IL30215A - Fuel burner - Google Patents

Description

FUEL BURNER • The invention is concerned with a fuel burner of the atomizing type and in particular with a liquid fuel burner which is universally adopted to cause efficient combustion of any liquid fuel.

More, particularly, the invention relates to liquid fuel burners wherein the fuel to be consumed is supplied to and dispersed from a film forming surface in spherical shaped droplets of spray, the excess fuel supplied to the surface being recirculated.

An object of the invention, then is to produce a liquid fuel burner with a high combustion efficiency that will not deteriorate with the operation of the burner.

Another object of the invention is to produce a liquid fuel burner capable of burning almost any fuel in liquid form, without changing the burner configuration or spray head.

Still another object of the invention Is to produce a simple reliable liquid fuel burner.

A further object of the Invention is to provide a novel recirculating type of fuel burner.

Still an additional object of the Invention is to produce a liquid fuel burner of extreme simplicity wherein the fuel does not pass through any nozzle and therefore is not susceptible to clogging with dirty fuel.

An additional object of .the invention is to produce a fuel burner for liquids in which the rate of combustion can be easily and quickly regulated.

Another object of the invention is to produce a liquid fuel burner capable of burning large amounts of fuel and releasing a large amount of heat energy in small compact com-bustion chambers.

Still a further object of the invention is to produce a simply operated gravity or pressure fed, low air pressure liquid fuel burner.

These and other objects of the invention not specl-cally set forth, but inherent therein will become readily apparent from a consideration of the subject master which is directed to a liquid fuel burner comprising a plenum chamber having a source of pressurized air connected therewith, and at least one aperture through the wall thereof; a liquid fuel source, means for admitting fuel from said source onto the outer surface of said plenum chamber, the point of application of said liquid being spaced from the aperture a distance sufficient to permit the fuel to form as a film on said surface before and after encountering said aperture, a housing surrounding said plenum chamber, said housing comprising an apertured chamber and a closure, said closure being provided with at least one dispensing opening aligned with said aperture whereby the liquid may be discharged from said housing and burned externally thereof and means for collecting excess fuel drain-ing from said plenum surface for recirculation thereover.

Having thus described the invention in its broad aspects, the operation and details thereof will become apparent from the following detailed description, wherein reference is made to the drawings in which, Fig. 1 is a side elevational view in section, showing the fuel burner, the fuel and air pressure sources being illustrated schematically, Fig. 2 is a plan sectional view taken along the line 2-2 of Fig. 1, Fig. 3 is an elevational view of a modified diffuser in assembly, Fig. 4a - c are top views showing various diffuser assemblies, Fig. 5 is a top plan view of a modified cover or shroud assembly, and Fig. 6 is a sectional view taken along the line 6-6 of Fig. 5.

Considering, now, Fig. 1 in detail, it .may be seen that burner is comprised of a chamber 1, of generally cylindri-cal form and having a closed bottom 3· Chamber 1 is also provided with a top 5 having a central opening 7 provided, as shown with an upwardly flared peripheral wall 19. While the chamber is illustrated as cylindrical and the top as generally dome shaped, it should be noted that the Invention is not so restricted since any convenient wall and top configuration is possible. A cylindrical form, however, is most easily fabricated as is the domed top 5.

Top 5 is provided with a downwardly depending cylindrical skirt 11 adapted to frictionally engage the lnterl-or of the chamber wall to retain same in place.

Disposed within chamber 1 is a funnel-like fuel collector 13. This collector is positioned concentrically in the chamber and may be held in place by any suitable, support means. In the embodiment of the invention shown, the collector 13 is supported on an elbow like drain tube 15 which is simply a hollow tube having one branch connected to the collector 13 and disposed vertically and the other branch fixed to the chamber 1 and extending therethrough to define a fuel return outlet 17.

Also disposed within chamber 1 and preferably con-centric therewith and with respect to collector 13* is a fuel diffuser assembly 20.

The fuel diffuser assembly is formed by an uppermost and spherical chamber 21 having at least one aperture 23* provided in its surface. In the embodiment disclosed this aperture is disposed at the Uppermost point in the spherical surface and as will be explained later may take a variety of forms. In addition as will be discussed, more than one aperture may be provided.

The spherical chamber 21 is open at its bottom and this opening communicated with a generally tube shaped chamber 25 having a closed bottom in the shape of a down turned cone or point 27. This cone or point is disposed generally over the center of the fuel collector 13.

