US2407973A - Method and means for igniting liquid fuel - Google Patents

Description

p 1946. H. A. BECKSTROM 2,407,973

METHOD AND MEANS FOR IGNITING LIQUID FUEL Filed Oct. 25, 1941 FIG- 2 HmR l ggasmon ATTORNEYS Patented Sept. 24, 1946 METHOD AND MEANS F(I)R IGNITING LIQUID FUE Harry A. Beckstrom, Seattle, Wash, assignor to J. G. Frost, Seattle, Wash.

Application October 25, 1941, Serial No. 416,546

1 Claim. 1

My invention relates to a method and means for igniting liquid fuel, and is pertinent to those systems of burning liquid fuel and the like having a high flash point and in which a high pressure blast or stream of air is employed to distribute the atomized liquid fuel in the combustion chamber.

It is well known by users of oil burning equipment in which heavy oil is used that the problem of adequately igniting the fluid to initiate a flame has been one difficult to combat.

Various means have been employed and methods used for producing the preliminary ignition necessary to effect the functioning of the heavyoil burning equipment. 'A common practice has been the soaking of a handful of oil waste in a readily combustible substance, igniting it and tossing it into the path of the oil laden blast to be ignited.

Such a blast of air has great volume and velocity and will often extinguish the ignition means of the nature described or else make it ineffective by causing the igniter flame to be blown sideways away from the stream of incoming fuel laden air. The result is that a quantity of fairly large droplets or globules of fluid are spattered throughout the interior of the combustion chamber before ignition takes place and then, the volume of fuel present in the combustion chamber being abnormally great the consequent ignition creates what is known as a puff-back. Smoke and gases of combustion often pervade the boiler room. The operators of such equipment as has been described have, in many cases, resigned themselves to this puff-back as an inevitable condition that cannot be avoided. Naturally it is a disagreeable condition due to the fact that the exhaust conduit from the combustion chamber usually is of insufficient capacity to accommodate the increased volume of gases of combustion and smoke. These gases unburned as well as burned pass through the air passages around the burner and into the furnace room, the dirt or smoke generally producing an undesirable condition, if not a dangerous one.

It is an important object of my invention to provide a method of and means for igniting heavy liquid fuel that has been atomized in a blast of air by the provision of a secondary flame capable of and so directed and arranged as to successfully combat the pressure or force of the fuel laden blast to be ignited.

Another object of my invention relates to the provision of a secondary flame employing the low pressure principle of homogenizing fuel oil which will define a flame of the desired force and characteristics according to the foregoing object.

A further object of my invention is the provision of means for igniting a liquid fuel oil laden air blast which is simple to construct and operate and easy to maintain in operable condition and which will produce instantaneous ignition of the primary burner.

Other objects and advantages of the invention will be more apparent during the course of the following description which, taken with reference to the accompanying drawing, constitutes the disclosure of my invention.

In the drawing I have shown a preferred form of my invention but it is specifically pointed out and it is to be understood thatchanges and alterations may be made within. the scope of the sub joined claims without departing from the spirit of the invention.

Figure 1 is a schematic showing of my method of and means for igniting a blast of liquid fuel laden air and illustrating equipment that may be used,

Figure 2 is an enlarged view of the burner elements of Figure l.

Figure 3 is a wiring diagram showing this invention electrically connected in a typical circuit.

In a conventional system. employed for burning the heavier type of fuel oil it is customary to introduce the burner unit in a wall it! of a combustion chamber with the operating parts of the mechanism largely positioned exterior of the wall and the discharge end of the burner being directed inwardly in that wall.

A conventional oil burner comprises a fan i2 which may be enclosed in a housing Hi and through which air may pass through an inlet passage i i. Often the inlet E3 is provided with a damper id to govern the flow of the incoming air. The air leaves the housing through an inwardly directed air blast tube 28. It is quite often customary to encircle the blast tube 26 in spaced relation with a secondary air inlet tube 22 to prevent the creation of sub-atmospheric pressures and to insure free circulation of air.

