In the present work, detailed experimental investigations on lifted spray flames have been carried out to identify the various combustion modes using group combustion number analysis with kerosene fuel. The solid cone pressure swirl nozzle N1 (m_f = 1.7 kg/h at ΔP_inj = 9 bar) is considered, and fuel injection pressure varied from 3 to 48 bar. Detailed droplet size and droplet velocity measurements using shadowgraphy and particle image velocimetry (PIV) helped obtain the group combustion number and dimensionless droplet separation distance. A Chiu et al. (1977, 1982) criterion of group combustion number is used with experimental observations to understand the spray combustion mode in lifted spray flames. Internal group combustion mode is observed at lower injection pressures (3 bar) in which individual droplet combustion is significant. The combustion mode is defined by internal group combustion with a double reaction zone at intermediate pressures. The inner reaction zone burns with local extinction, and the outer reaction zone burns like a diffusion flame. A group combustion number range of 1−10³ is investigated for various combustion modes in lifted spray flames without coflow air. For air coflow conditions (V_coflow = 0.4 m/s), both the individual droplet burning mode and double reaction zone flame structure disappear from the flame. Small fuel vapor clouds burning with the external group combustion mode at higher injection pressures are observed in the G range of 10³−10⁶.

中文翻译：

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煤油提升喷雾火焰群燃烧模式作用的实验研究

在目前的工作中，对提升喷雾火焰进行了详细的实验研究，以使用煤油燃料的群燃烧数分析来识别各种燃烧模式。实心锥形压力涡流喷嘴 N1 (m _f = 1.7 kg/h at ΔP _inj= 9 bar) 被考虑在内，燃油喷射压力在 3 到 48 bar 之间变化。使用阴影成像和粒子图像测速 (PIV) 详细测量液滴尺寸和液滴速度有助于获得组燃烧数和无量纲液滴分离距离。邱等人。(1977, 1982) 群燃烧数准则与实验观察一起用于了解提升喷雾火焰中的喷雾燃烧模式。在较低喷射压力（3 bar）下观察到内部组燃烧模式，其中单个液滴燃烧显着。燃烧模式由在中间压力下具有双反应区的内部群燃烧定义。内反应区燃烧时局部熄灭，外反应区像扩散火焰一样燃烧。A组燃烧数范围1-10^图3研究了无共流空气的提升喷雾火焰中的各种燃烧模式。对于空气共流条件（V _coflow = 0.4 m/s），单个液滴燃烧模式和双反应区火焰结构都从火焰中消失。^{在 10 3} -10 ⁶的 G 范围内观察到在较高喷射压力下以外部组燃烧模式燃烧的小燃料蒸汽云。