Modelling soot formation from wall films in a gasoline direct injection engine using a detailed population balance model
Modelling soot formation from wall films in a gasoline direct injection engine using a detailed population balance model
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DOI：
10.1016/j.apenergy.2015.11.011
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发表时间：
2016-02
期刊：
影响因子：
11.2
通讯作者：
Buyu Wang;S. Mosbach;Sebastian Schmutzhard;S. Shuai;Y. Huang;M. Kraft
中科院分区：
文献类型：
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作者：
Buyu Wang;S. Mosbach;Sebastian Schmutzhard;S. Shuai;Y. Huang;M. Kraft
在本研究中，使用随机反应模型(SRM Engine Suite)模拟了汽油直喷(GDI)发动机中的碳烟生成，该模型包含一个能够描述颗粒形态和化学成分的详细的颗粒平衡碳烟模型。为了描述壁膜碳烟的形成，SRM发动机套件被扩展到包括喷雾撞击和壁膜蒸发模型。圆柱体被划分为壁面和体积区，以求解壁附近混合物的当量比和温度分布。假设燃烧室壁面只与壁面区域直接换热。用不同的混合模型模拟了不同区域内和两个区域之间的湍流混合。研究了关键参数对这两个区域温度和当量比的影响。壁面和块体之间的混合速度对壁面区域的影响很大，而壁面区域的混合速度对温度和当量比在某一阈值以下的影响很小。实验数据来自一台四缸汽油直喷火花点火发动机。为了研究喷雾撞击对碳烟形成的影响，进行了120CAD BTDC到330CAD BTDC的喷油定时扫掠。用当前模型模拟了最早的喷射工况(330 CAD BTDC)，其产生的颗粒物排放水平明显高于任何其他工况。结果表明，缸内压力和放热率与实验数据吻合较好。模拟得到的颗粒尺寸分布与实验结果具有相同的数量级。通过在当量比-温度图中跟踪颗粒，证明了壁面附近的浓淡混合物是由于壁膜蒸发而形成碳烟的来源。
In this study, soot formation in a Gasoline Direct Injection (GDI) engine is simulated using a Stochastic Reactor Model (SRM Engine Suite) which contains a detailed population balance soot model capable of describing particle morphology and chemical composition. In order to describe the soot formation originating from the wall film, the SRM Engine Suite is extended to include spray impingement and wall film evaporation models. The cylinder is divided into a wall and a bulk zone to resolve the equivalence ratio and temperature distributions of the mixture near the wall. The combustion chamber wall is assumed to exchange heat directly only with the wall zone. The turbulent mixing within each zone and between the two zones are simulated with different mixing models. The effects of key parameters on the temperature and equivalence ratio in the two zones are investigated. The mixing rate between the wall and bulk zone has a significant effect on the wall zone, whilst the mixing rate in the wall zone only has a negligible impact on the temperature and equivalence ratio below a certain threshold. Experimental data are obtained from a four-cylinder, gasoline-fuelled direct injection spark ignition engine operated stoichiometrically. An injection timing sweep, ranging from 120 CAD BTDC to 330 CAD BTDC, is conducted in order to investigate the effect of spray impingement on soot formation. The earliest injection case (330 CAD BTDC), which produces significantly higher levels of particle emissions than any other case, is simulated by the current model. It is found that the in-cylinder pressure and the heat release rate match well with the experimental data. The particle size distribution in the simulation has the same order of magnitude as the experimental one. By tracing the particles in an equivalence ratio-temperature diagram, it is demonstrated that the rich mixture near the wall becomes the source of the soot formation as a result of the wall film evaporation.