Leaf Spring Nozzle Flow Control

Abstract

A leaf spring nozzle flow control which is positioned in the nozzle body controls the flow of fluid to a fixed restriction nozzle such that the flow varies substantially in direct linear relationship with the pressure of the fluid. The flow control includes a plate having a plurality of leaf spring valves which are biased by the fluid pressure from a first position in which flow to the nozzle is blocked to a second position in which the fluid flows to the nozzle when the pressure of the fluid exceeds a predetermined minimum magnitude as determined by the leaf spring.

Description

BACKGROUND OF THE INVENTION

This invention relates to a nozzle flow control device and, more particularly, to a leaf spring flow control device for controlling the flow of fuel to nozzle injection orifices.

In the present fuel injection systems for jet aircraft engines and the like, the flow rate of the fuel to the injection nozzles is usually controlled by controlling the pressure in the piping system which supplies the pressurized fuel to the nozzles, the injection nozzles generally being of the fixed restriction type. Numerous difficulties have been encountered in such systems and particularly where there is a wide difference between the specified maximum and minimum fuel flow rates to the engine. Under such conditions the input pressure of the fuel nozzles at the minimum flow rate is frequently of such low magnitude that the flow is not susceptible of accurate control. Such condition particularly arises due to the fact that the flow rate from a fixed-dimension restriction, such as a fixed orifice nozzle, varies approximately as square root of the pressure of the fluid. Thus, by way of example, where the specified maximum flow rate is 500 pounds per hour at 500 p.s.i.g. and the specified minimum flow rate is 10 pounds per hour, the pressure of the fluid at the minimum flow rate would be 500/50.sup.2 or 0.2 p.s.i.g. Such low pressure is not only incapable of accurate control and produces rough and inefficient operation of the engine at low speeds, but also results in a maldistribution of fuel from the top to the bottom of the engine depending on the spacing in height or altitude of the various nozzles in the engine. For example, where the engine is 3 feet in diameter, the pressure at the bottom nozzles due to the head effect would be about 1.0 p.s.i. or five times greater than the pressure at the nozzles at the top of the engine during the minimum flow condition due to head effect. Such variation in pressure results in a fuel input at the bottom of the engine which is approximately 225 percent than the fuel input at the top of the engine. Also since the nozzles of the prior systems are generally in direct flow communication with the fuel delivery manifold, the fuel present in the manifold at engine shutdown usually drains to the combustion chamber and is wasted. Also on restart, before fuel injection commences a time lag occurs while the manifold fills.

In the past, various attempts have been made to overcome some of the above-mentioned difficulties in wide-range fuel-input turbine installations. One such attempt employs dual orifice nozzles of different sizes and employed alternatively to effect full-range operation. However, such additional nozzles complicate the fuel system, require additional maintenance and generally increase the expense of the turbine installation. Moreover, in many modern small turbine units which are found in use, by way of example in helicopters and auxiliary power units, the small orifices and the extremely low minimum flow rates in the fuel passages encountered during operation result in poor operation due to the levels of fuel contamination which are frequently encountered.

The nozzle flow control of my invention obviates these numerous disadvantages without necessitating the provision of dual nozzles to accommodate injection over a wide flow range. In the nozzle flow control of my invention, a resilient valve is positioned in the nozzle body which accurately controls the flow of fluid to the nozzle at both maximum and minimum flow rates. The flow control of my invention enables the minimum pressure of the fluid at minimum flow rates to be substantially increased to a magnitude which is accurately controllable. Such increase in minimum pressure minimizes the head effect due to engine diameter at the minimum flow rates as well as provides accurate control of the fuel flow rate. Moreover, the resilient valve of my invention prevents draining of the fuel manifold on engine shutdown and the fluid flow control device of my invention, when arranged in series with a conventional fixed flow resistance downstream thereof, effects a substantially direct linear flow to input pressure relationship which is ideal from the standpoint of gas turbine engine fuel control. The fuel control valve assembly of my invention is capable of easy and inexpensive manufacture and assembly and occupies a minimum of space so that it may be located directly within the body of a small fuel injection nozzle. Such location substantially minimizes the detrimental effects of flow differential due to head effect between the nozzles at the top and bottom of the engine which might occur if the nozzles are regulated from a common flow control separate and apart from the nozzles. The spring valve flow control of my invention may be employed to equal advantage with substantially any fixed-restriction-type spray head arrangement, including the swirl or flat spray or fixed restriction spray arrangements in which air is also mixed at the injection orifice, and substantially reduces the deleterious effect of fuel contamination.

