US3418060A - Nozzle mixing gas burner - Google Patents

Description

United States Patent O 3,418,060 NOZZLE MIXING GAS BURNER Lyle S. Spielman and Edward E. Moore, Rockford, Ill., assignors to Eclipse Fuel Engineering Co., Rockford, Ill., a corporation of Illinois Filed May 25, 1967, Ser. No. 641,338 7 Claims. (Cl. 431-158) ABSTRACT F THE DISCLOSURE A gas delivery pipe extends through the closed end and terminates near the open end of a cup which is disposed within and concentric with a tube to which air is delivered so as to be formed into a curtain around the cup and the stream of 4gas discharged from the end of the pipe. Some of the gas flows out of the pipe through holes and is mixed within the cup with air entering through holes so as to provide a continuing pilot flame. Partial combustion of the remaining gas occurs within the tube beyond the cup and is completed beyond a high velocity nozzle as a result of a necking down of the air tube starting well beyond the cup and leading to a restricted discharge nozzle.

Background of the invention This invention relates to -gas burners in which air and gas are supplied through separate conduits into one end of an elongated tube in which small portions of each are mixed within the inlet end of the tube to form a continuous pilot flame while the remaining air and gas are mixed and ignited within the tube producing an efficiently burning flame discharged from the downstream end of the tube.

Summary of the invention In the improved burner, air is delivered into one end of an elongated tube and formed into a cylindrical tubular stream by a cup which opens downstream and surrounds a pipe to which gas is delivered into the tubular air stream beyond the cup. Holes around the pipe and cup admit gas from the pipe and air from the stream to form a pilot mixture which burns continuously at different gas ows as adjusted to provide various temperatures of ame discharged from the burner nozzle.

Beyond the cup, the gas delivered from the pipe end picks up air from the Surrounding tubular air stream, the mixture continuing to burn along the tube. In approaching the nozzle, the air stream is contracted by converging of the tube wall thus providing an air-gas mixture for most eicient or blue dame burning at the different gas ow rates. The tube wall is shaped to retain the tubular form of the air stream all the way through the nozzle thus preventing objectionable heating or erosion of the tube wall.

Brie] description 0f the drawings FIGURE 1 is a side view, on a one-third scale, 0f a gas burner embodying the novel features of the present invention.

FIG. 2 is a fragmentary section taken along the line 2-2 of FIG. 1.

FIG. 3 is a section taken along the broken line 3-3 of FIG. 2.

Description of the preferred embodiment The invention is shown in the drawings incorporated in a nozzle mixing burner comprising an inner tube into which gas is delivered at one end through a pipe 11 and air is forced through a surrounding outer tube 12 to provide at all rates of gas dow a continuously burning pilot ICC within the inlet end of the tube and an e'iciently burning and high velocity blue flame 9 discharged from a nozzle 13 at the downstream end of the tube. A valve 14, adjustable manually or automatically, is interposed in the gas supply pipe 11 which is threaded into a fitting 15 clamped against the inlet end of the air tube. A power driven blower 16 delivers air to the tube at the desired rate, the air being conducted through a pipe 17 into an opening 18 in the side of the tube adjacent the tting 15.

Within the air tube shortly beyond the inlet 18, the gas tube 10 projects through and is secured in a flange 19 projecting from the bottom 21 of a cup 22 having a cylindrical wall 23 somewhat smaller in diameter than the tube 12 and cooperating with the cylindrical internal wall 24 thereof to form a passage 25 of suciently narrow thickness, one-fourth of an inch in the present instance, and of sufficient length to convert the air delivered through the opening 18 into a stream of tubular form, indicated by the dotted arrows in FIG. 2, and direct such stream in such form along and well beyond the open end 26 of the cup and substantially to the nozzle 13.

The gas delivered through the pipe 10 flows through an extension 2B within the cup and part is allowed to escape outwardly through holes 27 in the extension as indicated by the solid arrows in FIG. 2 and to mix within the cup with air forced in through holes 28 angularly spaced around the cup bottom and holes 29 in the side of the cup. The latter holes are arranged in annular series axially spaced apart and disposed beyond the gas holes 27. The mixture thus formed within the cup may be ignited by sparks formed at the open end of the cup across the elec trodes of a spark plug 31. Initially, gas for the pilot mixture is admitted to the tube 10 through a pipe 32 including a valve 33 and connected at opposite ends to the pipe 11 and in parallel with the main regulating valve 14 which is maintained closed until the pilot mixture has been ignited. The spark plug and the rod 30 of a flame detector project into and are mounted in the outer tube 12 so as to be disposed immediately beyond the open end 26 of the cup.

