US2411048A - Pressure atomizing oil burner - Google Patents

Description

Nov. 12, 1946. A, LOGAN rnassums A'roMIzmG OIL BURNER 2 Sheets-Sheet 1 Filed Oct. 4, 1944 mvsmon J 1.506115 Bu VUTTORNEYS Nov. 12, 1946.

J.'A. LOGAN 2,411,048

PRESSURE ATOMIZING OIL BURNER Filed Oct. 4. i944 2 Sheets-Sheet 2 INVINTOR MLOGHN *HTTORNEYS I Patented Nov. 12, 1946 PRESSURE ATDRHZING OIL BURNER Joseph A. Logan, Hadley, Mass, asslgnor to Gilbert & Barker Manufacturing Company, West Springfield, Mass., a corporation of Massachusetts Application October 4, 1944, Serial No. 557,119

2 Claims. (Cl. 158-28) This invention relates to a new structure and mode of operation in gun type oil-burners. The gun type burner is well known. It operates to pump oil under pressure through an atomizing nozzle, mix the spray with air supplied under pressure from a fan and to ignite and burn the carburetted air.

In the prior art much attention has been given to the emciency of the atomizing nozzle. An account of this is published in the Transactions of the A. S. M. E. of July 1939 under the title "Atomization of oil by small pressure atomizing nozzles. Reference to this publication will give a background to what is said about nozzles in disclosing this invention.

A main purpose of the invention is to provide a new gun type structure to burn oil from a relatively large nozzle at a low rate in the amount per hour. It is most useful in serving small heaters for domestic house and hot water heating.

In referring to the prior art, gun type burners are being considered. These are oil pressure atomizing burners.

Ordinarily the oil burning rate per hour is determined by the size of the atomizing nozzle. The small ratein present practice calls for a corresponding small nozzle size. Ordinarily the rate is not changed much in practice by changing the pressure for feeding oil to the nozzle. That pressure is commonly adjusted or determined in practice by what will give the most eilicient kind of a nozzle spray; any change of 2 provide for using in the new structure a practical dependable nozzle, sized to give a rate of one gallon an hour when used in the practice with prior art burner structures. The new structure will operate successfully with this nozzle at a rate substantially less than one gallon an hour, for example a rate of about one-half gallon an hour. The same structure will also operate successfully at the normal rate of one gallon per hour when such larger rate is .wanted. Thus a substantial range of burner rates. is available rate due to oil pressure being incidental to that purpose of efficient spraying. All this is indicated in the above publication. It is seen that the rate is made primarily by the size of nozzle. And it is seen that'the lowest rated nozzle of that published investigation is one gallon an hour. I know nozzles have been made for smaller rates than one gallon. But I known that as the nozzle sizes go below the size intended for one gallon, the expense of making them accurately for a desired smaller rate increases and there is a practical limit. There is another practical limit caused by the increasing liability of very small nozzles to clog up in use. The size for the one gallon rate has an orifice in the neighborhood of one hundredth of an inch in diameter.

According to one feature of my invention I provide for using a nozzle which would be altogether too large for the desired rate under the common practice and compensate for the oversize by cooperating structure to get the desired Y low rate when wanted. By way of example I which is most useful in providing for the lower rates.

An example of specific structure for embodying the principles of the invention will be understood frcm the accompanying drawings, the description and mode of operation to be disclosed in the description.

Referring to the drawings:

Fig. 1 is a side and Fig. 2 is a rear view of the new gun type burner to practice the invention; these views showing the casing partly broken away with some detail appearing in the assembled form;

Fig. 3 is a view looking at the front of the burner head of Fig. l but with an added element;

Fig. 4 is a sectional view on line 5-5 of Fig. 5, of a centrifugal clutch also seen assembled in side view. with other burner parts in Fig. 2;

Fig. 5 is a face view with an end plate removed, of the clutch of Fig. 4 showing one way of adjusting it for a range of timing operations;

Fig. 6 is a sectional view of a conventional atomizing nozzle such as used in gun type burners, the scale being enlarged considerably in the drawing of this element; and

Fig. 7 is a sectional view of a conventional oil pump by-pass such as used in gun type burners, the view is taken on a horizontal plane through the pump output of Fig. 2, some oil passages not particularly pertinent here being omitted.

