UAV fuel and lubrication system

Abstract

An unmanned aerial vehicle has an internal combustion engine, and a fuel and lubrication system comprising a fuelling system for fuelling the engine and a lubrication system for delivering lubricating oil to the engine. The fuelling system comprises a fuel reservoir from which fuel can be delivered to the engine. The fuel reservoir comprises a main tank and a header tank. The lubrication system comprises an oil tank. The oil tank is accommodated internally within the main tank to provide an integrated assembly. The arrangement provides for warming of lubrication oil for the UAV engine using several available heat sources. Further, the arrangement facilitates a configuration and layout intended to minimise or negate any undesirable moments of inertia for the UAV during flight as fuel and oil is consumed.

Claims

1. A fuel and lubrication system comprising a fuel reservoir, an oil reservoir, and an oil pump for delivery of oil from the oil reservoir to an engine, wherein the oil reservoir is accommodated internally within the fuel reservoir, wherein the oil pump comprises an electronic oil pump accommodated within the oil reservoir, and wherein the fuel reservoir comprises a main tank and a supplementary tank which can receive fuel from the main tank and from which fuel can be delivered to an engine.

2. The fuel and lubrication system according to claim 1, wherein the oil reservoir is accommodated internally within the main tank of the fuel reservoir.

3. The fuel and lubrication system according to claim 1, wherein the supplementary tank is associated with the main tank, whereby the main tank and the supplementary tank cooperate to provide the fuel reservoir.

4. The fuel and lubrication system according to claim 3, wherein the supplementary tank is accommodated within or closely adjacent to the main tank.

5. The fuel and lubrication system according to claim 4, wherein the supplementary tank is accommodated internally within the main tank.

6. The fuel and lubrication system according to claim 1, further comprising a transfer system for transferring fuel within the fuel reservoir from the main tank to the supplementary tank.

7. The fuel and lubrication system according to claim 6, wherein the transfer system comprises a transfer pump.

8. The fuel and lubrication system according to claim 7, wherein the transfer pump comprises a jet pump supplied by return fuel flow from the engine to the fuel reservoir.

9. The fuel and lubrication system according to claim 1, wherein the oil reservoir comprises an oil tank accommodated internally within the main tank of the fuel reservoir.

10. The fuel and lubrication system according to claim 1, wherein the electronic oil pump comprises an electromagnetically-actuated pump.

11. The fuel and lubrication system according to claim 10, wherein the electromagnetically-actuated pump comprises an electromagnetically-actuated reciprocating-piston pump.

12. The fuel and lubrication system according to claim 11, wherein the electromagnetically-actuated reciprocating-piston pump comprises a solenoid actuated positive displacement pump.

13. The fuel and lubrication system according to claim 1, wherein the electronic oil pump is operable to generate additional heat to assist heating (warming) of oil without pumping of any additional oil.

14. A vehicle having a fuel and lubrication system according to claim 1.

15. The vehicle according to claim 14, further comprising an internal combustion engine operable using fuel and lubricating oil received from the fuel and lubrication system.

16. The vehicle according to claim 14, wherein the vehicle is selected from a group consisting of an unmanned aerial vehicle (UAV), another type of aerial vehicle or aerial craft, a watercraft, and a ground-based vehicle including for a snowmobile.

17. A vehicle engine system comprising an internal combustion engine, a fuel system for fuelling the engine, and a lubrication system for delivering lubrication oil to the engine, the fuel system comprising a fuel reservoir, the lubrication system comprising an oil reservoir and an oil pump for delivery of oil from the oil reservoir to the engine, wherein the oil reservoir is accommodated internally within the fuel reservoir, wherein the oil reservoir is accommodated within the fuel reservoir, and wherein the fuel reservoir comprises a main tank and a supplementary tank which can receive fuel from the main tank and from which fuel can be delivered to the engine.

18. The vehicle engine system according to claim 17, wherein the electronic oil pump is operable to generate additional heat to assist heating of oil without pumping of any additional oil.

