US2560941A - Multijet oil burner - Google Patents

Description

July 17 1951 A. J. FISHER 2,560,941

MULTIJET OIL BURNER Filed July 10, 1947 Ana/few 1.

4 Adv/neg Patentedv July 17, 1951 MULTIJET OIL BURNER Andrew J. Fisher, Sparrows Point, Md., assignor to Bethlehem Steel Company, a corporation of Pennsylvania Application July 10, 1947, Serial No. I759,953

2 Claims. (Cl. 299-140) My invention relates to new and useful improvements in burners, and particularly to high temperature burners of the type in which a liquid fuel is intimately mixed with steam or other atomizing agent.

In open hearth furnaces for making steel the bath is heated primarily by the-burner flame.

The greatest part of the heat transfer from the flame to the bath is by radiation, and because of refractory limitations, the flame must be placed close to the bath so that the major part of this heat will radiate directly from the flame to the bath.

The working efficiency of an open hearth furnace is especially dependent on the amount of heat extracted from the flame at the first and second doors nearest the burner, because any heat not transmitted in this part of the furnace will be carried over to the third, fourth and fifth doors and cause the furnace to burn in the ports and uptakes of the outgoing end, or else to suffer a loss in tonnage by a necessary curtailment in the amount of fuel used per hour. The problem, therefore, is to create a flame that will heat both the ingoing and outgoing ends of the furnace close to the burning point at the same time.

All of the reactions between the oil, steam and air cannot be completed at the first two doors. The only way to extract maximum heat from the flame at this point is to utilize the partial burning of the oilfor further cracking the mixture of oil and steam. This will give a flame of high luminosity due to the free carbon particles produced in the flame, thus increasing its black-body properties. As the amount of heat transferred by a flame is a function of its temperature and emissivity, or radiating power, any addition in flame luminosity will materially increase the radiation exchange between flame and bath.

, Since it is the incandescent carbon particles which produce this luminosity, the higher carbon fuels, such as tar, pitch and fuel oil, have considerably greater potential emissivity than natur`al gas, coke oven gas,`or producer gas. However, theburner nozzles should also be kept clean at all times, and fuels of the first type have been found to clog and dirty most of the usual nozzles with carbon deposits very quickly.

The area and shape of theclean burner nozzle and the pressure of the oil and steam determine the shape and conical angle of the flame, and hence the area of the flame envelope.

When burners become dirty, the nozzle area is usually reduced. Since the flow of steam is controlled by pressure, any such restriction in the burner will decrease the amount of steam. The lessened flame radiation of a dirty burner is therefore due to two fractors: (l) the reduction in the amount of steam used per gallon of oil; and (2) the increased premixing of the flame envelope and the air stream which lowers the luminosity of the flame. The resultant effect is a lowering of the flame radiation at the first and second doors, with the consequence of a double loss in production, one when the burner is operating in a dirty condition, and another when the furnace is off for refractory repairs caused by dirtyburners.

An additional complication is the fact that an eflicient open hearth burner must be able to develop a very high temperature non-luminous flame fcr the initial melting-down period, as well as a lower temperature and highly emissive luminous flame for the period after melting down.

Steam, air and blast furnace gas are the most common atomizing agents, and the factors of the kind, amount and temperature of the atomizing agent used have a particular bearing on the thermal decomposition of the fuel in respect to time.

Good mechanical mixing of the fuel and atomizing agent is also important, being necessary to produce a uniform flame, and is governed by the relationships between the mixer used and the temperatures of the fuel and the atomizing agent.

One object of my invention, therefore, is to provide a liquid fuel burner assembly which is capable of projecting a strongly luminous or nonluminous flame as desired.

Another object is a burner assembly which will remain clean and unclogged during the combustion of carbon rich fuels.

Another object is a burner assembly which can be readily adjusted or controlled from the ex- Fig. 3 is a sectionl taken on the line 3-3 of Fig. 2;

Fig. 4 is a vertical section of the mixer taken on the line 4-4 of Fig. 5;

Fig. 5 is a horizontal section of the mixer on the line 5-5 of Fig. 4; and

Fig. 6 is a section on the line 6-6 of Fig. 1.

Referring now to Fig. 1 of the drawings, the burner I p roper is provided with an outer tubular casing 2, of steel or the like, to the forward end of which is welded the circular steel end plate 3, having an upper central orice 4 through which the flanged embossed nose portion 5 of the forwardly tapering multijet nozzle 6, of fast heat conducting metal, preferably a bronze such as silicon bronze, or copper, is inserted and securely brazed as shown in Fig. 2. Said nose portion 5 is of considerable depth, and has a.

plurality of horizontal rows of parallel evenly spaced small circular discharge passagesl (nine such passages being shown), having flaring inner ends 8 communicating with the enlarged inner chamber 9 of the nozzle which is provided with interior threads I0 on the inner end thereof. v

The rear end of the tubular casing 2 is provided with a welded external annular flange II, to which is bolted or otherwise secured the flanged casting I2 (Fig. 6) divided by wall I3 into lower and upper chambers I4 and I5 connecting with the inlet pipe I6, distributor pipe I1 and outlet. pipe I8 for continuously circulat ing water or other cooling fluid within said cashearth ch'arge,^the three-way valve y29 is turned through v90 to divert theoil upwards into the atomizer 36, -where it `meets the tangentially entering steam and undergoes a swift whirling rotation and. thorough mixing. The resultant A steam conveyer pipe 22, as shown in Fig. l. Only the oil is thus diverted, and steam continues to ing 2. Said casting I2 is also provided with a stuffing box I9 through which projects the pipe 20, having its forward end screw threaded by external threads 2I into the threaded end of the nozzle 6. Within said pipe 20 is a steam and mixture conveyer pipe 22 of somewhat smaller diameter, having its forward end 23 beveled and outwardly flared and welded into the forward end of the pipe 20. Welded spacing members 24 and 25 hold the forward ends of the water distributor pipe I1 and the pipe 20 in lhorizontal position within the outer casing 2. f

