US2944597A - Fuel system - Google Patents

Description

July l2,` 1960 Filed Feb. 20, 1957 3 Sheets-Sheet l R. w. wlLsoN l 2,944,597

July 12, 1960 FUEL SYSTEM 5 Sheets-Sheet 2 Filed Feb. 20, 1957 liv/JA July 12, 1960 R. w. WILSON 2,944,597

FUEL SYSTEM United States Patent-O FUEL SYSTEM Robert W. Wilson, Euclid, Ohio, assignor to Thompson Ramo Wooldridge Inc., a corporation of Ohio Filed Feb. 20, 1957, Ser. No. 641,367

7 Claims. (Cl. 15S-36.4)

This invention relates to fuel systems and more particularly to ya combination pump of the type utilized in an aircraft fuel system wherein three separate pumping units are provided, one of the pumping units providing fuel rfor a main burner, another of the pumping units providing fuel for an `afterburner, andthe third pumping unit providing fuel for the afterburner at periods of peak demand. Y

This invention is primarily directed to a combination pump of the type having three separate pumping units including a main pump unit for the main burner, an afterburner pump unit which is continuously operative to supply fuel to the afterburner, and an auxiliary afterburner pump unit which may be selectively actuatedin response to demand pressure of the principal afterburner pumping unit. Demand pressure, as referred Yto herein, is the pressure of the fuel in the delivery line, which pressure is regulated in response to a control signal to satisfy demand for fuel yfor more or less power. For example, in systems Where a positive displacement pump is used, the fuel delivered to the burner may be controlled by a bypass valve, and as the by-pass valve is closed in response to a control signal, which manifests a demand for more fuel, the pressure increases. The vpressure increases with demand also in a system where a fuel pump is speeded up to satisfy a demand for power increase.

In particular, this invention involves the provision of a combination pump ofV the stated type in which a valve 'Patented July 12, 1960 z unit, the valve assembly is actuated to terminate the bypassing of the discharge from the auxiliary afterburner pumping unit to parallel this discharge with the discharge from the principal afterburner pumping unit. The valvel assembly includes a spool or pilot slidably mounted within a cylinder and biased in one direction by a spring. The spool or pilot is motivated by fuel discharged from the principal afterburner pumping unit in opposition to the force of the spring so that pressure is brought to bear upon another spool or pilot which is then moved axially within another cylinder to afford avjoinder of the discharges rfrom the several afterburner pumping units.

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

Figure l is a sectional elevational view, partly broken away, of a combination pump embodying the fuel system of the present invention;

Figure 2 is a greatly enlarged sectional diagrammatic view of a valve assembly forming a part of the combination pump of Figure l;

Figure 3 is a schematic showing of a fuel system illustrating a system of the type therein the principles of the invention may be utilized.

As shown on the drawings:

The pump forming a part of the fuel system of the present invention is indicated .generally by thereference numeral 10 and comprises a casing or housing 1l which includes a plurality of connected housing parts identified. on Figure l-by the reference numerals 12, 13, 14, l5 and The housing part indicated at 15 has an inlet i9 which may be connected to a suitable fluid supply conduit. The inlet '19 is in communicaiton with a volute pumping chamber 2i) in which is rotated a centrifugal impeller 2l. l

for increasing the pressure of the iluid to a predetermined level.

In the housing parts 12, 13 and 14 and 15 there are formed three longitudinally spaced pumping cavities for three separate gear pumping units indicated generally by the reference characters A, B and C, respectively.

