Jet-Noise Reduction through Liquid-Base Foam Injection

Manson, Lidia; Burge, H. L.

doi:10.1121/1.1912730

Cited by 3 publications

(3 citation statements)

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“…Lightweight cellular materials or foams, that resist fatigue and creep and that can recover completely from large strain over a broad temperature ( T ) range are highly desired for diverse applications including automotive, aerospace, and more recently, soft robotics and flexible electronics. − Foam properties and performances depend strongly on characteristics of the material that makes up the cell walls or struts in addition to the cell geometry and volume fraction . Hence, to meet specific application requirements, foams with various microstructures are fabricated using polymers, metals, and ceramics as struts .…”

Section: Introductionmentioning

confidence: 99%

Graphene-Coated Carbon Nanotube Aerogels Remain Superelastic while Resisting Fatigue and Creep over −100 to +500 °C

2017

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Lightweight, superelastic foams that resist creep and fatigue over a broad temperature range are being developed as structural and functional materials for use in numerous diverse applications. Unfortunately, conventional foams display superelasticity degradation, undergo considerable creep, show fatigue under repeated usage, or fracture over large strains, particularly under significant temperature variations. We report that graphene-coated single-walled carbon nanotube (SWCNT) aerogels remain superelastic, and resist fatigue and creep over a broad temperature range of −100−500 °C. The microstructure of these ultralow density (≈14 mg/mL; corresponding volume fraction ≈9 × 10 −3 ) aerogels is composed of a three-dimensional network of randomly oriented SWCNTs with junctions between SWCNTs coated with 2−5 layers of ≈3 nm long graphene nanoplatelets. Compressive stress (σ) versus compressive strain (ε) curves show that the aerogels fully recover their shapes even when strained by at least 80% over −100−300 °C and 20% at 500 °C, whereas the Young's modulus remains similar over the temperature (−100−500 °C) and strain rate ε̇(0.01−0.16 1/s) ranges. We suggest that under compression, the graphene layers hinder free rotation and irreversible sliding of the SWCNTS about the junctions, leading to bending of the graphene layers, while the struts form new junctions stabilized via van der Waals interactions. When the compressive load is removed, the bent graphene layers provide a restoring force that breaks the junctions created during compression, accounting for full aerogel shape recovery, albeit with hysteresis. The storage (E′) and loss (E″) moduli measured in the linear regime show ultralow damping ratio (tan δ = E″/E′) ≈0.02, and these viscoelastic properties remain constant over three decades of frequencies (0.628−628 rad/s) and across −100−500 °C. The low loss in these aerogels is corroborated by exceptional fatigue resistance for 2000 (5 × 10 5 ) cycles at ε = 60% (1%) from −100−300 °C (−100−500 °C) and creep resistance at least under σ = 20 kPa, for a minimum of 1 min from −100−500 °C. Furthermore, these aerogels retain their exceptional creep resistance under the same creep test conditions but for much longer time of 30 min at all tested temperatures except at 500 °C where they show small creep ε of ≈0.7% with ≈0.8% residual ε. The emergent thermomechanical stability of these aerogels that arises from, in part, microscopic deformations of the graphene-coated junctions, motivate junction modification as a means to control the mechanical properties of CNT foams in general. Furthermore, the temperature-invariant mechanical properties of these aerogels combined with their facile fabrication method, which is readily applicable to other nanotube foams, make this class of aerogels a strong alternative to conventional foams, particularly in environments with large temperature variations.

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Section: Introductionmentioning

confidence: 99%

Graphene-Coated Carbon Nanotube Aerogels Remain Superelastic while Resisting Fatigue and Creep over −100 to +500 °C

2017

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“…However, subsequently, other researchers conducting experiments found that a significant amount of water was required to effectively reduce the engine noise through water injection. In 1971, Manson et al [111,112] attempted to replace the water injection with liquid foam to reduce the water consumption. Experimental results showed that foam injection had excellent absorption effects in the high-frequency range, achieving up to 90% reduction in noise and a maximum noise reduction of 10 dB.…”

Section: Jet Noise Controlmentioning

confidence: 99%

Research Progress on Active Secondary Jet Technology in Supersonic Flow Field of Aerospace Propulsion Systems

Zhu,

Guo,

Sun

et al. 2023

Fluids

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As humans continue to explore the aerospace field, higher demands have been placed on new types of propulsion systems. Meanwhile, active secondary flow has been applied to various aspects of engines over the past seventy years, significantly enhancing engine performance. For the new generation of propulsion systems, active secondary flow remains a highly promising technology. This article provides an overview of the application of active secondary flow in engines, including a review of the past research on the secondary jet flow field, and an introduction of the more prominent applications of the jet in engines and its research progress. Finally, the problems existing in the current application of the secondary jet are summarized, and the future direction of the research is anticipated.

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“…The connection between fluidic injection and mechanical suppressors such as tabbed or chevron nozzles was revisited in the years following 2000. An innovative concept using foam injection was investigated for subsonic and supersonic jet exhausts [13,14,15]. Investigators hypothesized that the injection of liquid foam, a collection of gas bubbles separated by a thin liquid film, resulted in jet noise reduction through the dissipation of sound energy from resonances of the foam structure.…”

Section: Fluidic Injection 1970s and 1980smentioning

confidence: 99%

Fifty Years of Fluidic Injection for Jet Noise Reduction

Henderson

2010

International Journal of Aeroacoustics

109

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The paper reviews 50 years of research investigating jet noise reduction through fluidic injection. Both aqueous and gaseous injection concepts for supersonic and subsonic jet exhausts are discussed. Aqueous injection reduces jet noise by reducing main jet temperature through evaporation and main jet velocity through momentum transfer between water droplets and the main jet. In the launch vehicle environment where large quantities of fluid do not have to be carried with the vehicle, water injection is very effective at reducing excess overpressures. For in-flight use, aqueous injection is problematic as most studies show that either large quantities of water or high injection pressures are required to achieve noise reduction. The most effective noise reduction injection systems require water pressures above 2000 kPa (290 psi) and water-to-mainjet mass flow rates above 10% to achieve overall sound pressure level reductions of roughly 6 dB in the peak jet noise direction. Injection at lower pressure (roughly 1034 kPa or 150 psi) has resulted in a 1.6 EPNdb reduction in effective perceived noise level. Gaseous injection reduces noise through jet plume modifications resulting from the introduction of streamwise vorticity in the main jet. In subsonic single-stream jets, air injection usually produces the largest overall sound pressure level reductions (roughly 2 dB) in the peak jet noise direction. In dual-stream jets, properly designed injection systems can reduce overall sound pressure levels and effective perceived noise levels but care must be taken to choose injector designs that limit sound pressure level increases at high frequencies. A reduction of 1.0 EPNdB has been achieved with injection into the fan and core streams. However, air injection into dual-stream subsonic jets has received little attention and the potential for noise reduction is uncertain at this time. For dual-stream supersonic jets, additional research needs to be conducted to determine if reductions can be achieved with injection pressures available from current aircraft engines.

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Jet-Noise Reduction through Liquid-Base Foam Injection

Cited by 3 publications

References 0 publications

Graphene-Coated Carbon Nanotube Aerogels Remain Superelastic while Resisting Fatigue and Creep over −100 to +500 °C

Graphene-Coated Carbon Nanotube Aerogels Remain Superelastic while Resisting Fatigue and Creep over −100 to +500 °C

Research Progress on Active Secondary Jet Technology in Supersonic Flow Field of Aerospace Propulsion Systems

Fifty Years of Fluidic Injection for Jet Noise Reduction

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