US2158522A - Fuel burner - Google Patents

Description

May 16, 1939. K. K. NA-GYAN FUEL' BURNER Filed July 29, 1937 KEvoRK K. NAH/GYAN Patentecl May 16, 1939 UNITED STATES PATENT OF FI CE.

FUEL BURNER Application July 29, 1937, Serial NO. 156,262

6 Claims.

This invention relates to fuel burners, and more particularly to burners for use with fluent f'uels, such as gas or pulverized coal, which are burned in suspension in a furnace.

It has been proposed heretofore to construct burners of this type with a fuel nozzle arranged to project a stream of fuel annular in crosssection, and to supply air to both the inside and the outside of the fuel stream. While such a construction tends to produce an intimate mixture of the fuel and air, certain serious difficulties have been encountered in operation. In some cases the operating range of the burner has been decidedly limited, and in other cases it has been difficult to ignite the fuel and to maintain ignition when operating at low rates of combustion. With certain constructions it is impossible to control the shape of the flame and to avoid impingement of the ame on the walls of the furnace.

2'0` Other prior burners have been expensive to manulut facture and subject to rapid deterioration because of the high temperatures encountered in actual service.

It is accordingly one object of the invention to provide a fuel burner which will allow ready ignition of the fuel, and which can be operated efiiciently over a wide range of capacities.

It is a further object of the invention to provide a fuel burner having a simple and effective means for adjusting the shape of the fiame.

It is a further object of the invention to provide a fuel burner which will be simple and inexpensive to manufacture, and capable of withstanding severe operating conditions throughout a long life of service.

With these and other objects in View, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.

In accordance with my invention in its preferred form, I provide a burner having a fuel nozzle shaped to discharge fuel in a converging annular stream. Means is provided forming a passage through which a fiow of air is induced to the center of the flame by the aspirating effect of the fuel stream. The issuing fuel stream is preferably wh'rled about its axis by means of suitable vanes in order to increase the aspirating effect. The nozzle is preferably surrounded by a casing forming a plenum chamber from which air may fiow around the outside of the fuel stream, and the nozzle may be provided with circumferentially spaced passages communicating with the plenum chamber and extending radially through the fuel passage. The induced air flow through these radial passages may be controlled by an axially adjustable damper mounted in the center of the fuel nozzle.

Referring to the drawing illustrating one embodiment ofv the invention, and in which like reference numerals indicate like parts,

Fig. 1 is a longitudinal section through a fuel burner, the section being taken on the line l-l of Fig. 2;

Fig. 2 is a front elevation of the fuel nozzle, as indicated by the line 2-2 of Fig. 1;

Fig. 3v is an enlarged section on the line 3--3 of Fig. 1; and

Fig' 4 is an enlarged rear elevation of the fuel nozzle.

The embodiment illustrated comprises a furnace wall Ili of refractory material provided with a circular opening ll therethrough which fiares outwardly at the rear or furnace side of the wall. A fuel nozzle l2 is mounted in front of the wall l and coaxial with the opening ll to discharge a stream of fuel rearwardly through the opening into the furnace. This nozzle I2 comprises an outer wall [4 and an inner wall l5, these walls forming a fuel passage IB therebetween which is annular in cross-section. The front portion of the outer wall M is increased in diameter, and the front portion of the inner wall l5 is decreased in diameter, to provide an inlet chamber IB which communicates with the annular passage l6, this chamber being closed at the front by means of a plate 19. The chamber IB is supplied with fluent fuel through a radially positioned inlet nozzle to Which a fuel pipe 2l is connected. Individually adjustable vanes 22 are mounted in the chamber 18 at its junction with the passage l6 to aid in distributing the fuel uniformly about the axis of the burner.

Air for combus-tion is preferably supplied to the burner under forced draft, and for this purpose the fuel nozzle I2 is enclosed in the rear of the inlet nozzle 20 by means of a casing 24. This casing forms a plenum chamber 25 which communicates directly with the furnace wall opening ll. Air is supplied to the chamber 25 under pressure through a duct 26, the rate of flow being controlled by dampers 21. In order to whirl the air at high Velocity as it enters the opening ll, and to distribute the air uniformly about the burner axis, suitable louvers or guide vanes 28 are mounted in the plenum chamber 25 in surrounding relation to the fuel nozzle l2. These vanes 28 are located in front of the wall IO and hence are protected to a considerable extent from the radiant heat of the furnace.

In order to obtain better mixing of the fuel and air, and to increase the fuel burning capacity ofV the burner while retaining the advantages of a comparatively short fiame, I provide means for supplying air not only to the outside of the annular fuel stream but also to the inside thereof. For this purpose there are provided four circumferentially spaced passages 30 which extend radially across the annular fuel passage IB and serve to connect the plenum chamber 25 with the central space 3l surrounded by the inner wall 15 of the fuel nozzle. The air fiow inwardly through these passages is controlled by a diskshaped damper 32 extending across the space 3 and mounted on the rear end of a tube 33 coaxial with the fuel nozzle l2. The tube 33 is slidably supported in the contracted portion ol the inner wall [5, and may be held in a desired position by means of a set screw 35. This tube is closed at its front end by a cap 36, which is provided with ears 31 to serve as handles When adjusting the tube.

