US 3308869 A
Description (OCR text may contain errors)
March 14, 1967 w. L. LIVINGSTON 3,308,869
LIQUID FUEL BURNER FOR WIDE RANGE OF LOAD Filed Dec. 17, 1965 2 Sheets-Sheet 1 \ELECTROMOTIVE FORCE Lu 90 FIG. 4
INVENTOR: WILLIAM L. LIVINGSTON FIG. I5 BY @lafdfl AGENT March 14, 1967 w L. LIVINGSTON LIQUID FUEL BURNER FOR WIDE RANGE OF LOAD 2 Sheets-Sheet 2 Filed Dec. 17, 1965 INVENTOR: WILLIAM L. LIVINGSTON AGENT United States Patent 3,308,869 LIQUID FUEL BURNER FOR WIDE RANGE OF LOAD William L. Livingston, Burnsville, Minn., assignor to Combustion Engineering, Inc., Windsor, COnlL, a corporation of Delaware Fiied Dec. 17, 1265, Ser. No. 514,516 7 Claims. (Cl. 158--28) The invention relates to an improved apparatus for burning liquid fuel at a wide range of load, and is particularly applicable to a steam or air atomizing oil burner and related apparatus for burning oil in the furnace of a steam generator.
In modern steam generating practice it is quite fre quently required that the steam generator be capable of operation over a wide range of steamload. Thus the fuel input into the furnace or the heat input may often vary between percent and 100 percent of the full load capacity. Since the load range of oil burners for efficient operation is generally considerably less than that required of the steam generator it had, in the past, been necessary in large steam generators to employ several oil firing burners such as four, six or nine, with only a selected number of burners in operation for any given steam load below maximum load. Also, with this plurality of burners a distinctive spray pattern or firing pattern has been established to produce the most effective heat absorption in the furnace, when operating at loads below maximum steam load. Thus, not only the number of burners selected for operation at a given load, but also their location with respect to the geometry of the furnace chamber play a vital role in the establishment of the most eflicient fuel spray pattern.
The requirement of installing a plurality of burners in one steam boiler furnace together with the auxiliary apparatus for operating these burners for the purpose of obtaining a wide load range, substantially increases the capital cost as well as the maintenance cost of the steam generator.
It is accordingly a major object of the invention to provide a steam generating furnace having a liquid fuel firing burner capable of producing a variety of spray patterns which are suitable for variable load conditions that extend over a wide load range of the steam generator.
It is another important object of the invention to control the selection of the most suitable spray pattern of the herein disclosed burner in response to variations in steam load.
It is a further object of the invention to provide a steam generating furnace having a burner with different spray patterns, in which the spray pattern with a relatively wide over-all spray angle is selected for the high combustion rates or high steam load condition, and the spray pattern with a relatively narrow spray angle is selected for the low combustion rates or low steam load conditions.
It is a still further object of the invention to provide a steam generating furnace having a burner capable of producing different spray patterns in which a spray pattern for high combustion rates or high steam load conditions is selected that is produced by orifice groups having a large number of spray orifices, and a spray pattern for low combustion rates or low steam load conditions is selected that is produced by orifice groups having a small number of spray orifices.
Other objects and advantages of the invention will become apparent from the following description of an illustrative embodiment thereof when taken in conjunction FIG. 2 is an enlarged partial and diagrammatic cross section through the herein disclosed burner nozzle and showing the control means for operating the same;
FIG. 3 is a front view of the burner nozzle shown in FIG. 2;
FIG. 4 is a line diagram showing in detail the control apparatus for selecting suitable spray patterns as required by combustion rates or steam load requirements;
FIG. 5 is a line diagram showing a typical valve actuator in detail;
FIGS. 6, 7, 8, 9, 10, 11 and 12 are schematic representations of different orifice group combinations that form fuel spray patterns suitable for different combustion rates or steam load conditions; and
FIG. 13 illustrates a burner nozzle tip of a different design than that shown in FIGS. 2 and 3.
Referring nOW to the drawings wherein like reference characters are used throughout to designate like elements and referring specifically to FIG. 1, the illustrative and preferred embodiment of the invention depicted therein includes a vapor generator designated generally as 10 and comprising a furnace chamber 12 having a wall 14 provided with a burner throat 16 for feeding liquid fuel such as oil to furnace 12 by way of conduits 28, 29, 30 and burner nozzle 20, primary air by way of conduits 34, 35, 36 and secondary air by way of conduit 22 and wind box 23.
