Pergamon Int. Comm. HeatMass Transfer, Vol. 28, No. 5, pp. 713--721, 2001 Copyright © 2001 Elsevier Science Ltd Printed in the USA. All rights reserved 0735-1933/01/S-see front matter PII: S0735-1933(01)00275-5 A THEORETICAL STUDY OF QUASISTEADY SPHERICOSYMMETRIC COMBUSTION OF ALCOHOL DROPLETS Achintya Mukhopadhyay and Dipankar Sanyal Department of Mechanical Engineering Jadavpur University Calcutta - 700 032 India (Communicated by A.R. Balakrishnan) ABSTRACT A distinct characteristic of alcohol droplet combustion is absorption of moisture, generated as combustion product, during early part of the droplet life. A theoretical model for combustion of alcohol droplets has been developed. The quasisteady sphericosymmetric gas phase equations have been solved analytically while the transient diffusive liquid phase equations have been solved numerically. It is observed that neglecting the effect of moisture absorption in combustion modelling leads to underprediction of droplet life and overprediction of flame temperature and flame stand-off ratio. The results show that for alcohols with boiling points lower than that of water, a significant amount of moisture, generated during combustion is absorbed by the droplet. Absorption of this moisture prolongs droplet life and reduces flame temperature. A similar effect is also observed with increasing initial moisture content in the droplet. © 2001 Elsevier Science Ltd Introduction Combustion of liquid fuel droplets has been studied extensively over the last few decades, owing to its importance in the combustion processes of compression ignition engines, power station gas turbine combustors, propulsion systems and oil-fired furnaces and boilers. The study of evaporation and combustion of individual droplets forms an important part of spray combustion analysis. The impetus for research in this field comes from the need of constant search for new grades of fuel owing to diminishing oil reserves, persistent demands for energy, and growing consciousness about efficient combustion and low level of pollutant emission. The search for alternative fuels has led to the exploration of feasibility of alcohol as a fuel. Although cheap and abundant, viability of alcohol as a fuel may be limited by its high latent heat of vaporisation and low heating value. Consequently, further research on combustion of alcohols, particularly in heterogeneous systems, is necessary. Law and Binark [1] analysed the vaporisation and transport of a mono-disperse fuel spray in a cold humid environment. Condensation of water vapour was considered to take place either homogeneously in the gaseous medium or heterogeneously on the droplet surface. This effect was found to substantially enhance the vaporisation rate, especially in the heterogeneous mode. Law et al. [2] studied alcohol droplet vaporisation in humid air, both analytically and experimentally. The analytical study was treated to be sphericosymmetric. 713