基于多频率声表面波传感器阵列的大气颗粒物浓度与粒径分布测量机理研究

As the atmospheric particulate matter pollution becomes a serious problem, and the harmful effects of the particulates varies with their diameters, the measurement of atmospheric particulates of both concentration and size distribution has become a hot researching spot recently. However, the classic perturbation theory by the additional mass cannot predict the frequency perturbation of particles to the resonators working at frequencies over a hundred hertz. Most typical measuring methods for particulates are complex and expensive. By using high-frequency resonance devices, the measurement of particulates could be simpler, highly sensitive and with low power consumption. The coupling mechanism between them has to be studied. In this research, to study the measurement of the concentration and size distribution of atmospheric particulates, high frequency resonator, namely surface acoustic wave (SAW) sensor, has been chosen, to form the array for the studying the fundamental method and basic theory of particulate measurement. By using the characteristic of different sensitivity of SAW for measuring different sized particles, the particle-sensor coupling mechanism in a wide range of particle size will be studied. This theory could serve as the basics of the study of the atmospheric aerosol-sensor coupling model. Finally, the method of using multiple frequency SAW to form an array for the measurement of atmospheric particulates is proposed. By using of proper signal processing technique, the information of concentration and size distribution could be extracted.

近年来大气颗粒物污染问题严重，其造成的危害与颗粒物粒径相关，因此大气颗粒物浓度和粒径分布测量成为研究热点。目前传统的颗粒物测量方法大多复杂、昂贵，而采用高频谐振器件的颗粒物测量方法，具有简单、灵敏度高、功耗低等优点。然而经典的质量增量扰动理论无法正确预测颗粒物对百兆赫兹以上高频谐振器件的频率扰动，两者的耦合扰动机理有待深入研究。本课题基于高频谐振器件——声表面波传感器（SAW），针对大气颗粒物浓度与粒径分布测量问题，开展多频率SAW阵列颗粒物测量的基本方法和基础理论研究。利用SAW在测量不同粒径颗粒物时具有差异化灵敏度的特点，开展宽粒径范围的颗粒物- SAW耦合扰动模型研究。在此基础上，对粒径分布下的大气气溶胶-SAW的耦合扰动机理进行研究。最后，提出基于多频率SAW阵列的大气颗粒物测量方法，通过分析与处理SAW阵列的频率改变组合，提取颗粒物浓度与粒径分布信息。

大气颗粒物是一种影响空气质量的重要污染物，其造成的危害与颗粒物粒径密切相关，对大气颗粒物的浓度和粒径分布测量成为近年来的研究热点。目前能够同时测量浓度与粒径分布的传统方法大多复杂且昂贵。本项目采用结构简单且成本低的高频谐振器件——声表面波传感器（SAW），开展了多频率SAW阵列测量颗粒物浓度与粒径分布的机理与方法研究。研究了宽粒径范围的单个颗粒与SAW的耦合扰动，通过在质量域和弹性域两种耦合态下的界面受力情况、声阻抗和频率改变阐明了颗粒对SAW的扰动机理，指出颗粒粒径、接触尺寸和颗粒材料对SAW频率扰动造成影响；在此基础上，研究了粒径分布符合对数正态分布规律的颗粒物与SAW的耦合扰动机理，揭示了单位质量颗粒物引起的频率改变是质量耦合负频率扰动和弹性耦合正频率扰动竞争的结果，由颗粒物粒径分布参数、材料和SAW频率决定，通过SAW对聚四氟乙烯粉末产生的气溶胶测量实验，展现了SAW对不同粒径分布的颗粒物具有差异化灵敏度的特性；搭建了由315MHz、434MHz、499MHz三种频率SAW组成的阵列，并对0-3μm和A2两种亚利桑那粉尘按7种比例混合产生的粒径分布可控的5种浓度的气溶胶进行了测量实验，对传感器阵列的多维频率改变进行了主成分分析，结果表明不同浓度、粒径分布组合的聚类可以分离，所有聚类在主成分平面中占扇形区域，说明多频SAW阵列能够同时提取浓度和粒径分布信息。