NOx是柴油机排放的主要污染物质, 它对人体和环境的危害极大, 其中NO含量又占NOx总量的90％以上, 因此合理准确的检测柴油机排放物中NO的含量对NOx含量的检测尤为关键。 现有的测试方法由于采用采样分析法, 不能及时反映真实情况, 光学检测方法作为一种新型的测试技术, 在很多领域都有应用。 结合光学检测方法对稳态和瞬态过程下的NO浓度用TLAS技术开展研究, 通过模拟NO浓度的变化情况, 验证这种方法在柴油机上应用的可行性, 选择一台中心波长为5 263 nm的带间级联激光器用于检测, 为获得不同浓度的混合气体设计一套配气混合系统, 用高纯度的ＮＯ作为被测气体, N2作为背景气体, 配比不同浓度的测试样气, 在稳态测量时, 分别配比浓度为500, 1 000, 2 000 ppm的样气进行试验, 得到相对误差小于1%, 最大绝对误差为115 ppm。 在瞬态测量中, 分别对浓度增加与减少过程进行试验, 实时测量气室内的浓度变化情况, 在1 ms时间分辨率的情况下可实现52%的最大相对误差。 通过设计的系统, 可以实现NO浓度的瞬态测量, 能将此方法应用到柴油机上, 这种方法有利于研究柴油机的排放物含量。

NOx is the main pollutant substance of diesel engine. It is extremely harmful to human being and environment. NO content takes up more than 90 percent among NOx. Therefore, reasonable and accurate detection NO component of diesel engine emissions is particularly critical for the detection of NOx component. Current detection method can not reflect the real situation in time because of using sampling analysis. As a new testing technique, optical detection method has been applied in many fields. This paper combines the optical detection method to investigate TLAS technique for NO concentration under steady and transient process. By simulating the situation of NO concentration changes, the feasibility of this method to apply in the diesel engines verified. An inter-band cascade laser whose center wavelength is 5263 nm is chosen for detection. A gas compounding system is devised to obtain different concentration mixing gas. Matching the test sample gas of different concentrations with high purity NO as the measured gas is carried out with N2 as the background gas. In the steady measurement, respectively match the concentrations of 500, 1 000 and 2 000 ppm to conduct experiment. A relative error is less than 1%, and the maximum absolute error is 115 ppm. In the transient measurement, experiment is conducted respectively in the process with concentration increasing and decreasing. Besides the situation of the concentration change in the chamber is measured at real time. A maximum relative error of 52% is realized with a time resolution of 1ms. With the system we devised, a transient measurement of NO concentration can be realized. This method can be applied in the diesel engine, which is good for the study of the diesel engines emissions content.