US3368604A - Combustion apparatus - Google Patents

Description

Feb. 13, 1968 P. A. MUTCHLER COMBUSTION APPARATUS 2 Sheets- Sheet 1 Filed June 14, 1966 INVENTbR. Pau/ A. Muzc/z/er I Filed June 14, 1966 Feb. 13,l968 P. A. UTCHLER 3,368,604

COMBUST ION APPARATUS 2 Sheets -Shet 2 I INVENTOR. I.

United States Patent dfifice 3,368,604 COMBUSTION APPARATUS Paul A'. Mutchler, University City, Mo., assignor to American Air. Filter Company, Inc., Louisville, Ky., a corporation of Delaware Filed June 14, 1966, Ser. No. 557,493 9 Claims. (Cl. 1584) ABSTRACT OF THE DISCLGSURE It is desirable that fuel burning devices operate efliciently over a wide range of fuel feed rates, and burn different grades and weights of fuel, without the emission of objectionable vapors or smoke. Such fuel burning devices can include combustors which provide means to receive and mix fuel and combustion 'air and to initiate and at least partially complete the combustion process within the confines of the combustor. In many previous combustors, the combustion air flow rate has not been controlled in accordance with the rate of introduction of fuel, so air is continuously introduced into the combustor at the rate necessary to sustain combustion at a maximum fuel feed rate so there is a large excess of combustion air when the combustor is operated at a low fuel rate. The excess air at low fuel feed rate undesirably cools the unburned and partially burned fuel in the combustion chamber, inhibits combustion and reduces the temperature in the combustion zone resulting in smoking, carbon deposition, poor combustion efiiciency, and the emission of flames or partially burned fuel from the combustor. Other previous combustors have provided complicated mechanical means for regulating combustion air flow rate in accordance with the fuel rate or combustion zone temperature but such means are susceptible to failure and erratic operation.

Many such previous combustors also include internal baflles, flame targets, and other means to direct fluid flow within the combustor. Such means increase minimum combustion air pressure requirements and impose additional requirements and restrictions on air movers provided to supply combustion air to the combustor.

Operation of fuel burning devices is stabilized by establishing a flame base at some selected location in the burning device to prevent flame pulsation. Various baffle configurations have been used in previous fuel burning devices and combustors to establish a stable flame base. Such means are usually disposed downstream of the fuel nozzle so the velocity effect of the fuel-air mixture passing the baffle means will induce low pressure at the donwstream side of the baflles. Fuel and air are mixed in the low pressure area where the mixture burns to establish a flame base. Such arrangements have concentrated the flame base so the flame is more stable than where there is no provision for flame stabilization. However, the flame front in such previous devices is susceptible to variation in flow or pressure conditions in the comubstor and in many instances excess fuel is drawn to the low pressure areas resulting in the formation of carbon deposits on the baflie.

Summary of the invention In accordance with applicants invention, an advan- 3,368,604 Patented Feb. 13, 1968 tageous combustor arrangement is provided where the rate of introduction of combustion air to the combustion zone and the distribution of air to various sectors of the combustor is controlled in accordance with the rate of fuel consumption without requiring complex apparatus to control such air distribution. Furthermore, applicants advantageous combustor arrangement in accordance with the present invention assures high temperatures in the combustion zone, even under minimum fuel feeding conditions, so combustion efficiency is improved and smoking and carbon deposition resulting from incomplete combustion are significantly reduced. Further in accordance with the present invention it has been recognized that applicants advantageous efficient combustor arrangement will reduce the total amount of excess air required per unit of fuel consumed and results in a straightforward combustor of decreased physical size, Weight, and simplified configuration which is capable of successfully and efficiently burning a wide range of fuels to give increased heat per unit volume of combustor.

Moreover, the straightforward combustor in accordance with applicants invention further improves combustor oper'ability and efliciency by decreasing internal flow resistance and pressure drop through the combustor by eliminating internal targets or baflles provided in previous combustors to direct combustion gases through reversing paths in such combustors to assure adequate combustion.

Furthermore, the present invention provides a new and advantageous means to establish a stable flame front at a selected location in a fuel burning device wherein the flame front is not concentrated but is spread over a selected wide area. Applicant has recognized that establishing 'a broad flame base provides a stable, smooth burning, flame which is insignificantly affected by changes in conditions Within the combustor.

