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.

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.

Classification of Iron Meteorites with High Frequency Ultrasonic Waves

2019 ◽  
Vol 24 (2) ◽  
pp. 277-284
Author(s):  
Dris El Abassi ◽  
Bouazza Faiz ◽  
Abderrahmane Ibhi ◽  
Idris Aboudaoud
Keyword(s):  
Phase Velocity ◽  
Acoustic Impedance ◽  
Nickel Content ◽  
Normal Incidence ◽  
Ultrasonic Pulse ◽  
Ultrasonic Waves ◽  
Iron Meteorites ◽  
Acoustic Transducer ◽  
Pulse Echo ◽  
Non Destructive

We present the results of an ultrasonic pulse-echo technique and its potential to classify iron meteorites into hexahedrites, octahedrites and ataxites by determining their acoustic impedance and phase velocity. Our technique has been adapted from those used in the field of ultrasonic non-destructive investigation of a variety of materials. The main advantage of our technique is that it does not need any preparation of the meteorites like cutting and etching and therefore is rapid, easy and non-destructive. In essence, a broadband acoustic transducer is used in a monostatic pulse-echo configuration which means that both the transducer and the meteorite sample are located in a water bath and adjusted in the way that the ultrasonic pulse shit the meteorite sample at normal incidence. Then the reflected pulses from the front and rear faces of the meteorite sample are measured with the emitting transducer, digitally recorded and processed to analyze the signal. After Fourier transforming the echoed pulses from the front and the rear face of the meteorite sample, the calculated reflection coefficients yield the phase velocity and the acoustic impedance. Our study investigates a variety of iron meteorites collected in Morocco and other countries and it helps to understand how the nickel content of these meteorites affects the acoustic impedance. It reveals that the acoustic impedance of iron meteorites increases with increasing nickel content, so that a further refinement of our technique might have the potential to classify iron meteorites directly and reliably into hexahedrites, octahedrites and ataxites without destroying them.

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

Study on Liquid QCM Sensor Design and its Response Model

2015 ◽  
Vol 742 ◽  
pp. 32-35
Author(s):  
Hai Xia Chen
Keyword(s):  
Transmission Line ◽  
Acoustic Impedance ◽  
Classical Method ◽  
Equivalent Circuit Model ◽  
Impedance Method ◽  
Frequency Change ◽  
Response Model ◽  
Transmission Line Theory ◽  
Depth Analysis ◽  
Line Theory

We use quartz crystal material from a physical point of constitutive equations derived in detail combined with the boundary conditions of the liquid Kanasawa QCM response model and Martin correction BVD equivalent circuit model; then apply transmission line theory and the theory of Acoustic impedance load, the research results can be useful as a QCM-D model, response model and Martin mode, then in-depth analysis of the liquid phase conditions, factors affecting the QCM frequency change, we propose a new method for measuring the density of the unknown liquid viscosity supplement. The main purpose of this chapter is to illustrate the viscous liquid medium under contact conditions, based on transmission line theory and the theory of load Acoustic impedance method compared to the classical method is simple, accurate, and effective.

Influence of Base Thickness on Performance of 1-3-2 Piezoelectric Composite

2010 ◽  
Vol 123-125 ◽  
pp. 121-124 ◽  
Author(s):  
Xin Cheng ◽  
Shuang Shuang Liao ◽  
Shi Feng Huang ◽  
Li Li Guo
Keyword(s):  
Coupling Coefficient ◽  
Acoustic Impedance ◽  
Electromechanical Coupling ◽  
Mechanical Quality Factor ◽  
Piezoelectric Composite ◽  
Electromechanical Coupling Coefficient ◽  
Electromechanical Properties ◽  
Base Thickness ◽  
Mechanical Quality ◽  
Titanate Ceramic

Sulphoaluminate cement and Lead Niobium-Magnesium Zirconate Titanate ceramic [P(MN)]ZT were used as matrix and functional phase respectively to fabricate 1-3-2 cement-based piezoelectric composites by dice and filling technique. The influences of base thickness on piezoelectric properties, electromechanical properties and acoustic impedance properties of the composites were discussed. The results show that as the base thickness increases, the piezoelectric stain factor d33 increases gradually, while the piezoelectric voltage factor g33 decreases. The planar electromechanical coupling coefficient Kp exhibits the trend of decrease, while the thickness electromechanical coupling coefficient Kt and acoustic impedance show the increasing trend. The mechanical quality factor Qm reaches the minimum (1.49) when base thickness is 2.00 mm. The results reveal that the 1-3-2 piezoelectric composite will be suitable for application by changing the base thickness.

scholarly journals Geometry Effects on the Noise Reduction of Helmholtz Resonators

2012 ◽  
Author(s):  
M. Farooqui ◽  
A. Alhamoud ◽  
A. Aliuddin ◽  
S. Mekid
Keyword(s):  
Resonant Frequency ◽  
Noise Reduction ◽  
Degrees Of Freedom ◽  
Helmholtz Resonator ◽  
Shape Effect ◽  
Noise Attenuation ◽  
Two Degrees Of Freedom ◽  
Helmholtz Resonators ◽  
Geometry Effects

In this paper the effect of geometry shape of the Helmholtz resonator on its resonant frequency and on its noise attenuation capability is discussed. The theory of resonant frequency depending on the shape of the vessel of the resonator is verified analytical and numerically using COMSOL for one and two degrees of freedom. The simulation was validated experimentally and has shown very good agreements. Various shapes of the resonators were compared in arrays. A better understanding of the shape effect is shown through simulations.

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