SUMMARY OF THE INVENTION

In one principal aspect, the nozzle flow control device incorporating the principles of my invention includes a plate which is adapted to be mounted adjacent a fixed restriction orifice. A cavity is provided in one face of the plate and a pair of passages in the plate communicate between the periphery of the plate and the cavity and a slot. An elongated leaf spring is fixed in the slot and blocks communication between the passages when the pressure of the fluid falls below a predetermined magnitude and provides fluid flow when the pressure exceeds the predetermined magnitude.

In another aspect, the fluid nozzle assembly constructed in accordance with the principles of my invention includes a tubular nozzle body which is closed at one end and has a fixed restriction spray orifice in the closed end. A plate is positioned in the body and passages communicate with a chamber in the plate. Fluid delivery means is provided for delivering the fluid from a pressurized source to one of the passages the other passage communicates with the orifice. Elongated resilient means is positioned in the chamber and is moveable in response to the pressure of the fluid from a first blocking position to a second position in which fluid flows to the orifice.

In another principal aspect, a fluid nozzle assembly is provided which includes a nozzle body having a fixed restriction orifice and fluid delivery means for delivering a flow of fluid to the orifice from a pressurized source. Control means is carried in the body for controlling the flow of fluid to the orifice such that the volume of fluid delivered to the orifice varies in substantially rectilinear relationship with the input pressure of the fluid.

These and other objects, features and advantages of the present invention will be more clearly understood when considering the following detailed description.

BRIEF DESCRIPTION OF THE DRAWING

In the course of this description, reference will frequently be made to the attached drawing in which:

FIG. 1 is an exploded view of a preferred embodiment of nozzle flow control assembly constructed in accordance with the principles of my invention;

FIG. 1A is an end elevation view of the fluid delivery plate of my assembly taken along line 1A - 1A of FIG. 1;

FIG. 1B is a perspective view of the end of the nozzle body of my assembly;

FIG. 2 is an enlarged cross-sectioned side elevation view of the preferred embodiment of my assembly in its assembled form;

FIG. 3 is an enlarged and elevation view of the valve plate of my assembly;

FIG. 4 is a side elevation view of the valve plate taken along line 4 - 4 of FIG. 3; and

FIG. 5 is an exemplary plot of fluid flow v. input fluid pressure showing the flow-pressure characteristics of an orifice and the nozzle flow control of my invention arranged in series.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1 in particular, the components of a preferred embodiment of my nozzle flow control assembly are shown in exploded form. The assembly includes an adapter coupling 10 having an axial bore 11 extending therethrough and which is threaded at one end 12 to receive a fuel line from a pressurized source of fluid, such as the injector pump of a turbine fuel system. A flange plate 14 having a central opening 16 in one face thereof, is threaded to receive the threaded end 18 of the adapter. A tubular cup-shaped nozzle body 20 is adapted to receive a tubular cylindrical sleeve 22 therein and a valve plate 24 and fluid delivery plate 26 are adapted to be press fitted into the sleeve. The external surface of the nozzle body 20 adjacent its open end is threaded at 28 and the nozzle body is threadedly mounted concentric to the end 18 of the adapter on mating threads in a larger opening 30 in the flange plate 14. An air cap 32 is fitted over the other end of the nozzle body 20 for mixing air with the fuel as it issues from the nozzle body.

Referring particularly to FIGS. 1, 1B and 2, the nozzle body 20 is generally cup-shaped in form and a spray orifice 34 is formed in the closed end 36 of the body. A plurality of grooves 38 extend from the circumference of the nozzle body 20 to a point adjacent the orifice 34. The external surface of the nozzle body 20 includes a stepped shoulder 40 which is of slightly less diameter than the major portion 42 of the body, and a third portion 44 which is of somewhat less diameter than the shoulder 40. The air cap 32 is fitted over the orifice end of the nozzle body and pressed in place over the shoulder 40. The air cap 32 is generally cup-shaped, the closed end 46 of which bears against the closed end 36 of the nozzle body to cover the grooves 38 to define air passages with the grooves. The other end of the air cap includes a plurality of apertures 48 about its circumference for the entry of air. In operation, air enters the apertures 48, flows between the external reduced diameter portion 44 of the nozzle body and the inner surface of the air cap 32, through the passages defined by the grooves 38 and is mixed with the fuel issuing from the orifice 34. The mixed air and fuel then exits from an opening 50 defined in the closed end 46 of the air cap.

A converging bore 52 communicates between the orifice 34 and the interior of the nozzle body and terminates short of the body walls so as to define an annular shoulder 54 formed by the closed end of the nozzle body. The tubular sleeve 22 is slip fitted into the tubular portion of the nozzle body, as viewed in FIG. 2, and rests against and is matelapped to the shoulder 54.

