US2515929A - Pressure atomizing liquid fuel burning system - Google Patents

Description

July 18, 1950 F. w. OFELDT PRESSURE ATOMIZING LIQUID FUEL BURNING SYSTEM Filed July 2, 1947 Patented July 18, 1950 PRESSURE ATOMIZING LIQUID FUEL BURNING SYSTEM Frank- W. Ofeldt, Carnot, Pa.., assignorto Homestead. Valve Manufacturing Company, Coraopolis, Pa., a corporation of Pennsylvania Application July 2', 1947, Serial No. 758,594

This invention relates generally to pressure atomizing, liquid fuel burning systems and more particularly to r method and apparatus for smoothing out the pressure pulsations of the atomizing liquid fuel burning system and maintaining the liquid fuel under atomizing' pressure to provide a shape. pressure reduction when the fiow of fuel is cut off. I V

This invention may be advantageously employed. in the pressure atomizing, liquid fuel burning system of a spray generating apparatus employed for cleaning or agricultural purposes. When a spray generating apparatus of this character is employed for cleaning purposessolutions of soap or other similar cleaning compounds are employed to make the spray mixture but when used for agricultural purposes solutions containing a germicide, fungicide, and insecticide are mixed with a conveyor liquid such as water to form solutions. The solution to be employed is fed in metered quantities to a heating zone where it is heated by a pressure atomizing liquid fuel burning system to which fuel is metered in quantities relative to the quantities of solutions fed. to the heating zone. The metered quantities of solution and fuel are soproportioned as to generate a vapor or steam pressure and form a spray mixture from the solution which mixture is composed of a liquid and the vapor of a liquid and when discharged to the atmosphere produces an atomized spray for the purpose of cleaning,sterilizing, spraying or other similar purposes for which the spray solution is intended. By properly proportioning themetered quantities of the solution and fuel the spray mixture may be varied to produce a fine atomized spray or a spray of relatively heavy liquid globules which would be considered a wet spray, the former being ideal for agricultural spraying whereas the latter is best suited for cleaning purposes as the force and erosive effect of the water droplets provides a superior cleaning action.

In the pressure atomizing liquid fuel burning systems employed in a spray generating apparatus of this character there is usually an air blower and positive displacement pump of the pulsating fiow type for metering the liquid fuel in proportioned quatities correlated with the metered solutions delivered to the. heating zone.-

When the pump and blower is stopped, either by stopping the prime mover or by means of a pressure or temperature control system, the pressure on the liquid fuel slowly decreases and. permits vthe fuel to issue from the burner at pressures 2 Claims. (Cl. 158--36.3)

lower than the fuel atomizing pressure andv the air from the blower materially decreases and gets out of phase with the amount of fuel delivered. Such a condition causes the fuel to burn slowly creating a. considerable amount of. soot and smoke; If the fuel pump is stopped this dribbling may produce an accumulation of the fuel within the combustion chamber causing the apparatus to give off soot and smoke when it is again started up. Such an accumulation of fuel within. the combustion chamber may find its way to other parts of the apparatus and catch fire causing the spray generator to burn up. Di-fierent types of apparatus and different methods. have been employed in an endeavor to eliminate this hazardous condition some of which have been partially successful but have not entirely eliminated these difficulties. It was discovered. that this problem could be overcome by conducting the liquid fuel under atomizing pressure through a particular type of flexible hose connected between the pump and the atomizing burner. Such a flexible hose may be constructed was to expand only in a longitudinal direction in order to maintain the. liquid fuel under atomizin'g pressure at the time that the fuel pump is stopped and the action of the flexible hose in contracting longitudinally will forcibly discharge the entire last slug of fuel through the burner at atomizing pressure thereby preventing any dribbling or other low pressure discharge of liquid fuel from the burner.

The principal object of this invention is the provision of method or apparatus for preventing the discharge of liquid fuel from the burner at a pressure lower than. atomizing pressure when the fuel supply is stopped.

