US2974489A - Internal combustion engine apparatus - Google Patents

Description

March 14, 1961 P, C, HQLDEN ETAL 2,974,489

INTERNAL COMBUSTION ENGINE APPARATUS Filed July 5, 1957 flow rate.

United StatesPatent INTERNAL COMBUSTION ENGINE APPARATUS Paul C. Holden, Mission, Kans., and William A. English, Lees Summit, M0., assignors, by mesne assignments, to the United States of America as represented by the Secretary of the Air Force v Filed July 3, 1957, Ser. No. 670,844 1 Claim. (Cl. Gli-39.74)

This invention relates to a centrifugal liquid injection structure for an internal combustion power plant, more particularly to a centrifugal liquid injection structure for delivering liquid in nely Iatomized form, and has for an object to provide an improved structure of this type.

Heretofore, numerous rotary arrangements have been proposed employing centrifugal force for injecting liquid fuel or the like into a combustion chamber. These prior arrangements employed fixed area injection orices radially spaced from the center of the rotor. Hence the degree of atomization attained, assuming an adequate constant head of liquid is maintained, was preponderantly a function lof rotary speed. However, in practice, the liquid liow rate to the rotor and the rotary speed are widely variable to suit varying operating conditions. Hence the liquid head varies with rotary speed and liquid flow rate. Since, at a selected speed, the liquid head is reduced as the flow rate is reduced, the quality of atomization deteriorates accordingly. `On the other hand, if at a selected speed the liquid iiow rate is increased to a value higher than it can *be discharged through the orifice, the liquid will overflow. To sumrnarize, it can now be seen that with injectors having orifices of fixed area best atomization at any selected sneed of the rotor occurs at only one value of liquid In view of the above,'it is a further object of the invention'to provide a centrifugal liquid injection structure which effects a fine degree lof atomization over a wide range of rotattional speeds and/or liquid flow delivery rates. Y

Another object is to provide a centrifugal liquid injection rotor in which the effective area of the injection orifice is varied 4as a direct function of the liquid liow rate, so that increased ow rate can be accommodated by the rotor, thereby eliminating the possibility of overflow due to -overfilling of the rotor.

A Briefly, in accordance with the invention there is provided arotor having a plurality of radially extending tubular arms communicating at their inner ends with a a centrally disposed drurnand jointly rotatabletherewith. ,Each of the arms is provided with substantially identical liquid injection structure including an injection orice lprovided adjacent its outermost tip and controlled by a piston slidably received within the arm adjacent the orifice.. Hence, a description -of the operation of one liquid vinjection structure will suiiice toV explain the invention.

Liquid fuel is delivered by a stationary conduit to the interior of the 4drum and, Yas the rotor is rotated, the f uel will be urged into tbetubular arm by the centrifugal forces set up, to establish a liquid column. The piston is also urged radially outwardly by the .centrifugal forces in the-direction -to block the injection orifice. However, the forces urging the piston radially outwardly are opposed byfthe forces` acting on the liquid column in the arm so that the piston attains a balanced position in ice 2 which the injection orifice is partially opened. With constant fuel liow rate, should the speed of the rotor be increased or decreased, the centrifugal forces acting on the liquid column and the piston are proportionately increased or decreased, respectively, to momentarily maintain the piston in substantially the same balanced position. However, the change in fuel pressure `across the so far unchanged orifice area, causes a momentary increase or decrease in the rate at which fuel is injected from the orifice thus decreasing or increasing the fuel level in the arm. This causes the piston to seek a new equilibrium position. By proper design, a suitable large `liquid head pressure can be maintained in the column, regardless of variations in motor speed. For example, by properly proportioning the piston member so that its centrifugal force is somewhat less than that of the liquid column when the arm is completely filled, the piston member will be movable to completely unblock the orifice to increase the injection rate suiciently to maintain the height of the column of liquid to a value less than the length of the arm, thereby preventing liquid overliow from the drum. Accordingly, a high degree of fuel atomization is maintained through a wide range ofv rotor speeds. However, as the rate at which fuel delivered to the drum is varied, the height of the column of liquid in the arm is varied, thus moving the piston in the direction to increase the area of 4the injection orifice with increase in flow rate and in the direction to decrease the area of the injection orifice with decrease in ow rate. With this arrangement a consistently high degree of fuel atomization is attained, even though the fuel flow rate and/or the rotary speed of the rotor is varied. l

