As part of the continuing technological advance towards the design of transonic steam turbine blades by analysis, rather than by experience based on time-consuming field testing, a series of experiments in a one-dimensional Laval nozzle was conducted to determine the nature of self-excited fluctuations due to shock wave/boundary layer interaction. Results in superheated steam flow showed peak-to-peak pressure fluctuations reaching 80 percent of the ideal across a normal shock wave, with a frequency spectrum having a fairly flat response to 150 Hz. Results in wet flow showed a distinctly different spectrum with decreased activity up to 200 Hz, but a shock wave interacting with incipient condensation near the nozzle throat produced additional broad spectral strength at 500 and 700 Hz. In addition, shock wave fluctuation in supercooled flow could trigger condensation in advance of the natural Wilson point.

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