Research On Rapid Response Detection Method And Key Technology Of Nitrogen Oxide

In this paper,according to the chemiluminescent reaction mechanism of NO and O₃,the NO analysis of motor vehicle exhaust is realized,and the photoelectric conversion technology of photodiode is used instead of the traditional photon counter.The traditional NOx gas detection process is re-optimized,which shortens the gas path and reduces the detection time,so that the time for the detection signal to reach the stable T₉₅is 3s,realizing real-time detection.Secondly,aiming at the problems of large divergence,strong randomness,low collection efficiency and long optical path of chemiluminescence,a new cylindrical total reflection S-shaped optical cavity structure for rapid detection of NO gas is designed.The optical software Zemax is used to simulate and analyze three optical path models:cylindrical wide-mouth scattering,lens focusing and cylindrical total reflection.The simulation results show that the cylindrical total reflection optical path has the best effect.In order to improve the mixing uniformity of nitric oxide and ozone in the cavity and the collection efficiency of photodiode detector,the structural model of S-shaped cavity composed of cylindrical totally reflective optical path is simulated by Fluent software.According to the comparison and analysis of cloud pictures of nitrogen dioxide,oxygen and ozone components,it shows that the collection efficiency of chemiluminescence by the collection optical path of S-shaped cavity is 47%,and the relative energy distribution of photons received by the optical path is 2.73.The gas reaction and mixing of S-shaped cavity model is more complete,and the stable error of reaction and mixing is 0.049,compared with the same period of last year.In order to realize the high sensitivity and low noise detection of fluorescent signals,p A-level photoelectric signal amplification circuit is designed,and a temperature control device with temperature control accuracy of 0.1℃is added to the gas chamber structure,which reduces the influence of temperature on the detection circuit and the chemical reaction of reactant gases,and provides guarantee for the detection of low concentration NO.At last,the influence parameters such as gas flow rate and reaction temperature are analyzed theoretically and verified experimentally.The experimental results show that the concentration of low concentration NO gas is linearly related to the luminous intensity,and the luminous intensity will increase obviously with the increase of gas flow rate,pressure and reaction temperature.In the range of 0-3067.48 mg/m³,the linearity of the system detection is 0.9993,the detection limit is 1.23 mg/m³,and the standard deviation is2.12.The system structure is simple,the response time is short,and it meets the new national testing standards.