US2559504A - Gas burner with internal-combustion chambers - Google Patents

Description

July 3, 1951 J. B. HENwooD GAS BURNER WITH INTERNAL-COMBUSTION CHAMBERS Patented July 3, 1951 GAS BURNER WITH INTERNAL- COMBUSTION CHANIBERS James B. Henwood, Bala-Cynwyd, Pa., assigner to Selas Corporation of America, Philadelphia, Pa., a corporation of Pennsylvania Application February 23, 1946, Serial No. 649,482

4 Claims. 1

My invention relates to the art of burning a combustible gaseous mixture, and is particularly concerned with the production of one or more gas streams consisting of highly heated products of combustion developed substantially entirely in several combustion chambers embodied in a burner.

It is an object of the invention to provide an improvement for effecting combustion of a combustible gaseous mixture in the manner just described to increase the temperature of the heated products of combustion and rate of heat liberation, whereby a burner of a given heat capacity will be of minimum size.

Another object of the invention is to provide a burner of the character described having a plurality of combustion chambers in each of which intense heating of a combustible gaseous mixture is accomplished, and discharging the highly heated products of combustion from the chambers through outlets closely adjacent to each other to produce gas streams at the desired temperatures and velocities for doing useful work.

The above and other objects and advantages of the invention will be more fully understood upon reference to the following description and the accompanying drawings forming a part of this specification, and of which Figs. 1 and 2 are end and side vertical sectional views, respectively, of a gas burner embodying the invention; Fig.

3 is a horizontal sectional view, taken on line 3 3 of Fig. 1, to illustrate the burner more clearly; and Fig. 4 is a fragmentary end sectional view, similar to Fig. 1, illustrating a modification of the invention.

Referring to the drawing, the gas burner l embodying the invention includes a base member II shaped to form an inlet chamber I 2 communicating with an inlet opening I4 formed in a nipple connection I5. The nipple connection I5 is internally threaded to receive a conduit I6 through which a combustible gaseous mixture is delivered from a suitable source of supply.

The base member II is formed with internal shoulders I1 above the inlet chamber I2 to receive an apertured member or burner screen' I8 formed with a plurality of openings or passages I9.

To the top surface of the base member I I is secured a slotted clamping plate 20, as by screws 2|, for example, which overlies flanges or lugs 22 formed at opposing sides of the apertured member I8. In order to obtain a gas-tight seal about the burner screen I8, a gasket 23 formed of suitable material, such as asbestos, for example, is interposed between the plate 20 and base mem- 2 ber II. The spaces 24 above the lugs 22 may be filled with a suitable high temperature fire-brick cement.

The open end of a cup-shaped metal shell or casing 25 is removably secured at 26 to the base member II. Within the metal shell 25 is provided an outer wall or lining of refractory material. The outer refractory lining is formed by a hollow rectangular shell comprising two complementary wall parts, U-shaped in horizontal section, and each having parallel ends 21, as shown in Fig. 3. The extreme vertical edges of the opposing ends 21 of the outer refractory lining are in abutting relation, as indicated at 28 in Fig. 3.

The closed ends or side walls 28 of the U-shaped parts forming the outer refractory lining, at the other outer surfaces thereof, conform to the shape of the metal shell 25. The inner surfaces of the ends 21 are straight throughout the heights of these walls, as shown in Fig. 2. The inner surfaces of the side Walls 29 include straight wall portions 30 extending upwardly from the clamping plate 20 to an intermediate part of the outer refractory lining, and inwardly sloping wall portions 3I terminating at the upper part of the metal shell 25, as best shown in Fig. 1.

A second inner refractory wall or lining is disposed withn the outer refractory lining just described to form a centrally disposed combustion chamber 32 and smaller combustion chambers 33 at each side of the chamber 32. The inner refractory lining is also formed by a hollow rectangular shell comprising two complementary Wall parts, U-shaped in horizontal section, and each having parallel ends 35 over which snugly lit the ends 21 of the outer refractory Wall parts, as shown in Fig. 3. The extreme vertical edges of the opposing ends 35 of the inner refractory wall parts are in abutting relation at 36, as shown in Fig. 3.

