Background: Over all efficiency of a turbofan engine can be improved by increasing turbine
inlet temperature. To withstand the high turbine inlet temperatures advanced cooling techniques and
robust materials are required. Air supplied from compressor can be used to purge turbine components
and disk cavities from the incoming hot gas.
Objective: In the present study, an attempt is made to understand the aerodynamic and thermal effects
caused by the purge flow in the presence of stationary upstream wakes.
Methods: Reynolds Averaged Navier Stokes Equation coupled with SST turbulence model is used for
computational study. Base case experimental data conducted on a 5 blade linear cascade is used for
numerical validation. The coolant to mainstream blowing ratio is varied from 0.2 to 1.2 with a step size
Results: It is observed that with an increase in the blowing ratio, the mass averaged total pressure losses
also increase. Purge flow shifts the passage vortex away from the endwall and causes significant overturning
up to a span of 30-40mm, before they exhibit underturning up to midspan. In an effort to reduce
the losses, purge ejection angle is reduced to 45° from 90°. Significant loss reduction and improved
endwall protection are observed at 45° ejection angle. This ejection angle provides enough acceleration
and momentum to the fluid inside the endwall boundary layer. But the upstream secondary wakes and
secondary flows enhanced the mixing losses within the blade passage.
Conclusion: The turbulent mixing generated by upstream wakes reduced the film cooling effectiveness
over the endwall. The numerical results show that film cooling effectiveness can be improved by reducing
the purge ejection angle. Various patents have been discussed in this article.