US3052089A - Afterburner control for dual injector turbine pump - Google Patents

Description

p 1962 M. F. ALEXANDER 3,052,089

AFTERBURNER CONTROL FOR DUAL INJECTOR TURBINE PUMP Filed March 21, 1958 4 Sheets-$heet 1 .EZEZZZQZ" Sept. 4, 1962 M. F. ALEXANDER AFTERBURNER CONTROL FOR DUAL INJECTOR TURBINE PUMP Filed March 21, 1958 4 Sheets-Sheet 2 EEZZZQF Sept. 1962 M. F. ALEXANDER 3,052,089

AFTERBURNER CONTROL FOR DUAL INJECTOR TURBINE PUMP Filed March 21, 1958 4 Sheets-Sheet 3 Sept. 4, 1962 M. F. ALEXANDER AFTERBURNER CONTROL FOR DUAL INJECTOR TURBINE PUMP Filed March 21, 1958 4 Sheets-Sheet 4 a J o J 0 ru 0 M M m w w w 4 w w W Z a 3 3 4 -kih 4 1 T 8 27\ 4 W M o w 4 w 4 mm. a M 4 4/ 4 4 a (U 0 no 0 My w w w w m w w m United States Patent Ofilice 3,952,089 Patented Sept. 4, 1962 3,952,039 AFTERBURNER @QNTROL FUR DUAL INJECTOR TURBINE PUMP Melville F. Alexander, Euclid, Ohio, assignor to Thompson Rama Wooldridge, Inc, a corporation of Ohio Filed Mar. 21, 1958, Ser. No. 723,027 2 Claims. (Cl. 60-356) This invention relates to a fluid flow control system, and particularly to an afterburner fuel control system for a turbojet aircraft engine. The illustrated embodiment of the invention comprises an air turbine pump and a control unit for controlling supply of fuel from the pump to a dual injection system in the tail cone of a turbojet engine.

It is an object of the present invention to provide an afterburner fuel control system which enables the pilot to shift from single to dual injection operation without danger of flooding or explosion.

It is a further object of the present invention to provide a control system for supplying fuel to a pair of fuel discharge devices and for causing the total of the flow rate to said devices to vary as a smooth function of an input variable over a region of transition from fuel supply to one device to fuel supply to both devices.

Another object of the invention resides in the provision of an afterburner fuel control system for varying the fuel supply rate in a predetermined manner as a function of compressor discharge pressure.

Still another object of the invention resides in the provision of a novel and improved afterburner fuel supply system and particularly in the provision of such a system wherein a single valve assembly is adapted to vary the supply of fuel to a dual injection system in a predetermined manner.

A further object resides in the provision of an afterburner fuel supply system having means for initating flow to a second fuel discharge device of :a dual fuel injection system simultaneously with movement of a fuel flow controlling valve member into a predetermined position.

Yet another object of the invention is to provide a novel and improved assembly comprising an air turbine driven fuel pump and a control unit for controlling supply of fuel from the pump to the afterburner of a turbojet engine.

Other objects, features and advantages of the present invention will be apparent from the following detailed description taken in connection with the accompanying drawings, in which:

FIGURE 1 is a diagrammatic illustration of a turbojet engine embodying an afterburner fuel control system in accordance with the principles and teachings of the present invention;

FIGURE 2 is a diagrammatic perspective view of an air turbine driven afterburner pump and fuel control assembly in accordance with the present invention;

FIGURE 3 is a further diagrammatic perspective view of the assembly of FIGURE 2;

FIGURE 4 is a somewhat diagrammatic longitudinal sectional view of the fuel control unit of FIGURE 2;

FIGURE 5 is a graph illustrating certain characteristics of a. fuel control system embodying the teachings of the present invention;

FIGURE 6 is a graph illustrating further character istics of a fuel control system in accordance with the present invention; and

FIGURE 7 is a simplified diagrammatic view illustrating the manner of operation of the fuel metering valve of the fuel control unit of FIGURE 4.

As shown on the drawings:

Referring to FIGURE 1, a turbojet aircraft engine is I indicated generally at 10 and includes a compressor section 11 supplying air to a combustion chamber indicated at 12. A turbine 14 is mounted on a common shaft 15 with the compressor section 11 and is driven by the products of combustion emanating from the combustion chamber 12 to drive the compressor section.

