Multi-stage variable-speed pump

Description

BACKGROUND

[0001] The subject matter disclosed herein relates to gear driven fuel pumps for aircraft.

[0002] Gear driven fuel pumps can be utilized within an aircraft to provide fuel pressure to engines and hydraulic actuators. Fuel pumps are designed and specified to provide a desired amount of fuel under peak demand conditions. Often, fuel pumps may pump excess fuel flow under lower demand conditions which may heat fuel. Fuel pumps are known from EP 2562420, WO 02 / 25112, US 2016 / 025192, US 4,420,289, US 2011 / 129359 and DE 10104635.BRIEF SUMMARY

[0003] According to one aspect, there is provided a multi-stage gear pump as defined in claim 1.

[0004] According to another aspect, there is provided a method to operate a multi-stage gear pump as defined in claim 7.

[0005] Technical function of the embodiments described above includes a variable speed gearbox including an input and an output, wherein the input is rotationally coupled to the first pump stage and the input rotates at a first rotational speed, and the output is rotationally coupled to the second pump stage and rotates at a second rotational speed, wherein a variable gear ratio determines the second rotational speed relative to the first rotational speed.

[0006] Other aspects, features, and techniques of the embodiments will become more apparent from the following description taken in conjunction with the drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The subject matter is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the embodiments are apparent from the following detailed description taken in conjunction with the accompanying drawings in which like elements are numbered alike in the FIGURES: FIG. 1 is a schematic view of an embodiment of a multi-stage gear pump according to the claims; FIG. 2 is a schematic view of an illustrative example, not according to the claims, of a multi-stage gear pump; and FIG. 3 is a schematic view of another illustrative example, not according to the claims, of a multi-stage gear pump. DETAILED DESCRIPTION

[0008] Referring to the drawings, FIG. 1 shows a pump system 100. The pump system 100 includes a multi-stage gear pump 101 including a main pump gear stage 102, an actuator gear stage 104, and a variable speed gearbox 110. The multi-stage gear pump 101 can provide a desired fuel flow through either a main pump gear stage 102 or an actuator gear stage 104 by adjusting the gear ratio of the variable speed gearbox 110. Advantageously, the use of the variable speed gearbox 110 allows for the actuator gear stage 104 to be driven at a different speed than the main pump gear stage 102 to allow for a desired amount of fuel to be delivered by both the main pump gear stage 102 and the actuator gear stage 104 on demand without any excess fuel pumping. Further, by reducing excess fuel pumping, heating of fuel can be reduced preventing varnish or coking of fuel within the fuel system and the aircraft.

[0009] In the illustrated embodiment, the pump stages 102, 104, 106 of the multi-stage gear pump 101 can be located in a common housing, while in other embodiments, the pump stages 102, 104, 106 can be located in separate housings. The multi-stage gear pump 101 receives rotational energy from a rotational device 119. The rotational device 119 can be a rotational drive from an engine, an engine gearbox or any other power source. The rotational device 119 can rotate the input shaft 122 at a first rotational speed 120. The first rotational speed 120 can vary in accordance with operational speed of the rotational device 119.

[0010] The main pump gear stage 102 is driven by the rotational device 119. The main pump gear stage 102 includes a rotational input 103a and a rotational output 103b associated with the gears within the main pump gear stage 102. The main pump gear stage 102 supplies fuel to an engine of an aircraft. The main pump gear stage 102 speed and fuel output are related to the rotational speed of the main pump gear stage 102.

[0011] The main pump gear stage 102 can receive rotational input from the rotational device 119 via the rotational input 103a. The rotational device 119 can rotate the input shaft 122 to rotate the rotational input 103a. In the illustrated embodiment, the rotational input 103a is a pass through that allows the input shaft 122 to pass therethrough while driving the rotational input 103a. The pass through of the rotational input 103a can allow multiple devices to be rotated by the same shaft that passes therethrough.

[0012] Further, the main pump gear stage 102 can provide a rotational output via the rotational output 103b. Rotation of the gears within the main pump gear stage 102 can drive the rotational output 103b. The rotational output 103b can rotate an output shaft, such as centrifugal boost shaft 126 to drive other rotating components, at least including the centrifugal boost stage 106.

[0013] The rotational output 103b has a relative gear ratio to drive the rotational output 103b at a different rotational speed. Accordingly, the rotational output 103b can drive the centrifugal boost shaft 126 at a rotational speed varying from the first rotational speed 120.

