Abstract Emissions of soot particles exert crucial impact on human health and the environment. Previous researches show that a partial replacement of fossil fuels with oxygenated fuels is supposed to reduce soot emission. However, the crucial information of soot size distributions is unclear, although small particles are more dangerous than large particles. In this paper, dimethyl ether (DME) is selected among the oxygenated fuels for the investigation of the doping effect on nascent soot formation. DME was doped in the burner-stabilized rich premixed ethylene/oxygen/argon flames at various mixing ratios. Flame temperature profiles were measured using R-type thermocouples with radiation correction. A scanning mobility particle sizer (SMPS) with a sampling system was used to determine particle size distributions (PSDs) of soot-containing combustion products with immediate dilution. Thermo-gravimetric analysis (TGA) complemented with elemental analysis (EA) was conducted to detect the chemical properties of formed soot particles. Additionally, species profiles of the experimental flame conditions were provided from simulations. The experimental PSDs showed that DME addition could slow down soot evolution process, while lead to a slight increase in incipient soot with size below 4 nm. When DME added, the production of benzene was suppressed due to the reduced concentrations of acetylene and propargyl, and thus soot nucleation. Meanwhile, soot oxidiation was enhanced because the OH radical and the oxidizability of soot particles are both increased. Considering the slight increase of sub-4 nm soot, the effect of oxygenated-PAHs (OPAH) was emphasized. The production of OPAH suppressed soot surface growth, which leading to the relatively lower consumption of sub-4 nm soot in DME added flames. As a result, DME cannot be simply regarded as a clean fuel due to the enhanced formation of sub-4 nm soot particles. When applying oxygenated fuels into practice, it is necessary to pay more attention to the size distributions of the emitted particles, and conduct appropriate post-processing techniques to reduce the emissions of small particles.

中文翻译：

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二甲醚在预混乙烯火焰中初期烟灰形成中的作用

摘要 烟尘颗粒的排放对人类健康和环境产生至关重要的影响。先前的研究表明，用含氧燃料部分替代化石燃料应该可以减少烟尘排放。然而，虽然小颗粒比大颗粒更危险，但烟尘粒度分布的关键信息尚不清楚。在本文中，二甲醚 (DME) 被选为含氧燃料，用于研究掺杂对新生烟尘形成的影响。DME 以各种混合比掺入燃烧器稳定的富预混合乙烯/氧气/氩火焰中。使用带有辐射校正的 R 型热电偶测量火焰温度曲线。带有采样系统的扫描迁移率粒度仪 (SMPS) 用于确定立即稀释的含烟灰燃烧产物的粒度分布 (PSD)。进行热重分析 (TGA) 和元素分析 (EA) 以检测形成的烟灰颗粒的化学性质。此外，实验火焰条件的物种分布由模拟提供。实验 PSD 表明，添加 DME 可以减慢烟尘演化过程，同时导致尺寸低于 4 nm 的初始烟尘略有增加。当加入 DME 时，由于乙炔和炔丙基的浓度降低，从而抑制了烟灰成核，苯的产生受到抑制。同时，由于 OH 自由基和烟尘颗粒的氧化性均增加，烟尘氧化得到增强。考虑到亚 4 nm 烟尘略有增加，强调了含氧多环芳烃 (OPAH) 的影响。OPAH 的产生抑制了烟灰表面的生长，从而导致在 DME 添加的火焰中亚 4 纳米烟灰的消耗相对较低。因此，由于亚 4 nm 烟尘颗粒的形成增强，DME 不能简单地被视为清洁燃料。在实际应用含氧燃料时，需要更加关注排放颗粒的尺寸分布，并采取适当的后处理技术，减少小颗粒的排放。OPAH 的产生抑制了烟灰表面的生长，从而导致在 DME 添加的火焰中亚 4 纳米烟灰的消耗相对较低。因此，由于亚 4 nm 烟尘颗粒的形成增强，DME 不能简单地被视为清洁燃料。在实际应用含氧燃料时，需要更加关注排放颗粒的尺寸分布，并采取适当的后处理技术，减少小颗粒的排放。OPAH 的产生抑制了烟灰表面的生长，从而导致在 DME 添加的火焰中亚 4 纳米烟灰的消耗相对较低。因此，由于亚 4 nm 烟尘颗粒的形成增强，DME 不能简单地被视为清洁燃料。在实际应用含氧燃料时，需要更加关注排放颗粒的尺寸分布，并采取适当的后处理技术，减少小颗粒的排放。