The effect of split injection on mixture formation and combustion process was investigated in a rapid compression and expansion machine (RCEM). A two-dimensional (2D) piston cavity, which was designed as the cross section of a reentrant piston, was used to observe the in-cylinder information from the lateral side. The experiments were conducted at injection pressures of 80 MPa and 120 MPa. High-speed shadow method was applied to investigate the spray development, mixture formation, ignition location, and soot generation in the cylinder. The results showed that fresh oxygen and part of oxidized soot were involved in the burned pilot mixture with main spray injection, which was beneficial to reducing the soot particles. Furthermore, split injection accelerated the spray mixture development resulting from the air entrainment, and the longer interval led to more uniform mixture distribution, which was beneficial to improving the combustion process while suppressing the soot generation. This research provides a detailed investigation on diesel spray and combustion process and demonstrates that the impinging spray has a significant effect on the combustion process.

中文翻译：

---

分流喷射策略下柴油喷射和燃烧过程的实验研究；快速压缩膨胀机二维活塞腔侧面现象观察

在快速压缩和膨胀机 (RCEM) 中研究了分流喷射对混合物形成和燃烧过程的影响。二维 (2D) 活塞腔设计为凹形活塞的横截面，用于从侧面观察缸内信息。实验在 80 MPa 和 120 MPa 的注射压力下进行。应用高速阴影法研究汽缸内喷雾的发展、混合物的形成、点火位置和烟尘的产生。结果表明，主喷喷射燃烧后的中试混合物中含有新鲜氧气和部分氧化烟尘，有利于减少烟尘颗粒。此外，分流喷射加速了由夹带空气引起的喷雾混合物的发展，间隔越长，混合气分布越均匀，有利于在抑制烟尘生成的同时改善燃烧过程。本研究对柴油喷雾和燃烧过程进行了详细研究，并证明撞击喷雾对燃烧过程有显着影响。