Aerodynamic Detuning Analysis of an Unstalled Supersonic Turbofan Cascade

Hoyniak, D.; Fleeter, Sanford

doi:10.1115/1.3239886

Cited by 16 publications

(6 citation statements)

References 3 publications

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“…wRo = wR e~l"r#~ (9) The resulting unsteady aerodynamic lilt on the two reference airfoils of the detuned cascade is given in Eq. (10).…”

Section: (~)+ (~L + /K=0mentioning

confidence: 99%

Passive Control of Supersonic Throughflow Turbomachine Discrete Frequency Noise Generation by Aerodynamic Detuning

Fleeter¹

1992

Noise Control Eng. J.

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Substantial improvements in supersonic and hypersonic flight vehicles can be obtained by utilizing supersonic throughflow fans and compressors. However, the environmental impact of such future propulsion systems must be considered, such as their noise generation. In this regard, progress in engine noise control is dependent on developing an increased fundamental understanding of turbemachinery noise generation and on novel methods for controlling this noise which do not impose performance penalties on the engine. In this paper, a mathematical model is developed to analyze the effects of aerodynamic detuning on the discrete frequency noise generation of supersonic axial flow rotors, with the detuning achieved by alternating the circumferential spacing of adjacent rotor blades. This model is then applied to baseline uniformly spaced twelve bladed rotors and detuned configurations of these baseline rotors, with the effect of this aerodynamic detuning on the discrete frequency noise generation determined by considering the relative magnitudes of the gust generated unsteady aerodynamic lift. This study demonstrated that alternate blade circumferential spacing aerodynamic detuning is a viable passive discrete frequency noise generation control technique for supersonic throughflow rotors, depending on the specific blade row and flow field geometry.

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“…wRo = wR e~l"r#~ (9) The resulting unsteady aerodynamic lilt on the two reference airfoils of the detuned cascade is given in Eq. (10).…”

Section: (~)+ (~L + /K=0mentioning

confidence: 99%

Passive Control of Supersonic Throughflow Turbomachine Discrete Frequency Noise Generation by Aerodynamic Detuning

Fleeter¹

1992

Noise Control Eng. J.

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“…(6) into Eq. (5) and the subsequent grouping of the sets of full-chord and splitter airfoils leads to the following expression for the total unsteady aerodynamic moment: (7) where a.…”

Section: Aerodynamic Influence Coefficientsmentioning

confidence: 99%

Control of rotor aerodynamically forced vibrations by splitters

Fleeter

Topp

Hoyniak

1988

Journal of Propulsion and Power

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A mathematical model is developed to demonstrate the potential benefit of splitter blades as a passive control mechanism for the flow-induced forced response of supersonic turbomachine rotors. The splitters introduce both aerodynamic and structural detuning and also provide a large measure of control of the location of the Mach wave full-chord airfoil and splitter intersections. The level of aerodynamic detuning is associated with the relative locations of the splitters in the full-chord airfoil passages, with the level of structural detuning a function of the ratio of the natural frequencies of the splitters to that of the full-chord airfoils. The ability of splitters to decrease the amplitude of flow-induced forced response is demonstrated by applying this model to four 12-bladed rotors incorporating splitters, utilizing Verdon's Cascade B flow geometry as a baseline. The critical parameters for decreased forced-response amplitudes of vibration are the chord length and the circumferential and axial locations of the splitters. NomenclatureCg = gust influence coefficient of airfoil n C£ = motion influence coefficient of airfoil n k = reduced frequency, k = coc/LŜ = uniform airfoil spacing v^ = cascade inlet velocity w = gust normal perturbation velocity a = complex oscillatory amplitude a = ae' at ft = interblade phase angle w = gust frequency co 0 = natural torsional frequency of full-chord airfoils Subscripts d = detuned cascade g =gust n = airfoil number R = reference for full-chord airfoils R s = reference for splitters

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“…For this case, the unsteady aerodynamic moments acting on the two reference airfoils of the detuned cascade, R 0 and R 19 are written in terms of influence coefficients in Eq. (9) (9) where the double subscripts express two equations, one for each reference airfoil R 0 and R^ d RoRl are the complex displacements of the reference airfoils; and [CM] denotes the motion-induced influence coefficients.…”

Section: Influence Coefficientsmentioning

confidence: 99%

Supersonic turbomachine rotor flutter control by aerodynamic detuning

Spara

Fleeter

1993

Journal of Propulsion and Power

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A mathematical model is developed to analyze the flutter stability characteristics of an aerodynamically detuned rotor operating in a supersonic inlet flowfield with a supersonic axial component. Alternate-blade aerodynamic detuning is considered, accomplished by alternating the circumferential spacing of adjacent rotor blades. The unsteady aerodynamics are determined by developing an influence coefficient technique which is appropriate for both aerodynamically tuned and detuned rotor configurations. The effects of this detuning on the flutter stability characteristics of supersonic axial flow rotors are then demonstrated by applying this model to baseline 12-bladed rotors. Results show that, dependent on the specific blade row and flowfield geometry, alternate blade aerodynamic detuning is a viable flutter control mechanism for supersonic through-flow rotors.

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Aerodynamic Detuning Analysis of an Unstalled Supersonic Turbofan Cascade

Cited by 16 publications

References 3 publications

Passive Control of Supersonic Throughflow Turbomachine Discrete Frequency Noise Generation by Aerodynamic Detuning

Passive Control of Supersonic Throughflow Turbomachine Discrete Frequency Noise Generation by Aerodynamic Detuning

Control of rotor aerodynamically forced vibrations by splitters

Supersonic turbomachine rotor flutter control by aerodynamic detuning

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