Abstract:
An oil fired burner adapted to produce a variable asymmetrical flame shape. The burner includes a tip head carrying a plurality of tips disposed in at least two orientations, i.e., axial and off-axis. The relative rates of fuel supply to the tips is controlled to afford asymmetric flame shaping. In a typical application in a rotary cement kiln, the flame is biased to increase the heat transferred to the load in the front end of the kiln and to decrease the heat transferred to the top and sides of the kiln.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to an oil burner that affords adjustment of the shape of the flame produced thereby in an asymmetric pattern. 
     In many burner applications, for example, in firing a rotary kiln, it is desirable to vary the flame pattern from time to time and to bias the shape of the flame in an asymmetric pattern. In the environment of a rotary kiln, variations in the constitution and feed rate of the raw materials fed into the kiln require variations in flame shape in order to achieve optimal operation. 
     Oil fired burners designed to produce variable flame shapes which are symmetrical in longitudinal cross section are known. An exemplary burner is described in U.S. Pat. No. 3,752,405 to Vosper et al. Therein, an oil burner is described having two separate, individually fed oil injection systems, one of which injects one or more narrow, axially directed oil streams, and the other of which injects one or more short, wide angle oil streams. The apparatus described in that patent is so arranged that the streams injected by the two systems intercept one another to form a symmetric composite stream which combusts in the form of a composite flame of variable &#34;bushiness.&#34; 
     SUMMARY OF THE INVENTION 
     According to the invention, a variable flame shape oil burner for kiln and other applications produces a flame which is asymmetrical in longitudinal cross section. The flame produced thereby is biased to increase the heat transferred generally downwardly to the load in the kiln and to decrease the heat transferred to the top and sides of the kiln where the burner is aligned with the kiln axis. In specific embodiments, the burner can produce a flame which is biased to increase the heat transferred to the load at the front end of the kiln. 
     The burner according to the invention includes a tip head which is fabricated with a multiplicity of flame tips arranged in a predetermined pattern and at predetermined angles relative to a central axis. Specifically, there are provided so-called core tips, i.e., tips fed through the central or core supply line, which direct an axial fuel spray. The tip head further includes so-called annulus tips, i.e., tips fed through an annular coaxial supply line, which directs fuel spray at an angle with respect to an axial center line of the burner. The fuel sprays intersect to form a composite asymmetrical fuel spray. Each of the annulus tips is adapted to produce a spray cone angle of greater than about 70° and preferably about 80°. A spray cone angle of about 33° is used in the core tip heads. The wider spray angle has the effect of producing a softer spray with a smaller droplet size which results in a desirable localized heat &#34;polishing&#34; effect from the annulus tips without danger of actually stroking or &#34;playing&#34; on the load. 
     In a specific embodiment for use in a cement kiln, two wide angle annulus tips and three axially aligned core tips are provided. The wide angle annulus tips are disposed at about a 45° to 55° angle relative to the center line of the burner. The annulus tips are to be oriented at an angle generally directed toward the location of maximum load in the kiln. 
     Separately controllable fuel supplies are provided to the annulus tips and to the core tips. An asymmetric bushy portion of the flame can be directed toward the load by relative adjustment of the fuel supply rates. 
     The principal object of this invention is to provide a burner which is capable of producing any desired asymmetric flame shape between a long narrow flame at one extreme and a short wide bushy flame at the other extreme. This object at achieved by providing in close spaced relation two sets of individually fed nozzle tips disposed at compound angles and by means for varying the amount of fuel supplied to each of the nozzle tips. 
     A feature and advantage of the present invention is that the rate or the pressure at which the fuel is supplied to one or both of the nozzle tip sets can be varied in order to extend still further the range over which the flame shape can be varied. 
     Other objects, features and advantages of the present invention will be more apparent after referring to the following specification and accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front elevational view in partial cross section of a burner according to the invention. 
     FIG. 2 is a side cross sectional view along line 2--2 of FIG. 1. 
     FIG. 3 is a side cross sectional view of a burner tip suitable for use in the device of FIG. 1. 
     FIG. 4 is a cross sectional view along line 4--4 of FIG. 3. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring more particularly to the drawings, there is shown a burner assembly 10 having a tip head 12, a first fuel supply conduit for core feed 14, a second fuel supply conduit or annulus feed 16 concentric about the core feed 14, a first controllable liquid fuel supply 18 which is connected with core feed 14 and a second controllable fuel supply 20 which is connected to annulus feed 16. 
     As shown in FIG. 1, the tip head 12 is mounted to the core feed 14 and annulus feed 16 which mates with first and second concentric counterbores 22 and 24 in the tip head 12. The tip head 12 is generally cylindrical and includes a first face 26 which is generally perpendicular to a central axis of the tip head and a second face 28 at an obtuse angle to the first face 26. The second face 28 may be formed by cutting off one corner of the tip head 12 so that the first and second faces 26 and 28 share a common edge 30. The angle between the central axis through face 26 and an axis normal to face 28 is generally between about 40° and 70° and is preferably about 55°. In other words, the angle of the faces to one another along edge 30 is preferably about 235° (or 125°). 
