of the Heat Transfer Coefficient (HTC) performance of a
Micro-Tangential-Jet (MTJ) Film cooling scheme on a gas turbine vane using transient Thermochromic
Liquid Crystal (TLC) technique. The MTJ scheme is a micro-shaped scheme designed so that the secondary
jet is supplied parallel to the vane surface. In order to supply the jet in a direction parallel to the vane
surface, extra material was added on both pressure and suction sides. The film cooling performance of
one row of holes on both pressure and suction sides were investigated at a blowing ratio ranging from
0.5 to 1.5 on the pressure side and 0.25 to 0.625 on the suction side, calculated based on the MTJ scheme
exit area. The average density ratio during the investigations was 0.93, and the Reynolds number was
1.4E+5, based on the free stream velocity and the main duct hydraulic diameter. The pitch to diameter
ratio of the cooling holes is 5 on the pressure side and 6.5 on the suction side. The turbulence intensity
during all investigations was 8.5% and was measure two chords upstream the vane leading edge using the
PIV technique. The investigations showed that the increase in the HTC ratio due to the presence of the
MTJ scheme is very close to that resulting from the presence of normal traditional shaped schemes on
the pressure side. Meanwhile, a reduction in the HTC ratio is recorded on the suction side. Such performance
is attributed to the small overall height of the scheme which helped keep the resulting turbulence
to a minimum. Moreover, the HTC distribution downstream the MTJ scheme is uniform in the lateral
directions which helps minimize the thermal stresses. The Net Heat Flux Reduction (NHFR) parameter
is used to judge the overall performance of the MTJ scheme. The NHFR represents a combination of
the effects of both the cooling effectiveness and the HTC. Great enhancement in the NHFR performance
of the MTJ was observed compared to traditional shaped schemes. With the current MTJ scheme design
and dimensions and under the previously mentioned Reynolds number and turbulence intensity it was
observed that a blowing ratio close to unity, calculated based on the scheme exit area, provides an optimal
film cooling performance on both pressure and suction sides.
Research Journal
Int. J. of Heat and Mass Transfer
Research Pages
401-417
Research Rank
1
Research Vol
64
Research Year
2013