U.S. patent number 3,808,803 [Application Number 05/341,440] was granted by the patent office on 1974-05-07 for anticarbon device for the scroll fuel carburetor.
This patent grant is currently assigned to The United States of America as represented by the Secretary of the Navy. Invention is credited to Enrico Salvi.
United States Patent |
3,808,803 |
Salvi |
May 7, 1974 |
ANTICARBON DEVICE FOR THE SCROLL FUEL CARBURETOR
Abstract
An anticarbon device for a scroll-type carburetor consists of a
frustro-ccal plug mounted on the upstream wall of the spin chamber
at a location along the axis of the core outlet and the primary
vortex. A plurality of passageways formed therethrough permit air
to be introduced into the scroll and directed against those wall
locations where carbon deposits usually form because of the reverse
high temperature gas flow. The plug also retains the high air/fuel
velocities through the swirl vanes for flashback prevention.
Inventors: |
Salvi; Enrico (Salem, MA) |
Assignee: |
The United States of America as
represented by the Secretary of the Navy (Washington,
DC)
|
Family
ID: |
23337583 |
Appl.
No.: |
05/341,440 |
Filed: |
March 15, 1973 |
Current U.S.
Class: |
60/737; 239/404;
431/185; 239/400; 431/183 |
Current CPC
Class: |
F23R
3/14 (20130101); F23D 2209/10 (20130101); F23D
2900/00016 (20130101) |
Current International
Class: |
F23R
3/14 (20060101); F23R 3/04 (20060101); F02c
007/22 () |
Field of
Search: |
;60/39.74R,39.74B
;239/400,403-406 ;261/79 ;431/185,183 |
References Cited
[Referenced By]
U.S. Patent Documents
|
|
|
3605405 |
September 1971 |
Dubell et al. |
|
Primary Examiner: Croyle; Carlton R.
Assistant Examiner: Garrett; Robert E.
Attorney, Agent or Firm: Sciascia; R. S. Shrago; L. I.
Claims
What is claimed is:
1. For use in a scroll-type carburetor of the type having a spin
chamber that includes spaced upstream and downstream planar walls
interconnected by an involute wall, with said downstream wall
having a circular opening that serves as a discharge exit for the
vortical fuel/air mixture, the combination of,
an anticarbon member secured to said upstream wall at a location
corresponding to the central axis of said cirular opening,
said member having a generally frustro-conical body portion which
extends across said spin chamber with the apex thereof terminating
at a point beyond said circular opening,
said member also having a plurality of passageways formed
therethrough which permit air to be injected into said spin
chamber; and
means for deflecting some of said injected air backwardly against
surrounding exterior portions of said upstream wall which are
adjacent said anticarbon member.
2. In an arrangement as defined in claim 1,
wherein said anticarbon member has a central aperture formed
therein whose diameter increases to a maximum at said apex, and
forms a circular edge thereat.
3. In an arrangement as defined in claim 1,
wherein said frustro-conical body portion has a convex surface.
4. For use in a scroll-type carburetor having a spin chamber that
is formed by spaced upstream and downstream planar walls that are
interconnected by an involute wall, with a circular opening formed
in said downstream wall for discharging the vortical fuel/air
mixture into the combustion chamber, the combination of,
a generally frustro-conical member secured to said upstream wall at
a location such that the longitudinal axis of symmetry of said
member coincides with the central axis of said circular
opening,
said member extending across said spin chamber with the apex
thereof terminating at a point beyond said circular opening,
said member also having formed therein a plurality of passageways
which permit air to be injected from outside said spin chamber into
the interior thereof; and
means for deflecting some of said injected air against surrounding
exterior portions of said upstream wall and forwardly along the
surface of said member so as to counteract any recirculation flow
from said combustion chamber back into said spin chamber.
5. In an arrangement as defined in claim 4,
wherein one of said passageways formed in said member is located
along said longitudinal axis of symmetry.
6. In an arrangement as defined in claim 5,
wherein said one passageway increases in size such that the maximum
opening thereof occurs at the apex of said member.
7. In an arrangement as defined in claim 4,
wherein some of said passageways of said plurality are arranged in
a circle.
8. In an arrangement as defined in claim 4,
wherein the outer surface of said member is curved.
Description
The present invention relates generally to scroll fuel carburetors
and, more particularly, to an anticarbon device for such
carburetors which eliminates smoke without reducing the required
flashback margin.