Although not specifically limited thereto, the improved centrifugal liquid injector is primarily applicable for injecting fuel into the combustion chamber of a gas turbine power plant and, when so employed, may be attached to the turbine-compressor rotor aggregate forv joint rotation therewith.

The above and other objects are effected by the invention as will be apparent fromthe following description and claims, taken in connection with the accompanying drawing, forming a part of this application, in which:

Fig. 1 is an axial schematic sectional view, with the lower radial portion omitted, of -a typical axial-How aviation turbojet engine having the invention incorporated therein;

Fig. 2 is a cross-sectional view taken on line Il-II of Fig. l, looking in the direction of the arrows; Y

Fig. 3 is an enlarged fragmentary sectional view taken on line Ill-III, looking in the direction of the arrows; and

Fig. 4 is a transverse sectional view taken on line IV-IV of Fig. 3. u

Referring to the drawing in detail, especially Fig. l, there is shown an internal combustion power plant which for purposes of illustration has been shown as an aviation turbojet engine 10 of the well-known axial ow type.

As is well known in the art, the engine is provided with an outer tubular shell 11 having an axial-flow air compressor section 12, a fuel combustion section 13 and a gas turbine section 14 disposed in axial alignment with each other Within the shell 11. provided with a bladed rotor 15 and a bladed stator 16 complementary therewith. The turbine 14, in similar manner, is provided with a bladed rotor 17 and a bladed stator 18 complementary therewith. Also, suitable liner structure 19 is provided, which, jointly with the outer q shell 11, `defines an annular passageway 20 for air liow.

through the engine.V The rotors 17 and 15 are connected The compressor section 12 is,

to each other for joint operation by shaft 21 and form a rotor aggregate which is suitably supported for rotation by means (not shown).

As thus far described, the engine operates in. a .wellknown manner to receive air througha forwardly directed air intake 22, which air is then pressurized in the compressor section 12 and thence delivered by the passageway 20 into the combustion section 13 wherein it is combined with fuel admitted thereto, in a manner subsequently to be described, to form hot motive gases which are then directed through the turbine rotor 17 to rotate the same and eventually are expelled through a rearwardly directed exhaust nozzle 23 to the ambient atmosphere in the form of a propulsive jet.

In accordance with the invention, there is provided a fuel injecting system 24 for admitting liquid fuel in highly atomized form to the combustion section 13. The fuel injecting system 24 comprises a rotor 25 mounted on the shaft 21 and having a drum 26 of circular shape. hc drum 26 defines an annular fuel receiving chamber Z7 having a forwardly directed opening 23 concentric with the shaft 21. A plurality of tubular arms 29 are attached to the periphery of the drum 26 and extend radialiy outwardly therefrom, as best shown in Figs. l and 2. Since the arms 29 may be identical to each other, only one of the arms will be described. The arm 29 is formed of generally circular cross-section, as shown in Fig. 4, and is provided with an elongated passageway 30 communicating at its inner end 31 with the drum 26 and extending outwardly therefrom the full length of the arm. The arm 29 is provided with a fuel injectioh aperture 32 adjacent its outer tip and within the arm 29 there is provided a tubular wall member 33 having an elongated bore 34 formed therein. Within the bore 34 there is slidably disposed a piston valve member 35 which divides the bore 34 into an outer chamber 36a and an inner chamber 36h. The outer chamber 36a communicates with the passageway 30, by means of a radially outwardly facing opening 37 formed in the wall member 33, and with the injection aperture 32. The chamber 36h is vented to the atmosphere by means of a small vent opening 38.