Referring now to FIG. 2 the burner nozzle comprises a nozzle tip having a wall 24 facing theinterior of furnace 12. Groups of orifices generally desisgnated as 25 are provided in wall 24. In the preferred embodiment of the invention illustrated in FIG. 2 three groups of orifices A, B and C are shown in wall 24 for discharging a mixture of liquid fuel and atomizing medium into the furnace chamber 12. Each group A and B comprise eight orifices, whereas group C only has five orifices. The number and size of these orifices are subject to change depending upon the viscosity of the liquid fuel and the required firing capacity of the fuel burner.
Liquid fuel referred to in the description herein as fuel oil, for example, is delivered to the burner nozzle 20 from a source 26 by way of pump 27 and conduits 28, 29 and 30, and under pressure which may vary with steam load.
Atomizing medium which may be steam or air or other suitable gaseous fluid, however herein generally referred to as air, is delivered under pressure to burner nozzle 20 from a source not shown by way of pump 32 and conduits 34, 35 and 36.
To receive the fuel oil and atomizing air the preferred embodiment of the burner nozzle shown in FIG. 2 comprises six coaxially internested tubes 40, 41, 42, 43, 44 and 45. Of these tubes three tubes 40, 42 and 44 are operationally connected to conduits 30, 29 and 28, respectively, for receiving fuel oil, and the remaining tubes 41, 43 and 45 are operationally connected to conduits 34, 35 and 36, respectively, for receiving the atomizing air. Each pair of tubes 40, 41 and 42, 43 and 44, 45 terminate in concentric mixing chambers 46, 48 and 50, respectively, which, in turn, communicate with orifice groups A, B and C, respectively.
As illustrated in FIG. 3, the eight orifices of each group A and B are spacedly located on two imaginary lines 51, 52 and 53, 54, respectively, which lines in the preferred embodiment of FIG. 3 form concentric circles surrounding the longitudinal axis 55 of the burner nozzle. Likewise, four of the orifices of group C are located on a concentric circle 56 with the fifth orifice being located on the nozzle axis. Lines forming other geometric figures such as elipses or squares could be used for the purpose of grouping orifices.
The orifices of each group, with the exception of the center orifice or group C, are arranged such that the longitudinal axis of each orifice is inclined to the longitudinal axis of nozzle at an acute angle, with the size of the angle increasing as the distance of the respective orifice from the nozzle axis increases. Thus, the axes of the outermost orifices of group A form the largest spray angle a with the fuel nozzle axis, and the axes of the outer orifices of group C form the smallest spray angle c. The axes of the outermost orifice of group B form an intermediate spray angle b with the fuel nozzle axis.
Obviously, when all the orifices deliver oil to the furnace for burning, and at the widest possible sprayangle and at the highest pressure, a maximum quantity of heat is delivered to the furnace. For very low loads only the orifices of group C sprays oil into the furnace and at a narrow spray angle 0. Accordingly, only a small fire ball is formed in the furnace with orifice group C in operation, in contrast to the largest fire ball being formed with all orifice groups A, B and C in operation.
In addition to the three spray patterns mentioned above, there are four additional intermediate spray patterns to serve other load conditions between the maximum and the minimum loads. All seven spray patterns are diagrammatically illustrated in FIGS. 6 through 12. Thus, in FIG. 6 only the orifices of group C are shown to be in operation; in FIG. .7 the orifices of group B are shown for discharging oil into the furnace at a wider spray angle b; and in FIG. 8 a still wider spray angle is obtained from the group A orifices. FIGS. 9, 10 and 11 show arrangements wherein two orifice groups are combined for operation. Thus, groups C and B are combined in FIG. 9, groups C and A in FIG. 10 and groups B and A in FIG. 11', all representing spray patterns for increasing the steam load. FIG. 12 shows a pattern wherein all the orifice groups A, B and C are in operation for maximum load conditions. I
In accordance with the invention the flow of fuel oil and atomizing air to each orifice group is individually controlled. Accordingly, the oil conduit and air conduit 34 supplying mixing chamber 46 and orifice group A with fuel and air are provided with flow controlling devices such as valves 60 and 62, respectively. Likewise the oil conduit 29 and air conduit supplying mixing chamber48 and orifice group B with fuel and air are provided with valves 64 and 66, respectively. Also, oil conduit 28 and air conduit 36 supplying mixing chamber 58 and orifice group C with oil and air are provided with valves 67 and 68, respectively.