The leading face 56 of the valve plate 24, which has previously been pressed into the sleeve, rests against the shoulder 54. The valve plate 24 includes a cavity 58 in face 56 which faces the orifice 34, the cavity 58 communicating with the wider end of the converging bore 52. The valve plate 24 is generally cylindrical in shape and includes a plurality of notched channels 60, 61 and 62 on its perimeter, the notched grooves extending in an axial direction through the thickness of the valve plate. As shown in FIG. 3, a plurality of elongated rectangular slots 64, 65 and 66 are formed in the plate extending from the perimeter thereof to a point within the plate, but in spaced relation to the cavity 58. The slots 64, 65 and 66 may be formed by cutting or sawing into the thickness of the plate. Narrower slots 68, 69 and 70 each extend from the internal end of slots 64, 65 and 66 to the perimeter and are formed only partially through the thickness of the plate, as by cutting or sawing, and elongated resilient leaf spring valve plates 72, 73 and 74 are firmly anchored at one end in each of the slots 68, 69 and 70 by the pressure exerted on the plate 24 when it is pressed into the sleeve 22, and the springs extend into slots 64, 65 and 66, respectively. Passages 76, 77 and 78 are bored between each of the notched channels 60, 61 and 62 and slots 64, 65 and 66 respectively and passages 80, 81 and 82 are bored from the peripheral edge of the plate and communicate slots 64, 65 and 66 respectively with cavity 58. The ends of the resilient leaf springs 72, 73 and 74, opposite their anchored ends, are positioned so as to resiliently block communication from passages 76, 77 and 78 when the fluid pressure is below a given minimum and produce a variable orifice effect with the passages as will be described in more detail later.

Referring to FIGS. 1, 1A and 2, the fluid delivery plate 26 is also pressed into the sleeve 22 and against face 84 of the valve plate. The fluid delivery plate 26 includes an axially extending bore 86 terminating in a recess 88 in the face of the plate opposite the valve plate 24. A washer 90 is positioned in the recess 88 so that when the adapter 10 and nozzle body 20, with the delivery plate 26 positioned therein, are screwed into the flange plate 14, a seal is formed between a knife edge 92 on the adapter end 18 and the washer, and the plates 24 and 26 firmly abut each other and the valve plate 24 and sleeve 22 are firmly held in position against the shoulder 54 of the nozzle body. A plurality of radially extending bores 94, 95 and 96 extend from the axial bore 86 to the edge of the plate and a plurality of notched channels 98, 99 and 100 extend in an axial direction from the end of the radial bores 94, 95 and 96 to the face of the plate adjacent face 84 of valve plate 24 and communicate with the notched channels 60, 61 and 62 of the valve plate.

In the assembly, the pressurized fluid enters the adapter coupling 10 and flows through bore 11 of the adapter, bore 86 of delivery plate 26, bores 94, 95 and 96, and the passages formed by the notched channels 98, 99 and 100 of plate 26 and the internal surface of sleeve 22. The channels 98, 99 and 100 are aligned respectively with the axially extending notched channels 60, 61 and 62 of the valve plate 24 since they are pressed together and the fluid flows into each of the passages 76, 77 and 78. If the pressure of the fluid is above a given minimum pressure which is sufficient to bias the resilient leaf spring valves 72, 73 and 74 to the open position as viewed in FIG. 3, the fluid enters the chambers formed by the slots 64, 65 and 66, the passages 80, 81 and 82 and thence flows into the cavity 58. In the embodiment shown, passages 80, 81 and 82 enter cavity tangentially so that the fluid entering the cavity 58 from the passages will swirl. The swirling fluid then passes through the converging bore 52 and is discharged from the orifice 34 where the discharge is mixed with the swirling air entering through the grooves 38 in the end of the nozzle body 20. The mixed air and fuel then issues forth from the opening 50 in the air cap 32 and into the combustion chamber of the engine.

It will be noted that the end of each of the notched channels 60, 61 and 62 adjacent shoulder 54 are closed by the shoulder. The slots 64, 65 and 66 also are closed along one side by the sleeve 22 and along the sides which open to the faces 56 and 84 of the valve plate by the shoulder 54 and the delivery plate 26, respectfully. The end of each of passages 80, 81 and 82 adjacent the edge of the valve plate 24 are closed in the final assembly by the internal surface of the sleeve 22 and the sleeve also forms a closed passage with the notched channels 60, 61 and 62.