The engine is provided with a further combustion region indicated generally at 18 in the tail cone section 19 of the engine which is supplied with fuel by means of a dual injection system indicated generally at 20. The dual injection system may comprise an inner burner ring or core 22 and an outer burner ring or annulus 23, each of which is designed to discharge an annular stream of fuel into the combustion region 18.

Means is provided for controlling the supply of fuel to the dual injection system 20 comprisng a unitary assembly or package 30 including an air turbine driven fuel pump unit 31, FIGURES 2 and 3, and a fuel supply control unit 32. The fuel impeller section 35 of pump 31 is driven by means of an air turbine section 36 having a turbine mounted on a common shaft with the fuel impeller means. Fuel is supplied from a fuel tank to inlet 40 of the fuel impeller section and is delivered from the impeller section by means of a conduit indicated at 41 in FIGURE 2 connecting with fuel control unit 32. The turbine section 36 of pump 31 is supplied with air from compressor section 11 by means of a conduit indicated at 44 in FIGURE 1 connecting with an air inlet 45 of control unit 32. The air inlet 45 communicates with an air outlet 46, FIGURE 2, under the control of the unit 32, and the air outlet 46 connects with the turbine section 36 of the pump by means of a conduit indicated at 48 in FIGURE 2. The air supply from compressor section 11 via conduit 44 thus serves to drive the turbine section of the pump 31 to supply fuel under pressure to the control unit 32 via fuel conduit 41. The control unit 32 controls the supply of air to the turbine section of the pump to control the speed and hence the fuel discharge pressure of the pump.

The control unit 32 is suitably referenced to compressor discharge pressure by means of a line 52, and the fuel control unit is operative to vary fuel supply to the afterburner section of the engine as a predetermined function of compressor discharge pressure as will hereinafter be described in detail. The control unit 32 serves to control the delivery of fuel from fuel conduit 41 to core port 54 and annulus port 55 which are connected by means of conduits 57 and 58 with core burner secton 22 and annulus burner section 23 of the engine 10. The assembly 30 is designed to be controlled by means of a manual fuel flow demand lever which is suitably coupled with an input control shaft 76 of fuel control unit 32.

FIGURE 4 illustrates a preferred embodiment of the control unit 32 of FIGURES 1 to 3 and comprises a fuel inlet port 80 which connects with the fuel conduit 41 of FIGURE 2. Fuel flows from inlet 80 to ports 82 and 83 of a valve member 84 which is rotatably and axially slidably mounted relative to a sleeve 86 having peripheral slots -87 and 88 therein leading to respective annular chambers 9t) and 91. The chambers 90 and 91 connect with the core and annulus ports 54 and 55 shown in FIGURE 3 for delivering fuel to the core and annulus burners 22 and 23 of FIGURE 1 via passages 94, and 95, 96 and 97, respectively. The passage 94 communicates directly with the core port 54 and the passage 97 communicates directly with the annulus port 55. The valve body 84 is connected by means of spider portions 84a with a central shaft 100 which has an enlarged splined end portion 100a axially shiftable relative to a splined bore 76-12 of shaft 76. The splines key the shaft 100 for rotation with the shaft 76 while allowing axial movement of the shaft 100 aoeaosa relative to the shaft 76. As shaft 76 is rotated from an initial position in response to movement of a pilot operated manual fuel flow demand lever, valve body 84 is rotated and port 82 of the valve body registers with a progressively increasing area of the slot 87 in sleeve 86 to tend to deliver more fuel to the core burner 22.