Fuel is directed into the fuel collecting chamber 27 by means of a fuel conduit 39 which is stationarily received in a hollow strut member 4t) extending across the air passageway 20. As illustrated, the strut member 40 is connected at one end to the outer shell 11 of the engine and extends through the core member 19, as best shown in Fig. l. The conduit 39 has a curved outlet end portion 41 which extends into fuel collecting chamber 27 through the opening 28 and is preferably directed (as shown in Fig. 2) in the direction of rotation of the rotor.

The combustion section 1'3 includes stationary outer and inner foraminated wall structures 43 and 44, respectively, of annular shape concentrically mounted relative to the axis of rotation of the shaft 21 and defining a fuel combustion chamber 45. The wall structures 43 and 44 are provided with radially disposed and spaced end walls 46 and 47, respectively, which jointly define an annular opening 4S for admitting fuel into the combustion chamber 45 for combustion purposes.

In operation, after the rotor aggregate (including rotors 15 and 17 and the shaft 21) is cranked by any suitable means (not shown) to start the engine, fuel is delivered to the conduit 39 by suitable fuel fiow regulating mechanisrn (not shown) in desired volume to sustain `operation of the engine. The fuel is directed into the fuel collecting chamber 27 of the drum 26 through the conduit outlet 41 and then, due to the rotary action of the rotor 25, the fuel is thrown in radially outward direction by centrifugal force into the arm 29. Concomitantly therewith, the piston valve member 35 is moved in radially outward direction by centrifugal force to momentarily block the orifice 32. The fuel column accumulating in the passageway 30. provides a head pressure effective through the opening` 37 to urge the piston valve member in radially inward direction, thereby to unblock the orifice. Since the forces acting on the piston valve 35 are in direct opposition to each other, the piston valve will assume a stable position somewhere between the maximum open position and the closed position, depending upon thc height of the liquid column in the arm, to permit fuel to ow from the passageway 30 through the opening 37 into the chamber 36a and thence to be ejected by the orifice 32 in finely atomized form. Since the aperture 32 is in rotary alignment with the annular opening 48 in the combustion section 13, the atomized fuel issuing through the orifice 32 will be directed into the combustion chamber 45 in suitable form for combustion.

During normal operation it may be desirable to increase the rotational speed of the rotor aggregate (17 and l5). During such increased rotational speed conditions, the centrifugal force acting on the piston valve 35 will increase, thereby increasing the radially outwardly urging effect thereon. However, since the rotational effect also increases the centrifugal force on the fuel column within the chamber 3ft in a similar manner, the net result upon the piston valve 35 is the same as before, so that its position remains unchanged as long as the height of liquid column remains unchanged. However, this change in rotational speed causes a momentary change in fuel pressure across the so `far unchanged orifice area and tends to change the fuel level. The piston value 35 will then moveto a new equilibrium position.

However, when it is desired to increase the thrust of the engine by increasing the rate at which the fuel is injected thereinto, the rate of fuel flow through the fuel conduit 39 is increased. Hence, a greater volume of fuel is momentarily collected within the arm 29 and the height of the fuel column is momentarily increased, thereby increasing the fluid force on the piston valve 35 in opening direction. During such conditions, the piston valve 35 moves radially inwardly to a new stable position in which the effective area of the orifice 32 is increased. At the new equilibrium position, the head of fuel above the outer piston `face will actually be decreased slightly. since less fuel force is required to balance the lower centrifugal force of the piston inertia in its inwardly moved position. The height of fuel in the arm 29, however, increases slightly. It will be seen that the fuel pressure decreases with increasing fiow.

Conversely, when it is desired to reduce the thrust of the engine, the amount of fuel delivered through the conduit 39 is reduced. During such conditions, the height of the liquid within the arm 29 is momentarily reduced, thereby reducing the force upon the piston valve 35 in opening direction and allowing the valve to move radially outwardly to a new stable position in which the effective area of the orifice 32 is reduced. Hence, even though the fuel flow rate to the engine is reduced, the pressure is actually increased slightly to maintain the high degree of atomization of fuel injected into the combustion chamber 49.

