US2396867A

US2396867A - Fuel burner

Info

Publication number: US2396867A
Application number: US529573A
Authority: US
Inventors: Jacob A Mason
Original assignee: Babcock and Wilcox Co
Current assignee: Babcock and Wilcox Co
Priority date: 1944-04-05
Filing date: 1944-04-05
Publication date: 1946-03-19
Anticipated expiration: 1963-03-19

Description

March 19, 1946. J. A. MASON FUEL BURNER Filed'ipril 5, 1944 2 Sheets-Sheet 1 Emu S w & mi am a, Q QM \MY 0 \lm & m mi NN Q mm mm m a V a mm 9 a m nm E m Q m 3 A TTORNE Y Mmh 19, 1946. J. A. MASON FUEL BURNER Filed April 5, 1944 2 Sheets-Sheet 2- Fig. 3

' IINVENTOR Jacob A. Mason .1 ATTORNEY Patented Mar. 19, 1946 FUEL BURNER Jacob A. Mason, Newark, N. J., assignor to The Babcock & Wilcox Company, Rockleigh, N. J a corporation of New Jersey Application April 5, 1944, Serial No. 529,553

4 Claims.

The present invention relates in general to the construction and operation of fluid fuel burners, and particularl to an improvement in the construction and the operation of fluid fuel burners utilizing a conical spray of atomized fuel discharging through a burner port into a swirling stream of air.

The main object of this invention is to provide a device in'a fluid fuel burner of thegeneral type described, for directing the flow of air through the body of the burner in a manner improving the mixing action of the entering fuel and air, and thus facilitating rapid and complete combustion of the fluid fuel. A further and. more specific object is the provision of a fluid fuel burner construction which in operation avoids combustion conditions tending to cause pulsations in the associated furnace. The invention is of particular importance and utility in high capacity furnaces with restricted volumetric dimensions, wherein combustion conditions must be maintained which minimize pulsations, due to the adverse effect of such pulsations on the furnace efficiency. For example, fuel burners incorporating the invention have been successfully used over a wide operating range in high capacity marine water tube boilers having an effective furnace depth of only 6 feet, without furnace pulsations and with a high combustion eficiency.

A better understanding of the present invention will be obtained b reference to the drawings and descriptive matter illustrating a preferred embodiment of my invention and attached hereto. The novel features of this invention are pointed out with particularity in the claims forming a part of this specification.

Of the drawings:

Fig, 1 is an elevation, partly in section of a mechanical atomizing liquid fuel burner incorporating my invention;

Fig. 2 is a view of the shroud member taken on line 22 of Fig. 1;

Fig. 3 is a perspective view of the burner port ring;

Fig, 4 is an enlarged view partly in section of the louver adjusting crank and gear assembly; and

Fig. 5 is a view of an individual air louver blade illustrating the change in radius of the louver tip on rotation about its axis and its relation to the shroud member.

In the drawings the invention is illustrated as incorported in a liquid fuel burner of the type shown in U. S. patent 2,260,062. As shown, the burner is mounted in a vertical wall ill of a suitable furnace II and arranged coaxially of a circular burner port 12 in the furnace wall. The port i2 is defined by suitable refractory material tapering to a substantially circular throat at an intermediate point. A metallic port ring l3, shaped as a truncated cone defines the outer section of the burner port and has a flanged outer end rigidly secured to the metal casing I of the furnace wall iii. As shown in Fig. 3, the port ring I3 is formed with its. inner discharge edge section shaped to form a regular decagonal surface at the inner side of the port throat section. A symmetrical series of air directional vanes i5 are located on corresponding flat surfaces of the port ring l3, each vane projecting inwardly toward the axis of the burner port and arranged with its furnace or inner edge meeting the fur.- nace edge of the ring 13 at the center of each flat of the decagonal inner surface, and the base of each vane pitched at an angle of approximately 30 to the plane of the furnace edge of the ring. The furnace edge of each vane i5 slopes outwardly away from the furnace at an angle of approximately 45 to the plane of the furnace edge of the ring, a bend being formed in the vanes near the furnace edge whereby the pitch angle is increased an additional amount, approximately 15. The vanes have rounded inner ends, which merge with a substantially straight outer edge arranged approximately perpendicular to the internal surface of the port ring.

