US3220460A - Heat generators - Google Patents

Description

Nov. 30, 1965 G. M. GOUBSKY ETAL 3,220,460

HEAT GENERATORS Filed April 12, 1963 2 Sheets-Sheet 1 FIG.|

INVENTORS. GREGORY MICHAEL GOUBSKY BY ALA O'HEA ATTORNEY Nov. 30, 1965 M. GOUBSKY ETAL 3,220,460

HEAT GENERATORS 2 Sheets-Sheet 2 Filed April 12, 1963 INVENTORS. GREGORY MICHAEL GOUBSKY ALAN O'HEA ATORNEY United States Patent HEAT GENERATORS Gregory Michael Goubsky, Hanworth, and Alan OHea, Dorking, England, assignors to Colt Ventilation and Heating Limited, Surbiton, Surrey, England, a company of Great Britain and Northern Ireland Filed Apr. 12, 1963, Ser. No. 272,752 4 Claims. (Cl. 15828) This application is a continuation-in-part of application Serial No. 26,525, filed May 3, 1960 and now abandoned.

This invention relates to heat generators of the kind comprising a combustion chamber and burner assembly of unitary construction to which liquid or gaseous fuel for combustion is fed under pressure, the heat developed being directly utilized, or imparted to a heat exchanger.

A known application of the latter use is that of space heating. A conventional heat generator for such an application requires a supply of at least 25 pounds of air per pound of fuel for complete combustion and an efliciency in the range of 70 and 80 percent approximately is obtainable with a combustion chamber and heat exchanger of good design and of practical proportions. It is known that efficiencies of most conventional burners fall below the theoretical maximum efficiency of about 86 percent, which is economically unattainable on account of the excessive size of some heat exchangers and outside conditions affecting combustion. The efficiency figures referred to above and elsewhere in the following specification are based upon the gross calorific value of the fuel.

The object of the present invention is the provision of a heat generator of the above kind embodying features which enable stable, clean and complete combustion to be rapidly established and to be maintained with a substantially reduced margin of excess air compared with known equipment of conventional form; such a heat generator has an inherently higher combustion efiiciency and furthermore when operated with an associated heat exchanger for space heating application has an etficiency 3 to 4% higher than known conventional equipment of the same kind and operating with the same exhaust gas temperature. A further object of the present invention is the provision of a heat generator with a form of self-sustaining flame which enables refractories to be dispensed with and which produces combustion products of low volume and high temperature when compared with known equipment of equivalent rating; high heat transfer rates are thus obtainable with small associated heat exchangers whilst the overall size, weight and cost of manufacture of the heat generator and associated equipment are reduced compared with known conventional equipment. A further object of the invention is the provision of a heat generator of the above kind capable of being fired equally efficiently at a wide range of operating rates and the elimination of many of the factorssuch as dependence upon external influences which in conventional burners lead to fluctuations in running eificiency, gradual decline in efliciency, and deterioration in burner components. A still further object of the invention is the provision of a heat generator of the above kind in which the pattern of combustion is rapidly established so that combustion may be established and interrupt-ed artificially in cycles of short duration to enable a modulated heat output to be obtained without sacrifice of efficient combustion.

According to the invention there is provided a heat generator comprising a combustion chamber bounded by a wall, an outlet at one end of said combustion chamber for products of combustion, at least one group of air inlets arranged in said wall, a burner chamber bounded by a casing which is closed at one end and joined at the other end to the said wall by a closure member sealed to said wall, said burner chamber Opening into said combustion chamber, at least one group of air inlets arranged in said casing, at least one surrounding conduit for the supply of air under pressure to said air inlets, deflector means associated with said air inlets for directing air entering said combustion chamber and easing respectively in whirls therein, the air whirling in said combustion chamber in the opposite direction to air in said casing and a fuel injector mounted adjacent the closed end of said casing.

