US3118491A

US3118491A - Liquid pumping apparatus

Info

Publication number: US3118491A
Application number: US75593A
Authority: US
Inventors: Ernest D Simons; Stanley R Tyler
Original assignee: Dowty Fuel Systems Ltd
Current assignee: Dowty Fuel Systems Ltd
Priority date: 1959-12-15
Filing date: 1960-12-13
Publication date: 1964-01-21
Anticipated expiration: 1981-01-21

Description

21, 1964 E. D. SIMONS ETAL 3,118,491

I LIQUID PUMPING APPARATUS Filed Dec. 13, 1960 4 Sheets-Sheet 1 FIG].

J 1964 E. D. SIMONS ETAL LIQUID PUMPING APPARATUS 4 Sheets-Sheet 2 Filed Dec. 13, 1960 1964 E. D. slMoNs ETAL LIQUID PUMPING APPARATUS 4 Sheets-Sheet 3 Filed Dec. 15, 1960 H54 7 Exam/vat? .2

ME 7' E RING com/701.

Jan. 21, 1964 E. D. SIMONS ETAL LIQUID PUMPING APPARATUS 4 Sheets-Sheet 4 Filed Dec. 13, 1960 a2 s4 s5 67 a: 6/ 59// $3 42 A Inn/9 United States Patent 3,118,491 LIQUID PUMPING APPARATUS Ernest D. Simons and Stanley R. Tyler, (Iheltenham, England, assignors to Dowty Fuel System Limited, Cheltenham, England, a British company Filed Dec. 13, 1960, Ser. No. 75,593 Claims priority, application Great Britain Dec. 15, 1959 3 Claims. ((31. 158-365) This invention relates to pumping apparatus. The object of the present invention is to provide a pumping apparatus capable of the delivery of liquid at widely varying pressures and flow rates to a hydraulic load. An example of pumping apparatus to which the invention may be applied is the pumping apparatus used on an aircraft to supply the burner nozzles of a gas turbine engine.

In accordance with the present invention a liquid pumping apparatus for delivery of liquid at widely varying pressures and flow rates to a hydraulic load comprises a main pumping and metering unit capable of pumping any desired flow rate of liquid within a lower pressure range, an auxiliary pump of the centrifugal type, and valve means operative by a pressure in the hydraulic load or by the pressure in the output of the main unit to connect the main unit output either directly to the load at lower pressures or to pass it through the centrifugal pump to the load if higher pressures become necessary. Where the load takes the form of spill spray nozzles which require a high pressure supply flow and a lower pressure zone to which spill flow may return, the auxiliary centrifugal pump may be connected to the spill burners to receive the spill flow and to pump it at a higher pressure for supply to the spill nozzles. For this purpose the auxiliary centrifugal pump may be provided with an auxiliary port giving access to the pump impeller at a position radially between the central inlet and the peripheral outlet, the supply to the spill nozzles then coming from the peripheral outlet and the spill return entering the impeller at the auxiliary port. The output of the main unit is then preferably connectable by the valve means alternatively to the centrifugal pump inlet or to the auxiliary port depending on whether a higher or lower range of pressures are required in the supply pipe to the nozzles. The main unit may comprise a variable positive displacement pump having metering means to control displacement to give the required rate of liquid flow. Alternatively, the main unit may comprise a fixed positive displacement pump having a by-pass valve adjustable by flow metering means to give the required rate of flow. Again the main unit may comprise a centrifugal pump having a variable restrictor controlled by the metering means in series with its inlet or outlet ports. The auxiliary centrifugal pump may be arranged for operation over part or the whole of its range as a vapour core pump in which the liquid forms an annulus within the pump casing whose radial depth determines the pressure at the output and at the auxiliary port if provided. The valve means may comprise a simple changeover valve to connect the output of the main unit alternatively to the input or output of the auxiliary centrifugal pump in accordance with pressure at the output from the auxiliary pump which directly feeds the load. Alternatively, the valve means may operate to disconnect all ports of the auxiliary pump and to connect the main unit directly to the load in the lower pressure range, the valve also acting in this condition to connect the output of the auxiliary pump to a low pressure zone so that the pump may empty and thus take substantially no power to drive the rotor. Again, alternatively, the valve means may comprise a pressure sensitive valve to connect the main unit output to the input of the auxiliary centrifugal pump when the pressure of the main output exceeds its predetermined value, a non-return valve being provided 3,113,491 Patented Jan. 21, 1984 to connect the main unit output With the auxiliary centrifugal output whereby the main unit output may feed the load directly until the pressure switches the main output to the input of the auxiliary centrifugal pump, the non-return valve then closing automatically because of the higher pressure developed at the output of the auxiliary pump over and above the pressure of the output of the main unit.

