US3705690A

US3705690A - Combustion heads

Info

Publication number: US3705690A
Application number: US244673A
Authority: US
Inventors: Joseph W Brown
Original assignee: Individual
Current assignee: Individual
Priority date: 1972-04-17
Filing date: 1972-04-17
Publication date: 1972-12-12
Anticipated expiration: 1989-12-12

Abstract

A combustion head which surrounds the fuel nozzle in an oil burner, the combustion head directing a stream of air into a cone which converges at the fuel nozzle; the inside of the combustion head is contoured to achieve maximum air velocity at the plane of fuel injection.

Description

United States Patent Brown 1451 Dec. 12, 1972 [54] COMBUSTION HEADS [72] Inventor: Joseph W. Brown, 5051 Walton Avenue, Philadelphia, Pa. 19143 [22] Filed: April 17, 1972 [21] Appl. No.1 244,673

Related [1.8. Application Data [63] Continuation-impart of Ser. No. 115,969, Feb. 1 1971, abandoned.

[52] US. Cl. ..239/424.5, 239/430, 431/353 [51] Int. Cl ..F23d 11/38 [58] Field of Search ..239/419, 419.5, 423, 424, 424.5, 239/427, 429, 430, 431, 434.5; 431/187,

[56] References Cited UNITED STATES PATENTS 1,172,755 2/1916 Wilson ..431/35l 1,423,650 7/1922 Decuir ..239/427 X 2,334,617 11/1943 ..43l/l88 2,485,207 10/1949 ....239/43l X 3,232,542 2/1966 Colin-Smith". ..239/431 X 3,365,136 1/1968 Hoffman ..239/430 X Primary Examiner- M. Henson Wood, Jr; Assistant Examiner-Michael Mar 2 Attorney-Otto M. Wildensteiner [57 ABSTRACT A combustion head which surrounds the fuel nozzle in an oil burner, the combustion head directing a stream of air into a cone which converges at the fuel nozzle; the inside of the combustion head is contoured to achieve maximum air velocity at the plane of fuel injection.

5 Claims, 6 Drawing Figures PMENTEDnEm m2 SHEET 1 0F 2 v INVENTOR. Joya v25 .5 r0 W/7 PATENTED DEC 12 I972 3 7 05 690 SHEET 2 BF 2 I NVENTOR.

Joye 9h Brow/7 COMBUSTION HEADS This application is a continuation in part of Ser. No. 1 15,969, filed Feb. 17, 1971, now abandoned.

The primary objective of any system involving combustion is to maximize combustion efficiency; that is, to generate the maximum amount of heat that can be obtained from burning a given amount of fuel. As combustion efficiency goes up, the cost of providing heat goes down since each unit of fuel liberates a greater amount of heat. This direct economic benefit of combustion efficiency increase is most noticeable to the average person when applied to the process of heating his home; if the efficiency of his furnace is increased by percent, his fuel bill will be decreased by approximately that amount. Conversely, his fuel bill will go up if the combustion efficiency of the furnace goes down.

A further consideration of interest to the homeowner is heat release rate. Basically, this is a measure of the size of the heating plant required to generate a given amount of heat (expressed as BTUs) in a given amount of time. Heat release rates are usually expressed as BTUs per cubic foot of furnace volume per hour. An increase in this number indicates that a greater amount of heat is being liberated by a combustion system; therefore if the heat output required of the system is constant, an increase in heat release rate means that the size of the system can be reduced without reducing its heat output. For the homeowner that means a smaller, hence cheaper, home furnace. It also means that the furnace will take up less floor space, leaving more useable floor area in the house.

Both of the above, combustion efficiency and heat release rate, are affected by the way in which air is mixed with the fuel being burned. Obviously, if not enough air is supplied, the flame will be weak and smoky; the result will be low combustion efficiency and a low heat release rate. However, a bright flame with a high combustion efficiency does not necessarily imply a high heat release rate; this is so because the flame may be quite long, requiring a large volume and thereby producing a low heat release per cubic foot of burner volume. Therefore, it can be seen that what is required is a short, intense, hot flame.

