U.S. patent number 3,747,588 [Application Number 05/151,881] was granted by the patent office on 1973-07-24 for oil burning submerged combustion units.
This patent grant is currently assigned to C. & W. Walker Limited. Invention is credited to Christopher John Booth.
United States Patent |
3,747,588 |
Booth |
July 24, 1973 |
OIL BURNING SUBMERGED COMBUSTION UNITS
Abstract
In an oil burning combustion unit a mixture of oil and
combustion air is directed downwards into a combustion chamber
submerged in a liquid, and having a step at which its cross-section
increases in a downward direction. It is made from a single
thickness of metal with its inner surface exposed to the flame and
its outer surface immersed in the liquid.
Inventors: |
Booth; Christopher John
(Chester, EN) |
Assignee: |
C. & W. Walker Limited
(Donnington, near Wellington, Shropshire, GB)
|
Family
ID: |
22540638 |
Appl.
No.: |
05/151,881 |
Filed: |
June 10, 1971 |
Current U.S.
Class: |
126/360.2 |
Current CPC
Class: |
F22B
1/26 (20130101); F23C 3/004 (20130101) |
Current International
Class: |
F23C
3/00 (20060101); F22B 1/00 (20060101); F22B
1/26 (20060101); F24h 001/20 () |
Field of
Search: |
;60/39.55,39.57
;126/360,36A,350 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Sprague; Kenneth W.
Claims
What I claim as our invention and desire to secure by Letters
Patent is:
1. An oil burning combustion unit having an oil atomizer operable
to direct atomized oil and combustion air downwardly into a
combustion chamber;
said combustion chamber having an opening in the lower end thereof,
being substantially circular in horizontal cross-section and
substantially submerged in a liquid such as water in operation;
said combustion chamber further having a stepped construction where
its horizontal cross-section increases suddenly in a downward
direction, the enlarged portion of said combustion chamber below
the step having a length between 1/2 and 11/2 times the diameter
thereof;
said combustion chamber further having an upper diverging portion
whose diameter increases progressively downwardly, a middle
substantially cylindrical portion having a substantially constant
diameter substantially equal to that of the lower end of said upper
diverging portion and extending from same to the step, the lower
cylindrical portion of said combustion chamber from said step
downwardly to the open end thereof having substantially constant
diameter;
the opening at the lower end of said combustion chamber being of
substantially annular form and defined by a substantially circular
plate spaced downwardly from the otherwise substantially circular
open lower end of the combustion chamber wall below the step
therein.
2. A unit as in claim 1 including a pilot gas burner provided in
conjunction with said unit and mounted in substantial axial
alignment with the combustion chamber of said unit, said pilot gas
burner having a port connecting the combustion chamber of the pilot
gas burner to the middle substantially cylindrical portion of said
unit combustion chamber above the step therein, whereby to ignite
the flame in the unit combustion chamber.
3. A unit as in claim 1 wherein the unit combustion chamber has an
ultraviolet flame detector and means associated therewith operative
to shut off the supply of oil to the oil atomizer should the flame
be extinguished in the unit combustion chamber.
4. A unit as in claim 1 wherein the proportions of the parts of the
unit combustion chamber, taking the diameter of the opening at the
lower end thereof as 1.0, are: diameter of the unit combustion
chamber above the step is 0.67 and the diameter of the upper end of
the unit combustion chamber upper portion is 0.33, the height of
the lower portion of the unit combustion chamber below the step is
1.0, the height of the middle portion of the combustion chamber
above the step is 1.0 and the height of the upper portion of the
unit combustion chamber is 0.64.
5. An oil burning combustion unit having an oil atomizer operable
to direct atomized oil and combustion air downwardly into a
combustion chamber;
said combustion chamber having an opening in the lower end thereof,
being substantially circular in horizontal cross-section and in
operation substantially submerged in a liquid such as water;
said combustion chamber having an uppermost diverging portion whose
diameter increases progressively downwardly, a middle cylindrical
portion of a substantially constant diameter equal to that of the
lower end of the uppermost portion and extending from the latter to
a step, and a lower cylindrical portion of increased diameter
extending downwardly from said step to the open end;
the wall of the unit combustion chamber above and below said step
formed of a single thickness of metal whereby the inner surface
thereof is exposed to the flame and the outer surface thereof is in
direct contact with said liquid in operation.
6. A unit as in claim 5 wherein the lowermost large diameter
portion of said unit combustion chamber, below the step, has a
length between 1/2 and 11/2 times its diameter.
7. A unit as in claim 5 wherein the outlet opening from the burner
to the surrounding fluid in operation is defined in annular form by
a substantially circular plate downwardly spaced from the otherwise
open circular lower end of the unit combustion chamber wall.
