Aircraft engine acoustic liner

1999 ◽  
Vol 105 (3) ◽  
pp. 1446
Author(s):  
William H. Hogeboom ◽  
Gerald W. Bielak
Keyword(s):  
Aircraft Engine ◽  
Acoustic Liner

An acoustic liner design methodology based on a statistical source model

2021 ◽  
pp. 1475472X2110238
Author(s):  
Douglas M Nark ◽  
Michael G Jones
Keyword(s):  
Design Methodology ◽  
Three Dimensional ◽  
Aircraft Engine ◽  
Flight Test ◽  
Source Model ◽  
Practical Implementation ◽  
Source Information ◽  
Fan Noise ◽  
Future Design ◽  
Acoustic Liner

The attenuation of fan tones remains an important aspect of fan noise reduction for high bypass ratio turbofan engines. However, as fan design considerations have evolved, the simultaneous reduction of broadband fan noise levels has gained interest. Advanced manufacturing techniques have also opened new possibilities for the practical implementation of broadband liner concepts. To effectively address these elements, practical acoustic liner design methodologies must provide the capability to efficiently predict the acoustic benefits of novel liner configurations. This paper describes such a methodology to design and evaluate multiple candidate liner configurations using realistic, three dimensional geometries for which minimal source information is available. The development of the design methodology has been guided by a series of studies culminating in the design and flight test of a low drag, broadband inlet liner. The excellent component and system noise benefits obtained in this test demonstrate the effectiveness of the broadband liner design process. They also illustrate the value of the approach in concurrently evaluating multiple liner designs and their application to various locations within the aircraft engine nacelle. Thus, the design methodology may be utilized with increased confidence to investigate novel liner configurations in future design studies.

High fidelity modeling tools for engine liner design and screening of advanced concepts

2021 ◽  
pp. 1475472X2110238
Author(s):  
Julian Winkler ◽  
Jeffrey M Mendoza ◽  
C Aaron Reimann ◽  
Kenji Homma ◽  
Jose S Alonso
Keyword(s):  
Aircraft Engine ◽  
High Fidelity ◽  
Treatment Area ◽  
Modeling Tools ◽  
Physical Constraints ◽  
Acoustic Performance ◽  
Acoustic Liner ◽  
Bias Flow ◽  
Honeycomb Cores ◽  
Acoustic Treatment

With aircraft engines trending toward ultra-high bypass ratios, resulting in lower fan pressure ratios, lower fan RPM, and therefore lower blade pass frequency, the aircraft engine liner design space has been dramatically altered. This result is also due to the associated reduction in both the available acoustic treatment area (axial extent) as well as thickness (liner depth). As a consequence, there is current need for novel acoustic liner technologies that are able to meet multiple physical constraints and simultaneously provide enhanced noise attenuation capabilities. In addition, recent advances in additive manufacturing have enabled the consideration of complex liner backing structures that would traditionally be limited to honeycomb cores. This paper provides an overview of engine liner modeling and a description of the key physical mechanisms, with some emphasis on the use of low to high-fidelity tools such as empirical models and commercially available software such as COMSOL, Actran, and PowerFLOW. It is shown that the higher fidelity tools are a critical enabler for the evaluation and construction of future complex liner structures. A systematic study is conducted to predict the acoustic performance of traditional single degree of freedom liners and comparisons are made to experimental data. The effects of grazing flow and bias flow are briefly addressed. Finally, a more advanced structure, a metamaterial, is modeled and the acoustic performance is discussed.

Design and assessment of a distributed active acoustic liner concept for application to aircraft engine noise reduction

2017 ◽  
Vol 141 (5) ◽  
pp. 3643-3643
Author(s):  
Herve Lissek ◽  
Romain Boulandet ◽  
Sami Karkar ◽  
Gaël Matten ◽  
Manuel Collet ◽  
...  
Keyword(s):  
Noise Reduction ◽  
Aircraft Engine ◽  
Engine Noise ◽  
Acoustic Liner

Characterization of a Compliant-Backplate Helmholtz Resonator for An Electromechanical Acoustic Liner