The burner assembly of Figs. 1 and 2 has a casing i for a multi-vane fan 2 to drive air into cylinder 3. The fan is driven by direct shaft connection with motor 4. The motor has a shaft transmission to oil pump 5. In this transmission there is a centrifugal clutch 5 and a coupling 1. A transformer 8, electrical conduit 9 and stand IB are indicated and need no description.

The oil discharge conduit ll leads from the pump 5 -to an atomizing nozzle l2. The oil is atomized by the pressure of the oil through a nozzle structurelike that of Fig. 6. The nozzle is positioned axially of cylinder 3. It .may be screwed on the end of pipe 1 I, the latter being held by a member I3. As shown the member is a closure at the. rear end of a perforated cylinder H for which it serves as a support at that end, see Figs. 1 and 3. A spider held by screws through cylinder 3 supports .the member 13. Electrodes l5 pass through the member I3 with spark gap terminals adjacent the orifice of the atomizing nozzle. The member l3 may have as shown in Fig. 3, two air feed openings l6 through it. These openings are not large. They serve with sliding covers, merely indicated, to let a supplementary air supply .go through the member 13 when wanted and be completely closed when such supply is not wanted in any particular instance.

The perforated cylinder l4 provides a combustion chamber B. It is a cylinder having many perforations through which air is fed to meet the atomized oil spray. The air comes from the annular space A, the cylinder serving as a jacket around cylinder M to provide space A. The air fan will establish air pressure in jacket space A .and the air will feed to space B in a great many air pressure jets or streams. The front end of spaceB is open. The frontend of space A is shown closed by the spacing ring indicated there while therear end is open as the annular space between member l3 and cylinder3 is open, except for'the spider support before mentioned. The purpose of the small shuttered openings it through member 13 is to adjust for a small supplementary air supply. .much less than the amount of air fed through the perforations in cylinder M. The supple- Thelatter is always mentary supply should never be enough to change the dominant character of the radially moving air, forced through said perforations. The jacket receives substantially all the air fan supply, but

this statement is to be understood as not excluding a minor supplementarysupply through openings I6 directed parallel to the oil supply. One idea in the supplemental air supply is to have it meet the oil spray from the rear and break it up. For, example at less thanthe best oil pres-- sure for the best atomizing result per se, an operation involved in this" invention to beexplained, the tendency is for the oil spray to take a cup rather than a coneform. The supplemental air supply is directed at the cup form from the rear, breaks it up into a better condition to get mixed with the radially directed air .jets from the air jacket. The supplemental air supply is also useful in locating, to some extent, the point where the flame begins. The air supply radially directed from the air jacket, however, is always enough greater than the supplemental when the motor shaft l1 turns. The latter is fast to the'motor armature and the fan always turns with the armature. When the motor is switched off its armature having considerable momentum will turn the fan and the action is a gradual stopping of the -fan after the motor current is cut off.

On the hub l9, Figs. 4 and 5, three clutch driving shoes are mounted as indicated. These are driven by pins 2! carried by the hub. Each shoe is made of two parts 22 and 23. A separate screw 24 is threaded through each part 23. It has a counters'eat for its head the outer face of part '23. Itiwill be seen from Fig. 5, that with this construction, the parts 22 and 23 of each similar shoe can be held apart by adjusting screw 24. A pair of tensioned coil springs 25, each one arranged as a full ring in one of the opposite side face recesses, will tend to pull the parts 22 and 23 of the shoes together. But screws 24 will determine stopping points. When screws 24 are turned with tendency to go inwardly, parts 23 must move outwardly as the screw ends are always held against parts 22 by the springs. Such outward movement of shoe parts 24 will increase the tension of springs 25. When shaft l1 speeds up the tension of springs 25 will determine at what time or at what speed the mass of shoe parts 22 and-23 will be centrifugally moved out for the parts 23 to engage the driven part of the clutch.

