US2510888A - Gas burner and mixing tube construction - Google Patents

Description

June 6, 1950 N. E. HILL ET AL GAS BURNER AND MIXING TUBE CONSTRUCTION Filed April 4, 1946 Q ENAAQNA F Patented June 6, 1950 GAS BURNER AND MIXING TUBE CONSTRUCTION Napoleon E. Hill, Otto J. Bess, and Erank J.

Nunlist, Jr., Milwaukee, Wis assignors to, L. J. Mueller Furnace Company Application April 4;. 1946;8erlal Nm' 65956.29

3 Claims. 1

This invention relates to improvements in gas burner and mixing tube constructions.

A general objectof the. invention is to. provide an improved gas burner and mixing tube so constructed as to eliminate extinction noise and flashback characteristics.

In connection with the operation otgas burners having conventional mixing tubes associatedtherewith, considerable difliculty has been experienced when burning gas-with high ignition velocity characteristics. Avery pronounced objection has been the extinction noise and flashback characteristics common to the operation of gas burners formedwithconventional mixing tubes. It is the theory that in such structures the extinction noise and flashback characteristics are caused by the following conditions: When the supply of, gas. to the burner isshut 011', there is, of course, residual gas. in the piping between the shut-off valve and the burner ports or orifices; Upon the closing of .the gas supply shut-off valve, the quantity of gas Within the device and reaching the burner ports isgradually reduced. Consequently, there is less energy in the gas streams leaving the burner ports and the quantity of primary air within the'mechanism is consequently reduced. However, the ratio of primary air togas greatly increases. Up toa definite ratio of primary air to: gas, the ignition velocity of the combustible mixture increases and a situation attains wherein after the .gas supply shut-cif valveto the. mixing tube is closed, the ignition velocity increases until it is greater than the velocity of the primary air-gas mixture in the burner ports. At such time the flame will travel back or recede through the burner ports into the burner head and will ignite the primary air-gas mixture therein. If there is a sufficient volume of the combustible mixture within the. mechanism, an explosion or extinction noiseresults.

With the foregoing explanation in mind, the present invention aims at eliminating objectionableexplosions and extinction noises inherent to the operation of conventional gas burner mech: anisms by providing a. gas burner and mixing tube construction wherein the mixing tube communicating with the burner head has associated therewith a trap which extends above the level of the burner ports. Inasmuch as theair-gas. mixture within the burner head has a specific gravity less than that of air, with the improved elevated trap construction associated with the mixing tube, after the gas supply valve has been shut oif, the air-gas mixturein the burner head a tends to fiow into, and rise to the highest point in the trani, Such trapped air-gasmixture within the trap then tends to block or counteract the-normalfiowof air admitted through an air valveina lower portionof the trapiandby blocking the flowof additional air, the flashback, orflextinction noise tendency of the .burneris overcome.

Camel-e specific object of the invention is to providers gas-burner and mixing, tube. construetion wherein the mixing tube, remote from the burner head, carriesan elevated cylindrical trap which hasl-located'therein below its top, air-and gas inlets.

-A further object'of the .inventionis to providee'gas burner and mixing tubeconstruction wherein thewmixingtube has aportion of substantial lengthat an elevation. above the; elevation'of the burnergas ports, and which terminates, remote from the burner, in a trap of relatively largevolume and projecting above the level of the. burner gas ports, said elevated portions ofthe mixing tube and trap being adapted to receive a light air-gas mixture-and to hold the same, under certain conditions, as a curtain between the primary air :andgas inlets and the burner ports.

A further object of the invention is to providea gas burner and. mixingtube construction of such iormationthat the primary airand/or the primary air-gas mixture must travel upwardly and then: downwardly before reachingthe burner head with the uppermost v ointof flow being substantially abovethe planeof the burner ports.

'A further object of'the invention is. to providea gasburner andmixing tube construction which is very simplais'easy to install, service and reg-- ulate, is relatively inexpensive, which functions eflieiently, andwhich is well adapted for the purposes. described.