Screw-threaded onto the rear end of the pip 20 is a large T 26, and centrally spaced therein and extending forwardly through the conveyer pipe 22 f or a considerable portion of its length is the inner fuel conveyer pipev21. which also serves to provide an annular channel around its outer surface for the passage through said pipe 22 of the steam or other atomizing agent,V

either alone or in a mixture with the liquid fuel, as hereinafter described. Connected to said T 26 and pipe 21 is a nipple 28, which connects in turn through three-way valve 29 to fuel supply pipe 38. 1

Said three-way valve 29 is connected by'pipe 3l, elbow 32, pipe 33, elbow 34 andfpipe 35 to the mixer or atomizer 36.v Said atomizer may be of the construction shown in my Patent No. 2,242,424, issued May 20, 1941, or other eilicient type, but I prefer to use with the present burner the cyclonic atomizer shown in Figs. 4 and 5 of the drawings annexed hereto, in which the fuel entry pipe 35 projects through the upper circular steel end plate 31,'to which it is welded, and

which end plate 31 in turn is brazed to the edges of the atomizer 36, which may be of bronze or other like metal. A pipe 38 is provided for ad- I mitting steam or the like through the spiral trough 39 tangentially into the mixing chamber 40 of said atomizer 36, the bottom aperture 4I of which is connected by the pipe 42 to the In operation, for melting down the open be supplied to the atomizer 36. It is readily seen "that the bottom'rowof the burner holes 1 will be rich infoil and the top row will be lean in oi1, with the' middle row of holes somewhere in between. f

The highratioof steam -to oil, and the preheated furnaceair'which is driven into the flame,`

cause quick burning of the top layers of the flame. action cracks the lower layers of the slow burning" rich o il flamexinto small particles of fre'e carbon which cause the flame vto be luminous, vwith. maximum ilameradiation. The flame is heavy and has a tendency to lay close to the bath, which maximizes heat transfer to theA bath andminimizes damage to the roof.

'I'he size and spacing of the nozzle holes 1, and

the length of the inner oil pipe 21 are all variables which may be changed to t the burner to any size of furnace, so as to produce flame radiations of equal and maximum intensity, as measured by a radiation pyrometerfat the rst and second doors ofl the furnace. Nozzle holes 2" in diameter, spaced 1/2" apart on centers, will be found suitable for an average burner.

For the atomizing agent, superh'eated steam at 375 F., at pressures from 100 to 150 lbs. per square inch, has been found very satisfactory, although a pressureas low as lbs. persquare inch hasbeen used. Moreover, compressed air can be further enriched with oxygen to any proportions'if higher intensity llames are desired. It is also possible to use one kind of atomization agent for melting down, and another for after meltingdown.

Thisburner runs from campaign to campaign without .getting dirty or having to be cleaned.' y Reasons for this'eiect are the small holes 1 which donotvallow radiation in the reverse direction to penetrate far into the holes, the veryeective directwater cooling of the holes, the high velocity vspecific structure and varrangement stated, but

Ivmay'- use such" substitutes, modifications, or equivalents thereof as are within the scope and spirit of the invention and of the appended claims. Y

meri-nus described my invention, what I 5 claim as new and useful and desire to protect by Letters Patent is:

1. A liquid fuel burner assembly comprising an outer tubular cooling jacket, concentric outer and inner fuel pipes within said jacket, a nozzle of highly heat conductive material within the cooling jacket and connecting to the forward end of the outer fuel pipe, said nozzle having a plurality of rows of spaced horizontal discharge passages, an external atomizer connected to the outer fuel pipe, means for supplying an atomizing agent to the atomizer, and selective valve and conduit means for supplying liquid fuel either to the atomizer or to the inner fuel pipe in accordance with the desired character of the flame.

2. A liquid fuel burner assembly comprisingan outer tubular casing forming `a water jacket, a nozzle having a plurality of small discharge passages within said water jacket, outer and inner fuel inlet pipes also enclosed within said water jacket but insulated therefrom by an air space, the outer fuel pipe being connected to the nozzle and the inner fuel pipe terminating short of the nozzle, an external atomizer wherein steam is introduced tangentially to the fuel and the mixture passes through the outer fuel pipe and the nozzle to produce a non-luminous flame, and a three-way valve connected in the fuel line 6 to the atomizer and the inner fuel pipe and arranged for terminating the flow of fuel to the atomizer and directing the flow of fuel into the inner fuel pipe to produce a luminous flame.

ANDREW J. FISHER.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 437,013 Black Sept. 23, 1890 759,750 Rosenthal May 10, 1904 784,505 Rush Mar. 7, 1905 904,911 Achee Nov. 24, 1908 952,372 Speer Mar. 15, 1910 1,026,815 Matteson May 21, 1912 1,102,329 Dunn July 7, 1914 1,141,721 Mastin June 1, 1915 1,337,328 Said Apr. 20, 1920 1,581,078 Mulroy Apr. 13. 1926 1,639,685 Coffee et al Aug. 23, 1927 1,769,266 Lusier July 1, 1930 1,842,877 Muller et al Jan. 26, 1932 1,952,236 Clawson Mar. 27, 1934 2,044,720 Fletcher June 16, 1936 2,419,336 Cress Apr. 22. 1947

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