Various other features of the present invention. will become obvious to one skilled in the art upon reading the disclosure set forth hereinafter.

The combustor in accordance with the present invention provides: first combustion chamber means having an inlet and an outlet; fuel feeding means adjacent the inlet disposed to direct fuel into the first chamber means; first chamber air inlet means to provide combustion air to the first chamber means; orifice means having an aperture smaller than the first chamber outlet disposed in communicative relation, with the first chamber outlet to receive combustion products from the first chamber; second chamber means adjacent the orifice means including an inlet disposed in communicative relation with the aperture of the orifice means to receive combustion products from the orifice means, and outlet means for emission of combustion products from the second chamber means to adjacent heat receivingmeans; second chamber air inlet means to provide com-bustion air to the second chamber means; and, combustion air supply means communicating with the air inlet means ofthe first chamber and the second chamber means to provide combustion air to the chamber means.

Furthermore, the present invention provides an improved fuel burning arrangement comprising: b'affle means having a central aperture and second apertures smaller than the central aperture and spaced radially from the central aperture; a fuel spray nozzle; means to dispose the fuel nozzle and the bafile in spaced, aligned, cooperative relation so the nozzle directs fuel through the central aperture; and, means to supply combustion air to the area intermediate the baffleand the nozzle so air is passed through the central aperture and the spaced second apertures.

It is to be understood that various changes can be made in the arrangement, form, and construction of the fuel burning device disclosed herein without departing from the scope or spirit of the present invention.

FIG. 1 is a sectional view of a combustor in accordance with the present invention;

FIG. 2 is a view taken through a plane passing through line 22 of FIG. 1;

FIG. 3 is an enlarged view, in section, of a partial assembly of the combustor of FIG. 1; and

FIG. 4 is a view taken along a plane passing through line 44 of FIG. 1.

Referring to the drawings of an example of a fuel burnin-g device in accordance with the present invention, an outer casing 11 is provided and is adapted to contain combustion chambers 1 and 2. Chambers 1 and 2 are communicatively aligned through orifice 4 so outlet 9 from combustion chamber 2 communicates with outlet 6A of casing 11. Perforated baffle 12 which is provided at the fuel inlet to chamber 1, is disposed generally transverse the longitudinal axis of chamber 1, and has a central aperture 28 and radially spaced apertures 27. Fuel feeding nozzle 3 is cooperatively disposed to spray fuel through aperture 28 into chamber 1. Combustion air is supplied to combustion chambers 1 and 2 from air chamber 14 and air is supplied to chamber 14 through air conduit 13 from a combustion air source (not shown). Heat and combustion products are discharged through outlet 6A to adjacent heat receiving heat exchange equipment (not shown).

In accordance with one aspect of the present invention, at least two combustion chambers are provided in communicative relation with a flow restricting orifice interposed between and combustion air is advantageously provided to the chambers in a manner hereinafter described. In the example of FIGURE 1, combustor casing 11 is adapted to contain the two cylindrical combustion chambers 1 and 2 which are enclosed by casings 20 and 23 respectively. Spacers and disposed in casing 11, have central orifices 4 and 6 and are adapted to hold casings and 23 in advantageous aligned communicative relation so combustion products, flame, and hot gases emitted from chamber 1 pass through restrictive orifice from chamber 1 pass through restrictive orifice 4 into chamber 2. Combustion products are emitted from chamber 2 and casing 11 through cooperatively aligned orifice 6 and outlet 6A of casing 11. Combustion air is provided to combustion chambers 1 and 2 through air inlets 21 and 22 in casings 20 and 23 respectively. Spacers 5 and 10 can be made of any heat resistant material, for example fire brick, to resist degradation at temperatures encountered in the operation of the combustor. Orifice 4 of spacer 5 is adapted to receive a heat and corrosion resistant orifice ring 4A, for example Hastelloy X. It is to be noted at FIG- URE 4 that spacer 5 further includes air passages 15 to conduct or bypass air from chamber 14 to annular chamber 16 (FIG. 1) defined generally between spacers 5 and 10 and casings 11 and 23. Spacer 10 includes a concave portion 24 adapted to direct air to inlets 22 of casing 23 and annular notch 26 adapted to receive one end of casing 23 in nesting relation. Spacer 10 has a central aperture 6 communicating with outlet 6A from casing 11 and outlet 9 of chamber 2. The cross-sectional area of aperture 6 is advantageously greater than the area of orifice 4 but smaller than the cros'ssectional area of chamber 2. Such an arrangement prevents excessive pressure increase in chamber 2 from the added volume of combustion air and combustion occurring in chamber 2 but can be sized t maintain a selected pressure in chamber 2.