. Another object is the provision of a flexible alleviating conduit in a pressure atomizing liquid fuel system that smooths out pressure impulses and maintains the final discharge of fuel under atomizing pressure when the fuel supply is shut off. 1

Another object is the provision of a flexible connection between the source of fuel supply and a fuel burner which permits independent manipulation'of the burner and also provides an alleviator which smooths out the. pressure impulses of the liquid fuel and maintains atomizing pressure on the fuel. discharged from the burner when the supply of fuel is shut off.

Another object is the provision of method and apparatus for the final discharge of liquid fuel from a blower type pressure atomizing burner at end of the shaft of the electric motor 20.

atomizing fuel pressure before diminution of the air supply.

Another object is the provision of method and apparatus for the final discharge of liquid fuel from a correlated air fuel atomizing type burner before the air supply is reduced to a position where smoke or soot may be produced.

Other objects and advantages appear hereinafter in the following description and claims.

A practical embodiment illustrating the principles of this invention is disclosed in the accompanying drawing wherein:

Fig. 1 is a diagrammatic view of a pressure atomizing liquid fuel burning system this invention.

comprising Fig. 2 is a view partially in section and partially broken away illustrating the flexible connection between the pump and the burner as shown in Fig. 1.

Referring to Fig. l of the drawing l represents a liquid fuel supply tank or reservoir which may be filled at the top through the opening-2 and is providedwith a drain cock 3 at the bottom thereof. The fuel burned in a spray jenny-apparatus 'ofthe character with which this system is emwith a plunger l3 driven by the connecting rod M which is pivotally attached at its ends to the plunger [3 and a crank [5 on the rotatably supported pulley It. A belt drive- IT i arranged to connect the pulley IS with the pulley l8 on the Although an electric motor is illustrated here as a prime mover any other suitable prime mover such as a gasoline or steam motor may be employed to operate the displacement pump ID.

The displacement pump [0 is also provided with an outlet check valve 2| arranged to permit the fuel to flow through the fixed orifice 22 and through the return pipe line 23 back to the fuel supply tank I. The orifice 22 thus provides a bypass for the positive displacementpump I0 which not only limits the pressure capable of being developed by the pump but also provides a constant pressure for the fuel discharged from the pump past the outlet check valve I2. The fuel passing the outlet check valve l2 isconveyed through the pipe line 24, the metering valve 6,

and the flexible hose connection 25 to the pipe line 26 and the vertically disposed pipe 21, the upper or free end of which has a liquid fuel atomizing burner jet 28 attached thereto. The liquid fuel atomizing burner jet 28 is provided with the deflector 29. A burner of this character is disclosed in United States Letters Patent 2,289,675, issued July 14, 1942.

The flexible hose connection 25 shown in detail in Fig. 2 is made up of a suitable elastomer inaterial such as natural or synthetic rubber or other plastic material having similar characteristics. It is preferable that the material be chosen so that it will resist the action of solvents normally found in fuels such as kerosene, gasoline, fuel oils, or other types of liquid fuels that may be employed for this purpose. The interior wall of the flexible hose as shown at 30 in Fig. 2 is relatively heavy and is made of the elastomer material. This wall is covered with a cross-braided sleeve made of wire or cord such as illustrated at 4 3|. A second layer of the elastomer material is ordinarily formed over the cross-braided sleeve 3| such as illustrated at 32. A second sleeve of similar cross-braided material is placed on the elastomer coating 32 as illustrated at 33 and this latter sleeve 33 is then ordinarily protected by a final coveringor coat of the elastomer material as illustrated" at 34. The 'cross braided cords forming the sleeves 3| and 33 are applied in constructing the flexible hose so that they cross one another at an acute angle less than longitudinally of the axis as shown and is preferably substantiallyv 82. These cross-braided or basket weave sleeves with the cords crossing at an acute angle permit the flexible hose to have material longitudinal expansion when subjected to an internal fuel pressure, its radial expansion being substantially nil. When the fuel supply to the hose is shut off the whole of the last slug of fuel is quickly discharged. If the braiding is such that internal pressures within the flexible hose will expand readily, it will not function to produce the desired results of maintaining atomizing pressure on the liquid fuel and the last slug of fuel is not forced through the burner quick enough. The flexible hose 25 is preferably constructed in such a manner that it will expand longitudinally instead of the radial expansion common to hose generally. Thus, the hose having predominant expansion longitudinally provides one means for solving the problem of eliminating the dribbling of fuel from the burner when the flow of fuel supply is shut off. ,7

