US3724994A

US3724994A - Burner

Info

Publication number: US3724994A
Application number: US00033672A
Authority: US
Inventors: D Desty
Original assignee: BP PLC
Current assignee: BP PLC
Priority date: 1969-05-19
Filing date: 1970-05-01
Publication date: 1973-04-03
Anticipated expiration: 1990-04-03
Also published as: DE2023060A1; FR2047787A5; SE348044B; AT300270B; NL7007072A; DK135244B; CH505340A; DK135244C; GB1263611A; BE750574A; NO124283B

Abstract

A burner for gaseous fuels, e.g. methane or hydrogen, has a porous exit sheet adjacent to a base plate. The two sheets are perforated to allow the passage of air, and fuel gas circulates between the sheets and around the perforations. The fuel passes through the porous sheet to burn with air passing through the perforations.

Description

United States Patent 1191 Desty [4 Apr. 3, 1973 54] BURNER 1,488,677 4 1924 Hoffman ..431/346X 3 s 'W d e, 3,367,149 2/1968 Manske [75] Inventor f iz enry e y g 491,226 2/1893 Roberts g 2,227,899 1/1941 Grubb 3,173,470 3/1965 Wri m [73] Asslgneez The British Petroleum Company 3,198,240 8/1965 Keitgh etalm Llmlted, London England 3,437,416 4/1969 Saponara ..431/329 [22] Filed: May 1, 1970 [21] Appl. No.: 33,672

[30] Foreign Application Priority Data May 19, 1969 Great Britain ..25,4l9/69 [52] US. Cl. ..43l/328, 239/145, 239/425.5 [51] Int. Cl ..F23d 13/12 [58] Field of Search ..43l/326, 328, 329; 126/39 1, 126/92 B; 239/145, 419.5, 424, 425.5

PrimaryExaminer-Carroll B. Dority, Jr. Attorney-Morgan, Finnegan, Durham & Pine [5 7] ABSTRACT A burner for gaseous fuels, e.g. methane or hydrogen, has a porous exit sheet adjacent to a base plate. The two sheets are perforated to allow the passage of air, and fuel gas circulates between the sheets and around the perforations. The fuel passes through the porous sheet to burn with air passing through the perforations.

[56] References Cited 5 c1 2 n F UNITED STATES PATENTS 3,147,545 9/1964 Valyi ..29/42l 2,194,208 3/1940 Moran ..263/DIG. 5

FUEL

PATENTEDAPR3 I975 3,724,994

FUEL I AIR INVENTORZ DEN|S HENRY DESTY His Attorneys BURNER This invention relates to a burner and in particular to a burner which can burn both high flame speed gases (e.g., hydrogen or towns gas) and low flame speed gases (e.g., methane).

According to the invention a burner for gaseous fuels comprises a perforated porous exit sheet,e.g., a sheet of metal foam, one side of which is adjacent to a combustion zone and the other side of which is adjacent to a perforated base plate to which the exit sheet is connected in such a manner that:

a. The perforations in the exit sheet mate with the perforations in the base plate so as to allow air to pass through them and b. The exit sheet is spaced apart from the base plate between the perforations so as to form fuel passages whose resistance to the flow of fuel gas is low compared with the flow resistance through the exit sheet, the exit sheet being joined to the base plate along the sides of the fuel passages so as to prevent excessive escape of gas through the joints, the whole configuration being such that, during the use of the burner, gaseous fuel passes throughout the fuel passages and thence via the porous exit sheet into the combustion zone where it burns with air drawn through the perforations.

The configuration specified above is particularly suitable for thin burners, e.g., those less than 10 mm, preferably less than 5 mm, thick.

Preferably the perforations are arranged in an hexagonal pattern and the fuel passages extend throughout the interstitial space between the perforations.

In order to achieve uniform air distribution it is desirable that the air holes be uniformly distributed over the burner. The air holes are preferably circular in shape and preferably of an area of 0.01 1 cm. The number of air holes is such that they account for 20 50 percent, preferably 25 35 percent, of the total area of the burner.

The invention will now be described by way of example with reference to the accompanying drawings in which:

FIG. 1 is a plan view of a burner according to the invention, and

FIG. 2 is a cross-section, on an enlarged scale, taken along the line 22 of FIG. 1 through one air hole.

The burner takes the form of a thin sheet and, as can be seen from FIG. 1, the burner is pierced by perforations arranged in an hexagonal pattern. Fuel passages extend throughout the interstital space 11 between the perforations 10.

