The main objective of this experimental-observational study is to investigate the microexplosion phenomenon of small methanol-in-diesel emulsion droplets (50 to 150 μm) under realistic enginelike conditions of high temperature and pressure. The microemulsion was prepared mixing 59 wt % diesel and 25 wt % methanol with 16 wt % 1-dodecanol as the surfactant, whereas the macroemulsion was prepared with 87.6 wt % diesel, 10 wt % methanol, and 2.4 wt % mixture of two surfactants. The emulsion droplets were generated using a nozzle with a size of 230 μm and injected into a high-pressure chamber. The chamber is optically accessible and filled with nitrogen at a pressure of 50 bar and a temperature of 900 K. In this current observation, emulsion droplets in the size range of 50 to 150 μm in a high-pressure, high-temperature environment did not exhibit the phenomenon of microexplosion even up to 11 ms, which is close to the timescales of relevance in practical diesel engines. This is attributed to the small timescale of droplet evaporation, which is not sufficient for coalescence of the dispersed droplets inside an emulsion droplet to occur. As coalescence is a precursor for the microexplosion, the droplet tends to evaporate before undergoing microexplosion. In addition, a strong convective environment may create internal circulation inside the emulsion droplets, further restricting coalescence of the dispersed droplets.

中文翻译：

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类似发动机工况下柴油机内甲醇乳液液滴微爆现象的评估

这项实验-观察研究的主要目的是研究在高温高压的现实发动机条件下柴油中小甲醇乳液液滴（50 至 150 μm）的微爆炸现象。将 59 wt% 柴油和 25 wt% 甲醇与 16 wt% 1-十二烷醇作为表面活性剂混合制备微乳液，而用 87.6 wt% 柴油、10 wt% 甲醇和 2.4 wt% 两种表面活性剂的混合物制备粗乳液。使用尺寸为 230 μ m 的喷嘴产生乳液液滴并注入高压室。在 50 bar 的压力和 900 K 的温度下，该腔室可光学进入并充满氮气。在目前的观察中，尺寸范围为 50 至 150 的乳液液滴μm在高压、高温环境下即使达到11 ms也没有表现出微爆现象，这接近于实际柴油机的相关时间尺度。这归因于液滴蒸发的小时间尺度，这不足以使分散液滴在乳液液滴内发生聚结。由于聚结是微爆炸的前兆，液滴在经历微爆炸之前往往会蒸发。此外，强对流环境可能会在乳液液滴内部产生内部循环，进一步限制分散液滴的聚结。