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Show particles at any given time, are significantly higher than those for the largest particles. The effect of trajectory is also especially apparent by comparing reaction efficiencies for the 5 J.Lm particles A, B, and C introduced at the three different radial positions. The slopes of the reaction history curves indicate the rates of reaction and depend on both the local fluid temperature and the availability of oxygen for combustion. Greater slopes indicate both high local temperature and availability of oxygen, while lower slopes indicate a combination of lower local temperatures and/or low availability of oxygen. As expected, the large particles burn slower than the small particles. In the time 2tUo/d = 0.6, the unburnt fraction for 5 J.Lm size particle is only between 0.2 to 0.3, whereas the heavy particles still have the unburnt fraction 0.9. 5 Conclusions Predictions of particle behavior, including path, temperature, and reactivity history, as reported here, strongly depend on input location and particle size. The rate of pyrolysis was shown to be highest for those particles injected closest to the center of the jet, while the rate of char reactivity was shown to depend on the details of the trajectory, with reaction rate increasing, remaining constant, or decreasing through regions of various temperature and oxygen concentrations. Particle reaction behavior is in qualitative agreement with the experimental results. For more quantitative agreement, we need a more accurate description of temperature and oxygen fields. However, these results indicate that the details of fluid flow, as it affects the individual particle combustion, may be used as an important tool for investigation of the total combustion behavior. References [1] C. F. Bender, R. H. Essenhigh, U. Ghia, and M. L. Mittal. 206th American Chemical Society National Meeting, Fuels Division:66-72, 1993. [2] K. A. Bueters, J. G. Cogoli, and W. E. Habelt. Fifteen Symposium (International) on Combustion, 15:1245-1260, 1974. 11 |