NZ195194A - Elongate gas burner with diffuser and nozzle at an angle - Google Patents

Description

♦ m 195194 i i ivi b. ^ 1-.^ O wy * ••aaitB«aaaBc#«aa»c CompfsCo SpecrScsis-cn Filed: $.'!$;?P\ ; r*I■!&**• ■1P-9J1' MAY 1984 F2*> PIH"(c6 "tcbi3CSi.*'on Date: • •» ^ r», -JV0'. ■ < ' iiss" NEW ZEALAND COMPLETE SPECIFICATION Patents Act 1953 IMPROVEMENTS IN OR RELATING TO GAS BURNERS C_ .C We, PYROX LIMITED, of 463-467 Warrigal Road, Moorabbin, Victoria, -0^©tT; Australia, hereby declare the invention for which we pray that a patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement: HF 195194 The present invention relates generally to gas burners and is particularly applicable to elongate burners having a burner head comprising one or more rows of flame ports. Such elongate burners may be used for example, in ovens, grills, room heaters, central heaters and heat exchangers.

It is well known that different types of gases exhibit different burning and other characteristics. For example, natural gas has a lower burning velocity and is more difficult to light than town gas. As a result, a natural gas flame is generally prone to lift-off whereas a town gas flame is generally prone to light back. While high flame-port velocity may assist in alleviating the light-back of town gas it aggravates the problem of lift-off with natural gas. L.P.G. gas on the other hand presents its own problems.

The majority of elongate burners sold in.Australia at present, are for use with natural gas, although there is also a need ror burners capable of utilizing other gases, particularly L.P.G. A number of proposals have been put forward for overcoming the problems associated with a particular gas. However, it would be preferable to provide a single burner suitable for use with a number of different gases supplied at different pressures. Such a burner should preferably be economical to manufacture and install.

Accordingly, the present invention provides a gas burner including a waisted inlet portion and a combustion portion; the inlet portion having a nozzle part converging from an open mouth to a narrowed throat portion and having a diffuser part diverging from the throat portion to an N.Z. PATENT OFFICE 2 5 JAN 1984 cation with said entry port, and a plurality of flame ducts leading from said burner manifold to a plurality of flame ports, said flame ports being arranged in one or more rows to form a burner head; wherein the diffuser part has a straight longitudinal axis in the region of the throat portion and the said straight longitudinal axis of the diffuser part and a longitudinal axis of the nozzle are angled with respect to one another; and wherein gas injected into said mouth mixes with air drawn into the inlet portion and the combustion mixture so formed passes through said entry port into the manifold and via said flame ducts to said burner head.

The diffuser part is preferably considerably longer than the nozzle part. The ratio of the respective lengths of the diffuser and nozzle parts is preferably between 1.5:1 and 5:1 and most preferably about 3:1.

The entry port and throat are preferably substantially circular while the mouth is preferably circular, substantially oval or egg-shaped with the elongation extending downwardly. The respective areas of the openings at the mouth and entry port are preferably similar and considerably larger than the corresponding area at the throat.

The longitudinal axes of the nozzle and diffuser parts are at an angle a with respect to one another.

The term "angle a" is used herein to mean the acute angle formed between an extension of the longitudinal axis of the diffuser part and the longitudinal axis of the nozzle part.

The longitudinal axis of the diffuser part extends from the centre of the throat to the centre of the entry port while the longitudinal axis of the nozzle part extends N.Z. PATENT OFFiCE 3 2 5 JAN 1984 195194 from the centre of the mouth to the centre of the throat.

Preferably, the angle is not more than 2 5° and most preferably is around 5°. Preferably, the centre of the mouth is below that of the throat so that the nozzle part may be considered as being skewed downwardly relative to the throat and diffuser part.

The angle between the parts, the angle of flaring of the nozzle part and the shape of the mouth are preferably such that when projected along the longitudinal axis of the diffuser part, the throat falls wholly within the mouth.