In the example of FIG. 1, a cap 37 covers the end of casing 11 opposite outlet 6A and is fastened to casing 11, for example, by cooperative interlocking notches and pins (not shown). Cap 37 has a central aperture disposed to receive a fuel nozzle holder 32 in generally aligned relation with chamber 1. Nozzle holder 32 is further adapted to receive a fuel feeding nozzle 3, for example an air aspirating fuel nozzle, which is provided to spray a cone of fuel of selected characteristics into the chamber 1. Nozzle 3 is advantageously disposed a selected distance from baffle 12 in axial alignment with aperture 28 of baffle 12 so the fuel spray emanating from nozzle 3 passes through aperture 12 into chamber 1. Nozzle holder 32 includes an end 32A adapted to fit over the inlet end of casing 20 to hold casing 20 and nozzle holder 32 in aligned relation. Nozzle holder 32 has spaced apertures 34 to admit air into the chamber formed between nozzle holder 32 and baffle 12 and such air passes through apertures 27 and 27A into chamber 1.

Combustor casing 11 of FIG. 1 is adapted to receive a conduit 13 connected to an air supply (not shown) to provide combustion air. Conduit 13 communicates through casing 11 with annular-air supply chamber 14 defined between casing 11 and cylindrical combustion air distributing screen 17 disposed between casing 11 and combustion chamber casing 20. Screen 17 includes perforations 17A and is of the same general configuration as chamber 1. In the example of FIG. 1 the diameter of screen 17 is greater than the diameter of chamber 1 so screen 17 surrounds chamber 1 to form an annular chamber 39 therebetween. Screen 17 is provided to prevent direct air flow from conduit 13 to chamber 1 and to distribute combustion air uniformly to inlets 21 of casing 29 because uniform air distribution to inlets 21 promotes smooth burning in chamber 1. The air flow to chamber 1 at minimum pressure in chamber 1 can, advantageously be determined by the size and number of perforations 17A in screen 17. Air distributing screen 17 is supported at one end by tabs 35 joined to the top 36 of cap 37 and at the other end screen 17 is received by a cooperative notched rim 40 in spacer 5. Air from chamber 39 is also supplied through inlets 34 to the chamber defined generally by nozzle holder 32 and bafile 12.

Combustors of the type shown in FIG. 1 are usually adapted to provide heat for selected purposes and the combustor of FIG. 1 can include flange means 18 having a bolt receiving aperture 19 to fasten the combustor to the adjacent heat receiving means (not shown). FIGURE 3 shows one example of a means for joining baffle 12 to casing 20 so that welding or other fastening means is not required. Casing 29 can include a notched portion 25 adapted to receive a peripheral section of baflie 12 in nesting relation. To assemble the arrangement shown in FIGURE 3, casing 20 can be heated to cause a linear expansion of casing 20 and increase the diameter of the casing so that baffle 12 can be forced into the inlet end into nesting relation in notch 25.

In operation, fuel and combustion air are supplied to chamber 1 and the fuel-air mixture is ignited, for example by means of an electric lighter 1a, to initiate combustion.

Combustion air admitted through inlets 34 of nozzle holder 32 passes through central aperture 28 and radially spaced apertures 27 and 27A adjacent casing 20. The velocity of air passing through apertures 27 and 27A develops low pressure adjacent the areas 25 (FIG. 2) between apertures 27, 27A, and 28. The resulting low pressure and turbulence promotes flow of fuel adjacent areas 25 to form a combustible mixture of air and fuel and provides conditions for establishing and maintaining a broad, stable flame base at any fuel feed rate. In accordance with the present invention, it has been recognized that uniform distribution of the established flame front over a broad area prevents flame pulsation and promotes a stabilized flame front in an area adjacent baffle 12.