The fan 52 is mounted on a shaft 24 that is rotated by the motor 26. It is a common practice to provide a hollow shaft for the element 24 and to associate it with a pump indicated at 28 having oil supplied thereto through the pipe 35) from a reservoir or tank 32. Rotation of the shaft operates the mechanism (not shown) of the pump 28 and applies a pressure to the oil flowing from the tank 32 passing it through the shaft and discharge end 34 into a centrifugal cup 36. Oil is thus discharged into a spinning cup and, through the action of centrifugal force, is caused to pass over the surface of the cup 3% in a thin stream. Whenthe oil flow approaches the edge 38 it is picked up by the air blast passing therearound and is conveyed into the combustion chamber with great force. I designate this as the primary blast or air stream.

The primary problem solved by my invention is the ignition of this blast of air which, in its initial stages starting from the at rest position of the fan, will include a multitude of fairly large droplets of oil that are cold and not at all easy to ignite.

My method of igniting this blast of fuel comprises the provision of an extremely hot clean and sharply defined secondary or igniter flame that is directed into the blast to be ignited with force sufficient to withstand the effect of the primary blast upon the contact to the end that instantaneous ignition occurs and the spattering of the combustion chamber by raw oil is elimininated. For accomplishing this result I employ a pump P preferably of a low pressure type, which has oil supplied thereto from the reservoir iii through the conduit 42 and air supplied thereto through the inlet Ml, metering valves $6 and may be employed to regulate the flow of the oil and air to the pump.

Operation of the pump results in a homogenizingof the oil due to the compressive action of the pump, which has been indicated as a vane type unit. The homogenized substance flows through the inlet tube 50 and is discharged through the terminal orifice 52. It is my practice to provide a generous sized orifice in this nozzle so as not to impede the flow of the igniter fluid, to reduce the effect of carbonization of oil that may be deposited upon the orifice in a fairly hot combustion chamber, and to define a generous flame The ignition of the homogenized stream of ma= terial passing through the orifice is effected by the use of the igniter electrodes 54 and 56 to which electrical current may be supplied from any suitable source. It is preferable in this system to employ a fluid oil having a low flash point so that. instantaneous ignition of the igniter fiame can be had.

The housing member 6! for the secondary nozzle 52 and electrodes 54 and 55 is let through the wall 10 of the combustion chamber to one adjacent the primary blast discharge. In the drawing it can be seen that this unit is directed angularly at the primary blast so that the flame it creates strikes into the primary blast with. force to effectively combat the unignited stream and produce the desired ignition.

Simultaneously with the flow of the primary blast to be ignited, the effect of the secondary or igniter flame is initiated.

This early and. efficient ignition of the primary blast is accomplished in certain cases by arranging that the ignition of the secondary flame occurs during the acceleration period of motor 25. Such motors as are customarily used in rotary oil burners for heavy fuel .oil require a brief period of time during which they come up to speed.

motor, a clean and Well-defined igniter flame is presented to the primary air blast as it increases in volume and, in consequence, in the amount of air-borne particles of fuel that it contains.

In certain instances the fuel line feeding to the cup 36 may be closed off by a valve during the starting period of the motor 26, which valve may be opened by any of the well-known centrifugal means which operate upon the occurrence of a predetermined rotary speed. In such a case, the valve would ordinarily be set so that it does not open until the cup is spinning with. sufficient velocity to insure atomization of the fuel oil delivered thereto. During the closed period of such a valve the igniter flame Will-be instituted ready to take effect as soon as oil is present in the primary air blast. 1

In Fig. 3, line current is delivered to motor M and motor 26, which are in parallel. Between motors M and 25 is the switch S for discontinuing operation of the motor M in response to combustion period. In parallel to motor M is the primary of the transformer T, the secondary of which is connected to the spark electrodes 54, 55. i

I claim:

A combustion control system including a heavy-oil main burner of the rotary atomizing type, a burner nozzle and ignition means therefor, said burner nozzle being located to one side of and directed at an acute angle into the discharge stream of said heavy-oil main. burner, a source of low flash-point fuel oil, a vane type rotary pump connected with said burner nozzle and having an air and oil inlet, fluid fuel conductor means between said source and saidoil inlet, means for energizing said main burner and means operable simultaneously therewith for rotating said vane pump to aerate and pressurize air and oil supplied thereto, means for activating said ignition means coincident with the discharge of air and fuel from said vaned pump, whereby an igniter flame is initiated having intensity and velocity to strike into and ignite the oil laden core of the discharging stream from the main burner.

HARRY A. BECKSTROM.

By starting the flow of fuel to the nozzle 52 and by instantly igniting that fuel during the period of delayed action of the primary

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