Numéro |
J. Phys. III France
Volume 2, Numéro 4, April 1992
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Page(s) | 575 - 594 | |
DOI | https://doi.org/10.1051/jp3:1992148 |
J. Phys. III France 2 (1992) 575-594
Analysis of experimental time-dependent blade surface pressures from an oscillating turbine cascade using the influence-coefficient technique
T. H. FranssonSwiss Federal Institute of Technology, Lausanne, Switzerland
(Received 15 February 1991, revised 9 September 1991, accepted 27 September 1991)
Abstract
A two-dimensional section of the last stage of a steam turbine blade has been investigated
experimentally in an annular non-rotating cascade facility as regards to its steady-state and
time-dependent aerodynamic characteristics at design and off-design conditions. The unsteady
experimental data obtained with the blades vibrating in the "travelling wave" mode indicate that
one of the main reasons for the flutter susceptibility of the cascade lies in the high expansion
and following shock wave close to the blade suction surface leading edge and the corresponding high
unsteady loading. The decomposition of the experimental data into unsteady aerodynamic influence
coefficients validates this conclusion and also shows that another reason for the flutter
susceptibility can be found in the fact that the cascades is overlapped for a part of the blade
surface where the local flow velocities are close to sonic. The unsteady aerodynamic influence
coefficients show that the instability arises because of the time dependent aerodynamic coupling
effects between, essentially, the reference blade and its immediate suction surface and, to a
lesser extent, pressure surface neighbors.
© Les Editions de Physique 1992