Combustion Phenomena of High Temperature Air Combustion - High Temperature Air Combustion: From Energy Conservation to Pollution Reduction - page 112

TABLE 2.7
Experimental Conditions

Items Specifications

Fuel JIS No. 1 Kerosene

Spray nozzle Hollow-cone type

Spraying angle: 60 degrees
Rated capacity: 0.3 gal/h

Spraying pressure 0.5 MPa

Oxygen content 3, 5, 8, 10, 12, 15%

m 3

In-furnace airflow rate 15

Preheating temperature 250 - 1100˚C

Gas Fuel: LPG,

Dilute: Nitrogen

experiment, the volume flow rates of both the diluting nitrogen and the air were
added together, to set the in-furnace airflow rate as 15 m 3 /h at normal condition.

2.4.1.2.2 Spray Pressure
It has been already confirmed that the finer the fuel droplets, the stabler the com-
bustion. Further, in the case of the pressurized spraying method, the spraying pressure
should be increased, because the fuel droplets are made fine when the spraying
pressure is high enough. However, even in the case of the experiment where the
injecting device with the accumulator was applied, the fuel flow rate was increased
as the spraying pressure was increased further. This resulted in easier generation of
incomplete combustion in a smaller test furnace to be measured. Therefore, tests
were carried out under the conditions where the ideally fine fuel droplets were used
and the spraying pressure was maintained around 0.5 MPa, where the characteristics
of the spray flame in diluted air could be easily observed. Under these experimental
conditions, the spraying pressure and the fuel flow rate were proportional. The fuel
flow rate is linearly varied with the spraying pressure.

2.4.1.2.3 Spraying Method
The following types of spraying methods can be used for finely atomizing the
liquid fuel: the oil hydraulic spraying type, which injects the liquid fuel at a high
speed; a twin fluid spraying type, which sprays the liquid fuel by gas jet diffusion;
a rotating type, in which the liquid fuel is sprayed by a centrifugal force; a colliding
nozzle type, in which the liquid fuel is collided to make fine particles; an oscillating
type, in which the liquid fuel is disrupted by such oscillation ultrasonic waves;
and a static electricity type, in which the liquid fuel is atomized by high voltage
static electricity.
The twin fluid spraying method makes measuring complicated because it takes
in air, steam, and other contaminants. Both the centrifugal force spraying method
and the ultrasonic wave spraying one are difficult to apply in an atmosphere of high
temperature air. Therefore, the commonly used oil hydraulic spraying method was
adopted to carry out the experiment. This spraying method has the following advan-