Fuel supply passage 94 is referenced to a chamber 103 defined by a diaphragm 105 and an axially expansible and contractable bellows 107 by means of passages 109 and 110. Inlet 80 is referenced to a second chamber 112 defined by diaphragm 105 and a similar bellows 113 by means of a passage 115. Thus, as valve body 84 is rotated to increase the area of registration between port 82 and slot 87 in sleeve 86, the pressure in annular chamber 90 will tend to increase relative to the fuel pressure at inlet 80 to tend to cause diaphragm assembly 120 between chambers 3 and 112 to move to the left. Spring 121 acting on lever 122 causes lever 122 to tend to rotate about its pivot 124 in a counterclockwise direction to follow movement of end 120a of diaphragm assembly 120. End 1220 of lever 122 thus tends to move closer to discharge orifice 125 and further away from discharge orifice 126. This tends to increase the pressure in air valve control chamber 130 and decrease the pressure in control chamber 131 causing piston assembly 133 to move to the right and causing air valve member 135 to uncover more of the inlet 46 to the air driven turbine section 36. Air from the compressor enters inlet 45 as indicated in FIGURE 1 and is delivered into chamber 140, FIGURE 4, from which it travels past edge 135a of air valve 135 and enters air outlet 46 for delivery by conduit 48, FIGURE 2, to the turbine section 36. The chamber 140 communicates with air control chambers 130 and 131 by means of passages 143, 144 and 145, and 143, 146 and 147, respectively, under the control of adjustable valve members 150 and 151. The chambers 130 and 131 communicate with discharge orifices 125 and 126 via passages 145 and 1 53, and 154, respectively, and air downstream of orifices 125 and 126 escapes from the control unit via a passage 156.

Thus, when shaft 76 is rotated to demand more fuel, diaphragm assembly 120 causes air valve member 135 to supply more air to the turbine section 36 to increase the discharge pressure of the pump section 35, until the pressure in chamber 112 referenced to the fuel inlet 80 reaches a predetermined value in relation to the pressure in core annular chamber 90. The value of the pressure differential which is maintained between chambers 112 and 103 is determined by means of a set screw 160 which has an end portion 160a for varying the compression of spring 121. The screw 160 thus serves to control the pressure drop across the metering orifice defined by the registering portions of port 82 and slot 87 For closing air valve 135 in a predetermined angular position of shaft 76, the shaft 76 is provided with a earn 164 secured to the shaft by means of a nut 165 to be rotatable therewith and having an eccentric portion indicated at 164a for normally maintaining a pin 168 in the raised position shown in FIGURE 4 relative to end 122b of lever 122 against the action of a spring 169. When the shaft 76- is in its inital angular position closing the metering orifices defined by ports 82 and 83 and slots 87 and 88, cam portion 164a is out of registry with pin 168, so that spring 169 maintains pin 168 in a depressed condition where end 168a of pin 168 maintains lever 122 in an extreme clockwise position closing discharge orifice 126 and thus maintaining a high pressure in air control chamber 131 to maintain valve 135 in closed position. As soon as shaft 76 is rotated to demand fuel, cam section 164a engages pin 168 to raise the same to the position shown allowing complete freedom of movement of lever 122 between discharge orifices 125 and 126.

Shaft 180 of diaphragm assembly 120 extends within annular bellows 113 and is connected with a diaphragm assembly 181 by means of a collar 183 and nut 184. The

1.2. collar 183 is fixed with respect to shaft 180 so that the diaphragm assembly 181 is rigidly coupled with diaphragm assembly 120. The diaphragm assembly 181 is interposed between a pair of chambers 200 and 201. Chamber 200 is referenced to turbine inlet air pressure which exists at air outlet 46 leading to the turbine impeller section 36 of pump 31 by means of a port 205. Chamber 200 communicates with chamber 201 via passages 207 and 208 under the control of a valve member 210 which is adjustable by screw means 212. Thus, under stable conditions, the pressure in chambers 200 and 201 will be equal to turbine inlet pressure, and diaphragm assembly 181 will not affect operation of diaphragm assembly 120. If, however, the pressure in chamber 103 should increase suddenly relative to the pressure in chamber 112, causing a sudden opening movement of valve 135 and a consequent sudden increase in turbine inlet air pressure, this increased turbine inlet air pressure would momentarily cause a pressure differential between chambers 200 and 201 which would be equalized under the control of valve member 210 over a predetermined time period during which further movement of diaphragm assembly 120 tending to further open valve 135 would be resisted. The system including diaphragm assembly 181 and chambers 200 and 201 thus constitutes a flgedback system for stabilizing operation of the air valve In the illustrated embodiment, fuel is not supplied to the annulus burner 23 until a predetermined angular position of shaft 76 is reached, at which position a raised cam shoulder 76c moves out of registry with a valve member 225 to allow the valve member to assume an open position under the urging of a spring 226. Before this angular position of shaft 76 is reached, valve member 225 restricts communication between passages 228 and 229 to provide a relatively low pressure in chamber 233, passage 228 referencing chamber 233 to pressure in annular chamber 91 downstream of valve 84 and upstream of annulus burner 23. A chamber 236 is referenced to fuel inlet pressure by means of a passage 238 communicating with fuel inlet Diaphragm assembly 240 IS responsive to the differential in pressure between chambers 233 and 236, and with valve member 225 in the flow restricting position shown in FIGURE 4, valve member 242 is held in open position relative to valve port 243 and provides a relatively high pressure in chamber 246. Fluid flows from chamber 246 to passage via orifice 252 so that the pressure in chamber 246 is normally intermediate fuel inlet pressure and the pressure at passage 95. With valve member 225 in full restricting posit on, a relatively high pressure exists in chamber 246 relative to the pressure in passage 95 so as to bias valve member 254 to the left against the bias of spring 257 to close valve ports such as indicated at 254a between passages 95 and 96 to cut off the supply of fuel to the annulus burner 23. A spring 260 may be provided tendmg to urge valve member 254 toward closing relation but allowing opening of ports 254a by spring 257 when valve member 225 is moved to open position.

