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首页> 外文期刊>Combustion and Flame >Large eddy simulation of pressure and dilution-jet effects on soot formation in a model aircraft swirl combustor
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Large eddy simulation of pressure and dilution-jet effects on soot formation in a model aircraft swirl combustor

机译：飞机涡旋燃烧器中压力和稀释射流对烟尘形成的大涡模拟

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Soot formation in a model aircraft engine configuration operating at elevated pressures is studied using large eddy simulation (LES) and detailed models for precursor and soot population evolution. Specifically, pressure and secondary oxidation air injection effects on soot formation are simulated. The configuration simulated is a dual-swirl ethylene/air combustor operating at pressures of 3 and 5 bars, with and without secondary oxidation air injection. The inflow conditions are chosen such that for the two different pressures, the only hydrodynamic change is the Reynolds number. Detailed comparisons with experimental data show that the simulation captures gas-phase statistics accurately. Although the spatial structure of soot formation is captured, including some of the trends for different operating conditions, the quantitative comparisons had significant differences. This could be attributed to the large distribution in the measurements or the chemical/physical models for soot formation. Detailed analysis showed that soot mass generation in such devices is driven by acetylene-based surface growth, with strong oxidation zones that significantly reduce net soot emissions. More importantly, soot formation occurs due to a spatially and temporally intermittent phenomena, where a small set of fluid trajectories that deposit fuel-rich pockets into the right gas-phase conditions is responsible for the bulk of soot mass generated. The occurrence of these relatively low-frequency trajectories is due to large scale unsteadiness caused by the strong swirl near the fuel jets. Lagrangian particle trajectory analysis revealed that lower pressure case without sidejet injection encourages entrainment of soot particles into the inner recirculation zone, increasing the residence time and leading to increased soot volume fraction. When pressure is increased from 3 to 5 bar, these particles move through a different mixture fraction-progress variable phase space. Consequently, there is a hydrodynamic scaling mode introduced, which can produce interesting variations from the nominal pressure scaling for soot production. These studies point to an intricate dependence of soot formation on large-scale turbulent flows, which is generally non-universal and not observed in canonical jet flames. (C) 2018 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
机译：使用大型涡流仿真（LES）和详细的前驱体和烟尘种群演化模型，研究了在高压下运行的模型飞机发动机配置中的烟尘形成。具体而言，模拟了压力和二次氧化空气注入对烟灰形成的影响。模拟的配置是双旋流乙烯/空气燃烧器，在3巴和5巴的压力下运行，带有或不带有二次氧化空气注入。选择流入条件，使得对于两个不同的压力，唯一的流体动力学变化是雷诺数。与实验数据的详细比较表明，该模拟可准确捕获气相统计数据。尽管捕获了烟尘形成的空间结构，包括不同操作条件下的一些趋势，但定量比较却存在显着差异。这可能归因于烟尘形成的测量值或化学/物理模型中的较大分布。详细的分析表明，此类设备中烟尘的产生是由基于乙炔的表面生长驱动的，具有强大的氧化区，可大大减少烟尘的净排放量。更重要的是，烟尘的形成是由于空间和时间上的断续现象而引起的，其中少量的流体轨迹将富含燃料的气穴沉积到正确的气相条件中，这是产生烟尘质量的主要原因。这些相对低频的轨迹的出现是由于燃料喷嘴附近的强烈旋流引起的大规模的不稳定。拉格朗日粒子轨迹分析表明，在没有侧喷的情况下，低压情况会促使烟尘颗粒夹带进入内部再循环区，从而增加了停留时间并导致烟尘体积分数增加。当压力从3 bar增加到5 bar时，这些颗粒将通过不同的混合物分数前进可变相空间。因此，引入了一种流体动力结垢模式，该模式可以产生与烟灰生产的标称压力成比例的有趣变化。这些研究指出烟尘形成对大规模湍流的复杂依赖性，这通常是不普遍的，并且在规范射流火焰中没有观察到。 （C）2018年燃烧研究所。由Elsevier Inc.出版。保留所有权利。

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