Internal combustion engines working at cold conditions lead to the production of excessive pollutant emissions levels. The use of the exhaust gas recirculation could be necessary to reduce the nitrogen oxides emissions, even at these conditions. This paper evaluates the impact of using the high-pressure exhaust gas recirculation strategy while the diesel particulate filter is under active regeneration mode on a Euro 6 turbocharged diesel engine running at low ambient temperature (−7°C). This strategy is evaluated under 40 h of operation, 20 of them using the two systems in combination. The results show that the activation of the high-pressure exhaust gas recirculation during the particulate filter regeneration process leads to a 50% nitrogen oxides emissions reduction with respect to a reference case without exhaust gas recirculation. Moreover, the modification of some engine parameters compared to the base calibration, as the exhaust gas recirculation rate, the main fuel injection timing and the post injection quantity, allows to optimize this strategy by reducing the carbon monoxide emissions up to 60%. Regarding the hydrocarbons emissions and fuel consumption, a small advantage could be observed using this strategy. However, the activation of the high-pressure exhaust gas recirculation at low temperatures can produce fouling deposits and condensation on the engine components (valve, cooler, intake manifold, etc.) and can contribute to reach saturation conditions on the particulate filter. For these reasons, the regeneration efficiency is followed during the experiments through the filter status, concluding that the use of low high-pressure exhaust gas recirculation rates in combination with the regeneration mode also allows to clean the soot particles of the particulate filter. These soot depositions are visualized and presented at the end of this work with a brief analysis of the soot characteristics and a quantitative estimation of the total soot volume produced during the experimental campaign.

在寒冷条件下工作的内燃机导致产生过量的污染物排放水平。即使在这些条件下，也可能需要使用废气再循环以减少氮氧化物的排放。本文评估了在柴油机微粒滤清器处于主动再生模式下时使用高压废气再循环策略对在低环境温度（−7°C）下运行的Euro 6涡轮增压柴油机的影响。该策略是在运行40小时后进行评估的，其中两个系统组合使用了其中的20个。结果表明，相对于没有废气再循环的参考情况，在微粒过滤器再生过程中高压废气再循环的激活导致氮氧化物排放减少了50％。而且，与基本校准相比，对某些发动机参数的修改，例如排气再循环率，主燃料喷射正时和后喷射量，可以通过减少高达60％的一氧化碳排放来优化此策略。关于碳氢化合物的排放和燃料消耗，使用这种策略可以观察到很小的优势。但是，低温下高压排气再循环的激活会在发动机部件（气门，冷却器，进气歧管等）上产生结垢和冷凝，并有助于达到颗粒过滤器的饱和状态。由于这些原因，实验过程中通过过滤器状态来跟踪再生效率，结论是，将低压废气再循环率低与再生模式结合使用还可以清洁微粒过滤器的烟灰颗粒。在工作结束时，这些烟灰沉积物将被可视化并呈现出来，其中简要分析了烟灰特性，并对实验过程中产生的烟灰总量进行了定量估算。