输气管道泄漏声源特性及其变化规律

Characteristics and variation rules of acoustic source of gas pipeline leaks

泄漏声源基本特征及变化规律是声波传播研究的基础,对泄漏信号预处理、特征准确提取及泄漏识别算法改进具有重要意义。为此,以输气管道泄漏喷注产生的声源为研究对象,基于气动声学理论推导泄漏喷注流场中的声源项构成,建立了泄漏声源区域三维仿真模型,基于M？hring声类比提取高马赫数和高雷诺数流场中的等效声源,采用气动噪声混合数值模型进行仿真。分析过程中提取了不同条件下（压力及泄漏孔径）泄漏声源的质点最大速率和平均速率、声压级及声功率级等基本特征参数,并利用管道泄漏模拟测试平台进行验证,明确了泄漏声源基本特征及其变化规律。研究结果表明：（1）泄漏喷注噪声主要是由气体高速喷射湍流和气固耦合引起的,声源以四极子和偶极子为主;（2）针对管道运行压力和泄漏孔径,得出了泄漏声源基本特征参数的变化规律;（3）泄漏产生的能量集中于低频部分,各频段（小于等于200 Hz）能量分布分析结果表明0-20 Hz能量比大于等于0.81,无泄漏及正常输送条件下能量分布趋于平均,可作为泄漏识别的特征指标。

The basic characteristics and variation rules of leakage acoustic source, as the basis of acoustic wave propagation studies, are of great significance in the preprocessing, accurate characteristic extraction and identification algorithm improvement of leakage signals. In this paper, with the acoustic source generated by leakage jet of gas pipeline as the research object, the composition of acoustic source items in the leakage jetting flow field was deduced according to pneumatic acoustic theory and a 3D simulation model of leakage acoustic source was built. By virtue of Mohring acoustic analogy, the equivalent acoustic source was extracted from the flow field of high Mach number and high Reynolds number, and then simulation was conducted by using the mixed numerical model of pneumatic noise. In the process of analysis, the basic characteristic parameters of acoustic source were extracted under different conditions （internal pressure and leakage aperture）, including the maximum velocity and average velocity of mass point, sound pressure level and sound power level. The simulation results were verified by using the pipeline leakage simulation test platform. Finally the basic characteristics and variation rules of leakage acoustic source were figured out as follows. Firstly, the leakage jetting noise is mainly caused by high-speed gas jetting turbu- lence and gas-solid coupling, and the acoustic source is dominantly composed of quadrupole and dipole. Secondly, the variation rules of leakage acoustic source were obtained under different pipeline running pressures and leakage apertures. And thirdly, the energy generated during leakage is concentrated at the low-frequency domain. Analysis results of energy distribution of each frequency band （ 〈 200 Hz） show that the energy ratio of the frequency band 0-20 Hz is greater or equal to 0.81. Under normal or non-leakage conditions, energy dis- tribution tends to be even. The energy ratio can be taken as one characteristic index of leakage identification.