Performance Analysis Of An Axial Exhaust
Diffuser Downstream Of An Un-shrouded Turbine
Author(s)
R. Blanco & S. Farokhi
Abstract
Performance of an axial exhaust diffuser downstream of an un-shrouded turbine
rotor is computationally analyzed. Three-dimensional analysis of two
turbine stage-exhaust diffuser configurations has been performed. In one case,
the turbine rotor is shrouded and in the second case, the rotor is un-shrouded.
The static pressure recovery coefficient in the exhaust diffuser is used as the
diffuser performance parameter. It has been found that the over the tip leakage
flow in the un-shrouded rotor emerges as a swirling wall jet at the upper wall of
the diffuser. The case of the shrouded rotor produced no wall jet at the entrance
to the diffuser and the turbine exit flow was \“quasi-uniform”. The presence of
the wall jet allowed the annular diffuser outer wall angle at stall point to increase
from 12° (in the shrouded rotor case) to 18° in the un-shrouded turbine. By
changing the angular speed of the rotor, the effect of the swirl in the turbine exit
plane on the performance of the diffuser was explored. In the shrouded rotor
case, the diffuser recovers higher static pressure when the inlet is swirl-free. In
this case, the performance of the diffuser is independent of whether the turbine
exit flow has co- or counter-swirl. However, in the presence of un-shrouded
rotors, higher static pressure recovery was achieved when the core flow
possessed slight counter-swirl. This observation was more pronounced when
larger diffuser upper wall angles were considered.
Keywords: Wall jet flow, over the tip leakage, residual swirl flow, exhaust
diffuser, turbine stage, static pressure recovery.
Keywords
Wall jet flow, over the tip leakage, residual swirl flow, exhaust
diffuser, turbine stage, static pressure recovery.
Related Book
Other papers in this volume
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