Fluid sprinkling – spraying – and diffusing – Combining of separately supplied fluids – Including whirler device to induce fluid rotation
Reexamination Certificate
2003-01-17
2004-09-07
Mar, Michael (Department: 3752)
Fluid sprinkling, spraying, and diffusing
Combining of separately supplied fluids
Including whirler device to induce fluid rotation
C239S403000, C239S405000, C060S748000, C060S743000
Reexamination Certificate
active
06786430
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid atomizing nozzle, and more particularly to a liquid fuel atomizing nozzle to be used in a combustion chamber of a jet engine, gas turbine or the like, by an air stream of air or the like.
2. Description of the Related Art
As one means for atomizing liquids, there are air-blast liquid fuel atomizing nozzles which atomize liquid fuel by means of an air blast, which have come to be used in recent jet engines and liquid fueled gas turbines. Air-blast liquid fuel atomizing nozzles are a form of nozzle wherein liquid fuel is atomized by means of an air blast which flows into a combustion chamber. The liquid fuel is supplied in the form of a liquid film, and as a result of this thin liquid film contacting with an air stream having a speed of several tens of meters per second, is atomized from the front end edge of the nozzle into free space. Atomization is facilitated by supplying liquid fuel in a liquid film.
FIG. 4
is a diagram which shows one example of the structure of a typical air-blast liquid fuel atomizing nozzle of the liquid film method. FIG.
4
(
a
) is a longitudinal sectional view thereof, FIG.
4
(
b
) is a B
4
—B
4
sectional view of (
a
), FIG.
4
(
c
) is a C
4
—C
4
sectional view of (
a
), and FIG.
4
(
d
) is a D
4
—D
4
sectional view of (
a
). The air-blast liquid fuel atomizing nozzle
30
(hereafter abbreviated as “atomizing nozzle”) shown in
FIG. 4
comprises a tapered outer cylinder
32
which is formed with a progressively thin-walled front end section, and an inner cylinder
33
which is arranged within the outer cylinder
32
in a condition extending along the same axis. An annular space
37
which is open towards the front end side is formed between the inner wall surface
35
of the outer cylinder
32
and the outer wall surface
36
of the inner cylinder
33
. The annular space
37
is formed in a conical shape of a reducing diameter towards the front end side. The outer cylinder
32
and the inner cylinder
33
connect at a cylindrical nozzle base
34
in the back end.
The back end section of nozzle base
34
is connected to a pipe
40
to receive a supply of a liquid fuel LF to be atomized, and the liquid fuel LF supplied though the pipe
40
passes through a passage
41
formed within the nozzle base
34
and flows into an annular liquid reservoir
42
formed within the same nozzle base
34
. The liquid reservoir
42
and the annular space
37
, as is shown in FIG.
4
(
d
) in particular, connect through a plurality of spiral passages
43
which are formed in parallel to each other. The liquid fuel LF which has flowed into the annular space
37
from the spiral passages
43
, flows and forms a liquid film FF over the inner wall surface
35
of the outer cylinder
32
, and is atomized from a front end edge
44
arising from the thin wall of the outer cylinder
32
and flows out into free space.
The liquid fuel LF is given a rotating motion by being passed through the spiral passages
43
, and this rotation produces an action of inducing a spreading and moreover stabilization and the like in the liquid film FF on the inner wall surface
35
of the outer cylinder
32
. The part of the atomizing nozzle
30
that forms the liquid film FF is called a prefilmer (liquid film forming section)
45
. Along an outer wall surface (the outer wall surface of the outer cylinder
32
)
46
and an inner wall surface (the inner wall surface of the inner cylinder
33
)
47
of the prefilmer
45
, air is flowing into a combustion chamber (the air streams Ao, Ai). Most commonly, a rotating motion is given to the air streams Ao, Ai which flow through the passages within and without the prefilmer
45
by swirl vanes
48
,
49
in order to facilitate mixing of air and fuel particles that have been atomized and in order to stabilize the flame within the combustion chamber. The liquid film FF is atomized largely through air encountering these, namely an air stream Ai flowing along the inner wall surface
47
, but the rotation of the air stream Ai on this inner side is also effective in stabilizing the liquid film FF on the prefilmer
45
. The air stream Ao which flows along the outer wall surface
46
of the prefilmer
45
also produces an action which prevents liquid from running back from the front end edge
44
to the outer wall surface
46
, and prevents bulking of the liquid fuel particles which are atomized from the front end edge
44
.
With air-blast liquid fuel atomizing nozzles, it is important to make the properties of the spray resulting from the fuel particles which have been atomized symmetrically around the axis of the nozzle. If there are deviations in the fuel concentration in the circumferential direction around the axis of the nozzle, due to differences in the ratio of fuel and air (air-fuel ratio) according to the position around the axis of the nozzle, the flame stability is impaired, producing deviations in the temperature distribution within the combustion chamber, and as a result, high temperature combustion or locally incomplete combustion occurs, giving rise to problems of increased generation of harmful components or incompletely combusted components.
In the atomizing nozzle
30
shown in
FIG. 4
, due to the spiral passages
43
or the liquid passages corresponding thereto being set located apart in the circumferential direction, there is a tendency for the thickness of the liquid film FF to become thick in positions around the circumference which correspond to the spiral passages
43
or the liquid passages, even on the prefilmer
45
. In cases where the number of the spiral passages
43
is low or the axial length of the prefilmer
45
is short, this tendency is particularly pronounced. Easing this problem by making the annular space
37
an extremely narrow annulus could be considered, but in cases which adopt this kind of measure, the liquid fuel cannot be given rotation. Moreover, when attempting to resolve this problem by making the cross-sectional area of the spiral passages
43
smaller and in exchange increasing the number of the spiral passages
43
, another problem occurs of passage blockages developing easily as a result of solid deposits in the liquid fuel.
Furthermore, in times of low fuel flow rates, there is a tendency for the flow rate of fuel passing through the spiral passages
43
in the bottom side to become larger than in the upper side due to pressure differences in the top and bottom of the liquid reservoir
42
resulting from gravitational force, and due to this a problem occurs in which the fuel discharge volume of the atomizing nozzle
30
deviates in the circumferential direction. There are also cases where these kind of deviations can be eased by reducing the cross-sectional area of the spiral passages
43
and by applying adequately high pressure to the fuel in liquid reservoir
42
so that pressure differences which occur through gravitational force can be ignored, but in many cases elevation of the fuel pressure is restrained by problems such the above-mentioned blockages through solid deposits or fuel flow rate turndown ratios (the maximum fuel flow rate of an engine divided by the minimum fuel flow rate).
The strongest controlling factor on the size of the droplets formed by means of atomization is the thickness of the liquid film, and in the development of air-blast liquid atomizing nozzles, efforts have been focused on how to form a thin liquid film which is furthermore uniform around the circumference. If the liquid film becomes thick, even locally, the larger droplets generated there become, and in a case of liquid fuel may be tied to outbreaks of smoke-generation or incomplete combustion. In order to avoid these drawbacks in combustion which are ascribable to deviations in fuel concentration, it is essential to disperse the liquid fuel as uniformly as possible in the circumferential direction around the nozzle axis.
Consequently, in air-blast liquid atomizing nozzles, dispersing the liquid as much as possible unifo
Gorman Darren
Mar Michael
National Aerospace Laboratory of Japan
Westerman Hattori Daniels & Adrian LLP
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