Ducted fuel injection (DFI) is a newly established technology showing great potential in breaking the soot/NOx trade-off. Multiple-injection strategy is also seen as a possible way to reduce soot and NOx emissions simultaneously. However, the applicability of these approaches is not fully understood. The present study investigated the spray characteristics of DFI technology coupled with a dual-injection strategy. Results showed that during the injection interval (the interval between two injections), ambient gas continues to flow into the duct due to the pressure difference between the duct inside and outside, which increases the velocity of the second injection. The spray penetration length development of ducted spray is faster than that of free spray in both the first and the second injection events. During the first injection, the distribution of the equivalence ratio of ducted spray is more uniform than free spray, and the peak value of the equivalence ratio of ducted spray is lower than that of free spray. Compared to the first injection, in the second injection, when the radial equivalence ratio distribution of ducted spray is equivalent to the that of free injection, the path of spray traversed is shorter. These indicate that DFI technology and dual injection strategy couples well in case of spray and mixing process.

中文翻译：

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双喷射策略管道喷雾的实验和数值研究

管道燃油喷射 (DFI) 是一项新建立的技术，在打破烟尘/氮氧化物平衡方面显示出巨大潜力。多次喷射策略也被视为同时减少烟灰和氮氧化物排放的可能方法。然而，这些方法的适用性还没有被完全理解。本研究调查了 DFI 技术与双喷射策略相结合的喷雾特性。结果表明，在喷射间隔期间（两次喷射之间的间隔），由于管道内外压力差，环境气体继续流入管道，这增加了第二次喷射的速度。在第一次和第二次喷射事件中，管道喷雾的喷雾渗透长度发展都比自由喷雾快。在第一次注射时，管道喷雾的当量比分布比自由喷雾更均匀，管道喷雾的当量比峰值低于自由喷雾。与第一次喷射相比，第二次喷射中，当管道喷雾的径向当量比分布与自由喷射相当时，喷雾横越的路径更短。这些表明 DFI 技术和双喷射策略在喷雾和混合过程中耦合良好。喷雾经过的路径较短。这些表明 DFI 技术和双喷射策略在喷雾和混合过程中耦合良好。喷雾经过的路径较短。这些表明 DFI 技术和双喷射策略在喷雾和混合过程中耦合良好。