基于TDLAS直接检测法的柴油机NOx排放在线测试

NO_x是柴油机排放污染物中对生态环境危害最为严重的组分。随着全球环境污染问题的日益严重，柴油机NO_x排放问题受到了广泛的关注。各种排放法规相继出台，一方面对柴油机NO_x排放量提出新的要求，另一方面对测试方法也提出了更高的要求。现有测试方法多为采样分析法，采样周期较长，无法实现污染物排放的实时在线测量，柴油机污染物排放的实时在线测量不仅有利于监管，同时可为优化柴油机的燃烧过程、优化控制策略提供数据支持。光学检测技术作为一种新型的检测方法，其中的可调谐半导体激光吸收光谱技术(TDLAS)因其实验原理简单、响应速度快，在其他领域得到了广泛使用。为验证该方法在柴油机NO_x排放检测中的可行性，实验小组开展基于TDLAS的柴油机NO_x排放实时在线测量研究，针对NO_x的主要成分，利用调谐波长为5 262~5 265和6 138~6 142 nm的带间级联激光器(interband cascade lasers, ICL)分别作为检测NO、NO₂的探测光源，Thorlabs PDA10JT型热式探测器用来对信号光进行采集。采用直接探测方式在D4114B型柴油机上开展实验研究，并将测试结果与AVL排放分析仪进行对比，其测量偏差小于5%，另外，实验小组利用TDLAS技术的高时间分辨率，对柴油机的变工况过程进行NO_x瞬态排放测量，得到合理的NO_x排放变化结果。因此，采用TDLAS技术对研究柴油机瞬态排放特性具有重要的意义。

Research on the Online Test of Diesel NOx Emission by TDLAS

NO_x is the most harmful component for ecological environment in diesel engine emission. As global environmental problem becomes increasingly serious, the NO_x emission of diesel engine has been concerned widely. With a variety of emission regulations legalized, this not only presents new demands for NO_x emissions of diesel engine but also puts forward higher requirements for test method. Feasible test methods usually are the methods of sampling and analysis, which need a long sampling time and can’t achieve online measure of emission. The online measure of diesel engine emission is not only to the benefit of supervising but also provides data support for optimizing combustion process and optimizing control strategy for diesel engine. Optical detection technique serves as a new detection method. As one of it, the tunable diode laser absorption spectroscopy has been widely applied in other areas because of simple experimental principle and fast response speed. In order to verify the feasibility of this method in diesel engine NO_x emissions testing, experimental team researched on the online test of diesel NO_x emission by TDLAS. Aiming at the main component of NO_x, two interband cascade lasers whose tunable wavelengths were 5 262~5 265 and 6 136~6 142 nm were selected as detecting light source for respectively testing NO and NO₂. Thorlabs PDA10JT type thermal detectors were chosen for collecting optical signal. The diesel engine of D4114B by the direct detection was researched and the test result with the result of AVL emission analyzer was compared. The measure error is less than 5％. In addition, experimental team conducted NO_x transient emission measurement of a diesel variable conditions with the high time resolution of TDLAS and obtained a reasonable changed consequence of NO_x emissions. Thus, appling TDLAS technique has important significance for transient emission characteristics of diesel engine.