US 3182711 A
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May 11, 1965 w. E. ROBB NOZZLE MIXING TYPE GAS BURNER Filed March 26, 1962 mm 2 in 2 mm FN m. J/ K I! I 2 t .w 'mm 2- on mm wm wl w 1|la| 9 mm E v 5 mm INVENTOR. WENDELL E. Ross ATTORNEY 3,182,711 NOZZLE MDQNG TYPE GAS BURNER Wendell E. Robb, Tulsa, Okla, assignortoMidland-Ross orporation, Toledo, @hio, a corporation of Qhio Filed Mar. 26, 1962, Ser. No. 182,609 7 Claims. (13!. 153-109) This invention relates to gas burners and particularly to gun-type gas burners used to promote the combustible reaction of a rapidly flowing stream of air and an annular stream of fuel flowing in generally parallel flow relationship to the stream of air. More particularly, the invention relates to improved flame stabilizing means of the nozzle mixing type for stabilizing a combustible reaction of the aforesaid type.
In the operation of a gun-type burner, that is, a burner constructed integrally with a combustion air blower such as the burner illustrated in United States Patent 2,932,347 to K. S. Jaeger, a stream of air and a generally annularly shaped stream of fuel flowing in parallel flow relationship to the stream of air are combustibly reacted according to the principle of nozzle-mix combustion.
It is usual in a combustion reaction of the aforesaid type that the rate of flow of the burning mixing air and fuel exceeds the rate of flame propagation therethroughf Consequently, the flame tends to be carried away by the flowing streams which can cause the burner to pulsate. This, in turn, can be hazardous. To rectify this condition, it is common in the prior art to dispose an annular flame stabilizing member in the burner adapted to direct flame toward the point of ignition of the annular stream of fuel and the stream and air for the purpose of stabilizing the combustion reaction. The flame stabilizing members used in the prior art comprise an annular chamber adapted to receive a portion of the stream of air and a portion of the stream of fuel, facilitate the mixing of the portions of the fuel and air streams, and pass the mixed streams from a restricted outlet to be ignited by a sparking member. Thus, in the prior art, the flame from the stabilizing member would be obtained by means of premix combustion.
According to the present invention, it has been found that the combustible reaction of the main fuel and air streams can be much more smoothly stabilized by means of a flame from a stabilizing member adapted to operate on the nozzle mixing combustion principle. An appropriate stabilizing member of this type comprises an annular chamber of generally U-shaped configuration. The U is disposed generally parallel to the flow of the main stream of air with the apex upstream with respect to the direction of flow. The legs of the U preferably diverage as they proceed from the apex to form a chamber of ever increasing width. a
The U-shaped chamber is adapted to receive a portion of the air from the main stream as by means of a plurality of ports circumferentially located around the annular stabilizing member, preferably disposed parallel to the direction of flow of the main stream of air and entering the U-shaped chamber at the apex. A portion of the fuel from the fuel stream is admitted to the annular U-shaped stabilizing member from the annular fuel supply means at a plurality of circumferentially disposed points. The portions of the fuel and air streams which are admitted to the stabilizing member tend to mix therein by turbulence to form acombustible mixture; When this mixture is ignited at U ited States Patfl 3,182,711 Patented May 11, 1965 the flame front will tend to recede into the annular. U- shaped chamber to the point where the degree of mixing is adequately complete to support combustion. This is possible by virtue of the degree of openness of the chamber inherent in its U configuration. Thus, the stabilizing combustion reaction proceeds by nozzle mix combustion. Since the flame front of the stabilizing combustion reaction is within the stabilizing member rather than exterior thereto in the case of a stabilizing member operating according to premix combustion, it is more insensitive to the disturbing influences of variations in the flow of the main air and fuel streams.
For a further consideration of what is considered to be novel and inventive, attention is directed to the following portion of the specification, the drawing, and the appended claims.
' In the drawing:
FIG. 1 is an elevational sectional view of a gun-type gas burner embodying the present invention; and
FIG. 2 is an enlarged view of a fragmentary portion of the apparatus of FIG. 1.