When input shaft 76 has moved to a predetermined angular position, cam portion 76c moves out of registry with valve member 225 and valve member 225 moves to an open position to apply pressure from chamber 91 to chamber 233 tending to move valve member 242 toward restricting relation to orifice 243 to tend to decrease the pressure in chamber 246. Reduction of pressure in chamber 246 allows valve member 254 to move to the right tending to open ports 254a and supply fuel to the annulus burner via passages 96 and 97 and conduit 58 shown in FIGURE 1.

Screw means indicated at 270 is operative to adjust the force exerted by spring 271 against diaphragm assembly 240, so that adjustment of this screw means 270 adjusts the pressure drop across the annulus metering orifice defined by the registering portions of port 83 and slot 88.

For varying the rate of flow of fuel to the afterburner in accordance with compressor discharge pressure for a given angular position of shaft 76, a chamber 300 is referenced to compressor discharge pressure by means of a port 303 and line 52 illustrated in FIGURE '1. The chamber 300 is bounded in part by annular bellows members 305 and 306 and a cup member 307. A vacuum chamber 309 is defined by plate 310, bellows 306 and 313 and end wall 307a of member 307. Plate 310 is connected with a pin 317 abutting a flapper valve 320 in chamber 321. As compressor discharge pressure increases, the pressure in chamber 300 increases to tend to move plate 310 to the right, shifting pin 317 connected with plate 310 to the right to actuate flapper valve 320, which is pivotally mounted by means of a double leaf spring arrangement 322 in chamber 321.

Chamber 321 is referenced to fuel inlet 80 via a passage 330, metering orifice 331, passage 332 and orifice 333. Fuel is bled from chamber 321 through a metering orifice 236 and a passage 237 to a further passage 339 connecting with the pump inlet 40 seen in FIGURES 2 and 3. The pressure in chamber 321 is thus intermediate pump discharge and pump inlet pressure and is referenced to a chamber 350 by means of passages such as indicated at 351 in a piston member 352. The pressure in chamber 350 acts on one side of a piston assembly 360, while fuel pressure from passage 339 is referenced to a chamber 362 by means of a passage 363. A central area 360a of piston assembly 360 is exposed to fuel discharge pressure from fuel inlet 80. It will be observed that piston assembly 360 is connected with valve shaft 100 by means of a connector 362 so that if piston 360 is shifted axially, valve body 84 will likewise shift axially. Slots 87 and 88 in sleeve 86 are of such a configuration that shifting of the valve body 84 to the left will increase the area of the metering orifices leading to the core and annulus burners, for a given angular setting of input shaft 76. As compressor discharge pressure increases in chamber 300, plate 310 moves to the right moving pin 317 against flapper valve 320 which in turn moves piston member 352 to the right against the action of a spring 370. Movement of flapper valve 320 to the right tends to restrict an orifice indicated at 372 downstream of OI'fiJlCC 333 to tend to decrease the pressure in chamber 321 and consequently in chamber 350 and thus to cause piston assembly 360 and valve member 84 to move to the left. Movement of piston assembly 360 to the left compresses spring 370 to move flapper valve 320 to the left opening orifice 372' and increasing the pressure in chambers 321 and 350 until equilibrium is restored.