The gas tube 20 projects as shown a short distance beyond the open end 26 of the cup 22 and is open at this end so that the major part of the gas delivered through the pipe is discharged into a zone 34 of the tube disposed beyond the open end of the cup. Preferably and just short of its end 35, the gas tube 20 is formed with an annular series of holes 36 which permits some gas to ow out- Wardly toward the advancing tubular curtain and initiate the formation of a gas-air mixture which is ignited by the pilot flame.

The metal part of the outer tube 12 terminates in an outturned flange 37 axially spaced a short distance beyond the open end of the cup and clamped by screws 38 to a ring 39 telescoped around one end and supporting a relatively thick walled tube 41 composed of refractory material. Herein the internal wall 42 of this tube is somewhat larger in diameter than the tube 12 and extends a substantial distance, about seven inches in the present instance, beyond the end of the metal tube. The refractory tube thus enlarges somewhat and extends the preliminary mixing area to provide for progressive intermixing of the adjacent portions of the advancing tubular air stream and central gas stream over the substantial length of the cylindrical ceramic wall 42. In the zone 34 and continuing on ysubstantially through the zone 43 defined by the cylindrical refractory wall 42, the mixture contains an excess of fuel and therefore burns with a yellow flame.

The present invention contemplates the provision of means near the discharge nozzle 13 for increasing at a rapid rate the proportion of air in the air-gas mixture so as to establish approximately stoichiometric proportions near or beyond the end of the nozzle and therefore optimum combustion el'liciency and a blue name as the products of the combustion are discharged from the nozzle. Such mixing action is achieved by decreasing the diameter of the mixing zone 43 commencing at the end 44 of the cylindrical ceramic wall 42 by a necking down or inwardly tapering of the refractory as indicated at 45 to the discharge nozzle. The diameter of the nozzle is determined by the discharge velocities desired being, in the present instance, about one-third that of the ceramic wall 42.

The inwardly converging wall 45 not only deflects and contracts the oncoming tubular stream of air inwardly toward the nozzle but also intercepts the straight-forward flowing central air-gas stream and thus induces enough turbulence near the nozzle to cause additional air to be mixed with the available gas so as to provide for optimum eliiciency of combustion as evidenced by the blue flame appearing beyond the nozzle opening. This desirable action takes place at all of the varying rates of gas iiow resulting from adjustment of the valve 14 to vary the volumetric rate of gas delivery into the supply pipe and thereby vary correspondingly the temperatures of the excess air and products of combustion as discharged from the nozzle.

In accordance with another aspect of the present iuvention, the converging batlie surface 45 is spaced axially far enough from the open end 26 of the cup 22 to avoid any danger of the resulting turbulence within the ceramic tube from being reflected backwardly and extinguishing or otherwise aecting the continued operation of the pilot flame developed as above described within the cup 22.

Because of the length and narrow radial width of the passage 25, the air delivered into the tube 12 is formed into a tubular curtain which advances at high velocity along the tube wall 24 and the refractory extension 42 thereof. Throughout this advance, the tubular form of the air stream is retained thus insulating the walls 24, 42 from the high temperatures developed within the combustion zones 34, 43. The refractory material is thus protected electually against erosion in spite of the high velocities of liow along the Wall.

Such protection of the refractory material is extended over the entire area of the nozzle Wall 45 by proper contouring of this wall to maintain the tubular form of the advancing air stream as it is contracted due to the convergence of the nozzle wall. For this purpose, the wall not only tapers inwardly but the slope or angle of convergence of the taper decreases progressively from about 60 degrees near the intersection with the cylindrical wall 42 to zero bear the outer end of the nozzle opening. The resulting contour is similar to part of an air-foil section and thus facilitates air flow in changing the direction to contract the stream while maintaining a layer of air at all times over the entire area of the Wall.

In operation, the blower is started to deliver air at the rate required for maximum gas liow and flame temperature, for example 5200 c.f.h. for a burner of the size indicated. With the valve 14 closed, the valve 33 is opened to supply gas for the pilot flame. After ignition as observed through a peep opening 47, the valve14 is opened progressively to deliver gas through the pipe y at the rate required to produce the desired velocity and temperature of the products of combustion. The latter burns eiiciently for all rates of gas ow and appears as a blue ame discharged from the nozzle.

