Loading...

Determination of Flameless Combustion flow Pattern for Methane-Fuel Burners

Jahedi, Morteza | 2023

60 Viewed
  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 56141 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Saeedi, Mohammad Hassan
  7. Abstract:
  8. Flameless combustion is a regime of combustion that is caused by slowing down the chemical reactions of combustion, which is the result of reducing the local concentration of oxygen in the combustion chamber. This reduction in oxygen concentration is mainly due to the strong recirculation of hot gases from combustion and the high mixing of these gases with the reactants. In this type of combustion, due to the reduction of hot spots, the production of nitrogen oxide pollutant is significantly reduced compared to normal combustion. The aim of this research is to determine the performance limits of flameless combustion in order to seriously reduce NOx and other pollutants. For this purpose, after carefully examining and choosing the appropriate kinetics for this type of combustion and the structure of the flameless combustion phenomenon, other factors affecting combustion such as the type of fuel and its geometry were also determined, and finally, in order to obtain the flameless combustion flow map, the temperature Intake air and air-to-fuel ratio were selected as variable parameters of the problem. In this research, the inlet conditions of the Dally furnace were changed in order to achieve the flameless combustion flow map in a relatively wide range, and the results showed that with the increase in the equivalence ratio of fuel and air, as well as the increase in the temperature of the inlet air, the conditions for achieving flameless combustion will be better. Of course, it should be noted that in some situations, even though the combustion occurs flameless, the amount of pollutants is higher compared to the combustion flameless in other conditions (but the pollutants of the examined cases are still very low compared to the normal combustion); For example, in the equivalence ratio of 0.8 and the inlet air temperature of 423 K, there is flameless combustion, but the amount of nitrogen oxide produced in this state is higher than in other states of flameless combustion. Therefore, the mere fact that the combustion is flameless is not enough to reduce pollutants, and the optimal mode must always be found for each furnace. In addition, the amount of carbon monoxide pollutant production is also different in each flameless combustion, and it should be noted that as the equivalence ratio and furnace air temperature increase, the amount of this pollutant in the furnace increases. Therefore, in addition to optimizing furnace inlet conditions to reduce nitrogen oxide, a balance must be established between its production rate and carbon monoxide production rate. According to the flow map obtained in this research, in order to achieve flameless combustion in the Dally furnace, if the equivalence ratio is less than 0.65, the inlet air temperature should be increased to more than 500 K. If it is in the range of 0.65 to 1.1, the inlet air temperature should reach more than 400 K, and for equivalence ratios higher than 1.1, the inlet air temperature of 320 K is sufficient
  9. Keywords:
  10. Moderate or Intense Low Axygen Dilution (MILD) ; Flamless Combustion ; Nitrogen Oxide Emission ; Flow Map ; Combustion Mood ; Flameless Combustion Regime ; Flameless Combustion Scale

 Digital Object List

 Bookmark

No TOC