Environmental Engineering Reference
In-Depth Information
Kogyo NFK (see Foreword). The injection nozzle was designed compactly about
10 mm in diameter, to minimize disturbance of the flame flow. For the vessel, a
pressurized oil storage vessel with an accumulator was prepared, instead of the usual
vessel with a spill-type nozzle, to permit control of both the injection pressure and
the injection volume.
2.4.1.1.1 Spraying Device
Schematic diagram of the whole device . The accumulator was filled with kerosene
and was used instead of a fuel tank. The following injection method was adopted.
A T pipe on the upper portion of the accumulator was set using a copper pipe 6 mm
in diameter. The required pressure was supplied using a high pressure air tank. In
the case of this injecting method, the time required for applying pressure was not
needed, and the necessary pressure could be obtained steadily by controlling the
opening of the regulator. The piping diagram is shown in Figure 2.75 . The spray
nozzle was connected to the furnace by a pressure hose, and it was secured on a
slider that was set up to a traverser, to prevent it slipping out of the bayonet angle
during testing and to enhance the reproducibility.
2.4.1.1.2 Combustion Device
A high temperature gas generator (the trade name is Airenthalpy Intensifier, AI, man-
ufactured by NFK) was used as the combustion device that can produce heated air at
a high temperature in a short time and that can also dilute simply the inside of the
furnace. Schematic diagrams of the combustion device are shown in Figure 2.1 and
the configuration of the heat reservoir and regenerator used in the present experiment
in Figure 2.76 . The heat reservoir is made of ceramic (aluminum titanate and cordierite)
and is in a honeycomb state. Meshes of 300/in 2 are set up in this heat reservoir, and
two of the heat reservoirs are arranged in each furnace, respectively.
2.4.1.1.3 Spray Nozzle
The nozzle used in the experiment was of a hollow-cone spray-flow type. It is
recognized that this type of nozzle can be used even in a furnace with a narrow
range to produce a stable flame at a lower outflow rate of the spray. The hollow-
cone spray flow is a flow of the fuel as follows. When liquid fuel is jetted out
conically at an angle to the liquid axis, a liquid film in a conical shape is atomized
into small particles, resulting in a hollow-cone spray. Since the pressure in the
vicinity of the central axis of such a spray is lower than the surrounding pressure,
the ambient air is forced in and small liquid droplets are transferred to the central
part by this airflow. As a result, a classification of droplet diameters occurs, that is,
the comparatively smaller liquid droplets concentrate at the central part and the
larger droplets at spray boundary.
Further, if the ambient pressure becomes higher and the density of ambient gas
is also increased, the divergent angle of spray becomes narrow, resulting in the state
of spray becoming nearer to an axial spray having a high flow rate of liquid droplets
even at the central portion of flow. This is because, when the gas density becomes
higher, exchange of the respective momentum of both the liquid droplets and the
gas is quickened, and therefore the pressure lowering rate at the central portion of
the spray flow increases. The divergent angle (spraying angle) of the spray is decided
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