In accordance with the present invention, a portion of the air entering combustion chamber casing 11 is directed through screen 17 to be supplied to chamber 1 and a portion passes through air passages 15 to chamber 16 to be supplied to chamber 2. The quantity of combustion air admitted to chamber 1 is determined by the differential in pressure between chamber 1 and air supply chamber 14 with the remainder of the air passing through passages 15 to-casing 2. As the pressure in chamber 1 increases, forexample as a result of increased combustion .in the chamber, the differential pressure between chamber 1 and chamber 14 is decreased so more air flows through passage 15 to chamber 2. It will be noted that at no time does all of the combustion air pass to chamber 1. Combustors in accordance with the present invention advantageously provide a sufficient quantity of air to chamber '1 to sustain combustion at low fuel feeding rates so the temperature in the combustion zone remains high enough to promote complete combustion. In accordance with the present invention, a large excess of cool combustion air is not supplied to the combustion zone at low fuel rates because the excess air lowers the temperature in the combustion zone resulting in the emission of partially burned fuel, smoking, and soot formation. The air not required to sustain combustion in chamber 1 is passed to chamber 2 and is mixed, in chamber 2, with the completely burned combustion products emitted from orifice 4. As the rate of fuel feed to nozzle 3 is increased, the rate of combustion in chamber 1 and the size of the combustion zone is increased. Eventually a portion of the combustion zone passes from chamber 1 through orifice 4 into chamber 2 where additional com-bustion air is provided. As the rate of combustion is increased the pressure in chamber 1 increases, as hereinbefore noted, resulting in increased gas velocity through outlet 4 and the velocity effect of the gases emitted through orifice 4 draws combustion air from chamber 16 through inlets 22 and into combustion chamber 2. As the pressure in chamber 1 increases, and the velocity through orifice 4 is increased, more combustion air is drawn to chamber 2. Drawing increasing amounts of air to chamber 2 decreases the quantity of air available in chamber 1 so the combustion process is advantageously more evenly distributed between chambers 1 and 2. It is to be noted that the total quantity of air supplied to casing 11 does not vary widely but the distribution of the air between chambers 1 and 2 varies with the intensity of the combustion occurring.

In accordance with the present invention, it has been recognized that providing an alternate path for the flow of combustion air through the combustor, for example when all combustion air available is not required at low firing rates, provides a combustor that will not expel objectionable fumes at the lowest anticipated firing rates and still provide maximum combustion efficiencies at top firing rates without smoking or soot. The alternate path for introducing unneeded combustion air downstream from the main combustor during low firing rates also contributes to the low pressure com-bustion air requirements during high fire operations because the combustion air is supplied along the length of the combustor to the lowest pressure area.

It is to be further noted that in accordance with the present invention and in applicants advantageous combustor arrangement shown in FIGURE 1, all combustion air, with the exception of that accompanying the fuel sprayed through the baflie orifice and that flowing through the other :baflie openings, intersects the fuel and products of combustion at right angles so all air to enter the attached heat exchanger first flows through the fire to improve fuel air mixing and eliminate the necessity for the flame baflies required in previous combustors. It has been found that in combustor arrangements in accordance with applicants invention combustion air requirements are decreased below the 2550% excess required in previous combustors. In fact, prototype testing has established that it is possible to burn all grades of liquid fuel, gasoline through No. 2 domestic fuel oil with less than ten percent excess air without any trace of smoke or soot in the products of combustion.

The invention claimed is:

1. A fuel burning combustor comprising: a first housing means having fuel and air inlet means and an outlet, defining a first combustion chamber; fuelfeeding means adjacent said first housing inlet to provide fuel to said first chamber; fuel ignition means; first housing air inlet means to provide combustion air to said first chamber; orifice means having an aperture smaller than said first chamber outlet disposed in axial alignment and communicative relation with said first housing outlet to receive combustion gases from said first chamber whereby the velocity of gases emitted from said first chamber is increased; second housing means defining a second chamber having an inlet disposed in axial alignment and communicative relation with said orifice means to receive combustion products from said orifice means, and second housing outlet means for emission of combustion products from said second chamber; second housing air inlet means to provide combustion air to said second chamber; and, primary combustion air chamber means communicating with said first housing air inlet means and said second housing air inlet means to provide combustion air to said first and second chambers so air flow is apportioned between said chambers in accordance with pressure in said first and second chambers.

2'. The fuel burning combustor of claim 1 including first conduit means communicatively connecting said primary air chamber and said first housing air inlet means and second conduit means communicatively connecting said first conduit means and said secondchamber inlet means.

