基于声波法测量的炉内燃烧流场重建方法及多场耦合机制

The aerodynamic, temperature, and species concentration fields are coupling, meanwhile independent to each other, which determine the safety and efficiency of combustion in a power-plant boiler. Amongst, the aerodynamic field is the radical and decisive factor; however, its effective measurement is faced to significant challenges. Acoustic method provides a novel non-intrusive, full-field and efficient measurement with the combustion flow fields in furnaces. Whereas, for its big complexity, underdetermined etc., there are just preliminary related studies internationally. For this project, the propagation mechanism of sound in the combustion field in furnace are to be explored, as well as effective reconstruction of the flow fields. This would be based on the successfully carried out research on cold-model studies by the applicant. First, the attenuation and the frequency dispersion of the measuring sound will be dealt with. They are caused by complex ingredients and the medium viscosity from combustion which will be quantitatively studied by theoretic, simulating and experimental methods. On the other hand, the coupling mechanism will be studied between temperature, aerodynamic, and species concentration fields of combustion in furnaces, and also its strong nonlinearity. Then its influence can be achieved to the acoustic reconstruction of the flow field in combustion furnaces. Based on that, in terms of effective apriori knowledge of the combustion flow field, a proper wavelet basis will be studied to fit the solenoidal potential of the vector field, so that a reasonable and optimized inverse model on flow field reconstruction would be built up with the studied field. Then, the fow field is expected to be restored with rare sound projection data. By comparison with acoustic pyrometer for temperature measurement, the acoustic measurement of vector flow field claims having more deep and integral physical and mathematical principles with the field. This research is expected to cast light on the realization of the advanced online acoustic measurement of aerodynamic fields in combustion furnaces, and will also provide scientific reference to researches within related fields.

电站锅炉流场与温度场、成分场等相互耦合又相对独立，决定着燃烧是否安全高效。其中流场是根本决定因素，但其有效测量仍面临巨大挑战。声波法是一种非接触、全场、高效的测量方法，因其复杂性、欠定性等，目前国内外只有少量初步探索。本项目基于申请者已成功开展的冷态条件下的系统工作，研究声在炉内燃烧场中传播机理及其复杂流场的声波法有效测量重建：采用数值模拟与实验相结合，定量研究燃烧介质成分、粘性等引起的复杂声波衰减和频散特性，以及流场、温度场和成分场与声场的耦合机理及非线性特征，探究其对声波法测量的影响规律；基于此，构造速度势场的有效小波基，创新性结合流场物理定律建立优化的逆问题重建模型与算法，由稀少声投影数据进行有效的炉内复杂流场重建。相对于温度场，速度场的声波法测量要求获得更深入全面的物理数学规律作为重建先验知识。该研究可为大型炉内燃烧流场声波法在线检测技术的实现和相关领域物理量测量研究提供基础参考。

电站锅炉流场与温度场、成分场等相互耦合又相对独立，决定着燃烧是否安全高效。其中流场是根本决定因素，它直接决定燃烧温度场和产物的分布。相对研究较多且已有一定应用的温度场测量来说，作为矢量场的速度场测量难度更高，挑战巨大。.声波法流场测量是一种非接触、全场、高效方法，其仅基于少量数据，目前国内外只有初步探索。本项目基于申请者已开展的冷态条件下的工作，研究了声波在炉内燃烧场中传播机理，及相应复杂流场声波法测量重建模型理论。相比声波法温度场测量，其声波传播时间测量精度要高两个数量级或更高，要求更深入全面的场的物理数学先验知识。主要内容：.(1)燃烧介质成分、粘性等引起的复杂声波衰减和频散特性；.(2)炉内燃烧流场、温度场和成分场与声场的耦合机理及非线性特征，声波在其中传播的路径弯曲机理；.(3)构造介质速度势场重建的有效小波基，结合流场先验知识建立优化的模型与算法，由稀少声投影数据进行有效重建。.项目重要研究结果和数据： .(1)实现了炉内空气动力场的小波法重建理论模型。一方面包括确定最佳尺度基函数的小波框架，另一方面创新性地构建了空间小波基，用于场势函数的有效重建。新方法克服了现有文献中模型不能随流场涡尺度变化的缺陷，同时获得了更为准确、可靠的重建结果。该方法预期可适应任意模态场的重建；.(2)研究声波在介质温度、流速空间变化场中传播的弯曲机理，首次实现了在温度、流速耦合场中的有效声路径追踪，使得热态场可靠重建方法得以完整实现；.(3)项目另一个相关的重要工作是，研究实现了基于垂向流速引起声路径弯曲的原理重建管内轴向流速分布的方法，其在单一横断面上布置一定数量声传感器，可有效测量重建出轴向流速沿断面的分布。方法突破了当前原理，更可靠更简单，已由PCT申请获得美国专利授权。.项目预期研究内容尚未最终完成，主要有：一是基于新的小波法场重建模型的实验研究，二是结合声路径弯曲有效追踪的热态流场的测量实验。将在接下来的时间里尽快开展、完成。