The driven clutch part consists in the drum 26 fast on hub 21. The latter is mounted for free running on hub l9. It is held against coming off axially by the head of shaft screw 18. This screw I head is arranged in a recess, see Fig. 4, so it will not have any effective frictional contact tending to drive the driven part of the clutch. What friction occurs will tend to keep the screw in place. its having a thread direction for that purpose. This recess for thus pocketing the head of screw 68, is closed by a plate fastened to hub 21 to rotate with the latter. Suchplateis part of the connector end 2'fforming a part to join with the flexible shaft coupling 1' indicated in Fig. 2. This coupling positively connects the shaft of the oil pump 5 with the driven half of the centrifugal clutch above described. The result is that the motor is provided with a transmission to always drive the fan with its armature and a centrifugal clutch in the transmission to drive the oil pump only when the fan is at a desired supply to dominate the nature of the whole air supply to give the result as herein described from the radial feeding of air jets. The electrodes 15 and nozzle l2 may be adjusted from the positions shown and placedas a group at any desired position along the axis of chamber B. This is done by making slipping fits in the member support l3 for these parts.

Referring to clutch 6, suitable arrangements for it are indicated in Figs. 4 and 5. The motor slots of hubl9 as indicated. The hub can be easily assembled on and taken off shaft I! by the means described and a positive shaft drive for the hub is provided. The hub at its right side is fastened to the frame of fan 2, see Figs. 2 and 4. Thus the fan is positively driven and always turns high speed. The clutch can be adjusted for such a .has an opening connected to discharge conduit H, see Fig. 2. The pump has a. casting 30, as is usually provided with needed pump passages. The pressure regulating means or valve is mounted in this casting as in Fig. 7. Since the structure per se is generally known, it will ,be only very briefly described here. Outlet through nut 29 is normally closed byspring pressed valve 30a. The area of valve 30a is subject to the pump discharge pressure from passage 3|. does not open, being spring closed, until the pressure on its area. is sufficient to overcome the spring. When opened the action is to by-pass through suitable passages. enough of the pump The valve discharge to keep the pressure constant. "The by-pass is through openings 32 and 33, when they register. to conduit 34. The latter connects to the suction side of the pump. The one by-pass indicated is merely by way oi example. There may be others.

It will be clear that the quantity of oil bypassed is determined by the degree of pressure necessary to move the valve far enough against its spring to cause passages 32 and 33 to register more or less. Thus the discharge pressure is easily regulated by regulating the spring load on the valve. This is done by compressing spring 35 more or less by turning adjusting screw 36 one way or the other. Nut 31 is a sealing cap for the adjusting screw head. when adjusted the spring controlled by-pass device acts to automatically maintain the oil pressure of oil passing through nut at, constant. The pump is generally slightly oversize. When it starts to operate,

the burnerfeeding oil pressure is established 1 practically at the same time as the pump starts.

The tendency is toward excess pressure. This excess is prevented bythe by-pass action. And the oil is delivered with an atomizing nozzle pressure easily determined between wide limits by hand adjusting of the by-pass valve device. The description of one such device is given with the idea of merely illustrating the well-known principles involved in adjusting the oil pressure discharge from the pump as a separate element per se, of the combination.