Extending radially outwardly from chamber 25 is a tubular conduit 29 which is fixed to the wall of chamber 1 and terminates outwardly thereof, whereby the hollow sphere 21 and tubular chamber 25 are placed in communication with a source of gas pressure, outside of chamber 1. The diffuser assembly 20, then, comprises a closed plenum supported within chamber 1.

Also extending through the wall of chamber 1 radially thereof is a further tubular conduit 31 having an inward terminal end 33 disposed adjacent but spaced from the spherical surface of chamber 21. It should be noted that conduit 31 is positioned so as to lie on a diameter extending through the center of the sphere.

Surrounding chamber 1 is an annular or hoop-like collar 35. This collar may be positioned on the outside of the chamber by any suitable means, friction detents such as 37» so that while same is prevented from sliding down the cylin-drlcal chamber it ma be readil rotated with res ect thereto.

The collar 35 Is further provided with at least one, preferably more—two being shown—apertures 39, 39' in the form of windows which may be displaced at a variety of angular positions around cylinder 1.

It will also be seen that the cylindrical wall of chamber 1 is provided with windows 4l, l' located so as to be disposed within the vertical dimension of the collar 35 but having an opening area commensurate with that of the windows 39 in the collar. Thus as the collar is rotated the window or as shown windows 39, 39' and l, 4l' can be brought into and out of registry to any desired degree, the collar 35 serving as a damper as it is rotated and registry between the windows is reduced or obviated completely. As shown in Fig. 2, the collar 35 is positioned so that about half of the window areas 3 s 39' and 4l, l» are registered.

As illustrated schematically in Fig. 1, the conduit 31 is supplied by fuel under pressure from reservoir S, via pump P. In some cases the liquid fuel may be passed directly from reservoir S to conduit 31 provided a suitable gravity flow head is established between reservoir S and conduit 31· As also shown, conduit 29 is supplied with gas from a pressure source shown simply as pump P though this may be a charged gas container or any suitable means capable of supplying gas under pressure at about 3 to 20 p.s.l.g. over sustained periods of time.

Conduit 17 which defines the fuel return conduit also enters into pump Pg and is returned to reservoir S though, again depending on the location of the reservoir S with respect to the burner, this pump P2 may be dispensed with. In other o a i i c osed the burner is not y Inflexibly tied in with any particular system of supply and return so long as the requisite mediums fuel and a gas under pressure are supplied to conduits 31j 29 respectively and unburned fuel is removed from collector 13 via conduit 17.

It should be noted that as illustrated in the drawings, the burner as indicated may be made of glass. However, any suitable material may be used to fabricate these structural parts. For example, the chamber 1 may be stainless steel while the fuel collector is made of similar materialsj the diffuser being glass or vice versa. Similarly the diffuser can be made of stainless or other metallic or even plastic material. Moreover, as will be seen the material user1 may be governed by the type of fuel being burned so that whatever the fuel the burner construction is resistant to solvent action or corrosion by the fuel. Thus, because glass is relatively inert and almost totally unaffected by any fuel and because the burner is adaptable to the combustion of practically every known liquid fuel from gasoline through bunker C oil, it has been Illustrated as formed of glass components.

In Fig. 3, however, a modified version is shown wherein the diffuser assembly is comprised partly of metal, partly of non-metallic material to further illustrate the versatility of the structure.

As shown in Fig. 3 there are various means by which the basic structure may be adapted to accommodate various fuels, combustion rates, etc. Fig. 3 illustrates one such means, it being understood that same is merely exemplary of one mode of effecting this result. In this Figure a diffuser, assembly 20 ' is shown in partial elevation and the spherical upper portion thereof, 21 ' is affixed to the lower member 25 ' by means of a threaded connection. As in Fig. 1, the diffuser sphere is provided with an opening 23 ' shown as a round hole having an outwardly divergent circumferential wall. The wall could of course be straight, i.e. define a cylinder concentric with the central axis of the assembly 21 ' , however, for reasons of greater efficiency it is generally preferred that the aperture be defined by an outwardly opening conical or divergent wall.

By connecting the spherical portion 21 ' of diffuser assembly 20 ' to the lower portion 25 ' > by means of a threaded or "push-pull" type connection, it is possible to change the sphere quite easily. Thus, if as will be explained, it is desired to change the material of the sphere 21 ' this can readily be accomplished by substituting one sphere for another. Also where it is desired to produce a greater burner capacity and/or to modify the flame configuration, sphere 21 may be modified to include more than one aperture 23 the apertures themselves being varied from round holes to elongated slots disposed in various locations in the uppermost portion of the spherical surface. Examples of various modifications are shown in Figs. 4a, b and c, showing a plurality of diffusers 40, 50 and 60 provided with apertures 43, 53 and 63 respectively. It will be noted that in Fig. 4a the apertures are in the form of slots disposed at equally spaced locations around the surface of the sphere. Four such slots are shown in this embodiment. In Fig. 4b the apertures 53 are in the form of round apertures 53 at diametrically spaced points on the surface of the sphere 51. Fig. 4c shows the opening 63 as a slot disposed parallel to the direction of fuel flow. In this connection it should be noted that fuel flow in these Figures is illustrated by the arrows.