A heat generator of the kind described may comprise a combustion chamber, bounded by a vertical wall of cylindrical form, fitted at the upper end with a frusto-conical discharge aperture and at the other end fitted with a cylindrical extension having a lesser diameter than the combustion chamber wall, said casing being fitted in a circular hole in an annular closing member, said closing member being fitted to the lower end of the combustion chamber wall, the cylindrical combustion chamber wall being fitted with one or more peripherally arranged groups of vaned slots for the admission of air for combustion, with a whirling motion within the combustion chamber, said cylindrical casing being also fitted with one or more groups of vaned inlets arranged to promote a swirl rotating in the opposite direction to and of a smaller diameter than the swirls produced in the combustion chamber, the said air inlets being surrounded with one or more annular jackets forming one or more air supply passages for the admission of air from a high pressure source or sources to said inlets. In this embodiment the said cylindrical casing is closed by a disc member at the end opposite the said frusto-conical member and a fuel injection nozzle is mounted in proximity to the said disc for the admission of fuel under pressure from a fuel pump, and ignition electrodes are mounted in proximity to the said fuel injector for ignition of the fuel in the known manner. A second frusto-conical member is conveniently located on the end of the said cylindrical casing opposite to the said disc to accentuate the swirl or air emerging from the said cylindrical casing and to promote an intense interaction in contrary rotating directions with the swirls of larger diameter in the combustion chamber promoted by the said vaned inlets in the walls thereof.

A heat generator according to the invention embodies a fundamentally new system of cumbustion air supply, viz, in respect of location, velocity, distribution and of tem- .perature and will operate when fired -with oil fuel with approximately only 16 pounds of combustion air per pound of fuel compared with at least 25 pounds for known equipment of conventional type. A heat generator constructed according to the invention and supplied with gaseous fuel will operate with an excess combustion air supply amounting to less than 15% of the theoretical minimum needs for complete combustion.

One application of this invention involves the use of an associated heat exchange chamber surrounded by a separate supply of air under pressure for absorption of heat through the walls of said heat generator and heat exchange chamber and subsequent discharge from on outer enclosing shell for distribution. In such an application the combustion chamber communicates with a heat exchange chamber of double wall annular construction which is disposed around the heat generator, the whole being mounted at the upper part of an outer shell, the lower part of which has mounted therein an air fan for forcing air lower and around a heat generator and associated heat exchange chamber to the distribution outlet.

In the case of oil fuel the heat release rates for combustion equipment used for space heating are from 15,000 to 50,000 B.t.u.s/hr. per cubic foot of combustion chamber space whereas in the application of the subject of this invention in this field it has been possible to obtain a rating approaching 500,000 B.t.u.s/hr. per cubic foot.

Furthermore, in such an application of a heat generator made according to the invention the total size of the complete unit is very much smaller on a volumetric basis than the size of known units for the same output.

In order that the invention may be clearly understood and readily carried into effect, reference is directed to the accompanying drawings, wherein:

FIGURE 1 illustrates diagrammatically in vertical section one embodiment of an oil fired heat generator constructed in accordance with the present invention;

FIGURE 2A is a sectional plan on the line IIII in FIGURE 1;

FIGURE 2B is a sectional plan View of a modified construction of the heat generator shown in FIGURE 1;

FIGURE 3 illustrates diagrammatically in vertical section another embodiment of an oil fired heat generator constructed in accordance with the present invention; and,

FIGURE 4 is a sectional plan of such a unit on the line IVIV in FIGURE 3.

Referring to FIGURES 1 and 2A these illustrate a heat generator in which a unitary construction is used to provide a combustion chamber 1 bounded by a vertical cylindrical wall 2 which is provided at the top with frustoconical extension 7 to form a discharge outlet 8 for the products of combustion.

The lower end of the combustion chamber 1 is closed by a closure member 10b and the cylindrical casing 12 bounding a burner chamber is closed at its lower end by a circular closure plate 11. Associated with the combustion chamber wall 1 is a surrounding closed jacket 3a forming an annular passage a communicating with a conduit 9a from a source of high pressure air diagrammatically illustrated at 46. Associated with the cylindrical casing 12 is a closed jacket 3b forming an annular passage 5b communicating with a conduit 912 from the same source of high pressure air. Formed in the combustion chamber wall 2 are two groups of circumferentially arranged slots 14 each provided with a vane 14a projecting inwards from the cylindrical wall 2 at an angle to the periphery. The slots 14 are in communication with the annular passage 5a. Arranged in the wall of the cylindrical casing 12 are slots 15 each provided with a vane 15a projecting inwards from the cylindrical wall of the casing 12 at an angle to the periphery thereof. The slots 15 are in communication with the annular passage 5b. The vanes 14a are so arranged as to promote a swirl within the combustion chamber 1 of combustion air emerging from the annular passage 5a with a rotation contrary to the direction of rotation of a swirl of combustion air similarly promoted by the vanes 15a. The closure plate 11 at the bottom of the cylindrical casing 12 supports an oil fuel nozzle 16 of known construction supplied with oil fuel under pressure, ignition electrodes 17 also being mounted on the closure plate 11 for initiating combustion in the known manner. The nozzle 16 is thus adjacent to the closed end of the casing 12.

