US2147925A - Method of gas flame control for heating furnaces - Google Patents

Description

Feb. 21, 1939.

F. G. SCHWALBE METHOD OF GAS FLAME CONTROL FOR HEATING FURNACES Filed June 28, 1957 2 Sheets-Sheet l @6449 Miwm Sum/wing Feb. 21 1939. F, G. SCHWALBE METHOD OF GAS FLAME CONTROL FOR HEATING FURNACES 2 Sheets-Sheet 2 Filed June 28, 1937 55 Hqb 26 f I I a s e s 4 2 HQ Z 4 H LII 5 4 Fill 2 e 6 z nrx U mm A w W J ,9 fl m4 mm M Jf w ///w/////// H Patented Feb. 21, 1939 UNITED. STATES PATENT OFFICE nmrnon or GAS FLAME oon'raor. FOR

HEATING summons Fran! G. Schwalbe, Toledo, 01110 Application June 28, 1937, Serial No. 150,684

1 Claim. (01. 158-99) My invention provides a method of producing a flame of gas in sheet form extending over a wide area for heating or heat-treating materials or articles.

The invention provides a method of producing uniform distribution of gas delivered from an extended port of a furnace and producing emission thereof at a constant and uniform quantity rate in sheet form with a relatively slow movement. By my invention, gas under pressure is directed to one or more burners to obtain approximately desired distribution of the gas within the burner or burners and then the gas stream is alternately and repeatedly expanded and con-- tracted in advance of its ignition and delivery to the furnace to produce the same uniform rate of flow of the gas from all parts of the burner or burners.

Particularly, the invention provides a method of impinging a mixture of fuel gas and varying amounts of neutral gas and primary air to produce reversal of flow and eliminate the velocity pressure head, and repeatedly and alternately expanding and contracting the stream-of the mixture to produce uniform local distribution of the 7 mixture within the burner and delivery into the furnace by a slow moving stream that is emitted at uniform quantity rate throughout the length of an extended narrow opening or a plurality of aligned closely positioned slots.

The method enables the formation of a flame that may be readily varied as to flame characteristics, as to flame lengths and wherein desired gas and air stratiflcation may be readily formed and consequently one that is applicable to varied requisites as to heat treatment of articles and materials and as to different substantially flxed flame controlling dimensional relations existing in furnaces of diflerent forms and/or used for different purposes.

The method involving the use of my invention may be varied in its details aspresented in the claim and'to illustrate a practical application of the invention, I have selected a burner as an example of the structure in which the method may be used. The selected structure and an 11-- lustrative method of the invention is described hereinafter. The particular burner structure selected is shown in the accompanying drawings. Fig. 1 illustrates conventionally a furnace and also shows the burner and its connections with sources of supply of fuel gas, air and neutral gas or substantially non-burnable gas. Fig. 2 is a view of a vertical transverse section of the burner. F18. 3 is a longitudinal horizontal section of the burner structure. Fig. 4 is a vertical section of secondary air passageways of the burner. Fig. 5 illustrates a vertical longitudinal section of a part of the burner structure taken on a plane at right angles to the plane of the section shown in 5 Fig. 3.

The burner structure I may be used in connection with a furnace 2 wherein materials may be heated by a flame having desired characteristics in order to produce particular desired effects on 10 the material heated The burner structure i is located in position to deliver a mixture of air and neutral gas, such as waste gas in varying amounts together with fuel gas, through a suitable port 3, the products of combustion being withdrawn 15 from the furnace through a port 4 that connects with the stack 6 of the furnace. A desired amount of the gaseous products of combustion may be drawn from the stack and used as the neutral gas.

The fuel gas is directed from a source of supply through a p'pe II to the burner structure and is controlled by a suitable valve Ill. The primary air is conducted from a source of supply of air under pressure, such as the blower 9 that 25 operates to draw air from the atmosphere through the pipe l5 and directs it through a pipe i3 to the burner structure. The pressure of the air is controlled by a suitable valve, such as the valve l4, and a damper or slide valve IS. The 30 pressure of the gas from the source of supply of fuel gas is at the usual low pressure and less than the air pressure.