From the foregoing descriptive matter, it is believed apparent that while a simple structural embodiment and several variations thereof have been shown, the burner is capable of various modifications and changes as will be readily understood as the mode of operation is described.

In respect of the burner operation, the fundamental concepts involved in producing a spray characterized by the spheroid shape of the minuscule drops has been described in great detail in the prior art. Basically the prior art process involves the introduction of the fluid to be sprayed on an apertured surface with sufficient kinetic energy to cause the liquid to film out or be stressed during its flow over the surface. At the point where the dynamic film is stressed to a high degree--as evidenced by its smooth almost invisible flow pattern—air at very modest pressures is emitted from an opening and small almost perfectly shaped spheroid particles of the liquid are caused to emerge from the film. Experimentation has shown that these particles of liquid are on the order of 50 microns in size where, for example, water is caused to flow in a thin film over a glass surface and air at a pressure of eight p.s.i.g. is caused to flow through a small orifice in said glass surface. In the operation of the disclosed apparatus it generally requires less energy or gas pressure to atomize a liquid '.fuel than it does to atomize water. This is because virtually all liquid hydrocarbon fuels have a low surface tension and excellent wetting characteristics. Good wetting is helpful in the forming of a highly stressed thin film and a low surface tension allows the liquid particles to be easily dispersed from the thin film. For example, because of these favorable physical properties, gasoline can be atomized better at a gas pressure of 3 p.s.i.g. than water can be atomized at a gas pressure of 8 p.s.i.g.

Surprisingly enough, it has been found that if the liquid is introduced onto a film forming surface with sufficient kinetic energy, not only will the fluid flow and spread downwardly as where it is introduced at a point above the surface, but if, as shown, the liquid is ejected against a properly curved surface such as the spherical portion of the diffuser assembly 20, from fuel inlet pipe or conduit 33, the fluid can be caused and will flow upwardly to completely envelop the upper portion of the spherical surface and is highly stressed into a thin dynamic, film which passes over the apertures or aperture 23. If> then, air at very low pressures above the ambient pressure in the chamber is caused to flow through the aperture 23 or apertures 23' > ^3> 53 and 63, there occurs a separation of minuscule drops of liquid from the highly stressed dynamic liquid film. As stated, evidence indicates the drops or droplets are almost uniformly dispersed as to size and shape, being spheroids on the order of 50 microns or less.

While the entire phenomenon is not clearly understood, it has been found that if the spray thus produced is caused to be ejected upwardly through a shroud or cover 5, as shown in Fig. 1 and air is introduced into the chamber 1 through parts l as secondary or combustion air, the diffused liquid will be exited in great volume through the aperture 7 in shroud 5 and if Ignited the liquid fuel burns with a highly intense combustion rate about one half to three quarters of an inch above the aperture 7 and will not propagate itself back into chamber 1. This phenomenon has manifested itself with a variety of liquid fuels including highly volatile fuels such as gasoline. One explanation is that the quantity of atomizing air is so small by comparison to the quantity of fuel atomized, that the fuel/air mixture within chamber 1 is "fuel rich" that is the fuel/air ratio is so unbalanced by the presence of excess fuel, that combustion is impossible. Once the fuel is ejected from the chamber, however, due to the fineness with which it is dispersed, the attainment of a favorable combustion ratio is quite rapid with the consequence that burning occurs quite close to the point of exit of the spray and throughout the entire spray area.

Because of the above described phenomenon, it is possible to regulate the spray pattern and volume by means of the cover or shroud 5 by the simple expedient of providing multiple, selectively usable covers in which the dimensions of the spray exit aperture 7 is varied from one cover to another. Thus, by a matching of a selected opening 7 with the fuel being burned not only can the combustion rate be adjusted quickly and easily, but the spray, hence combustion pattern can be readily and easily varied by not only the cover change but by coupling this feature with a selection of any one of the diffuser designs as exemplified in Pig. 4. It has been found that the spray, hence combustion pattern can be varied from an almost vertical column to a fan shaped pattern.

