Method for preventing one-cell stall in bladed discs (5832606)
Inventors: Francis Kushner. Issued September 16, 1997 in United States
A method for preventing one-cell rotating stall initiated by a bladed disc having a plurality of blades including the steps of identifying a one-cell stall condition and modifying one or more blades to force the bladed disc into at least a two-cell stall pattern. This can be accomplished by modifying the spacing between the blades to force the bladed disc into at least a two-cell stall pattern. Alternatively, at least one of the blades can be geometrically modified so as to force the bladed disc into at least a two-cell stall pattern.
Turbomachinery stationary vane arrangement for disk and blade excitation reduction and phase cancellation (9,581,034)
Inventors: Francis Kushner, Brian Pettinato. Issued March 14, 2013 in United States
A turbomachine includes a plurality of rotating blades adjacent to a plurality of stationary vanes attached to a stationary casing. Stationary vanes are spaced apart circumferentially with equal spacing around an inner perimeter of the casing. Optionally, stationary vanes are offset radially and/or circumferentially. Stationary vanes may alternate with leading and/or trailing edges at different distances from the rotating blades. In one embodiment, stationary vanes have tapered leading and/or trailing edge angles to homogenize flow and reduce stator wake excitation, flow excitation, and acoustic excitation due to interaction with spinning modes of acoustic pressure pulsations at rotating blade passing frequency. Tapered trailing edges are arranged such that they are inclined at mutually opposing angles to reduce rotor blade and/or disk excitation by: a) homogenizing the successive wakes within the flow stream, and b) reducing the effect of vortices shed-off the stationary vanes on acoustic modes of the gas within the casing.
Disc Vibration – Rotating Blade and Stationary Vane Interaction
Published by (ASME Journal of Mechanical Design)
Authors: Frank Kushner. Published July 01, 1980
Describes 1976 discovery of Interaction Resonance for Bladed Disks
(Includes equations later termed by others as “Safe Diagrams” and also “Interference Diagrams”)
Rotating Component Modal Analysis And Resonance Avoidance Recommendations – An Update
Published by (Texas A&M University; Proceedings of the 42nd Turbomachinery Symposium, Turbomachinery Laboratory)
Authors: Kushner, F., Shurina, J., Strickland, R. A. Published October 01, 2013
Rotating disk and blade fatigue failures are usually a low percentage of failures i n most machinery types, but other than coupling / shaft end failures remain some of the most problematic for extensive repairs. High -cycle fatigue failures of rotating disks and blades are not common in most machinery types, but when they occur, they requi re extensive repairs and resolution can be problematic. This paper is an update of the tutorial given at the 2004 Turbomachinery Symposium focusing on high -cycle fatigue failures in steam turbines, centrifugal and axial gas compressors in refineries and pr ocess plants. The failure theories and many of the descriptions for cases given in 2004 have been updated to include blade resonance concerns for potential flow as well as vane and blade wake effects. Disk vibratory modes can be of concern in many machines , but of little concern in others as will be explained. In addition, vibratory modes are included where blades are coupled via communication with the main disk. Over the past decade, fluid -structure -interaction computational methods and modal testing have improved and have been applied to failure theories and problem resolution in the given cases. There is also added information on the effects of mistuning blades and disks, some beneficial and some with serious concerns for increased resonant amplification. Finally, knowledge about acoustic pressure pulsation excitation, particularly for centrifugal impellers at rotating blade passing frequency, has been greatly expanded. A review of acoustics calculations for failure prevention, mainly for high -pressure app lications is covered here.
| Noise Control & Acoustics
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