The burner port ring i3 and vanes l5 impart a counterclockwise swirl to the stream of air passtween the walls forming a passageway ll surrounding the body of the burner for the flow of preheated combustion air to the burner port.-

Preferably these walls are spaced approximately 16 inches apart. Air flow from the space ll toward the furnace I I is caused by maintaining the air pressure in the space greater than the operating pressure in the furnace.

A circular cover plate It closes an access opening in the wall i6 arranged coaxially of and of larger diameter than the burner port ring. The plate i8 is provided with a heat protective covering of insulating material 42held in place by metallic sheet 43 and is rigidly'connected by struts 23 to the outer circumference of an air register ring 24 carried by a spool section 25 which in turn is fixed to the burner port ring,

the

parts

28 and 24 forming acontinuation of,

the ring l3. Cover plate I 8 supports a central hub member is through which extends a burner barrel 20 having a fuel supply assembly 2| on its outer end and an atomizer head 22 on its inner or furnace end. The atomizing head 22 is'prefsurface having a'series of equally spaced openin s and corresponding deflector plates therein.

A circular series of segmental louver blades 21 are pivotally mounted within the annular space between ring 24 and barrel 20 by pins 28 and 29. The rotational axis of each louver blade, as shown in Figs. 1 and 5 is at an oblique angle of approximately 60 to the axis of the barrel 20. Furthermore, the blades 21 are adjustable about blades has been demonstrated in practice. The

main advantage lies in causing the combustion air passing through the circular opening of the annular end plate to engage the leading edge of the louver blades and to be directed in limited rotational movement in proportion to the transverse angularity of the blades, the effect of the blades on the air flow being to minimize the formation of localized eddy currents of air detrimental to an equalized flow of the combustion air through the burner throat.

It will be observed, by reference to Fig. 5, the anguiarity of the louver blade axis with respect to the axis of the burner barrel causes a change inthe radius of the blade tip 40, as projected into the plane of the annular end plate 39, on rotation of the blade on its axis. When the blades are in their wide open position, the projected diameter of the tips in the described plane will be at the maximum value and at the'min imum value when the blades are rotated into the closed position. I have found by operating tests that the diameter of the annular end ring open-' ing 4| should be equal to or less, but should not their axes by means of pinions engaging a ring gear 3| on a rotatable sleeve 32. The sleeve 32 is operated by the mechanism shown in Fig. 4, consisting of

gears

33 and 34, shaft 35, and crank 36. The crank 36 is angularly movable to predetermined positions to rotate the louver blades 21 and thereby control the quantity and direction of the combustion air delivered to the fluid fuel burner. In Fig. l the louver blades are shown inia wide open position permitting maximum flow of combustion air therethrough. When in this position the leading edge 31 of the blades-will be substantially perpendicular to the axis of the burner.

In accordance with the present invention, a cylindrical shroud member 38 is formed concentrically with and circumferentially enclosing the series of louver blades 21, the inner edge of the shroud 38 registering with and welded to the outer edge of the air register ring 24 and thus defining a cylindrical outer end portion for the passageway directing the flow of combustion air from the space I! into the burner port, wherein it intersects and mixes with the conical spray of fuel discharging from the atomizer head 22. The outer end of the shroud member 38 .has an annular end plate or flange 39 welded thereto in a plane transverse to the axis of the burner barrel.

The axial length of the shroud member 38 is made suflicient to permit the full opening of the louver blades without having the blades contact with the annular end plate. 39. .The circular opening 4| in the end plate 39 is coaxial with the burner barrel, the diameter of the openin 4| being preferably less than the internal diameter of the ring 24 at the pivot pins 28 of the louver blades 21, and greater than the diameter of the burner port throat.

More specifically, as shown in Fig. 5, the radius of the annular end plate opening 4| is slightly less than the radius of a projection, in a plane normal to the plane of the annular end plate. of the louver blade leading edge tip 40 when the blade is in its closed position.