In the modified construction illustrated in FIGURE 2B, the vanes 14b instead of projecting inwards into the combustion chamber 1, project outwards from the cylindrical wall 2 at an angle to the periphery. Similarly the vanes 15a may also be arranged to project outwards instead of inwards.

Referring to FIGURES 3 and 4 of the drawings which illustrate another embodiment of a heat generator constructed according to the invention a unitary construction is used providing a combustion chamber 1 bounded by three cylindrical walls 2, 3 and 4 forming between them two annular spaces 5 and 6. The outer wall 4 is turned in and joins the perimeter edge of wall 2 and then continues at the upper part to form a combustion chamber extension 7 and provide a discharge outlet 8 for the products of combustion.

The lower end of the combustion chamber 1 formed by inner wall 2 is closed at its lower end by a closure member of inverted frusto-conical form and a cylindrical casing 12 bounds a burner chamber and is closed at its lower end by a circular closure plate 11. The intermediate wall 3 is open at the top to permit communication between annular spaces 5 and 6 and is closed to the circular closure plate 11 through the intermediary of an annular closure member 13.

The outer wall 4 is closed by a wall 4a spaced below the lower end of the cylindrical casing 12, means forming an air inlet 9 to the outermost annular passage 6 being provided.

The source of high pressure air 46 connected to conduit 9 forces air up the passage 6 and down the passage 5, some air for combustion entering through slots 44, vanes 44a being provided to promote a swirl within the combustion chamber 1 in one direction. The air entering the cylindrical casing 12 through slots 45 is given a swirl in the opposite direction by means of vanes 45a which project outwardly from the wall of the casing 12 at an angle to the periphery thereof. Further air enters the combustion chambers through perforated inlets 10a arranged circumferentially in the conical wall 10.

The circular closing plate 11 supports an oil fuel injection assembly having a nozzle 16 of known construction supplied with oil fuel under pressure, ignition electrodes 17 also being fitted to the closure plate 11 for initiating combustion. The nozzle 16 is again adjacent to the closed end of the casing 12. Helical guide vanes 18 may be incorporated in annular spaces 5 and 6 for promotion of contraflow preheating of combustion air with consequent cooling of the heat generator walls and ultimate transfer of heat outwards through outer wall 4.

A series of holes 19 are arranged about the axis of the circular closure plate 11 and permit the passage of light from the combustion flame for the energization of a photoelectric flame failure device mounted in the space 20. This photoelectric flame failure device operates in a known manner.

The vortex produced by the vanes 44a provides an outer swirl of combustion air within the combustion chamber, while the vanes 45a produce an inner vortex of combustion air in contra-rotating direction the core of which provides a stabilized zone for flame propagation of fuel issuing from nozzle 16 in the known manner; at the same time the swirl assists in obtaining homogeneity and turbulence of fuel .and air whilst ensuring a fuel lean mixture in the vicinity of inner wall 2 to prevent combustion taking place close to the surface of the said wall 2.

The location and function of combustion air inlets consisting of slots 14 and 15, vanes 14a and 15a and in the embodiment illustrated in FIGURES 3 and 4, the perforated inlets 10a .are fundamental to the operation of the heat generator according to the invention. In the latter case the air enters inwards through the perforations 10a at right angles to the rotating fuel and air mixture emanating from the lower portion of the combustion chamber, the fuel and air mixture again interacting with contrarotating combustion air inlet through inlets 14.

The interaction between the fuel spray and the patterned combustion airstreams causes intense eddy diffusion to result and a self-stabilized flame front occurs regardless of the output over a very wide range, thus dispensing. with components such as flame Spreaders, baffles, stabilizers and the like which must be designed for a fixed rate of flow. The. high temperature and thickness of the stable flame front produced is such that the larger fuel droplets vaporize and burn within the contour of the flame front.