The provision of the control provided by the resilient leaf spring valves 72, 73 and 74 enables the elevation of the minimum pressure of the fuel supplied to the adapter 10 to a magnitude which may be easily controlled, for example 10 p.s.i.g. rather than 0.2 p.s.i.g. as earlier mentioned. Where the pressure of the fuel is less than such elevated minimum, the resilient leaf springs prevent any flow to the orifice 34 and thereby prevents complete draining of the fuel manifold through the orifice on engine shutdown. Moreover, the increase in the minimum pressure provides for more accurate flow control and substantially reduces head effect while minimizing the effect of fuel contamination. When viewing FIGS. 2 and 5, it will be noted that the leaf spring valves operate, in effect to provide a variable orifice in series upstream of the orifice 34 such that the fuel flow through the assembly varies in a substantially rectilinear manner with the input pressure of the fuel upstream of the valve plate 24. Such input pressure relationship is more ideally suited for the fuel control conditions which are normally encountered in fuel turbine systems.

Although my invention has been shown with a nozzle of the swirl and air mixing type, it will be readily understood that the principles of my invention may be employed in other fixed restriction orifice nozzles and nozzles which are employed in other than fuel systems as well as nozzles of the nonmixing variety. However in passing, it should be noted that the flow control device of my invention is particularly suited for air-mixing-type nozzles of the type shown since such nozzles are readily capable of efficient mixing under low liquid flow rate operating conditions.

It should also be understood that the embodiment of the invention which has been described is merely illustrative of one application of the principles of the invention. Numerous modifications may be made by those skilled in the art without departing from the true spirit and scope of the invention.

Claims

What I claim is

1. A nozzle flow control device for controlling the flow of fluid through a fixed restriction spray orifice, said device comprising,

a plate which is adapted to be mounted adjacent the orifice,

an elongated slot in said plate extending from the perimeter thereof to a point within the perimeter of the plate,

a recessed cavity in one face of the plate which is adapted to communicate with the orifice,

a first passage in said plate communicating between the periphery of said plate and said elongated slot,

a second passage in said plate communicating between said elongated slot and said cavity, and

resilient elongated spring means having one end fixed and the other end of said spring means extending into said elongated slot and being moveable between a first position in which communication between said passages is blocked and a second position in which communication between said passages is established when the pressure of the fluid in the first passage exceeds a predetermined magnitude.

2. The device of claim 1 wherein said resilient spring means blocks communication between said first passage and said elongated slot in said first position.

3. The device of claim 1 wherein said resilient elongated spring means is a leaf spring.

4. The device of claim 3 wherein said leaf spring is fixed at said one end in a second slot in the plate.

5. The device of claim 1 wherein said elongated slot extends in depth through the thickness of said plate.

6. The device of claim 1 wherein said plate and said cavity are substantially circular and concentric.

7. The device of claim 6 wherein said second passage communicates tangentially with said cavity.

8. The device of claim 1 wherein said first passage comprises a notched channel in the perimeter of said plate extending between the opposite faces of the plate, and a bore extending between said notched channel and said elongated slot and substantially parallel to the opposite faces of the plate.

9. A fluid nozzle assembly comprising,

a tubular nozzle body closed at one end,

a fixed restriction spray orifice in said closed one end of said tubular body,

a plate carried in said tubular body adjacent said closed end, said plate having a chamber therein and first and second fluid flow passages communicating with said chamber,

fluid delivery means for delivering the fluid to be sprayed from a source of pressurized fluid to said first passage, said second passage communicating with said orifice, and

elongated resilient valve means in said chamber, said valve means being moveable in response to the pressure of the fluid from a first position in which fluid flow to said orifice is blocked to a second position in which fluid flows to said orifice.

10. The assembly of claim 9 wherein said first passage comprises a notched channel in the edge of said plate extending substantially parallel to the axis of said plate.

11. The assembly of claim 9 including a sleeve carried in said tubular body, said plate being positioned in said sleeve and said sleeve defines at least in part said first and second passages and said chamber.

12. The assembly of claim 11 wherein said fluid delivery means comprises a second plate positioned against said first plate to maintain said first-mentioned plate in position adjacent said closed end, said fluid delivery passage means in said second plate communicating with said first passage.

13. The assembly of claim 12 wherein said fluid delivery passage means is defined at least in part by said sleeve.

14. The assembly of claim 9 wherein said first and second passages and said chamber are defined at least in part by said nozzle body.

15. The assembly of claim 9 wherein said valve means comprises a leaf spring.

16. The assembly of claim 9 wherein said plate includes a plurality of said first and second passages, said chambers and said valve means, one of each forming a fluid flow path between said fluid delivery means and said orifice.

17. The assembly of claim 9 wherein said body includes second fluid delivery means for delivering a second fluid to the spray issuing from said orifice for mixing the fluids.

18. The assembly of claim 9 wherein said elongated resilient valve means blocks the flow to said orifice when the pressure of the fluid is below a predetermined magnitude.