19. A vehicle having a vehicle engine system according to claim 17.

20. An unmanned aerial vehicle (UAV) comprising: an airframe; and a propulsion system including an internal combustion engine, a fuel reservoir from which fuel can be delivered to the engine, and an oil reservoir from which lubricating oil can be delivered to the engine; wherein the lubrication system comprises an oil reservoir and an oil pump for delivery of oil from the oil reservoir to the engine; wherein the oil reservoir is accommodated internally within the fuel reservoir to provide an integrated assembly; wherein the oil pump comprises an electronic oil pump accommodated within the oil reservoir; and wherein the fuel reservoir comprises a main tank and a supplementary tank which can receive fuel from the main tank and from which fuel can be delivered to an engine.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further features of the present invention are more fully described in the following description of a non-limiting embodiment thereof. This description is included solely for the purposes of exemplifying the present invention. It should not be understood as a restriction on the broad summary, disclosure or description of the invention as set out above. The description will be made with reference to the accompanying drawings in which:

(2) FIG. 1 is a schematic perspective view of an unmanned aerial vehicle (UAV) having a propulsion system featuring an internal combustion engine and a fuel and lubrication system, according to the invention;

(3) FIG. 2 is a schematic fragmentary side view, illustrating in particular the propulsion system;

(4) FIG. 3 is a schematic side view of the fuel and lubrication system, illustrating in particular a fuel reservoir from which fuel can be delivered to the engine, and an oil reservoir from which lubricating oil can be delivered to the engine; and

(5) FIG. 4 is a schematic sectional view of an electronic oil pump forming part of the fuel and lubrication system.

(6) In the drawings, like structures are referred to by like numerals throughout the various views. The drawings shown are not necessarily to scale, with emphasis instead generally being placed upon illustrating the principles of the present invention.

(7) The figures depict a particular embodiment of the invention. The embodiment illustrates a certain configuration; however, it is to be appreciated that the invention can take the form of many configurations, as would be obvious to a person skilled in the art, while still embodying the present invention. These configurations are to be considered within the scope of the invention.

DESCRIPTION OF EMBODIMENTS

(8) Referring to FIG. 1, there is shown an example embodiment of an unmanned aerial vehicle (UAV) depicted generally by reference numeral 10. The example embodiment UAV 10 comprises an airframe 11 including a fuselage 13 and wings 14. The example embodiment UAV 10 further comprises a propulsion system 15 comprising a propeller 16 and a propulsion module 17 for driving the propeller. In the arrangement shown, the propeller 16 is configured as a pusher propeller, but it need not necessarily be so. By way of example, in other arrangements the propeller 16 may be configured as a tractor propeller.

(9) As best seen in FIG. 2, the propulsion module 17 includes an internal combustion engine 19, and a fuel and lubrication system comprising a fuelling system 21 for fuelling the engine and a lubrication system 23 for delivering lubricating oil to the engine. An engine control unit (ECU) is provided for controlling operation of the engine 19 in known manner, as well as operation of the fuelling system 21 and the lubrication system 23.

(10) The fuelling system 21 comprises a fuel reservoir 25 from which fuel can be delivered to the engine, a fuel supply circuit 27 for transporting fuel from the fuel reservoir 25 to the engine, and a fuel return circuit 29 for returning excess fuel to the engine to the fuel reservoir 25. In this embodiment, the fuelling system 21 further comprises a fuel injection system (not shown) having a fuel rail containing a fuel regulator, with the fuel rail being in fluid communication with both the fuel supply circuit 27 and the fuel return circuit 29.

(11) The lubrication system 23 comprises an oil reservoir in the form of an oil tank 31.

(12) The oil tank 31 is accommodated internally within the fuel reservoir 25 to provide an integrated assembly 33, as shown in FIG. 3 and as will be described in more detail later.

(13) The integrated assembly 33 is preferably so positioned within the fuselage 13 with respect to the centre of gravity of the UAV 10 such that variations in fuel mass within the fuel reservoir 25 and oil mass within the oil tank 31 do not cause a significant shift in the position of the centre of gravity and hence do not result in any unwanted moments of inertia for the UAV during flight. The integrated assembly 33 also provides for a compact configuration, which may be beneficial in assisting in the UAV design process. This is the case in this example embodiment where the UAV 10 has size constraints in accommodating the propulsion system 17 within the fuselage 13, particularly in achieving a configuration and layout which satisfies considerations with respect to the centre of gravity and minimising moments of inertia for the UAV.

(14) In the arrangement shown, and as best seen in FIG. 3, the fuel reservoir 25 comprises a main tank 41 and a supplementary tank 43. The supplementary tank 43 will hereinafter be referred to as a header tank. The header tank 43 is accommodated internally within the main tank 41 so as to be surrounded by fuel in the main tank 41. This arrangement is advantageous, as any leakage from the header tank 43 would merely be into the main tank 41 and as such unlikely to be of any adverse consequence.

