Patent ID: 12252244

DETAILED DESCRIPTION OF EMBODIMENTS

FIG.1illustrates a vertical take-off and landing (VTOL) device100in accordance with embodiments of the invention. The device100is generally sized and configured to carry a human adult user2and this load may be supplemented with an additional payload190. The overall passenger and payload weight carried by the device may therefore be in the region of around 50 to 150 kg. However, in other embodiments the device may be larger or smaller and configured for carrying larger or smaller payloads. Payloads of up to a 150 kg user and a 20 kg payload, or thereabouts are envisaged.

The thrust source for the VTOL device is a fan110. The fan110preferably has a pair of contra-rotating sets of blades113aand113b(blade sets). However, in some embodiments a single rotating blade set113aor113bcan be envisaged. Each blade set is typically mounted to a corresponding rotor. In alternative arrangements, one pair, or two pairs, of contra-rotating blade sets113aand113band113cand113dcan be included. One or more further pairs of contra-rotating fans (not shown) could also be included.

The fan is a ducted fan and so is surrounded by ducting or cowling111. The blade set or sets113a,113b,113c,113dare mounted centrally within the cowling111and are rotatable about a central axis X of the main duct150and cowling111. Central axis X may also be considered a primary axis of the overall device along which one or more components may be substantially aligned. The blade sets may be mounted via variable inlet guide vanes114, which may be replaced or supplemented by other fixed radial mounts.

The set of variable angle guide vanes114at an inlet side of the fan110, may be provided with a structural function for the central dome112and to adjust the angle of attack due to the inlet flow distortions of the air impinging on the blades of the first rotor113a. For the same reasons secondary ducting115may be provided to provide a double-ducted fan.

Most axial flow fans are designed for an inlet flow with minimal inlet flow distortion. The double ducted fan concept is proven to be an effective way of dealing with inlet flow distortions occurring near the lip section of any axial flow fan rotor system. An advantage of providing this secondary ducting115is that when the device is in a vertical take-off or hovering mode, but beginning to traverse, the secondary ducting115can reduce the likelihood of a inlet duct lip stall occurring due to a transverse flow across the top of the cowling111hindering the intake of airflow into the fan110, which could otherwise reduce its ability to generate a downward thrust.

In particular the secondary stationary duct system115controls the “inlet lip separation”111related momentum deficit at the inlet of the fan rotor occurring at elevated forward flight velocities while hovering. Such separation is typical in hovering since there is a local zone in which there are strong radial velocity components distorting the inlet flow and limiting the controllability and speed during “hovering”. A double ducted design can be advantageous also in other scenarios such as with a strong transverse wind which also generates a radial velocity.

Suitable designs can be found in the paper DOUBLE DUCTED FAN (DDF) By Cengiz Camci and Ali Akturk, of the Turbomachinery Aero-heat Transfer Laboratory, Vertical Lift Research Center of Excellence, Department of Aerospace Engineering, The Pennsylvania State University, dated Sep. 3, 2010. In particular the CASE-B short double ducted fan in FIG. 2.4: (a) page 30 is proven to produce the best results in terms of improved mass flow rate passing from the duct (by 40%) and improved thrust force obtained from the ducted fan (by 56.2%) relative to baseline duct in edgewise flight condition. Hence such geometry can be advantageous in embodiments of the present invention.

A central dome or bullet nose112may be provided centrally to the fan110. The blade sets113a,113band/or113cand113d(and any others present) are driven by a drive train120to deliver drive from a drive source to the fan. Where contra-rotating pairs of blade sets are used, it is necessary to generate contra-rotating drives for the contra-rotating blade sets. This can negate any resulting torque generated by the rotating blade sets and acting on the body of the device, which can improve the stability of the device and ease of control, in particular during changes in fan speed. The use of multiple rotors also allows their diameter to be reduced in comparison to an implementation using a single rotor, without impacting efficiency, which can provide a much more compact design. Furthermore, any inlet flow distortion at the duct inlet will be reduced by the first rotor, so that the second and any further rotors will have a much better inlet flows, allowing improved efficiency. A preferred configuration is with one inner shaft123connecting a first rotor or set of rotors113aand/or113cand a second, outer, shaft124connecting a second rotor or set of rotors113band/or113d. The inner and outer shafts are connected to an epicyclic gear122which provides a contra-rotation to them. Further this configuration allows much reduced leakage flow since the clearance of the blades in rotors113band113dis towards the hub and not the duct. In further detail, the counter-rotation with no reduction and equal torque among the blade sets can be achieved by using an epicyclic gear122where the sun gear is provided on the main shaft121, which preferably extends directly from the primary drive source. Preferably, the inner shaft123and its blades are driven by the epicyclic carrier shaft, while the outer shaft124with its blades are driven by the epicyclic ring shaft. The primary drive shaft121can therefore drive one or more sets of blades113aand113band113cand113dto generate the necessary thrust for the device. The primary drive shaft121can advantageously be supported by at least one radial bearing141at its lower end, to react primarily radial loads. At an upper end, at least one axial bearing126may support the shaft to react axial loads of the fan impinging on the bearing in reaction to the thrust generated by the fan.