The overall effect produced is one of optimum homogeneity of fuel and preheated combustion air within the combustion zone producing an intense and stable selfcontained combustion in a small combustion volume compared with conventional equipment of equivalent rating. The combustion pattern being self-contained and independent ofthe refractory effects of the combustion chamber boundaries establishes itself instantaneously and advantage may be taken of this factor to operate with short time cycles of firing.

The characteristics of combustion obtained with a heat generator constructed according to the present invention are such that it may be fired at rates of combustion down to ten percent of maximum without loss of stability or efficiency.

Holes in the cylindrical intermediate wall 3 of the preheating passages 5 and 6 may be desirable in order to promote a degree of intercommunication between the two passages so that excessive temperature gradients in the combusion chamber inner wall may be eliminated.

The high temperatures of the combustion chamber zone and the absence of combustion in the immediate vicinity of the inner wall 2, the conical portion 10 and the cylindrical casing 12 ensure that sooting up cannot occur; as carbon deposits are hygroscopic the heat generator does not suffer from the usual corrosive effects associated with carbon formation. When fired with oil fuel any tendency to burner nozzle dribble on shut-off is minimized by the extremely high temperatures which persist for sufficient time to promote immediate combustion of the last particles of fuel admitted.

An annular deflector 21 of conical form may be fitted to the upper portion of the cylindrical casing 12 for the purpose of controlling combustion in the region 22.

In one application of a heat generator constructed according to the invention applied for space heating in conjunction with an associated heat exchange unit and operating with oil fuel, practical overall operating efiiciences in excess of eighty-four percent based on the gross calorific value of fuel may be obtained and maintained in a cubic space content less than would be required in conventional equipment; the combustion zone being relatively small a valuable contribution to reduction in outer shell or casing size and cost of manufacture is made whilst the high working temperatures coupled with the much reduced volumetric contents of the products of combustion makes possible the desired heat transfer in an associated heat exchange unit of much reduced proportions compared with known equipment of conventional form operating at the equivalent rating and with the same discharge temperature of gases into the exhaust stack.

The behaviour of the unit is substantially unaffected by variations in external ambient conditions such as flue stack effects. At thesame time the maintaining of efficiency of the unit is automatic and is not left in the hands of personnel.

A heat generator constructed according to the invention may be mounted and run at any angle or position which permits of flexibility in use and in the choice of the best form of housing. Moreover, in certain circumstances, it can even be completely inverted so that the burner is at the top and the outlet 8 for the products of combustion is at the bottom.

The design is such that blow back associated with conventional equipment is entirely eliminated; this derives from the fact that the combustion chamber is pressurized by a high pressure blower and is assured by the fact that both static pressure and velocity head of the combustion air is available to quench any tendency to blow back.

The small relative size of a refractory-less heat generator constructed according to the invention and any associated heat exchange chamber coupled to it provides a reduction in thermal inertia of the unit with consequent reduction in warming up time.

The use of a heat generator constructed according to the present invention is not limited to space heating application, as many other applications of the heat generator are envisaged, for example, the direct utilization of the heat output for materials drying, industrial process drying and furnace or oven heating and other indirect uses involving heat exchangers for promoting heat and power utilization.

Further, the use of the heat generator is not restricted to static equipment as the small size and light weight for the outputs obtainable will enable use to be made of it in portable equipment for similar diverse purposes.

What we claim and desire to secure by Letters Patent is:

1. A heat generator comprising at least three concentrically arranged cylindrical walls constituting outer, intermediate and inner walls, said Walls defining inner and outer passages of annular form, said inner wall forming a combustion chamber and providing an outlet at the upper end of the chamber for products of combustion, a closure member of inverted frusto-conical form at the lower end of said inner wall, a cylindrical burner chamber bounded by a casing fitted to said closure member, a circular closure plate for the lower end of said cylindrical casing, an axially disposed pressure fed fuel injection assembly supported on said circular closure plate, a closure plate spaced below the lower end of said cylindrical casing for said outer cylindrical wall, an annular closing member between the top end portions of the outer and inner cylindrical walls, an annular closure member for the lower end of the said intermediate wall and said circular closure plate, means for admitting air to the outermost annular passage, said outermost annular passage communicating with the innermost annular passage, said inner wall having vaned slots for the admission of air from said inner annular passage to said combustion chamber, said frusto-conical closure member having perforations for admission of air to said combustion chamber and circumferentially arranged vaned slots formed in said cylindrical casing for the admission of air to said pressure fed fuel injection assembly, and a connection for a source of high pressure air to the means for admitting air, the vanes in the slots in the inner wall of the combustion chamber being inclined in the opposite direction to the vanes in the slots in the cylindrical casing.