Fuel maybe supplied by the pumping unit A to a main burner of an aircraftpropulsion engine utilizing` jet burners. The pumping unit B supplies fuel at all times to an afterburner forming apart of the environment of the present fuel system. 'The pumping unit C selectively supplies'fuel to the afterburner at periods fof system employing `a pump of the combination typ/e in which the output of the auxiliary afterburner pumping unit is selectively recirculated when not 'required for afterburner operation at a relatively lowy pressure, .substantially lower than the normal output pressure, so that the inevitable increase in temperatureof therfuel due to' working is minimized. f t

-V According to the present invention, the combination pump incorporates a flow transferring means in the pump casing for selectively parallelingthe outlet of the auxiliary afterburner pumping unit with the outlet of the principal afterburner, pumping unit.Y For Aexample,V the outlets of the principal afterburner pumping unit and the auxiliary afterburner pumping unit comprise a pair of longitudinally Yspaced openings selectively controllable by a valve assembly which permits continuous llow ofthe discharge from the principal afterburner pumping unit,Y

while normally bypassing the discharge from the auxiliary afterburner pumping unit back to interstage or inlet pressure. Upon a predetermined increase iii-pressure peak demand, Vsuch as at take-ofi or when accelerating. Each of the gear pumping units A, B,'and C are'substantially identical with respect to structural features, and, accordingly, common reference numerals will be used wherever possible. v J

Each gear pumping unit comprises a driven gear 34 meshing at an area of intermesh 36 with a driving gear 37. Extending axially outwardly from the hub portion 'of each'respective driving and driven gear is a first shaft extension 38 and a second shaft extension 39. EachV shaft-extension 33 is journalled by a stationary bushing member 40 received in a corresponding housing bore and Vhaving a flange 41 providing a sealing face for engaging and sealing against the adjoining side face of the Y 'of the discharge from the principal'.afterburnerpumping f gear.y Y

Each gear shaftr extension39 is journalled in the casingby a movable pressure-loaded bushing 42 having a ilange V43 providing a front face 44 for engaging and sealing against an adjoining gear side face and a rear faceV 46 which togetherl with means includingthe housing,

11 forms a pressure control chamber 47v communicating with pump-generated discharge pressure to pressure load The housing part 12 is closed by a cover member 4S assembled in lfirm assembly to the housing part 12 by a plurality of fasteners 49. A shaft driving member Si) has a splined portion 51 adapted to be connected to a prime mover on the outside of the pump and extends inwardly into the housing part 12 for connection to the gear pumping units A, B and C. The driving member 50 has a collar portion 52 splined to a quill shaft 53 which extends through hollow portions of the driving gears 37 of the gear pumping units A and B. The quill shaft 53 is in turn splined to the driving gear of the gear pumping unit C and also to a second quill shaft member 54 which extends through the gear pumping unit C and has attached thereto at one end a gear S6 forming part of a gear train 57 which is operative to drive the centrifugal impeller 21. Thus, the gears of the gear pumping units A, B and C are rotated at a speed corresponding to a rated eiciency speed for intermeshing gears and the centrifugal impeller 21 is rotated at a much higher speed corresponding to the speed for greatest rated `eciency of centrifugal impellers. The housing part 16 forms a cover for the gear train 57 and may be fastened to the housing part by a plurality of fasteners indicated at 58.

The shaft extensions and the hubs of the driving gears 37 are hollow and the shaft extensions 38 and 39 as well as the hub portions of the driven gears 34 are also hol.- 10W, thereby proving through passages the length of the pump housing 11. Thus, all of the internal cavities such as the cavity 59 in the pump housing 11, which are sepa*- rated from the actual outlet portions of the pump can be communicated with a` source of low pressure such as the pump inlet to facilitate the use of low pressure seals for minimization of leakage and other sealing problems.

Moreover, this arrangement affords another advantageous structural and functional feature which permits the flooding and lubrication of a thrust bearing associated with the driving means just described. In reference to this arrangement, it should be noted on Figure l that the driving member 50 has a radially outwardly extending annular ange 60 having at one side thereof a chamfered bearing face 61 engaging a ring of bearing material 62 seating in an annular recess 63 formed in the cover member 48. A coil spring 64 is located in a recess jointly provided by the driving member 50 and the quill shaft 53 so that one end of the coil spring 64 is bottomed against the driving member 50 and the opposite end is bottomed against the quill shaft 53, thereby maintaining a continuous biasing force between the two parts.

