US2536556A - Liquid fuel supply system for internal-combustion prime movers - Google Patents

Description

Jan. 2, .1951 N. LAWRENCE o. l' g v LIQUID FUELv SUPPLY SYSTEM FORINIERNALLCOMBUSIION PRIME MovERs l Enea March 4, 1945 f Patented Jan. 2, 1951 :presse LIQUID FUEL SUPPLY SYSTEM FOR INTER- NAL-COMBUSTION PRIME MOVERS Owen Napier lawrence, Birmingham, England, assignor to Joseph Lucas Limited, Birmingham,

England Application March 1948,

serial No. 651,847

In Great Britain March 30, 1 945 s claims. (ci. 15s-36.3)

This invention relatos to liquid :fuel supply systems for internal combustion prime movers,` of the kind comprising a variable-delivery pump. one or more swirl-type nozzles for supplying the liquid fuel to a combustion chamber in the form of a spray, and controlling means responsive to liquid fuel pressure, and other conditions associated with the system (such as atmospheric pressure), for automatically regulating the quantity of liquid supplied to the nozzle or nozzles.

The requiredswirl of the liquid on emerging from the nozzle or nozzles depends in part on the velocity at which the liquid fuel is supplied, and to enable this velocity to be adequate under all conditions of now it is already known to supply the liquid to the nozzle or nozzles at a rate which is in excess of that required to meet load requirements, the excess liquid being returned to the system before emergence from the nozzle or nozzles.

'I'he object-of the invention is to provide a system of the kind above specified, having improved means for controlling the supply ofduid to, and

the return of excess fluid from, the nozzle or nozzles. x

The invention comprises a system of the kind aforesaid having in combination, a variable orice situated in the supply passage between the pump and the nozzle or nozzles,a deviceresponsive to the pressure difference at the opposite sides of the orice for actuating a pump controlling means, a second variable orifice in the return passage from the nozzle or nozzles, a second device responsive to the pressure differencel at the opposite sides of the second oriiice and adapted to co-operate with the first mentioned device for actuating the pump controlling means, and a valve situated in the return passage and responsive to the pressure diierence associated with the second orifice.

The accompanying diagram illustrates one mode of carrying the invention into effect.

In the diagram a indicates a variable delivery pump which may have any convenient form; but which is preferably of the swash plate type, the pump being adapted in any convenient manner to be driven by the prime mover (not shown) Vto be supplied with fuel. The pump a has combined with vit fluid-operable means for` automatically varying the pump output. Such means may consist as shown of a spring loaded piston b which is slidable in a cylindrical chamber c, and which is connected by a rod d to the angularly adjustable swash plate v(not shown) of thepump a. The end of the chamber c to the left of piston b communicates through a passage e with'the outlet f of the pump a, andalso communicates through a restricted -passage *g with the end of the chamber to the right of the piston. The latter end of the chamber c is provided with a venting passage h which at its outer end forms a seating i for a valve :i formed on or attached to cne end of .a Vlever 1c in a chamber m. When the valve :i is closed the liquid pressures at the two sides of the piston b are equal, and the piston is moved by its spring loading to a position in which the pump gives its maximum output. Opening of the valve i causes the pressure inthe right hand end of the cylinder to fall, whereupon the piston will be moved by the preponderance of fluid pressure in the left hand end of the cylinder in the direction for reducing the pump output until a new condition of equilibrium is reached. The lever Ic is supported at a position intermediate its ends by a ilexible diaphragm n which divides the chamber m into two compartments mi, m2,the compartment m1 being in communication with the pump inlet o or a sump (not shown) through a passage p, and the compartment m2 being in communication with the outer atmosphere through a passage q. Also the lever k is loaded by a spring r which tends to hold the valve 7' on its seating i, and by a capsule or other device as s which is responsive to atmospheric pressure and is situated in the compartment m2. Movement of the valve i by the lever k causes the output of the pump a to be varied.

The outlet f of the pump a is connected by a pipe or other passage t to cne or more swirl type the nozzle or nozzles as u, there is provided a variable orifice w adapted to set up between its two sides a pressure diierenee which is proportional to the rate of ilow of liquid fuel through this passage. The orifice w may be'formed by a spring-loaded closure member a: co-operating with a seating y, the closure member being slidable in a cylindrical housing z which contains the loading spring 2 of the closure member and communicates through a passageway 3 with the part of the passage t containing the seating. At opposite sides of the orice w the passage t is connected by branch pipes or passages 4to a pressure responsive device which, in the example shown, comprises a chambers divided into two compartments by a flexible diaphragm 6, the arrangement being such that the diaphragm is subject to the said pressure difference. A rod secured to the diaphragm 6 and extending through the ends of the chamber 5, acts at one end on the spring-loaded lever 1c carrying the valve i above mentioned. As the lever k is also acted on by the capsule or other device s which is' responsive to atmospheric pressure, the pump output (which is variable under the control of the valve j on the lever) depends on both atmospheric pressure and the difference of pressure at the oriiice w.