The burner of FIG. 1 comprises annular wall means 11 defining a passage 12 having an inlet attached to blower member 13, as by means of sheet metal screws 14. The outlet of passage 12 is attached to burner mounting head 15 which, in turn, is adapted to be mounted against the firebox of a boiler, or the like, by means of annular flange 16. r
Disposed within passage 12 is a fuel supply member 17 adapted to deliver a generally annularly shaped stream of fuel to passage 12 to flow therethrough in parallel flow relationship to the stream of air delivered to passage 12 from blower 13. Fuel supply member 17 comprises a first annular wall 18 and a second annular Wall 19 circumposed about wall 18 and defining an elongate annular passage 21 which extends co-axially with passage 12. A stream of fuel is delivered to annular passage 21 from a suitable source, not shown, by means of inlet pipe 22. The upstream end of annular passage 21 is closed by means of casting member 23 and the downstream end is closed by means of casting member 24. Fuel passes from annular passage 21 into passage 12 through a plurality of circumferentially disposed ports 25 in casting member 24. Ports 25 are disposed parallel to the axes of passage 12 and annular passage 21.
Casting member 25 is'provided with wall means comprising circumferential leg members 26 and 27 which are disposed generally coaxially with each other and the axes 'of chamber 12 and annular chamber 21. Leg members 26 and 27 communicate at their origin, which is on the upstream side with respect to the direction of flow through passage 12, thereby forming an annular chamber 28 of generally U-shaped configuration.
A portion of the stream of air flowing through passage 12 is admitted to chamber 28 by means of a plurality of circumferentiall y disposed ports 29. Fuel is admitted to chamber 28, as by means of a plurailty of circumfe entially disposed ports 31 in casting member 24 which communicate chamber 28 with annular chamber 21. The streams of fuel and air admitted to chamber 28 through ports 29 and 31, respectively, tend to form afuelair mixture of a degree of homogenousness which may vary widely at various points within chamber 28. Thus, there will be a mixture of suflicient homogenousness to such as the rates of flow of fuel and/ or air or outlet pres- 7 sure.
The combustible mixture which emerges from chamber 28 is ignited by means of a spark plug 32. When once ignited the flame front of the burning mixture emerging from chamber will recede into chamber 28 by virtue of its unrestricted outlet to the point where the rate of flow of the mixing air and fuel equals the rate of flame propagation therethrough. In this regard it is desirable to construct chamber 28 of gradually increasing width by having leg members 26 and 27 diverge slightly as they proceed from the apex. Thus, the velocity of the flow of mixture through chamber 28 will decrease slightly as it proceeds toward the outlet thereby assuring that there will be a point where the velocity of flow does not exceed the rate of flame propagation in order to further safeguard against blow-off of the flame from the burning mixture. It'is also desirable in the construction of annular U- shaped chamber 28 that the leg intermediate chamber 28 and the fuel ports, i.e. leg 27 in the illustrated embodiment, by somewhat longerthan the other leg. This added length serves to prevent portions of the fuel passing from ports 31 to be drawn by localized turbulence into chamber 28 thereby unduly enriching the mixture being formed therein.
In some instances it is desirable to commence operation of a burner of this type by allowing the air to flow therethrough while slowly increasing the rate of fuel flow from a zero value. Thus, means comprising a pipe 33 are provided to admit fuel to chamber 28, or at least an arcuate portion thereof, at a rate independent of the rate at which fuel flows into chamber 28 from annular chamber 21 through ports 31.
The flame which issues from annular chamber 28 flows .through passage 12 intermediate the portion of the stream of air which is external to fuel supply member 17 and the annular stream of fuel passing from ports 25 and serves to ignite and stabilize the nozzle mixing combustible reaction therebetween. The rate of mixing of the fuel and air is increased by the turbulence imparted to the air stream by means of an annular radially extending lip 34 attached to the downstream end of leg member 26.
A frusto-conical flame diffuser member 35 is disposed downstream of annular U-shaped chamber 28 and coaxially therewith. Flame diffuser member 35 is constructed of a thin metallic wall 36. A plurality of turning vanes 37 extend inwardly from metallic wall 36 near the outlet end thereof. Vanes 3'7 impart a whirling effect to the air stream flowing through the central portion of passage 12. V
The use of a vaned diffuser in the manner described contributes to the proper shaping of the flame as is desirable in boiler firebox applications. Additionally vaned diffuser 35 has the unexpected effect of providing a secondary flame stabilizing stage. The secondary flame stabilizing stage is evidenced by an annular ring of flame of an intense blue color, which forms immediately downstream of wall means 36. This effect is probably ob- V tained by virtue of the rapid localized mixing of uncombusted fuel from ports 25 passing over wall means 36 with the swirling air from turning vanes 37.
