Experimental study of droplet temperature in a two-phase heptane/air V-ﬂame Camille Letty, Bruno Renou ⇑ , Julien Reveillon, Sawitree Saengkaew, Gérard Gréhan CORIA UMR 6614, CNRS, INSA de Rouen, 76801 Saint Etienne du Rouvray, France article info Article history: Received 30 May 2011 Received in revised form 23 August 2012 Accepted 14 March 2013 Available online 9 May 2013 Keywords: Two-phase combustion Global rainbow technique Droplet temperature abstract An understanding of the complex phenomena involved in droplet combustion, such as two-phase ﬂows and heat/mass transfer, is a necessary step towards improving combustion efﬁciency and reducing pol- lutant emissions. This paper is focused on an analysis of the droplet temperature evolution across the ﬂame front in two-phase ﬂow systems. In this experiment, the ﬂame was stabilized on a rod at atmo- spheric pressure and the fuel was liquid at injection, which implies the presence of fuel droplets close to the ﬂame front. However the ﬂame was partially premixed because part of the fuel vaporized quickly and contributed to the stabilization of the ﬂame. The conﬁguration was two-dimensional and so called ‘‘V-shape’’ ﬂame. Two different ﬂow conditions were investigated: a pseudo-laminar ﬂow as the refer- ence case (R) and a low-turbulence level ﬂow (LT). The evolution of the mean fuel droplet temperature across the ﬂame brush was quantiﬁed. The shape of the fuel droplet temperatures histogram became clearly bimodal for high values of the mean progress variable  c, indicating the presence of droplets in the measurement volume that were heated up by the burnt gases and the ﬂame. The temperature evo- lution and the statistics across the ﬂame front can be used to compare the numerical and the physical models applied to two-phase combustion. Ó 2013 The Combustion Institute. Published by Elsevier Inc. All rights reserved. 1. Introduction Turbulent spray combustion is used extensively to convert en- ergy in such practical applications as furnaces, gas turbines, and aeronautic or automotive engines. Nowadays these installations have to meet very strict economical and environmental speciﬁca- tions. To comply with these restrictions requires an in-depth understanding and modeling of the various physical phenomena interacting in the combustion chamber, which is fed by a liquid fuel. Two-phase combustion is a complex phenomenon involving the dispersion and the evaporation of a liquid fuel in a gaseous oxi- dizer. Capturing the mass and heat exchange between both phases is of primary importance to predict the topology of the gaseous fuel and the resulting combustion regimes. Nevertheless, a substantial lack of information regarding the various exchanges between the liquid and the gas phase, and their direct impact on the combus- tion processes, persists as a result of experimental and modeling difﬁculties, which arise from the simultaneous presence of the two phases. Although numerical simulation is a valuable tool to overcome many of these measurement difﬁculties, the method still needs to be validated through sound experimental studies. Fur- thermore, it is not yet able to tackle very complex conﬁgurations. It is therefore of fundamental interest to develop experimental set-up that are able to capture and analyze the various interactions between the liquid and gas phases in spray combustion. Previous studies dedicated to two-phase combustion have con- sidered generic conﬁgurations such as dilute laminar spray diffu- sion ﬂames in a coﬂow conﬁguration [1] or counter-ﬂow diffusion spray ﬂames [2]. Various combustion regimes have also been studied (for instance, partially pre-vaporized sprays [3], par- tially premixed spray jets [4], and swirling ﬂames [5,6] leading to partially premixed combustion). These experiments, dedicated to several aspects of two-phase combustion, were focused on ﬁve main areas of study: (i) the combustion regimes and the transitions between them, (ii) the ﬂame structures that resulted from the droplet diameter and the presence of droplets close to the ﬂame front, (iii) the relationships between strain rate and burning veloc- ity or temperature, (iv) the evolution of droplet velocity and size distribution during the combustion process, (v) the ignition of ﬂame kernels. One of the fundamental aspects to consider in two-phase ﬂow combustion is the heat transfer between the liquid and the gas phase that necessarily occurs during the vaporization process. Generally the temperature of the liquid phase injected into the combustion chamber is below the gas phase temperature. Most 0010-2180/$ - see front matter Ó 2013 The Combustion Institute. Published by Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.combustﬂame.2013.03.017 ⇑ Corresponding author. Address: CNRS UMR 6614, CORIA, Universite et INSA de Rouen, Site Universitaire du Madrillet, BP 12, 76801 Saint-Etienne du Rouvray Cedex, France. Fax: +33 2 32 96 97 80. E-mail address: bruno.renou@coria.fr (B. Renou). Combustion and Flame 160 (2013) 1803–1811 Contents lists available at SciVerse ScienceDirect Combustion and Flame journal homepage: www.elsevier.com/locate/combustﬂame