'I'he inner surfaces of the ends 35 of the inner refractory wall parts are straight throughout the heights of these walls, as seen in Fig. 2. The closed ends or side walls 31 of the U-shaped parts forming the inner refractory lining include straight wall portions 38 extending upwardly from the burner screen I8 substantially the same distance as the straight inner wall surface portions 39 of the outer refractory lining, and inwardly sloping wall portions 39 terminating in a narrow rectangular-shaped slot or discharge orifice 40 projecting or extending through an opening at the top part of the metal shell 25.

It will be seen that the inner surfaces of the straight wall portions 33 of the inner refractory lining are vertically ribbed. as shown most clearly in Fig. 2, to increase the surface area presented by these portions of the inner refractory lining. The side walls 31 of the inner refractory wall parts are slotted at the upper ends thereof at 4I, such slots extending across the closed sides 31 of the wall parts and being inclined upwardly;

The bottom edges of the inner refractory 1ining rest directly upon imperforate portions of the burner screen I8, the ends 35 fitting snugly in shoulders 42 and the closed sides 31 tting .in U-shaped recesses 43 extending lengthwise of the burner screen I8. as shown in Figs. 1 and 2, respectively. In this way the side walls 31 of the inner refractory lining are held in spaced relation with the side walls 23 of the outer refractory lining to form the combustion spaces 33 therebetween. In order to rigidly hold the spaced apart side walls of the inner and outer refractory wall parts in spaced relation, the side walls 31 of the inner refractory lining are formed with vertically extending raised portions 44 of the shape shown in Fig. 3, which butt against both the straight wall portions 30 and sloping wall portions 3| of the side walls 29 of the outer refractory lining.

The U-shaped parts forming the inner refractory lining are provided at their upper ends with flanges 45 extending into and tting in notches or recessed portions formed at the top edges of the side walls 29 of the outer refractory lining. Each of the flanges 45 is formed with a plurality of recesses at its top surface in alignment with threaded openings formed in the outer metal shell 25 to receive locking or retaining screws 46. l

In order to retain the inner and outer refractory linings rigidly in position within the outer metal shell 25 so that each inner wall part is snugly nested within an outer wall part, the outer refractory lining is fixed to the inner surface of the shell 25a by a coating 41 of a suitable high temperature fire-brick cement. The flanges 45 of the inner refractory lining are also fixed at 4l to the recessed portions of the outer refractory lining by such high temperature cement, as shown in Fig. l. Likewise, the abutting vertical ,edges of the ends 21 and 35 of the outer and inner refractory linings, respectively, may be united by high temperature cement. The recesses formed at the top surfaces of the flanges 45 are also filled with high temperature fire-brick cement. which, after hardening, firmly anchors the screws 46 in position.

When it is desired to employ the burner I for applying heat to work. a combustible gaseous fuel mixture is supplied thereto through the conduit I6 from a suitable source of supply. Such mixture may comprise ordinary city gas, natural gas or the like, and a combustion supporting gas, such as air or a mixture of air and oxygen, for example. When the burner I0 is relatively cool Aand at the temperature of the surroundings, the gaseous mixture supplied thereto passes through the inlet chamber I2. burner screen I8 and chamber 32 from which it is discharged through the outlet or discharge orice 40. The gas mixture in the smaller chambers 33 is discharged therefrom through the slots 4I and merges with the gaseous mixture discharged from the central chamber 32.

The gaseous mixture is initially supplied to the burner I0 at a relatively low pressure, such as a pressure equivalent to or 6 inches of water col- 4 umn, for example, so that the gaseous mixture discharged from the outlet 40 can be ignited to produce and maintain a llame at this region. When the ame is being maintained at the discharge orice 40, the pressure of the gaseous mixture supplied to the burner I0 is then reduced sufficiently to cause the flame to backfire from the discharge orifice 40 onto the burner screen I8 in chambers 32 and 33. When this occurs a plurality of flames are produced and maintained at the upper ends of the openings I9 communicating with each of the chambers 32 and 33.

When the flames are being maintained within chambers 32 and 33 at the top of burner screen I3 the pressure of the gaseous mixture supplied to the burner may be increased. After a short interval of time the flames maintained at the top surface of the burner screen I8 which project into chamber 32 ell'ect such heating of its inner refractory lining that the latter is heated to a high incandescent temperature. Similarly, the llames produced at the upper ends of openings I9 which communicate with the smaller chambers 33 effect such-heating therein that the outer surfaces of the side walls 31 and inner surfaces of the side walls 29 are also heated to a high incandescent temperature.

