420
Q. Lei et al.
emission method, pressure change method, resistance change method, etc. All of
these methods have unique advantages, however, the acoustic emission detection
method is more suitable for engineering applications because of its simple principle
and high detecting sensitivity [3, 4].
Acoustic emission leak detection is a kind of nondestructive testing technology,
which is mainly used by the amplitude, frequency, energy and other parameters
of the acoustic emission signal generated by the leak to locate and evaluate the
leak. Acoustic emission detection can be divided into two types according to the
signal type [5, 6], burst signal detection and continuous signal detection. The former
mainly focuses on the number of ringing, rise time and other parameters detection, while the latter mainly focuses on the detection of amplitude, energy and other
parameters. In recent years, with the development of digital acquisition technology,
acoustic emission leak detection has developed rapidly and achieved certain research
results. In 1999, Hunaidi and Chu [7] simulated a variety of leak forms of plastic
pipes under certain experimental conditions, and studied the acoustic characteristics of the leak signals, including the characteristics of each frequency component
of the acoustic signal or vibration signal. They studied the relationship between the
frequency components and the leak form, flow rate, pipe pressure, and the relationship
between attenuation rate, wave velocity and frequency. In 2006, Jingpin et al. [8] and
others studied the application of modal acoustic emission technology in the field of
pipeline leak detection, established the model of pipeline leak modal acoustic emission localization, and successfully solved the problem of one-dimensional pipeline
leak location. In 2014, Avramchuk et al. [9] and others studied the application of the
new cross-correlation method to leak location, and solved the problem of pipeline
leak detection through time-frequency correlation function. However, most of these
methods are aimed at the location of leak points, and there are few studies on leak
rate assessment, especially gas leak rate assessment. In the paper, the spectrum analysis method combines with the characteristic parameter analysis method to study the
characteristics of acoustic emission signals produced by gas leak of different sizes
of leak holes, and the spectrum and characteristic parameters of acoustic emission
signals of gas leak are obtained.
37.2 Detection Principle
When there is a leak in the sealed cabin of a spacecraft, the gas leaks from the
sealed structure along the leak path to the vacuum environment outside the cabin
under the action of the pressure difference. When the gas medium passes through
the tiny aperture, its velocity is high. It is in a turbulent state with a large number
of turbulence. The internal stress of the interaction between the turbulence of the
gas causes their respective volume elements to be subjected to equal and opposite
undulating forces, which causes the gas to produce a quadrupole sound source. At
the same time, the interaction of the gas and the channel structure of the leak will
Q. Lei et al.
emission method, pressure change method, resistance change method, etc. All of
these methods have unique advantages, however, the acoustic emission detection
method is more suitable for engineering applications because of its simple principle
and high detecting sensitivity [3, 4].
Acoustic emission leak detection is a kind of nondestructive testing technology,
which is mainly used by the amplitude, frequency, energy and other parameters
of the acoustic emission signal generated by the leak to locate and evaluate the
leak. Acoustic emission detection can be divided into two types according to the
signal type [5, 6], burst signal detection and continuous signal detection. The former
mainly focuses on the number of ringing, rise time and other parameters detection, while the latter mainly focuses on the detection of amplitude, energy and other
parameters. In recent years, with the development of digital acquisition technology,
acoustic emission leak detection has developed rapidly and achieved certain research
results. In 1999, Hunaidi and Chu [7] simulated a variety of leak forms of plastic
pipes under certain experimental conditions, and studied the acoustic characteristics of the leak signals, including the characteristics of each frequency component
of the acoustic signal or vibration signal. They studied the relationship between the
frequency components and the leak form, flow rate, pipe pressure, and the relationship
between attenuation rate, wave velocity and frequency. In 2006, Jingpin et al. [8] and
others studied the application of modal acoustic emission technology in the field of
pipeline leak detection, established the model of pipeline leak modal acoustic emission localization, and successfully solved the problem of one-dimensional pipeline
leak location. In 2014, Avramchuk et al. [9] and others studied the application of the
new cross-correlation method to leak location, and solved the problem of pipeline
leak detection through time-frequency correlation function. However, most of these
methods are aimed at the location of leak points, and there are few studies on leak
rate assessment, especially gas leak rate assessment. In the paper, the spectrum analysis method combines with the characteristic parameter analysis method to study the
characteristics of acoustic emission signals produced by gas leak of different sizes
of leak holes, and the spectrum and characteristic parameters of acoustic emission
signals of gas leak are obtained.
37.2 Detection Principle
When there is a leak in the sealed cabin of a spacecraft, the gas leaks from the
sealed structure along the leak path to the vacuum environment outside the cabin
under the action of the pressure difference. When the gas medium passes through
the tiny aperture, its velocity is high. It is in a turbulent state with a large number
of turbulence. The internal stress of the interaction between the turbulence of the
gas causes their respective volume elements to be subjected to equal and opposite
undulating forces, which causes the gas to produce a quadrupole sound source. At
the same time, the interaction of the gas and the channel structure of the leak will