The driving member 50 is provided with an axially extendingannular lip 66 and the cover member 48 is provided with an additional recess 67 in which is mounted a sealing assembly 63, the sealing assembly 68 engaging against the lip 66 and effecting an adequate seal between the cover member 48 and the driving member 50. Since the sealing assembly 63 is located outside of the thrust bearing formed by the flange 6% and the bearing 61, the thrust bearing can be flooded with the fluid contained Within the cavity 59 to insure adequate lubrication and cooling even though the pump is operated at high speeds.

Referring now more particularly to Figure 2 in conjunction with Figure l, each of the pump units A, B and C has a separate outlet formed by cored areas or recesses Within the housing parts 13 and 14. The outlet of the pumping unit A provides fuel to the main burner in the conventional manner and need not be discussed in detail. The outlets of the pump units B and C are shown somewhat diagrammatically in 1Figure 2 and are indicated by reference numerals 71 and 72respectively.

As illustrated in Figure 3, the pump A is `connected to discharge to a delivery line 75 which is connected toa main burner nozzle 77. The quantity of fuel delivered from the pump may be controlled such as by the provision of a by-pass line 79 leading from the discharge line '75 to a pump intake line 85. The quantity of ow ing of a valve 81 which is operated by a control 83.

The output or discharge of pump B is connected to the line 71 which connects to the valve assembly Si), as also illustrated in Figure 2. The output conduit 1122 from the valve assembly 80 connects to an afterburner nozzle 95. During periods of low fuel consumption of the nozzle 95, the delivery of fuel from the pump B is controlled through a lay-pass line 87 which connects to the conduit 122 and connects to the pump intake 89. Flow through this bypass line is controlled by a by-pass valve 91 operated by a control 93. With this arrangement, as the demand for fuel increases, the control 93 closes the valve 91, and a resulting increase in the discharge pressure of the pump B results.

The pump C has its discharge connected to the line 72 which connects to the valve assembly 80. The by-pass return line 100 connects to apump intake line 97.

According to the present invention, the outlets 71 and 72 are in communication with the valve assembly Si? which is operated to afford continual flow from the pumping unit B and recirculation of the discharge from the outlet 72 of the pumping unit C at predetermined discharge pressures of the pumping unit B. In addition, the valve assembly 80 is operative to effect joinderof the discharges from the pumping units B and C at certain demand pressures of the pumping unit B. To this end, the valve assembly 80 is provided with av cylindrical bore $2 in which is slidably mounted a valve spool or pilot 84 having spaced control portions 86, 88 and 90. The valve spool or pilot S4 is normally retained inthe position shown in Figure 2 by a compression spring 92 which is opposed by fluid received within the bore 82 at the right side of the control portion 90 from theV outlet 71 by any suitable means such as a cored passage 73 or the like. In this position of the valve spool 84, fuel discharged from the pumping unit C is free to flow radially through the bore 82 and out a port 94 formed in the valve assembly casing in register with the outlet 72, through a longitudinally extending passage 96 and thence back to the inlet of the pumping unit C through a port 98 and a registering port 100, a passage being formed through the bore 82 by the left side of the controlportion 86 and a disk 102 against which the compression springy 92 abuts.

The valve assembly 80 has another cylindrical bore 104 in which is slidablymounted a valve spool or pilot 106 having control portions 108v and 110 maintained in spaced relation on a central shaft `112. YThe spool l106 is normally maintained in the position shown by a compression spring 114 which abuts against a disk 116 mounted at one end of the shaft 112 and is opposed by the relatively low pressure of the fluid discharged from I the pumping unit C when the spool 84 is in the position shown. In theposition shown, discharge from the pumping unit B may at all times flow across the bore S2, through a passage 118 and thence into the passage' 120 which is in register with a passage 122Y at the opposite side of the bore 104. Thus, fuel is supplied to the afterburner through the passage 122 at all times.

