Variable speed centrifugal pump

• US 4,332,527 A
• Filed: 08/10/1979
• Issued: 06/01/1982
• Est. Priority Date: 08/10/1979
• Status: Expired due to Term

• Current Assignee: BFM Romec Corp.
• Original Assignee: Lear Siegler, Inc. (LSS Holdings LLC)
• Inventors: Moldovan, Richard J., Davis, Harold D.
• Primary Examiner(s): Croyle, Carlton R.
• Assistant Examiner(s): LOOK, EDWARD K
• Application Number:
  US06/065,527
• Time in Patent Office: 1,026 Days
• Field of Search: 415/18, 415/122 R, 417/15, 417/84, 417/85, 417/87, 417/89, 417/79, 417/80, 417/18, 417/20, 417/22, 417/24, 417/212, 417/213
• US Class Current: 415/15
• CPC Class Codes: F02C 7/236 Fuel delivery systems comprising two or more pumps
• CPC Class Codes: F02C 9/30 characterised by variable fuel pump output
• CPC Class Codes: F04C 14/02 specially adapted for several machines or pumps connected in series or in parallel

Abstract

A variable speed centrifugal pump for aircraft fuel systems and the like having the capability of matching fuel flow and pressure to engine requirements throughout a variable flight profile without in-line flow controls and metering devices comprising a unique combination of centrifugal impeller stage and positive displacement pump device which controllingly, drivingly, fluidly couples the impeller to the aircraft engine drive. The positive displacement pump device includes rotating hydraulic displacing input and output members, the latter being driven by the former at a relative speed normally responsive to discharge flow rate of the positive displacement pump device which is controlled to regulate impeller speed for matching pump flow and pressure to engine requirements. The positive displacement pump may employ fuel as the pumping media in which event the discharge flow from the positive displacement pump device may be directed to the main pump outlet during pump priming and engine start-up and, alternately, to a jet nozzle provided in series with the centrifugal impeller stage to provide motive flow therefor under idle and in-flight conditions. During engine prime and start-up, free rotation of the impeller may be restrained by a clutch responsive to impeller discharge pressure to ensure adequate fuel supply delivery by the positive displacement pump device to the engine at low RPM'"'"'s. Alternatively, other hydraulic fluid may be used as the pumping media for the positive displacement pump, and an auxiliary start pump provided for use during pump prime and engine start-up.

Claims

1. A variable speed, variable output pump for an aircraft fuel system comprising a housing having a main inlet and a main outlet, a jet pump nozzle downstream of said main inlet, an impeller downstream of said jet nozzle and in fluid series therewith, positive displacement pump means for controllingly, drivingly connecting said impeller to the aircraft engine, the speed of said impeller relative to engine speed being variable in response to the discharge flow rate of said pump means, and valve means for controlling the discharge flow rate of said pump means thereby to vary impeller speed relative to the engine speed and for directing discharge flow of said pump means to said main outlet and to said jet nozzle to provide motive flow therefor.

2. A pump for an aircraft fuel system comprising a centrifugal impeller stage, fluid coupling means for controllingly, drivingly connecting said impeller stage to the engine of the aircraft to facilitate matching of fuel flow and pressure to engine requirements, said fluid coupling means comprising rotating input and output members, and positive displacement pump means for fluidly coupling said input and output members, the relative speed of said output member to said input member being variable in response to the discharge flow rate of said pump means, valve means for controlling the discharge flow rate of said pump means thereby fluidly to vary the relative speed of said output member to said input member, an electronic computer operatively connected to the engine to sense various engine parameters, and means operatively connecting said valve means to said computer so as to be controlled in accordance with the parameters sensed thereby to control the speed of the centrifugal impeller stage to match fuel flow and pressure to engine requirements.

3. A pump for an aircraft fuel system comprising a centrifugal impeller stage, fluid coupling means for controllingly, drivingly connecting said impeller stage to the engine of the aircraft to facilitate matching of fuel flow and pressure to engine requirements, said fluid coupling means comprising rotating input and output members, and positive displacement pump means for fluidly coupling said input and output members, the relative speed of said output member to said input member being variable in response to the discharge flow rate of said pump means, valve means for controlling the discharge flow rate of said pump means thereby fluidly to vary the relative speed of said output member to said input member, a main inlet and outlet for said pump for respectively receiving and discharging fuel, means for directing a portion of the fuel to said positive displacement pump means for use as its pumping media, and a jet pump stage in series with said impeller stage, said valve means being operative to direct discharge flow from said pump means to said jet pump stage to provide the motive force therefor.

4. The pump of claim 3 wherein said valve means is operative to direct the discharge flow of said pump means to said main outlet during engine start-up and to said jet pump during normal operating conditions.

5. The pump of claim 4 wherein said input member comprises an input shaft adapted for driving connection to the engine and said output member comprises an output shaft, and the impeller of said impeller stage is mounted on said output shaft for rotation therewith.

6. The pump of claim 5 further comprising means to restrain free rotation of said output shaft during engine start-up.

7. The pump of claim 6 wherein said means to restrain further comprises means for gradually releasing said output shaft as impeller discharge pressure rises.

