Abstract Since fuel reactivity stratification greatly influences the combustion process of dual-fuel engines and nozzle geometry directly affects the distribution of direct injected fuel, experiments were carried out to investigate the effects of nozzle-hole number on the combustion and emissions of dual-fuel engine. The experiments were performed on a single-cylinder diesel engine with port injection of ethanol and direct injection of diesel. There are four diesel injectors with 4, 5, 6 and 8 nozzle holes studied in this paper, while the total orifice areas and included spray angles of the injectors are kept the same. With reduced nozzle holes, the experimental results showed that both the in-cylinder peak pressure and PPRR (peak pressure rise rate) of ethanol/diesel dual-fuel combustion were decreased while with extended combustion durations. This is mainly because the number of high fuel reactivity regions was reduced with fewer diesel sprays, then the combustion of premixed ethanol was slowed down which consequently decreased the heat release rate. With reduced nozzle holes, the engine-out NOx emissions were decreased, and soot emissions were slightly increased while still maintained at quite low level. The UHC and CO emissions were slightly increased with reduced nozzle holes which resulted in lower combustion efficiency. However, the influences of nozzle-hole number on dual-fuel combustion were gradually decreased with advanced injection, which was mainly because of the enhanced diesel/air mixing. The experimental results indicated that dual-fuel combustion with reduced nozzle holes could achieve moderate heat release with lower PPRR.

中文翻译：

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喷孔数对乙醇/柴油双燃料发动机燃烧及排放特性影响的试验研究

摘要 由于燃料反应分层对双燃料发动机的燃烧过程有很大影响，喷嘴几何形状直接影响直喷燃料的分布，通过实验研究了喷嘴孔数对双燃料发动机燃烧和排放的影响。 . 实验在单缸柴油发动机上进行，采用进气口喷射乙醇和直接喷射柴油。本文研究了四个喷孔为4、5、6和8的柴油喷油器，而喷油器的总孔口面积和喷雾夹角保持不变。实验结果表明，随着喷嘴孔的减少，乙醇/柴油双燃料燃烧的缸内峰值压力和PPRR（峰值压力上升率）均降低，而燃烧持续时间延长。这主要是因为随着柴油喷射次数的减少，高燃料反应区的数量减少了，然后预混乙醇的燃烧速度减慢，从而降低了放热率。通过减少喷孔，发动机排出的氮氧化物排放量减少，烟尘排放量略有增加，但仍保持在较低水平。UHC 和 CO 排放量随着喷嘴孔的减少而略有增加，从而导致燃烧效率降低。然而，喷孔数量对双燃料燃烧的影响随着提前喷射逐渐减小，这主要是由于柴油/空气混合的增强。实验结果表明，减少喷嘴孔的双燃料燃烧可以在较低的 PPRR 下实现适度的放热。