Various examples of the invention will now be described With reference to the accompanying drawings in which:

FIGURES 1, 2 and 3 are diagrammatic representations of three separate examples particularly illustrating the valve means;

FIGURE 4 is a more detailed diagrammatic representation of the main pumping unit usable in any of the examples of FIGURES 1 to 3; and

FIGURE 5 is a detailed diagrammatic representation of an alternative pump for use in the main pump unit of FIGURE 4.

Reference is made initially to FIGURE 1. Hydraulic liquid is supplied from a tank 1 to a supply pump 2 which may be of the variable positive displacement type or the fixed positive displacement type. Output from the supply pump 2 passes to a metering control 3 which measures the flow rate of liquid from the supply pump 2 and acts to control the output as described with reference to FIG- URE 4 or FIGURE 5 to ensure that a desired flow rate is delivered. The supply pump 2 is capable of generating a reasonable pressure, but where a large total pressure range of hydraulic liquid is required it may not be possible to rely on a single positive displacement pump to supply liquid at the higher pressures. Alternatively, the drive for the supply pump 2 may be of a limited power capacity which will prevent the obtaining of higher pressures. The supply pump 2 and the metering control 3 together form the main unit which supplies liquid at a selected flow rate but only up to a medium pressure level. The output from the main unit passes through pipe 4 to a piston valve 5 comprising a cylinder 6 within which a spool valve 7 is slidable. The pipe 4 opens at a port 8 in the cylinder 6 at a position where liquid flow is controlled by the land 9, so that in the uppermost position of the spool valve against an upper stop 11 a connection is provided from port 8 to a port 12 leading to the inlet of the auxiliary pump 13, whilst in the lower position of the valve 7 against the lower stop 14, the output of port 8 may flow into the port 15 from which pipe 16 extends to the hydraulic load. The upper land 17 of the valve 7 in the uppermost position connects a port 18 carrying output from the pump 13 to the port 15. The land 17 in its lower most position cuts off the flow passage between ports 18 and 15 and opens a flow passage from the port 18 to a port 19 which carries liquid to a low pressure zone at the inlet to supply pump 2. The lower land 21 of the spool valve 7 isolates the lower end of the cylinder 5 which is connected by a pipe 22 to the output pipe 16 so that the pressure in the output pipe 16 may act over the lower surface of the land 21. The force exerted on the piston valve 7 is opposed by the compression of a spring 23 located at the upper end of the piston valve 7. The spring 23 is a low rate highly compressed spring so as to allow movement of the piston valve 7 from one stop to the other when the pressure in the pipe 16 is above or below a predetermined pressure. The auxiliary pump 13 comprises a suitably shaped chamber 24 within which a centrifugal pump rotor 25 is rotat ably mounted for drive by a shaft 26.

The apparatus as described in FIGURE 1 may be used for the supply of fuel to a gas turbine engine, the pipes 16 supplying burner nozzles of a simplex type. The metering control 3 is adjustable to select any desired flow and usually, although not necessarily, the desired flow rate will determine the pressure that must exist in the output pipe 16 necessary to cause the desired flow rate to pass through the load. If the pressure required in the pipe 16 is low, i.e. below the predetermined pressure, the piston valve 7 will be in its lower position against stop 14 under the action of spring 23 and the output of the main unit through the pipe 4 will then enter by port 8 into the space between lands 9 and 17 and leave through the output pipe 16. In this position of the valve the inlet 12 to the centrifugal pump 13 will be closed and the outlet 18 of the centrifugal pump will be connected through port 19 back to the inlet of the supply pump 2. In this way the pump 13 will be empty, and although the rotor is driven very little power will be consumed. When the pressure exceeds the predetermined value in the output pipe 16 the piston valve 7 will move upwardly against the load of spring 23 to cause port 8 to be connected to port 12 and port 18 to port 15. Thus, the output liquid from the main unit will enter the auxiliary pump 13 and be delivered from this pump through ports 18 and to the output pipe 16. The liquid within the pump 13 will assume an annular form within the pump casing 24 whose radial depth will determine the pressure existing within the output pipe 16. The pressure in the pipe 4 will drop to a low value approximating to the vapor pressure of the liquid being pumped. The pump 13 is, of course, of such size and driven at such a speed that it is fully capable of supplying the maximum liquid fiow rate at the maximum pressure desired from the whole apparatus.

