BURNING RATES AND FLAME OSCILLATIONS IN GLOBALLY HOMOGENEOUS TWO-PHASE MIXTURES (FLAME SPEED OSCILLATIONS IN DROPLET CLOUD FLAMES)

Abstract

The study of spray combustion in industrial equipment is difficult due to the multiplicity of interdependent variables. Therefore, a combustion vessel was used for fundamental studies of aerosol combustion, under strictly controlled conditions of pressure, temperature and equivalence ratio. The droplet clouds were characterized using laser diagnostics, variables such as Sauter mean diameter, number density, gas and liquid equivalence ratios were determined. Nearly mono-sized droplet clouds were obtained in this vessel being the droplet diameter a function of time. The phenomenon of flame oscillation, the cyclic variation of flame speed during flame development, has been addressed in the past using several approaches but there is no yet a unique accepted explanation. The combustion studies in the present work revealed the differences between the speed of droplets and the gas velocity near the flame front. These resulted in variations in local equivalence ratio, which in turn manifested in flame speed oscillations.

Keywords:

• droplet cloud
• flame speed
• oscillations