الفهرس 
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Abstract
The field of spray and combustion is very important to our lives, because it has several applications such as; diesel engines and spark ignition engines which used in cars, trucks, trains, gas turbine engines which used in planes and power plants, boilers which used in some industrial application to get steam or hot water and also in power plants to produce the electrical power which used to operate all electrical and electronics devices that we use.
The oil and gaseous fuels burning represents the main source of energy in the present time. So in this work, an experimental study of diesel fuel spray and combustion characteristics is carried out. The present experimental work is divided into two parts; the first part contains studying of the spray characteristics of the modified air blast atomizer using diesel fuel. The air blast atomizer is designed so that the atomizing air flows through its internal atomizing air swirler. The investigated parameters in this part are; (1) Atomizing air swirler angel (AASA) which takes values of 0°, 15°, 30°, and 45°, (2) Atomizing air to liquid ratio (AALR) which takes values of 1, 2, 3, 4, 5, 6, 7, and 8 and (3) The ratio of nozzle–orifice gap to fuel nozzle diameter (l/D) which takes values of 0, 1, 2 and 3.
The effects of changing the above parameters on the spray cone angle, spray intensity, spray concentration and spray momentum are measured for studying the spray characteristics.
The second part interested in studying the combustion characteristics of the modified air blast atomizer spray. The atomizing air and the combustion air have the same swirling direction. The investigated parameters in this part are; (1) Changing the atomizing air to liquid ratio (AALR) from 5 to 6, 7 and 8, (2) Changing the atomizing air temperature (AAT) from 300 to 350, 400 and 450 K, (3) Changing the atomizing air swirler angle (AASA) from 0° to 15°, 30° and 45°, (4) Changing the ratio of nozzle–orifice gap to fuel nozzle diameter (l/D) from 0 to 1, 2 and 3 and (5) Changing the atomizing air orifice diameter to fuel nozzle diameter (Da.a/D) from 7 to 8, 9 and 10. During the experimental runs the fuel mass flow rate, combustion air mass flow rate and combustion air swirl number are kept constants at 1.0 g/s, 40 g/s and 0.87, respectively.
The effects of the above parameters on the temperature maps, axial center line temperature distributions, temperature gradient, visible flame length and the combustion center line species concentrations are measured along water cooled combustor for studying the combustion characteristics. In order to study these two investigated parts, two test rigs were constructed; spray test rig and combustion test rig.
The experimental results show that, increasing both atomizing air swirl angle and atomizing air to liquid ratio led to increasing the spray cone angle, while by increasing l/D ratio from 0 to 3 led to decreasing the spray cone angle. The spray droplet intensity at the center line is found to be relatively high and by moving outward away from center line, spray intensity clearly decreases.
The high temperatures regions shifted upstream and became nearest to the burner head and also shifted outward far away from the combustor axial center line by increasing air liquid ratio, atomizing air swirl angle and atomizing air temperature while it is shifted downstream by increasing both l/D and Da.a/D ratios. The visible flame length is decreased and the flame became wider by increasing air liquid ratio, atomizing air swirl angle and atomizing air temperature, while it is increased and the flame became thinner by increasing both l/D and Da.a/D ratios. By increasing air liquid ratio, atomizing air swirl angle and atomizing air temperature the O2 and CO concentrations are decreased while NO and CO2 concentrations are increased at the center of the combustor exit.