Reference is now made to FIGURE 2 of the accompanying drawings where possible similar reference numerals will be used. This example is particularly intended for the supply of fuel to spill spray nozzles in the combustion chambers of an aircraft gas turbine engine. Fuel is contained within a tank 1 and is normally drawn from the tank by a supply pump 2 of the positive displacement type and then fed through a metering control 3 which may act as ascribed with reference to either FIGURE 4 or FIGURE 5. After passing the metering control 3 the fuel is at medium pressure and is then passed through a heat exchanger 27 for the cooling of liquids used in the aircraft which might reach an undesirable high temperature for example engine lubricating oil. Again the supply pump 2 and the metering control 3 forms the main unit and the output is fed to pipe The auxiliary centrifugal pump 13 comprises a rotor 25 rotatable by shaft 26 within a chamber 24. The rotor 25 is of the unshrouded type and at a position in the casing between the peripheral outlet port 28 and the inlet port 29, an auxiliary port 31 is provided which ovens on to the vanes of the impeller 25. A piston valve 5 is provided comprising a piston valve member 7 siidably mounted within a cylinder 6, the pipe 4 opening to a port 8 in the wall of the cylinder 6. There is, however, some difference from the previous example in the construction of the valve 5. The valve member 7 comprises a pair of

spaced lands

32 and 33 of which the lower land 32 is sufficiently large to close the passage between the port 8 and the port 12 which leads to the inlet of the pump 13. The upper end of the cylinder 6 is connected to the port 31 whilst at the lower end of the cylinder 6 a spring 23 is provided which urges the valve member 7 upwardly. The lower end of the cylinder 6 is connected by a pipe 22 to the inlet of the pump 2. The port 3 1 in the pump casing communicates by a pipe 34 with the spill connections of a plurality of spill spray nozzles of which one is diagrammatically indicated at 3-3. The output port 28 of the auxiliary centrifugal pump communicates with a pipe 35 which feeds the main supply connection of the spill spray nozzles. A non-return valve 36 interconnects the spill passage 34 with the output pipe 4 from the main unit.

In normal operation of the example in FIGURE 2 at low rates of flow the metered output of the main unit passing through pipe 4 will pass directly through nonreturn valve 36 into the spill passage 34. In this pa sage fuel will fiow to the auxiliary port 31 of the pump 13 and will be centrifuged to the output port 28 whence it will flow at a higher pressure through the pipe 35 to the spill nozzle 30. The liquid within the pump chamber 24 may either completely fill the space in which the impeller rotates or, alternatively, if sufficient pressure may be given to the liquid by the rotor a liquid annulus may be formed within the chamber having a vapour core, radial depth of the annulus giving pressures at the

ports

28 and 31 suitable for the supply and

spill passages

35 and 34 of the spill nozzles. As the fuel flow rate is increased by the action of the metering control 3 pressures in the system will rise and in particular pressure in port 31, which acts on the upper end of valve member 7 will urge this latter against the spring 23 to open the port 8 to the port 12 to allow flow from the pipe 4 to the inlet 29 of the centrifugal pump 13. The pressure rise developed in the centrifugal pump between the inlet port 29 and the auxiliary port 31 will thus be added to the pressure in the pipe 4 with the result that the non-return valve 36 will close and liquid at higher pressures will then pass through the

pipes

34 and 35. Depending on the opening allowed between the

ports

8 and 12 by the valve member 7 the pressure in the pipe 4 is controlled in a predetermined manner such that it does not drop to a particularly low value, but at the same time it is considerably l0\ 'er than the maximum pressure that may be developed by the pump 2. The auxiliary centrifugal pump may operate either completely full of liquid or, alternatively, with a vapour core. In this latter case the pressure at the end of the inlet port 29 will be substantially zero and any pressure generated by the supply pump 2 for feeding to pipe 4 will be lost as pressure drop between

ports

8 and 12 of valve 5. Thus, the pump 13 will supply the entire operating pres sure for the spill spray nozzles.