It will thus be understood that the valve body 84 shifts angularly in reponse to rotation of shaft 76 and shifts axially in response to changes in compressor discharge pressure introduced at 303 so as to be capable of providing a fuel supply rate varying as a function of an angular input and as a function of compressor discharge pressure.

FIGURE 5 is illustrative of a typical performance characteristic for the control unit of FIGURE 4 and represents a plot of fuel flow in pounds per hour divided by compressor discharge pressure in pounds per square inch absolute as a function of power lever angle in degrees. It will be understood that the variable power lever angle refers to the pilots manual fuel flow demand lever angle. Angular movement of this lever is transmitted by means of a suitable remote control system to cause angular movement of input shaft 76 of the control unit shown in FIGURE 4. It will be observed that the ratio of fuel flow to compressor discharge pressure is illustrated as increasing over the range where fuel is supplied to the core burner only between power lever angles of 90 and 115, after which core fuel supply is illustrated as leveling off at a ratio value of approximately 165. Above the ratio of fuel flow to compressor discharge pressure increases at a uniform rate, while below 110, the variation of the ratio with power level angle is a function of compressor discharge pressure in the range from 15.3 pounds per square inch absolute to 39 pounds per square inch absolute, curve 401 representing the variation for a compressor discharge pressure of 15.3 pounds per square inch absolute, curve 402 illustrating the variation for a compressor discharge pressure of 2.6 pounds per square inch absolute and curve 403 illustrating the variation for compressor discharge pressures of 39 pounds per square inch absolute up to a maximum of 170.6 pounds per square inch absolute. It will be understood from this curve that fuel flow is to increase as a function of compressor discharge pressure, and in the range of from 110 to for example, fuel flow is to be a linear function of compressor discharge pressure. Such a fuel flow characteristic may be obtained by the control unit of FIGURE 4 by arranging the metering orifices defined by the ports 82 and S3 and slots 87 and 83 so as to provide a progressively increasing area as the valve body 84 is shifted axially to the left with increasing compressor discharge pressure in chamber 300 and by providing a progressively increasing area of the metering orifices as shaft 76 is rotated in the direction of the arrow 405 in FIGURE 4. It will also be noted that for compressor discharge pressures of 39 pounds per square inch and above, fuel fiow is to be a linear function of power level angle at a given compressor discharge pressure for angles above 100.

FIGURE 6 illustrates further characteristics of a preferred embodiment in accordance with the present invention wherein the ratio of fuel flow to compressor discharge pressure is plotted as a function of power level angle for compressor discharge pressures in the range of 39 pounds per square inch absolute and above. Curve 410 represents the core fuel flow While the curve 411 illustrates the annulus fuel flow and the dash curve 412 illustrates the sum of annulus and core fuel flow for power level angles beyond 115. It will be observed that in a system in accordance with this illustrated embodiment, it is contemplated that at a power level angle in the neighborhood of 115, core fuel flow to the core burner (for a given compressor discharge pressure) will be sharply reduced as fuel begins to be supplied to the annulus burner. This provision prevents flooding or explosion at the time that fuel begins to be supplied to the annulus burner. It is contemplated that the core fuel characteristic may be variable from the curve represented by lines 403-415416 in FIGURE 5 to the curve represented by lines 410, 420 and 421 in FIGURE 6, so that the fuel flow rate to compressor discharge pressure ratio will be adjustable between the limits of and for power level angles in the neighborhood of 115 and above. By this means, the total afterburner fuel flow rate may be a substantially linear function of power lever angle as represented by the lines 410a and 412 in FIG- URE -6.