8. An oil burning combustion unit having an oil atomizer operable
to direct atomized oil and combustion air downwardly into a
combustion chamber;
said combustion chamber having a discharge opening at the lower end
thereof, being substantially circular in horizontal cross-section
throughout the substantial height thereof and substantially
submerged in a liquid such as water during operation;
said combustion chamber further of substantial two part
construction vertically separated by a step whereat the diameter
thereof increases suddenly downwardly;
the enlarged portion of said unit combustion chamber, below the
step therein, having a length between 1/2 and 11/2 times the
diameter thereof;
the wall of the unit combustion chamber and both above and below
the step formed of a single thickness of metal whereby the inner
surface thereof is exposed to the flame, the outer surface thereof
in direct contact with the liquid in which it is submerged in
operation.
9. An oil burning combustion unit having an oil atomizer operable
to direct atomized oil and combustion air downwardly into a
combustion chamber;
said combustion chamber having a discharge opening in the lower end
thereof, having the substantial same configuration ro shape in or
entire vertical height thereof in horizontal section therethrough
and substantially submerged in a liquid such as water in operation
thereof;
said combustion chamber further of a step construction where its
cross-sectional dimension increases suddenly in a downward
direction, the enlarged portion oF said combustion chamber below
the step having a length between 1/2 and 11/2 times the diameter
thereof;
the wall of said chamber both above and below the said step formed
of a single thickness of metal whereby the inner surface thereof is
exposed to the flame and the outer surface thereof is in direct
contact with the liquid in which same is submerged in
operation.
10. An oil burning combustion unit having an oil atomizer operable
to direct atomized oil and combustion air downwardly into a
combustion chamber;
said combustion chamber having a discharge opening in the lower end
thereof, of the same configuration or shape in horizontal
cross-section throughout the vertical height thereof and
substantially submerged in a liquid such as water in operation;
said combustion chamber having an uppermost diverging portion whose
diameter increases progressively downwardly, a middle portion of a
substantially constant diameter (or transverse dimension) equal to
that of the lower end of said uppermost portion and extending
downwardly therefrom to a step, at the step the cross-sectional
dimension of the combustion chamber increasing suddenly in a
downward direction and a lowermost portion of substantially
constant diameter or transverse dimension extending downwardly from
the step to the open end thereof;
the wall of said chamber both above and below the said step formed
of a single thickness of metal whereby the inner surface thereof is
exposed to the flame and the outer surface thereof is in direct
contact with the liquid in which same is submerged in
operation.
11. An oil burning combustion unit including an oil atomizer for
directing atomized oil and combustion air downwards into a
combustion chamber with an opening at the bottom and submerged in a
liquid such as water, in which the combustion chamber has in it a
step at which its cross-section increases suddenly in a downward
direction, the wall of the chamber both above and below the step
being formed of a single thickness of metal with its inner surface
exposed to the flame and its outer surface immersed in the liquid,
the combustion chamber is of circular section and the enlarged
portion of it, below the step, has a length between 1/2 and 11/2
times its diameter, the combustion chamber also having an upper
diverging portion whose diameter increases progressively downwards,
a middle cylindrical portion of a substantially constant diameter
equal to that of the lower end of the upper portion extending from
it to the step, and a lower cylindrical portion of substantially
constant diameter extending down from the step to the open end.
12. An oil burning combustion unit including an oil atomizer for
directing atomized oil and combustion air downwards into a
combustion chamber with an opening at the bottom and submerged in a
liquid such as water, in which the combustion chamber has in it a
step at which its cross-section increases suddenly in a downward
direction, the wall of the chamber both above and below the step
being formed of a single thickness of metal with its inner surface
exposed to the flame and its outer surface immersed in the liquid,
the combustion chamber is of circular section, the enlarged portion
of it, below the step, has a length between 1/2 and 11/2 times its
diameter, and the opening at the bottom of the combustion chamber
is of annular form provided by a plate spaced from the otherwise
open lower end of the combustion chamber wall.
13. An oil burning combustion unit including an oil atomizer for
directing atomized oil and combustion air downwards into a
combustion chamber with an opening at the bottom and submerged in a
liquid such as water, in which the combustion chamber has in it a
step at which its cross-section increases suddenly in a downward
direction, the wall of the chamber both above and below the step
being formed of a single thickness of metal with its inner surface
exposed to the flame and its outer surface immersed in the liquid,
the combustion chamber is of circular section, the enlarged portion
of it, below the step, has a length between 1/2 and 11/2 times its
diameter, and a pilot gas burner, mounted alongside and having a
port connecting it to the combustion chamber, which ignites the
flame.
