Research On Key Techniques For Detecting High Temperature CO,CO₂ Emission Factors Of Motor Vehicle Exhaust

CO and CO2 emissions from the vehicle exhaust are one of the major mobile sources of the urban air pollution.At present,the state has issued relevant policies and regulations to strengthen the supervision of the exhaust CO and CO2 emissions.Vehicle-mounted equipment that detects CO and CO2 emission factors in China mainly depends on imports.In this paper,the key technologies for the detection system of the CO and CO2 emission factors of the vehicle exhaust has been researched to provide the technical support for the localization testing equipment for the CO and CO2 emission factors.Aimed at the sampling and pretreatment demand for the vehicle exhaust of high temperature,the key components such as the portable small cyclone separator for water-removal,the improved pitot tube for the tail pressure differential measurement,the multi-point temperature measuring module,and the improved orifice plate for the sample gas pressure measuring have all been developed.Then the gas sampling and pretreatment circuit has been designed and the pretreatment system for the high-temperature has been integrated and the purpose of removing particulate matter and moisture from the exhaust has been achieved.The corresponding parameters such as the temperature and mass flow of the CO and CO2 emission factors have been obtained from the vehicle exhaust of high temperature.The experimental results show that after the pretreatment relative humidity of the sample gas is less than 40%,its temperature is less than 50?,its particle diameter is less than 3 ?m,also with a very low content,all of which can meet the requirements of the optical detection and analysis module.The gas circuit switching and driving module for the zero,scalar and sample gas of the detection system was designed.The detection circuit to detect temperature,humidity,and pressure parameters of sample gas were developed.In the infrared absorption signal detection circuit,an adaptive wide-range signal detection circuit and a single-frequency filter circuit based on DSP and a modified dual-sampling circuit for modulating the photoelectric signal were developed.Fast,wide-range,low-noise detection of the infrared measurement signals is achieved.The comparison experiments show that the response time of the high-temperature exhaust CO and CO2 concentration detection system is 0.5s,a six-fold increase in response speed over traditional methods.The effect of temperature,humidity,and pressure on the concentration of CO and CO2 measured after pre-treatment was analyzed,an on-line correction algorithm for CO and CO2 concentration detection based on neural networks has been proposed,the inversion accuracy of CO and C02 concentrations in high temperature tail gas is improved.Standard sample experiments show that the maximum relative deviation has decreased from 22%to 5.8%.Simulation comparison experiments show that the maximum relative deviation has decreased from 15%to 4.8%.Vehicle experiments show that the correction factor is between 0.8 and 1.The above results verify the effectiveness of the algorithm in the CO and CO2 concentration correction.The external field application experiment of the detection system has been carried out.The CO and CO2 emission factors of the light gasoline vehicle and the diesel one have been measured respectively.And compared with the SEMTECH-CO/CO2 detector of Sensors,the experimental results showed that the correlation degree of the CO emission factor has reached 0.931,while that of the CO2 emission factor has reached 0.925.