The drive train120is driven from one or more drive sources. In certain embodiments, it is advantageous to provide more than one drive source. A first drive source may be a primary drive source130. In some embodiments this may be an internal combustion engine. The combustion engine may comprise a two stroke engine and it may comprise two cylinders or three cylinders, preferably in line, for high power/weight ratio and optimal use of space, although other configurations and numbers of cylinders can be envisaged for different applications. The primary drive source130includes an output shaft131. The output shaft131may be connected to the drive shaft121via a clutch device125. This can allow engagement and disengagement of the primary drive source130from the drive train120. This may be advantageous, in particular in instances where the primary drive130has failed and it is desired to disconnect it from the drive train120in order to allow drive to be provided from a secondary drive source140. Drive source140may be mounted through-shaft with the drive shaft121to save any transmission weight (if no reduction is necessary). If a gear train, gear box or transmission is present between an output of the primary or secondary drive source and the fan110, numerous types can be used. Suitable transmission types include a constantly variable transmission (CVT), a fixed reduction gear, epicyclic gear box, or in some examples it may be beneficial to have a gearbox with one or more selectable speeds or transmission ratios.

The clutch125also has the advantage of allowing the drive source130to run without providing any drive to the fan110, if desired. This may be advantageous when running the engine on the ground prior to take-off or after landing. However, as mentioned above, a primary advantage may be the disconnection of the engine in the event of its failure in order to allow a drive to be provided from the secondary drive source140.

Other emergency mechanisms can be provided. One example is a ballistic parachute80, which can be fired to provide rapid deployment of a parachute in the event of high altitude failure of a drive source. However, as mentioned above, a drawback of such parachute mechanisms is that below altitudes of around 150 m, the parachute does not have time to deploy and to provide an effective means of breaking the fall of the device, and its user if present, before impact with the ground. Therefore, particularly below altitudes of around 150 m, it may be advantageous to have available a secondary drive source140which can be activated in the event of a failure of the primary drive source130. A drawback of primary drive sources such as combustion engines, is that they are noisy, in particular during take-off and landing. For this reason, it is also possible to use an alternative drive source such as secondary drive source140, during take-off and/or landing. In this manner, where the secondary drive source140is an electric motor, for example, it can provide a quieter power source for take-off, and then the primary drive source130, which maybe a more noisy combustion engine, can be engaged for higher altitude travel of the device100. The primary drive source130may be delivered energy from a primary energy store160. In some examples this may be a fuel tank160, providing a combustible fuel to a combustion engine130. The device may comprise a main frame, casing or body180. The fuel tank160or other primary energy store may preferably be located outside of the main frame, casing or body180of the device, so that it is located far from hot parts of the device, such as the primary drive source, in particular exhaust manifolds if the primary drive source is an engine. Locating the energy store or sources outside the frame can also allow for easier packaging of more critical components such as the drive source and/or payload and/or electronic control equipment, or electrical components such as a secondary energy store, which can in some examples be a battery and/or supercapacitor. A supercapacitor is a term understood by one skilled in electrical power storage systems with much higher charge and discharge rates than batteries and is typically double layered and carbon-based. A supercapacitor has significantly more capacity and more energy storage capability than a standard capacitor. The secondary drive source140may be an electric motor and may be powered from a secondary energy store161, which may be a store of electrical energy, such as a battery and/or a supercapacitor. Providing primary and secondary drive sources and energy stores which are each of sufficient size and capacity for sustained flight of the device would be likely to result in an excessively heavy and cumbersome device. Therefore, it can be advantageous if the second energy store is configured for significantly shortened operation as compared to the primary drive source.

In this way, the secondary drive source can be used only for emergency landings in the event of a failure of the primary drive source. Additionally or alternatively, the secondary drive source can be used for reduced noise landing and take-off. In either the emergency case, or the reduced noise case, an operating time of between fifteen and seventy five seconds would be sufficient for the secondary drive source. Therefore, the secondary energy store161can be sized and configured to provide sufficient energy for that length of operation. In addition to such uses, the secondary drive source can be used to provide an additional boost to the power delivered by the primary drive source. This can allow the primary drive source to work at a reduced power level. This can enhance the TBO and fuel efficiency of the primary drive source.

