基于光声光谱原理的气体浓度检测是光声技术最典型的应用。 与其他光谱气体检测方法相比, 光声气体检测技术主要具有结构简单、 探测器不受波长限制、 零背景噪声、 成本低等优点。 它在气体检测领域得到了广泛的认可和应用。 作为光声光谱气体检测系统的核心部件, 光声池的性能将直接影响系统的检测结果。 因此, 光声池的优化设计已成为该领域的研究热点。 当前, 针对光声池的优化主要是基于系统静态条件, 关于光声池腔内气体流动性能及动态时间响应的研究报道较少。 由于光声池在动态检测条件下的气体扰动及系统检测噪声具有一定影响, 因而对于光声池的相关参数进行进一步的探索与优化, 改善光声池腔内气体流场分布、 动压特性及其气体浓度平衡时间对于提升光声光谱的气体检测性能具有重要意义。 为此, 以传统的圆柱形光声池为基础, 基于三维流场数值模拟方法建立了光声池腔内流场的稳态和瞬态模拟模型, 计算获得了光声池腔内气体流场分布及其气体浓度平衡响应规律, 结果表明, 减少光声池腔内气流流速及优化光声池中的过渡结构将会改善气流引发的动压波动以及缩短腔内气体浓度调节时间。 以光声池的缓冲腔与谐振腔过渡处圆角、 辅助孔数量、 辅助孔半径、 辅助孔中心圆半径以及进气速度5个参数为因素, 以谐振腔轴线中点处动压值和气体浓度调节时间为考察指标, 采用数值模拟和正交试验设计与熵权法相结合的方法, 获得了光声池的相关参数对动压值影响的主次影响顺序为: 辅助孔半径>辅助孔数>进气速度>过渡圆角>辅助孔中心圆半径; 对调节时间影响的主次顺序依次为: 进气速度>辅助孔半径>辅助孔数=辅助孔中心圆半径>过渡圆角, 为平衡指标的影响, 将多目标参数优化问题转化成单目标优化问题, 客观地给出动压值和调节时间的权重分别为0.49、 0.51。 在研究参数范围内, 获得了其最佳参数组合为: 缓冲腔与谐振腔过渡处圆角为3.0 mm、 辅助孔数量为8个、 辅助孔半径为3.5 mm、 辅助孔中心圆半径为22.5 mm、 进气速度为0.06 m·s-1, 优化后的光声池谐振腔轴线中点处动压值为9.4×10-4 Pa, 腔内气体浓度调节时间为141 s, 相较于优化前的指标, 动压值相对降低了88.1%, 调节时间相对降低了17.5%, 两项指标均得到优化提升, 优化效果较为理想。 研究方法与结论可为光声池的优化设计和拓展研究提供重要参考。

Photoacoustic spectroscopy gas detection technology is the most typical application of photoacoustic technology. Compared with other methods, photoacoustic gas detection technology has the advantages of a simple structure, wavelength free detector, zero background noise and low cost. This technology has been widely used in various fields. The photoacoustic cell is the core component of the photoacoustic spectrum gas detection system, and its performance greatly impacts the detection results. At present, the optimization of the photoacoustic cell is mainly carried out under static conditions, and there are few reports on the gas flow performance and dynamic time response in the photoacoustic cell cavity. Because the gas disturbance and system detection noise of the photoacoustic cell under dynamic detection conditions have a certain impact, the relevant parameters of the photoacoustic cell are further explored and optimized to improve the gas flow field distribution in the photoacoustic cell cavity. Dynamic pressure characteristics and gas concentration equilibrium time are of great significance to improve the gas detection performance of photoacoustic spectroscopy. Therefore, based on the traditional cylindrical photoacoustic cell, the steady-state and transient simulation models of the flow field in the photoacoustic cell cavity are established based on the three-dimensional flow field numerical simulation method, and the gas flow field distribution and gas concentration balance response law in the photoacoustic cell cavity are calculated. The results show that reducing the flow velocity in the photoacoustic cell and optimizing the transition structure in the photoacoustic cell will improve the dynamic pressure fluctuation caused by the flow and shorten the gas concentration regulation time in the cavity. Taking the five parameters of the transition corner between the buffer cavity and the resonator of the photoacoustic cell, the number of auxiliary holes, the radius of the auxiliary hole, the radius of the center circle of the auxiliary hole and the air inlet speed as factors, and taking the dynamic pressure value at the midpoint of the resonator axis and the gas concentration adjustment time as inspection indexes, the method of combining numerical simulation, orthogonal experimental design and entropy weight method is adopted, The primary and secondary order of the influence of the relevant parameters of the photoacoustic cell on the dynamic pressure value is obtained as follows: the radius of the auxiliary hole>the number of auxiliary holes>air inlet speed>transition fillet>the radius of the center circle of the auxiliary hole; The primary and secondary order of influence on the adjustment time is: inlet speed>auxiliary hole radius>number of auxiliary holes=auxiliary hole center circle radius>transition fillet. In order to balance the influence of indicators, this paper transforms the multi-objective parameter optimization problem into a single objective optimization problem. It objectively gives the weight of dynamic pressure value as 0.49 and the weight of adjustment time as 0.51 respectively. Within the range of parameters studied in this paper, the best combination of parameters is obtained: the circle at the transition between the buffer cavity and the resonator is 3.0 mm, the number of auxiliary holes is 8, the radius of auxiliary holes is 3.5 mm, the radius of the center circle of auxiliary holes is 22.5mm, the air inlet speed is 0.06 m·s-1, the dynamic pressure value at the midpoint of the axis of the optimized photoacoustic cell resonator is 9.4×10-4 Pa, and the gas concentration adjustment time in the cavity is 141 s. Compared with the indicators before the optimization of the photoacoustic cell, the dynamic pressure value is relatively reduced by 88.1%, and the adjustment time is relatively reduced by 17.5%. Both indicators have been optimized and improved, and the optimization effect is relatively ideal. The research methods and conclusions can provide important references for photoacoustic cell optimization design and expansion.