Research On Automobile Co Emissions Quantity Measurement Technique Using Qepas

Rapid growth of the automotive and universal application has brought convenience to people’s lives and production, but at the same time its emissions are causing serious pollution to the survival of our environment. In order to monitor and prevent vehicle emissions of pollutants, it must first do emissions testing to strictly prohibit substandard vehicles traveling. Our country started from 1981 in accordance with the national conditions of China’s industrial level to develop appropriate emission regulations, with increasing levels of industry, the emissions regulations increasingly toughen, harmful emissions increasingly demanding lower limits. Therefore, the detection techniques and methods which have advantage include of efficient, reliable detection, limit smaller and higher accuracy was needed.The quartz enhanced photoacoustic spectroscopy (QEPAS) has high sensitivity, Strong outside interference immunity, fast response, low detection limit, large dynamic range and response has nothing to do with the incident light wavelength, which are advantages in the gas detection. It provides new ideas and methods in automotive emissions testing when QEPAS is used in automobile CO emissions detection.In this paper, based on the gas molecules absorb infrared theory, automobile CO emissions to be measured, looked for absorption lines that ware no cross-interference with other gases absorption peak. The quartz tuning fork and quartz enhanced photoacoustic spectroscopy theory were analysed, and the wavelength modulation and harmonic detection method were applied QEPAS to increase signal to noise ratio and accuracy. Using the Matlab software to simulate QEPAS detected automobile CO emission quantity, which was the theoretical foundation for the examination.Designed and built a QEPAS automobile CO emissions testing system based on quartz enhanced photoacoustic spectroscopy theory analysis. The tunable DFB laser and focus collimated optical path was slected as the optical path. The quartz tuning fork and resonance tube was slected as gas path. The preamplifier, electronic control unit and computer assembled system circuit part.The laser performance of QEPAS automobile CO emissions testing system which connect wavelength and power with temperature and current were tested, and the modulation parameters were selected. QEPAS automobile CO emissions testing system was calibrated by wavelength modulation method. its performance that included detection limit, reproducibility and stability were tested. Combined with National Standard GB 18285-2005 40’Limits and measurement methods for exhaust pollutants from vehicles equipped ignition engine under two-speed idle conditions and simple driving mode conditions’to test automobile CO emissions quantity, the tested results and the exhaust gas analyzer measurement results were compared.