Furthermore, the hardware that produces this short intense flame must not surround the flame region or be exposed to it because of the possibility of the hardware being burned by the flame. It must be upstream of the flame region, and operate by directing air into the flame region in the proper amounts and locations. In this manner the desired flame will be produced without running the risk of having the hardware burned up in use.

The part of a furnace which performs this function of producing a flame with the desired characteristics is known as the combustion head. A combustion head is merely a member which surrounds the fuel nozzle, and is contoured to direct air into the flame. Prior art combustion heads, such as that shown in Glendenning U.S. Pat. No. 2,393,897, suffer from either or both of the following drawbacks: there is no stream of air within the combustion head directed at the fuel nozzle; or the inside of the combustion head is not aerodynamically clean near the fuel nozzle, which results in a loss of velocity at that point. In either case, the result is a flame that is not as short and intense as it could be, with correspondingly poor performance.

Accordingly, it is an object of the present invention to provide a combustion head for an oil burning furnace that promotes both high combustion efiiciency and high heat release rates.

It is a further object to provide a combustion head for an oil burner that promotes a very short intense flame.

It is a further object to provide a combustion head for an oil burner that is completely upstream of the flame region of the burner.

Other objects and intentions of the present invention will be apparent from the following specification and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is'a side elevation of a combustion head of the present invention;

FIG. 2 is a top view of the combustion head of FIG.

FIG. 3 is taken on line 3-3 of FIG. 2; FIG. 4 shows an alternate configuration of the combustion head-of the present invention;

' FIG. 5 is a top view of the configuration of FIG. 4; and

FIG. 6 is taken on line 6-6 of FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. 1-3, 1 designates the combustion head of the present invention. When installed in a home heating furnace, the combustion head surrounds an oil injection nozzle 2, which forms no part of this invention. The oil nozzle may be of any type, but preferably is of the pressure atomizing type wherein oil under pressure is directed out of the nozzle in such a manner that it forms a cone of atomized fuel, as shown in FIG. 3. The combustion head is in turn surrounded by a blast tube 2a, which receives the pressurized air from the fan associated with the oil burner. This pressurized air from the fan, moving in the direction of arrow 3, divides into two streams; the primary air stream, which flows into the combustion head; and the secondary air stream, which flows around the combustion head.

An air retaining ring 4 surrounds the combustion head near its upstream end; the purpose of this ring is to direct air into the air jets 5. It will be seen that air jets 5 are at an angle to the sidewalls of the combustion head; in this manner a cone of air is directed at the fuel nozzle. There are additional air holes 6 on the upstream end of the combustion head, in order to provide an additional flow of air downstream through the combustion head. As shown in FIG. 2, the upstream end of the combustion head has provision for the passage therethrough of a fuel line and fuel igniter, holes 7 and 8 respectively.

Lugs 9 are utilized to locate the combustion head centrally within the blast tube. These lugs merely rest on the inside wall of the blast tube, thereby allowing the combustion head to be moved axially within the blast tube by the control rod. As can be seen, a slight gap will exist between the air retaining ring 4 and the inside of the blast tube; secondary air flows through this gap and mixes with the primary air stream and fuel as will be explained later.

Referring to FIG. 3, tapped hole has been provided for the reception of a control rod; the function of this control rod will be explained later. As can be seen, the shape of the interior of the combustion head is approximately'that of a venturi. That is, the cross-sectional area of the combustion head decreases to a minimum at its exit; this causes the velocity of the air within to be at a maximum at the exit. It can also be seen from FIG. 3 that the interior of the combustion head is aerodynamically clean; there are no swirl vanes or air deflectors projecting into the flow path within the combustion head. This means that the air is able to flow in an unobstructed manner to the fuel nozzle; the full velocity of the air is then available to break up the cone of fuel, as will be explained later.

