A Flexible Fibre Optic Borescope for Diagnosis of Active Controlled After-treatment and Engine Implementations

现代柴油机面临着满足日益严格的排放法规的诸多挑战。采用控制策略来减少尾气中氮氧化物(NOx)和颗粒物(PM)的排放。由于柴油机的整体稀薄运行，在排气流中添加了还原剂来中和NOx。在汽车行业通常采用的选择性催化还原(SCR)系统中，尿素被用作还原剂，而在贫氧NOx捕集系统中，燃料被定期添加。后一种系统与SCR系统相比具有整体成本低的优点，但在效率和投药控制方面存在缺点。减少PM还需要补充燃料来再生柴油微粒过滤器。排气在后处理系统中分布的均匀性对NOx转化效率有很大影响。此外，燃料分布的不均匀增加了热应力，对衬底造成了严重的破坏。在郑博士的团队中，已经对外部燃料补充的主动流动控制进行了广泛的实证研究。在主动后处理系统中，为了进行光学诊断，需要使用孔镜。通过光学诊断，可以确定喷射角和喷雾贯穿距离，并对其进行优化，以防止碰壁。利用红外成像技术，可以监测基片的热分布，有助于进一步优化给药策略。这对于气缸部件的安装和精确对准尤为必要，因为采用先进的新腔体设计的新活塞设计和新的喷油器安装要求在对准方面进行非常精确的匹配。轻微的不对准可能会对发动机部件造成损害。一个长的内窥镜探头来验证发动机内部件的正确匹配和没有干扰是非常关键的。随着我们目前的研究重点是在先进的内燃机中使用生物燃料，在硬件修改方面的需求更加强烈，以设计新的活塞几何形状并使新的喷油器适应我们的发动机平台。

Modern diesel engines are facing many challenges of meeting the increasingly stringent emission regulations. Control strategies are employed to reduce tail-pipe emissions of the nitrogen oxides (NOx) and particulate matter (PM). Due to the overall lean operation of diesel engine, supplemental reductant is used in the exhaust stream to neutralize NOx. In a selective catalytic reduction (SCR) system that commonly adopted by automotive industry to meet 2014 beyond emission standards, urea is dosed as the reductant, while in a lean NOx trap system, fuel is dosing periodically. The later system has the advantages over the SCR system for overall low cost but disadvantages in the efficiency and dosing control. PM reduction also requires supplemental fuel to regenerate the diesel particulate filter. The homogeneity of the exhaust fluid distribution in the after-treatment systems strongly impacts the NOx conversion efficiency. Moreover, the non-homogeneous fuel distribution increases the thermal stress and causes severe damage of the substrate. Extensive empirical investigations of active flow control with external fuel supplement have been carried out in Dr. Zheng's group. A borescope is needed for the purpose of optical diagnosis in the active aftertreatment system. Through optical diagnosis, the injection angle and the spray penetration can be characterized and then be optimized to prevent wall impingement. With infrared imaging technique, the thermal distribution of the substrate can be monitored, which can future help the optimization of the dosing strategies. This is particularly needed for cylinder component installation and precise alignment, since the new design of piston with advanced new chamber design and new injector installation require very precise matching in the alignment. A slight mis-alignment could be detrimental for the engine components. A long borescope probe to verify the correct mating and lack of interference of components within the engine is very critical. With our current research focus in using biofuels in advanced combustion engines, the need is intensified in hardware modifications to design new piston geometries and adapt new injectors to our engine platform.