When the demandV pressure of the pumping unit B increases, the fuel at the right side of the control portion urges the valve spool 84 to the left, as viewed in Figure 2, thus compressing the spring 92 and closing off the port 98 so that the pressure of the lluid discharged from the pumping unit C is increased and exerts a pressure against the control portion 10S of the spool 106 against the force of the compression spring 1=14 so that the spool 106 is moved to the right. Thus, aV port 124 which is in communication with the passage 96 may clischarge fluid across the borer104, into a registering passage 126 and then through a longitudinally extending passage 128 to the discharge passage 122.

The control portion 90 of the spool 84 is dimensioned to aiford suflicient movement of the spool to effect closing of the port 98 by the control portion v86. An addi;

' permits the control uid on the rightrside thereof to discharge through the passage 120.

'from said rstipump therethrough, a second bore having longitudinally spaced iports forY selective communicavBy the above-described inventiommeans are provided for recirculating the discharge of one pumping unit of .a-

vcombination pump at relatively low pressure. By this arrangement, excessive heating and effervescing of the recirculated fuel are effectively precluded. In the present instance, the pumping unit C is activated in'response to peak demand pressure of the pumping unit B so that additional .fuelrisprovided to the afterburner during periods of peak requirement such as at takeoff Vor acceleration. In the present instance also, the Yrecirculation control is located within the pumpso that the distance which the recirculated fuel is pumped is minimized.

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

I claim as my invention:

l. In combination, a firstl pump operable to discharge fuel to a burner of a reaction engine, a second pump for selectively supplying fuel to the burner in response to the discharge pressure of said first pump, and `means for activating said second pump at periods of peak fiow demand manifested by said discharge pressure of said first pump, said means comprising a valve assembly having a rst bore, a valve spool slidably mounted therein and having longitudinally spaced control portions, a second bore communicating with said first bore, a valve spool slidably mounted in said second bore, said secondnamed valve spool having a plurality of longitudinally spaced control portions, said second-named valve spoolY being normally positioned to afford recirculation of the discharge from said second pump at relatively low pressure, said second-named valve spool being movable arially in response to an increase in pressure of the discharge from said first pump to a predetermined level to ter- 2. In a fuel system for reaction engines and the like,

in combination, a first pump for supplying fuel toa burner, a second pump for selectively supplying fuel to the burner, and means operative in response to the pres; sure of the discharge from said first pump for activating said second pump during periods of peak fuel flow requirements, said means comprising a valve assembly having a first bore, ay valve spool slidably mounted'therein and having longitudinally spaced control portions, a second bore communicating with said first bore, a valve spool slidably mounted in said second bore, said second-named valve spool having a plurality of longitudinally spaced control portions, said second named valve spool being normally positioned to afford recirculation of the discharge from said second pump at relatively low pressure, said second-named valve spool being movable axially in response to an increase in pressure of the discharge from said first pump to a predetermined level to terminate the recirculation of the discharge from' said second pump,-

said first-named valve spool being movable axially in response to an increase-in pressure of the discharge from said second pump to a predetermined value to interconnect the discharge of said second pump and the discharge of said rst pump to .afford an increased fuel supply to said burner.

3. In a fuel system for reaction engines and the like having first and second pumps and including a valve assembly integral with said pumps and having a first bore, a valve spool slidably mounted in said bore and having a plurality of longitudinally spaced control portions normally positioned to afford free passage of the discharge 75 output of said second pump and to the output of said tion With said first bore a'bypassV communicating with the Ysecond bore for recirculating `the discharge from' said second. pump back' to the inletv thereof, avalve spool slidably mounted in said second bore and having longitudinally spacedy control portions normally affording free passage therethrough ofthe discharge from` said first pump while preventing the freepassage therethrough of the discharge from said vsecond pump,V said second- Ynamedspool being movable axially in responseto an increase in pressure of the discharge Vfrom said first pump to a predeterminedjlevel to terminate the recirculation of the discharge from said second pump, saidrrst-named valve spool being lmovable axially in response to anrincrease in pressure of the discharge from saidsecond pump to a predetermined ,value to interconnect the disl charge ofsaidsecond pump. and the discharge of `said first pump to afford anincreased fuel supply. Y

