Early Flame Development in the Combustion of Droplet and Vapour Mixtures

Abstract:

Experimental investigations of combustion of droplet and vapour mixtures under quiescent condition have been conducted in a closed combustion vessel. Droplet and vapour mixtures or aerosol mixtures were generated by expansion of iso-octane gaseous pre-mixture to produce a homogeneously distributed suspension of fuel droplets. The aerosol mixtures were ignited centrally in the combustion vessel and the flame development was recorded by schlieren photography. The effect of fuel droplets in the early stage of flame propagation was investigated by comparing the flame structure and flame speed of gaseous mixtures at identical conditions. Comparison between gaseous and aerosol flame have shown quantitatively that the presence of fuel droplets causes earlier onset of instabilities and cellularity than for gaseous flames, particularly at rich conditions. This difference was shown to be a function of droplet size and overall equivalence ratio. It is suggested that these factors lead to vary the local equivalence ratio which increases the initial burning rate of lean aerosols, but decreases that of rich ones.

• Periodical: Applied Mechanics and Materials (Volume 388)
• Pages: 223-228
• DOI: https://doi.org/10.4028/www.scientific.net/AMM.388.223
• Online since: August 2013
• Authors: Aminuddin Saat, Mazlan Abdul Wahid, Muhamad Said Mohd Farid
• Keywords: Burning Rate, Droplet, Flame Speed

References

[1] Hayashi, S., Kumagai, S., Flame propagation in fuel droplet-vapor-air mixtures, Proc. Comb. Inst. 15: 445-452 (1974).

DOI: 10.1016/s0082-0784(75)80318-3

[2] Nomura, H., Koyama, M., Miyamoto, H., Ujiie, Y., Sato, J., Kono, M., Yoda, S., Microgravity experiments of flame propagation in ethanol droplet-vapor-air mixture, Proc. Comb. Inst. 28: 999-1005 (2000).

DOI: 10.1016/s0082-0784(00)80307-0

[3] Lawes, M., Lee, Y., Marquez, N., Comparison of iso-octane burning rates between single-phase and two-phase combustion for small droplets, Comb. and Flame 144: 515-525 (2006).

DOI: 10.1016/j.combustflame.2005.07.015

[4] Polymeropoulos, C.E., Flame propagation in aerosols of fuel droplets, fuel vapour and air", Combution Science and Technology 40: 217-232 (1984).

DOI: 10.1080/00102208408923807

[5] Nomura, H., Kawasumi, I., Ujiie, Y., Sato, J., Effects of pressure on flame propagation in a premixture containing fine fuel droplets, Proc. Comb. Inst. 31: 2133-2140 (2007).

DOI: 10.1016/j.proci.2006.07.036

[6] Wilson, C. T. R., Condensation of water vapour in the presence of dust-free air and other gases, Proc. of the Royal Society of London 189: 265-307 (1897).

DOI: 10.1098/rsta.1897.0011

[7] Saat, A., "Fundamental studies of combustion of droplet and vapour mixtures, PhD Thesis, School of Mechanical Engineering, University of Leeds (2010).

[8] Bachalo, W.D., Rosa, A. B., Sankar, S.V., Diagnostic for fuel spray characterisation, in Combustion measurements, (Ed. Chigier N. ), Hemisphere, pp.229-278 (1991).

[9] Atzler, F., Fundamental studies of aerosol combustion, PhD Thesis, School of Mechanical Engineering, University of Leeds (1999).