tailieunhanh - UNSTEADY AERODYNAMICS, AEROACOUSTICS AND AEROELASTICITY OF TURBOMACHINES Episode 9

Tham khảo tài liệu 'unsteady aerodynamics, aeroacoustics and aeroelasticity of turbomachines episode 9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Study of Shock Movement and Unsteady Pressure on 2D Generic Model 411 of and and that after this range of reduced frequencies the unsteady force damps the blade oscillation. Fujimoto et al. 1997 studied this unsteady fluid structure interaction on a transonic compressor cascade oscillating in a controlled pitching angle vibration. They noticed that although the amplitude of the shock wave displacement did not change much within the range of this experiment the phase lag relative to the blade oscillation increases up to almost 90r as the blade oscillation reduced frequency increases to . Later Hirano et al. 2000 performed other experimental campaigns on this transonic compressor cascade oscillating in a controlled pitching angle vibration. They conclude that the shock wave movement has a large effect on the amplitude and the phase angle of unsteady pressures on the blade surfaces the amplitude of unsteady pressure becomes large upstream of the shock wave but decreases rapidly downstream the phase angle across the shock wave changes largely for the surfaces facing the ft w passages adjacent to the oscillating blade the amplitude of shock wave movement increases following the increase of the reduced frequency and the phase angle relative to the blade displacement lags almost linearly as the reduced frequency increases. In such kind of experiments a driving system is creating an artificial oscillation of the rigid structure whose amplitude and frequency can be controlled. The compressor blade of Lehr and Bolcs 2000 for example is made oscillating in a controlled plunging mode by a hydraulic excitation system. The high-speed pitching vibrator of Hirano et al. 2000 is able to reach a 500Hz frequency of a 2D mode shape controlled oscillation in a linear cascade. In most of the cases the vibrating structures are designed in metal to be close to real applications. Thus large amplitudes of vibration at high oscillation frequencies prompt the failure of the .