With a burner constructed as above described and of the size indicated, it has been found that with air delivered into the tube 12 at 5200 c.f.h. and gas supplied at the rate of 43 c.f.h., the velocity of the flame discharged from the nozzle 13 will be approximately 10,500 ft./min. By increasing the gas supply to 520 c.f.h. while maintaining the same rate of air flow, the flame velocity is 4 increased to about 27,000 f.p.m. Thus, by adjusting the valve 14 alone, any desired flame velocity and temperature may be obtained.

The burner constructed as above described possesses numerous advantages in addition to those enumerated above. First, a separate pilot is not required since a stable pilot ame is developed and maintained within the cup 22. Secondly, high discharge velocities are attained without the necessity of setting and maintaining specic air-gas ratios. The burner is relatively insensitive to variations of the air-gas ratio and therefore is not subject to the pulsating normally associated with systems in which the liame is discharged into a tube submerged in water. Spark ignition and flame safety devices may be extended through the metal instead of the refractory parts and disposed in proper positions relative to the pilot flame.

We claim:

1. A nozzle mixing gas burner having, in combination, an elongated outer tube closed at one end and having a generally cylindrical inner wall, means for delivering air into said tube through an inlet at said closed end, a generally cylindrical and shallow cup mounted within said tube and opening downstream with the closed bottom of the cup disposed adjacent and downstream from said inlet, said cup being centered within the tube and somewhat smaller in diameter than said wall so as to cooperate therewith in forming the incoming air into a stream which is of narrow radial thickness and remains in tubular form in flowing along said wall beyond the cup, a gas supply pipe having a flow regulating valve therein and extending into the closed end portion of said tube and axially through said bottom to: the open end of the cup, holes angularly spaced around said cup and said pipe within the cup and allowing for the escape of gas from the pipe and the flow of air inwardly to provide within the cup at all rates of gas flow a combustible mixture adapted to burn continuously and form a continuous pilot, said pipe being open at its downstream end so as to deliver the remainder of the gas supply into a preliminary airgas mixing zone Within said tubular air stream, the internal wall of said tube being substantially cylindrical for a substantial distance beyond the open end of said cup, and a wall at the downstream end of said cylindrical wall converging inwardly and progressively to a central discharge nozzle substantially smaller in diameter than said tube wall, said end Wall acting to contract said tubular air stream rapidly around the advancing gas stream to eiiect rapid nal mixing of the air and gas into proper proportions to produce eicient combustion in and beyond said nozzle irrespective of the prevailing rate of supply of gas to said pipe.

2. A gas burner as defined in claim 1 in which said converging end wall is spaced downstream from said cup a substantial distance suicient to prevent turbulence developed in the air-gas mixing adjacent said nozzle from extinguishing the pilot llame Within said cup.

3. A gas burner as defined in claim 1 in which the angle of convergence of said converging wall decreases progressively from a maximum adjacent the downstream end of said cylindrical wall.

4. A gas burner as defined in claim 3 in which said decrease in the angle of convergence of said converging wall is such as to maintain a layer of air covering the wall all the Way to the discharge opening of said nozzle.

5. A gas burner as defined in claim 1 in which said gas pipe extends beyond the open end of said cup and beyond such end is formed with an annular series of holes that permit some of the gas supply to flow outwardly toward said tubular air stream.

y6. A gas burner as defined in claim 1 in which the crosssectional area of the opening in said nozzle is about onethird that of said tube within said cylindrical wall.

7. A gas burner as defined in claim 1 in which the interior of said tube, said converging wall and said nozzle, starting at a point shortly beyond said cup, are com- 5 6 posed of refractory material the surface of which is cov- 2,499,207 2/ 1950 Wolfersperger 15'8-4 ered by the air of said stream al1 the Way through said 3,117,619 1/1964 Lange et al 158-115 nozzle.

References Cited CHARLES I. MYI-IRE, Primary Examiner.

UNITED STATES PATENTS 5 H. B. RAMEY, Assistant Examiner. 868,250 10/1907 Blanchard 158-99 U S C1. X R

2,073,448 3/1937 Fruth et a1. 15s-.109 431264

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