Spectral analysis of turbocompressor-blade flutter

Bifurcation of resonance during flutter of the blades of a turbocompressor rotor

“…As a result, the equality of the eigenfrequency of the blades to one of frequencies (5) and the condition of synchronous vibrations with phase shift (1) are fulfilled.…”

“…1) in the format of the linear vibration theory. The analysis of spectral parameters and construction of the model are combined in the computer technology of the spectral analysis by Prony's method [5]. The spectral Prony expansion of the sequential segment of the temporal series has the form…”

Nonlinear acoustic diametral modes of pressure pulsations during flutter of rotor blades of a turbocompressor

“…3 after t = 58.3 s, frequency ≈ 222 Hz derived from harmonic 2f B generally prevails in residual pulsations of flow pressure. There fore, the presence of the second harmonic of blade bending frequency f B ≈ 81 Hz in the record of vibra tions of blades of the first stage of the rotor investigated in [2] is caused by air flow pressure pulsations (Fig. 2).…”

“…1. It is established [2] that torsion modes of blades with frequency f T ≈ 178 Hz, which is close to harmonic 3f R of the rotor speed, are primarily excited in the time interval t = 4, …, 20 s. With increasing rotor speed, the reso nance departure at frequency f T of the torsion mode of blades occurs, and in time interval t = 17.4, …, 24.6 s flutter with a pos itive damping factor (logarithmic decrement with the opposite sign) occurs at a lower bending frequency of the blades, …”

“…2) are deter mined by the Proni method [2]. The spectral decomposition of an arbitrary segment with length N for the total record of flow pressure pulsations (time series) p k = p(kΔt), k = 1, …, N 0 (below for short, it is con sidered that the time discretization interval Δt = 1) has the form ,…”