Novel cloud chamber design for 'transition range' aerosol combustion studies

Combustion of liquid fuel sprays is employed in a diverse range of industrial applications. Aerosol combustion characteristics differ to those exhibited by gaseous combustion primarily due to the heterogeneity of the unburnt aerosol mixture. Simplified models of aerosol burning rate have identified possible laminar burning velocity enhancement for aerosol fuel/air systems comprising droplet sizes within the so-called combustion 'transition range'-typically understood to be 5-15 mum for mono-disperse aerosols. However, burning velocity enhancement has not been validated to date, and hence understanding of aerosol combustion mechanisms is limited for conditions of considerable practical importance. This paper describes the methodology utilized to design and commission an integrated cloud chamber/combustor capable of systematically producing quasi-monodisperse droplet mists within the combustion 'transition range' for the first time. The principle of Wilson's cloud chamber is used to produce quasi-monodisperse ethanol aerosol clouds, facilitating systematic cloud generation across the combustion 'transition range'. The Malvern Mastersizer X (TM), operating in transient mode, is used to examine droplet growth, final droplet size and mono-dispersity, while Particle Image Velocimetry is used to confirm pre-ignition quiescence. The creation of quasi-monodisperse, quiescent mists comprising droplets within the combustion 'transition range' facilitates aerosol combustion studies (e.g. flame propagation, ignition energies, etc.) of importance to explosion hazard quantification as well as other industrial applications such as internal combustion engines.