基于气溶胶理论的热膜气体流量传感器颗粒物沉积机理与实验研究

Aiming at the measurement accuracy decrease after the hot-film air flow sensor is contaminated, the deposition mechanism of fine particles such as dust and oil mist on the hot-film surface is analyzed and researched by experiment based on the aerosol theory. In this project, the electric and thermal fields on the hot-film surface are considered differing from aerosol research in the field of the air-conditioning ventilation system and respiratory tract. The transport process in the flow channel and deposition velocity on the hot-film surface is analyzed by building the movement and force model of particle, and the main factors effecting on deposition velocity are researched. Based on the research above, the deposition quantity, thickness and distribution of particles on the hot-film surface are analyzed by simulation and experiment. The effect of roughness change caused by particle deposition on deposition velocity is also analyzed. Accuracy variation of the contaminated sensor is researched, and the relation model between contamination and measurement accuracy is build in order to forecast the accuracy variation tendency. The cyclone-type small particle segregation device is designed which can be integrated into hot-film air flow sensor. Its structure parameters are analyzed and optimized by the finite element model, and the dust collection efficiency is analyzed by experiment. The research of this project can provide the reference for sensor design, and have important significance for improving the anti-contamination ability and accuracy stability and broadening its application field.

针对热膜式气体流量传感器受污染后测量精度下降的问题，基于气溶胶理论对灰尘、油雾等微小颗粒物在热膜表面的沉积机理进行分析和试验研究。与气溶胶在空调通风、呼吸系统等领域的应用研究不同，本项目考虑传感器热膜表面形成的热场和电场，通过建立颗粒物的运动和受力模型，分析颗粒物在流道内的输运过程和热膜表面的沉积速度，研究影响沉积速度的主要因素。在此基础上，利用仿真和试验分析颗粒物在热膜表面的沉积数量、厚度和分布的变化规律以及由颗粒物沉积引起的粗糙度变化对沉积速度的影响，研究传感器受污染后精度的变化，建立沉积污染物与测量精度之间的关系模型，预测传感器精度的变化趋势。为减少颗粒物在热膜表面的沉积，基于气旋原理设计集成于传感器的小型颗粒物分离装置，利用有限元模型对结构参数进行设计优化，并通过试验分析其除尘效率。该研究可为传感器的设计改进提供参考，对于提高抗污染能力和精度的保持性，拓宽其应用领域具有重要意义。

针对热膜式气体流量传感器受污染后测量精度下降的问题，对微小颗粒物在热膜表面的沉积机理进行了分析和试验研究。首先，建立了颗粒物沉积试验系统，使颗粒物在传感器热膜表面自然沉积，通过测量堆积物的三维形貌，得到了随着沉积时间增加，颗粒物在热膜表面的沉积量、沉积厚度、分布区域的变化规律。结合气溶胶理论分析颗粒物在传感器中的输运过程和受力吸附过程，研究温度场和电场对于颗粒物沉积的影响规律，建立颗粒累积厚度随时间变化的理论模型，分析产生颗粒吸附污染的主要因素。通过建立流量传感器的理论模型和污染物的有限元模型，分析了污染物对传感器的温度场、流场以及测量精度的影响，通过自然沉积和微喷的方法进行实验验证。通过研究传感器受污染后精度的变化，建立沉积污染物与测量精度之间的关系模型，并分析了湿度和油雾浓度对于传感器测量精度的影响规律。为减少颗粒物在热膜表面的沉积，基于气旋原理设计集成于传感器的小型颗粒物分离装置，利用有限元模型对结构参数进行设计优化，通过仿真和实验研究了在不同工作条件下气旋除尘装置的支路流量比例、压力损失和除尘效率等性能。该研究可为传感器的设计改进提供参考，对于提高抗污染能力和精度的保持性，拓宽其应用领域具有重要意义。