The importance of the described relation of the diameter of the annular end plate opening to the location of the leading edge tip of the louver be greater than the minimum blade tip diameter as projected in the plane 'of the annular ring opening to secure the optimum results.

In the drawings the axial length of the shroud ring is approximately 4 /2" and the outer diameter of the concentric end plate opening 4| is of the order of 20 inches. The enclosure formed by the concentric sections comprising the spool member 25, air register ring 24 and shroud member 38 extends outwardly from the furnace wall and within space I! approximately ten inches,

leaving a substantially unobstructed air space between the outer end of the shroud member 38 and the cover plate l8 of approximately six inches. The space between the impeller plate 26 and the shroud end plate 39 provides ample room to position the louvers without interfering with the proper functioning of the related parts of the fluid fuel burner.

Inoperation combustion air flows through the air passage l1 towards the end plate opening 4|, passing through the opening and into the louvers in generally axial flow relative to the axis of the burner. Since the position of the louver blades is dependent onthe quantity of air required for proper combustion of the fuel delivered to the furnace, the blades may be either wide open or at some partially open position. At any partially open position the blades will be at an angle transverse to the direction of air flow and will cause a clockwise swirl of the entering air, the intensity of swirl depending on the degree of angularity of the blades. The combined effect of the shroud member and the louver blade facilitates equalization of the flow of air throughout the area of the space surrounding the fuel burner barrel, greatly improving the combustion efficiency of this type burner.

In one installation where the fuel burning apparatus described was applied to a small furnace having an eiiective depth only four times greater than that of the burner throat diameter, the elimination of furnace pulsations and the increase in combustion efliciency was particularly outstanding in comparison with imilar burners without the described shroud member.

I claim r 1. In combination with a furnace wall having a fuel burner port therein, a casing spaced from said wall to form an air space therebetween, a fluid fuel burner nozzle arranged coaxially of and aseaser discharging a stream of fluid fuel through said burner port, and means for directing combustion air from said space into said burner port comprising a ring member forming a. continuation of said burner port, a circular series of air directing blades surrounding said burner nozzle within said ring member, and a shroud member forming a continuation of said ring member in said air space and having a central air inlet at the outer side.

of said air directing blades with a diameter not greater than the air directing blade tip diameter. 2. A. liquid fuel burner comprising a barrel with v an atomizing head in one end thereof, a burner port ring arranged coaxial with said barrel, a ring member forming an outward continuation of said port ring, a series of segmental louver blades pivotally supported between said ring member and said barrel with the pivotal axes thereof obliquely intersecting the axis of said barrel, an annular shroud ring forming an outward extension of said ring member and enclosing the periphery of said louver blades, and an annular end plate having a central opening of a diameter les than the diameter of the adjacent edges of said louver blades projected into the plane of said plate opening.

3. In combination with a furnace wall having a fuel burner port therein, a casing spaced from said wall to form an air space therebetween, a fluid fuel burner nozzle arranged co-axialiy of and discharging a stream of fluid fuel through lit saidburner port, and means for directing combustion air from said air space into said burner port comprising a ring member forming a continuation of said burner port, a circular series of pivotally mounted segmental airlouver blades surrounding said burner nozzle within said ring member, and a shroud member forming a continuation of said ring member in said air space and having a central air inlet at the outer side of said louver blades with a diameter less than that of said louver blade series and greater than the minimum diameter of said burner port.

4. In combination with a furnace wall having a fuel burner port therein, a fiuid fuel burner nozzle arranged coaxially of and discharging a stream of fiuid fuel through said burner port, and means for directing combustion air into said burner port comprising an air register ring forming a continuation of said burner port, a circular series of pivotally mounted segmental air louver blade surrounding said burner nozzle within said register ring, and a shroud member forming a continuation of said register ring and having a central air inlet at the outer side of 'said air louver blades with a diameter not greater than the minimum diameter of the leading edge of the tips of said louver blades as projected in the plane of said central air inlet.

JACOB A. MASON.