A statistical method for draft tube pressure pulsation analysis

Draft tube pressure pulsation (DTPP) in Francis turbines is composed of various components originating from different physical phenomena. These components may be separated because they differ by their spatial relationships and by their propagation mechanism. The first step for such an analysis was to distinguish between so-called synchronous and asynchronous pulsations; only approximately periodic phenomena could be described in this manner. However, less regular pulsations are always present, and these become important when turbines have to operate in the far off-design range, in particular at very low load. The statistical method described here permits to separate the stochastic (random) component from the two traditional ‘regular’ components. It works in connection with the standard technique of model testing with several pressure signals measured in draft tube cone. The difference between the individual signals and the averaged pressure signal, together with the coherence between the individual pressure signals is used for analysis. An example reveals that a generalized, non-periodic version of the asynchronous pulsation is important at low load.


Published in:
Proceedings of the 26th Symposium on Hydraulic Machinery and Systems, 1, 1-8
Presented at:
26th Symposium on Hydraulic Machinery and Systems, Beijing, China, August 19–23, 2012
Year:
2012
Publisher:
International Association For Hydraulic Research
Laboratories:




 Record created 2018-05-21, last modified 2019-08-12

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