In the return passage 'u by which excess liquidY fuel is returned from the nozzle or nozzles u to the pump inlet o or the sump above mentioned, there is provided a second variable orice 8 which is essentially similar to the one above described. Thus, the orifice 8 may be formed by a spring loaded closure memberl 9 co-operating with a.

seating I0, the closure member being slidable in a cylindrical housing Il which contains the loading spring I2 of the closure member and communicates through a passageway I3 with the return passage. At opposite sides of the orice I the return passage o is connected by branch pipes or passages I4 to a second pressure responsive device which is also similar to the one above described. Thus, the second pressure responsive device comprises a chamber I5 divided into two compartments by a, flexible diaphragm I6, the arrangement being such that this diaphragm is subject to the pressure dinerence at the orice 8. The diaphragms 6, I6 of the two pressure responsive devices are interconnected by the rod 'I above mentioned, and the arrangement is such that the action of the second diaphragm i6 opposes that of the rst diaphragm S, that is to say the adjacent ends of the chambers 5, I 5 are respectively in communication with the higher pressure sides of the two orices w, 8.

Also there is arranged in the return passage o between the nozzle or nozzles as u and the second orifice 8, a normally open controlling valve il. Preferably this valve I1 is of the piston type, and is connected by a rod I8 to a spring-loaded diaphragm I9 dividing another chamber 20 into two compartments, the latter being connected by branch pipes or passages 2| to the return passage v at opposite sides of the associated orifice l. 'Ihe arrangement is such that when the pressure drop across orifice 8 in the return passage o exceeds some predetermined amount, the valve I1 is moved in the direction for retricting the ow in this passage. It will be assumed that the pump a is supplying the required amount of fuel to the nozzle or nozzles u with the prime mover at a given altitude. In this condition the forces exerted on the valve lever 1c by the spring r, the rod 1, and the capsule s will balance each other, and the valve lever will be in a position of equilibrium in which iluid leakage past the valve i relieves the fluid pressure in the right hand end of the cylinder c suiliciently to prevent movement of the piston b by its spring loading. With change of altitude, the variation in the air pressure acting on the capsule s disturbs the equilibrium of the valve lever 7c which is thereupon moved under the control of the diaphragm 6 in the direction for varying the pump output until a new condition of equilibrium is reached. Thus, with lowering of altitude the pressure exerted by the capsule s on the valve lever k is reduced with the result that the output of the pump is inliquid fuel flowing creased. This causes the pressure drop across the orlnce ab. and oonsequential movement of the diaphragm i which serves by acting on the valve lever lc through the medium of the rod I to move the valve lever into a new position of equilibrium. With of altitude the opposite eifeet is obtained in that the output oi' the pump a and-the pressure drop across the orifice w are appropriately redu It will be seen, therefore, that the diaphragm 6 which is responsive to the pressure drop acres the orifice w controls the movement of the valve lever k. Movement of the diaphragm I, however, is opposed by the diaphragm I6 which is responsive to the pressure drop acrom the orifice 8 in the return passage v. Consequently the pump a must at all times create across the oriilce w a pressure .drop sufficient to enableV the diaphragm 6 to overcome the opposing action of the diaphragm IB. As, moreover, the valve I1 in the return passage o serves to maintain the return ilow through this passage substantially constant, it follows` that the opposing action of the diaphragm I6 is also substantially constant, and as a result the amount of excess liquid fuel delivered by the pump through the return passage. The purpose of the controlling. means above described is to satisfy the requirement that the rate of supply of liquid fuel by the pump should be such as to provide always, in addition to the quantity of fuel required to meet the load requirements of the prime mover to be supplied with liquid fuel by the nomle or nozzles, an excess quantity equal to (that is, neither more nor less than) that which is returned from the nozzle or nozzles, and by my invention I am able to meet this requirement automatically in a very simple and satisfactory manner. The invention is not, however, limited to the example above described as subordinate details may be varied to suit different requirements.

Having thusdescribed claim as new and desire Patent is:

l. A liquid fuel supply System for an internal combustion prime mover, comprising in combination at least one swirl-type nozzle for supplying liquid fuel to the prime mover in the form of a spray, a liquid fuel supply passage connected to said nozzle and containing a variable orifice, a variable-delivery pump for supplying liquid fuel through said supply passage to said nozzle at a rate inexcess of that necessary to meet the load requirements of the prime mover, a. return passage into which the excess liquid fuel can flow before emergence at said nozzle, and which contains a scond variable orifice, means including a member forming a part of the pump for varying the pump output, pump controlling means operatively associated with the outputvarying member of said pum a device responsive to thetpressure dilference at the opposite sides of the first mentioned variable orifice for actuating said pump controlling means, a second devicev responsive to the pressure dill'erence at the opposite sides of said second variable orice and connected to the rst mentioned device so as to co-operate therewith for actuating said pump controlling means, a valve situated in said return passage, and means responsive to the pressure dierence at the opposite sides of said second variable orifice for actuating said valve.

2. A liquid fuel supply system as claimed in my invention what I to Secure by Letters claimhinwhicheachofthevariableoricesia:

t t corresponding increase of corresponds to the quantity of aque fomedbyesnrlnzloedednidobleeluremem- Thefollawing refereneesereofreoordin'the meotthlspetent:

G Uurrm sra-rms nm'rs Nuno Date Marshall Apr. 13, 1943 Muon et al. Nov. 18, 1943 Holley. Jr. Aux. 13, 1946 Chandler Nov. 6, 1946 Chandler i- Nov. 5, 1946 FOREIGN PATENT@ Country Date Great Britain Sept. 30, 1940 Greet Britain Apr. '1, i941

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