Variable speed multi-stage pump

A multi-stage gear pump includes a first pump stage, a second pump stage, and 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.

BACKGROUND

The subject matter disclosed herein relates to gear driven fuel pumps, and more particularly, to gear driven fuel pumps for aircraft.

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.

BRIEF SUMMARY

According to an embodiment, a multi-stage gear pump includes a first pump stage, a second pump stage, and 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.

According to an embodiment, a method to operate a multi-stage gear pump includes providing a first pump stage, providing a second pump stage, rotationally coupling an input of a variable speed gearbox to the first pump stage, 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, rotationally coupling an output of the variable speed gearbox to the second pump stage, and rotating the second pump stage at the second rotational speed.

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.

Other aspects, features, and techniques of the embodiments will become more apparent from the following description taken in conjunction with the drawings.

DETAILED DESCRIPTION

Referring to the drawings,FIG. 1shows a pump system100. In the illustrated embodiment, the pump system100includes a multi-stage gear pump101including a main pump gear stage102, an actuator gear stage104, and a variable speed gearbox110. In the illustrated embodiment, the multi-stage gear pump101can provide a desired fuel flow through either a main pump gear stage102or an actuator gear stage104by adjusting the gear ratio of the variable speed gearbox110. Advantageously, the use of the variable speed gearbox110allows for the actuator gear stage104to be driven at a different speed than the main pump gear stage102to allow for a desired amount of fuel to be delivered by both the main pump gear stage102and the actuator gear stage104on 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.

In the illustrated embodiment, the pump stages102,104,106of the multi-stage gear pump101can be located in a common housing, while in other embodiments, the pump stages102,104,106can be located in separate housings and commonly driven or otherwise operatively connected. In the illustrated embodiment, the multi-stage gear pump101receives rotational energy from a rotational device119. The rotational device119can be a rotational drive from an engine, an engine gearbox or any other power source. The rotational device119can rotate the input shaft122at a first rotational speed120. The first rotational speed120can vary in accordance with operational speed of the rotational device119.

In the illustrated embodiment, the main pump gear stage102is driven by the rotational device119. In the illustrated embodiment, the main pump gear stage102includes a rotational input103aand a rotational output103bassociated with the gears within the main pump gear stage102. The main pump gear stage102supplies fuel to an engine of an aircraft. The main pump gear stage102speed and fuel output are related to the rotational speed of the main pump gear stage102.

The main pump gear stage102can receive rotational input from the rotational device119or any other suitable power source via the rotational input103a. In the illustrated embodiment, the rotational device119can rotate an input shaft122to rotate the rotational input103a. In the illustrated embodiment, the rotational input103ais a pass through that allows the input shaft122to pass therethrough while driving the rotational input103a. The pass through of the rotational input103acan allow multiple devices to be rotated by the same shaft that passes therethrough.

Further, the main pump gear stage102can provide a rotational output via the rotational output103b. In the illustrated embodiment, rotation of the gears within the main pump gear stage102can drive the rotational output103b. In the illustrated embodiment, the rotational output103bcan rotate an output shaft, such as centrifugal boost shaft126to drive other rotating components, such as the centrifugal boost stage106. In certain embodiments, the rotational output103bcan rotate at the same first rotational speed120that is received via the rotational input103a.

In other embodiments, the rotational output103bcan have a relative gear ratio and drive the rotational output103bat a different rotational speed. Therefore, in certain embodiments, the rotational output103bcan drive the centrifugal boost shaft126at a rotational speed varying from the first rotational speed120.

In certain embodiments, the rotational output103bis a pass through that allows an output shaft to pass therethrough. The pass through of the rotational output103bcan allow multiple devices to be rotated by the same shaft that passes therethrough.

The centrifugal boost stage106can receive rotational input from the rotational output103bof the main pump gear stage102. The rotational output103acan rotate the centrifugal boost shaft126to rotate the centrifugal boost stage106. The centrifugal boost stage106can be rotated at the same speed as the rotational output103b.

In the illustrated embodiment, the centrifugal boost stage106is a pump to boost fuel pressure as needed. In the illustrated embodiment, the rotational speed of the centrifugal boost pump106corresponds to the output of the centrifugal boost pump.

In the illustrated embodiment, the actuator gear stage104is driven by the variable speed gearbox110. In the illustrated embodiment, the actuator gear stage104includes a rotational input105aand a rotational output105bassociated with the gears within the actuator gear stage104. The actuator gear stage104supplies fuel to fueldraulic/hydraulic actuators within the aircraft. The actuator gear stage104speed and fuel output corresponds to the rotational speed of the actuator gear stage104. In the illustrated embodiment, the actuator gear stage104typically has lower fuel flow demands than the main fuel pump, and may have different fuel demands at different times.

