US3363663A - Combustion chamber burner and a method for its operation - Google Patents

Description

Jan. 16, 1968 w, PORTER 3,363,663

COMBUSTION CHAMBER BURNER AND A METHOD FOR ITS OPERATION Filed June 7, 1965 v 4 Sheets-Sheet 1 WILLIAM E PORTER INVENTOR.

Bydrfw (Md flaw A TTORNEY Jan. 16, 1968 Filed June 7, 1965 W. F. PORTER COMBUSTION CHAMBER BURNER AND A METHOD FOR'ITS OPERATION 4 Sheets-Sheet 2 FIG. 3

WILL/AM F. PORTER INVENTOR,

ATTORNEY 4 Sheets-Sheet 5 WILL/AM F. PORTER INVENTOR.

ATTORNEY Jan. 16, 1968 w. F. PORTER COMBUTION CHAMBER BURNER AND A METHOD FOR ITS OPERATION Filed June 7, 1965 I mlllllllllill FIG. 4

Jan. 16, 1968 w. F. PORTER 3,

COMBUSTION CHAMBER BURNER AND A METHOD FOR ITS OPERATION Filed June '7, 1965 4 Sheets-Sheet 4.

W/L LIAM E PORTER INVENTOR.

A TTORNE Y United States Patent Ofilice 3,363,663 Patented Jan. 16, 1968 ABSTRACT OF THE DECLOSURE A burner is provided which has a substantially closed combustion chamber defined by steel walls, a constricted discharge passage and is substantially filled with rounded refractory bodies larger than said passage. The burner is ignited and the bodies brought to about 1500 F. on a rich gas-air mixture; then operation is at superatmospheric pressure with ISO-170% of the amount of air required for complete combustion. Discharge is a blast at high temperature and velocity.

This invention relates to a burner, and more particularly to an enclosed burner for discharging a high velocity, high temperature stream of gas obtained by the combustion of premixed fuel and oxidant.

A burner of this type will be found to be useful in those applications where gases of high temperature and velocity are desired, such as welding, brazing, heat treating of metal, glass working and the formation of glass fibers.

Burners for these applications achieved quick ignition and extremely rapid combustion of the fuel by providing the burner chamber with a refractory lining which is heated to incandescence during operation. The hot surface ignited the incoming fuel-air mixture and radiation from the incandescent refractory caused the combustion to be complete within the burner chamber. This refractory lining has proved rather fragile, sometimes lasting only a matter of days; careful design and workmanship have improved the situation somewhat but better burners are needed.

It is an object of this invention to provide a burner which is highly resistant to mechanical shock and to thermal shock.

It is a further object of this nvention to provide a burner in which there are a minimum of critical assemblies, and in which the difierential expansion between parts, during heat-up and cooling, and during start-up and shut-down, will be eliminated as a source of ditficulties.

It is the object of this invention to provide a burner design which imposes a minimum of restrictions on phys ical shape of the burner and on nozzle location. The burner may be elongate in shape for heating a small confined area; it may be adapted to supply heat to a long and narrow work piece without interruption; it may be in the form of a ring adapted to discharge its heated gases either radially or axially.

It is a further object of this invention to provide a burner construction which will afford unusual opportunity for flexibility in arrangement of its physical components. It is a still further object of this invention to provide a burner with such design flexibility that a single burner may be employed where previously several individual elements were necessary.

It is a still further object of this invention to provide a burner in which nozzle warpage and erosion are minimized.

It is a still further object of this invention to provide a burner which imparts high turbulence to the combustible mixture. It is a still further object to provide a burner construction in which the combustion products are evenly distributed along the discharge orifice.

An additional object to this invention is to provide a burner which will operate at temperatures above about 2500" F. without the use of high-priced alloys and other critical or unusual materials of construction.

A still further object of this invention is the provision of an improved method for the burning of fuel premixed with oxidant at super-atmospheric pressure. A still further object of this invention is provision of a method for the burning of fuel premixed with oxidant in a closed chamber to produce a high temperature, high velocity stream of combustion products.

Other and more specific objects and advantages of the invention will appear from the description which follows, and from reference to the drawings in which:

FIG. 1 is a projected view of a burner with the top and side walls partly broken away to reveal a portion of the interior construction.

FIG. 2 is a projected view of a burner similar to FIG. 1 but of somewhat simpler construction.

FIG. 3 is an illustration of a burner of a ring configuration with the orifice adapted for axial discharge of the combustion products.

