Post injection has significant benefit in the reduction of diesel soot emissions. Therefore, there is a need to understand the effect of post-injection strategy on soot physicochemical properties and reactivity because they play an important role in soot oxidation process that governs the final soot emissions. This work focuses on the impact of post injection on the physicochemical properties and reactivity of diesel in-cylinder soot using a main plus post injection (M*P) and a single injection (M) strategy. The soot was sampled by a developed total cylinder sampling system, and the dividing points of soot formation-dominant and oxidation-dominant phases were used for studying the impacts of post injection on the characteristics of in-cylinder soot. The physicochemical properties of the soot samples, including primary particle size, nanostructure, carbon chemical state and surface functional groups, were characterized. The soot reactivity was evaluated in terms of peak temperature, burnout temperature and apparent activation energy. In the oxidation-dominant phase, the M*P soot initially possesses smaller primary particle size, shorter fringe length, larger tortuosity, lower sp²/sp³ hybridization ratio of carbon atoms and higher content of aliphatic CH groups than the M soot. The beneficial influence of physicochemical properties on soot reactivity when using post injection is validated by the thermogravimetric data, which shows that the M*P soot is more reactive than the M soot at the onset of the oxidation-dominant phase. In the M*P case, the soot generated from the main-injection combustion has lower reactivity than the soot from the post-injection combustion after they experience the soot formation-dominant phase. The results indicate that the use of post injection leads to in-cylinder soot with physicochemical properties that favor reactivity. The enhancement of reactivity means that the soot will be more readily oxidized in the subsequent combustion process, and consequently contributes to a reduction in final soot emissions.

后喷射在减少柴油机烟尘排放方面具有显着优势。因此，有必要了解后喷射策略对烟灰理化性质和反应性的影响，因为它们在控制最终烟灰排放的烟灰氧化过程中起着重要作用。这项工作着眼于采用主加后注入（M * P）和单次注入（M）策略对后喷射对柴油机缸内烟灰的理化性质和反应性的影响。通过发达的总气瓶采样系统对烟灰进行采样，并以烟尘形成为主相和氧化为主相的划分点来研究后喷射对缸内烟灰特性的影响。烟尘样品的物理化学特性，包括初级粒径，纳米结构，表征了碳的化学状态和表面官能团。根据峰值温度，燃尽温度和表观活化能评估烟灰反应性。在氧化为主相中，M * P烟灰最初具有较小的初级粒径，较短的条纹长度，较大的曲折度，较低的sp碳原子的² / sp ³杂化比和脂肪族C的含量较高H组比M炭黑。通过热重数据验证了使用后注射时物理化学性质对烟so反应性的有益影响，这表明在氧化主导相开始时，M * P烟ot比M烟ot更具反应性。在M * P情况下，主喷射燃烧产生的烟灰在经历烟灰形成为主相后，其反应性比后喷射燃烧产生的烟灰低。结果表明，后喷射的使用会产生具有有利于反应性的理化性质的缸内烟灰。反应性的提高意味着烟灰将在随后的燃烧过程中更容易被氧化，因此有助于减少最终的烟灰排放。