A conventional atomizing nozzle in considerably more than full size is shown in Fig. 6. Assume that this one has a rate of one gallon an hour, in which case' the oil pressure under con ventional practice would be around one hundred 39. Then it feeds through small slots W in said surface. These are generally tangent to the upper circle of surface 35. They release the oil into the cone-shaped space above. This has an orifice M. It is around one hundredth of an inch in diameter. The action is for the oil from slots Mi to spin in the space to which it is released. The oil pressure is converted largely to oil velocity. The tangent direction causes the spinning. The restricted orifice does not stop the spinning but it acts to center the stream in an extremely small thread-like whirling mass. The further release of the .pressure from the oil in this stream as it expands beyond the orifice makes a second conversion of pressure to velocity. The angle of the opening above the orifice will give the action in a spray angle wanted in the burner. Reference to the aforesaid published article will show how much this nozzle art per se, is attended to up to a very recent time. The

practice has been and it has been much emphasized, to have oil burners get the most emcient attainable form or atomized spray. The nozzles are usually marked individually by their rate per hour of oil discharge when used at high enough pressure for their best eflici'ency. The user or his installing agent understands what this high pressure is to be if the nomlesare not actually marked to indicate the oil pressure with which the nozzle is intended under prior practice to be used for such efdciency. Of course as the pounds per square inch. Its action is for oil to feed along passage 38 to irusto-conical surface B, is ignited by spark gap indicated. The flame published article shows, the rate is afiected by viscosity of oil, which depends on the oil grade, and temperature. The general principle is to adiustevesoastousethe nonletoget the most eflicient spray atthemarked ra'teof oil consumption.

According to one of the ideas in my invention use is where under the prior art practice referred to, a nozzle size small enough to theoretically get the low burning rate wanted for a particular use such as heating hot water, would give too much 'nozzle trouble under general prior art burner practice.

Referring to my example; I will explain the principles involved in the structure and mode of operation. In Fig. 1, a conventional nomle i2 such as shown in Fig. 6 by way of example, sized for a one gallon rate according to prior practice can be used with advantage in my combination for a muchlower oil consumption rate Thestructure shown will accomplish my main purpose. The mode oi operation with the size of atomizing nozzle already given for the example, is as follows: The motor is switched on and ofl by the usual means. When it starts, the fan always starts the airstream at about the same instant, but the oil pump is idle in the beginning. After the air stream is fully underway, the oil pump is started and the atomizing nozzle starts spraying at practically the same instant. The clutch element d causes this timed relation of air and oil feed. The delayed oil spray starts from the rear portion or some intermediate portion along the axis of the space E, Fig. l. The air is forced in jets, from space A, into space B at all radial angles and meets the oil spray for mixing. The mixture, or carburetted air in space is made and the air and oil of the mixture for the flame support, continues to be supplied in the fashion described. The flame will start in the space E as the air fed is radially pressed in toward the axis of this space. This holds the flame in a compact mass form for burning mixture.

The conditions are all specially provided with the purpose of receiving the oil spray in such a way as to maintain a satisfactory fire even though the atomizing nozzle per se is working substantially below its known eillciency as a spray producing device. The nozzle size is deliberately chosen and the oil pressure to feed it from the pump is deliberately chosen, in the example given at about twenty-five pounds per square inch, so

that the'efiiciency of the spray per se is substantially less than normal. The normal pressure in prior art practice is about one hundred pounds per square inch for full spray emciency. This change is made from one hundredto twenty-five pounds pressure to get a lower volume of oil delivered to the flame during the time of burning and in lieu of meeting the troubles of a smaller nozzle orifice worked with much higher pressure to give commonly sought nozzle spray eiilciency, the change of pressure now being arranged to give the low volume of oil in the same time with less than full spray efiiciency. My structural armore practical nozzle size, i. e. an inexpensive one and large enough to avoid the clogging tendencies or smaller ones. The result is that it becomes practical to operate a gun type burner at 'a rate of about one-halfgallon per hour in oil burners are advertised with nozzles rated lower than one gallon per hour but they are not used much on account of the nozzle troubles referred to and the tendency in actual use is to avoid nozzles less than the one gallon ratio as I have stated.