[0014] In certain embodiments, the rotational output 103b is a pass through that allows an output shaft to pass therethrough. The pass through of the rotational output 103b can allow multiple devices to be rotated by the same shaft that passes therethrough.

[0015] The centrifugal boost stage 106 can receive rotational input from the rotational output 103b of the main pump gear stage 102. The rotational output 103a can rotate the centrifugal boost shaft 126 to rotate the centrifugal boost stage 106. The centrifugal boost stage 106 can be rotated at the same speed as the rotational output 103b.

[0016] The centrifugal boost stage 106 is a pump to boost fuel pressure as needed. In the illustrated embodiment, the rotational speed of the centrifugal boost pump 106 corresponds to the output of the centrifugal boost pump.

[0017] The actuator gear stage 104 is driven by the variable speed gearbox 110. The actuator gear stage 104 includes a rotational input 105a and a rotational output 105b associated with the gears within the actuator gear stage 104. The actuator gear stage 104 supplies fuel to fueldraulic / hydraulic actuators within the aircraft. The actuator gear stage 104 speed and fuel output corresponds to the rotational speed of the actuator gear stage 104. In the illustrated embodiment, the actuator gear stage 104 typically has lower fuel flow demands than the main fuel pump, and may have different fuel demands at different times.

[0018] The actuator gear stage 104 can receive rotational input from the variable speed gearbox 110 via the rotational input 105a. The variable speed gearbox 110 can rotate an output shaft 124 to rotate the rotational input 105a. In the illustrated embodiment, the rotational input 105a is a pass through that allows a shaft to pass therethrough while driving the rotational input 105a. The pass through of the rotational input 105a can allow multiple devices to be rotated by the same shaft that passes therethrough.

[0019] Further, the actuator gear stage 104 can provide a rotational output via the rotational output 105b. In the illustrated embodiment, rotation of the gears within the actuator gear stage 104 can drive the rotational output 105b. In the illustrated embodiment, the rotational output 105b can rotate an output shaft to drive other rotating components. In certain embodiments, the rotational output 105b can rotate at the same second rotational speed 121 that is received via the rotational input 105a.

[0020] In other embodiments, the rotational output 105b can have a relative gear ratio and drive the rotational output 105b at a different rotational speed. Therefore, in certain embodiments, the rotational output 105b can drive rotational components at a rotational speed varying from the second rotational speed 121.

[0021] In certain embodiments, the rotational output 105b is a pass through that allows an output shaft to pass therethrough. The pass through of the rotational output 105b can allow multiple devices to be rotated by the same shaft that passes therethrough.

[0022] The variable speed gearbox 110 is connected to the input shaft 122 and the output shaft 124. The variable speed gearbox 110 can receive a first rotational speed 120 of the input shaft 122 and can output and adjust the second rotational speed 121 of the output shaft 124. Advantageously, the second rotational speed 121 of the output shaft 124 can be adjusted by adjusting the gear ratio of the variable speed gearbox 110 in response to fuel demands.

[0023] In the illustrated embodiment, the variable speed gearbox 110 can include any suitable combination of gears or other power transmission to variably adjust the second rotational speed 121 of the output shaft 124. In the illustrated embodiment, the variable speed gearbox 110 can rotate the output shaft 124 at a second rotational speed 121 slower than the first rotational speed 120 of the input shaft 122 or faster than the first rotational speed 120 of the input shaft 122.

[0024] Advantageously, since the second rotational speed 121 of the output shaft 124 corresponds to the pump output of the pump rotationally connected to the output shaft 124, the fuel flow output of the corresponding pump can be adjusted by varying the gear ratio of the variable speed gearbox 110.

[0025] In the illustrated embodiment a controller 112 and an electronic engine controller 114 can work in conjunction to control the second rotational speed 121 of the output shaft 124 in response to fuel demands and other operating conditions. The electronic engine controller 114 can provide operational parameters including engine fuel demands, actuator flow demands, fuel temperature, fuel pressure, fuel flow rates, etc. to determine the current demand for the main pump gear stage 102 and the actuator gear stage 104. The electronic engine controller 114 can provide operational parameters to the controller 112 to control the variable speed gearbox 110 to provide a desired second rotational speed 121 of the output shaft 124.

[0026] For example, during periods of low engine load and high actuator load, it may be desired to overdrive the output shaft 124 to provide a higher second rotational speed 121 relative to the first rotational speed 120 of the input shaft 122. Further, during periods of high engine load and low actuator load, the output shaft 124 can be rotated at a lower second rotational speed 121. The controller 112 can further take into account the size and displacement of the pumps associated with the main pump gear stage 102 and the actuator pump stage 104. Advantageously, by varying the speed of the pump stages 102, 104 pumps can be sized based on different parameters and not peak demand. Advantageously pump speeds can be increased under demand and reduced under periods of low demand. Further, unnecessary heating of fuel can be reduced, reducing coking and varnishing of fuel.

