基于计算流体动力学的光声流量传感器设计与实验验证
Designing and experimental verification of a photoacoustic flow sensor using computational fluid dynamics
摘要：
演示了一种用于快速实时气体传感的光声（PA）传感器。PA传感器是由现场可编程门阵列（FPGA）控制的独立系统。使用计算流体动力学（CFD）分析设计PA单元，用于流噪声免疫。CFD分析的目的是研究并尽量减少气体分布和流动噪声对PA信号的影响。用自制的中红外带间级联激光器（ICL）在2950 cm $^{-1}$（3.38 $μ$ m）处激发清洁空气中己烷（C $_6$ H $_{14}$）和癸烷（C $_{10}$ H $_{22}$）分子的C-H伸缩振动带，在不同流速下进行PA测量。我们观察到（1 $σ$，标准偏差）的灵敏度为0.4 $\pm0.1$ ppb（nmol/mol）的己烷在清洁空气中的流速高达1.7 L/min，对应于归一化噪声等效吸收（NNEA）系数为2.5 $\times 10^{-9}$ W cm $^{-1}$ Hz $^{-1/2}$，表明高灵敏度和快速实时气体分析。癸烷的Allan偏差分析表明，在最佳积分时间的检测限为0.25 ppbV（nmol/mol）。
英文摘要：
A photoacoustic (PA) sensor for fast and real-time gas sensing is demonstrated. The PA sensor is a standalone system controlled by a Field-Programmable Gate Array (FPGA). The PA cell has been designed for flow noise immunity using computational fluid dynamics (CFD) analysis. The aim of the CFD analysis was to investigate and minimize the influence of the gas distribution and the flow noise on the PA signal. PA measurements were conducted at different flow rates by exciting molecular C-H stretch vibrational bands of hexane (C$_6$H$_{14}$) and decane (C$_{10}$H$_{22}$) molecules in clean air at 2950 cm$^{-1}$ (3.38 $μ$m) with a custom made mid-infrared interband cascade laser (ICL). We observe a (1$σ$, standard deviation) sensitivity of 0.4 $\pm0.1$ ppb (nmol/mol) for hexane in clean air at flow rates up to 1.7 L/min, corresponding to a normalized noise equivalent absorption (NNEA) coefficient of 2.5$\times 10^{-9}$ W cm$^{-1}$ Hz$^{-1/2}$, demonstrating high sensitivity and fast real-time gas analysis. An Allan deviation analysis for decane shows that the detection limit at optimum integration time is 0.25 ppbV (nmol/mol).
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