Due to heating of the refractory wall surfaces defining the chamber 32 and 33 to a high elevated temperature, complete combustion of the gaseous mixture is accomplished in chamber 32 before the mixture reaches the discharge orifice 40, and complete combustion of the gaseous mixture is accomplished in chambers 33 before the gaseous mixture reaches the slotted outlets 4 I Although not to be limited thereto, it is my belief that the gaseous mixture itltroduced into the combustion chambers 32 and 33 is subjected to intense heat radiated from the highly heated inner wall surfaces of these chambers to effect substantially complete burning of the gaseous mixture within the chambers before being discharged therefrom.

The high temperature gases passing through the outlets 4| of the smaller chambers 33 merge with the heated gases being discharged from the central chamber 32. From the outlet 40 is discharged a high velocity jet or stream of heated gases consisting substantially entirely of the heated products of combustion formed in chambers 32 and 33.

It is desirable in gas burners like that illustrated and just described to discharge the heated products of combustion at a maximum velocity and at the highest temperature possible. This is so because the rate of heat transfer effected by the gas stream discharged from the burner at the outlet 40 is dependent upon the temperature of the heated gases forming the gas stream as well as the rate at which the gases are delivered'from the refractory lined combustion chambers 32 and 33 embodied in the burner. In order to achieve this end it is necessary to give up to the heated products of combustion substantially all of the heat liberated in the combustion chambers 32 and 33 and to reduce to a minimum the loss ci heat through the walls of the combustion chambers.

In accordance with the present invention this is accomplished by providing the central combustion chamber 32 in which the major portion of the combustion gaseous mixture is burned, and thermally shielding such central chamber by the smaller combustion chambers 33 at opposite sides thereof. Since the outer surfaces of the longer side walls 31 of the inner refractory lining are heated to a highly radiant condition, the temperature di'erential across the side walls 31 is maintained at a minimum and the heat loss from the high temperature gases in the central chamber 32 is effectively retarded.

The side chambers 33 are appreciably smaller than the centrally disposed chamber 32 and the inlets thereof are provided with fewer passages I9 than the inlet for the central chamber 32. Hence, the rate at which the gaseous mixture is supplied to the side chambers 33 is considerably less than that at which the mixture is supplied to the central chamber 32. However, the crosssectional areas of the chambers 33 are made sufliciently small and properly related in size to the rate at which the gaseous mixture is normally supplied thereto through the openings I9, so that the inner refractory surfaces thereof can be readily heated to and maintained at a high incandescent temperature.

In order to keep the heat loss from the heatedv gases in the side chambers 33 at a minimum, the refractory wall parts providing the outer refractory lining are preferably formed of refractory material possessing poor thermal conducting properties as well as the ability to withstand thermal shock over a wide temperature range.

Since the chamber 32 is more effectively shielded from the surroundings than the side chambers 33, the gases can be heated to and maintained at the higher temperature in chamber 32 than in chambers 33. Even though the gases in chambers 33 are not heated to ashigh a temperature as in chamber 32, this is more than compensated by the fact that a major portion of the heated gases are developed in the central chamber 32 and heated to the highest possible temperature with minimum heatl loss. This enables the gaseous mixture to be burned at the highest possible rate in chamber 32 and contributes to the production of a gas stream of heated products of combustion which is discharged at the outlet 40 at an extremely high temperature and velocity to promote rapid transfer of heat to -work adapted to be heated.

While the heated gases developed in the side chambers 33 are not at the 'same high temperature as the heated gases developed in chamber 32, nevertheless such gases are at an elevated temperature approaching the temperature of the gases discharged from chamber 32. In order to utilize the highly heated gases formed in chambers 33 and produce a gas stream at the outlet 40 which is at a maximum velocity and capable of optimum heat transfer to work, the heated gases in chambers 33 are discharged through the outlets II so that such gases will merge with the heated gases passing from chamber 32. Since less than a major portion of the heated gases are developed in the side chambers 33, such gases will not unduly lower the temperature of the highest temperature heated gases formed in the central chamber 32.

By way of example only, the refractory wall parts providing the outer refractory lining may be formed of aluminum oxide. A refractory of this type possesses good insulating propertes and resistance to thermal shock. Such a refractory preferably is of desired porosity so that it will have adequate strength to serve as the outer refractory lining and stand up under the uses normally encountered by a gas burner like that just described. Although not to be limited thereto, the burner screen I8 and inner refractory lining may be formed of beryllium oxide, for example, because of its high resistance to thermal shock and rigidity and strength at high temperatures.