(15) The oil tank 31 is also accommodated internally within the main tank 41 so as to be surrounded by fuel in the main tank 41. With this arrangement, thermal energy (heat) within fuel contained within the main tank 41 may be transferred to the oil tank 31 for heating (warming) of the oil therein, as will be discussed in more detail later.

(16) The main tank 41, header tank 43 and oil tank 31 are each of a fixed size and volume.

(17) The header tank 43 is arranged to receive fuel from the main tank 41 by way of a transfer system 45 comprising a transfer pump 47. In the arrangement show, the transfer pump 47 comprises a jet pump supplied by return fuel flow from the engine via the fuel return circuit 29. The jet pump 47 has an inlet 48 in communication with the main tank 41 via filter 49. It is, however, to be understood that the jet pump 47 and/or transfer system 45 could in certain arrangements include an inlet comprising multiple pick-up points, with or without filters, through which fuel is drawn into the header tank 43. The jet pump 47 also has a discharge tube 50.

(18) A fuel pump 51 is also accommodated internally within the header tank 43. In the arrangement shown, the fuel pump 51 comprises an electric fuel pump operable under control of the ECU. The electric fuel pump 51 is configured to receive power by way of electrical wires 52. The fuel pump 51 has an intake 53 in communication with the header tank 43 via filter 55. Similarly as above, it should be appreciated that the fuel pump 51 could in certain arrangements include an intake comprising multiple pick-up points, with or without filters, through which fuel is drawn into the fuel pump 51 for delivery therefrom. In the arrangement shown, the filter 55 is a wicking filter of known kind. The fuel pump 51 has a discharge outlet 56 in fluid communication with the fuel supply circuit 27 for transporting fuel from the fuel reservoir 25 to the engine 19.

(19) The header tank 43 has an inlet 57 through which the tank can be filled with fuel as necessary. The header tank 43 also includes a vent 58 for venting the interior of the tank and overflow into the main tank 41 via a one-way valve. It should however be understood that in alternative arrangements, venting of the header tank 43 may be facilitated by way of a suitably arranged orifice instead of a one-way valve. The header tank 43 also has a fuel level switch or sensor 59.

(20) The lubrication system 23 further comprises an oil pump 61 for delivering oil from the oil tank 31 to the engine 19 along oil supply circuit 62.

(21) The oil tank 31 has an inlet 63 through which the tank can be filled with oil as necessary. The oil tank 31 also includes a vent 65 for venting the interior of the tank, and a level switch or sensor 67.

(22) The oil pump 61 comprises an electronic oil pump operable under control of the ECU and configured to receive power by way of electrical wires 69. The electronic oil pump may comprise an electromagnetically-actuated reciprocating-piston pump, and more particularly a solenoid-actuated positive displacement piston pump, which is the case in this embodiment.

(23) In the arrangement shown, and as best seen with reference to FIG. 4, the electronic oil pump 61 comprises a pump body 71 having an inlet 73 and an outlet 75. The pump body 71 defines an internal cavity 77 between the inlet 73 and the outlet 75. An electromagnetic piston 79 is mounted for sliding reciprocating motion within the cavity 77. An electromagnetic coil 81 surrounds the electromagnetic piston 79, thereby providing a solenoid arrangement for electromagnetically operating the piston 79 in known manner.

(24) The piston 79 is movable axially between two end positions within the cavity 77. The two end positions are defined by the opposed ends of the cavity 77 in the axial direction of movement of the piston 79 within the cavity.

(25) The piston 79 cooperates with the cavity 77 to define a pumping chamber 83 of variable volume, with sliding reciprocating motion of the piston within the cavity causing volume expansion and volume contraction of the pumping chamber. More particularly, the pumping chamber 83 is defined between an end 84 of the piston 79 and a confronting end wall 85 of the cavity 77.

(26) A spring 87, which acts between the piston 79 and end wall 85 of the cavity 77, is operable to bias the piston 79 for motion in a first direction. In the arrangement shown, the first direction corresponds to volume expansion of the pumping chamber 83. Specifically, the spring 87 biases the piston 79 into a position corresponding to the maximum volume condition of the pumping chamber 83.

