Mechanisms of fuel injector tip wetting and tip drying based on experimental measurements of engine-out particulate emissions from gasoline direct-injection engines
Mechanisms of fuel injector tip wetting and tip drying based on experimental measurements of engine-out particulate emissions from gasoline direct-injection engines
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DOI：
10.1177/1468087420916052
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发表时间：
2020-05
影响因子：
2.5
通讯作者：
M. Medina;F. Alzahrani;M. Fatouraie;M. Wooldridge;V. Sick
中科院分区：
文献类型：
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作者：
M. Medina;F. Alzahrani;M. Fatouraie;M. Wooldridge;V. Sick
沉积在喷油嘴尖端的汽油燃料已被确定为在汽油直喷发动机的某些操作条件下的颗粒排放的重要来源。这项工作提出了简化的概念理解的机制，控制喷油器尖端润湿和尖端干燥的汽油直喷发动机。这项工作的目的是确定哪些物理机制的尖端润湿和干燥是最重要的操作条件和硬件考虑，并与机制的测量颗粒物数量的排放量。每个物理过程的趋势被评估为发动机运行条件的函数，例如发动机转速、喷射开始正时、发动机负载、燃料轨压力和冷却剂温度。还考虑了喷油器几何形状对喷嘴头润湿和干燥机制的影响。通过对喷嘴头部湿化机理的概念性理解，阐述了喷嘴头部湿化的几种机理，包括宽羽流湿化、涡滴湿化、燃料滴化湿化和燃料凝结湿化。所考虑的主要尖端干燥机制是单相蒸发。使用的概念理解，在这项工作中创建的尖端润湿和干燥机制，发动机运行条件和喷油器的几何形状的机制上的影响进行了比较与实验结果的颗粒数。结果表明，测量的颗粒数增加，通过增加喷射燃料质量。增加喷射燃料质量被怀疑通过宽羽流润湿和涡流液滴润湿机制来增加尖端润湿。还观察到颗粒数量随孔长度增加而增加。较长的孔长度被怀疑会导致通过涡滴和燃料滴流润湿机制的更高的尖端润湿。较长的时间尺度被发现减少颗粒物数量的排放。较低的速度和早期的喷射正时增加了时间尺度。同样，较高的冷却液温度降低颗粒数。冷却剂温度影响尖端温度，导致尖端干燥程度更高。
Gasoline fuel deposited on the fuel injector tip has been identified as a significant source of particulate emissions at some operating conditions of gasoline direct-injection engines. This work proposes simplified conceptual understanding for mechanisms controlling injector tip wetting and tip drying in gasoline direct-injection engines. The objective of the work was to identify which physical mechanisms of tip wetting and drying were most important for the operating conditions and hardware considered and to relate the mechanisms to measurements of particulate number emissions. Trends for each of the physical processes were evaluated as a function of engine operating conditions such as engine speed, start of injection timing, engine load, fuel rail pressure, and coolant temperature. The effects of fuel injector geometries on the tip wetting and drying mechanisms were also considered. Several mechanisms of injector tip wetting were represented with the conceptual understanding including wide plume wetting, vortex droplet wetting, fuel dribble wetting, and fuel condensation wetting. The main tip drying mechanism considered was single-phase evaporation. Using the conceptual understanding for tip wetting and drying mechanisms that were created in this work, the effects of engine operating conditions and fuel injector geometries on the mechanisms were compared with experimental results for particulate number. The results indicate that measured particulate number was increased by increasing injected fuel mass. Increasing injected fuel mass was suspected to increase tip wetting via wide plume wetting and vortex droplet wetting mechanisms. Particulate number was also observed to increase with hole length. Longer hole length was suspected to result in higher tip wetting via vortex droplet and fuel dribble wetting mechanisms. Longer timescale was found to decrease particulate number emissions. Lower speeds and early injection timings increased the timescale. Similarly, higher coolant temperature decreased particulate number. The coolant temperature influenced tip temperature resulting in higher tip drying.