A computational study of the multirow interaction mechanisms has been carried out for a one-and-a-half stage (NGV-rotor-stator) transonic turbine. In addition to measurable subharmonic unsteadiness on the rotor blades induced by two fundamental stator passing frequencies, a significant aperiodic (“mistuned”) circumferential variation of unsteady forcing magnitude by about three times has been observed in the downstream stator blades. Further parametric studies with various stator blade counts illustrate that the circumferential variation pattern of the unsteady forcing is dictated by the NGV-stator blade count difference, while the local stator forcing magnitude is affected by its circumferential clocking position relative to the upstream NGV blades. The present work suggests that the circumferential clocking together with the choice of blade count should be considered as an aeromechanical design parameter. For cases with stator-stator (or rotor-rotor) blade counts resulting in a tuned (or nearly tuned) unsteady forcing pattern, the clocking position should be chosen to minimize the unsteady forcing. On the other hand, if the choice of blade counts leads to a significant aerodynamic aperiodicity (mistuning), the clocking-forcing analysis can be used to identify the most vulnerable blade that is subject to the maximum forcing.
Blade Count and Clocking Effects on Three-Bladerow Interaction in a Transonic Turbine
Contributed by the International Gas Turbine Institute (IGTI) of THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS for publication in the ASME JOURNAL OF TURBOMACHINERY. Paper presented at the International Gas Turbine and Aeroengine Congress and Exhibition, Amsterdam, The Netherlands, June 3–6, 2002; Paper No. 2002-GT-30310. Manuscript received by IGTI, December 2001, final revision, March 2002. Associate Editor: E. Benvenuti.
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Li, H. D., and He, L. (December 1, 2003). "Blade Count and Clocking Effects on Three-Bladerow Interaction in a Transonic Turbine ." ASME. J. Turbomach. October 2003; 125(4): 632–640. https://doi.org/10.1115/1.1622711
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