The waste gas of the furnace consists largely'of carbon dioxide gas and nitrogen and may be used 35 as the neutral gas. It may be drawn from the stack by the blower through the pipe 24 and directed by the blower to the pipe IS. The pipe 24 may be provided with a damper or slide valve 25 that will coact with the valve l4 in the pipe 4 iii to regulate the pressure of the neutral gas.

The velocity of stream of air and fuel gas mixture or the mixture of neutral and fuel gas or the mixture of fuel gas, air and neutral gas as it leaves the burner and enters the furnace is 45 controlled by varying the volume of mixture and the relative quantities of the neutral gas and air to the fuel gas in the mixture by adjustments of the valves i4, i6 and. Thus, the fuel gas may be mixed with air alone or with the neutral gas alone or with varying proportions of the air and neutral gas to vary the rate of flame propagation and luminosity. Variation in the quantity ratio of the air and waste gas introduced into 5 the fuel gas may be produced by adJustments of slide valves l8 and 25.

The air or neutral gas or mixture thereof under a relatively high pressure is directed through a nozzle 2|) into a passageway through which the fuel gas also moves to the burner structure. The nozzle 20 is located in and extends through a chamber 2|. The fuel gas enters the chamber so as to surround the nozzle. Consequently, the high pressure of the gaseous fluid moving through the somewhat constricted nozzle 20 operates injector-wise to draw the gas from the pipe II and produce a pressure in the passageway leading to the burner structure that is greater than that of the gas as delivered by the pipe N. If the pressure of the source of supply of gas is not sufficiently high, it may be raised by any suitable pressure means to a pressure substantially the same as that .of the pressure of gaseous mixture delivered to the burner and the injector nozzle may be omitted. The flow of the stream under a relatively high pressure in the conduit leading to the burner produces a thorough mixture of the gases and causes introduction of substantially equal portions of the gaseous mixture into the burners or parts of the burners in advance of discharge from the burner nozzles or outlets.

A pipe 23conducts the gaseous mixture to a pipe 26 located above a box 21. The ends of the pipe 26 are connected by pipes 28 to the ends of a pipe 29 that conducts gaseous mixtures into a plurality of metal shells 3| located in the box 21.

The height and' length of the interior of the box are substantially the same as the corresponding dimensions of the port 3. The port 3 may extend the width of the furnace. The box is connected to the furnace so as to cover the port.

The shells 3| may be of any desired length. They are mounted contiguous to each other and extend the length of the port. The cross section of the shells at right angles to their longitudinal central axis are substantially elliptical, the sides having the smaller curvature being slightly flattened as shown in Fig. 2. The side parts 39 of the shells extend into the port 3, and are provided with openings 4|. The orifice or opening 4| of each shell is made in the form of a narrow restricted slot extending the full length of the shell. The exterior of each shell flare venturi-wise from the opening 4| toward the central part of the shell. The side part 42 of the shell is closed and sharply curves, but with decreasing curvature along the top and bottom walls of the shell.

The pipe 29 extends through the ends of the box 21 and the shells. The end walls 43 of the shells have openings that exteriorly fit the pipe 29. To fixedly locate the shells on the pipe 29, the shells are provided with ears 44, and a. rod 45 extends through the ends of the box 21 and the ears 44. The pipe 29 has an exterior diameter slightly less than the vertical dimension of the interior of each shell to form restricted passageways or narrow openings 46 of small vertical dimension intermediate the pipe and the inner surfaces of the top and bottom of the shell and divides the shell into two expansion chambers 49 and 50.

If desired, a single shell may be used extending the length of the port 3 of the furnace. Preferably a plurality of shells of shorter length are used for convenience of mounting and substitution of parts and to readily obtain various flame widths. The shells are closely positioned and interior surfaces I end to end and deliver the gaseous mixture throughout the length of the port of the furnace in a substantially continuous sheet.

