Vehicle-Mounted Suitability Study Of Atmospheric Quality Monitoring Equipment

In recent years,with the development of modernization,the greenhouse gas emissions in the atmospheric have become a very important problem which affects our climate and environment.Among them,methane(CH4),as the second largest greenhouse gas,not only causes greenhouse effect,but also affects the abundance of other greenhouse gases,thus aggravating the global warming trend.Therefore,to achieve carbon peaking and carbon neutrality goals and mitigate the trend of global warming,it is necessary to strengthen the monitoring of methane concentration.Vehicle gas monitoring technology has been widely concerned because of its wide monitoring range and high precision.Infrared Absorption Spectroscopy is commonly used to monitor trace gases such as methane.Tunable Diode Laser Absorption Spectroscopy(TDLAS)has become one of the effective methods for monitoring trace gases,with high precision,sensitivity and selectivity.To ensure the high precision detection of monitoring equipment in the on-board application,this thesis simulates the actual monitoring environment of on-board equipment through experiments based on TDLAS technology,analyzes the main factors affecting the concentration detection accuracy,and carries out research on the compensation algorithm for the influence of temperature and pressure on the gas monitoring system.TDLAS technology principle and temperature and pressure model simulation are introduced.First,the basic principles of TDLAS technology are introduced and analyzed.Second,theoretical simulation was carried out by MathCAD software based on HITRAN(High resolution Transmission Molecular Absorption Database)to study the effects of temperature and pressure on laser absorption spectrum measurement.Finally,a laser absorption spectrum measurement system based on tunable diode is constructed by using the laser control circuit and gas absorption cell made in the laboratory.The problem of temperature interference is analyzed and the temperature compensation algorithm is researched.Aiming at the problems such as the variation of temperature in four seasons and diurnal temperature during vehicle operation,this thesis studies the influence of temperature variation on sample gas and laser absorption spectrum detector,and designs a temperature compensation algorithm based on empirical formula.First,by analyzing the variable temperature test data of the detection module,it is proposed to divide the influence factors of temperature into two parts,and study the influence of injection gas temperature and detector temperature respectively.Second,the temperature compensation is carried out by polynomial fitting concentration inversion results.Finally,according to the compensation effect,a scheme of treating the measured gas with 40℃ constant temperature treatment was proposed.After compensation,when the sample gas temperature changes from-40 to 70℃ the average error of system measurement is reduced from 8.4%to 1.08%,which effectively reduces the deviation of measurement value caused by temperature abrupt change,and achieves accurate measurement of methane at a wide temperature.The pressure interference problem of detection module is analyzed,and the pressure compensation algorithm is researched.In view of the pressure changes during long-term use of vehicle,a pressure compensation method based on empirical formula is proposed in this thesis to correct the gas concentration detection results.First,the influence of pressure abrupt change on gas concentration detection is studied and analyzed by experiment.Second,a pressure compensation algorithm is designed based on the concentration inversion results to correct the system.Finally,when the gas pressure changes from 995.3 kPa to 839.7 kPa after compensation,the average error of the system measurement decreases from 35.3%to 2.4%,effectively reducing the deviation of the measured value caused by the pressure mutation,and realizing the accurate measurement of methane in a wide range of pressure.In view of the above studies,this thesis demonstrates the strong correlation between concentration detection and temperature and pressure based on TDLAS technology.After the compensation of temperature and pressure algorithm,the accuracy and stability of the system are effectively improved,which realizes the accurate measurement of the detector in a wide range of temperature and pressure,and improves the scope of use of laser absorption spectroscopy detectors...