In this paper, conjugate heat transfer (CHT) simulation is performed
for a low-pressure stage of MGT-70, a heavy-duty gas
turbine (GT) manufactured by MAPNA Group. Although the vane
and the blade are uncooled, CHT analysis is performed to assess the
validity of using the fluid temperature of an adiabatic simulation as
the uncooled vanes or blades temperature, and also to model the
heat transfer between root or shroud and vane or blade profile. To
compare the resultant temperatures of CHT and adiabatic flow
analysis both simulations are done, using the same boundary conditions.
The vane shroud extends over the blade tip, which is of
free-standing type, and there is not a shroud segment. In fact, the
vane and blade share the shroud. In order to predict the shroud
temperature more accurately, the vane and the blade are simulated
simultaneously as a stage using appropriate interfaces. A single
vane CHT simulation is also performed to evaluate the effect of
blade tip flow on the shroud temperature. Furthermore, the cavity
above the shroud, containing the cooling and sealing flow, is also
included in the model to better prediction of the shroud temperature.
In addition, the rim cavity and the labyrinth seal under the
vane platform are included in the model to better predict the vane
platform temperature and to capture the effect of purge flows on
vane and blade temperature.
Simulation results show that, although, the average bulk temperature
of the profile in both CHT and adiabatic simulations are
close to each other, there are great differences in temperature distribution
over the suction side and pressure side. These differences
are because of heat flux through the profile in CHT simulation,
which results in a more realistic metal temperature distribution.
Comparing the results of the single vane simulation and stage
simulation no remarkable difference is observed in the temperature
distribution, except for the shroud region above blade tip. This
reveals that, although, the tip leakage flow is better captured in the
stage simulation, it is only useful when the shroud temperature is of
interest and it does not affect the vane profile temperature distribution.
Finally, the inclusion rim cavity and labyrinth seal in the
simulation helps to predict the mass flow distribution of purge
flows and the effect of these flows on platform temperature distribution
in vane and blade.