'With. the above and'other objects inview, the invention consists of the improved gas burner and mixing tube constructiomand its parts and combinations as set forth in the claims, and all equivalents thereof.

In the. accompanying drawing in which the samexreference characters indicate the same partsin all of the views:

Fig. 1 isaside view,.partlyin longitudinal ver- 'tical sectional view ofthe improved'gas burner andzmixing tube construction with an outer end portiongofthe burner head being broken away;

Fig. 2 is a plan viewof the gas burner and mixing tube; and

Fig.3 is a fragmentary inverted plan view oi 3 that portion of the apparatus which includes the mixing tube and trap.

Referring now more particularly to the drawing, it will be observed that a hollow gas burner is indicated generally by the numeral 8. The burner head may be of any desired accepted shape and may take the form of a T, as illustrated. In top wall portions of the burner head there are a plurality of burner port stools 9 with drilled gas ports or orifices l therethrough. The particular type of gas port referred to is merely by way of illustration and the burner head may, within the purport of the invention, be formed with any conventional type of gas port. The inner end of the burner head 8 is curved upwardly and the gas entrance end therein is surrounded by an annular shoulder I2 adapted to have seated thereon the adjacent end of a mixing tube, indicated generally by the numeral IS. The end portion of the mixing tube referred to is securely connected to the shoulder l2 of the burner head by any suitable means which will provide a gas tight joint.

The mixing tube I3 is venturi-like in formation with the end adjacent the burner head being enlarged and curved downwardly to engage the upturned end of the burner head. The major extent of the mixing tube is horizontal and the same extends at an elevation substantially above the plane of the burner ports H1. The composite structure which includes the burner head 8 and the mixing tube I3 is of goose neck formation.

The outer reduced end' of the mixing tube l3 has formed integral therewith a cylindrical 'casing l4 whose longest dimension is in a vertical plane. The closed upper end of the casing I4 is disposed somewhat above the mixing tube IS. The hollow interior of the casing l4 therefore provides a trap for the purpose hereinafter to be explained, with the interior of the casing having an outlet to the mixing tube somewhat below the top of the casing.

On the side wall of the casing l4 opposite the connection of the casing with the end of the mixing tube i3 is an apertured boss l5 havin secured therethrough a gas supply nipple l6 which is in connection with an outwardly extending gas supply pipe H. The discharge end of the gas nipple i6 is so arranged relative to the casing I 4 that it discharges thereinto generally in alinement with the outer end of the mixing tube I3 and the axis of said mixing tube.

The lower open end of the cylindrical casing I4 is provided with spaced radial webs l 8 adapted to cooperate with an air shutter l9, said webs having a central boss 20 to which is attached by means of a bolt 2|, the adjustable air shutter l9, previously referred to. The adjustable air shutter I9 is of the type which may be turned circularly to more or less close or open the spaces between the fixed webs l8 for the purpose of controlling the amount of primary air admitted into the trap forming casing 14.

Depended from a transverse portion of the burner head 8 is a tapped flange 22 which may be used for the attachment of pilot light equipment. From Fig. 1 it will be observed that the mixing tube [3 provides a gas carrying conduit which is above the level of the burner ports [0. Likewise, the major portion of the interior of the casing I4 is above the level of the burner ports. The gas supply nipple I5 is arranged to supply gas into the apparatus in a stream which is directed toward the open end of the mixing tube I3 and co-axially with said mixing-tube.

The point of introduction of the gas is at an elevation above the plane of the burner ports In. On the other hand, the primary air enters the interior of the casing ID at a considerably lower elevation and the direction of flow of incoming primary air is at right angles to the direction of flow of incoming gas.

