The development of inflow control devices for improved simulation offlight noise levels during static testing of a HBPR turbofan engine

Atvars, Y.; Rogers, D.R.

doi:10.2514/6.1980-1024

Cited by 6 publications

(8 citation statements)

References 1 publication

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“…Such disturbances, which may also be caused by ingested vortices, wakes and instabilities associated with flow around the inlet lip, produce streng narros.band random tones. Substantial effort has also been applied to the (multiple of shaft frequency) and the circumferential inflow control problem by industry (16)(17)(18)(19)(20)(21)(22)(23) including acoustic mode number corresponding to blade number flyover level comparisons to static projections (22) minus distortion number. Inflow control eliminates the and development of ICD design procedures (23).…”

Section: Mechanism Identificationmentioning

confidence: 99%

Aircraft Turbofan Noise

Groeneweg

Rice

1983

Volume 5: Ceramics; Structures and Dynamics; Controls, Diagnostics and Instrumentation; Education; Process Industries

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Recent advances in the understanding of turbofan noise generation and suppression in aircraft engines are reviewed with particular emphasis on NASA research. The review addresses each link in the chain of physical processes which connect unsteady flow interactions with fan blades to far field noise. Mechanism identification and description, duct propagation, radiation and acoustic suppression are discussed. Recent advances in the experimental technique of fan inflow control assure that in-flight generation mechanisms are not ma.,ked by extraneous sources in static tests. Rotor blade surface pressure and wake velocity measurements aid the determination of the types and strengths of the generation mechanisms. Approaches to predicting or measuring acoustic mode content, optimizing treatment impedance to maximize attenuation, translating impedance into porous wall structure and interpreting far field directivity patterns are illustrated by comparisons of analytical and experimental results. A persistent theme of the review is the interdependence of source and acoustic treatment design to minimize far field noise. Areas requiring further research are discussed and the relevance of aircraft turbofan results to quieting other turbomachinery installations is addressed.

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Section: Mechanism Identificationmentioning

confidence: 99%

Aircraft Turbofan Noise

Groeneweg

Rice

1983

Volume 5: Ceramics; Structures and Dynamics; Controls, Diagnostics and Instrumentation; Education; Process Industries

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“…The development of ICDs has taken place in the 70s and 80s of the last century, when Boeing and Pratt&Whitney cooperated in the development and testing of the JT9D engine for the Boeing 747 [3,4]. In the same period, analytical and experimental work for acoustic measurements with engines in wind tunnels was published by NASA [5,6] and General Electric [7].…”

Section: Introductionmentioning

confidence: 99%

“…A more recent study of engine noise during ground tests is concerned with engine test runs at airports [9]. All of these studies describe an increase of BPF tone levels between ground or wind tunnel tests and flight tests by as much as 12 dB, which are most significant as long as the blade tip speeds remain subsonic [3]. The explanation given is that turbulent or vortical structures with transverse length scales in the order of the blade tip spacing create additional sound sources at the rotor blades.…”

Section: Introductionmentioning

confidence: 99%

“…This is because without an ICD, there is a high number of individual, incoherent sources, while in the configuration with an ICD, a single mode dominates [5]. In free-field or wind tunnel tests without an ICD, the engine shaft frequency may even become instationary, resulting in instantaneous fluctuations of the levels and frequencies of the BPF tones and even the engine thrust [3].…”

Section: Introductionmentioning

confidence: 99%

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Analysis of the influence of inflow distortions on turbofan rotor noise

Grizewski

Behn

Funke

et al. 2019

25th AIAA/CEAS Aeroacoustics Conference

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Acoustic data measured in a fan test facility with and without an inflow control device (ICD) over the inlet were analysed using the cyclostationary analysis technique, which separates the total power into a rotor locked and a fluctuating component. Measurements were taken with an inlet mode ring upstream of the rotor and with far-field microphones for configurations with subsonic and with supersonic fan blade tip speeds. The ICD reduces the fluctuating component and stabilises the rotor locked component of the frequency spectrum at the blade passing frequency and its harmonics. The mode distribution in the inlet and the far-field directivity are also changed when an ICD is installed. The cyclostationary analysis of the mode spectrum in the inlet duct and of the far-field directivity can help to understand the effect of an ICD on the sound field in more detail than a classical spectral analysis.

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“…In recent years, large, sphericalshaped honeycomblscreen structures have been developed by both industry and government to be placed over turbofan inlets during static tests to reduce inflow disturbances and thereby the tone noise arising from these disturbances. (6)(7)(8)(9)(10) Parallel to the development of these structures, the use of wind tunnels to achieve adequate flight simulation of fan noise was also being investigated. Effects of forward speed, angle-of-attack, and advanced inlet design have been addressed in the Ames 40 x 80 foot tunnel, for e~ample.…”

Section: Introductionmentioning

confidence: 99%

Flight effects on fan noise with static and wind tunnel comparisons

Preisser

Chestnutt

1983

8th Aeroacoustics Conference

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A flight test program utilizing a JT15D-1 turbofan engine has been conducted with the objectives of studying flight effects on fan noise and evaluating the simulation effectiveness of both a wind tunnel and a static test configuration that incorporated an inlet control device (ICD). In conjunction with synchronized laser-radar tracking and meteorological profile information, data obtained from a linear array of ground microphones was narrowband-analyzed and ensemble-averaged to yield highly accurate far-field flight acoustic results. Utilizing appropriate corrections, flight. wind tunnel, and static acoustic data were normalized to a static-equivalent, 100-foot radius, lossless reference condition. Data comparisons showed that both the static test with ICD and wind tunnel were generally very effective in simulating flight blade-passage-frequency (BPF) noise levels. However, differences were observed in broadband noise levels and in the details of the multiple-pure-tone harmonics.

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The development of inflow control devices for improved simulation offlight noise levels during static testing of a HBPR turbofan engine

Cited by 6 publications

References 1 publication

Aircraft Turbofan Noise

Aircraft Turbofan Noise

Analysis of the influence of inflow distortions on turbofan rotor noise

Flight effects on fan noise with static and wind tunnel comparisons

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