THE EFFECT OF DROPLETS ON BUOYANCY IN VERY RICH ISO-OCTANE-AIR FLAMES | ||||
The International Conference on Applied Mechanics and Mechanical Engineering | ||||
Article 57, Volume 13, 13th International Conference on Applied Mechanics and Mechanical Engineering., May 2008, Page 199-209 PDF (671.47 K) | ||||
Document Type: Original Article | ||||
DOI: 10.21608/amme.2008.39305 | ||||
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Authors | ||||
SULAIMAN S. A.1; LAWES M.2 | ||||
1Senior Lecturer, Dept. of Mech. Eng., Universiti Teknologi Petronas, Malaysia. | ||||
2Senior Lecturer, School of Mech. Eng., University of Leeds, United Kingdom. | ||||
Abstract | ||||
ABSTRACT An experimental study is performed with the aim of investigating the effect of the presence of droplets in flames of very rich iso-octane-air mixture under normal gravity. Experiments are conducted for initial pressures in the range 100-160 kPa and initial temperatures 287-303 K at an equivalence ratio of 2.0. Iso-octane-air aerosols are generated by expansion of the gaseous pre-mixture (condensation technique) to produce a homogeneously distributed suspension of near mono-disperse fuel droplets. The droplet size varies with time during expansion; hence the effect of droplet size in relation to the cellular structure of the flame is investigated by varying the ignition timing. Flame propagation behavior is observed in a cylindrical vessel equipped with optical windows by using schlieren photography. Local flame speeds are measured to assess the effect of buoyancy in gaseous and aerosol flames. It is found that the presence of droplets results in a much earlier onset of instabilities, at a rate faster than that taken for the buoyancy effect to take place. Flame instabilities, characterised by wrinkling and cellular surface structure, increase the burning rate due to the associated increase in surface area. Consequently, the presence of droplets results in a faster flame propagation rate than that displayed by a gaseous flame. The mechanism of flame instabilities that causes a significant reduction of the buoyancy effect is discussed. | ||||
Keywords | ||||
Buoyancy; Combustion; Droplets; flame; Instabilities | ||||
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