基于湍声耦合机理的输气管道泄漏声波传播规律研究

Based on the sound-turbulence interaction mechanism, a fundamental and theoretical research on the propagation characteristics of acoustic waves for natural gas pipelines will be made in the project. First, the non-equilibrium sound-turbulence interaction model in low Mach number pipe flow with natural gas will be established when the sound-turbulence interaction is taken into consideration, and the perturbation Reynolds stress will be solved and obtained by the model, through which the acoustic propagation diffusion caused by the non-equilibrium process will be presented, including the one resulted from the background turbulence and another triggered by the perturbations that come from the effects introduced by the wave oscillations on the turbulent flows. Then using the non-equilibrium model, the relationships between the perturbation Reynolds stress and the wave number, the waveform can be bridged, respectively. Consequently, a theoretical system of acoustic propagation characteristics based on the sound-turbulence interaction mechanism can be concluded, through which the new leak location methods will be proposed to solve the key problems in the leak location methods. By using theoretical derivation, numerical simulation and experimental research methods, the initial characteristics of the acoustic waves will be described by the amplitude calculation formula and time factor expression; a piecewise function of sound-turbulence interaction models with the equivalent thickness will be established and modified by the actual field conditions; the relationships between the perturbation Reynolds stress and the amplitude attenuation, and the time factor variation will be built, through which the propagation law will be obtained; the new leak location methods based on the exponential attenuation law, the attenuation coefficients differences, as well as the acoustic velocities differences will be proposed. All of these will provide a theoretical foundation and technical support for the safety operation of the natural gas pipelines.

本课题基于湍声耦合机理，进行输气管道泄漏声波传播规律的基础理论研究。首先建立输气管道低马赫数下湍流与泄漏声波相互作用时的非稳态湍声耦合模型并求解脉动雷诺应力，用以表征湍声耦合的非稳态过程对声波传播的耗散作用，既包括湍流引发的声波耗散，又包括声波对湍流的扰动引发的声波耗散。然后通过非稳态湍声耦合模型建立脉动雷诺应力与声波波数及波形的关系，从而建立基于湍声耦合机理的声波传播规律理论体系。并据此提出泄漏定位方法，进而解决泄漏定位的关键问题。课题拟通过理论推导、数值模拟和实验研究，描述声波传播初始状态，总结声波幅值计算公式和时间系数表达式；建立湍声耦合模型随当量厚度变化的“分段函数”，并根据实际条件进行修正；建立脉动雷诺应力与声波幅值衰减和时间系数变化之间的关系，得到声波传播规律；提出基于声波异向传播指数衰减、基于衰减因子差和基于声速差的泄漏定位方法，为输气管道的安全运行提供理论基础和技术保障。

输气管道受到腐蚀、第三方破坏等作用而破裂会产生气体泄漏，泄漏检测与定位具有十分重要的安全环保意义。实现输气管道泄漏检测与定位的关键问题是如何考虑湍声耦合机理建立准确的声波传播模型，包括湍声耦合模型的建立、脉动雷诺应力的求解、声波传播规律的研究。湍声耦合机理是声波传播规律研究的关键所在。本项目围绕“湍声耦合机理”，从理论推导、数值模拟和实验研究三个方面开展研究工作。. 首先，采用动网格技术建立了基于气固耦合作用的泄漏发声理论机制，揭示了偶极子声源和四极子声源的比重及变化关系；提出了“幅值”和“时间系数”两个参数描述泄漏声波的初始状态，得到了输气管道泄漏声波传播初始状态特征，尤其考虑了外部环境为土壤和水时的泄漏声波的产生特性，总结推导了声波幅值计算的半经验半理论公式和时间系数表达式，通过计算模型得到的计算幅值的误差都在15%以内；进一步，建立了泄漏工况与其他工况下声波特征数据库；研发了幅值高、频率宽的动态压力传感器。. 其次，建立了非稳态湍声耦合模型并求解得到了脉动雷诺应力，得到了湍声耦合模型随当量厚度变化的“分段函数”，建立了湍声耦合机理的理论体系，将声学边界层厚度与湍流粘性底层当量尺度之比定义为“当量厚度”，结合不同工况，如无粘静止、有粘静止、无粘流动、有粘均匀流动、有粘非均匀流动时，得到了不同当量厚度下声波幅值衰减因子不同的表达形式。. 然后，建立了脉动雷诺应力与波数以及时间系数的定量关系，得到了基于湍声耦合模型的声波幅值指数衰减模型，时间系数变化模型以及声速公式修正模型，总结了基于湍声耦合机理的声波传播规律，声波幅值衰减因子计算误差在2%以内。. 最后，提出基于声波异向传播指数衰减、基于衰减因子差和基于声速差的泄漏定位方法，总结了快速准确的基于声波传播规律的泄漏定位技术。定位精度提高到0.1%。. 综上，基于湍声耦合机理的声波传播规律研究为输气管道的安全运行提供了理论基础和技术保障。