In the usual type of gas burner producing a bright and luminous flame burning in the open, the burner is usually positioned with respect to the work to be heated so that the tip of the flame, which is the region at the highest temperature, impinges the surface of the work. In gas burners operating with such a bright and luminous flame in the open, combustion or burning of the gas mixture takes place in the open. Under these conditions, combustion of the gas mixture is not taking place at the highest possible temperature because the heat liberated by the combustion reaction is given up to the cooler surroundings.

The burner l0 of the invention is characterized by the absence of a bright and luminous flame during normal operation of the burner. It is only when the burner I0 is first started that a flame is momentarily maintained at the elongated slot or discharge orifice 40, as previously explained. After the gas mixture has once been ignited, the gas delivery pressure is reduced sufliciently to cause backlring into the chambers 32 and 33, so that burning of the gas mixture will take place at the top surface of the burner screen I8.

Each of the burner flames initially produced at the upper surface of the burner screen i8 conslsts of an inner cone of unburned gaseous fuel and combustion supporting gas and an outer cone constituting the portion of the flame in which the combustion reaction is taking place. When operation of the burner I0 is first started and the inner refractory linings are relatively cool, the inner cones of the individual flames extending onto the combustion chambers 32 and 33 are relatively long in length. As the inner refractory linings become heated, the inner cones of the individual flames become increasingly shorter and shorter. When the surfaces of the inner refractory linings become heated to a high temperature approaching incandescence, thc inner cones of the individual flames become appreciably shorter from their original` lengths when initially produced. Under normal operating conditions, when the inner refractory linings reach a highly incandescent condition, it has been observed that the inner cones practically disappear and are not distinctly visible when the lower end of combustion chamber 32 is viewed through the opening 40.

The burner i0 is characterized by the maintenance of such combustion conditions in chambers 32 and 33 that rapid flame propagation is accomplished. By effectively shielding and insulating the central chamber 32, in which a major portion of the gaseous mixture is burned so that the combustion reaction may be carried out at an increased temperature, the delivery pressure of the gaseous mixture to the burner may be increased. Further, the thermal shielding of the central chamber 32 promotes combustion of slow burning gases, such as natural gas, for example, under increased delivery pressure of the gaseous mixture to the burner.

The combustion of the gaseous mixture is effected substantially entirely within the combustion chambers 32 and 33 and heated products of combustion are discharged from the outlet 40 at an elevated temperature of 3200 F., and higher when a gaseous mixture of air and ordinary gas and the like is employed. Since the theoretical flame temperature of gas mixture of air and ordinary gas, such as city gas, is about 3700" F., it will be evident that a gaseous source of heat is made available by the burner i of the invention which is at a temperature approaching theoretical ame temperature.

Since the gas mixture is introduced into the combustion chambers 32 and 33 at a temperature of about 70 F. and heated to a temperature of 3200 F. and higher, the gases expand at least seven fold and at a rate directly proportional to increase in absolute temperature. Since combustion of the gaseous mixture is accomplished substantially entirely Within the combustion chambers 32 and 33, and the gases undergo considerable expansion, as just pointed out, any increase in the gas mixture delivery pressure consistent with the intended mode of operation of the burner effects an enormous increase in the rate at which the heated gases are discharged from the chambers 32 and 33.

Burners like the burner l0 have been successfully used with gaseous mixture delivery pressures up to lbs. per square inch. In burners generally similar tothe burner Il! and having an outlet slot or discharge orifice 2" x la", and operating at a gaseous mixture delivery pressure of about 5 lbs. per square inch, it has been observed that the heated gases issue from the outlet at temperatures of 3200 F. and higher. In addition, tests which have been made indicate that vthese heated gases, consisting substantially entirely of heated products of combustion, are discharged from the burner at an average velocity of about 900 feet or more per second and at a maximum velocity of about 1300 feet or higher per second. Burners of this type have been operated experimentally at delivery pressures of gaseous mixture in excess of 5 lbs. per square inch and have produced high temperature gas streams at correspondingly higher temperatures and increased velocities.