FIG. 4 is a ring burner arranged for a radial discharge of combustion products and FIG. 5 is a burner for heating a long, narrow work piece.

FIG. 6 is a burner arranged with the inlets on a side of the burner.

In general, the burner of this invention comprises a combustion chamber adapted for operation at superatmospheric pressure defined by fluid-cooled walls and having a fluid-cooled discharge means. The combustion chamber contains a mass of loosely placed bodies of such a shape that open passages will remain between them. The bodies should preferably be of a material which will withstand temperatures above 2000 degrees F. because they are incandescent during operation of the burner. The glowing bodies efliect rapid ignition of the fuel-oxidant mixture and accelerate the rate of combustion by providing turbulence to burning gases and by radiating energy through the combustion region. The inlets which supply fuel and oxidant to the chamber, preferably as premixed gases, may be placed at various locations remote from the discharge means so the gases transit the re fr'actory mass during passage through the burner. For some reason not clearly understood, the fluid-cooled walls of the burner do not quench the combustion but absorb only a small fraction of the total energy output of the burner.

Referring now to the drawings, FIG. 1 shows a burner shell 1 which is generally rectangular but may be of any other shape which is convenient to produce and use. The shell shown can be readily fabricated from sheet materials and, therefore, is inexpensive to manufacture. It is generally of double-walled construction, as is shown at 2 and 3 and at 4 and 5. Although a single wall construction is shown for the back wall 6, it, too, can be a double wall construction and perhaps preferably so.

The space between the pair of walls 2 and 3 and the pair of walls 4 and 5 is filled with cooling fluid, supplied by means which is not shown.

The double wall construction extends to the orifice 7 and is an important feature in inhibiting distortion of this element when the burner is operating. An inlet pipe 8 is fitted to convey premixed fuel and oxidant to the interior of the burner under super-atmospheric pressure through a conventional inlet tip (not shown) fitted in the inlet pipe 8. Refractory alloys, such as those high in chrome and nickel may, of course, be used for the construction of this double-walled burner chamber but it has not been found at all necessary to employ this type of material. Mild steel fabricated by welding techniques has proven very satisfactory.

The interior of the burner chamber contains a large number of substantially solid bodies 9, of such a Shape that they may contact each other and the walls of the burner housing but will not nest but will between them define gas passages from the inlet 8 to the outlet 7. Other mechanically sturdy shapes also are suitable. Fused alumina balls have been found very satisfactory for this purpose and may be inserted into the burner chamber through the inlet 8 or through another filling opening. Other materials of like thermal stability may also be used.

The burner shown in FIG. 2 is of construction similar to FIG. 1 but is less expensive to fabricate because of its simpler design. Such a burner may have a combustion chamber of about 3 x 3 X 4 inches, a discharge orifice about t inch wide by 3 inches long, and may be filled with a plurality of refractory bodies having a major dimension of from about /2 inch to about 1 /2 inches.

FIG. 3 shows a projected view of a ring burner which has been sectioned to reveal its interior arrangement. It is generally of double-walled construction, the combustion chamber 20 being defined by water-cooled walls 21 through 25. Premixed fuel and oxidant is supplied at super-atmospheric pressure through inlets 26, a number of which may be spaced around the periphery of the burner and are connected to inlet feed Pipes 30. A discharge orifice 27 is adapted to direct the blast axially. The combustion chamber 20 is filled with alumina or porcelain spheres 28 only a portion of which are shown.

The ring burner shown in FIG. 4 is similar, except that the discharge orifice 40 is arranged to direct the discharge in a radial direction rather than axially as in the previous example.

In this view, an inlet feed pipe 41 is shown fitted with a bushing 46 holding a burner tip 42 for conveying the premixed fuel and oxidant mixture to the combustion chamber 43. A portion of the spheres 44 which fill the chamber are shown.

The burner in FIG. 5 is, of course, similar to the one shown in FIG. 1 but is adapted to heat a much longer work piece over a narrow area. When employing a long burner of this type, it has been found desirable to supply the premixed fuel and oxidant through a plurality of inlets spaced along the back wall 50.

The embodiment shown in FIG. 6 has the inlets 60 and the feed pipes 61 on the side of the burner, an arrangement which may be more convenient for some applications.

