【作者】 刘杰；

【导师】 柴钰；

【作者基本信息】 西安科技大学 ， 控制理论与控制工程， 2020， 硕士

【摘要】 工业生产过程中会伴随大量易燃易爆或有毒气体的产生,为了防止该类气体带来的危害,则需要精确检测出该类气体含量,本文采用仿真与实验结合的方法研究了纳米尖端、微米间距场域下电离式气体传感器的内部工作机理、结构优化以及该类传感器对低浓度下CH4检测的可行性。主要研究内容如下。(1)在该类传感器内部工作机理尚不完善的情况下,本文首先对纳米尖端、微米间距场域下N2-O2混合气体空间放电进行了二维直流放电建模仿真,研究了传感器的内部工作机理以及极间距对空间放电的影响;其次为忧化传感路的场致发射特性,对放电结构进行了二维静电场建模仿真,研究了底电极半径对场致发射的影响;最后结合极间距研究结果研究了底电极半径对空间放电的影响,仿真结果表明,随着底电极半径减小纳米管管身开始发生二次电子发射,且空间电流密度呈现出先增大后减小的趋势。(2)为了验证前期仿真结果,首先以阳极氧化法制备出的TiO2纳米管薄膜为电极材料组装了传感器,搭建了气仿体放电实验系统,并对不同极间距下的N2-O2混合气体空间放电进行了实验验证,实验结果表明:当极间距在30μm-150μm范围内时,存在最优极间距与仿真结果相似;其次对不同底电极半径下N2-O2混合气体空间放电进行了实验验证,实验结果表明;当阳极表面积在10mm×10mm-50mm范围内时,存在最优底电极半径与仿真结果相似;最后通过实验验证了传感器结构优化前与优化后对空间电离性能的影响并得出;优化后的传感器其放电电流相比于优化前的传感器提高了13倍,(3)由于CH4放电存在爆炸风险,为了研究传感器优化后对低浓度下CH4检测的可行性,本文主要对CH4浓度在1×103ppm～1×104ppm范围内的CH4-N2混合气体进行了二维仿真研究,仿真结果表明:随着CH4浓度增加,优化前后的传感器其空间电流密度都呈现出单调递增趋势,且优化后传感器的灵敏度与线性度要优于优化前的传感器。本文这种结合实际应用的仿真能够从微观尺度对放电机理进行解释,有效地弥补了实验诊断的不足,对实际产品的开发和优化具有一定的指导意义。更多还原

【Abstract】 The industrial production process will be accompanied by the production of a large number of flammable,explosive or toxic gases.in order to prevent the harm caused by such gases,it is necessary to accurately detect the content of such gases.This article uses a combination of simulation ahd experiment methads to study the nano tip,the internal working mechanism and structure optimization of the ionization gas sensor in the field of micron spacing,and the feasibility of this type of sensor to detect CH4 at low concentration,The main research contents are as follows:(1)When the internal working mechanism of this type of sensor is not yet perfect,this article first carried out two-dimensional DC discharge modeling and simulation in the N2-O2 mixed gas space discharge under the nano-tip and micron pitch field,and studied the internal of the sensor The working mechanism and the influence of the electrode spacing on the space discharge:secondly.to optimize the field emission characteristics of the sensor,the dicharge structure is modeled and simulated by a two-dimensional eletrostatic field,and the influence of the bottom electrode rading on the field emission is studied;finally,the electrode spacing is combined The research results have studied the influence of the bottom electrode radius on the space discharge.The simulation results show that as the bottom electrode radius decres,the nanotube body begins to emit secondary electrons,and the space current density first inereses and then decrease.(2)In order to verify the simulation results,first,the sensor was assembled using the TiO2 nanotube film prepared by anodization as the electrode material,a gas discharge experimental system was built and the space discharge of N2-O2 mixed gas at different electrode spacings was expcrimentally verified,the experimenal results show that When the distance is in the range of 30μm～150μm the optimal electrode spacing is similar to the simulation results;then,the space discharge of N2-O2 mixsted gas different bottom electrode radii was experimentaly verified,the exoermental results show that when the sutface area of the anode is the range of 10mm×10mm～50mm×50mm,the optimal bottom electrode radius is similar to the simulation results;finally,the effect of the structure of the sensor before and after optimization on the ionization performance of the space was verified by experiments and it was concluded that the discharge current of the optimized sensor compared to the optimized the front sensor is increased by 1.3 times.(3)There is a risk of explosion due to CH4 discharge,in order to study the feasibility of detecting CH4 at low concentration before and after sensor optimization,this paper mainly conducts a two-dimensional simulation study of CH4-N2 mixed gas with CH4 concentration in the range of 1×103ppm～1×104ppm,the simulation results show that:as the concentration of CH4 increases,the spatial current density of the sensors before and after optimization shows a monotonous increasing trend,and the sensitivity and linearity of the optimized sensor are better than those before optimization.In this paper,the simulation combined with practical application can explain the discharge mechanism from the micro scale,which effectively make up for the shortage of experimental diagnosis and has certain guiding significance for the development and optimization of actual products.更多还原