It has been found that the axial distance of vaned diffuser 35 with respect to annular U-shaped chamber 28 has some effect on the air2fuel ratio of the burner. Thus, it is desirable to provide for adjustment of the axial distance therebetween. Thus, vaned diffuser 35 has been mounted for axial adjustment with respect to annular chamber 28. Wall means 36 is mounted to axially trav-' ersible, centrally disposed, elongate rod 38 by means of a plurality (preferably three) curved ribs 39 having an end attached to rod 38 and the other end attached to the interior surface of wall means 36. Additional supporting struts 41 may be provided for extra 'rigidity'if desired.
Rod 3% is slidably supported by means of a saddle 46 extending inwardly from wall means 18 and is biased away from blower member 13 by means of a compression spring 42 having one end abutting against pad member 43 and the other end abutting against a bearing plate 44 attached to rod 38. The end of rod 38 is threaded and retraction of the vaned diffuser is accomplished by tightening nut 45.
The above described burner may be provided with flame supervisingequipment in a known manner as a precautionary measure. Such equipment might include a flame detection rod 47 operating. in conjunction with other equipment (not shown) to energize spark plug 32 upon flame failure.
The best mode known to me to carry out this invention has been described in terms sufliciently full, clear, concise, and exact as to enable any person skilled in the art to practice the invention. However, it is understood that various modifications will be readily apparent to a skilled artisan without departing from the scope of the invention whichis defined only by the appended claims.
1. Burner apparatus comprising, in combination: first wall means forming a passage having an inlet adapted to receive a stream of air and an outlet longitudinally spaced from the inlet; second wall means disposed interiorly of the first wall means and spaced therefrom and forming an annular chamber whose axis is substantaially parallel to the axis of the longitudinal passage and which is shaped as a pair of spaced apart U-shaped portions in axial crosssection with the bight of each U-shaped portion extending toward the inlet of the passage, and each U-shaped portion being substantially unobstructed to flow as it extends away from the bight toward the outlet of the passage; annular fuel supply means disposed within the passage exteriorly of the annular chamber and adjacent and substantially concentrically thereto and comprising first port means for delivering a first portion of a fuel supply to the passage exteriorly of the annular chamber in an annular pattern with a direction of flow toward the outlet of the passage, and further comprising second port means for delivering a second portion of the fuel supply in an annular pattern to the interior of the annular chamber; and third port means for admitting a portion of the air stream flowing through the passage, to the interior of the annular chamber in an annular pattern to form a combustible mixture of air and fuel with the second portion of the fuel supply, the annular chamber being of such an extent that, when the combustible mixture is ignited, it will burn with stability therein and flame will extend therefrom to ignite and stabilize the subsequent combustible reaction between the first portion of the fuel supply and air from the remaining portion of the air stream.
2. Apparatus according to claim 1 wherein the legs of each U-shaped portion diverge from one another at least slightly as they extend away from the bight toward the outlet of the passage.
3. Apparatus according to claim 1 wherein the annular chamber circumposes the annular fuel supply means.
4.'Apparatus according to claim 3 and further comprising a lip extending radially outwardly from the outlet of the annular chamber into the passage.
5. Apparatus according to claim 1 in which the leg of each U-shaped portion of the annular chamber intermediate the annular fuel supply means and the adjacent U-shaped portion of the annular chamber is significantly longer than the other leg thereby to prevent portions of the fuel from the annular fuel supply means from being drawn into the adjacent U-shaped portion.
6. Apparatus according to claim 1 and further comprising: annular wall means forming a frusto-conical shaped diffuser disposed downstream of the annular chamber and generally co-axially therewith with the larger portion of the frusto-conical shaped member disposed away from the annular chamber; and a plurality of turn- 6 ing vanes extending inwardly from the frusto-conical 2,858,729 I 11/58 Keyes. shaped difluser. 3,022,630 2/62 McCollum 6039.72 X 7. Apparatus according to claim 6 and further compris- 3,044,537 7/62 Keating et a1. 158109 ing means adapted to adjust the axial distance between the 3,051,464 8/62 Yeo et a1. 15899 X annular chamber and the frusto-conical shaped diffuser. 5
FOREIGN PATENTS References Cited by the Examiner 305,437 2/39 Great Britain UNITED STATES PATENTS I 2 0 5 042 12 3 Berryman 15 7 X JAMES W- WESTHAVER, m y r- 2,616,258 11/52 Mock. PERCY L, PATRICK, Examiner.