2. A heat generator according to claim 1, wherein ignition electrodes for igniting combustion are disposed in said cylindrical casing.

3. A heat generator according to claim 1, wherein helical guide vanes are disposed in the inner and outer annular passages adjacent the upper ends of said passages.

4. A heat generator according to claim 1, wherein the outer wall is turned inwardly at its upper edge and joined to the inner wall at a point below the upper end of the inner wall to form said first named annular closure member.

References Cited by the Examiner UNITED STATES PATENTS 1,020,048 3/ 1912 Normand 15 8-1 15 2,452,779 11/1948 McCollum 15 8-28 2,553,091 5/1951 Homing. 2,603,064 7/ 1952 Williams 158--28 X 2,607,193 8/1952 Berggran et al. 2,654,219 10/1953 Zaba 15828 X FOREIGN PATENTS 1,112,637 11/1955 France.

376,570 5/ 1923 Germany.

JAMES W. WESTHAVER, Primary Examiner.

Claims (1)

1. A HEAT GENERATOR COMPRISING AT LEAST THREE CONCENTRICALLY ARRANGED CYLINDRICAL WALLS CONSTITUTING OUTER, INTERMEDIATE AND INNER WALLS, SAID WALLS DEFINING INNER AND OUTER PASSAGES OF ANNULAR FORM, SAID INNER WALL FORMING A COMBUSTION CHAMBER AND PROVIDING AN OUTLET AT THE UPPER END OF THE CHAMBER FOR PRODUCTS OF COMBUSTION, A CLOSURE MEMBER OF INVERTED FRUSTO-CONICAL FORM AT THE LOWER END OF SAID INNER WALL, A CYLINDRICAL BURNER CHAMBER BOUNDED BY A CASING FITTED TO SAID CLOSURE MEMBER, A CIRCULAR CLOSURE PLATE FOR THE LOWER END OF SAID CYLINDRICAL CASING, AN AXIALLY DISPOSED PRESSURE FED FUEL INJECTION ASSEMBLY SUPPORTED ON SAID CIRCULAR CLOSURE PLATE, A CLOSURE PLATE SPACED BELOW THE LOWER END OF SAID CYLINDRICAL CASING FOR SAID OUTER CYLINDRICAL WALL, AN ANNULAR CLOSING MEMBER BETWEEN THE TOP END PORTIONS OF THE OUTER AND INNER CYLINDRICAL WALLS, AN ANNULAR CLOSURE MEMBER FOR THE LOWER END OF THE SAID INTERMEDIATE WALL AND SAID CIRCULAR PLATE, MEANS FOR ADMITTING AIR TO THE OUTERMOST ANNULAR PASSAGE, SAID OUTERMOST ANNULAR PASSAGE COMMUNICATING WITH THE INNERMOST ANNULAR PASSAGE, SAID INNER WALL HAVING VANED SLOTS FOR THE ADMISSION OF AIR FROM SAID INNER ANNULAR PASSAGE TO SID COMBUSTION CHAMBER, SAID FRUSTO-CONICAL CLOSURE MEMBER HAVING PERFORATIONS FOR ADMISSION OF AIR TO SAID COMBUSTION CHAMBER AND CIRCUMFERENTIALLY ARRANGED VANED SLOTS FORMED IN SAID CYLINDRICAL CASING FOR THE ADMISSION OF AIR TO SAID PRESSURE FED FUEL INJECTION ASSEMBLY, AND A CONNECTION FOR A SOURCE OF HIGH PRESSURE AIR TO THE MEANS FOR ADMITTING AIR, THE VANES IN THE SLOTS IN THE INNER WALL OF THE COMBUSTION CHAMBER BEING INCLINED IN THE OPPOSITE DIRECTION TO THE VANES IN THE SLOTS IN THE CYLINDRICAL CASING.

Images