Blade Forced Response Prediction for Industrial Gas Turbines: Part 1 — Methodologies

Moffatt, Stuart; He, L.

doi:10.1115/gt2003-38640

Cited by 26 publications

(14 citation statements)

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“…This paper employs the concept of aerodynamic modal damp ing ratio (AMDR) which is proposed by Moffatt and He [20] to express the magnitude of aerodynamic damping. The AMDR is based on the concept of equivalent viscous damping and can be calculated by Caero 2nXz cfda)…”

Section: Overview Of Energy Methodsmentioning

confidence: 99%

Tip Clearance Effects on Aero-elastic Stability of Axial Compressor Blades

Zhang

Wang

Jiang

et al. 2014

Journal of Engineering for Gas Turbines and Power

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The tip clearance effects on aero-elastic stability of axial compressor blades are investi gated with two independent three-dimensional (3D) flutter prediction approaches: energy method and aero-elastic eigenvalue analysis. An axial compressor rotor which has encountered broken fault caused by flutter during the test rig and flight has been analyzed for five tip gap configurations. A consistent conclusion obtained by these two independent approaches shows the variation trend of aerodynamic damping is not monotonic, but aer odynamic damping at the least stable case shows a trend of first decrease and then increase with the rising of tip gap size, which is different from the results of other researchers and can be utilized to understand the conflict between the conclusions of different research work. Apart from the results of tip clearance effects on aero-elastic sta bility, the employed two methods have revealed the key factors involved in the flutter occurrence from a different perspective.

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Section: Overview Of Energy Methodsmentioning

confidence: 99%

Tip Clearance Effects on Aero-elastic Stability of Axial Compressor Blades

Zhang

Wang

Jiang

et al. 2014

Journal of Engineering for Gas Turbines and Power

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“…A 3D flutter prediction methodology based on energy method will be considered in this article. With the assumption that the blade mode shapes and natural frequencies are unrelated to aerodynamic loads [17], the blade modal analysis is governed by the free vibration equation. Also, because of the compressibility and far smaller density of fluid compared to solid, the mass and stiffness components of fluid are ignored.…”

Section: Numerical Methodologymentioning

confidence: 99%

Flutter prediction in turbomachinery with energy method

Zhang

Wang

2011

Proceedings of the Institution of Mechanical Engineers, Part G:

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The study described in this article is the application of energy method for the prediction of flutter boundary and the effects of some parameters on aeroelastic stability in turbomachinery. The unsteady flow with multi-layer moving grid technique for blade oscillation was undergone for aerodynamic work with the blade passage being discretized using a background fixed H-grid and a body-fitted O-grid moving with the blade. Also, with the assumption of equivalent viscous damping, aerodynamic modal damping ratio was defined based on energy method. The numerical method, with mode shapes and nodal diameter numbers considered, was applied for a transonic compressor rotor stage for which measured flutter boundary on characteristic map was available. It was found that the calculated flutter boundary in the first bending blade mode agreed well with the measured one. Furthermore, it was concluded that the mode shapes and inter-blade phase angle were key parameters on aeroelasticity in turbomachinery and that the flutter instability was mainly induced by the co-action of shock wave and separated flow.

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“…S. Moffatt and L. He (Moffatt and He, 2003) have presented the methodology of an efficient frequency domain approach for prediction of blade forced response in industrial gas turbines. The interaction between fluid and structure is dealt with a loosely coupled manner, and the mode shape is interpolated from finite element analysis to the CFD mesh based on two-dimensional linear interpolation.…”

Section: Recent Workmentioning

confidence: 99%

Determination of Aerodynamic Damping at High Reduced Frequencies

Pan

Petrie-Repar

Mårtensson

et al. 2018

Volume 7C: Structures and Dynamics

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In turbomachines, forced response of blades is blade vibrations due to external aerodynamic excitations and it can lead to blade failures which can have fatal or severe economic consequences. The estimation of the level of vibration due to forced response is dependent on the determination of aerodynamic damping. The most critical cases for forced response occur at high reduced frequencies. This paper investigates the determination of aerodynamic damping at high reduced frequencies. The aerodynamic damping was calculated by a linearized Navier-Stokes flow solver with exact 3D non-reflecting boundary conditions. The method was validated using Standard Configuration 8, a two-dimensional flat plate. Good agreement with the reference data at reduced frequency 2.0 was achieved and grid converged solutions with reduced frequency up to 16.0 were obtained. It was concluded that at least 20 cells per wavelength is required. A 3D profile was also investigated: an aeroelastic turbine rig (AETR) which is a subsonic turbine case. In the AETR case, the first bending mode with reduced frequency 2.0 was studied. The 3D acoustic modes were calculated at the far-fields and the propagating amplitude was plotted as a function of circumferential mode index and radial order. This plot identified six acoustic resonance points which included two points corresponding to the first radial modes. The aerodynamic damping as a function of nodal diameter was also calculated and plotted. There were six distinct peaks which occurred in the damping curve and these peaks correspond to the six resonance points. This demonstrates for the first time that acoustic resonances due to higher order radial acoustic modes can affect the aerodynamic damping at high reduced frequencies.

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Blade Forced Response Prediction for Industrial Gas Turbines: Part 1 — Methodologies

Cited by 26 publications

References 0 publications

Tip Clearance Effects on Aero-elastic Stability of Axial Compressor Blades

Tip Clearance Effects on Aero-elastic Stability of Axial Compressor Blades

Flutter prediction in turbomachinery with energy method

Determination of Aerodynamic Damping at High Reduced Frequencies

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