FIG. 7 is a simplified diagrammatic view illustrating the manner in which the ports 82 and 83 and the slots 87 and 88 cooperate to define variable area metering orifices controlling fuel delivery in the control unit of FIGURE 4. As the valve body 84 is rotated in the direction of the arrow 405 in FIGURE 4 by means of shaft 76, ports 82 and 83 move in the direction of the arrows 430 and 431 relative to slots 87 and 38 in FIGURE 7, while as compressor discharge pressure in chamber 300 increases and valve body 84 moves axially to the left in FIGURE 4, the ports 82 and 83 move in the direction of the arrows 433 and 434 in FIGURE 7. The position of the ports 82 and 83 with full compressor discharge pressure is represented by the rectangles in dash outline at 436 and 437 in FIGURE 7. The position of the ports 82 and 83 in solid outline in FIGURE 7 corresponds to a minimum compressor discharge pressure. It will be observed that for a fixed minimum compressor discharge pressure, edge 440 of port 82 will move along imaginary line 441 with increasing power lever angle While edge 444 of port 83 will move along imaginary line 445. For a minimum compressor discharge pressure, as port 82 is moved along line 441, the area of registration between port 82 and slot 87 will progressively increase until leading edge 448 of port 82 reaches point 450 along the edge of slot 87 corresponding to a power lever angle somewhat less than 115. Further movement of port 82 along imaginary line 4411 will result in a decrease in the area of registration between port 82 and slot 87, which may be thought of as generally corresponding to the portion 420 of curve 410 in FIGURE 6. It will be understood that restricting the area of registration between port 82 and slot 87 will tend to reduce the pressure in annulus 90 which in turn will tend to reduce the flow of fuel to the core burner for a given compressor discharge pressure. Similarly, as port 83 is moved along imaginary line 445 for a minimum compressor discharge pressure, when valve member 225 is actuated to open ports 25411, for example at a power level angle just less than 115 as indicated by curve 411 in FIGURE 6, fuel will begin to flow to the annulus through the metering orifice defined by port 83 and slot 88. At this point leading edge 452 of port 83 will coincide with a point in the neighborhood of that indicated at 453 along the edge of slot 8 8 to provide a substantial area of registration between slot 8 8 and port 83 and accommodate a substantial increase in annulus fuel flow as the power lever is moved progressively in the neighborhood of 115. It will be observed that for any given angular setting of the power lever angle if compressor discharge pressure increases corresponding to a movement of the ports 82 and 33 to the left as indicated by the arrows 433 and 434, an increased area of registration between ports 82 and 83 and slots '87 and 88 will result providing an increased flow to the core and annulus burners. It will be appreciated that to vary the core fuel drop at the neighborhood of 115 as represented in FIGURE 6 at 420, the area restriction of slot 87 rep-resented by lines 460 and 461 could be varied, and in the limiting case, the slot edges could be represented by the dash lines 463 and 464 with no decrease in the area of registration beyond point 450, this condition corresponding to the curve 403-415416 in FIGURE 5.

Summary of Operation Assuming that the shaft 76 is initially in off position, as the pilot shifts the fuel supply demand lever to on position, cam portion 164a on shaft 76 raises pin 168 to disengage flange 1 68a from lever 122 to unlock lever 122 and allow opening of air valve 135.

As the power lever is moved between angles of 90 and approximately 114, the area of registration between port 82 and slot 87 progressively increases. The progressive increase in area of registration brings about a tendency for pressure in annulus 90 to increase which in turn tends to increase the pressure in chamber 103 and move diaphragm assembly 120 to the left tending to reduct the air pressure in chamber 131 and increase the air pressure in chamber 130 to open valve 135 and increase the supply of air to the turbine section 36 driving fuel pump section 35 Shown in FIGURES 2 and 3. This results in a pressure increase at fuel inlet 80 which is communicated to chamber 112 to balance the diaphragm assembly 120 in a new position corresponding to a new position of the valve 135. In this manner, increasing area of registration between port 82 and slot 87 results in a progressively increasing discharge pressure from the pump unit 35 and a progressively increasing 8 fuel flow to the core burner indicated at 22 in FIG- URE 1.

For any given setting of the fuel supply demand lever, an increase in compressor discharge pressure which is referenced to chamber 300, shifts valve body 84 to the left increasing the area of registration of port 82 with slot 87 and increasing the rate of flow of fuel to the core burner, generally in direct proportion to the increase in compressor discharge pressure.

When an angle of approximately 114 is reached as represented in FIGURE 6, cam shoulder 76c of shaft 76 moves out of engagement with valve member 225 to begin the supply of fuel to the annulu burner indicated at 23 in FIGURE 1. Specifically, opening of valve 225 references pressure in annulus 91 to chamber 233, tending to restrict orifice 243 and decrease pressure in chamber 246, allowing spring 257 to open ports 254a.