If, as is conventional in the operation of a gas burner, an automatic shutofi valve (not shown) terminates gas flow from the gas supply pipe l1 and nipple l6 into the casing II, a condition will thereafter exist where only primary air enters the casing l4 and flows into the mixing tube l3. The air-gas mixture within the apparatus will obviously become diluted. For a time this residual combustible mixture within the apparatus will flow into the hollow burner head 8 and will exhaust through the burner ports I!) where combustion takes place. Eventually, a condition will develop wherein the ignition velocity becomes greater than the velocity of the air-gas mixture at the burner ports. This induces a condition wherein there would ordinarily be a tendency for the flame to travel back into the burner head and ignite the air-gas mixture therein, resulting in a flashback or extinction noise. The present improvements prevent this highly objectionable contingency because the airgas mixture in the burner head, being lighter than air, will tend to flow back through the burner head and rise into the elevated portions of the mixing tube I3 and easing [4, said portions being above the plane of the burner ports. Consequently, this arrangement serves to establish a curtain of light air-gas mixture within said elevated portions of the apparatus. This light air-gas mixture curtain is interposed between the primary air inlet in the lower end of the casing l4 and the gas ports [0 and thereby serves to block the normal flow of primary air which continues to enter the casing Ill, preventing the incoming primary air from further diluting the residual combustible gas in that portion of the apparatus adjacent which the ignition occurs, preventing flashbacks and extinction noises.

It is to be noted that the casing M at the outer end of the mixing tube l3 provides a relatively large capacity, trap or reservoir and under normal conditions it enhances the admission of primary air and gas which are admitted at spaced points and in a manner so that the respective stream are generally at right angles to each other.

From the foregoing description, it will appear that the improved gas burner and mixing tube construction is both simple and novel, eliminates objections inherent to conventional gas burner and mixing tube constructions, and is well adapted for the purposes described.

What we claim as our invention is:

l. A composite gas burner head and mixing tube assembly of goose neck formation wherein the mixing tube portion extends horizontally at an elevation substantially above the burner head portion, the latter being parallel to the major extent of the mixing tube and being provided with burner ports in the top portion thereof, a hollow casing entered by the outer end of the mixing tube portion and extending above the planes of the mixing tube and burner head portions, and spaced apart means entering right angularly sep arated'wall portions of the casing for admitting primary air and gas in a manner so that the primary air stream enters said casing at substantially right angles to the entering gas stream.

2. In a gas burner construction, a hollow elongated burner head formed with upwardly opening burner ports in the top portion thereof, a mixing tube having an elongated rectilinear portion and an elbow portion, the latter portion being connected to the burner head so as to open into the interior of the latter at substantially a right angle to the axial line of the burner head and disposing the rectilinear portion of the mixing tube at an elevation above the plane of the burner ports, a hollow casing carried by the outer end of the rectilinear portion of the mixing tube and communicating therewith and having a portion extended substantially above said rectilinear portion and above the plane of the burner ports, means for admitting primary air into said casing below the axial line of the mixing tube, and means for admitting gas into said casing at a point above the line of the burner ports, whereby the gas-air mixture must flow through the elevated mixing tube and then downwardly through the elbow portion thereof and then longitudinally through the burner head before being upwardly exhausted through the burner ports.

3. In a gas burner construction, a hollow, elongated, horizontally disposed burner head formed with upwardly opening burner ports in the top portion thereof, a mixing tube having an elongated rectilinear portion and an elbow portion, the latter being connected to and in communication with the burner head and disposing the rectilinear portion of the mixing tube parallel with and above the burner head, the outer end portion of the mixing tube being enlarged to form a chamber which depends below the axial line of the rectilinear portion of the mixing tube, means for admitting primary air into a lower portion of said chamber, and means for admitting gas into a higher portion of said chamber, the arrangement being such that the gas-air mixture flows through the elevated mixing tube and then downwardly and into the burner head for discharge in an upward direction through the burner ports.

NAPOLEON E. HILL.

OTTO J. RESS.

FRANK J. NUNLIST, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 700,020 Dennis May 13, 1902 1,080,600 Spahr Dec. 9, 1913 FOREIGN PATENTS Number Country Date 239,256 Great Britain Sept. 2, 1925

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