Experiments in Fluids ( IF 2.4 ) Pub Date : 2021-04-12 , DOI: 10.1007/s00348-021-03197-5 Manuel Vogel , Michael Bachfischer , Jan Kaufmann , Thomas Sattelmayer
Abstract
In this study a measurement technique for determination of equivalence ratio fluctuations from flame chemiluminescence in a kerosene-fuelled lean premixed combustor under atmospheric conditions is presented. Firstly, fundamental investigations into the relationship between the ratio of different chemiluminescence signals and the equivalence ratio are carried out using an imaging spectrometer. The chemiluminescence intensity is recorded for a wide range of equivalence ratios and fuel mass flows during steady state operation. The spectra show that the CH*/OH* ratio depends linearly on the equivalence ratio and is independent of the mass flow in the investigated range. Moreover, the background radiation has no influence on the monotonous trend of the CH*/OH* ratio for kerosene combustion. This interesting finding opens up new possibilities for passive optical measurement of the equivalence ratio in kerosene flames. Bandpass-filtered phase-correlated images of OH* and CH* chemiluminescence of an acoustically excited flame are taken simultaneously on one camera chip using an image doubler. After distortion correction, the image pair is used to calculate the global equivalence ratio from the CH*/OH* ratio. Based on the calibration chart derived in stationary operation, phase-resolved equivalence ratio perturbations are determined during acoustic excitation. The presented technique allows a quantitative measurement of equivalence ratio fluctuations in spray combustion and can therefore provide a better understanding of the fundamental mechanisms of thermoacoustic instabilities triggered by equivalence ratio fluctuations.
Graphic abstract
中文翻译:
贫油预混煤油燃烧器当量比波动的实验研究
摘要
在这项研究中,提出了一种在大气条件下确定由煤油供油的稀薄预混燃烧器中火焰化学发光引起的当量比波动的测量技术。首先,使用成像光谱仪对不同化学发光信号的比率与当量比率之间的关系进行了基础研究。在稳态操作期间,记录了当量比的宽范围的化学发光强度和燃料质量流量。光谱表明,CH * / OH *比值线性取决于当量比,并且与研究范围内的质量流量无关。此外,背景辐射对煤油燃烧的CH * / OH *比的单调趋势没有影响。这一有趣的发现为煤油火焰中的当量比的无源光学测量开辟了新的可能性。使用图像倍增器,在一个摄像头芯片上同时拍摄声激发火焰的OH *和CH *化学发光的带通滤波后的相位相关图像。在畸变校正之后,图像对用于根据CH * / OH *比率计算全局等效比率。根据在静态操作中得出的校准图,确定在声激励过程中的相分辨等效率扰动。提出的技术可以定量测量喷雾燃烧中的当量比波动,因此可以更好地理解当量比波动触发的热声不稳定性的基本机理。