The acoustic impedance of perforated plates under various flow conditions relating to combustion chamber liners

2016 ◽  
Vol 106 ◽  
pp. 144-154 ◽  
Author(s):  
Chris Lawn
Keyword(s):  
Combustion Chamber ◽  
Acoustic Impedance ◽  
Flow Conditions ◽  
Perforated Plates

High Speed Flow through Perforated Plates

1960 ◽  
Vol 64 (590) ◽  
pp. 103-105
Author(s):  
P. G. Morgan
Keyword(s):  
Pressure Drop ◽  
High Speed ◽  
Perforated Plate ◽  
Wire Mesh ◽  
Flow Conditions ◽  
High Speed Flow ◽  
Perforated Plates ◽  
Speed Flow ◽  
Flow Through ◽  
Points Of View

The flow through porous screens has been widely studied from both the theoretical and experimental points of view. The most widely used types of screen are the wire mesh and the perforated plate, and the majority of the literature has been concerned with the former. Several attempts have been made to correlate the parameters governing the flow through such screens, i.e. the pressure drop, the flow conditions and the geometry of the mesh.

A New Type of Muffler Based on Microperforated Tubes

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
S. Allam ◽  
M. Åbom
Keyword(s):  
Acoustic Impedance ◽  
Noise Control ◽  
Wave Impedance ◽  
Sound Waves ◽  
Submillimeter Range ◽  
Perforated Plates ◽  
Characteristic Wave ◽  
Standard Temperature ◽  
New Type ◽  
Temperature And Pressure

Microperforated plate (MPP) absorbers are perforated plates with holes typically in the submillimeter range and perforation ratios around 1%. The values are typical for applications in air at standard temperature and pressure (STP). The underlying acoustic principle is simple: It is to create a surface with a built in damping, which effectively absorbs sound waves. To achieve this, the specific acoustic impedance of a MPP absorber is normally tuned to be of the order of the characteristic wave impedance in the medium (∼400 Pa s/m in air at STP). The traditional application for MPP absorbers has been building acoustics often combined with a so called panel absorber to create an absorption peak at a selected frequency. However, MPP absorbers made of metal could also be used for noise control close to or at the source for noise control in ducts. In this paper, the possibility to build dissipative silencers, e.g., for use in automotive exhaust or ventilation systems, is investigated.

EFFECT OF GRAZING–BIAS FLOW INTERACTION ON ACOUSTIC IMPEDANCE OF PERFORATED PLATES

2002 ◽  
Vol 254 (3) ◽  
pp. 557-573 ◽  
Author(s):  
X. SUN ◽  
X. JING ◽  
H. ZHANG ◽  
Y. SHI
Keyword(s):  
Acoustic Impedance ◽  
Perforated Plates ◽  
Flow Interaction ◽  
Bias Flow

scholarly journals Wet subglacial bedforms of the NE Greenland Ice Stream shear margins

2019 ◽  
Vol 60 (80) ◽  
pp. 91-99 ◽  
Author(s):  
Kiya L. Riverman ◽  
Sridhar Anandakrishnan ◽  
Richard B. Alley ◽  
Nicholas Holschuh ◽  
Christine F. Dow ◽  
...  
Keyword(s):  
Ground Penetrating Radar ◽  
Acoustic Impedance ◽  
Impedance Analysis ◽  
Flow Conditions ◽  
Lateral Shear ◽  
Ice Flow ◽  
Ice Stream ◽  
Water Saturated ◽  
Ground Penetrating

AbstractWe describe elongate, wet, subglacial bedforms in the shear margins of the NE Greenland Ice Stream and place some constraints on their formation. Lateral shear margin moraines have been observed across the previously glaciated landscape, but little is known about the ice-flow conditions necessary to form these bedforms. Here we describe in situ sediment bedforms under the NE Greenland Ice Stream shear margins that are observed in active-source seismic and ground-penetrating radar surveys. We find bedforms in the shear margins that are ~500 m wide, ~50 m tall, and elongated nearly parallel to ice-flow, including what we believe to be the first subglacial observation of a shear margin moraine. Acoustic impedance analysis of the bedforms shows that they are composed of unconsolidated, deformable, water-saturated till. We use these geophysical observations to place constraints on the possible formation mechanism of these subglacial features.

