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Five kHz thermometry in turbulent spray flames using chirped-probe-pulse femtosecond CARS, part II: Structure of reaction zones
Combustion and Flame ( IF 4.4 ) Pub Date : 2019-02-01 , DOI: 10.1016/j.combustflame.2018.10.034
Albyn Lowe , Levi M. Thomas , Aman Satija , Robert P. Lucht , Assaad R. Masri

Abstract Temperature was measured in turbulent spray flames of ethanol and acetone stabilized on the piloted Sydney Needle Spray Burner (SYNSBURNTM) using single-laser-shot, chirped-probe-pulse femtosecond coherent anti-Stokes Raman spectroscopy (CPP-fs-CARS) with a repetition rate of 5 kHz. The burner features air-blast atomization of liquid injected from a needle that can be translated by a length Lr within a co-flowing air stream so that piloted spray flames ranging from dilute to dense can be studied. Part I of these investigations has reported on the CPP-fs-CARS technique and extensive details of data processing methodology. Part II is concerned with the structure of the reaction zones at different spray loadings and for different departures from blow-off. While not performed simultaneously, measurements of the size distribution of liquid fragments are also reported and discussed in conjunction with the measured temperature. Measured probability density functions of temperature show that for flames with the same liquid loading but different recess lengths, Lr, the near-field spray structure that forms upstream of x/D = 10 affects flame structure and stability further downstream. As the spray exiting the burner becomes denser, with a higher proportion of ligaments and ‘irregular’ shaped objects, the entrainment of hot pilot gases into the spray envelope is affected, hence changing the rates of vaporization and subsequent combustion. The reported results will also form a useful platform for validating sub-models of atomization and combustion in turbulent, dilute to dense spray flames.

中文翻译:

使用啁啾探针脉冲飞秒 CARS 在湍流喷雾火焰中进行 5 kHz 温度测量,第二部分:反应区的结构

摘要 使用单次激光发射、啁啾探针脉冲飞秒相干反斯托克斯拉曼光谱 (CPP-fs-CARS) 与在先导悉尼针式喷雾燃烧器 (SYNSBURNTM) 上稳定的乙醇和丙酮湍流喷雾火焰测量温度5 kHz 的重复频率。该燃烧器的特点是对从针头喷射的液体进行空气喷射雾化,该针头可以在共同流动的气流中平移长度 Lr,以便可以研究从稀到稠的先导喷射火焰。这些调查的第一部分报告了 CPP-fs-CARS 技术和数据处理方法的广泛细节。第 II 部分涉及不同喷雾负载和不同排放偏离的反应区结构。虽然不是同时进行,还报告并讨论了液体碎片尺寸分布的测量结果与测量温度的结合。测得的温度概率密度函数表明,对于具有相同液体负载但不同凹槽长度 Lr 的火焰,在 x/D = 10 上游形成的近场喷雾结构会影响下游的火焰结构和稳定性。随着离开燃烧器的喷雾变得更密集,具有更高比例的韧带和“不规则”形状的物体,进入喷雾包层的热引燃气体受到影响,从而改变汽化和随后燃烧的速率。报告的结果还将形成一个有用的平台,用于验证湍流、稀到浓喷射火焰中雾化和燃烧的子模型。
更新日期:2019-02-01
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