The quasi-steady, spherically symmetric combustion of multicomponent isolated fuel
droplets has been modeled using modified Shvab-Zeldovich variable mechanism. Newly
developed modified Shvab-Zeldovich equations have been used to describe the gas phase
reactions. Vapor-liquid equilibrium model has been applied to describe the phase change at the
droplet surface. Constant gas phase specific heats are assumed. The liquid phase is assumed to
be of uniform composition and temperature. Radiative heat transfer between the droplet and
surroundings is neglected.
The results of evaporation of gasoline with discrete composition of hydrocarbons have been
presented. The evaporation rates seem to follow the pattern of volatility differentials. The
evaporation rate constant was obtained as 0.344mm2/sec which compared well with the unsteady
results of Reitz et al. The total evaporation time of the droplet at an ambience of 1000K was
estimated to be around 0.63 seconds. Next, the results of evaporation of representative diesel
fuels have been compared with previously reported experimental data. The previous experiments
showed sufficient liquid phase diffusional resistance in the droplet. Numerical results are
consistent with the qualitative behavior of the experiments. The quantitative deviation during the
vaporization process can be attributed to the diffusion time inside the droplet which is
unaccounted for in the model. Transient evaporation results have also been presented for the
representative diesel droplets. The droplet temperature profile indicates that the droplet
temperature does not reach an instantaneous steady state as in the case of single-component
evaporation.
To perform similar combustion calculations for multicomponent fuel droplets, no simple
model existed prior to this work. Accordingly, a new simplified approximate mechanism for
multicomponent combustion of fuel droplets has been developed and validated against several
independent data sets. The new mechanism is simple enough to be used for computational
studies of multicomponent droplets.
The new modified Shvab-Zeldovich mechanism for multicomponent droplet combustion has
been used to model the combustion characteristics of a binary alcohol-alkane droplet and
validated against experimental data. Burn rate for the binary droplet of octanol-undecane was
estimated to be 1.17mm2/sec in good concurrence with the experimental value of 0.952mm2/sec
obtained by Law and Law. The model has then been used to evaluate the combustion
characteristics of diesel fuels assuming only gas phase reactions. Flame sheet approximation has
been invoked in the formulation of the model.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/3320 |
| Date | 12 April 2006 |
| Creators | Vittilapuram Subramanian, Kannan |
| Contributors | Annamalai, Kalyan |
| Publisher | Texas A&M University |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Thesis, text |
| Format | 733884 bytes, electronic, application/pdf, born digital |
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