It is preferable to employ permanently attached couplings such as illustrated at 35 on the ends of the flexible hose 25. In practice it has been found that when the fuel system is designed to supply liquid fuel under normal operating pressure of from 1'75 to 200 pounds per square inch this flexible hose should have an approximate bursting strength of not less than 600 pounds per square inch owing to the shock pressures produced by a pulsating pump. A hose of this character may have an internal diameter of onefourth of an inch and an external diameter of five-eighths of an inch. It has also been found that the two braided sleeves willproperly function when constructed of double-strand cotton. cords both of which are embedded within the elastomer material forming the flexible hose.

With a flexible hose of this character, wherein the braids are constructed to allow longitudinal expansion and contraction of the hose when the motor is started or stopped, the fuel will not issue from the burner in an unatomized state because of the sudden longitudinal contraction of the hose which action causes quick discharge of the whole amount of the last slug of liquid fuel and thus eliminates the slow discharge of residual capacity.

The motor 20 is also arranged to drive the blower 36 through the belt connection 31 and the air discharged from the blower passes through the air duct 38 to burner throat 39 from whence it is discharged upwardly around the deflector 23 and mixes with the atomized fuel burner jet 28.

When the prime mover, such as the motor 23, is shut off it rapidly decelerates and the air flow delivered by the blower quickly diminishes to zero. It is then necessary to provide a flexible hose 25 that will produce a final discharge before the air flow from the blower diminishes toa point where soot and smoke is produced. A predominantly radially expanding alleviator hose canit 5 function to eliminate soot and smoke in this manner.

I claim:

1. In apressure atomizing liquid fuel burning system, the combination of a source of liquid fuel, a liquid fuel atomizing burner, a positive displacement liquid fuel pump connected to continuously force the liquid fuel from said source through said burner to atomize it for burning, and a flexible hose forming a part of the liquid fuel conduit from the pump to the burner and constructed to expand axially but incapable of expanding radially beyond its normal radial dimension and effect a sharp flow cutoff when the supply of liquid therethrough is stopped.

2. In a pressure atomizing liquid fuel burning system, the combination of a source of liquid fuel, a liquid fuel atomizing burner, a positive displacement liquid fuel pump connected to continuously force the liquid fuel from said source through said burner to atomize it for burning, a blower connected to supply air to the atomized fuel, motor means to operate the fuel pump and blower which are adjusted to correlate the supply of fuel and air for proper combustion, and a portion of the liquid fuel conduit from the pump to the burner being a flexible hose constructed to expand longitudinally but incapable of expanding radially beyond its normal radial dimension When sub- 6 jected to atomizing fuel pressure and to quickly recover its original shape without further deformation to produce a single final discharge of atomized fuel from the burner before the air supply diminishes to a point where soot and smoke is produced when the motor means is stopped.

FRANK W. OFELDT.

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

UNITED STATES PATENTS Number Name Date 207,165 Cooper Aug. 20, 1878 1,066,936 McKechnie July 8, 1913 1,230,867 Gobb June 26, 1917 1,579,891 Sandoz Apr. 6, 1926 1,797,193 Kimmich Mar. 17, 1931 1,798,798 Leguillon Mar. 31, 1931 1,858,302 Marshall May 17, 1932 2,020,633 Dannenberg Nov. 12, 1935 2,156,296 Kline May 2, 1939 2,364,489 Taylor Dec. 5, 1944 2,362,822 Houser et al Nov. 14, 1944 2,396,059 Roberts Mar. 5, 1946 FOREIGN PATENTS Number Country Date 326,388 Great Britain Mar. 13, 1930

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