As can be seen from FIG. 2 the burner is formed from an exit sheet 12 and a base plate 13 which are spaced apart from one another between the perforations 10 so as to form fuel passages 14. A joint 15, between the exit sheet 12 and the base plate 13, extends along the sides of the fuel passages 14. (It is equally correct to state that the joint 15 extends around the perimeter of each perforation 10.) The joint can be formed by suitably folded seams, or by the use of adhesives (e.g., solder) or by a combination of the two.

The exit sheet 12 varies in thickness between 0.5 and 1.0 mm and it is made of metal foam crushed in the ratio 3:1 (i.e., it was about 3 mm thick originally). The base plate is a metal sheet about 0.5 mm thick. Before crushing the metal foam took the form of a three dimensional network of tubular nickel strands which defined dodekahedral pores of average diameter 0.3 mm. The crushing flattened the original pores so that they became thin (about 0.1 mm) in the direction of crushing.

(Irregular dodekahedra can pack to fill space and the foam can be regarded as an example of such a packing. From this point of view the metal strands form the edges of the dodekahedra.)

The thickness of the burner was 5 mm. Each perforation had a diameter of 4 mm and the distance between the centers was 8 mm.

During the use of the burner fuel gas passes throughout the fuel passages 14 and, because their resistance is lower than that of the exit sheet 12, a uniform flow of fuel through the exit sheet 12 into the combustion zone is achieved. Since it is intended that fuel shall escape from the fuel passages 14 it is not necessary that the joints 15 be gas tight. It will be sufficient if the flow resistance through the joint is similar to that through the exit sheet 12 so that a satisfactorily even fuel distribution is obtained.

As is indicated in FIG. 2 the thin cross-section of the burner means that the flow of air tends to diverge over the exit sheet 12 after passing through the air holes 10 and similarly the gas flow through the exit sheet 12 tends to diverge over the air holes 10. This gas flow pattern encourages mixing of air and fuel and hence it facilitates combustion.

The burner shown in FIGS. 1 and 2 is capable of burning a wide range of gaseous fuels, e.g., low flame speed fuels such as methane, ethane, propane and bu- .tane as well as high flame speed fuels such as hydrogen.

In all cases combustion takes place with silent, blue flames by a diffusion mechanism. Combustion is complete within about 15 mm, usually within about 5 mm, of the top face of the burner, making it possible to mount a heat exchanger about 25 mm from the top face of the burner to give compact central heating appliances. Thus an appliance of rectangular cross section 15 cm X 30 cm and 10 12 cm high from the bottom of the burner to the top of the heat exchanger gave a heat output of 25 kw transferred to the water. (Note this power output is limited by the need to keep the exit gases above their dew point.)

I claim:

1. A burner for gaseous fuels, which burner is less than 10 mm thick and comprises a perforated porous exit sheet of metal foam one side of which is adjacent to a combustion zone and the other side of which is adjacent to a perforated base plate to which the exit sheet is connected in such a manner that:

a. The perforations in the exit sheet mate with the perforations in the base plate so as to allow air to pass through them, and

. The exit sheet is spaced apart from the base plate between the perforations so as to form fuel passages whose resistance to the flow of fuel gas is low compared with the flow resistance through the exit sheet, the exit sheet being joined to the base plate along the sides of the fuel passages so as to prevent excessive escape of gas through the joints, the whole configuration being such that during the use of the burner gaseous fuel passes throughout 4. A burner according to claim 1, in which the number of perforations is such that they account for 20-50 percent of the total area of the burner.

5. A burner according to claim 4, in which the 5 number of perforations is such that they account for 25-35 percent of the total area of the burner.

ll l 1F

Claims

1. A burner for gaseous fuels, which burner is less than 10 mm thick and comprises a perforated porous exit sheet of metal foam one side of which is adjacent to a combustion zone and the other side of which is adjacent to a perforated base plate to which the exit sheet is connected in such a manner that: a. The perforations in the exit sheet mate with the perforations in the base plate so as to allow air to pass through them, and b. The exit sheet is spaced apart from the base plate between the perforations so as to form fuel passages whose resistance to the flow of fuel gas is low compared with the flow resistance through the exit sheet, the exit sheet being joined to the base plate along the sides of the fuel passages so as to prevent excessive escape of gas through the joints, the whole configuration being such that during the use of the burner gaseous fuel passes throughout the fuel passages and thence via the porous exit sheet into the combustion zone where it burns with air drawn through the perforations.

2. A burner according to claim 1, in which the burner is less than 5 mm thick.

3. A burner according to claim 1, in which the perforations are circular and have an area of 0.01 - 1 cm2.

4. A burner according to claim 1, in which the number of perforations iS such that they account for 20-50 percent of the total area of the burner.

5. A burner according to claim 4, in which the number of perforations is such that they account for 25-35 percent of the total area of the burner.