The main controller 7 operatively connected with the fuel and air valves is organized to regulate the oil and air flow to the various orifice groups or combination of groups of FIGS. 6-12. FIG. 4 illustrates how the various valves are connected to the controller 7 for operation in response to various steam loads. Seven control points corresponding to the individual spray patterns illustrated in FIGS. 6l2 are shown as being operated by a master switch 69 having seven contact stations 70 through 76. These contact stations correspond to variable load conditions such as, for example, from 10 percent through 100 percent of maximum load. As an example, contact stations 70, 71, 72, 73, 74, 75- and 76 may correspond -to 10, 25, 40, 70, 85 and 100 percent, respectively,
of maximum load. Depending upon the operating conditions of the steam power plant other percentages of load could be chosen for the selection of the diiferent spray patterns or orifice group combinations as shown in FIGS. 612. Also, while manually controlled switches are shown for the sake of simplicity other switching gear directly connected to a load indicating device, as well known in the art, may be employed for the above purpose. the controller' 7' shown in FIG. 4, a switching bar 77 shown in the neutral position is rotatably mounted on a pin 78 electrically connected to pole/7.9. so. as to make Turning now to a more detailed description of closes switch 1%.
selective contact with the seven switching stations through 76. Switching stations 7t), 71 and 72 are each provided with one contact point, switching stations 73, 74 and 75 with two, and switching station 76 with three contact points. The closing of switch 70 will cause an electric circuit to be completed which includes switching bar 77 connected to one pole 79 of an electromotive force by way of conduit 80, conduit 81 connected to one end of the winding of an electromagnetic relay 82 and conduit 83 which is connected to ground or to the other pole 84 of the electromotive force. Energizing of relay 82 will close switch 85, normally held open by the tension of spring 86. This will complete an electric circuit comprised of conduit 87 connected to ground or pole 84 of the electromotive force, pole 79, conduits 88 and 89, valve actuator 90, organized to open fuel valve 67, and conduit 91 leading back to switch 85. In addition to the electric circuit just described, another circuit parallel thereto is completed by closing contact 70, which circuit includes conduit 92 connected to conduit 88 and to one pole of actuator 94 for opening air valve 68, with the other pole being connected to conduit 91 leading back to switch 85.
A typical. actuator for the fuel valves and air valves is shown in FIG. 5. A reversible motor such as 95 is provided for opening and closing each respective valve, for instance, valve 67, such opening or closing depending on the position occupied by spring loaded switches 96a, 96b. Thus, with switch (see FIG. 4) closed, a circuit is established which energizes relay 97 to the effect that switch 96a, 96b is pulled to the lower position against the tension of spring 98, thereby establishing a current flow through motor drive to open the fuel or air valve, such as valve 67, for example. The opening of switch 85, however, will energize relay 97 thereby permitting switch 96a, 96b to break the circuit which held the valve closed and through tension exerted by spring 98, and to assume the upper position thereby closing an electric circuit having reversed polarity. This causes reverse rotation of motor operator 95 and an opening of th valve 67. e
The actuator 94 operating air valves 6% acts in the same manner. Accordingly upon closing contact 70 in response to a load requirement of 10 percent, for example, both the fuel valves 67 as well as the air valve 68 which normally are held closed, are opened. In this manner fuel and air is admitted through conduit 44 and 45 into mixing chamber 50, and through the orifice of group C into the furnace 12 for burning in accordance with the spray pattern shown in FIG. ,6.
The valve controlling apparatus which is operatively connected to contacts 71 and 72 acts in a like manner. Thus, closing of contact 71 in response to a load require ment of 25 percent, for example, energizes relay 99 and to open fuel valve 64 and air valve 66. In this manner fuel and air is admitted into mixing chamber 48 and through the orifices of groups B into the furnace for burning in accordance with the spray pattern shown in FIG. 7.
Similarly, the closing of contact 72 in response to a 40 percent load condition, for example, energizes relay 103 and closes switch 104, followed by the opening of fuel valves 60 and 62 by means of actuators 105 and 106, respectively. Fuel and air is thereby admitted through conduit 40 and 41 into mixing chamber 46 and through the orifices of group A into the furnace for burning in accordance with the spray pattern shown in FIG. 8.
Closing of the contacts 73, 74 and 75 causes each to close two of the three switches 85, 106 and 104. Thus by closing contact station 73 having two contact points, and in response to aSS percent load condition, for example, relays 82 and 99 are energized'and switches 85 and are closed, thereby opening fuel valves 67, 64 and air valves 68, 66 by meansof. the respective actuators This causes actuators 101 and 162' 90, 101 and 94, 102. This permits fuel and air to flow to mixing chambers and 48 thereby discharging a mixture of fuel and air through orifice groups C and B and obtaining aspray pattern according to FIG. 9.