(27) Energisation of the electromagnetic coil 81 under the control of the engine ECU creates a magnetic attractive force to cause movement of the piston 79 in a second direction against the biasing effect of the spring 87, as would be understood by a person skilled in the art. In the arrangement shown, the second direction corresponds to volume contraction of the pumping chamber 83.

(28) In the arrangement described and illustrated, the spring 87 biases the piston 79 into the maximum volume condition and the electromagnetic coil 81 is operable to cause movement of the piston 79 against the biasing effect of the spring 87 to cause volume contraction of the pumping chamber 83. This arrangement could, of course, be reversed, with the spring 87 biasing the piston 79 into the minimum volume condition and the electromagnetic coil 81 being operable to cause movement of the piston 79 against the biasing effect of the spring 87 to cause volume expansion of the pumping chamber 83.

(29) The piston 79 includes a central bore 91 defining a flow path 93 which communicates at one end 94 with inlet 73. The other end 95 of flow path 93 communicates with the pumping chamber 83 via a one-way inlet valve 96 integrated within the piston 79. The one-way inlet valve 96 is configured to permit flow along flow path 93 from the inlet 73 into the pumping chamber 83 and to prevent flow in the reverse direction. With this arrangement, oil can flow through the inlet 73 and into the pumping chamber 83 upon volume expansion of the pumping chamber 83.

(30) The outlet 75 communicates with the pumping chamber 83 via a one-way outlet valve 97. The one-way outlet valve 97 is configured to permit flow from the pumping chamber 83 and to prevent flow in the reverse direction. With this arrangement, oil can be discharged under pressure from within the pumping chamber 83 to the outlet 75 upon volume contraction of the pumping chamber.

(31) The alternating action of the magnetic attractive force produced by intermittent current flowing through the electromagnetic coil 81 under the control of the engine ECU, and the biasing force of spring 87 causes the piston 79 to reciprocate with the cavity 77, thereby causing volume contraction and expansion of the pumping chamber 83 and thus delivery of oil from the inlet 73 to the outlet 75, and more specifically pumping of oil from the pumping chamber 83 through the outlet valve 97 and outlet 75.

(32) Operation of the solenoid actuated positive displacement piston pump 61 may generate additional heat to assist heating (warming) of oil within the oil tank 31, as will be discussed further later.

(33) As alluded to above, there are several sources of heat for heating (warming) the lubrication oil, including heat transfer from the fuel, heat available from operation of the electronic oil pump 61, and heat received from the internal combustion engine 19. Heating of the lubrication oil may be beneficial in certain circumstances; for example, at start-up, and also for a UAV engine likely to experience operation at high altitude conditions or prolonged operation in cold environments.

(34) In relation to heat transfer from fuel, the fuel may accumulate heat from various sources, including for example heat generated by operation of the electronic fuel pump 51 to which the fuel is exposed, and heat from the engine 19. Heat from the engine 19 may be by way of conduction and/or heat transfer through circulation of fuel between the fuel reservoir 25 and the engine via fuel supply circuit 27 (transporting fuel from the fuel reservoir 25 to the engine) and also the fuel return circuit 29 (returning excess fuel to the engine to the fuel reservoir 25). In particular, as the engine 19 becomes hot during normal operation, the fuel rail and associated fuel regulator increase in temperature, transferring heat to return fuel flowing back to the fuel reservoir 25 along fuel return circuit 29. The return fuel, which as a consequence is at an elevated temperature condition, mixes with fuel within the header tank 43 to effect heating of the fuel.

(35) It is believed heating available through heat generated by operation of the electronic fuel pump 51 in this embodiment may be about 7 W. Further, it is believed heating available through recirculation of fuel in this embodiment may be in the order of about 10 to 100 W.

(36) Still further, it is believed that heating available to the oil from the engine may be by way of conduction along an oil delivery line within oil supply circuit 62, and may be in the order of about 1 to 5 W in this embodiment.

(37) Furthermore, it is believed heating available through heat transfer from the electronic oil pump 61 in this embodiment may be about 2 to 3 W.

(38) In relation to heat transfer from the electronic oil pump 61, heat may be generated in several ways through operation of the electronic oil pump.

(39) Firstly, the mere operation of the electronic oil pump 61 will likely generate heat. Specifically, the electromagnetically-actuated piston pump 61 has electromagnetic coil 81 adapted to be energised by an electrical supply, with energisation of the electromagnetic coil generating heat. Additionally, heat will also likely be generated through frictional effects upon movement of the piston 79 within the pump 61.