In use the gas is fed into the mouth from an injector orifice as is well known in the art. The orifice is preferably coaxial with the throat and may be positioned on the extension of the longitudinal axis of the diffuser part. This arrangement is found to provide very good mixing of gas and primary air within the inlet portion to form the combustion mixture. It is believed that the good mixing is due to turbulence created within the inlet portion due to the skewness of the mouth and nozzle relative to the throat and diffuser.

The combustion portion also includes a burner manifold which may be elongated and is preferably substantially rectangular. The manifold preferably comprises a single chamber which is free of internal divisions, baffles or compartments. Combustion mixture passing into the burner manifold through the entry port should preferably be able to move freely within the burner manifold to facilitate mixing and create a substantially even pressure throughout the burner manifold.

The combustion portion also includes a plurality HF 195194 of flame ducts each leading from the burner manifold to a flame port. Preferably the flame ducts are formed in an elongated slot extending upwardly from the burner manifold to the burner head. The slot may extend along substantially the entire length of the manifold. The slot may be divided into a plurality of flame ducts by ridges in at least one of the opposed walls of the slot. The ridges extend across the slot toward the opposite opposed wall. Preferably, each ridge abuts the opposite wall of the slot. Either or both side walls of the slot may carry one or more of such ridges.

The ridges may be spaced apart such that the ducts and ports so formed vary in size. Preferably there are two sizes of ducts and each duct is preferably of constant cross-section throughout its length. Each of the larger or main ducts leading to a main port is preferably adjacent a smaller or retention duct leading to a retention port. Most preferably main and retention ports alternate along the head of a ribbon-type burner. The cross-sectional area of each main port is preferably not less than twice the cross-sectional area of each retention port. As a result of this size difference, combustion mixture flows more slowly through the retention ducts. Hence the flame at each retention port will be lower than at each main port. This difference in flame height serves to alleviate flame lift-off at main ports adjacent small retention ports.

Most preferably, the ridges dividing the slot into ducts extend alternatively from opposite side walls of the slot.

Preferably, the ridges projecting from one wall of liz. ?A7Ziy HF -5- * 12FEBM • .. 195194 the slot are evenly spaced but off set relative to those projecting from the other wall of the slot whereby to form a burner head having an alternating series of main ports and retention ports.

The ridges may each extend from the manifold to the outer edge of the slot whereby each duct is in the form of a bore extending from the manifold to a port at the head of the burner.

The burner of the invention may also include an igniter portion. The igniter portion may be particularly useful for igniting the combustion mixture at the flame ports when the main ports are not readily accessible, e.g. when they are located within a heat exchanger.

The igniter portion may include an igniter manifold for distributing gas to one or more igniter ducts each leading to an igniter port. The igniter manifold may be in direct communication with the burner manifold preferably in the vicinity of the entry port. Communication between the burner and igniter manifolds may be via a supply channel which restricts the flow of the combustion mixture from the burner manifold into the igniter manifold. Thus the combustion mixture in the igniter manifold is preferably at a lower pressure than that in the burner manifold. The igniter manifold is preferably narrower than the burner manifold and may be conveniently formed as a groove in one of the two halves of the burner. An igniter manifold so formed may be substantially semi-circular in cross-section.

The igniter ducts may be formed by one or more ridges in each of the side walls of a slot communicating with the igniter manifold as described above in relation to the HF N.Z. PATENT OFPiCE 2 5 JAN 1984 I Q ^ 1 Q / I 7 j i ; M- flame ducts.

The igniter ports may be arranged in a row extending from an accessible position for lighting to a position adjacent one or more flame ports. Each igniter port should preferably be spaced from its adjacent ports such that by igniting the combustion mixture at one end of the line of igniter ports the flame may run along the line and ignite the main part of the burner head, i.e. the flame ports.

If desired, a tap or similar shut-off device may be provided to shut-off the igniter ports once the flame ports are ignited. Such device may be conveniently positioned in the supply channel. However, for ease of manufacture the igniter ports may receive a continuous supply of combustion mixture. The supply may be restricted by the size of the supply channel and the amount of mixture consumed^-may also be kept to a minimum by making the igniter ducts relatively small. Conveniently the igniter ducts and ports are all one size which may be smaller than that of the retention ports, preferably in the ratio of about 1:2.