The vent opening 38 is effective to permit freedom of movement of the piston valve 35 within the bore 34 so that the piston valve is solely responsive to the force of the fuel column in the arm 29.

The piston valve 35 in the embodiment described is of greater specific gravity than the liquid fuel and, as illustrated, is of solid form. However, the exact density of the piston valve may be modified to suit the application regardless of the specific gravity of the material of which it is formed. For example, although not specifically shown, if the specific gravity of the material forming the piston valve is excessive for a particular application, the piston valve may be formed with a hollow interior or may be shortened in lengthwise direction for accurate performance.

If the density of the piston valve is less than that of the fuel, the piston valve will essentially oat in the liquid and the vent 38 to the atmosphere becomes unnecessary.

The collecting chamber 27 distributes the incoming fuel substantially at a luniform rate to each of the arms 29. Hence, adequate fuel distri-bution is assured in operation, obviating highly undesirable hot spots in the the combustion chamber 45. Also, since the head pres'- sure attained by the columns of fuel in the arms 29 is of a relatively high order, atomization of the fuel as it issues through the injection orices 32 is assured.

It will now be seen that the invention provides a fuel injection system for an internal combustion engine which delivers the fuel into the combustion section of the engine in finely atomized form over a wide range of rotational speeds and/or of fuel fio-ws.

It will further be seen that since the orifice 32 is variable by the sliding piston valve 35, the effective open area of the orifice 32 is not affected by variables other than the height of the liquid fuel in the anm 29. Also, since the piston valve is slidably mounted within the bore 34, and since the bore 34 has its outer chamber 36a lled with liquid fuel during all conditions of operation, the piston valve 35 will operate smoothly and with a minimum of friction.

Partial clogging of the injection orifice 32 by foreign particles is quickly cleared, since during such conditions the momentary decrease in effective area of the orifice causes the height of the liquid column to momentarily increase with :attendant movement of the piston valve in orifice yarea increasing direction.

While the invention has been shown in but one form, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various changes yand modiiications without departing from the spirit thereof.

What is claimed is:

In an internal combustion engine, wall structure deiining 4an annular fuel combustion chamber and having spaced portions defining an annular opening for permitting injection of liquid into said combustion chamber, a liquid injection 4rotor structure for injecting liquid solely by centrifugal Afonce in `atomized form into said combustion chamber through said annular opening, a conduit for delivering liquid to said rotor structure, said rotor structure being rotatable relative to said conduit vand said fuel combustion chamber, said rotor structure having a drum defining an open-ended liquid collecting chamber concentrically disposed relative to the rotational axis of said rotor structure, said conduit having an outlet opening disposed in said collecting chamber, a tubular arm having an elongated passageway communicating with said liquid collecting chamber and extending outwardly therefrom in radial direction, said tubular arm having a liquid injection orice communicating at a right angle with the radially outer portion of said passageway and disposed in rotary align-ment with said annular opening in the combustion chamber, a freely movable piston valve member cooperatively associated with said orifice `for modifying the eiective area of said orifice, a tubular wall member carried by said arm and defining a radially extending bore for slidably supporting said piston member, said piston member dividing said bore into first and second chambers, said rst chamber communicating with said passageway and said second chamber communicating with the atmosphere externally of said rotor structure, and said piston member being subject solely to the opposing forces of centrifugal force induced therein in one direction and the centrifugal force induced in the column of liquid in said passageway in the opposite direction to modify the 'area of said orifice, said piston having a mass of lower value than a mass of liquid equal to the volume of said passageway, and being effective to maintain the height of the column of liquid to a value less than the length of said passageway.

References Cited in the le of this patent UNITED STATES PATENTS 2,416,389 Heppner et al Feb. 25, 1947 2,568,921 Kroon Sept. 25, 1951 2,596,161 Murdock et al. May 13, 1952 2,622,394 Murdock et al. Dec. 23, 1952 2,627,718 Edelfelt et al Feb. 10, 1953 2,720,750 Schelp Oct. 18, 1955 2,861,425 Williams Nov. 25, 1958

Images