(40) Secondly, the electromagnetically-actuated piston pump 61 may be operated according to a control strategy to provide additional heat. By way of example, over-energisation of the electromagnetic coil 81 can be used to heat the oil pump 61 and consequently heat the oil surrounding the pump. In other words, the electromagnetic coil 81 can be energised for a time period longer than the stroke period of the pump 61, whereby the additional energy, which cannot induce further movement of the piston 79 because the piston is at the end of its stroke, is dissipated as heat. Put another way, the electromagnetic coil 81 is energised for a period of time to cause heating of the oil without continuously pumping the oil. In this way, the electromagnetically-actuated piston pump 61 is selectively operable to generate additional heat to assist heating (warming) of oil without pumping of any additional oil.

(41) The electronic oil pump 61 may be controlled by the engine ECU, with the ECU being operable to vary the energisation period of the electromagnetic coil 81 to effect a lubrication oil heating strategy.

(42) It is believed heating available through heat transfer from the electronic oil pump 61 in this embodiment may be about 2 to 3 W.

(43) From the foregoing, it is evident that the present example embodiment provides unmanned aerial vehicle (UAV) 10 having the capacity to heat (warm) lubrication oil required for the UAV engine, using heat sources onboard the UAV. This heating can be accomplished relatively rapidly, using the various available heat sources as described, and in particular through adoption of a lubrication oil heating strategy involving operation of the electromagnetically-actuated piston pump in a manner to vary the energisation period of the electromagnetic coil to generate additional heat.

(44) This can be beneficial in circumstances where the UAV may be required to undergo missions likely to encounter high altitude conditions or likely to involve prolonged operation in cold environments.

(45) Further, the present example embodiment provides unmanned aerial vehicle (UAV) 10 having the propulsion system 15 accommodated in a configuration and layout which satisfies considerations with respect to the centre of gravity so as to minimise or negate any undesirable moments of inertia for the UAV. In particular, the oil tank 31 accommodated internally within the fuel reservoir 25 provides integrated assembly 33 which can be so positioned within the airframe 11 with respect to the centre of gravity of the UAV such that variations in fuel mass within the fuel reservoir 25 and oil mass within the oil tank 31 do not cause a significant shift in the position of the centre of gravity, hence avoiding the generation of unwanted moments of inertia for the UAV during flight. The integrated assembly 33 also provides for a compact configuration, which may be beneficial in assisting in the UAV design process. This is the case in the example embodiment where the UAV 10 has size constraints in accommodating the propulsion system 17 within the fuselage 13, particularly in achieving a configuration and layout which satisfies considerations with respect to the centre of gravity and minimising moments of inertia for the UAV.

(46) In the example embodiment described, heating (warming) of lubrication oil required for the UAV engine involved use of the various available heat sources as described. It should be appreciated that in other embodiments only one or more, and not necessarily all, of the heat sources described may be used. Further, in other embodiments there may be one or more auxiliary heating sources provided to assist in heating (warming) of lubrication oil required for the UAV engine. By way of example, there may be one or more heating devices, such as dedicated heater elements, operable to assist in heating (warming) of lubrication oil. The auxiliary heating sources may have temperature control systems, although this need not necessarily be so.

(47) Modifications and improvements may be made without departing from the scope of the invention. In particular, while the present invention has been described in terms of a preferred embodiment in order to facilitate better understanding of the invention, it should be appreciated that various modifications can be made without departing from the principles of the invention. Therefore, the invention should be understood to include all such modifications within its scope.

(48) Reference to positional descriptions, such as lower, upper, top and bottom are to be taken in context of the embodiment depicted in the drawings, and are not to be taken as limiting the invention to the literal interpretation of the term but rather as would be understood by the skilled addressee.

(49) Additionally, where the terms system, device, apparatus are used in the context of the invention, they are to be understood as including reference to any group of functionally related or interacting, interrelated, interdependent or associated components or elements that may be located in proximity to, separate from, integrated with, or discrete from, each other.

(50) The invention described herein includes a range of preferred heat energy values presented in Watts (W) in relation to heat available for heating (warming) the lubrication oil. It should be understood that the heat energy values are provided for indicative purposes only and that the invention is in no way to be considered to be limited to such values. All heat energy values which achieve the same or substantially the same outcomes are to be considered to be within the scope of the invention.

(51) Throughout this specification, unless the context requires otherwise, the word comprise or variations such as comprises or comprising, will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.