An investigation into the heat transfer aspects of transpiration cooling
Date
2015-08-06
Authors
Hobson, G. V
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Abstract
Although transpiration cooling has been demonstrated to keep the
metal surface temperatures, in a gar turbine, below that at which
oxidation occurs even though the hot gas temperatures are in
excess of the metals melting temperature, few experimental studies
have been conducted on the heat transfer aspects of transpiration
cooling. Especially the effect blowing has on a turbulent
boundary layer that has developed over a porous surface that is
heated by the mainstream. Many studies have involved the blowing
or suction oi the boundary layer through heated porous plates.
Trans. an cooling was exper cntally investigated by making
use of an existing wind tunnel which was modified so as to simulate
the heat transfer phenomenon resulting from blowing coolant through
a porous wall into a heated mainstream. The existing wind tunnel
was designed and commissioned by Krieg (13) who considered the
momentum transfer aspects of transpiration cooling. The solution
of the momentum equation by Krieg forms the basis from which this
investigation was developed, the original solution procedure being
put forward by Cebeci and Smith (7). Krieg developed a generalised
two-dimensional finite-differunce compute* program to solve the
incompressible momentum equations describing a blown boundary layer.
This program was further developed as part of this effort to solve
the compressible momentum and neigy equations so as to account
for the heat transfer in the blown boundary layer. The program is
used to predict the experimental results obtained from the literature
as well is those ottained during the nine experimental runs on the
wind tunnel.
Freestream flow velocities varied from 4,^5 m/s to 14,95 m/s with
correspoi ;.ng temperatures of 44,95°C and 33,00eC respectively.
The blowing fr tion F, was varied from 0,0059 to a maximum of
,
temperature of 40°C.
The numerically calculated profiles and tho: » obi lined expurim ntally,
as well as one set presented by another researcher, compared well.
Finally, recommendations for future studies have been suggested.
Description
A dissertation presented in fulfilment of the requirements for
the Degree of Master of Science in Engineering
DECEMBER 1982