The fuel stream discharged by the nozzle l2 is utilized to produce an aspirating effect which induces a considerable flow of air inwardly through the passages 311. For this purpose the nozzle l2 is arranged to discharge the fuel in the form of a converging annular stream which is preferably whirled about the axis of the burner in order to increase the aspirating effect and to provide a turbulent flame. As shown particularly in Fig. 1 the rear portions 39 and 49 of the nozzle walls HI and l respectively are made frusto-conical, with their smaller ends toward the furnace, and angularly positioned vanes dl extend across the annular fuel passage between these frusto-conical portions to whirl the fuel stream. The rear portion of the fuel nozzle IZ, comprising the walls 39 and 23% and the vanes Ill, is preferably made separable from the remainder of the nozzle and fastened thereto by neans of bolts 43.

The operation of the invention will now be apparent from the above disclosure. A mixture of pulverized coal and primary air (or other suitable fuel) is supplied to the chamber lt' under pressure through the pipe 2l, and is discharged rearwardly from the fuel nozzle I2 in the form of a whirling and converging annular stream. Secondary air, which is preferably preheated, is supplied to the plenum chamber 25 under pressure through the duct 26 under the control of the dampers 21 and whirled around the fuel nozzle by the action of the louvers 28. A part of this air fiows rearwardly into the furnace through the opening ll in surrounding relation to the fuel stream, and the remainder of the air is drawn inwardly through the radial passages 30 by the aspirating effect of the converging fuel stream and thus brought into intimate contact with the fuel at the very center of the flame. This makes it possible to operate the burner at very high fuel burning rates and yet combustion can be completed with a comparatively short flame. When lighting the burner and when operating at low fuel burning rates the damper 32 will be moved to its rearmost position to prevent aspiration of air through the passages 30. This will produce a rich fuel mixture immediately in the rear of the fuel nozzle and thus facilitate ignition of the fuel. This is particularly true since the Convergence of the issuing fuel stream tends to delay for a slight interval the mixture of the fuel with the surrounding secondary air. Moreover, the vanes 4I not only produce turbulence but they also form small segregated streams which are particularly rich in fuel and hence are readily ignited. The burner can therefore be successfully operated over an unusually wide range of fuel burning capacities. By adjusting the damper 32 it is possible to lengthen or shorten the flame as desired. The burner is simple and inexpensive to manufacture, and all parts thereof are well protected from the radiant heat of the flame.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. A fuel burner comprising inner and outer walls shaped to provide a fuel nozzle from which fuel is discharged in a converging annular stream, a casing surrounding the nozzle to form a plenum chamber from which air flows around the outside of the fuel stream, and means providing a passage through which air may flow from the plenum chamber inwardly to the center of the flame under the influence of the aspirating effect of the converging fuel stream.

2. A fuel burner comprising a fuel nozzle having inner and outer walls forming an annular passage from which a stream of fuel is discharged, a casing surrounding the nozzle to form a plenum chamber from which air flows around the outside of the fuel stream, and means providing circumferentially spaced passages extending radially through the fuel passage to conduct air inwardly from the plenum chamber to the center of the flame.

3. A fuel burner comprising a fuel nozzle having inner and outer walls forming an annular passage which is shaped to discharge fuel in a converging annular stream, a casing surrounding the nozzle to form a plenum chamber from which air fiows around the outside of the fuel stream, and means providing circumferentially spaced passages extending radially through the fuel passage to conduct air inwardly from the plenum chamber to the center of the ame under the influence of the aspirating effect of the fuel stream.

A fuel burner comprising a fuel nozzle having inner and outer walls forming an annular passage which is shaped to discharge fuel in a converging annular stream, a casing surrounding the nozzle to form a plenum chamber from which air flows around the outside of the fuel stream, means providing circumferentially spaced passages extending radially through the fuel passage to conduct air inwardly from the plenum chamber to the center of the flame under the influence of the aspirating effect of the fuel stream, and a damper mounted in the center of the nozzle and axially adjustable to control the air fiow through the radial passages.

5. A fuel burner comprising inner and outer walls forming an annular passage from which a stream of fuel is discharged, and means providing circumferentially spaced passages extending through the annular passage to conduct air from the space outside the outer wall inwardly to the center of the flame.

6. A fuel burner comprising a fuel nozzle having inner and outer walls forming an annular passage from which a stream of fuel is discharged, a casing surrounding the nozzle to form a plenum chamber from which air flows around the outside of the fuel stream, means providing circumferentially spaced passages extending through the annular passage to conduct air from the plenum chamber inwardly to the center of the flame, and damper means associated with the circumferentially spaced passages to control the fiow of air therethrough.

KEVORK K. NAHIGYAN.

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