Recent advancements in turbomachinery forced response analyses

Kielb, Robert E.; Chiang, Hsiao-Wei D.

doi:10.2514/6.1992-12

Cited by 23 publications

(7 citation statements)

References 31 publications

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“…Also, because of the compressibility and far smaller density of fluid compared to solid, the mass and stiffness components of fluid are ignored. Kielb and Chiang [18] provided that the mechanical damping, related to some structural factors, was far smaller than aerodynamic damping, so mechanical damping was out of consideration during the blade flutter analysis. Li and He [19] studied the aerodynamic damping of transonic fan, which pointed out that the aerodynamic damping could be considered to be linear under small oscillating amplitude.…”

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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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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“…Generally the aerodynamic influence coef ficient matrix A is a full-populated cyclic matrix. Kielb and Chiang [21] have shown that the mechanical damp ing is much smaller than aerodynamic damping in turbomachinery (such as bladed disk), so the mechanical damping can be neglected in aero-elastic analysis. Substituting Eq.…”

Section: Fa= Aqamentioning

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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“…Kielb and Chiang [22] presented the summary of previous forced response research, and addressed the needs for further improvements. Since the 1980s, forced response analysis tools are being developed.…”

Section: Forced Response Analysismentioning

confidence: 99%

Aerodynamic and Aeroelastic Effects of Design-Based Geometry Variations on a Low-Pressure Compressor

Eggers

Kim

Bittner

et al. 2020

IJTPP

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In modern aircraft engines, the low-pressure compressor (LPC) is subjected to a flow characterized by strong wakes and secondary flows from the upstream fan. This concerns ultra-high bypass ratio (UHBR) turbofan engines, in particular. This paper presents the aerodynamic and aeroelastic sensitivities of parametric variations on the LPC, driven by the design considerations in the upstream fan. The goal of this investigation was to determine the influence of design-based geometry parameter variations on the LPC performance under realistic inlet flow distributions and the presence of an s-duct. Aerodynamic simulations are conducted at the design and off-design operating points with the fan outflow as the inlet boundary conditions. Based on the aerodynamic results, time-linearized unsteady simulations are conducted to evaluate the vibration amplitude at the resonance operating points. First, the bypass ratio is varied by reducing the channel height of the LPC. The LPC efficiency decreases by up to 1.7% due to the increase in blockage of the core flow. The forced response amplitude of the rotor decreases with increasing bypass ratio due to increased aerodynamic damping. Secondly, the fan cavity leakage flow is considered as it directly affects the near hub fan flow and thus the inflow of the LPC. This results in an increased total-pressure loss for the s-duct due to mixing losses. The additional mixing redistributes the flow at the s-duct exit leading to a total-pressure loss reduction of 4.3% in the first rotor at design point. This effect is altered at off-design conditions. The vibration amplitude at low speed resonance points is increased by 19% for the first torsion and 26% for second bending. Thirdly, sweep and lean are applied to the inlet guide vane (IGV) upstream of the LPC. Despite the s-duct and the variable inlet guide vane (VIGV) affecting the flow, the three-dimensional blade design achieves aerodynamic and aeroelastic improvements of rotor 1 at off-design. The total-pressure loss reduces by up to 18% and the resonance amplitude more than 10%. Only negligible improvements for rotor 1 are present at the design point. In a fourth step, the influence of axial gap size between the stator and the rotor rows in the LPC is examined in the range of small variations which shows no distinct aerodynamic and aeroelastic sensitivities. This finding not only supports previous studies, but it also suggests a correlation between mode shapes and locally increased excitaion with increasing axial gap size. As a result, potential design improvements in future fan-compressor design are suggested.

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Recent advancements in turbomachinery forced response analyses

Cited by 23 publications

References 31 publications

Flutter prediction in turbomachinery with energy method

Flutter prediction in turbomachinery with energy method

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

Aerodynamic and Aeroelastic Effects of Design-Based Geometry Variations on a Low-Pressure Compressor

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