A New Method for Measuring Acoustic Impedance of Perforated Plates with Grazing Flow

2018 ◽  
Vol 2018.56 (0) ◽  
pp. 703
Author(s):  
Daisuke SHIRAGA ◽  
Shunsuke NAKAMURA ◽  
Shotaro YAMAZAKI ◽  
Shinji AKAMATSU ◽  
Yuki MITSUI ◽  
...  
Keyword(s):  
Acoustic Impedance ◽  
New Method ◽  
Perforated Plates ◽  
Grazing Flow

Research on the Absorption Characteristic of Three-Layer Microperforate Plate of the Automotive Body

2011 ◽  
Vol 201-203 ◽  
pp. 2160-2166
Author(s):  
Cong Yun Zhu
Keyword(s):  
Absorption Coefficient ◽  
Equivalent Circuit ◽  
Acoustic Impedance ◽  
Perforated Plate ◽  
Absorption Characteristic ◽  
Perforated Plates ◽  
Automotive Body ◽  
Different Thickness

Three-layer micro perforated plate of the automotive body is researched. Acoustic impedance of the three-layer microperforated plate of the automotive body is attained according to the equivalent circuit, thus absorption coefficient is attained. Different microperforated plate with different porosity, different diameter, different thickness, different depth of cavity of the automotive body is analyzed and some conclusion is drawn to applied some theory to design these types of the micro perforated plates of the automotive body.

Experimental Analysis of V- to M-Shape Transition of Premixed CH4/H2/Air Swirling Flames

2013 ◽  
Author(s):  
T. F. Guiberti ◽  
L. Zimmer ◽  
D. Durox ◽  
T. Schuller
Keyword(s):  
Combustion Chamber ◽  
Bluff Body ◽  
Lewis Number ◽  
Critical Value ◽  
Operating Conditions ◽  
Chamber Wall ◽  
Sudden Expansion ◽  
Shape Transition ◽  
Flow Conditions ◽  
Swirling Flames

Lean premixed swirling flames stabilized at the sudden expansion of a combustion chamber generally take a V or a M shape, depending on the burner geometry and flow conditions. It is not rare to observe transitions between these shapes as operating conditions of the combustor are modified, but the governing mechanisms of these transitions are not well understood. An experimental study is conducted to analyze the transition from an initially V-shaped flame to a M-shaped flame for swirling flames fed by CH4/H2/air mixtures anchored on a central bluff body when flow conditions and geometrical elements of the combustor are modified. Two situations are identified depending whether strong flame wall interactions take place at the quartz tube confining the flame. When the V-flame front is impinging and quenched at the combustion chamber wall, the transition to a M-shape is triggered by a flashback mechanism along the wall followed by the propagation of the flame tip along the outer shear-layer of the swirling jet in the direction of the external rim of the burner. This mechanism is controlled by the mixture Lewis number, a Karlovitz number based on the velocity gradient at the combustor wall, the swirl imparted to the flow and the cross section area ratio between the injection unit and combustion chamber defining a confinement ratio. Experiments conducted at a given mixture Lewis number indicate that the onset of flashback is determined by decreasing the Karlovitz number under a critical value. It is shown that this critical value decreases when the Lewis number increases, but it also depends on the confinement ratio and swirl number. In the absence of direct interaction between the V-flame tip and the chamber wall, the situation differs and this flashback mechanism along the combustion chamber wall ceases. Attempts are made in this case to identify the governing parameters triggering the V- to M-shape transition for small confinement ratios.

Acoustic impedance of perforated plates in the presence of bias flow

2019 ◽  
Vol 446 ◽  
pp. 159-175 ◽  
Author(s):  
Zhixiang Chen ◽  
Zhenlin Ji ◽  
Hongpu Huang
Keyword(s):  
Acoustic Impedance ◽  
Perforated Plates ◽  
Bias Flow
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