The actuator gear stage104can receive rotational input from the variable speed gearbox110or any other suitable power source via the rotational input105a. In the illustrated embodiment, the variable speed gearbox110can rotate an output shaft124to rotate the rotational input105a. In the illustrated embodiment, the rotational input105ais a pass through that allows a shaft to pass therethrough while driving the rotational input105a. The pass through of the rotational input105acan allow multiple devices to be rotated by the same shaft that passes therethrough.

Further, the actuator gear stage104can provide a rotational output via the rotational output105b. In the illustrated embodiment, rotation of the gears within the actuator gear stage104can drive the rotational output105b. In the illustrated embodiment, the rotational output105bcan rotate an output shaft to drive other rotating components. In certain embodiments, the rotational output105bcan rotate at the same second rotational speed121that is received via the rotational input105a.

In other embodiments, the rotational output105bcan have a relative gear ratio and drive the rotational output105bat a different rotational speed. Therefore, in certain embodiments, the rotational output105bcan drive rotational components at a rotational speed varying from the second rotational speed121.

In certain embodiments, the rotational output105bis a pass through that allows an output shaft to pass therethrough. The pass through of the rotational output105bcan allow multiple devices to be rotated by the same shaft that passes therethrough.

The variable speed gearbox110is connected to the input shaft122and the output shaft124. In the illustrated embodiment, the variable speed gearbox110receive a first rotational speed120of the input shaft122and can output and adjust the second rotational speed121of the output shaft124. Advantageously, the second rotational speed121of the output shaft124can be adjusted by adjusting the gear ratio of the variable speed gearbox110in response to fuel demands.

In the illustrated embodiment, the variable speed gearbox110can include any suitable combination of gears or other power transmission to variably adjust the second rotational speed121of the output shaft124. In the illustrated embodiment, the variable speed gearbox110can rotate the output shaft124at a second rotational speed121slower than the first rotational speed120of the input shaft122or faster than the first rotational speed120of the input shaft122.

Advantageously, since the second rotational speed121of the output shaft124corresponds to the pump output of the pump rotationally connected to the output shaft124, the fuel flow output of the corresponding pump can be adjusted by varying the gear ratio of the variable speed gearbox110.

In the illustrated embodiment a controller112and an electronic engine controller114can work in conjunction to control the second rotational speed121of the output shaft124in response to fuel demands and other operating conditions. The electronic engine controller114can 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 stage102and the actuator gear stage104. The electronic engine controller114can provide operational parameters to the controller112to control the variable speed gearbox110to provide a desired second rotational speed121of the output shaft124.

For example, during periods of low engine load and high actuator load, it may be desired to overdrive the output shaft124to provide a higher second rotational speed121relative to the first rotational speed120of the input shaft122. Further, during periods of high engine load and low actuator load, the output shaft124can be rotated at a lower second rotational speed121. The controller112can further take into account the size and displacement of the pumps associated with the main pump gear stage102and the actuator pump stage104. Advantageously, by varying the speed of the pump stages102,104pumps 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.

Referring toFIG. 2, an alternative embodiment of the multi-stage gear pump101is shown. In the illustrated embodiment, the actuator gear stage104is directly driven by the rotational device119and the main fuel pump102is driven by the variable speed gearbox110. In the illustrated embodiment, the centrifugal boost stage106is driven by the rotational output105bof the actuator gear stage104. Advantageously, the actuator gear stage104can be directly driven to provide greater flow from the actuator pump in applications that require high actuator fuel flow.

Referring toFIG. 3, an alternative embodiment of the multi-stage gear pump101is shown. In the illustrated embodiment, the actuator gear stage104is directly driven by the rotational device119and the main fuel pump102is driven by the variable speed gearbox110. In the illustrated embodiment, the centrifugal boost stage106is driven by the rotational output103bof the main pump gear stage102. Advantageously, the actuator gear stage104can 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 shaft126to be driven by the main pump gear stage102the multi-stage gear pump101can be packaged for a suitable location or application.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the embodiments. While the description of the present embodiments has been presented for purposes of illustration and description, it is not intended to be exhaustive or limited to the embodiments in the form disclosed. Many modifications, variations, alterations, substitutions or equivalent arrangement not hereto described will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the embodiments. Additionally, while various embodiments have been described, it is to be understood that aspects may include only some of the described embodiments. Accordingly, the embodiments are not to be seen as limited by the foregoing description, but are only limited by the scope of the appended claims.