The pipe 29 is provided with a plurality of openings 48. The openings are located in the sides of the pipe away from the openings 4| of the shells and direct the streams of gaseous mixture that flow with considerable velocity by reason of the relatively high pressure of the gas in the pipe toward the sharply curved wall parts 42 of the shells where the flow of the gas is reversed and loses its velocity head pressure. The gas of each stream is divided into two streams that expand within the shells between the pipe 29 and the wall parts 42 of each shell and at a very much reduced pressure and reduced rate of flow each of the streams passes through a restricted area 48 and into the space between the pipe 29 and the part 39 of the shell where it again expands. The gas of the said two streams is brought together between the pipe and the part 39 and the gas then passes through the slot or opening 4| and the port 3 into the furnace at a relatively low pressure. Thus, the gaseous stream is raised in pressure and is then reversed in its direction of flow by impingement and is divided into two streams. The streams are then repeatedly expanded and constricted in its outward movement which insures substantially perfect distribution and uniform emission throughout the length of the orifices or openings 4| into the furnace.

The relatively high pressure to which the gas and air mixture is subjected enables uniform distribution of the gaseous mixture to all of the shells. If the gaseous mixture at the pressure produced in the pipe 29 were directed toward the openings 4| of the shells, the velocity of its emission from the shells would cause immediate local burning of the gas in close proximity to the port opening and prevent progressive flame propagation. By the reduction or elimination of the velocity pressure and the repeated alternate expansion and contraction of the gas stream within the shells, the gas pressure and the rate of flow of the stream of the gaseous mixture is reduced to cause the mixture to beemitted in the form of a slow-moving stream and prevent a turbulent or rapid mixture of the fuel gas with the secondary air in the furnace and the resultant localized heating at the port. The steady, uniform, relatively slow movement of the gas enables progressive combustion of the fuel gas according to the relative amounts of air and neutral as in the mixture with the fuel gas, that is, according to its combustion rate. The rate of movement of the gas may be adjusted by the valves l4, l8, and 25 and its ignition rate by the relative adjustment of the valves |2, l6, and 25, and, consequently, the flame length may be varied by relative adjustment of the four valves. Thus, by my invention, a sheet of flame of uniform heat emissivity having a width substantially equal to the length of the port and a length that will accord to the fuel gas quantity delivered to the furnace and its rate of flame propagation may be readily produced.

The stream of the gaseous mixture from the shells is delivered into or beside a stream of secondary air that moves in the same direction and at the same or aslightly less or slightly greater rate according to the results it is desired to accomplish in the furnace. The secondary air is directed from a suitable source of supply of air, such as the blower 54 as controlled by a damper or valve 55, through the pipe I58. The shell Si is connected to a second shell 62 by means of relatively large pipes 63 that interconnect the two shells at a plurality of spaced points to distribute the stream flow of the air over the interior of the shell 62. The movement of the air through the pipe 63 is controlled by slidable dampers or valves 64. The shell 62 has an open side that extends the length of the shell and is surrounded by the flanges that are secured to the edges of the box 21. A wire screen 81 of fine mesh is located intermediate the flanged edges of the shell and the edges of the box and operates to produce uniform distribution of the secondary air and substantially the same quantity rate flow through difierent parts of the box 21. .The secondary air flows above and below the shells 3| and through the port 3 into the furnace and above and below the gaseous stream that flows from the shells 3|. The secondary air quantity taken with the primary air quantity is adjusted to produce complete combustion of the fuel gas in advance of its entrance into the stack 8. The

rate of flow of the secondary air may be regu-. lated and varied by the valves 55 and 64.

The amount of the secondaryair that flows above the shells as compared with the amount that flows below the shells may be varied by raising or lowering the shells relative to the central horizontal plane of the box 21. Thus, if desired, the shells may be lowered to increase the quantity of secondary air that is directed'above the flame whereby the flame may be blanketed to protect the crown and produce a highrate of transmission of the heat to the material or articles to be heated or heat-treated.

I claim:

The method of producing a uniform discharge of fuel gas in sheet form from a burner which consists in reversing a stream of gas of relatively high velocity by impingement and producing two streams of gas from the said stream, progressively and separately. expanding the said two streams and separately contracting by restriction of each of the said two streams at points in line with its normal movement, again expanding the streams to intermingle the streams and progressively contracting the gas of the streams and directing them together to unite them in a single stream and then liberating the gas in sheet form at a uniform rate.

FRANZ G. SCHWALBE.

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