Evaluation of temperature gradients within combusting droplets in linear stream using two colors laser-induced fluorescence

Abstract

To cite this version:Guillaume Castanet, Alain Delconte, Fabrice Lemoine, Loïc Mees, Gèrard Gréhan. Evaluation of temperature gradients within combusting droplets in linear stream using two colors laser-induced fluorescence. Experiments in Fluids, Springer Verlag (Germany), 2005, 39 (2), pp.431 -440. 10.1007/s00348-005-0931-6. hal-01570421 ORIGINALS Guillaume Castanet AE Alain Delconte AE Fabrice Lemoine Loı¨c Mees AE Ge`rard Gre´han Evaluation of temperature gradients within combusting droplets in linear stream using two colors laser-induced fluorescence Abstract The scope of this paper concerns the heating process of fuel droplets injected in a hot gaseous environment. The two colors laser-induced fluorescence technique allows measuring the temperature distribution within a droplet by scanning the droplet volume by a sufficiently small probe volume compared to the droplet volume itself. The temperature field is reconstructed using two approaches which have been compared. One is based on a geometrical optics model and the other is based on the 3D calculation of the internal excitation field within the droplet, using the generalized LorenzMie theory. Experimental results have been obtained on a combusting monodisperse ethanol droplet stream (diameter around 200 lm).

Temperature and chemical composition of droplets by optical measurement techniques: a state-of-the-art review

“…The outskirt of the droplet remains mostly blank which reflects the lower contribution of this region to the signal due to the lens effect. Similar results were also obtained with the use of GLMT (Castanet et al 2005a). The method described above was used to investigate the heating of droplets of about 200 lm in diameter, i.e., about 10 times the dimensions of the measurement volume.…”

“…18 can be also modified in order to obtain the temperature distribution inside the droplet (Castanet et al 2003b(Castanet et al , 2005a(Castanet et al , 2011a. This is only possible in the case of monodisperse droplet streams as a result of the large number of droplets that can be sampled and their high reproducibility.…”

“…The Mie theory and geometrical optics were used to rigorously calculate the excitation field inside the droplet and the fluorescence signal emerging toward the detector (Castanet et al 2005a;Domann and Hardalupas 2001;Domann et al 2002;Frackowiak and Tropea 2010a, b;Zhang and Melton 1993). In the case of a laser beam arbitrary shaped like a Gaussian beam, the Generalized Lorenz-Mie theories (Gouesbet and Gréhan 2011) can be used as an extension of the Mie theory.…”

An improved size and refractive index measurement of a pentadecane single droplet in a heated chamber

“…The fuel droplet behaviors including size and refractive index are important parameters for the evaluation of the characteristics and behaviors of fuel droplets in a combustion chamber. Various droplet behaviors have been investigated such as evaporation by Wilms [1], size by Glover et al [2], temperature by Castanet et al [3,4] and refractive index and rainbow angle (for refractive index determination) by Roth et al [5,6] and Anders et al [7]. In addition, droplet temperatures and droplet fractions of the components inside the droplet as in the case of multi-component droplets can be determined from the measured refractive index value.…”

“…Groups of fuel droplets in the form of spray which cannot be used to determine accurately the individual fuel droplet characteristics have also reported [8]. Behaviors of many droplets presented as an average value were also not the real presentation of the only one droplet behaviors [3]. Honnery et al [13] have examined the behaviors of small droplet size (of less than 100 µm) and velocity measured by the Magnified Digital In-line Holographic Particle Image Velocimetry (MDIH-PIV) technique with a HeNe laser, but have not measured the refractive index.…”