The present invention relates to direct-fired steam generator
including a steam generator body defining a main combustion chamber having an outlet
end through which hot gases are exhausted from the combustion chamber, a mixing
chamber having an inlet end coupled for receiving the hot gases from the combustion
chamber, and a water injection arrangement for injecting water into a zone at said
outlet end for being contacted by said hot gases and changed to steam.
A direct-fired steam generator usually comprises a system
formed from three parts, namely, a burner head, a combustion chamber, and a straight,
or elbow-forming, tubular mixing chamber. Except for the mixing chamber, U.S. Patent
No. 4,211,071 discloses such a steam generator. Considerable heat is generated in
the burner head, combustion chamber and mixing chamber.
While the patented structure includes a water jacket for
cooling the length of the combustion chamber, the bottom wall, which contains a
centrally located exit outlet for conveying steam and hot combustion gases, is not
adequately cooled. A solution to this cooling problem is disclosed in U.S. Patent
No. 3,980,137, wherein a bottom combustion chamber wall is made of upper and lower
sections constructed for being clamped together to form an annular passage for receiving
cooling water. However, this solution is somewhat costly.
Both of the aforementioned patented structures introduce
feed water into the combustion chamber by having it enter from the top of the water
jacket through a small gap provided between the top wall of the combustion chamber
and the inner wall of the water jacket. This feed water then runs down the inner
surface of the inner wall. This water flow serves the purposes of providing secondary
cooling to the combustion chamber, and of introducing water into the hot products
of combustion so that it changes to steam while preventing water from coming in
direct contact with the flame, such direct contact being undesirable since it would
negatively affect combustion. While this may be a suitable way to introduce feed
water into a static combustion chamber, it has been found that in a mobile application,
such as when the steam generator is being used to generate steam to re-hydrate crop
just before baling, for example, the terrain traversed by the generator carrying
vehicle may result in the combustion chamber becoming tilted, which causes an uneven
flow of feed water along the inner wall of the combustion chamber. The result of
uneven flow is that a portion of the water prematurely flashed to steam in the combustion
chamber. As water flashes to steam, the water leaves behind solid particles (mineral
deposits) on the combustion chamber walls and the steam disrupts the flame. The
mineral deposits build up over time and will cause water flow and heat transfer
issues resulting in unacceptable steam generator system performance. In addition,
when water flow is disrupted, hot spots can occur in some designs on the lower parts
of the combustion chamber which are not cooled by the water-jacket. Yet another
disadvantage of this design is the abrupt transition at the bottom wall of the combustion
chamber to go from the diameter of the combustion chamber to the smaller diameter
of the exit conduit. This abruptness causes turbulence which requires an increase
in burner blower power to move the combined steam and combustion gases through the
system. Available power for implements can be very limited, especially in older
machines; therefore, a design with excessive power requirements has little practicality
for use in some mobile applications.
The aforementioned drawbacks associated with the known
design has been solved in part by another known system wherein the feed water is
injected as a fine mist or spray into the bottom zone of the combustion chamber
at the tip of the flame, but the problem remains that the flat bottom wall of the
combustion chamber still becomes too hot due to the fact that hot combustion gases
impact the wall and must abruptly move to the middle of it before exiting. In this
known steam generator layout, the bottom of the combustion chamber and an end of
an exit conduit were each provided with a flange and these flanges were clamped
and sealed to opposite faces of a water injection ring penetrated by a radially
extending feed water pipe terminating at a discharge nozzle located centrally within
the ring so as to meter water into a zone at the bottom of the combustion chamber.
However, the flanges were found to reach an unacceptable temperature in the neighborhood
of 390° C (735° F).
The problem to be solved then is to find a way to reduce
the operating temperature of the exterior surfaces of the combustion chamber and
exit conduit, located in the region of the bottom of the combustion chamber, to
an acceptable temperature.
According to the present invention, there is provided an
improved steam generator wherein the exterior surfaces of the components making
up the combustion chamber and mixing chamber exhibit acceptable exterior working
An object of the invention is to shape the combustion chamber,
so as to eliminate the bottom wall.
A further object in conjunction with that just mentioned
is to route the feed or process water, i.e., that water which is being changed to
steam, in such a way as to cool the flanges used to connect the combustion chamber
to the mixing chamber.
