基于紫外差分-自适应干扰对消的NO浓度高精度检测技术

High-precision detection technology of NO concentration based on UV differential-adaptive interference cancellation

为实现机动车尾气高精度监测,提出一种高精度宽量程NO测量方法。针对尾气中SO_(2)及NO在紫外波段存在吸收峰重合从而无法直接进行单组分气体反演问题,首先用紫外差分光学吸收光谱(ultra-violet differential optical absorption spectroscopy,UV-DOAS)法计算得到混合气体在NO敏感波段(200 nm~230 nm)的差分光学密度(differential optical density,DOD),并引入自适应干扰对消技术以实现混合气体DOD的快速分离,最终利用最小二乘法对分离出的NO进行浓度反演。该方法可实现100×10^(−6)~3000×10^(−6)范围内NO浓度(气体的体积分数)快速反演,经测试,在100×10^(−6)~200×10^(−6)浓度范围内反演相对误差绝对值小于10%,在300×10^(−6)~3000×10^(−6)浓度范围内,反演相对误差绝对值小于5%。该方法具有测量量程大、速度快的特点,可满足汽车尾气中3000×10^(−6)范围内NO浓度测量要求。

In order to realize high-precision monitoring of vehicle emission,a high-precision and wide-range NO measurement method was proposed.Aiming at the problem that the absorption peaks of SO_(2) and NO in emission overlapping in the UV band,and it was impossible to directly perform single-component gas inversion,the differential optical density(DOD)of mixed gas in the NO sensitive band(200 nm~230 nm)was first calculated by the ultraviolet differential optical absorption spectroscopy(UV-DOAS)method.Then,the adaptive interference cancellation technology was introduced to achieve rapid separation of mixed gas DOD.Finally,the least square method was used to perform the concentration inversion of separated NO.This method could achieve rapid inversion of NO concentration(volume fraction of gas)in the range of 100×10^(−6) to 3000×10^(−6).After testing,the absolute value of the relative error of inversion is less than 10%in the concentration range of 100×10^(−6) to 200×10^(−6),and less than 5%in the concentration range of 300×10^(−6) to 3000×10^(−6).This method has the characteristics of large measurement range and fast speed,and can meet the measurement requirements of NO concentration in the range of 3000×10^(−6) in vehicle emission.