3. The apparatus of claim 1 wherein said first housing air inlet means and said second housing air inlet means include perforations in the side of the said housings to direct flow of air radially into said chambers.

4. The apparatus of claim 1 wherein said first housing and said second housing are of generally hollow cylindrical shape, and said first housing air inlet means and second housing inlet means include perforations in the side of said housings to direct the flow of air radially into said chambers and where the diameter of said second housing is greater than the diameter of said aperture in said orifice means.

5. The apparatus of claim 4 including primary combustion air supply means adjacent said first housing; air distributing means interposed between said primary combustion air supply means and said first housing to distribute supply of combustion air evenly to said first housing air inlet means; secondary air chamber adjacent said second housing to provide combustion air to said second chamber; and, conduit means communicating with said primary combustion air supply means and said secondary air chamber to provide combustion air to said secondary air chamber.

6. In a fuel burning device including a tubular housing defining a combustion chamber and having an inlet end, a gas outlet means and combustion air supply means, an improved flame stabilization arrangement adjacent said casing inlet end comprising: baflie means having a central aperture and at least one second aperture spaced radially from said central aperture; means disposing said bafiie means in said tubular housing transverse the longitudinal axis of said tubular housing so said bafiie means extend substantially across said housing; nozzle means disposed to spray fuel through said central aperture; nozzle holder means to position said fuel nozzle in said tubular housing in spaced relation from and in axial alignment with said central aperture in said bafiie means and define a second chamber between said bafile means and said nozzle, said nozzle holder having spaced, generally axially directed apertures to provide flow of air into said second chamber between said nozzle and said bafile means; and, combustion air supply means communicating with said apertures in said nozzle holder to provide combustion air to said second chamber between said nozzle and said baffle means so all combustion air admitted to said second chamber flows through said central aperture and said spaced second apertures of said bafiie.

7. A fuel burning combustor comprising a first chamber enclosed by a tubular right cylindrical first housing having an inlet, an outlet, and apertures through said housing to admit combustion air radially into said chamber; a flame bafiie having a central aperture and at least one outwardly radially spaced aperture, said bafiie disposed generally transverse the longitudinal axis of said first housing and joined to said first housing around the periphery of said first housing inlet; a fuel feeding nozzle disposed in spaced relation upstream from said flame bafiie to direct a conical spray of fuel through said central aperture into said first chamber, and tubular nozzle housing means extending from said fuel nozzle to said flame bafileto form a chamber between said baflie and said nozzle, said nozzle housing having apertures to permit flow of combustion air into said chamber formed between said bafile and said nozzle so said combustion air flows through said central aperture and said spaced radial aperture in said flame baffie into said first chamber; first orifice means having an aperture disposed in aligned communicative relation with said outlet end of said first housing to receive combustion gases from said first chamber, said aperture having a cross-sectional area less than the cross-sectional area of said first housing outlet; a second chamber enclosed by right cylindrical second housing means having an inlet end in axial alignment and communicative relation with said aperture to receive combustion products from said orifice means, and an outlet end for emission of combustion products from said second chamber, said second housing having spaced apertures therein for admission of combustion air radially into said second chamber; primary air chamber means communieating with a source of combustion air; first air passage means communicating with said primary air chamber means and with said air admitting apertures in said first housing and said apertures in said fuel nozzle housing to provide combustion air to said first chamber; second air passage means communicating with said primary air chamber andsaid air inlet apertures in said second housing for admission of combustion air to said second chamher,

8. The apparatus of claim 7 including orifice means adjacent the outlet of said second housing, said orifice means having an aperture of cross-sectional area less than the cross-sectional area of said outlet of said second housing and disposed in aligned communicative relation with said outlet of said second housing to restrict flow of combustion products and gases from said second chamber.

9. The apparatus of claim 7 including air distribution means interposed between said tubular first housing and said primary air chamber to distribute said combustion air uniformly to said air inlets in said first housing.

References Cited UNITED STATES PATENTS 2,107,365 2/1938 Bray l58-76 X 2,885,858 5/1959 Lloyd 1584 3,247,884 4/1966 McFadden 158-7 3,265,313 8/1966 Paris 158--76 3,267,986 8/1966 Olsson 1584 JAMES W. WESTHAVER, Primary Examiner.

FREDERICK L. MATTESON, IR., Examiner.

E. G. FAVORS, Assistant Examiner.

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