الفهرس 
Flameless Combustor Design ConsiderationsOnly 14 pages are availabe for public view
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Abstract
The use of flameless combustion occupies a crucial role in industry sector such as gas turbine, power generation, cement industry and glass melting. Flameless combustion characteristics were analyzed numerically and experimentally at various design and operating conditions. An experimental test rig was constructed from scratch to analyze the effect of air to fuel ratio on flameless creation or abortion. Moreover, the influence of pre-heated combustion air temperature
was studied during the experimental plane. A numerical investigation of flameless combustion focusing on assessment of turbulence, combustion and radiation modelling was presented. The predicted results were validated with
experimental data of small-scale flameless burner. It was recommended to use realizable k- Ԑ and RNG k- Ԑ in flameless combustor modelling. Taking radiation modelling in consider yields to a very small discrepancies for the predicted results therefore, it wasn’t mandatory to take radiation effect in flameless modelling. The performance of different combustion and reaction modelling were investigated. A deviation
between predicted and measured temperature was noticed in all models, but EDC and GRI-EDC yields to smallest deviation. In general, GRI-EDC combustion model was recommended to predict the mean temperature and dry volume fraction of O2 and CO2, but a relatively large deviation for predicted CO species. Effect of inlet air momentum on flameless combustion characteristics was investigated numerically. Changing the inlet air momentum was obtained via using different inlet air nozzle
diameters (12, 10, 8 and 6 mm). Mixture mixing and recirculation ration were obtained and evaluated. Reducing the air nozzle diameter from 12 mm to 6 mm increases the inlet air momentum, therefore leads to an increase in the recirculation ration more than 300% of its value at 12 mm which decreases the O2 concentration in the mixture at burner tip and supports flameless
mode creation. Increasing inlet air momentum reduces the greenhouse gases due to the decrease in reaction temperature and mixture dilution. Air preheating temperature has a significant effect on flameless combustion. It is noticed that recirculation ratio decreases to less than its half value
at ambient temperature with increasing preheated air temperature up to 900 o
c. Higher air preheating temperatures can enhance the mixing of fuel and air, improving combustion efficiency and reducing the formation of NOx. However, if the preheating temperature becomes too high, it can lead to increased thermal NOx formation. It was noticed that increasing excess air ratio leads
to a reduction in the combustion temperature due to the increase the ignition delay. Higher excess air ratios generally lead to lower emissions of nitrogen oxides (NOx) due to the reduced
combustion temperatures and lower peak combustion temperatures. Higher excess air ratios contribute to lower OH emissions. The reduction in OH free radicals make the combustion zone
more flameless. Higher excess air ratios in flameless combustion promote better fuel-air mixing, resulting in improving combustion efficiency. A smaller fuel jet diameter can promote better
mixing of fuel and air, resulting in a more homogenous mixture and enhance mixture dilution. NOx emissions decrease with reducing fuel jet diameter due to improved mixing and reducing in
the combustion temperature. Smaller fuel jet diameters may enhance the mixing of diluents, leading to more effective NOx reduction. Increasing the number of fuel inlets improves fuel-air mixing within the combustion chamber. Improved mixing helps to distribute the heat release more evenly, reducing the formation of hotspots and slightly lowering the peak combustion temperature. Increasing the number of gas ports from 12 to 16 doesn’t have any effect on temperature
distribution or emissions. Increasing the number of fuel jet inlets can lead to reduced NOx and CO formation. Different values of radial position of the fuel jet were studied. It was found that when the fuel jet is positioned closer to the centerline, it promotes better fuel-air mixing and combustion,
leading to more complete combustion and reduced CO and NOx formation. In general, these conclusions will be a valuable knowledge for future flameless burner or combustor design and fabrication. Experimental tests lead to construct new burner design which suggested to create the flameless
mode using ambient temperature and which more applicable for small industrial applications. The use of a bluff body allows for better dilution of the fuel-air mixture, leading to improved combustion stability. The study successfully demonstrated the creation of flameless combustion without the need for preheated air temperature. The findings of this research contribute to
expanding the understanding of flameless combustion and provide valuable insights for the development of future combustion systems.