Forced Response in Axial Turbines Under the Influence of Partial Admission
2013 (English)In: Journal of turbomachinery, ISSN 0889-504X, Vol. 135, no 4, 041014- p.Article in journal (Refereed) Published
High cycle fatigue (HCF) due to unforeseen excitation frequencies, underestimated force magnitudes, or a combination of both causes control-stage failures for steam turbine stakeholders. This paper provides an extended design criteria toolbox, as well as validation data, for control-stage design based on experimental data to reduce HCF incidents in partial-admission turbines. The upstream rotor in a two-stage air test turbine is instrumented with pressure transducers and strain gauges. Admission degrees extend from 28.6% to 100%, as one or two admission arcs are simulated by blocking segmental arcs immediately upstream of the first stator vanes with aerodynamically shaped filling blocks. Sweeps across a speed range of 50%-105% of design speed are performed at a constant turbine pressure ratio during simultaneous high-speed acquisition. A forced-response analysis is performed and results presented in Campbell diagrams. Partial admission creates a large number of low-engine-order forced responses because of the blockage, pumping, loading, and unloading processes. Combinations of the number of rotor blades and low-engine-order excitations are the principal sources of forced-response vibrations for the turbine studied here. Altering the stator and/or rotor pitches changes the excitation pattern. We observed that a relationship between the circumferential lengths of the admitted and nonadmitted arcs dictates the excitation forces and may serve as a design parameter.
Place, publisher, year, edition, pages
2013. Vol. 135, no 4, 041014- p.
IdentifiersURN: urn:nbn:se:kth:diva-133975DOI: 10.1115/1.4007599ISI: 000326021900014ScopusID: 2-s2.0-84888066139OAI: oai:DiVA.org:kth-133975DiVA: diva2:664238
FunderSwedish Energy Agency
QC 201311142013-11-142013-11-142013-11-14Bibliographically approved