     Referring now particularly to FIG. 2, it is seen that each face 26 and 28 includes a plurality of orifices therein. The orifices are threaded sockets adapted to receive spray tips, an example of which is shown in FIG. 3. The sockets in face 26 may be called core tip sockets 32 because they are adapted to mount a burner tip which received its fuel supply from core 14 through a plurality of conduits 34. The sockets in face 28 are called annulus tip sockets 36 because burner tips therein receive fuel from the annulus 16 through conduits 38 and 40. 
     In the preferred embodiment, the tip head 12 is bilaterrally symmetric along a plane passing through the central axis. Three core tip sockets 32 are provided equidistant from the central axis in face 26. Two annulus tip sockets 36 are provided in the side face 28 which are also equidistant from the central axis although disposed in a divergent direction. A bore 42 and conduits 34 communicate between core 14 and core tip sockets 32. Annulus 16 communicates through a bore 44 and conduits 38 to core sockets 36 as well as through conduits 40. The respective conduits 34, 38, 40 open into the respective sockets 32, 36 through the side of a socket counterbore. 
     The annulus tips are configured to generate a relatively broad spray of fuel whereas the core tips are configured to generate a relatively narrow spray. The construction of one such tip 46 is shown in FIG. 3. Each tip 46 has an axially directed outlet passage 48 that communicates with an inner chamber 50 disposed therebehind. The chamber 50 is supplied with fuel from one or more tangentially directed passages 52 which lead to an annular chamber 54 defined by the outer wall of the tip 46 and the counterbore of the socket. The tip 46 sealably rests on a countersink 56 of the socket. The tangential passages 52 are shown more clearly in the cross section of FIG. 4. The tips 46 in annulus sockets are adapted to form a short wide fuel stream by reducing the diameter of tangential passages 52 relative to the size of the axial passage 48. The spray cone angle of the annulus tips are for example, preferably chosen to be between 60° and 100° and particulary a spray cone angle of about 80° is optimal. Spray cone angles in this range produce a relatively soft spray with small droplet sizes as compared with narrower spray angles. The cone angle of core tips is generally chosen to be between about 30° and 40° and particularly an angle of about 33° is optimal. When used in a tip head according to the invention to form a composite flame spray, the tips produce surprising results as hereinafter explained. 
     The contemplated operation of the invention is within a kiln which has a load to be fired which extends generally longitudinally along the bottom of the cylindrical interior of the kiln. The tip head is disposed within the kiln at one end with its central axis generally parallel with a central axis of the kiln and with the side face 28 disposed with its edge 30 generally parallel to the surface of the load. 
     Fuel from the controllable liquid fuel supply 18 for the core tips is injected through the core conduit 14 into the core tips to produce a combustible spray parallel to the central axis. Similarly, fuel from the controllable liquid fuel supply 20 is injected into the annulus 16 and through the annulus tips to produce a bushy or relatively wide, fine combustible spray transverse and asymmetrically divergent from the central axis. This latter spray, being extremely fine because of the wide spray angle and its reduced fraction of the total oil capacity from all nozzles, is &#34;picked up&#34; by the primary air and provides an immediate total heat release into flame heat of all of its oil since the primary air stream is able to provide, with a small additional quantity of ingested secondary air as needed for 100% combustion, quickly and locally of the oil from each of the annulus tips. This combustion, barely visible as a heat &#34;blister&#34; on the lower part of main flame body, adjacent, i.e., toward the load, is available to provide the heat source for the localized load head &#34;polishing&#34; by radiant energy transfer according to Boltzmann&#39;s law. 
     Fuel flow to each of the tips may be changed by changing the pressure of liquid fuel supplied thereto, or if larger changes are required within the limits of acceptable atomization, tips of differing capacity may be substituted. Also the side face 28 may include tips skewed from the plane through the central axis to provide further asymmetric divergence. 
     EXAMPLE 
     One effect of the use of a burner head according to the invention has been observed in a wet process cement kiln. The core tips function to provide load preheating and calcination of the limestone in the calcining zone. The annulus tips provide a relatively short flame of variable bushiness which, together with the spray of the core tips, can produce a flame for heat &#34;polishing&#34; of the clinker just prior to its discharge from the kiln. Core tips and off axis annulus tips having spray cone angles of 33° and 80° respectively in a tip head according to the invention produce a relatively short hot flame. At normal operating pressures within the limits of good atomization, the liquid fuel does not &#34;punch through&#34; the primary air, but rather mixes intimately with the primary air to provide in effect a large, bright, radiant heat bubble directly over the load in the kiln with spectacular results. The temperature of the clinker zone of an upset kiln which is at 2200° F. when driven according to the invention with an annulus tip pressure at 250 PSI has been observed to quickly increase in temperature to 2600° F. by mere increase in the annulus fuel pressure to 800 PSI. 
     The invention has now been described with reference to specific embodiments. Other embodiments will be apparent from this disclosure to those of ordinary skill in the art. It is therefore not intended that the invention be limited except as indicated by the appended claims.