- y 4. In av fuelisystemfor reaction engines and the like .having a combination pump including a first pump operable to discharge fuel to a burner of the reaction engine, a second pump for selectively supplying fuel to the burner in response to the discharge pressure of said first pump,

and means for activating said second pump at periods of peak demand, s aid means comprising a valve assembly Ihaving a first bore, a valve spool slidably mounted therein and having longitudinally spaced control portions, al ysecond bore communicating with said first bore, a valve spool slidably mounted in said second bore, said secondnamed valve spool having a plurality of longitudinally spaced control portions, said second-named valve spool being normally positioned to afford recirculation of the discharge from said second pump at a pressure substantially lower than the normal output pressure thereof, said second-named valve spool being movable axially in response to an increase in pressure of the discharge from said first pump to a predetermined level to terminate the recirculation ofthe discharge from said second pump, said first-named valve spool-being movable axially in response to a predetermined increase in pressure of the discharge from said second pump to interconnect the discharge of said second pump and the discharge of said first pump to afford an increased fuel supply to the burner.

5. In a fuel system where4 the delivery pressure increases with demand, a fuel mechanism comprisingrin combination, a first pump for supplying fuel under pressure to the system, a fuel delivery line connected to the output from said first pump for delivering fuel, a second pump for selectively supplying fuel under pressure to the system, said second pump normally inoperative to deliver fuel under pressure, and pressure responsive pump. actuating means connected to said fuel delivery line and to said second pump and operative in response to the discharge pressure from said i'lrst pump to activate said l second pump upon a predetermined rise in pressure of said discharge during periods of peak fuel ow requirement to cause the second pump to deliver fuel under pressure-to the system so that a'saving in power for oper;

' ating said pumps is effected during periods when said secv ond pump is inoperative.

l said second pump upon a predetermined rise in pressure of said discharge during periods of peak demand, said means comprising a valve assembly connected to the ffrstlpump-fand operative inifone=position tofby-pass the discharge -from-fsaid secondnpump andshifting inv respouse to saidfpredeterminederise in pressure of the dis- :charge of .theifrst pump toaifsec'ond position to'sc'onnect 'the output' ofth'eifrst Vpump to the output ofvrthe sec.;l 0nd, pump.

7. Inrafuelsystenl wheredelivery pressure increases with demand, -a fuel delivery-mechanism comprising in combination, "a lfirst pump for supplying fuel under-pressure, a Erst fuel delivery-line 'connected to thewoutput from-said rst purnpand connected to the system for delivering fuel, `-asecond pumpfor selectively supplying fuel under'pressure, `a second" fuel delivery line connected between `the output of said second pump andsaid rst fuelidelivery line so that 'said-first and second pumps can both deliverrfuel to thewsystem, a by-pass line connected tosaid second fuel delivery line for lay-passing the fueldelivered from said-,second-pump, a by-pass valve in said by-pass 1ine,'pressure `responsive valve operating `meansconnected to said by-pass lvalve actuated by discharge A,pressure ofthe .rstpump toclose'fsaidbwpass `valve upon` a precleterrrlined,` rise in "fuekpressure inlsaid rst fuel delivery linie, .a separatingfvalve in saidfsecond fueldelivery line between said by-passline and? said rst fuel delivery line stopping fuel' flow from saidrst 'delivery line to said by-pass line, and valveoperatingameans connected to` said separating valve'and operative 4toclose said separating valve when said` lay-passV .valve is yopen and to open said separating valve when said by-pass valve is closed.

References Cited in the le of this patent UNITED STATES PATENTS 1,049,894 Merrill Ian. 7, 1913 2,545,856 Orr Mar. 20, 1951 2,549,897 Evrell Apr. 24, 1951 2,582,753 Herbelleau Jan.l 15,V 1952 2,617,361 Neal Y Nov. 1-1', 1952 2,636,553 Ballantyne et al ApnV 28,Y 1953 2,835,323 Booth a May 20, 1958

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