A suitable motor preferably has the following performance characteristics, which can include, continuous power output of up to 150 kW, continuous torque of around 250 Nm. Weight is preferably less than around 40 kg. A relatively low speed of the motor can remove the need for a gearbox, so operating speeds of at or below around 6000-4000 rpm are beneficial for use in devices disclosed herein. Avoiding a transmission gearbox can make a 20 kg weight saving, which is significant in devices of this scale.

As for the battery/supercapacitor, the requirement is for a very high energy density and very high discharge rates. State of the art batteries can provide around 35C discharge rate and 140 Wh/kg energy density which for a device of the scale illustrated in the specific example shown, results in around 30 kg of battery weight.

One aspect of the configuration of the primary and secondary drive sources which can be important to the overall efficiency of the device is the relative sizing of the primary and secondary drive sources and the capacity of the primary and secondary energy stores. Each drive source is preferably of sufficient size to provide sufficient thrust to fly the device independently of the other drive source. In practice, the secondary drive source may be used for a far lesser proportion of the operating cycle of the device than the primary drive source, such as is described in relation to silent take-off and landing. Given that the secondary drive source is only preferably intended for emergency use or take-off and landing use, it may be provided with a secondary energy store which is smaller than the primary energy store. This results in an energy capacity of the secondary energy store of around between 2% to 3% of the energy capacity of the primary energy store. Such optimized energy capacity is key for a practical and commercial application of compact personal flying machines.

In some examples, the primary energy store is sized and configured to store a value X of energy, while the secondary energy store is sized and configured to store a value of between around 0.02X and 0.03X of energy. The first or second energy stores may be either or any of: a fuel tank, a canister, a battery, a battery cell, a kinetic energy storage device, a capacitor or a supercapacitor. In some examples, the primary energy store is a fuel tank for carrying a combustible fuel for an engine. In some examples, the secondary energy store is a store of energy for electrical output to a motor, such as a battery and/or a capacitor. In some examples the secondary energy store is a kinetic energy storage device.

Advantageously, the secondary energy store may be recharged by operation of the primary drive source130, either during powered flight by the primary drive source130, or by running the primary drive source130on the ground prior to take-off.

An alternative example of a secondary energy store which may be used in a device is a kinetic energy storage device. Such devices generally comprise a high speed flywheel, which is spun up to speed in order to store kinetic energy, and then when that kinetic energy is required for use, the flywheel is mechanically connected to an output of the device, commonly a rotatable output shaft, to provide kinetic energy. Therefore, the secondary drive source140may be a kinetic energy storage device and it may be used in the manner described above for the different flight modes of the device100, in place of an electrical secondary drive source. Such a kinetic energy storage system can have an advantage over electrical systems, since the overall weight of the kinetic energy storage and recovery system can be lower than an electrical system, which requires electromagnetic devices and electric energy storage devices, such as motors, magnets, batteries and/or supercapacitors.

The device may also be provided with either fixed or deployable wings181/182which are configured to permit substantially horizontal winged flight of the device. This can provide increased lift so that the fan110can be used primarily for forward thrust, with lift being provided by the one or more wings181/182. This is described in more detail in connection with the following figures.

The user2can be attached to the device via a harness3which may comprise upper30and lower31straps to retain the user to a user position32. Padding may be provided between the user2and the device to reduce the transmission of vibration to the user during operation. The user2may be allowed to stand on a platform40and a stand41may help to retain the device in an upright position when on the ground. One or more dampers198and198can be provided to help to absorb shocks upon landing, in particular in the case of harsh landings. A leg strap42may also be provided to restrain the legs of the user during use.

In addition to wings181and182, elevators191and194aprovide extra lift and a rudder195aand/or fin195bmay be provided to assist with stability during winged flight and/or steerage during winged flight. The structure comprising the elevators191and194, the rudder195band the connecting plates196/199and197may also provide a double function as a part of a stand on which the device can stand when in its upright position on the ground.

Connecting plate196is mounted at or toward a far end of the fixed stabiliser194b, to which the movable elevator section194ais attached, such that the movable section194acan pivot as shown by arrow194c. A second connecting plate199is mounted at or toward an opposite end of the horizontal stabilizer, as can be seen inFIG.2. A vertical stabiliser has a fixed section195band a movable section195awhich can act as a rudder by pivoting as indicated by arrow195c.