The burner may be conveniently formed from two pieces of sheet material. Each sheet is preferably substantially rectangular. The sheets may be pressed to form one half of the inlet portion, burner and inlet manifolds,ridges and other features of the finished burner. The two parts may be joined by rivetting, spot welding or other known methods to form the finished burner.

The joins may be effected in the unpressed or body portions of the burner. The body portions are those portions of the sheet which remain substantially unchanged during the N.Z. PATEmr OFFICE JAN 1984 195194 above described pressing operation. The body portions thus form flanges which extend substantially around the periphery of the burner. One flange extends along the lower edge of the burner and across the end remote from the mouth. The flanges along the upper edge of the burner are preferably formed so as to extend in a direction substantially normal to the side walls of the slot whereby in cross-section the side walls of the slot and the flanges form a "T" at the burner head. Such outwardly extending flanges form a shield which shields the flame from upward currents of secondary air travelling over the burner toward the flame. Such a draught of secondary air may aggravate flame lift-off but the shield flanges at the burner head alleviate this problem.

The body portion may also assist in positively locating the burner opposite the orifice of the injector and, in a furnace for example, relative to a heat exchanger. The end remote from the mouth may be conveniently located by positioning the flange in a slit or V-shaped holder.

Preferably the burner should be arranged in use so that the throat and injector orifice are substantially coaxial. The diffuser and burner manifold are also preferably coaxial about the same longitudinal axis as the throat and injector orifice. As described above, the mouth is preferably off-set downwardly relative to this longitudinal axis.

Throughout the specification the burner of the invention has been described in the preferred orientation in which the burner head and flame ports extend along the top of the burner. The drawings show a burner according to the invention in this orientation. It is to be appreciated however, that in use a burner according to the invention may be used in FstHotewr HF -8- T" E25EBI98I 195194 other orientations depending upon the particular application.

The burner may be conveniently formed from stainless-steel, vitreous enamelled steel or other materials known in the art to be suitable for burner manufacture. Conventional pressing and rivetting or spot-welding techniques may be used to form burners according to the invention.

In one particularly preferred arrangement, the two sides of a burner are formed in a single piece of sheet material which is folded preferably along the lower edge and then joined by rivetting or spot-welding to form the burner.

The present invention thus provides a burner which may be economically manufactured from sheet materials by pressing and joining operations without forming any holes in the material. Hence sharp edges which may collect fluff or otherwise interrupt the free flow of gases within the burner are avoided.

The burner provided by the invention has been found suitable for use with a wide variety of gases including natural and L.P. gas and it provides efficient mixing which results in substantially complete combustion. An economical igniting means may also be provided in accordance with the invention and the burner may be conveniently located via the flanges of sheet materials. The burner may be narrow and suitable for use in confined spaces, e.g. with a narrow heat exchanger of the type used in a domestic wall furnace. The burner also provides for substantially even pressure distribution along the line of flame ports.

In order to enable a clearer understanding of the invention the attached drawing illustrates an example embodiment of the invention. In the drawings: ~ = t •.. rEB si-Si HF -9- 195194 Figure (1) shows a plan view of an elongated burner according to the invention; Figure (2) shows a side view of the burner; Figure (3) shows a sectional view AA through the burner at A in the direction indicated by arrows; and Figure (4) shows a sectional view BB through the burner at B in the direction indicated by arrows.

The preferred embodiment illustrated is formed from a single piece stainless-steel sheet material. The two portions 1, 2 are joined along the lower edge of the burner. A row of flame ports extends along the upper edge. The main ports 4 are each separated by a smaller retention port 5 for retaining the root of the main port flames to the burner and alleviating lift-off. Shields 6, 7 extend along the upper edge of the burner and shield the flames from direct draughts caused by upwardly moving currents of secondary air.

The main ducts and retention ducts leading respectively to the main ports 4 and retention ports 5 are separated from each other by ridges 8 which are formed alternately in one of the two portions and extend across the slot to the other portion.

The gas/air combustion mixture which is fed to flame ports 4, 5 from burner manifold 3, enters the burner through mouth 9 passing along nozzle part 10 through throat 11 and diffuser part 12 to burner manifold 3.