2002 ◽  
Vol 1 (2) ◽  
pp. 183-205 ◽  
Author(s):  
S.B. Horowitz ◽  
T. Nishida ◽  
L.N. Cattafesta ◽  
M. Sheplak
Keyword(s):  
Acoustic Impedance ◽  
Degrees Of Freedom ◽  
Noise Suppression ◽  
Equivalent Circuit Model ◽  
Helmholtz Resonator ◽  
Normal Incidence ◽  
Aircraft Engine ◽  
Rigid Wall ◽  
Piezoelectric Composite ◽  
Acoustic Liner

Passive acoustic liners are currently used to reduce the noise radiated from aircraft engine nacelles. This study is the first phase in the development of an actively-tuned electromechanical acoustic liner that potentially offers improved noise suppression over conventional multi-layer liners. The underlying technical concept is based on the idea that the fundamental frequency of a Helmholtz resonator may be adjusted by adding degrees of freedom (DOF) via substitution of a rigid wall with a piezoelectric composite diaphragm coupled to a passive electrical shunt network. In this paper, a Helmholtz resonator containing a compliant aluminum diaphragm is investigated to provide a fundamental understanding of this two DOF system, before adding complexity via the piezoelectric composite material. Using lumped elements, an equivalent circuit model is derived, from which the transfer function and acoustic impedance are obtained. Additionally, a mass ratio is introduced that quantifies the amount of coupling between the elements of the system. The theory is then compared to experiment in a normal-incidence impedance tube. The experimental results confirm the additional DOF and overall acoustic behavior but also suggest the need for a more comprehensive analytical model to accurately predict the acoustic impedance. Nevertheless, the experiments demonstrate the potential benefits of this approach for the reduction of aircraft engine noise.

High-Temperature Instability of A Cr2Nb-Nb(Cr) Microlaminate Composite

1996 ◽  
Vol 54 ◽  
pp. 374-375
Author(s):  
M. Larsen ◽  
R.G. Rowe ◽  
D.W. Skelly
Keyword(s):  
Heat Treatment ◽  
Solid Solution ◽  
High Temperature ◽  
Elevated Temperatures ◽  
Aircraft Engine ◽  
Lattice Parameter ◽  
Microstructural Stability ◽  
Elevated Temperature Strength ◽  
Cross Sectional ◽  
Bcc Structure

Microlaminate composites consisting of alternating layers of a high temperature intermetallic compound for elevated temperature strength and a ductile refractory metal for toughening may have uses in aircraft engine turbines. Microstructural stability at elevated temperatures is a crucial requirement for these composites. A microlaminate composite consisting of alternating layers of Cr2Nb and Nb(Cr) was produced by vapor phase deposition. The stability of the layers at elevated temperatures was investigated by cross-sectional TEM.The as-deposited composite consists of layers of a Nb(Cr) solid solution with a composition in atomic percent of 91% Nb and 9% Cr. It has a bcc structure with highly elongated grains. Alternating with this Nb(Cr) layer is the Cr2Nb layer. However, this layer has deposited as a fine grain Cr(Nb) solid solution with a metastable bcc structure and a lattice parameter about half way between that of pure Nb and pure Cr. The atomic composition of this layer is 60% Cr and 40% Nb. The interface between the layers in the as-deposited condition appears very flat (figure 1). After a two hour, 1200 °C heat treatment, the metastable Cr(Nb) layer transforms to the Cr2Nb phase with the C15 cubic structure. Grain coarsening occurs in the Nb(Cr) layer and the interface between the layers roughen. The roughening of the interface is a prelude to an instability of the interface at higher heat treatment temperatures with perturbations of the Cr2Nb grains penetrating into the Nb(Cr) layer.

Report and discussion on “A philosophy of aircraft engine manufacture”

1965 ◽  
Vol 44 (7) ◽  
pp. 344
Author(s):  
L.R. Beesly ◽  
Morley ◽  
W.S. Hollis ◽  
Higson Smith ◽  
G.A.J. Witton ◽  
...  
Keyword(s):  
Aircraft Engine

Numerical Comparison of Drag Coefficient between Nacelle Lip-Skin with and without Bias Acoustic Liner

2016 ◽  
Vol 10 (6) ◽  
pp. 390 ◽  
Author(s):  
Qummare Azam ◽  
Mohd Azmi Ismail ◽  
Nurul Musfirah Mazlan ◽  
Musavir Bashir
Keyword(s):  
Drag Coefficient ◽  
Numerical Comparison ◽  
Acoustic Liner
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