With any nozzle construction, as the orifice size is decreased, and thus the oil spray volume is decreased, so far as it is practical size nozzle according to any prior practice it can'be used by my combination at a lower rate. For example attends the attempt to get a corresponding low rate of oil consumption well below one gallon an hour by merely'proportioning the nozzle orithe specific nozzle size I have referred to is one v rated at one gallon an hour. With that one I have reduced the oil rate to about a half gallon an hour. According to the same principles, when a practical nozzle appears for satisfactory use in prior art gun type burners, I can use that smaller one and yet continue to get a substantially smaller rate as compared to the prior art practice or mode of operation.

The apparatus shown in Fig. 1 will work with the nozzle and its ignition terminals positioned further to the left than the position shown. I prefer-now to have a position far enough back of the forward end of cylinder 3 to have the flame start well within space E for this reason. The flame then begins as a flame in a retort. It is at least partially within the space B. When this is so the radially directed air jets acton that portion of the flame. to condense it somewhat. I believe that the flame emerges from the front endof space B surrounded by an envelope of air which goes out with the flame. The preferred way of running is with a part of the flame burning well within space B as a retort and part of it burning outside as an extension of the flame inside such space.

With regard to the closures at the front end .of space A and the rear end of space B there is no objection to providing openings through these closures but they should not be large enough to spoil the eflect of the radial openings through cylinder M. The radial supply of air through this cylinder is a most desirable feature of the combination.

The combination in one aspect is arranged for efllciency of the prior art atomizing nozzle. But by doing that the rateof oil consumption is subfat flce in the prior burner constructions for such a rate.

Having disclosed my invention 1 claim: 1. In an oil pressure atomizing burner of the kind having an oil pressure atomizing nozzle, ad

jacent ignition means, power mechanism to pump the oil through the nozzle at a predetermined constant pressure, a fan to supply air, means to hold back the oil supply automatically unless the air supply fan is in substantially full operation,

an air tube to direct air from the supply fan to meet the oil adjacent the nozzle, the combination of a tubular cylinder, provided with many perforations closely spaced both circumferentially and axially and generally distributed over substantially the whole cylindrical surface, said cylinder being positioned inside and spaced from the air tube to form a jacket, the jacket being connected to the fan, for receiving substantially all of the air supply to be directed through the cylinder perforations in many small pressure jets, said nozzle being positioned axially to discharge directly into the rear portion and generally lengthwise of the cylinder across such jets, the perforated part of said cylinder extending from the place of oil discharge and far enough inside the air tube to substantially complete oil and air mixture inside the cylinder for both starting and continuing a substantial part of the fuel combustion in said cylinder before the mixture leaves the cylinder.

2. In an oil pressure atomizing burner of the type having an oil pressure atomizing nozzle with an orifice of a size to deliver at the rate of about one gallon an hour when the oil pressure is the apparently foolish purpose of decreasing the I stantially lowered. This eifect'alone would not be useful if the'result were to substantially de crease the efllciency of the burner. Such result does not follow, however, because the structure and mode of operation prevents it. The actual result is a good heating flame at the low rate of oil consumption in the gun type burner. And the oversize nozzle used avoids all the trouble which around one hundred pounds per square inch, an air supply fan, an air tube to direct the air from said fan to the oil, mechanism to pump the oil through the nozzle at a predetermined constant pressure which is adjustable, and means to hold back the. oil supply automatically whenever the air supply fan is not running at substantially full speed,- the combination of a tubular cylinder provided with many perforations closely spaced both circumferentially and axially and generally distributed over substantially the whole cylindrical surface, said cylinder being positioned inside and spaced from the air tube to form a jacket for receiving substantially all of the air around the cylinder, said jacket being adapted to direct the air through the cylinder perforations in many jets,- said oil nozzle beingpositioned to discharge directly into the rear portion and generally lengthwise of the cylinder across such jets, the

perforated part of said cylinder extending from.

the region of oil discharge and forwardly far enough to substantially complete oil and air mixture inside the cylinder,-sald burner combination being adapted to operate satisfactorily at an oil consumption rate substantially as low as onehalf gallon an hour when said mechanism is adjusted to provide an oil atomizing pressure as f low as about twenty-five pounds per square inch.

' JOSEPH a. mom.

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