The above objects are achieved by providing the combustion
chamber with a conical, lower wall section that gradually reduces the interior diameter
of the combustion chamber to that of the interior diameter of the exit conduit,
thereby obviating the need for a bottom wall, and by providing a flange joint designed
for injecting water into the lower region of the combustion chamber while being
cooled by the water before it is injected.
According to the invention, the flange joint design includes
a spacer ring located between the flanges in concentric spaced relationship to a
sealing gasket so as to form a water passage between the gasket and spacer ring.
In one embodiment, the spacer ring has a thickness approximately the same as that
of the gasket and is provided with spaced ends so as to permit water to flow into
the zone between the combustion chamber and the mixing chamber. In another embodiment,
the spacer is made so as to have a thickness somewhat less than that of the gasket,
thereby permitting water to be metered in the gap left between the spacer and the
flanges. In yet another embodiment, the gasket is replaced by two spacers having
cooperating profiles which result in the water being channeled about the flange
and into the zone between the combustion and mixing chambers.
Instead of using spacer rings, grooves could be formed
in one or the other or both of the flange faces so as to channel the water about
the faces and into the zone between the combustion chamber and the mixing chamber.
It would be possible to provide a direct-fired steam generator
comprising a steam generator body defining a main combustion chamber having an outlet
end through which hot gases are exhausted from the combustion chamber, and an exit
conduit having an inlet end coupled for receiving the hot gases from the combustion
chamber. Said generator body may have a cylindrical cross section and including
a conical exit end section tapering gradually inwardly to said outlet end; and said
inlet of said exit conduit having a diameter equal to that of said outlet end, whereby
said conical exit end section facilitates smooth flow of said hot gases to said
That conical exit end section of said generator body may
be provided with a first mounting flange surrounding said outlet; and said exit
conduit being provided with a second mounting flange surrounding said inlet; said
first and second flanges being secured together to form a flange joint coupling
said steam generator body to said exit conduit and surrounding a zone at a lower
end of said generator body; a water injection port being provided in one of said
flanges; and a water passage being defined between said flanges in a location in
fluid communication with said water injection port and extending substantially completely
about said zone; and at least one injection passage coupling said water passage
to said zone for causing water to be metered into said zone for being changed to
steam when contacted by said hot gases.
- FIG. 1
- is a schematic sectional view showing the steam producing components of a direct-fired
steam generator constructed in accordance with the principles of the present invention.
- FIG. 2
- is a perspective view showing the flange joint formed between the exhaust end
of the combustion chamber and the exit conduit forming the tubular mixing chamber
of the direct-fired steam generator.
- FIG. 3
- is a perspective view showing the combustion chamber with a flange gasket and
spacer plate located against the mounting flange at the exhaust end of the combustion
- FIG. 4
- is a perspective view like FIG. 3 but showing a spacer plate having a different
shape than that shown in FIG. 3.
- FIG. 5
- is a perspective view of the combustion chamber showing a plate having a first
pattern of openings fixed to the mounting flange used for securing the combustion
chamber to the mixing chamber.
- FIG. 6
- is a perspective view of the mixing chamber showing a plate having a second
pattern of openings fixed to the mounting flange used for securing the mixing chamber
to the combustion chamber.
- FIG. 7
- is a view showing the plates illustrated in FIGS. 5 and 6 mounted together to
form a path for carrying water about the mounting flanges of the combustion and
mixing chambers and for directing the water into the zone between the chambers.
- FIG. 8
- is a view like FIG. 3, but replacing the spacer plate with a raised C-shaped
surface formed integrally with the flange.