Reference is now made to FIGURE 3 of the accompanying drawings and again similar references will be used as in the previous two figures where possible. The difference in the arrangements of FIGURE 3 from the arrangement of FIGURE 2 lies in the construction of the valve 5. A piston valve member is no longer used but it is replaced by a simple piston 37 having a hollow interior constantly in communication with the port 8 and a graduated aperture 38 for co-operation with port 12, so that a graduated restriction of fuel flow from port 8 to port 12 is obtained with movement of the iston member 37, against the spring 23, which is in this instance a low rate a highly compressed spring. The pressure acting on the piston to urge it against the spring 23 is the pressure existing in pipe 4. The auxiliary centrifugal pump 13 is arranged to operate as a vapour core pump or as a fully primed centrifugal pump depending on operating conditions. Other than for the changes effective to the valve 5 the arrangement of FIGURE 3 corresponds with the arrangement of FIGURE 2.

In operation at low flow rates and pressures the output from the main unit passes from pipe 4 through non return valve 36 into the spill h w line 34 in which fuel flows back from the spray nozzles to the auxiliary port 31 in the centrifugal pump. The rising pressure between port 31 and port 28 gives the necessary pressure increase between the

passages

34 and 35. In this lower flow rate stage liquid from port 31 will enter the chamber 24 which will give a vapour core so that the radial depth of liquid from the core to the port 31 balances the pressure existing in the delivery pipe 4 from the main unit. As higher rates of flow and higher pressures are selected the output pressure in pipe 4 acts on the piston 37 to urge it down against spring 23 to open the restricted flow path thus increasing the radial depth of liquid inwardly at port 31 to increase the pressure in pipes 34 and to a value of that existing in the pipe 4. In

Reference is now made to FIGURE 4 of the accom-.

panying drawings, which illustrates one form of metering control 3 and its control of the supply pump 2'. In this control the supply pump is assumed to be of the variable displacement kind and displacement is controlled by an angularly movable lever 41. The lever is moved by a servo motor 42 comprising a cylinder 43 and a piston 44, sliding therein from which a piston rod .5 extends for pivotal connection to a lever 41. A spring 46 acts on the piston 44 to urge it to the position representing minimum displacement to the pump 2. A pipe 47 carries liquid under pressure as delivered by pump 2 to pipe 48, and it passes through a restrictor 49 to the right hand end of cylinder 43. From cylinder 43 a pipe 51 extends into the metering control 3. Within the metering control 3 a passage 43 extends to an adjustable throttle 52, and fuel having flowed past this throttle enters the output pipe 4 from the metering control. The throttle 52 is adjusted by rack and

pinion

53 and 54 which in turn are adjusted by an external lever 55. The pressure drop occurring at the throttle 52 is fed by means of pipes 56 and 5'7 to pressure

pads

53 and 59, which are joined together by a rod 61. The resultant force exerted on rod 61 is transferred by a pin 62 to one end of a lever 63 mounted within a chamber 64 in the control 3. The force exerted on the lever by the pin 62 is opposed by a compression spring 65 acting oppositely on the lever about its fulcrum 66. The lever controls escape of fuel from a vent 67 formed at the end of the pipe 51. Fuel entering chamber 64 from vent 67 escapes to a low pressure zone through a pipe 70.

In operation the fuel escaping from vent 67 will have passed through the restrictor 49 and thus the pressure acting on piston 44 to urge it against spring 46 will be determined by the escape flow permitted from vent 67. A very small movement of the lever 63 will make considerable variations in the escape flow from vent 67 and thus is capable of movement of piston 44. At a position of balance where the escape from the vent 67 determines a pressure in the cylinder 43 its balance is a spring 46, it can be seen that it is necessary for the spring 65 to balance exactly against the load exerted by the

opposed pressure pads

58 and 59. It is therefore clear that the spring 65 will act to control movement of lever 63 to adjust the displacement of the pump 2 so that the flow rate through the throttle 52 causes a certain pressure drop at the throttle 52 to occur. If the throttle 52 is adjusted by lever 55 a control as described will adjust the flow rate to retain the same pressure drop at the throttle 52. It will be clear that the metering control as described will enable any predetermined flow rate to be accurately maintained.