One of the proposed solutions for minimizing air pollution caused
by visible smoke emission from gas turbine engines involves
carbureting the inlet air and delivering the combustible fuel/air
mixture into the primary zone of the combustor as a vortical flow.
The apparatus which achieves thi mode of operation generally
comprises a housing defining a spin chamber that is centrally
disposed about a core outlet. Fuel and air introduced into this
chamber circulate through an array of swirl vanes and emerge as a
vortical discharge flow of air and highly dispersed fuel. A skirt
at the core outlet collects any non-varporized or atomized fuel
that might otheerwise be expelled from the system, and a secondary
array of swirl vanes disposed about this collector develops a
secondary vortical flow into the combustion chamber about the
primary vortex.
Such apparatus has been found to produce an extremely well
vaporized fuel/air mixture which may be efficiently burned in the
combustion chamber with reduced smoke emission. However, under
certain operating conditions, the reduced pressure of the vortex
core causes a reverse or recirculation flow to take place from the
combustion chamber back to the central portion of the spin chamber.
Although this recirculation does contribute to further vaporization
of any liquid fuel from the spin chamber surfaces, this high
temperature gas movement can have undesirable effects on the
performance of the apparatus if it is not counteracted. For
example, carbon deposits may accumulate on the upstream wall
surface of the spin chamber and cause unstable burning conditions
within the combustion chamber. Additionally, the high temperature
gas impinging on this upstream wall may produce premature
structural damage.
One technique that has been proposed to avoid these conditions
involves perforating the upstream wall and sending large amounts of
high velocity air ito the spin chamber to oppose the hot
recirculating gases. I order not to upset the primary vortex and
destroy the basic aero-dynamics of the system, this purge air has a
swirl imparted to it that is in the same direction as the primary
vortex flow.
It has been found that there is still a tendency for a stagnation
zone to occur at the center of the back face of the scroll. Carbon,
consequently, may continue to accumulate on this portion of the
upstream wall.
With the scroll type combustors, flashback may be experienced when
the fluid velocities through the vanes are not sufficiently high.
These velocities have been increased by reducing the scroll-vane
height. But when this is done by, for example, inserting a plug at
the back of the scroll, the richness of the fuel mixture in the
scroll increases and produces smoke.
It is, accordingly, a primary object of the present invention to
provide an anticarbon device for a scroll fuel vaporizer.
Another object of the present invention is to provide an anticarbon
device for a scroll fuel carburetor which minimizes smoking and
retains high vane velocities for flashback prevention.
Briefly, and in somewhat general terms, the above objects are
accomplished according to the present invention by positioning a
plug at the upstream or back face of the scroll at a location which
is along the central axis of the spin chamber so as to be co-axial
with the core outlet and the primary vortex. This member, which has
the general shape of a frustrated cone, extends across the spin
chamber and projects a short distance into the interior of the
skirt. A plurality of circumferential apertures and a central
aperture are provided in the cone thus permitting controllable
amounts of air to be introduced into the scroll and directed
against preselected back wall areas. This air prevents the build up
of carbon deposits on these surfaces and also leans out the very
rich mixture which otherwise occurs in this general region of the
scroll and causes smoking.
The plug also retains the present small scroll-vane height
associated with high fluid velocities through the vanes. This, as
is known in the art, eliminates the possibility of flashback.
Additionally, the surface of the anticarbon device is continuously
scrubbed with the fuel/air mixture, and this constant cleaning
discourages any carbon accumulation on this device.
Other objects, advantages and novel features of the invention will
become apparent from the following detailed description of the
invention when considered in conjunction with the accompanying
drawings wherein:
FIG. 1 is a fragmentary axial cross-sectional view of an exemplary
gas turbine engine combustion apparatus which may utilize the
improved scroll carburetor of the present invention;
FIG. 2 is a cross-sectional view of a scroll showing one
modification of the anticarbon device mounted in place;
FIG. 3 is a front-view showing the locations of the various
apertures; and
FIG. 4 schematically illustrates another configuration of the
anticarbon plug.
Referring now to the drawings, FIG. 1 schematically illustrates the
general cooperation between a gas turbine engine and a scroll fuel
carburetor of the type which may utilize the present invention. The
details of this system are shown in U. S. Pat. No. 3,605,405 of
Sept. 20, 1971, and reference may be had to this patent for a
complete description of the operation and performance of the
particular scroll carburetor shown. It would be pointed out,
however, that carburetor 34 produces both a primary vortical flow
40 and a secondary vortical flow 67. However, the secondary flow
need not be present as far as the operating principle of the
present invention is concerned.
