الفهرس 
CHAPTER 1Only 14 pages are availabe for public view
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Abstract
Considerable percentages of fuels are in a liquid phase such as diesel, straight
vegetable oils, biodiesel and Jatropha oil. The world oil consumption has been increasing,
mainly because of its usage in many industrial applications such as gas turbine engine
combustors, industrial furnace, and power generation applications. Therefore, the
investigation of liquid fuels combustion remains an important research topic. Also, it is
clear that the environmental pollution is increasing dramatically and reaching to alert
levels. Therefore, it is vital for industries in Egypt to burn the liquid fuels with high
efficiency and low pollutant emissions.
In the present study, the spray combustion produced by an external mixing air -
assist atomizer is investigated experimentally at different designs and operating
conditions. A test rig is built up to study the direct combustion of a diesel fuel in a
horizontal cylindrical combustor cooled by a water jacket. The performance of a special
design of an external mixing air - assist atomizer at different atomizing air pressures and
different air swirl angles is investigated experimentally. The atomizer design allows
changing the atomizing air swirl angle. Three cases of swirl angles (15, 30 and 45o)
relative to air stream in addition to no-swirl case are considered. The axial and radial
flame temperature profiles, the heat flux for the water jacket, combustion efficiency,
flame stability, furnace efficiency, and exhaust gas emissions over wide ranges of air to
fuel ratios (A/F) are obtained. Also, direct imaging of the free flame is taken at all
considered cases. Moreover, a comparative study for combustion and emission
characteristics between diesel fuel and blend B-10 (diesel &10% biodiesel) is carried out.
Finally, the effect of exhaust gas recirculation (EGR) as atomizing fluid instead of air on
combustion and emission characteristics is also studied.
It is found that, the axial inflame temperature increases with increasing the air to
fuel ratio up to certain ratio. Moreover, increasing air to fuel ratio up to 40 kgair/kgfuel
leads to decrease the confined flame length (by 44% relative to the length at A/F=14 kgair/kgfuel which is almost stoichiometric) and subsequently, decreases the amount of heat
flux to the cooling water jacket. Moreover, it was found that CO and NOx concentrations
decrease by 69.4 % and 46 % with increasing air-to-fuel ratio up to A/F=35 kgair/kgfuel,
respectively.
The effect of atomizing air pressure is studied and the results showed that,
increasing the atomizing air pressure up to 2 bar leads to increasing the axial inflame
temperature, decreasing the confined flame length by 38.75 % relative to the length at
Pa=0.5 bar. Subsequently, the amount of heat flux to the cooling water jacket and the
exhaust gas temperature decreases by 10 % relative to the temperature at Pa=0.5 bar. CO
and NOx emissions are increased by 36.4 % and 47.22 % relative to the emissions at
Pa=0.5 bar respectively, as the atomizing air pressure increased from 0.5 to 2 bar.
The study also shows that, As the atomizing air swirl angle increases, the flame
temperature increases in the flame region near to atomizer tip because of good mixing. At
small swirl angle, the trailing edge flame temperature is higher than those of big swirl
angle. Increasing the atomizing air swirl angle up to 45o reduces the flame length (by
36.1 % relative to the length at θs= 0o) at the same air-to-fuel ratio. Increasing the
atomizing air swirl angle increases the heat flux in the flame region near to atomizer tip
because of good mixing and high temperature. At small swirl angle of atomizing air, the
trailing edge heat flux is higher than those of big swirl angle. Increasing the atomizing
air swirl angle up to 45o leads to increasing CO and NOx emissions.
A comparative study for combustion characteristics between diesel fuel and blend
B10 (diesel&10% biodiesel) is performed. The results show that, diesel fuel enhances the
flame temperature and the heat flux to the water jacket, but the pollutant emissions
decrease.
Exhaust gas recirculation (EGR) is an effective strategy to control NOx emissions
from furnaces. It is found that the concentration of NOx decreases with using EGR by 15
% as the temperature decreases.