Of steam turbine wheel, batch and blade vibrations¹

Article type: Research Article

Authors: Kantorowicz, O.P.T.

Note: [1] Paper read before the North-East Coast Institution of Engineers snd Shipbuilders, Newcastle upon Tyne, on 23nd November 1963.

Abstract: The central concept in considering steam-excited wheel vibrations is the wave-speed curve which relates the circumferential propagation velocity of waves in turbine wheels to vibration frequency. Properties and diagnostic use of these curves are discussed, in particular their dependence on coupled systems (other stages, blading) and the consequent “anomalies”. The incidence of failures is discussed and it is shown that fortunately only a fraction of turbine stages in the design of which a risk was incurred – usually inadvertently – do in fact give trouble within the span of the economic life of the turbine. Failure thus appears to be the outcome of a chain of circumstances of which design decisions and inadequate workmanship are but links. Reported in detail are wave-speed curves for reaction blading with different arrangements of two binding wires. It is shown that little can be done about the general shape and position of the curve but that if the binding wire sectors are staggered breaks in the curve appear, related to the number of sectors, and at these breaks violent batch vibrations occur which are believed to be the immediate cause of some recent failures. Experiments on isolated batches show that a circumferential propagation velocity of waves in batches can be conceived and that sustained excitation of these vibrations is possible only when these velocities coincide with turbine running speed. From this follow some simple design rules. Observations on the uniformity of blades are reported and on the influence of the manner of blade fixation on vibration properties (frequency and damping) and on the variance of vibration parameters derived from field observations. It has also been possible in a simple case to explain the direction and frequency of vibration in a batch of blades from the corresponding vibration properties of individual blades.

DOI: 10.3233/ISP-1963-1010503

Journal: International Shipbuilding Progress, vol. 10, no. 105, pp. 170-192, 1963