The quantity of fuel spray and the shape of the spray cloud can also be controlled by rotating collar 35 to allow more or less secondary air to enter chamber 1 through windows 4l and 4l». Air is induced to flow into these windows by the ejector or pumping action of the total spray cloud leaving the fuel burner. The small amount of atomizing air by itself pro- e wit the mass flow of the atomized liquid, a significant amount of secondary air is induced to flow into chamber 1, when windows 4l and 4l' are in the open position. By restricting the flow through windows 4l and 4l' by the rotation of collar 35» the degree of vacuum in chamber 1 can be controlled. The vacuum control in chamber 1 can be in turn used to regulate the quantity and shape of the spray cloud leaving the fuel burner. For example, rotating collar 35 to restrict the secondary flow into chamber 1 through windows 4l and 4l' has the effect of increasing the degree of vacuum inside chamber 1 which in turn reduces the quantity of fuel spray and suppresses the height of the spray plume. It should be noted that while significant secondary air flows into chamber 1 during operation of the burner with side windows 41 and 4l» wide open, this amount of airflow is not sufficient to generate a combustible fuel/air mixture inside chamber 1.

In order to further simplify the structure, a modified shroud or cover 73* such as that shown in Pigs. 5 and 6 may be used. Again the mode of carrying out the structural manifestation of the inventive concept is exemplary only and not limiting. Other and equivalent means will readily occur to those skilled in the art. However, turning to Figs. 5 and 6 it will be seen that cover 73 is plane surfaced and provided with a central opening 77 of rather large diameter. Disposed above the opening and retained on the top surface of the shroud or cover 73 by means of simple L-shaped lugs 79 are a plurality of segment-shaped slidable restrlctors 8l, 83, 85 and 87. Each restrictor may be provided with an adjustment knob noted generally by the numeral 89. It will be noted that the ed es of restrlctors 83 and 87 underlie the edges of restrictors 8l and 85, whereby while each restrictor may be moved inwardly and outwardly with respect to the center of aperture 77 the restrictors acting as a whole form a solid shield or mask which rests on top of cover 73. As will now be obvious movement of the restrictors inwardly has the effect of reducing the overall diameter of the exit aperture through cover 73 and vice versa. In other words, restrictors 8l, 83, 85 and 87 define an iris-like shield whereby the effective area of the aperture may be readily reduced to meet a desired set of conditions.

Having thus described the invention and various aspects thereof, it is believed obvious that a variety of modifications thereof can be made, such being within the spirit and scope of the Inventive concepts involved; these being limited only as defined in the appended claims.

Claims (10)

1. A fuel burner characterized by a burner chamber having an apertured cover thereon, and at least one aperture in the side wall thereofj ayplenum disposed within the chamber, said plenum including a curved apertured surface a collector means having a part external of the closed chamber disposed below the plenum; means for supplying air under pressure to the interior of the plenum and means for supplying fuel to be burned to the curved surface of the plenum at a point spaced from the aperture therein whereby the fuel flows in the form of a highly stressed thin film thereover, the air emitting through the aperture in said surface dispersing fuel in a fog-like mist of minuscule spherical particles exteriorly of said burner chamber, secondary air gaining access to the interior of the burner chamber through the aperture in the side wall thereof.

2. A fuel burner as defined in claim 1 characterized by a fuel recirculation means between the fuel supply means and the fuel collector.

3. A fuel burner as defined in claim 1 characterized by the fact that said plenum is in the form of a hollow sphere having at least one aperture therein disposed at the high point thereof.

4. A fuel burner as defined in claim 1 characterized by the fact that said chamber is comprised of a receptacle provided with a removable cover.

5. A fuel burner as defined in claims 1 and 3 characterized by the fact that the lower surface of the sphere is provided with a hollow vertical column in communication with the interior thereof and said column terminates in an inverted conical end.

6. A fuel burner as defined in claim 1 characterized by the fact that said fuel collector comprises a funnellike receptacle having its low point connected to a conduit, and wherein said receptacle is disposed below and centrally of said plenum.

7. A fuel burner as defined in claim 1 characterized by the fact that said cover is provided with means for varying the size of its aperture.

8. A fuel burner as defined in claim 1 characterized by means for varying the effective size of the aperture in said side wall.

9. A fuel burner as defined in claim 1 characterized by the fact that the means for supplying fuel to the plenum surface comprises a conduit having its terminal end disposed adjacent but below the high point of the curved surface of said plenum.

10. A fuel burner as defined in claim 1 characterized by the fact that said burner chamber is cylindrical and said means for varying the effective size of the aperture in said side wall comprises a rotatable collar surrounding said chamber and in turn provided with an aperture movable into and out of registry with said aperture in said side wall to regulate the flow of secondary air into said chamber.