Acoustic liner acoustic impedance measurement method under condition of acoustic wave grazing incidence

An impedance measurement, grazing incidence technique, used in the aerospace field

Inactive Publication Date: 2014-03-19
BEIHANG UNIV
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Problems solved by technology

[0018] In order to solve the above problems, the present invention proposes an extraction test method that can meet the measurement requirements and is efficient in a short time, so as to solve the problem of extraction of the acoustic impedance of the acoustic l...

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  • Acoustic liner acoustic impedance measurement method under condition of acoustic wave grazing incidence
  • Acoustic liner acoustic impedance measurement method under condition of acoustic wave grazing incidence
  • Acoustic liner acoustic impedance measurement method under condition of acoustic wave grazing incidence

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Embodiment Construction

[0108] The present invention will be further described in detail below in conjunction with the accompanying drawings.

[0109] Acoustic lining acoustic impedance measuring method of the present invention, as figure 1 As shown, it is realized through the following steps:

[0110] Step 1: Install the acoustic lining;

[0111] Install the sound lining on the sound tube with a rectangular section; if the two opposite side walls of the sound tube are side wall A and side wall B, the sound liner is installed on the side wall A, and the incident surface of the sound liner is flush with the inner wall of the sound tube Flat, such as figure 2 shown.

[0112] Step 2: Measure the sound pressure at the wall surface of the sound tube side wall B;

[0113] Measure the sound pressure of M equally spaced nodes along the sound tube axis at the wall surface of the sound tube side wall B, including the sound pressure amplitude and phase, M≥8, preferably M=8; M nodes are all located in the a...

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Abstract

The invention discloses an acoustic liner acoustic impedance measurement method under a condition of acoustic wave grazing incidence. The method includes the steps of installing an acoustic liner on a side wall of a sound transmitting tube having a rectangular cross section; obtaining wall sound pressure of the position where M measurement points are selected on an opposite side to the side wall where the acoustic liner is located; based on modal characteristics of sound propagation in a tube, enabling the wall sound pressure of the sound tube to be written in an exponential function superimposed form, so that the number of axial wave of sound propagation in the sound tube can be identified through a Prony method; then extracting acoustic impedance in two cases, an when the gas in the sound tube is uniform flow, obtaining the acoustic impedance simply by using a simple dispersion relation and an eigenvalue equation; and when the gas in the sound tube is shear flow, obtaining the acoustic impedance by using an impedance boundary condition after a Pridmore-Brown equation is numerically solved. The advantages of the invention lie in that compared with conventional extraction methods, the acoustic liner acoustic impedance measurement method greatly simplifies the extraction process, reduces the number of measurement points of the wall sound pressure, and is free from the influence of reflection from an outlet; and the invention provides a novel test method for the industry community.

Description

technical field [0001] The invention belongs to the field of aerospace technology, in particular to a method for measuring the acoustic impedance of an acoustic lining under the condition of grazing incidence of sound waves. Background technique [0002] As a sound-absorbing structure, acoustic lining is widely used in architectural design and industrial equipment, and its function is to absorb and reduce noise. For the specific application of aero-engines, the various mechanical properties of the acoustic lining are very strict. It is required that the acoustic lining has the minimum thickness and weight and can withstand considerable pressure and temperature. Of course, the most important thing is to Has excellent noise reduction performance. Aeroengines mainly use local response acoustic linings. Therefore, whether the impedance value of local response acoustic linings can be accurately measured is of great significance to engine noise reduction. [0003] Impedance is d...

Claims

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Application Information

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IPC IPC(8): G01H15/00
Inventor 景晓东赵鑫孙晓峰
Owner BEIHANG UNIV
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