MASS SENSITIVITY IMPROVEMENT OF A DEVELOPED SURFACE ACOUSTIC WAVE BASED PARTICULATE MATTER 2.5 MONITOR
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- 英文论文题名：MASS SENSITIVITY IMPROVEMENT OF A DEVELOPED SURFACE ACOUSTIC WAVE BASED PARTICULATE MATTER 2.5 MONITOR
- 论文作者：Wen-chang HAO ; Zhong NIE ; Jiu-ling LIU ; Ming-hua LIU ; Shi-tang HE
- 英文论文作者：Wen-chang HAO ; Zhong NIE ; Jiu-ling LIU ; Ming-hua LIU ; Shi-tang HE ; Institute of Acoustics ; Chinese Academy of Sciences ; University of Science and Technology Beijing
- 年：2016
- 作者机构：Institute of Acoustics, Chinese Academy of Sciences;University of Science and Technology Beijing;
- 英文论文关键词：Particulate matter ; Surface acoustic wave ; Thermophoresis ; Deposition distribution ; Mass sensitivity
- 会议召开时间：2016-10-21
- 会议录名称：2016年全国压电和声波理论及器件应用研讨会论文摘要集
- 英文会议录名称：Abstract Book of 2016 Symposium on Piezoelectricity, Acoustic Waves and Device Applications
- 语种：英文
- 分类号：X851
- 学会代码：AGLU
- 会议名称：2016年全国压电和声波理论及器件应用研讨会
- 会议地点：中国陕西西安
- 主办单位：中国力学学会、中国声学学会、IEEE UFFC分会
- 学会名称：中国力学学会
- 页数：2
- 文件大小：181k
- 原文格式：D
- 会议级别：全国
摘要
Background, Motivation and Objective Particulate matter(PM) 2.5, also known as fine particle, refers to particles with a nominal aerodynamic diameter less than or equal to 2.5μm, which has adverse impact on air environment. To control the PM_(2.5) pollutions, the monitoring work, especially extensive area monitoring, is indispensable. In the paper, a novel PM_(2.5) monitor based on a surface acoustic wave(SAW) detector was developed, which consisted of a SAW dual-resonator oscillator, a thermophoresis unit and a virtual impactor. For the SAW based PM_(2.5) monitor, the mass sensitivity is a key parameter, which is closely related to the operation frequency of the SAW detector, the thermophoresis collection efficiency and the SAW velocity shift caused by the deposited particles. Obviously, to increase the SAW velocity shift, the particle deposition distribution on the SAW detector surface should be highly regarded, which eventually improves the mass sensitivity of the sensor. Thus, in this contribution, an optimal structure of the PM_(2.5) monitor by considering the particle deposition distribution was presented. Statement of Contribution/Methods The schematic of the SAW based PM_(2.5) monitor is shown in Fig.1. When the airborne particles are separated by size in the virtual impactor, the PM_(2.5) is transferred to the plate-to-plate thermophoretic precipitator. By the thermophoresis effect, the mass loading from the PM_(2.5) deposited results in the SAW velocity shift, and accordingly, the change of the oscillation frequency is utilized to PM_(2.5) evaluations. Based on the thermophoretic deposition efficiency formula given by Tsai et al., a thermophoretic precipitator dimensions for particle diameter of 2.5 μm under 100% collection efficiency condition is shown in Fig. 2. Considering the surface size of a SAW device, the dimensions of the precipitator is set to 200μm′ 3.6mm ′ 6.3mm. To describe the movement of the particles to the surface of SAW detector, a 3D finite element method(FEM) with the commercial software COMSOL was used to model the structure, shown in Fig. 3. By using the Non-Isothermal Flow and the Particle Tracing for Fluid Flow packages with the flow rate of 6 m L/min, the deposition distributions of particles with diameter of 2.5 μm in the original and optimal structures were obtained, shown in Fig. 4. In the optimal structure, the position of the heat source was moved to the right for 2 mm to guarantee the particles high-density distributed area corresponds with the optimal sensitive area of the SAW sensor, namely the center of the cold plate. Results A cigarette was lit and collected in the particle chamber to generate the tobacco smoke before testing. A photograph taken by an optical microscope of the surface of an original prototype exposed to high concentration of tobacco smoke is shown in Fig. 4. The particles distributed densely at the entrance of the thermophoretic precipitator shown in a yellow circle, which is in accord with the theoretical result. Discussion and Conclusions This paper presents a SAW based PM_(2.5) monitor. The structure optimization for improving the mass sensitivity of the sensor by considering the particle distribution deposited by thermophoresis on the SAW detector was analyzed and verified in experiments. Based on the theoretical results, an optimal monitoring structure was obtained and a higher mass sensitivity of the PM_(2.5) monitor was achieved theoretically.
