Numerical study for the combustion characteristics of Orimulsion fuel in a small-scale combustor

A numerical and experimental study has been made in order to figure out the combustion characteristics of Orimulsion fuel for the possible substitution of traditional fuels in existing boilers. To this end, a comprehensive computer model has been developed using Patankar’s SIMPLE algorithm for the complex process associated with the turbulent reaction of this fuel. The program includes several phenomenological models such as behavior of fuel droplet, multi-phase reaction and formation of pollutant species such as NO and SO2 in radiation-participating, turbulent flows.The calculation results of species and temperature profiles have been successfully compared with the experimental data measured in a small-scale combustor. Comparing the combustion characteristics of Orimulsion with that of heavy fuel oil, one of the noticeable features of Orimulsion combustion is relatively low flame temperature together with the delayed appearance of the peak flame. This is considered to be attributed to the effect of moisture content and the increased flow rate of Orimulsion fuel on the basis of an equivalent calorific value. Further this feature of Orimulsion flame observed in calculation and experiment are consistent with other experimental findings reported in open literature.It is found that the flame characteristics of Orimulsion fuel can be changed to some extent by the variation of operation conditions such as the injection velocity of Orimulsion fuel and the swirl strength of air stream. Further, other parametric study has been made in terms of the type of atomizing fluid, equivalence ratio, radiation model and grid size. In general the results are physically acceptable and consistent. Therefore the computer program developed is considered as a viable tool for the advanced design and determination of optimal operating condition for the large scale of Orimulsion combustor.