Vibration excitation of axial compressor rotorblades

[摘要] ENGLISH ABSTRACT: Turbomachines are exposed to several environmental factors which maycause failure of components. One of these factors, high cycle fatigue, is oftencaused by bladeutter. This thesis forms part of a project of the EuropeanSeventh Framework Programme (FP7), called project Future. Project Futureis doing theoretical and experimental investigation into the occurrenceofutter in turbomachinery. The objective of this thesis was to evaluate theeffectiveness of a gas injection system as a means of exciting vibrations on the rst stage rotor blades of a compressor. Unsteady simulations of the excitationvelocity perturbations were performed in the Computational Fluid Dynamics(CFD) software, Numeca FINE/Turbo. Experimental testing on the in-houseRofanco compressor test bench, using one prototype of the 15 injector system,provided data that was used to implement boundary conditions and to verifycertain aspects of the unsteady simulation results. The simulation results revealedthe following: the injector bypass frequency was so dominant that theexcitation frequency was hardly detectable in the majority of cases. Furthermore,several secondary frequencies were consistently present. The injectorbypass frequency, as well as the secondary frequencies, occurred as a resultof the convolution of Fast Fourier Transforms. While the injector bypass frequenciescan theoretically be eliminated, it will not be possible to eliminatethe secondary frequencies from the blade response. In conclusion, according tothe CFD results, it will not be possible to excite a single excitation frequencyby making use of anite number of gas injector vibration exciters.

[发布机构] Stellenbosch University