[0027] Referring to FIG. 2, an alternative example, not according to the claims, of the multi-stage gear pump 101 is shown. In the illustrated example, the actuator gear stage 104 is directly driven by the rotational device 119 and the main fuel pump 102 is driven by the variable speed gearbox 110. In the illustrated example, the centrifugal boost stage 106 is driven by the rotational output 105b of the actuator gear stage 104. Advantageously, the actuator gear stage 104 can be directly driven to provide greater flow from the actuator pump in applications that require high actuator fuel flow.

[0028] Referring to FIG. 3, an alternative example, not according to the claims, of the multi-stage gear pump 101 is shown. In the illustrated example, the actuator gear stage 104 is directly driven by the rotational device 119 and the main fuel pump 102 is driven by the variable speed gearbox 110. In the illustrated example, the centrifugal boost stage 106 is driven by the rotational output 103b of the main pump gear stage 102. Advantageously, the actuator gear stage 104 can be directly driven to provide greater flow from the actuator pump in applications that require high actuator fuel flow. Further, by arranging the centrifugal boost shaft 126 to be driven by the main pump gear stage 102 the multi-stage gear pump 101 can be packaged for a suitable location or application.

Claims

1. A multi-stage gear pump, comprising: a rotating device (119) to which an input shaft (122) is connected; a first pump stage (102) configured to supply fuel to an engine of an aircraft, the first pump stage comprising a rotational input (103a) and a rotational output (103b); a second pump stage (104) configured to supply fuel to aircraft actuators, the second pump stage comprising a rotational input (105a) to which an output shaft (124) is connected and a rotational output (105b); and a variable speed gearbox (110) including an input and an output, wherein the input is rotationally coupled to the rotational input of the first pump stage via the input shaft and the input rotates at a first rotational speed (120), and the output is rotationally coupled to the rotational input of the second pump stage via the output shaft and rotates at a second rotational speed (121), wherein a variable gear ratio determines the second rotational speed relative to the first rotational speed; further comprising a boost stage (106) configured to boost the pressure of the fuel, wherein: the boost stage is rotationally coupled to the rotational output of the first pump stage via boost shaft (126), and the rotational output of the first pump stage drives the boost shaft at a rotational speed varying from the first rotational speed.

2. The multi-stage gear pump of claim 1, further comprising a gearbox controller (112) to adjust the variable gear ratio.

3. The multi-stage gear pump of claim 2, further comprising an electronic engine controller (114) to provide at least one operating parameter to the gearbox controller.

4. The multi-stage gear pump of claim 3, wherein the gearbox controller (112) adjusts the variable gear ratio in response to the at least one operating parameter.

5. The multi-stage gear pump of claim 1, wherein: the first pump stage is a main pump stage (102) or is an actuator pump stage, and the second pump stage is a main pump stage or an actuator pump stage.

6. The multi-stage gear pump of claim 1, wherein the boost stage rotates at the second rotational speed.

7. A method to operate a multi-stage gear pump, comprising: providing a first pump stage configured to supply fuel to an engine of an aircraft, the first pump stage comprising a rotational input, which is receptive of rotational input from a rotating device via an input shaft, and a rotational output; providing a second pump stage configured to supply fuel to aircraft actuators, the second pump stage comprising a rotational input to which an output shaft is connected and a rotational output; rotationally coupling an input of a variable speed gearbox to the rotational output of the first pump stage via the input shaft and rotationally coupling an output of the variable speed gearbox to the rotational input of the second pump stage via the output shaft; rotating the first pump stage at a first rotational speed; determining a second rotational speed relative to the first rotational speed via a variable gear ratio of the variable speed gearbox; and rotating the second pump stage at the second rotational speed; providing a boost stage (106) configured to boost the pressure of the fuel, wherein: the boost stage is rotationally coupled to the rotational output of the first pump stage via a boost shaft (126), and the rotational output of the first pump stage drives the boost shaft at a rotational speed varying from the first rotational speed.

8. The multi-stage gear pump of claim 1, further comprising a common housing in which the first pump stage, the second pump stage and the boost stage are located.

9. The method according to claim 7, further comprising locating the first pump stage, the second pump stage and the boost stage in a common housing.