14. An oil burning combustion unit including an oil atomizer for
directing atomized oil and combustion air downwards into a
combustion chamber with an opening at the bottom and submerged in a
liquid such as water, in which the combustion chamber has in it a
step at which its cross-section increases suddenly in a downward
direction, the wall of the chamber both above and below the step
being formed of a single thickness of metal with its inner surface
exposed to the flame and its outer surface immersed in the liquid,
the combustion chamber is of circular section, the enlarged portion
of it, below the step, has a length between 1/2 and 11/2 times its
diameter, and the combustion chamber provided with an ultraviolet
flame detector which shuts off the supply of oil if the flame is
extinguished.
15. An oil burning combustion unit including an oil atomizer for
directing atomized oil and combustion air downwards into a
combustion chamber with an opening at the bottom and submerged in a
liquid such as water, in which the combustion chamber has in it a
step at which its cross-section increases suddenly in a downward
direction, the wall of the chamber both above and below the steo
being formed of a single thickness of metal with its inner surface
exposed to the flame and its outer surface immersed in the liquid,
and the combustion chamber has an upper diverging portion whose
diameter increases progressively downwards, middle cylindrical
portion of a substantially constant diameter equal to that of the
lower end of the upper portion extending from it to the step, and a
lower cylindrical portion of substantially constant diameter
extending down from the step to the open end.
16. An oil burning combustion unit including an oil atomizer for
directing atomized oil and combustion air downwards into a
combustion chamber with an opening at the bottom and submerged in a
liquid such as water, in which the combustion chamber has in it a
step at which its cross-section increases suddenly in a downward
direction, the wall of the chamber both above and below the step
being formed of a single thickness of metal with its inner surface
exposed to the flame and its outer surface immersed in the liquid,
and the opening at the bottom of the combustion chamber is of
annular form provided by a plate spaced from the otherwise open
lower end of the combustion chamber wall.
17. An oil burning combustion unit including an oil atomizer for
directing atomized oil and combustion air downwards into a
combustion chamber with an opening at the bottom and submerged in a
liquid such as water, in which the combustion chamber has in it a
step at which its cross-section increases suddenly in a downward
direction, the wall of the chamber both above and below the step
being formed of a single thickness of metal with its inner surface
exposed to the flame and its outer surface immersed in the liquid,
and a pilot gas burner, mounted alongside and having a port
connecting it to the combustion chamber, which ignites the
flame.
18. An oil burning combustion unit including an oil atomizer for
chamber atomized oil and combustion air downwards into a combustion
,hamber with an opening at the bottom and submerged in a liquid
such as water, in which the combustion chamber has in it a step at
which its cross-section increases suddenly in a downward direction,
the wall of the chamber both above and below the step being formed
of a single thickness of metal with its inner surface exposed to
the flame and its outer surface immersed in the liquid, and the
combustion chamber provided with an ultraviolet flame detector
which shuts off the supply of oil if the flame is extinguished.
Description
This invention relates to submerged combustion units, and is
concerned with the provision of a submerged combustion unit capable
fo satisfactorily burning oil.
According to the present invention an oil burning combustion unit
includes an oil atomizer for directing atomized oil and combustion
air downwards into a combustion chamber with an opening at the
bottom and submerged in a liquid such as water, in which the
combustion chamber has in it a step at which its cross-section
increases suddenly in a downward direction, the wall of the chamber
both above and below the step being formed of a single thickness of
metal with its inner surface exposed to the flame and its outer
surface immersed in the liquid.
Preferably the combustion chamber is of circular section and the
enlarged portion of it, below the step, has a length between half
and one and a half times its diameter.
Thus in one form of the invention the combustion chamber has an
upper diverging portion whose diameter increases progressively
downwards, a middle cylindrical portion of a substantially constant
diameter equal to that of the lower end of the upper portion
extending from its to the step, and a lower cylindrical portion of
substantially constant diameter extending down from the step of the
open end.
For heating a liquid submerged combustion has considerable
advantages in that with a combustion chamber below the surface of
the liquid, and therefore in intimate contact with it, and with the
exhaust gases passing from the combustion chamber directly into the
liquid in which the burner is submerged, efficient transfer of heat
is obtained in a simple manner. Moreover it does not require a
refractory lining, resulting in a saving in capital outlay, and
indeed could not employ one since the hot refractory material would
be shattered when flooded with liquid on shutting off the
burner.
Although oil is a cheaper fuel than gas, therm for therm, it has
hitherto been customery to employ gas because of its ease or
ignition and stability of flame, and difficulty has been
experienced in obtaining satisfactory results with oil. Thus
whereas a gas flame is a continuous medium and burns as a single
continuous flame, oil is atomized in its combustion air and is
therefore a mist of tiny droplets each of which burns and each of
which forms a very small flame within the combustion zone, nd each
of which has to be ignited. These droplets burn at their surfaces
where they are evaporating and the oil and air are truly mixed at a
molecular scale. Thus the function of an oil bruner is first to
break up the oil into small droplets, secondly to evaporate these
droplets and thirdly to burn the evaporated droplets as a gas so as
to evolve heat part of which serves to evaporate incoming
droplets.
