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Accueil du site > Thèmes de recherche > Combustion & systèmes réactifs > 1.7 Multiphase gasification and combustion phenomena > 1.7.1 Vaporisation of liquid droplets and clouds

1.7.1 Vaporisation of liquid droplets and clouds

This research axis concerns the vaporisation of liquid fuel droplets after the primary and secondary atomisation phases, and is important for reactive mixture formation analysis in liquid fuel combustion systems, such as liquid rocket engines or lean prevaporized premixed gas turbine applications. Our global objectives are to experimentally characterize and model the vaporization properties of various liquid fuel droplets at high pressure and temperature conditions. High pressure enhanced natural convection effects are reduced by conducting the experiments under reduced gravitational acceleration conditions. During the last years, emphasis was put on droplet interaction effects. A specific apparatus was developed to observe and characterise high temperature vaporisation of a droplet network.

This set-up is also adapted for parabolic flight experiments in order to achieve reduced gravity conditions. n-Heptane droplets are deposited at the intersections of two cross wires of 0.014 mm in diameter, reducing drastically the fibre effect on the droplet vaporisation characteristics, as was inevitably observed with the classical large diameter fibre suspended droplet experiments. By comparing the two techniques, the effect of the heat transfer from the fibre was clearly identified and quantified. Correlations for the vaporisation rate were proposed allowing the unification of earlier results. Droplet interaction effects were investigated for n-decane droplets.

The vaporisation rate of the centre droplet in a 3D droplet network was measured and a reduction of about 60% was observed compared to single droplet vaporisation rates under identical surrounding conditions. These results, conducted within the CNRS-CNES coordinated action (GDR) on “Transport phenomena in microgravity” allows detailed comparisons with the numerical simulations of the literature (ACTI15, 23, 51). This work is presently extended to the vaporisation of droplet clouds.