Throat 11, diffuser part 12 and burner manifold 3 are substantially symmetrical about longitudinal axis 13.

However, the longitudinal axis 18 of nozzle part 10 is angled downwardly toward the bottom edge of the burner. The angle0*-between the two axes is of the order of 6°. For maxmuiiu."^-"'"^; HF -10- ;v_ 195194 efficiency gas is preferably fed into the burner substantially along longitudinal axis 13. mixture from burner manifold 3 via supply channel 15. Igniter manifold 14 is formed as a groove in portion 2. A series of ridges 16 extend from igniter manifold 14 to the shield 6, 7 to form igniter ducts which open at the head of the burner as igniter ports 17.

Thus, a small flame ignited at C extends along the row of igniter ports 17 to D to ignite flame ports 4, 5.

Finally, it is to be understood that various alterations, modifications and/or additions may be introduced into the constructions and arrangements of parts previously described without departing from the spirit or ambit of the invention as defined by the appended claims.

Igniter manifold 14 receives the gas/air combustion HF 195194

Claims (12)

WHAT WE CLAIM IS:

1. A gas burner including a waisted inlet portion and a combustion portion; said inlet portion having a nozzle part converging from an open mouth to a narrowed throat portion and having a diffuser part diverging from said throat portion to an entry port leading into said combustion portion; said combustion portion including a burner manifold in communication with said entry port, and a plurality of flame ducts leading from said burner manifold to a plurality of flame ports, said flame ports being arranged in one or more rows to form a burner head; wherein the diffuser part has a straight longitudinal axis in the region of the throat portion and the said straight longitudinal axis of the diffuser part and a longitudinal axis of the nozzle are angled with respect to one another; and wherein gas injected into said mouth mixes with air drawn into the inlet portion and the combustion mixture so formed passes through said entry port into the manifold and via said flame ducts to said burner head.

2. A gas burner according to claim 1 wherein a slot extending along the burner manifold is divided into a plurality of flame ducts by ridges in at least one of the opposed walls of the said slot, extending across said slot toward the opposite opposed wall whereby to divide said slot into a plurality of flame ducts.

3. A gas burner according to claim 2, wherein said ridges are spaced apart such that the flame ducts and flame ports so formed vary in size with larger or main ports being adjacent smaller or retention ports.

4. A gas burner according to claim 3, wherein the cross-sectional area of each main port is not less than twice the cross-sectional area of each retention port.

5. A gas burner according to any one of claims 2 to 4 -12- N.2. PATENT or :. 25 JAN 1984 195194- wherein the ridges projecting from one wall of said slot are evenly spaced and off-set relative to those projecting from the other wall of said slot whereby to form a burner head having an alternating series of main ports and retention ports.

6. A gas burner according to any preceding claim wherein ratio of the length of the diffuser part to the length of the nozzle part is between 1.5:1 and 5:1.

7. A gas burner according to any preceding claim wherein the angle (as herein defined) is not more than 25 degrees.

8. A gas burner according to any preceding claim wherein said nozzle is skewed downwardly relative to the throat and diffuser part.

9. A gas burner according to any preceding claim# which further includes an igniter portion comprising an igniter manifold for distributing combustion mixture to a row of igniter ducts each leading to an igniter port said igniter ports extending in a row from said burner head toward said mouth whereby a flame established at the mouth end of the row of igniter ports runs along the row and ignites the combustion mixture issuing from the flame ports whereby to ignite the burner.

10. A gas burner according to any preceding claim wherein a flange extends along the length of the burner nead at each 6ide thereof, each flange projecting outwardly away from the flame ports so as to deflect upward currents of secondary air away from said burner head.

11. A gas burner according to any preceding claim formed by stamping or pressing the outline shape of the burner components in a single piece of sheet material. HF -13- 195194 folding said sheet to align complementary component parts and securing the folded portions to one another by welding, rivetting or other securing means whereby to form said burner.

12. A gas burner according to claim 1 substantially as hereinbefore described with reference to the accompanying drawings. PYROX LIMITED by their attorneys BALDWIN SON & CAREY HF -14-