An important operating characteristic of the burner I0 is that the combustion chambers 32 and 33 are maintained above atmospheric pressure during normal operation of the burner due to the provision of the restricted outlets 4I! and 4 I This is of considerable importance in promoting rapid flame propagation and electing a high rate of combustion of the gaseous mixture. By providing a burner l0 like that just described and illustrated having a central chamber 32 in which a major portion of the combustible gaseous mixture is burned and which is thermally shielded by the side chambers 33, the heat capacity or output of a given size burner may be increased as much as fifty per cent.

A modification of the invention is illustrated in Fig. 4 which is generally like the embodiment just described and shown in Figs. 1 to 3 and differs therefrom in that the outlet 41a of one of the smaller chambers 33 extends to the extreme upper end of the burner and terminates at a. region closely adjacent to the outlet 40. The outlet 4ib of the other smaller chamber 33 extends through the upper part of the side wall 29 associated therewith and terminates at the side of the cup-shaped casing at a region removed from the outlet 40.

In the embodiment of Fig. 4 the central chamber 32 is thermally shielded from the surroundings by the smaller combustion chambers 33 in the same manner as in the embodiment first described. However. all of the highest temperature heated gases are separately discharged from the chamber 32 through the outlet 40 to form a 8 first high velocity jet. charged through the outlet 4 la form a second jet which preferably merges with the jet produced at the outlet at the exterior of the burner l0 and directed against closely adjacent regions of y work to be heated.

The highly heated products of combustion of the second jet discharged at the outlet 41a are at a temperature below the temperature of the gases of the first jet discharged at the outlet 40. Further, by providing an outlet 41af which is only slightly restricted with respect to the cross sectional area of the chamber 33 associated therewith, the velocity of the gas stream at the outlet lia may be appreciably reduced with respect to the velocity of the first jet discharged atjthe outlet 40.

While several embodiments of the invention have been shown and described, it will be obvious to thoseY skilled in the art that various modifications and changes may be made without departing from the spirit and scope 0f the invention, as pointed out in the following claims.

What is claimed is:

1. A burner comprising structure including a hollow body, partitions extending across the interior of said hollow body from one end to the other thereof to divide said body into a plurality of individual and substantially closed combustion chambers alongside of each other, one of said chambers being of greater size and centrally disposed between two smaller chambers, said chambers having means forming inlets at one end adjacent to one another and means forming outlets at the opposite end, said inlet forming means each having a number of small passages for subdividing into a plurality of gas streams a combustible gaseous mixture adapted to be supplied thereto under pressure, said chambers having their outlet forming means and inner wall surfaces formed substantially entirely of high temperature refractory material so that combustion of the gas streams may be effected within said chambers and cause heating of the inner wall surfaces thereof to incandescence and produce regions of intense heat in each of which substantially complete combustion is accomplished, the outlet forming means for the large chamber being adjacent to the outlet forming means for the smaller chambers so that the heated gases discharged from the latter merge with the heated gases discharged from the larger chamber.

2. A burner as set forth in claim l in which the inlet for the larger central chamber is provided with a greater number of passages than the other chambers so that a major portion of the gaseous mixture is burned in the larger chamber.

3. A burner comprising structure forming a chamber having an inlet at one end, an outlet at the other, a perforated refractory part across said inlet, said part being provided on the side toward the chamber with a pair of parallel grooves, a. pair of partition members in said chamber to divide said chamber into a plurality of sections, one end of each of said partition members being received in one of said grooves and the other end of each partition member being located at one side of said outletl means to hold the said other ends of said partitions in position, and said partition members each being provided with an opening adjacent to said other Y end whereby the sections of said chamber are in communication with each other only adjacent to said outlet.

4. A burner comprising in combination a pair The heated gases disl of complementary substantially shell-like refractory members cooperating to form a combustion chamber larger at one end that at the other. the large end being the inlet and the small end being the outlet, a perforated refractory part one side o1' which engages the ends of said members to close said inlet, a second and smaller complementary pair of shell-like refractory members received in the chamber to divide the chamber into three sections, one end of each o! said second pair of members engaging said part andthe otherA end of said second pair of members extending into said outlet in spaced relation, means to hold said second pair of members in xed relation to said rst-mentioned pair of members, and means forming a space on the opposite side of said part from the side engaging said members into which a combustible mixture may be forced to flow through 'said part into the sections of the combustion chamber to be burned.

JAMES B. KENWOOD.

140 REFERENCES crrED The following references are of record in the tile of this patent:

UNITED STATES PATENTS

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