FIG.2illustrates a cross-sectional front view of the device with the wings181and182in a deployed position. As can be seen in the Figure, the primary ducting150splits into first and second exhaust ducts151and152. The exhaust ducts151and152may be rotatable around rotatable mounts153and154to allow steerage of the device during flight, by directing thrust from the separate exhaust ducts. The rotatable mounts153and154may be universal joints to allow adjustment of the orientation of the exhaust ducts in substantially any direction relative to the fan110. The flow from the fan110is therefore split into a plurality of exhaust ducts to provide a plurality of directable thrust sources. The exhaust ducts may be provided with a chevron form11, which can reduce noise generated. One example of a primary drive source130is illustrated in the form of a two cylinder engine having an engine block133and first and second pistons132aand132b. The engine is provided with an air inlet139which feeds air into the inlet port138of the engine. The inlet139can be provided in one or more of the primary duct150or the first and/or second exhaust ducts151and152of the fan arrangement. Another component which can be located in the ducts and more generally in the thrust path of the fan is a cooling device90for the engine130. Cooling fluid may be delivered to and from the cooling device90by fluid conduits91and92in order to cool the engine. One or more exhaust outlets134and135may be provided to deliver exhaust gases to a muffler136and on to an exhaust pipe137. The engine may be provided with an electric turbocharger and/or an electric supercharger to provide additional boost to the engine. An electric turbo charger can take thrust from the exhaust of the engine and use a turbine193and suitably connected generator to convert this to electrical power to be delivered to the battery. An electric supercharger can take electric power from the battery and convert it to mechanical output with a motor, for providing power to the compressor192. In some arrangements it is possible for the electric compressor192to take power from the generator/turbine193directly.

It is also possible to provide a further additional thrust device to the VTOL device100. This can be provided in the form of one or more secondary thrust sources10which may be provided anywhere on the device in order to aim their thrust in a generally downward direction during flight. In the illustrated example, they are located on the first and second exhaust ducts151and152. The devices10can be provided in the form of emergency rockets, for example solid state rockets. These may be fired in the event of the failure of one or more of the primary and secondary drive sources130and140. Therefore, it is possible to provide the device with one or more back-up drive sources to provide drive to the fan or alternative thrust sources to provide an alternative or back-up in the event of failure of the primary drive source, or simply as an alternative thrust source to the fan110. The thrust available in the secondary thrust devices is preferably sufficient to allow safe descent of the device in the event of engine failure. This can be calculated depending on the weight of the device and its payload and the desired permissible downward speed and/or downward acceleration.

FIG.2also illustrates the wings181and182of the device in a deployed position. Although they may be deployable between the position shown inFIG.2and the stowed position ofFIG.1, where they are substantially aligned with the primary axis X of the device, the wings may be provided in a fixed and permanent configuration as illustrated inFIG.2. As can be seen, each wing has a leading edge183,184, and a trailing edge185,186and a tip187,188. As will be appreciated, when the device is propelled in a forward direction, i.e. that of the leading edges183and184, the wing can be suitably configured to provide lift to the device and so the device can be flown in winged flight. Using the drive or thrust sources to provide forward thrust to the winged device during extended flight can result in overall efficiency increases and therefore extended range of the VTOL device during use, since the “hovering” mode flight is significantly less efficient than winged flight.

Referring to both toFIGS.1and2, the control of the device by the user will now be briefly described. The user2can grasp manual control inputs170. Manual control inputs170can be directly connected to the exhaust ducts151and152to effect direct mechanical control. However, other forms of control input can be envisaged. Any suitable interface to receive user inputs, either by remote control or by on-board control of the device can be envisaged to provide control inputs to the device100. The main controls are the level of thrust generated by the fan110, angles of each of the exhaust ducts151and152, deployment or stowage of the wings181,182and the selection of a drive or thrust source from the primary or secondary drive sources or thrusters10. In the illustrated example, manual input devices171and172are illustrated and can be gripped by the user's hands. The user can provide input to set a direction of thrust of the exhaust vents151and152to control and steer the device in flight. This generally controls the rotation of the exhaust ducts around their rotatable connections153and154. Other inputs, either visual, verbal or mental could be envisaged by other input devices, such as voice recognition commands interpreted by a suitable controller, touch screen input, movement sensors or any other form of input device which can deliver control signals from a user to a controller. Many are in development, including mind control based upon detecting brain waves, and could be implemented to control flight of the device. Similarly, one or more input devices can be provided to receive a thrust level input from a user to control the level of thrust required to drive the device. Alternatively, the user may simply input coordinates of a destination and a controller may be provided which calculates a vertical and horizontal trajectory and then controls the device automatically to achieve a suitable altitude, transition to winged flight if necessary, and then transition to vertical flight once more for landing at the chosen destination. As will be appreciated, in such instances, the user2may simply be a passenger and may not have any control over the device100, or may simply have emergency control in the event of anything going wrong with the automated flight systems. Inputs may be provided to allow the user to select one of the primary and/or secondary drive sources for the fan110. However, the selection of those drive sources may alternatively be automatically carried out by a controller provided either in the device100, or remotely from the device in an automated or manual controller which simply transmits control signals to the device. Similarly, activation of the emergency thrusters10may be manually controlled or automatically controlled from a remotely or locally located controller.

