Caractérisation expérimentale de la propagation d’une flamme laminaire dans un milieu diphasique (brouillard) à haute pression et en microgravité

摘要

Spray and aerosol cloud combustion accounts for 25% of the world’s energy use, and yet it remains poorly understood from both a fundamental and a practical perspective. Realistic sprays have a liquid breakup region, a dispersed multiphase flow, turbulent mixing processes, and various levels of flame interactions through the spray. Idealization of spray configurations in a quiescent environment (the starting point for models) has been impossible in 1 g due to the settling of large droplets and the buoyant pluming of post combustion gases. Testing in microgravity conditions relates to the possibility of creating aerosols without sedimentation effects. This research was to determine experimentally the flame propagation velocity in aerosols. First, the size of droplets in the aerosol was characterized using a laser diffraction particle size analyzer “Sympatec-HELOS”, and using ethanol as fuel. Second, high-Pressure combustion studies were performed using a high-Pressure combustion chamber (max pressure 12 MPa). These pieces of equipment were designed to be used in microgravity while aboard the Airbus A300-0g of the CNES. After ground tests, five parabolic flight campaigns were conducted. A systematic comparative analysis for identical initial conditions in both normal and reduced gravity was performed. The effects of initial temperature and pressure on the droplet diameter distribution of the aerosol, the effects of gravity on the flame behavior for both vapor-Air and droplet-Vapor-Air mixtures, and the effect of drops size on the flame speed and structure were all studied.