Similarly closing of contact station 74 having two contact points, and in response to a percent load condition, for example, energizes relays 02 and 103 and causes switches 85 and 104 to close. This, in turn, opens fuel valves 67, 60 and air valves 68, 62 by means of the respective actuators 90, 105 and 94, 106. Fuel and air is thereby permitted to flow into mixing chambers 50 and 46 for discharge into the furnace by way of orifice groups C and A in accordance with spray patterns shown in FIG. 10.
In like manner closing contact station having two contact points, and in response to an percent load condition, for example, will cause energizing of relays 99 and 103 and switches 100 and 104 to close, which, in turn, will open fuel valves 64, 60 and air valves 66, 62. Fuel and air is thereby permitted to flow under pressure into mixing chambers 48 and 46, with a mixture of fueland air being discharged into the furnace through the orifices of groups B and A. A spray pattern is accordingly established as illustrated in FIG. 11.
Finally, in response to maximum load the closing of contact station 76 having three contact points will cause all three relays 82, 99 and 103 to be energized and all three switches 85, 100 and 104 to close. This, in turn, will open all the fuel valves 60, 64 and 67 and all the air valves 62, 66 and 68, permitting fuel and air to be discharged into the furnace in accordance with the spray pattern illustrated in FIG. 12.
Thus the invention provides a single burner and firing control having novel features which enable the operator to select a fuel spray pattern that is most suitable for the prevailing steam load conditions.
The invention has been described with a preferred fuel nozzle design in mind. However, other nozzles or nozzle tips, such as the one shown in FIG. 13, can advantageously be designed for use in practicing the invention. Furthermore, any suitable control system such as those of the hydraulic or pneumatic type may be employed in place of the electric system hereinabove described.
While I have illustrated and described a preferred embodiment of my invention, it is to be understood that such is merely illustrative and not restrictive and that variations and modifications may be made therein without departing from the-spirit and scope of the invention. I therefore do not wish to be limited to the precise details set forth but desire toavail myself of such changes as fall within the purview of my invention.
1. Aburner system for burning liquid fuel in a furnace at a variable combustion rate comprising a source of liquid fuel and gaseous medium for atomizing said fuel; a burner throat adapted to be provided in the wall of said furnace,
an elongated fuel nozzle of the gas atomizing type for delivering a mixture of liquid fuel and gaseous atomizing medium to said burner throat; said fuel nozzle having a nozzle tip at the furnace end thereof including a nozzle wall adapted to face the interior of said furnace; a plurality of orifices provided in said nozzle wall for discharging jets of a mixture of said fuel and atomizing medium into said furnace; said orifices comprising at least two groups, the orifices of each group being spacedly located on at least one imaginary line surrounding the longitudinal axis of said nozzle, with the lines of said groups being spaced from said axis at progressively larger distances; the axes of the orifices in each group being inclined to the longitudinal axis of said nozzle at an acute angle, with the size of said angle increasing with increasing distance from said nozzle axis; a multiplicity of mixing chambers for mixing said fuel and atomizing medium; means for operatively connecting each of said mixing chambers with one of said groups of orifices; conduit means for connecting each of said mixing chambers with said source of fuel and with said source of atomizing medium; flow control means cooperating with each of said conduit means to control the flow of fuel and atomizing medium to each group of orifices; and means for selectively operating the flow control means of each group of orifices as required by variations in said combustion rate.
2. The combination as defined in claim 1, wherein said plurality of orfices comprise at least three groups.
3. The combination as defined in claim 1, wherein the How control means cooperating with the group of orifices located a relatively long distance from said nozzle axis are operated for increased fiow therethrough in response to a demand for a relatively high combustion rate, the flow control means cooperating with the group of orifices located a relatively short distance from said nozzle axis being operated for a decreased flow therethrough.
4. The combination as defined in claim 1, wherein the flow control means cooperating with the group of orifices located a relatively short distance from said nozzle axis are operated for increased flow therethrough in response to a demand for a relatively low combustion rate, the flow control means cooperating with the group of orifices located a relatively long distance from said nozzle axis being operated for decreased flow therethrough.
5. The combination as defined in claim 2, wherein the flow control means cooperating with the larger number of groups of orifices are operated for increased flow therethrough in response to a demand for a relatively high combustion rate.
6. The combination as defined in claim 2, wherein the flow control means cooperating with the smaller number of groups of orifices are operated for increased flow therethrough in response to a demand for a relatively low combustion rate.
7. The combination as defined in claim 1 wherein said imaginary lines upon which said orifices are located form circles.
References Cited by the Examiner UNITED STATES PATENTS 2,106,310 l/1938 Warrick. 2,549,952 4/1951 Wheelock 236-1 2,919,122 12/1959 McConnell 15828 JAMES W. WESTHAVER, Primary Examiner.