FIGS.3A to3Dillustrate some possible modes of operation of the device100. The sequence of figures generally illustrates how the device can be used from take-off through to winged flight. InFIG.3A, the device100is operated with the exhaust ducts151directed in a generally downward position and aligned with the primary axis X of the device100. The user2can increase the thrust until such time as sufficient lift is provided to lift the user and device from the ground. Varying proportions of power can be provided from the primary and secondary drive sources. Take-off can be 100% from the primary power source, but this can be noisy. It can therefore be preferred to have a proportion, of between around 30% to around 70% or more of the drive power coming from the secondary drive source, while a remainder comes from the primary drive source. This balance can then be shifted toward a greater proportion of the power coming from the primary drive source as the device gains height, and/or gains speed after lift-off.

Effecting take-off and landing with, for example 50%-60% power using an electric generator allows the combustion engine to be run at only 50%-40% power at these times. This can allow a much lower net fuel consumption as the engine can be run in its more efficient revolutionary speed range. The device can be configured to enable recharging of secondary energy store, such as a battery, slowly with the engine during horizontal flight at around 50% power as well, making the charging possible at the most efficient engine speed as well. Also, the engine not running at 100% improves greatly the TBO, since the stress effect on the engine is not linear with the engine power but goes almost with the square of it, thus significantly increasing the need for more regular maintenance.

In order to transition to winged flight, as shown inFIG.3D, the user can control the exhaust ducts151and152to begin to propel the user2and the device100in a forward direction as inFIG.3B, preferably with the wings still closed. As forward speed increases, first drag and then lift in the direction of arrow300generated by the elevators191and194will increase providing angular momentum for the rotation of the machine from the hovering flying mode to the winged flying mode. The deployable wings181and182can be gradually opened as forward motion and angular rotation increases, as shown inFIG.3C, until the device arrives at the fully winged flying mode depicted inFIG.3D. Depending on the weight distribution and the detailed position of the wings, the deployable wings could be opened in the hovering condition, prior to transition to winged flight.

To increase the forward speed, the user can push the ducts toward the rear of the device, as shown inFIGS.3B,3C &3D, and as increasing forward speed increases lift generated by the wing or wings181and elevators194, then the exhaust nozzles151and152can be increasingly orientated towards the front-to-rear axis of the device and then aligned to the device in the horizontal winged flight mode, to further increase the forward speed and generate further lift as necessary from the wing or wings181. This efficient winged flight can be used for the majority of a journey between locations to provide increased range. During winged flight, control surfaces on any or all of the wings, tail or tailfin may be used to control the flight of the device. In some examples, the main wings187and188may have no control surfaces and may be substantially fixed. Control surfaces may be provided on elevators194and a rudder195of the device and/or on a tail wing or wings provided additionally to the main wings187and188. Any or all of the control surfaces may be operated by a user via control pedals, which may be provided in the structure40. The pedals may be provided in the structure40on which the user stands in the upright position of the device.

As will be appreciated on understanding the steps carried out inFIGS.3A to3D, the return to vertical flight for a vertical landing is essentially the reverse of the sequence shown inFIGS.3A to3D. The user or controller directs the device into a vertical orientation by pointing the head or front end of the device upward with a gradual downward orientation of the exhaust ducts151and152. Once vertically oriented to a sufficient degree that the weight of the device is entirely balanced by the thrust of the fan110, the user or controller can begin to reduce the thrust to effect a descent.

A further measure which can be incorporated into the emergency features of the device is the detachment of one or more components of the device in the event of a power failure, in order to slow the descent of the device. If one or the other of the drive sources fails, one or more components of the drive source or its energy store may be jettisoned, such as the drive source itself, components of the drive source, or the corresponding energy store. In some examples, where there is a failure in the primary drive source, one or more of the primary drive source, its corresponding primary energy store, and/or a payload carried by the device may be jettisoned to slow a descent of the device in such a failure mode.

Although particular arrangements have been discussed and described in relation to the enclosed figures, it will be appreciated that the various features can be combined in different combinations from those described above whilst still realising the benefits of the invention.