The bodies filling the combustion chamber impart great turbulence to the gas as it is passing through, so that combustion is extremely thorough and rapid. In addition, when the burner is at its operating temperature, the bodies are glowing very brightly, and the radiation from them serves to further accelerate a combustion in the turbulent gas in its transit through the passages between the various bodies. Because these bodies are already discrete and are loosely packed, they are not subject to mechanical damage or thermal shock to the same extent as a cast ceramic lining in the burner. Should they be severely damaged through accident or inadvertence, it is but a simple matter to remove them and replace them with fresh bodies. Spherical bodies have been found to be highly suitable for operation of the burner but the shape is not critical, and bodies of other shapes may be employed so long as they do not nest so that the passages for the gases are obscured and the pressure drop across the burner becomes excessive. Because there is no rigid connection between the ceramic bodies and the metal shell of the burner, differential thermal expansion of these parts is of no consequence in the operation of this burner. This absence of rigid connection between these elements likewise contributes to the mechanical ruggedness of the construction. Because the ceramic bodies can be added after the shell of the burner has been completed, and may be replaced at will, great latitude is afforded in the design of the burner shell to accommodate any existing needs or purposes. Furthermore, the ratio of radiant surface area of the ceramic bodies relative to the total volume of the burner chamber can be readily adjusted to accommodate different fuels should this be desirable.

In one embodiment of this invention a burner similar to FIG. 5 was constructed of /4" steel plate, so that the ends 51 were 4" wide and 3" tall, the length of the burner being 9 /2". The discharge slot 52 was /4" wide and 9" long. Three gas inlet pipes were equally spaced along the back wall 5%. As many as possible alumina balls 1%" in diameter were added to the combustion chamber by dropping them through the inlet pipes before inserting the burner tips. The space between the inner walls and outer walls was A", to which was supplied cooling Water under tap pressure.

Natural gas, having an energy content of about 1,000 B.t.u. per cubic foot, was premixed with air at a ratio of about 1 to 9 and fed at a pressure of about one pound per square inch to the burner. This gas immediately issued from the discharge slot 52 and was ignited and permitted to burn for a short time outside the slot. A stream of oxygen was then impinged into the slot to cause the flame to strike back and burn within the burner chamber. After a short time, 30 sec. or so, the alumina balls began to glow and when they reached a temperature estimated to be about 1500 F. the gas pressure was increased to seven pounds per square inch and the mixture adjusted so that the gas to air ratio was about i to 10. The temperature of the gas stream was reduced without decreasing its velocity by increasing the amount of air mixed with the gas, the glowing refractory enabling combustion to continue. A gas to air ratio of about 1 t 17 was operable.

When the burner is p-erating in a preferred manner, by looking into the discharge slot the refractory bodies can be seen glowing brightly. Very little if any flame could be seen emerging from the slot even after the room had been darkened. A further increase in the supply of gas and air did cause some flame to become visible but operation in this manner is considered less desirable.

It is quite clear, therefore, that a burner of advanced design has been disclosed, which will find utility in numerous appiications.

The foregoing embodiments were disclosed by way of example only and any additional modivcations may be made. It is thus contemplated to cover any such modifications as fall within the true spirit and scope of this invention as defined by the appended claims.

I claim:

1. The method of generating a high temperature, high velocity blast from a gas burner having a substantially closed chamber filled with rounded refractory bodies which comprises the steps of admitting to said chamber a premixed combustible gas-air mixture, the quantity of air in said mixture being equal to about of the amount of air required for complete combustion, igniting the mixture and continuing to burn it until the refractory bodies reach a temperature of about 1500 F., increasing the air in the gas-air mixture until the quantity of air in said mixture is equal to between about l0O%-170% of the amount required for complete combustion, continuing the combustion at super atmospheric pressure and discharging the combustion products through constricted dis charge means.

2;. A burner adapted to deliver a blast of high temperature combustion products at high velocity comprising steel walls defining the interior of a substantially closed combustion chamber adapated to operate at superatmospheric pressure, constricted discharge means forming an outlet passage adapted to lead the combustion products from said chamber in a high velocity stream, inlet means for a pressurized combustible mixture located remotely from said discharge means, a plurality of contiguous rounded refractory bodies substantially filling said chamber and in contact with said steel walls, said bodies being larger than said outlet passage and defining a plurality of combustion passages between said inlet means and said outlet passage.

3. A burner as in claim 2 wherein the refractory bodies are alumina balls with a diameter from about /2 inch to about 1 /2 inches.

References Cited UNITED STATES PATENTS 6 Land.

Hayes 158-99 Lucke 15899 Hammond 158-99 Rowland 263-5 X Hays. Schutz.

Stalego 158-99 X Ronay 263-4 JAMES W. WESTHAVER, Primary Examiner.

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