Referring now to FIG. 1, there is shown a portion of a
direct-fired steam generator 10 including a steam generator body 12 having a relatively
long cylindrical inlet section 14 to which a cylindrical burner head 16 is coupled,
and having a relatively short conical outlet section 18. An elbow or inlet end 20
is coupled between the outlet section 18 of the body 12 and a tubular static mixer
22 containing mixing fins or baffles 24 having a purpose explained in more detail
The burner head 16 includes a pilot burner tube 26 located
such that it communicates with a lower region of the burner head 16. An igniter
(not shown) is mounted so as to terminate within a lower region of the pilot burner
tube 26. The igniter may be a spark plug or other type of sparking device, which
operates to selectively ignite a fuel/air mixture selectively metered into an upper
end of the pilot burner tube 26. When this mixture is ignited, it in turn acts to
ignite a fuel/air mixture metered into an upper end of the burner head 16, with
this resulting in a main flame being created in a combustion chamber 28 defined
by the generator body 12. Steam is created by injecting water, in a manner described
below, into hot combustion gases at a zone 30 where the small or exhaust end of
the combustion chamber 28 joins an entrance of a mixing chamber 32 defined by the
elbow 20 and the static mixer 22. It can be seen that the inside diameter of the
conical outlet section 18 of the steam generator body 12 gradually tapers to an
exit end having a diameter equal to the inside diameter of the elbow 20. Therefore,
no bottom wall is present at the bottom of the steam generator body 12 to impede
the flow of combustion gases, with the tapered shape of lower end of the combustion
chamber 28 promoting an increase in combustion gas velocity without requiring excessive
burner blower power.
It is to be noted that each of the generator body 12, the
burner head 16 and the elbow 20 are constructed with double walls so as to form
respective water jackets which are interconnected to each other by connecting lines
(not shown) and are connected to a pressurized source of process water, delivered
by a water pump (not shown), for example, so that these jacketed components are
cooled so as to be maintained within an acceptable operating temperature range.
Referring now also to FIG. 2, it can be seen that the conical
outlet section 18 of the steam generator body 12 is provided with a mounting flange
34 and the elbow 20 is provided with a similar mounting flange 36, the flanges 34
and 36 being clamped together in sandwiching relationship to an annular flat gasket
38 by a plurality of bolts 39 inserted through aligned holes in the flanges 34 and
36. A water injection port 40 is provided at the twelve o'clock position in the
mounting flange 36. However, the port 40 could just as well be provided in the mounting
Up to this point, except for the water injection port 40,
the described structure of the direct-fired steam generator 10 is conventional.
What follows is the novel structure designed for effecting cooling of the flanges
34 and 36.
Specifically, with reference to FIG. 3, it can be seen
that a C-shaped spacer plate 42 is located against the mounting flange 34 of the
steam generator housing 12 in concentric relationship to the gasket 38, with a gap
44 defined between opposite ends of the plate 42 being disposed at the six o'clock
position. The spacer plate 42 has a thickness which is approximately equal to that
of the gasket 38 when the latter has been compressed between the flanges 34 and
36. The spacer plate 42 has an outside diameter spaced from an inner diameter of
the gasket 38 so as to define an annular recess or channel 46, which, when covered
by the flange 36 of the elbow 20, cooperates with the flange 30 to define a passage
through which water may flow, from the water injection port 40 into the zone 30
at the exhaust end of the combustion chamber 24 by way of the gap 44 so as to be
contacted by hot exhaust gases and changed to steam, with this contact with hot
exhaust gases being enhanced by the vanes 24 of the static mixer 22. According to
the disposition of the generator body 12, it may be desirable to place the injection
port 44 and/or the gap 44 at different locations so as to obtain the most effective
water flow for cooling the flanges 34 and 36.
It is to be noted that a variant of the spacer plate 42
may be provided wherein the thickness of the plate 42 is somewhat less than that
of the gasket 38. In this case, an annular recess is still formed for permitting
water to flow so as to contact confronting, annular regions of the faces of the
flanges 34 and 36. However, since the spacer plate 42 has a thickness less than
that of the gasket 38, water may enter the zone 30 by flowing radially across the
spacer plate 42. Thus, if desired, the spacer plate 42 may be constructed as a complete
ring where the gap 44 is eliminated.
Referring now to FIG. 4, a spacer plate 42' is shown which
differs from the previously described spacer plate 42 in that the spacer plate 42'
is oriented such that the gap 44 is located at approximately the one o'clock position
so as to be rightward of the water injection port 40. Further, a radial projecting
bridge section 48 is joined to one end of the spacer plate 42 so as to span the
recess 46 at a location rightward of where water is injected into the passage defined
in part by the recess 46 so that the injected water is forced to flow counterclockwise
until it reaches the gap 44.