The configuration shown in FIGS. 4-6 differs from that in FIGS. 1-3 in number and size of air jets, and in the contours of the downstream half of the combustion head. The larger air jets 5' allow a greater amount of air into the interior of the combustion head, as would be required by a higher fuel flow nozzle. As can be seen in FIG. 6, the downstream end of the combustion head is approximately conical in shape, with its smaller end downstream. This conical shape is not dictated by the higher fuel flow nozzle; it is merely an alternative to the shape shown in FIGS; 1-3. Since the internal cross-sectional area of this configuration also decreases in a downstream direction, the airflow will likewise be accelerated to a maximum at the exit.

In operation, air is forced through the blast tube by means of the blower associated with the combustion unit. Most of this air, the primary air stream, flows into the combustion head through

holes

5 and 6. The inside contours of the combustion head accelerate this air to a high velocity at the exit. Secondary air flows between the air retaining ring 4 and the interior of the blast tube; it then flows around the outside of the combustion head and mixes with the primary air stream and fuel spray. Fuel is supplied to the fuel nozzle under pressure, generally about 100 psi. It issues from the nozzle in a cone of very finely atomized droplets, and is immediately contacted by the high velocity primary air stream. Since the cone of fuel is at an angle of approximately 40 to the primary air stream (the included angle of the cone is approximately 80), there is a considerable amount of shear of the fuel stream by the air stream; there is also a great amount of turbulence between the two streams. This shear and turbulence result in very intimate mixing of the two streams in a short axial length; this in turn results in the short intense flame referred to earlier. Tests have shown that optimum operation occurs when the exit plane of the combustion head is approximately V4 inch downstream from the exit of the fuel nozzle; with the combustion head in this location, fuel consumption is cut 15-24 percent, pollution is cut 44-46 percent, and smoke output is 0. I

In order to adjust the location of the combustion head during operation, provision is made for a control rod. This is merely a rod which is threaded into tapped hole 10 and which extends upstream to a location outside of the blast tube. By means of this rod' the combustion head is moved axially within the blast tube until the combustion process is observed to be most intense,

then it is locked in place. In this manner, minor variations 111 fuel nozzle spray cones, etc. can be accommodated.

I claim:

1. A combustion system, comprising an air stream, a blast tube surrounding said air stream, a fuel nozzle within said air stream, and a combustion head surrounding said fuel nozzle, said combustion head comprising a generally barrel-shaped member having an open downstream end, a closed upstream end perpendicular to the longitudinal axis of said combusiton head and having air admission holes therethrough, a first diverging sidewall adjacent said closed end and coaxial with said axis, and a second sidewall adjacent said first sidewall and substantially parallel with said axis, said first side wall having air admission holes at an angle other than degrees with said sidewall.

2. The combustion system of claim 1 wherein said air admission holes direct air onto said fuel nozzle.

3. The combustion system of claim 2 further including means to accelerate the air flow within said combustion head.

.4. The combustion system of claim 3 wherein said accelerating means comprises a substantially venturishaped contour incorporated into said second sidewall of said combustion head.

5. The combustion system of claim 3 wherein said accelerating means comprises a substantially conical contour incorporated into said second sidewall of said combustion head.

Claims

1. A combustion system, comprising : an air stream, a blast tube surrounding said air stream, a fuel nozzle within said air stream, and a combustion head surrounding said fuel nozzle, said combustion head comprising a generally barrel-shaped member having an open downstream end, a closed upstream end perpendicular to the longitudinal axis of said combusiton head and having air admission holes therethrough, a first diverging sidewall adjacent said closed end and coaxial with said axis, and a second sidewall adjacent said first sidewall and substantially parallel with said axis, said first side wall having air admission holes at an angle other than 90 degrees with said sidewall.

4. The combustion system of claim 3 wherein said accelerating means comprises a substantially venturi-shaped contOur incorporated into said second sidewall of said combustion head.