Reference is now made to FIGURE 5 which discloses an alternative arrangement for the supply pump 2" to that disclosed in FIGURE 4. In this arrangement the pump 2" is of fixed positive displacement and a by-pass valve 68 is provided to adjustably by-pass fuel from the delivery of the pump in order to determine a flow rate at the output passage 4. The by-pass valve comprises a bypass valve member 69 capable of axial movement to adjust the throttle flow passage between two

ports

71 and 72 in the valve 68. Port 71 is connected to the delivery passage 48 of the pump 2 whilst port 72 is connected to the inlet passage to the pump 2". Piston valve 69 is adjusted by a servo piston 73 carried within servo cylinder 74. Pressure liquid from the delivery of the pump 2" is carried through pipe 75 to the lower end of cylinder 74 and through a restrictor '76 to the upper end of cylinder 7%. Pipe 51 extends from the upper end of cylinder 74 to the vent 67 in the metering control 3. The escape of liquid from the vent 67 determines a pressure drop in restrictor 76 which enables a force balance to be obtained between the higher pressure acting over the lower smaller area piston 73 and the reduced pressure acting over the upper full area of this piston. For a position of balance a particular position of the lever 63 in the metering control 3 is necessary, which will then determine an opening of the piston valve member 69 and of the by-pass flow rate from the delivery of the pump 2", the remainder of the delivery then forming the controlled output through the pipe 4.

The main pumping and metering unit may be formed by Way of example as shown in either FIGURE 4 or FEGURE 5, and either of these arrangements may be included in the examples of the invention described with reference to FIGURES l, 2 or 3.

We claim as our invention:

1. In combination with a hydraulic load, a main pumping and metering unit including a positive displacement pump and drive means therefor, which unit is alone only capable of pumping at required flow rates up to a predetermined high load pressure, an auxiliary pump of the centrifugal type which is capable of pumping at said required flow rates against load pressures in excess of said high load pressure, means defining two flow paths between the main pumping and metering unit and the load, at least one of which passes through the centrifugal pump, and valve means operative to route the main unit flow through the other of the flow paths so long as the pressure applied by the unit remains below said high load pressure and to divert flow through said one flow path when the pressure exceeds said high load pressure.

2. The combination according to claim 1 wherein the centrifugal pump is equipped with a peripheral outlet having a connection with the load, and with a pair of inlets having a connection with the main pumping and metering unit, one of which inlets is positioned centrally of the centrifugal pump and the other of which is positioned relatively radially intermediate the outlet and said one inlet thereof; and wherein the valve means is opera tive to route the main unit fiow through the other of the centrifugal pump inlets so long as the pressure applied by the inlet thereof when the pressure exceeds said high load unit remains below said high load pressure and to divert flow through said one pressure.

3. The combination according to claim 2. wherein the hydraulic load includes a spill spray nozzle the inlet of which is connected with the outlet of the centrifugal pump, and the spill return of which is connected with the other of said inlets in the centrifugal pump.

References (Jited in the file of this patent UNITED STATES PATENTS 868,718 Smith Oct. 22, 1907 1,049,894 Merrill Jan. 7, 1913 2,720,256 Pearson Oct. 11, 1955 2,916,875 Morley et a1 Dec. 15, 1959 3,026,929 Burns Mar. 27, 1962 FOREIGN PATENTS 750,909 Great Britain June 20, 1956 1,184,654 France Feb. 9, 1959 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION :Patent No., 3,, ll8 49l January 21, 1964 Ernest DO Simons et al,

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 6 line 5O beginning with "the inlet thereof" strike out all to and including "said one pressureo" in line 52 same column 6, and insert instead the unit remains below said high load pressure and to divert flow through said one inlet thereof when the pressure exceeds said high load pressure Signed and sealed this 16th day of June 1964- (SEAL) Attest:

EDWARD J. BRENNER Commissioner of Patents ERNEST W. SWIDER Attesting Officer