At this same power lever angle of approximately 114, the area of registration between port 82 and slot 87 may begin to rapidly decrease to cause a decrease in the area of registration corresponding to the curve portion 420 in FIGURE 6 and causing a corresponding drop in the supply of fuel to the core burner as the power demand lever is moved fro-m an angle of approximately 114 to an angle of approximately 116. As illustrated in FIG- URE 6, the drop in fuel flow to the core burner may exactly compensate for the increase in fuel flow to the annulus burner as represented by the curve 411 in FIG- URE 6, so that the sum of the core plus annulus fuel flow constitutes a smooth function of power lever angle over the regions from to 130. In fact, as represented in FIGURE 6, the total flow is a substantially linear function of power lever angles for angles between and This relatively smooth transition from flow to the core burner to flow to both the core and annulus burners prevents flooding or explosion in the afterburner section of the engine.

Adjustment of the screw means varies the bias of spring 121 on lever 122, and thus regulates the pressure difierential between chambers 112 and 103 which will be maintained by the system. Screw means 160 thus adjusts the pressure drop which will be maintained across the metering orifice defined by the registration between port 82 and slot 87.

Similarly, screw means 270 provides for adjustment of the bias of spring 271 to regulate the pressure drop across the metering orifice defined by the registration of port 83 and slot 88.

It may be noted that in FIGURE 4, valve 254 would normally be closed with valve member 225 in its flow restricting position shown in FIGURE 4, but has been shown open in order to illustrate the valve ports 254a more clearly. Also fuel inlet 80 and air outlet 46 are shown in FIGURE 4 for ease of comprehension of the control unit, although these ports are actually on the opposite side of the control unit from that viewed in FIGURE 4, as will be apparent from a consideration of FIGURES 2 and 3.

It will be apparent that many modifications and variations may be effected without departing from the scope of the novel concepts of the present invention.

I claim as my invention:

1. In a turbo jet engine including a compressor section and an afterburner section having core and annulus fuel discharge means, valve means having core and an nulus valve ports controlling flow of fuel to said core and annulus fuel discharge means respectively, said valve means being angularly movable to progressively open the core valve port in a first range of angular positions and to progressively open said annulus valve port in successive angular positions thereof beyond said first range of angular positions, said valve means being axially shiftable to alter the fuel flow rate to at least one of said core and annulus fuel discharge means, and means responsive to compressor discharge pressure for controlling the axial position of said valve means.

2. In combination, a unitary assembly comprising a turbine driven fuel pump having a fuel inlet, a fuel outlet, an air inlet and an air outlet, a control housing having an air inlet and an air outlet, a fuel inlet and a fuel outlet, means connecting said housing air outlet with said pump air inlet, means for connecting said pump fuel outlet with said housing fuel inlet, fuel valve means in said housing for controlling fuel flow between said housing fuel inlet and said housing fuel outlet, said fuel valve means having first and second outlet valve ports controlling flo-w of fuel therefrom, said fuel valve means being angularly movable to progressively open the first valve port in a first range of angular positions of the valve member and to progressively open the second valve port in successive angular positions thereof beyond said first range of angular positions, said valve means being shiftable axially to vary the area of at least one of said valve ports in predetermined angular positions of said valve means, air valve means in said housing for controlling air flow between said housing air inlet and said housing air outlet,

and means responsive to the differential in pressure between said control housing fuel inlet and said housing fuel outlet controlling said air valve means for maintaining a substantially constant fuel pressure drop between said housing fuel inlet and said housing fuel outlet.

References Cited in the file of this patent UNITED STATES PATENTS 2,447,423 Nies Aug. 17, 1948 2,674,847 Davies et al Apr. 13, 1954 2,688,842 Oestrich et al Sept. 14, 1954 2,724,239 Fox Nov. 22, 1955 2,739,442 Neal et al Mar. 27, 1956 2,742,755 Davies et al. Apr. 24, 1956 2,742,761 Mullen Apr. 24, 1956 2,770,945 Crim Nov. 20, 1956 2,774,215 Mock et a1 Dec. 18, 1956 2,807,138 Torell Sept. 24, 1957 2,830,436 Coar Apr. 15, 1958 2,836,957 Fox June 3, 1958 2,963,082 Binford et al Dec. 6, 1960

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