Referring now to FIGS. 5 - 7, there is shown another embodiment
wherein two circular spacer plates 50 and 52 (see FIG. 7) are used to define a path
for water to flow from the injection port 40 into the zone 30 containing hot exhaust
gases. Specifically, the spacer plate 50 (FIG. 5) has an outer diameter equal to
the inner diameter of the flange gasket 38 and is shown positioned within the gasket
38 and against the flange 34 of the steam generator body 12. The spacer plate 50
has a thickness approximately equal to half that of the flange gasket 38. The spacer
plate 50 is provided with seven identical openings 54 which are spaced 45°
from each other about the center of the plate 50, and which are separated by identical
webs or spokes 56, except at a region centered approximately about a ten o'clock
position wherein a web or spoke 58 having a size equal to two of the webs 56 plus
one of the openings 54 is provided. The web 58 is positioned so that it is in confronting
relationship to the water injection port 40 located in the flange 36 of the elbow
In FIG. 6, the second circular spacer plate 52, which has
the same outside diameter as does the spacer plate 50, is shown positioned against
the flange 36 of the elbow 20. The spacer plate 52 contains seven identical openings
62 which are spaced 45° f rom each other and sized like the openings 54 of
the spacer plate 50, with the openings 62 being bordered by radially extending webs
or spokes 64. When installed (see FIG. 7), the spacer plate 52 is indexed 45°
relative to the spacer plate 50 so that the webs 56 of the spacer plate 50 are disposed
centrally across the openings 62 of the spacer plate 52, and so that the webs 64
of the spacer plate 52 are disposed centrally across the openings 54 of the spacer
plate 50. In the region next to the water injection port 40, the spacer plate 52
is provided with an opening 66 sized slightly larger than the other openings 62,
by an amount about half the size of the webs 64, and having a radially inner corner
coupled to a passage 68 that extends radially to an inner diameter of the plate
52. A web 70 bordering the side of the passage next to the passage 68 is about half
the size of the webs 64.
Like the spacer plate 50, the spacer plate 52 has a thickness
about half that of the flange gasket 38 so that when the gasket 38 and the plates
50 and 52, as shown in FIG. 7, are clamped between the flanges 34 and 36, a water
path is defined which permits water to flow clockwise from the injection port 40
over the portion of the web 58 that is rightward of the web 70. From there, water
flows alternately under webs 64 of the plate 52 and over webs 56 of the plate 50,
and finally exits through the radial passage 68. It is to be understood that the
particular hole pattern provided in the spacer plates 50 and 62 is only exemplary
and that a large variety of patterns could be used that would result in effective
cooling of the flanges 34 and 36.
Referring now to FIG. 8, a further embodiment is shown
wherein a flange 72 is provided at the end of the steam generator body 12 which
differs from the previously described flange 34 in that an outer annular portion
74 of the flange 72 is made of a lesser thickness than the remainder of the flange
so as to define a seat for receiving the flange gasket 38. Spaced radially inward
of the flange gasket 38 at a location chosen so that it is directly opposite from
the water injection port 40, is an annular recess 76. A plurality of radially extending
water passages 78 couple the recess 76 to the center of the flange 72 so that when
the flanges 36 and 72 are clamped in sandwiching relationship to the gasket 38,
the face of the flange 36 cooperates with the recess 76 to define an annular passage
for conveying water in a circular path where it contacts and cools both flanges
36 and 72. The passages 78 are sized so that water will fill the recess 76 before
flowing radially into the zone 30 where it is contacted by hot exhaust gases and
changed to steam there or subsequently as it becomes more thoroughly mixed with
the hot gases. It is to be understood that the shape of the recess 76 is only exemplary
and that a large variety of recess patterns may be used and still accomplish effective
cooling of the flanges 36 and 72.
It will be appreciated that no matter what water injection
scheme is used at the flange joint between the steam generator body 12 and the elbow
20 for injecting water into the steam generator, water is injected through a port
beyond that of the flame area, thereby eliminating all of the problems associated
with water flowing on the inside surface of the combustion chamber 28.
Having described the preferred embodiment, it will become
apparent that various modifications can be made without departing from the scope
of the invention as defined in the accompanying claims.