Soot nucleation in low-sooting high-pressure flames: Experiment and modeling

低烟灰高压火焰中的烟灰成核：实验和建模

• 批准号: 439059510
• 负责人: Professor Dr. Thomas Dreier
• 金额: --
• 依托单位: Institut für Energie- und Material-Prozesse (EMPI)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2020
• 资助国家: 德国
• 起止时间: 2019-12-31 至 2023-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/439059510?language=en
• 关键词: Soot; nucleation; low; sooting; pressure

Combustion is still by far the major source of power generation and therefore retains long-term practical importance, especially for the long-distance transportation sector. The related combustion processes are known to generate carbonaceous particles associated with negative climate impact and health hazards, especially for the small particle size classes. Therefore, the better understanding and reliable predictive modeling of soot formation pathways – particularly in pressure regions relevant for engine combustion – is of high interest. Especially the processes governing the initial steps of soot nucleation, and the balance between formation and oxidation in flames that operate close to the fuel/air ratio of soot formation are poorly understood, and there is still a controversy about these initiation mechanisms. Existing kinetics models for soot nucleation and growth based on hypotheses about PAH–PAH, radical–radical, and radical–PAH interactions are not experimentally verified. Therefore, the objective of this proposal is to improve the understanding of soot formation in flames at elevated pressure (2–20 bar) by supporting model development with an extended experimental database of spatially-resolved measurements of temperature, species concentrations, mean soot particle size, and volume fraction. This is accomplished using in situ optical diagnostics and thermophoretic soot sampling from up to now not investigated premixed methane/ethen/air flames at high pressures (1 – 20 bar) in regimes with low-sooting tendency achieveable by proper selection of equivalence ratios (i.e., low C/O ratio). To modify chemical routes towards soot formation soot promoting/suppressing additives (ethyne and hydrogen, respectively) will be mixed into the fresh gas flow. Measurements will be performed in two high-pressure burners with optical access supporting flat premixed flames. Time-resolved laser-induced incandescence (LII), optical extinction, tuneable diode laser absorption spectroscopy in the near- and mid-infrared, and soot pyrometry will be used to determine soot volume fraction, mean particle size, gas temperature and carbon monoxide and water vapor concentrations, respectively. For independent validation of the particle size distribution, spatially resolved soot sampling is carried out with subsequent electron microscopy analysis. To increase the range of studied total pressures and species measurements, we plan for a strong international collaboration with other expert groups: Researchers from Lille University (France) conduct measurements in sub-atmospheric flames and help establishing the high-pressure soot-balanced flames and associated models. Partners from Texas A&M University (USA) will provide temperature, CO, atomic hydrogen, and oxygen concentration profiles from an identical burner. The growing database will form the basis for chemistry modeling with partners from the University of Milan (Italy).

到目前为止，燃烧仍然是发电的主要来源，因此仍然具有长期的实际重要性，特别是对长途运输部门。众所周知，相关的燃烧过程会产生与负面气候影响和健康危害有关的碳质颗粒，特别是对于小颗粒类别。因此，更好地了解碳烟形成途径并建立可靠的预测模型--特别是在与发动机燃烧相关的压力区域--是非常有意义的。尤其是控制碳烟成核的初始步骤的过程，以及在接近碳烟形成的燃料/空气比的火焰中形成和氧化之间的平衡，人们对这些引发机制仍然存在争议。现有的基于多环芳烃-多环芳烃、自由基-自由基和自由基-多环芳烃相互作用假设的碳烟成核和生长动力学模型没有得到实验验证。因此，这项提议的目标是通过建立一个关于温度、物种浓度、平均碳烟颗粒大小和体积分数的空间分辨测量的扩展实验数据库来支持模型开发，从而提高对高压(2-20巴)火焰中碳烟形成的理解。这是利用现场光学诊断和热熔烟尘采样完成的，从目前为止，在高压(1-20bar)下尚未研究过的甲烷/乙烷/空气预混火焰，在具有低煤烟倾向的区域，可通过适当选择当量比(即低C/O比)来实现。为了改进煤烟形成的化学路线，将煤烟促进剂/抑烟剂(分别为乙炔和氢气)混合到新气流中。测量将在两个高压燃烧器中进行，该燃烧器具有支持扁平预混火焰的光学通道。时间分辨激光诱导白炽法(LII)、光学消光、近红外和中红外可调谐半导体激光吸收光谱以及碳烟热法将分别用于测量碳烟体积分数、平均颗粒尺寸、气体温度以及一氧化碳和水蒸气浓度。为了独立验证颗粒尺寸分布，进行了空间分辨的烟尘采样和随后的电子显微镜分析。为了扩大研究的总压力和物种测量的范围，我们计划与其他专家小组进行强有力的国际合作：来自法国里尔大学的研究人员在大气下火焰中进行测量，并帮助建立高压烟尘平衡火焰和相关模型。来自德克萨斯A&M大学(美国)的合作伙伴将提供来自相同燃烧器的温度、CO、原子氢和氧浓度分布。不断扩大的数据库将成为与米兰大学(意大利)的合作伙伴进行化学建模的基础。