Evaluation of the Flame Lift-off Length in Diesel Spray Combustion Based on Flame Extinction
Evaluation of the Flame Lift-off Length in Diesel Spray Combustion Based on Flame Extinction
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DOI：
10.1299/jtst.5.238
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发表时间：
2010-12
影响因子：
1.2
通讯作者：
U. Azimov;N. Kawahara;E. Tomita;Kazuya Tsuboi
中科院分区：
文献类型：
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作者：
U. Azimov;N. Kawahara;E. Tomita;Kazuya Tsuboi
喷雾和燃烧过程的相互作用形成了内燃机中发生的复杂物理现象系统。研究这种相互作用对于确定同时减少柴油发动机烟灰和氮氧化物排放的策略非常重要。喷雾燃烧相互作用通过火焰升空长度来评估——从喷射器孔口到火焰射流中最接近喷射器的羟基发光位置的距离。各种工作致力于通过使用各种燃烧建模方法成功模拟柴油机的升焰。在这项工作中，火焰表面密度和小火焰概念用于模拟柴油升空长度。使用 ECFM3Z 模型和正庚烷燃料进行了数值研究，以确定静态条件下的火焰升空长度。数值结果与实验数据非常吻合，实验数据是从光学可访问的定容室获得的，并在桑迪亚国家实验室的发动机燃烧网络（ECN）上提供。结果表明，在距喷射器孔下游一定距离处，化学计量标量耗散率与消光标量耗散率相匹配。计算出的消光标量耗散率与火焰升空长度密切相关。对于所研究的条件范围，在各种环境气体 O2 浓度和环境气体密度下的提离长度的实验测量获得了足够的定量一致性。
The interaction of spray and combustion processes forms a complex system of physical phenomena undergoing in IC engines. Studying this interaction is important to determine strategies for simultaneously reducing soot and NOx emissions from diesel engines. Spray combustion interactions are evaluated by the flame lift-off length - the distance from the injector orifice to the location of hydroxyl luminescence closest to the injector in the flame jet. Various works have been dedicated to successful simulations of lifted flames of a diesel jet by use of various combustion modeling approaches. In this work, flame surface density and flamelet concepts were used to model the diesel lift-off length. Numerical studies have been performed with the ECFM3Z model and n-Heptane fuel to determine the flame lift-off length under quiescent conditions. The numerical results showed good agreement with experimental data, which were obtained from an optically accessible constant volume chamber and presented at the Engine Combustion Network (ECN) of Sandia National Laboratories. It was shown that at a certain distance downstream from the injector orifice, stoichiometric scalar dissipation rate matched the extinction scalar dissipation rate. This computed extinction scalar dissipation rate correlated well with the flame lift-off length. For the range of conditions investigated, adequate quantitative agreement was obtained with the experimental measurements of lift-off length under various ambient gas O2 concentrations and ambient gas densities.