Considerable difficulty is experienced in obtaining a reliable and
stable flame with oil fuel. In a conventional combustion chamber
the incoming oil drops are vapourized by heat radiated from the
walls of the combustion chamber which are incandescent. This
necessitates the employment of a refractory lining which adds
substantially to the cost and also reduces the transfer of heat. It
is believed that the step in a combustion chamber in accordance
with the present invention introduces a degree of turbulence which
results in a satisfactory transfer of heat from the burning
vapourized oil to the incoming oil droplets, and produces a
reliable and stable flame.
The present invention may be put into practice in various ways but
one specific embodiment will now be described by way of example
with reference to the accompanying drawing which is a somewhat
diagrammatic elevation, partly in section, of an oil-burning
submerged combustion unit for heating water for purposes such as
swimming baths.
The unit comprises an oil-burning atomizer 10 of conventional type
directed downwardly into a combustion chamber 14. The combustion
chamber 14 is formed of a single thickness of sheet steel and
comprises an upper frusto-conical portion 15 diverging downwardly
from the oil atomizer 10, a cylindrical middle portion 16 of the
same diameter as the lower larger end of the upper portion 15, and
a horizontal step 17 connecting the lower end of the cylindrical
portion to the upper end of a lower cylindrical portion 18 of
larger diameter than the middle portion 16. A flat circular plate
19 is connected to, and spaced from, the lower end of the lower
cylindrical portion 18 by four straps 20.
It is found that there is a critical minimum length for the lower
portion 18 of the combustion chamber 14, of which the ratio of
length to diameter should lie between 1.5 and 0.5. Thus in the
specific embodiment the proportions of the parts are roughly as
follows, taking the diameter of the lower open end of the lower
portion 18 as one. On this basis the height of the upper portion
15, the middle portion 16 and the lower portion 18 are each 0.64,
1.0 and 1.0 respectively. The diameter of the middle portion 16 and
of the lower end of the upper portion 15 is 0.67 and the diameter
of the upper end of the upper portion 15 is about 0.33.
The combustion chamber is secured to a flat plate 25 and the water
level may vary between the limits indicated by the lines 26 and 27,
which are respectively, on the basis of the above proportions, 0.1
below and 1.0 above the flat plate 25.
With these proportions it is found that a stable flame can be
produced with the water in contact with the outer surface of the
combustion chamber 14 and the flame in contact with its inner
surface. Due to the water-cooling the wall is not destroyed and at
the same time efficient transfer of heat occurs. COnveniently the
oil burner is provided with a pilot gas burner 30 to ignite it.
This comprises a smaller cylindrical combustion chamber 31 mounted
vertically alongside the oil-burning unit having at the top an
inlet tube 32, through which a mixture of gas and air is admitted
to the gas burner, a small opening 33 in the bottom and a lateral
port 34 opening into the combustion chamber 14 of the oil-burning
unit. A flash tube 37 extends from the gas combustion chamber 31 to
a point above the surface of the water and is provided with a
sparking plug 38 and venting valve 39.
The oil combustion chamber 14 and the gas combustion chamber 31 may
be provided with ultra-violet flame detectors, 42 and 43
respectively, to automatically shut off the supplies of oil and gas
if the flames are extinguished.
Thus to start the oil burner air from blowers 50 and 51 is admitted
to the combustion chambers 14 and 31 to completely purge the
system. Gas is then admitted from a supply 52 to the gas combustion
chamber 31, by way of a venturi device 53 and the inlet tube 32, in
combustible proportions with air and the venting valve 39 opened to
allow some gas to flow up the flash tube 37 and be ignited, by the
sparking plug 38, to start the gas flame. The rate of flow of the
inflammable mixture up the flame tube is governed by a restriction
40, which may be incorporated in the valve 39, so that on ignition
the flame will flash back into the gas combustion chamber 31. The
oil is then turned on and the gas flame, which extends through the
port 34 into the oil combustion chamber 14, ignites it. If desired
the the gas flame may now be turned off provided that either a good
seal is made at the top of the gas burner or air is left flowing
through this part of the system.
The hole 33 in the base of the gas burner 30 is desirable to avoid
detonation on ignition of the gas and consequent damage to air
compression equipment.
The preferred gas is propane but other gaseous fuels preferably
with a calorific value above 350 BTU/ft.sup.3 may be used.
* * * * *