Background, Motivation and Objective Particulate matter(PM) 2.5, also known as fine particle, refers to particles with a nominal aerodynamic diameter less than or equal to 2.5μm, which has adverse impact on air environment. To control the PM_(2.5) pollutions, the monitoring work, especially extensive area monitoring, is indispensable. In the paper, a novel PM_(2.5) monitor based on a surface acoustic wave(SAW) detector was developed, which consisted of a SAW dual-resonator oscillator, a thermophoresis unit and a virtual impactor. For the SAW based PM_(2.5) monitor, the mass sensitivity is a key parameter, which is closely related to the operation frequency of the SAW detector, the thermophoresis collection efficiency and the SAW velocity shift caused by the deposited particles. Obviously, to increase the SAW velocity shift, the particle deposition distribution on the SAW detector surface should be highly regarded, which eventually improves the mass sensitivity of the sensor. Thus, in this contribution, an optimal structure of the PM_(2.5) monitor by considering the particle deposition distribution was presented. Statement of Contribution/Methods The schematic of the SAW based PM_(2.5) monitor is shown in Fig.1. When the airborne particles are separated by size in the virtual impactor, the PM_(2.5) is transferred to the plate-to-plate thermophoretic precipitator. By the thermophoresis effect, the mass loading from the PM_(2.5) deposited results in the SAW velocity shift, and accordingly, the change of the oscillation frequency is utilized to PM_(2.5) evaluations. Based on the thermophoretic deposition efficiency formula given by Tsai et al., a thermophoretic precipitator dimensions for particle diameter of 2.5 μm under 100% collection efficiency condition is shown in Fig. 2. Considering the surface size of a SAW device, the dimensions of the precipitator is set to 200μm ′ 3.6mm ′ 6.3mm. To describe the movement of the particles to the surface of SAW detector, a 3D finite element method(FEM) with the commercial software COMSOL was used to model the structure, shown in Fig. 3. By using the Non-Isothermal Flow and the Particle Tracing for Fluid Flow packages with the flow rate of 6 m L/min, the deposition distributions of particles with diameter of 2.5 μm in the original and optimal structures were obtained, shown in Fig. 4. In the optimal structure, the position of the heat source was moved to the right for 2 mm to guarantee the particles high-density distributed area corresponds with the optimal sensitive area of the SAW sensor, namely the center of the cold plate. Results A cigarette was lit and collected in the particle chamber to generate the tobacco smoke before testing. A photograph taken by an optical microscope of the surface of an original prototype exposed to high concentration of tobacco smoke is shown in Fig. 4. The particles distributed densely at the entrance of the thermophoretic precipitator shown in a yellow circle, which is in accord with the theoretical result. Discussion and Conclusions This paper presents a SAW based PM_(2.5) monitor. The structure optimization for improving the mass sensitivity of the sensor by considering the particle distribution deposited by thermophoresis on the SAW detector was analyzed and verified in experiments. Based on the theoretical results, an optimal monitoring structure was obtained and a higher mass sensitivity of the PM_(2.5) monitor was achieved theoretically.
Background, Motivation and Objective Particulate matter(PM) 2.5, also known as fine particle, refers to particles with a nominal aerodynamic diameter less than or equal to 2.5μm, which has adverse impact on air environment. To control the PM_(2.5) pollutions, the monitoring work, especially extensive area monitoring, is indispensable. In the paper, a novel PM_(2.5) monitor based on a surface acoustic wave(SAW) detector was developed, which consisted of a SAW dual-resonator oscillator, a thermophoresis unit and a virtual impactor. For the SAW based PM_(2.5) monitor, the mass sensitivity is a key parameter, which is closely related to the operation frequency of the SAW detector, the thermophoresis collection efficiency and the SAW velocity shift caused by the deposited particles. Obviously, to increase the SAW velocity shift, the particle deposition distribution on the SAW detector surface should be highly regarded, which eventually improves the mass sensitivity of the sensor. Thus, in this contribution, an optimal structure of the PM_(2.5) monitor by considering the particle deposition distribution was presented. Statement of Contribution/Methods The schematic of the SAW based PM_(2.5) monitor is shown in Fig.1. When the airborne particles are separated by size in the virtual impactor, the PM_(2.5) is transferred to the plate-to-plate thermophoretic precipitator. By the thermophoresis effect, the mass loading from the PM_(2.5) deposited results in the SAW velocity shift, and accordingly, the change of the oscillation frequency is utilized to PM_(2.5) evaluations. Based on the thermophoretic deposition efficiency formula given by Tsai et al., a thermophoretic precipitator dimensions for particle diameter of 2.5 μm under 100% collection efficiency condition is shown in Fig. 2. Considering the surface size of a SAW device, the dimensions of the precipitator is set to 200μm ′ 3.6mm ′ 6.3mm. To describe the movement of the particles to the surface of SAW detector, a 3D finite element method(FEM) with the commercial software COMSOL was used to model the structure, shown in Fig. 3. By using the Non-Isothermal Flow and the Particle Tracing for Fluid Flow packages with the flow rate of 6 m L/min, the deposition distributions of particles with diameter of 2.5 μm in the original and optimal structures were obtained, shown in Fig. 4. In the optimal structure, the position of the heat source was moved to the right for 2 mm to guarantee the particles high-density distributed area corresponds with the optimal sensitive area of the SAW sensor, namely the center of the cold plate. Results A cigarette was lit and collected in the particle chamber to generate the tobacco smoke before testing. A photograph taken by an optical microscope of the surface of an original prototype exposed to high concentration of tobacco smoke is shown in Fig. 4. The particles distributed densely at the entrance of the thermophoretic precipitator shown in a yellow circle, which is in accord with the theoretical result. Discussion and Conclusions This paper presents a SAW based PM_(2.5) monitor. The structure optimization for improving the mass sensitivity of the sensor by considering the particle distribution deposited by thermophoresis on the SAW detector was analyzed and verified in experiments. Based on the theoretical results, an optimal monitoring structure was obtained and a higher mass sensitivity of the PM_(2.5) monitor was achieved theoretically.
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