Lift-off and stabilization of n-heptane combustion in a diesel engine with a multiple-nozzle injection
Lift-off and stabilization of n-heptane combustion in a diesel engine with a multiple-nozzle injection
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DOI：
10.1016/j.proci.2012.06.111
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发表时间：
2013
期刊：
影响因子：
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通讯作者：
Rickard Solsjö;Mehdi Jangi;C. Chartier;Ö. Andersson;X. Bai
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文献类型：
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作者：
Rickard Solsjö;Mehdi Jangi;C. Chartier;Ö. Andersson;X. Bai
本文提出了重型柴油发动机火焰升空和稳定机制的联合数值和实验研究。采用不同喷嘴配置的喷射策略可以量化存在涡流时不同喷射间角度间距的影响。为此，本研究选择了三种不同的喷射间角度； 45°、90° 和 135°。利用正庚烷的详细化学动力学机制进行大涡模拟，以解决湍流燃料和空气混合问题，并捕获点火和火焰锋周围的重要物质，以描述火焰稳定过程。对 OH 化学发光进行测量，以确定光学可访问发动机中的火焰升起位置。总体而言，环境空气中的旋流对升空影响较大，射流上风侧和顺风侧的升空长度相差15%。 LES 结果表明，重要的点火反应在升空位置前面的广阔区域内发生。随着射流间角度的减小，相邻射流对热产品输送的影响变得更加突出。升空长度周围的热储层会增加局部环境温度，并通过混合冷喷射燃料和热空气来增强自燃过程。
This paper presents a joint numerical and experimental investigation of flame lift-off and stabilization mechanisms in heavy-duty diesel engines. The injection strategy, employing different nozzle configurations, allows for quantification of the impact of varying inter-jet angle spacing in the presence of swirl. For this purpose, three different inter-jet angles are chosen in this study; 45°, 90° and 135°. Large-eddy simulations are performed utilizing a detailed chemical kinetic mechanism for n-heptane to resolve the turbulent fuel and air mixing and to capture the important species surrounding the ignition and flame-fronts to describe the flame stabilization process. Measurements are carried out for OH chemiluminescence to identify the flame lift-off position in an optical accessible engine. In general, the swirl flow in the ambient air shows a great impact on the lift-off, with a 15% difference in the lift-off lengths on the upwind and downwind side of the jet. The LES results show that important ignition reactions undergo in a broad region in front of the lift-off position. With decreasing inter-jet angle, it is shown that the impact of transportation of hot products from adjacent jets becomes more prominent. Hot reservoirs surrounding the lift-off length increase the local ambient temperature and augment the auto-ignition process by mixing of the cold injected fuel and hot air.