8. The pump of claim 7 wherein said means to restrain comprises a cone-clutch responsive to positive displacement device discharge pressure.

9. A pump for an aircraft fuel system comprising a centrifugal impeller stage, fluid coupling means for controllingly, drivingly connecting said impeller stage to the engine of the aircraft to facilitate matching of fuel flow and pressure to engine requirements, said fluid coupling means comprising rotating input and output members, and positive displacement pump means for fluidly coupling said input and output members, the relative speed of said output member to said input member being variable in response to the discharge flow rate of said pump means, valve means for controlling the discharge flow rate of said pump means thereby fluidly to vary the relative speed of said output member to said input member, a positive displacement start-up pump in parallel with said impeller stage, and means for operatively driving said start-up pump during engine start-up and for disengaging said start-up pump after start-up is achieved, said means for operatively driving comprising a centrifugal clutch connected to said output shaft.

10. In combination, an aircraft engine and a fuel pump therefor, said fuel pump including a centrifugal impeller stage for pumping fuel to said engine, fluid coupling means for controllingly, drivingly connecting said impeller stage to said engine to permit fuel flow and pressure to be matched to engine requirements, said fluid coupling means comprising rotating input and output shafts drivingly connected, respectively, to said engine and said centrifugal impeller stage, positive displacement pump means for fluidly coupling said input and output shafts, the relative speed of said output shaft to said input shaft being variable in response to the discharge flow rate of said pump means, barrier valve means for controllingly blocking discharge flow from said pump means thereby hydraulically to vary the relative speed of said output shaft to said input shaft, computer means operatively connected to the engine to sense various engine parameters, and means operatively connecting said valve means to said computer means so as to be controlled in accordance with the parameters sensed thereby to control the speed of the centrifugal impeller stage to match fuel flow and pressure to engine requirements.

11. The combination of claim 10 further comprising a main inlet and outlet for said pump for respectively receiving and discharging fuel, said pump means using the fuel as its pumping media.

12. The combination of claim 11 further comprising a jet pump stage in series with said impeller stage, said valve means being operative to direct discharge flow of said pump means to said jet pump stage to provide the motive force therefor and to said main outlet.

13. The combination of claim 12 wherein said discharge flow of said pump means is directed to said main outlet during engine start-up and to said jet pump during normal operating conditions.

14. The combination of claim 13 further comprising means to restrain free rotation of said output shaft during engine start-up.

15. A pump for an aircraft fuel system comprising a centrifugal impeller stage, fluid coupling means for controllingly, drivingly connecting said impeller stage to the engine of the aircraft to facilitate matching of fuel flow and pressure to engine requirements, said fluid coupling means comprising rotating input and output members, and positive displacement pump means for fluidly coupling said input and output members, said centrifugal impeller stage being directly driven by said output member, said positive displacement pump means including means for varying the relative speed of said output member to said input member in response to changes in the discharge flow rate of said pump means, and valve means for controlling the discharge flow rate of said pump means thereby fluidly to vary the relative speed of said output member to said input member.

16. The pump of claim 15 further comprising means for sensing various engine parameters and controlling said valve means in accordance with the parameters sensed thereby to control the speed of the centrifugal impeller stage to match fuel flow and pressure to engine requirements.

17. The pump of claim 16 further comprising a main inlet and outlet for said pump for respectively receiving and discharging fuel, and means for directing a portion of the fuel to said positive displacement pump means for use as its pumping media.

18. The pump of claim 15 wherein the impeller of said impeller stage is mounted on said output member for rotation therewith.

19. The pump of claim 18 wherein said output member has a central passage providing an inlet to said pump means proximate the impeller of said impeller stage, and filter means in said inlet for filtering the fuel received therethrough, said filter means being so positioned in said inlet so as to be cleansed by fuel passing thereover.

20. The pump of claim 15 further comprising means to restrain free rotation of said output member during engine start-up, said means being operative to gradually release said output member as impeller discharge pressure rises.

21. The pump of claim 20 wherein said means to restrain comprises a clutch responsive to positive displacement pump discharge pressure.

22. The pump of claim 15 further comprising a positive displacement start-up pump in parallel with said impeller stage, and means for operatively driving said start-up pump during engine start-up and for disengaging said start-up pump after start-up is achieved.

23. The pump of claim 15 wherein said pump means comprises a gear-type positive displacement pump, said gear-type positive displacement pump including a driving gear connected to said input shaft and a driven gear carried by a rotatable casing, said output shaft being connected to said casing for rotation therewith.

24. In combination, an aircraft engine and a fuel pump therefor, said fuel pump including a centrifugal impeller stage for pumping fluid to said engine, fluid coupling means for controllingly, drivingly connecting said impeller stage to said engine to permit fuel flow and pressure to be matched to engine requirements, and means for sensing various engine parameters and controlling said fluid coupling means in accordance with the parameters sensed thereby through a variable flight profile to control the speed of the centrifugal impeller stage to match fuel flow and pressure to engine requirements throughout such variable flight profile.