Referring now to FIG. 2, it will be seen that housing 35 of
carburetor 34 is formed by an involute outer wall 48 and a pair of
planar spaced upstream and downstream end walls 50 and 52,
respectively. The air/fuel mixture introduced into end opening 55
thus experiences a circular motion of ever-decreasing radius in
spin chamber 46, and, this, together with the action of swirl vanes
such as 31, 32 within this chamber, produces the primary vortical
flow 40.
The reduced pressure condition at the vortex core 56 causes the
reverse flow, previously mentioned, to be established from
combustion chamber 14 back into spin chamber 46, as shown by arrow
82. While this recirculation is beneficial in that it enhances
vaporization of the liquid fuel from the spin chamber surfaces and
any atomized fuel droplets carried by the air intake, it does,
unfortunately, have detrimental effects if it is allowed to impinge
upon the upstream end wall 50 of the spin chamber. For example,
this high temperature may overheat this wall surface and cause
structural deformation or damage. Additionally, it may cause the
accumulation of carbon deposits on the interior wall surfaces and
produces unpredictable burning conditions in the combustion chamber
14.
To eliminate this problem, as shown in FIG. 2, an anticarbon device
80 is mounted or otherwise secured to end wall 50 at a location
which lies along the central axis of the core outlet and the
primary vortex. This apparatus has the general shape of a truncated
cone with, in this particular case, its outer surface 51
concave.
A plurality of apertures such as 90 and 91, better shown in FIG. 3,
are cut through this member at a circle of locations adjacent its
rim portion. Also, a central aperture 92 of progressingly greater
diameter is formed therein so as to provide a circular edge 93 at
the apex.
The dimensions of plug 80 are such that its conical body portion
extends completely across the spin chamber, with its apex portion
projecting a short distance into the interior of skirt 89.
Cooperating with plug 80 is a spaced deflector 94 which has a
central opening 96 formed therein to accommodate the anticarbon
plug in a concentric manner. Deflector 94 includes a ring portion
disposed within the spin chamber so as to confront the circle of
air inlet apertures. A plurality of integrally form-supporting tabs
project from this ring portion and are secured to the outside
surface of the back wall. Alternatively, these tabs may be directly
attached near the outer rim portion of the conical plug 80 so as to
permit the insertion of the complete apparatus, that is, the plug
and the deflector into the scroll as a unitary device. In this
case, any suitable mounting arrangement may be employed to position
this device in place on the back wall of the scroll.
In any event, the purpose of this deflector is to direct the air,
which is injected into the interior of the scroll via the circle of
apertures, such as 90 and 91, upstream against end wall 50 of the
scroll. This air flow prevents the accumulation of any carbon on
the swept surrounding wall surface. Some of this air is also
admitted as a film around the concave surface of the truncated
cone, and, when it leaves the apex, it does not interfere with the
aero-dynamics of the primary vortical flow.
The circular trailing edge 93 serves as a means from which any fuel
can shear off uniformly and concentrically to the scroll exit.
Central aperture 92 is included to insure that all possible
stagnation zones are eliminated.
In the operation of the apertures of FIG. 2, the fuel and air
mixture passes through the various swirl vanes, such as 31 and 32,
and the primary vortical flow is established in the usual manner.
The additional air introduced through the circle of apertures in
the anticarbon device, as mentioned hereinbefore, splashes onto the
upstream surface of this scroll and prevents carbon formation
thereon. Some of this air is also admitted as a film around the
downstream surface of the truncated cone, and, when it is
discharged therefrom, counteracts the recirculation flow. Further
contributing to the counteraction of this flow is the air
introduced at the central opening 92.
The fuel/air mixture emanating from the swirl vanes sstrikes the
concave surface 81 of plug 80 and, thus, this portion of the
apparatus is continuously scrubbed. This constant cleaning prevents
any carbon accumulation at this site.
It will also be pointed out that the additional air introduced into
this system via the various apertures in plug 80 leans out the
otherwise very rich mixture which sometimes is present in this
region and is responsible for some of the smoking.
FIG. 4 shows an alternative anticarbon configuration. Here the
surface is convex rather than concave and the central aperture has
a constant diameter.
* * * * *