Patent Description:
Current advances in aircraft technologies have facilitated propulsion systems with greater efficiency. Further, with the introduction of stronger and lighter materials, additive manufacturing process, computer controlled systems, the use of electric power sources and other alternative energy sources further advances have enabled the development of Vertical Take-Off and Landing (VTOL)/Short take-off and Landing (STOL) vehicles for usage not only for military purposes but also for commercial purposes.

Most of these VTOL and STOL systems today employ a vectored thrust mechanism to provide vertical flight capability. This is achieved by designing the propulsion system in multiple ways. However, these propulsion systems typically require rotating or tilting the entire vehicle and/or engines and/or propellors, thereby necessitating complex structures and mechanisms.

The cross-flow fan (CFF) or tangential fan, developed in <NUM> by Mortier is used extensively in the heating, ventilating and air conditioning (HVAC) industry. The fan is usually long relative to the diameter, so the flow approximately remains <NUM>-dimensional (2D) along the length of the fan. The CFF uses an impeller with forward curved blades, placed in a housing consisting of a rear wall and vortex wall. Unlike radial machines, the main flow travels transversely across the impeller, passing the blading twice.

<FIG> illustrates a prior art system that shows a section view of a typical HVAC configuration. For efficient forward flight of an airborne craft, the propulsor must ingest and expel the flow at a small angle to the forward flight direction. The conventional HVAC-type CFF housing, characterized by approximately a <NUM> degree turn from inlet to outlet, is not well suited for this application.

The popularity of the CFF comes from its ability to handle flow distortion and provide high pressure coefficient. Effectively a rectangular fan, the diameter readily scales to fit the available space, and the length is adjustable to meet flow rate requirements for the particular application. Since the flow both enters and exits the impeller radially, the cross-flow fan is well suited for aircraft applications particularly where a spanwise trailing edge air jet is desirable for distributed propulsion. Due to the 2D nature of the flow the fan readily integrates into an airfoil for use in both thrust production and vectoring and boundary layer control.

In addition to increased propulsive efficiency, embedded propulsion provides reduced noise and increased safety, since the propulsor is now buried within the structure of the aircraft (e.g. no exposed propellers). Also, by eliminating the engine pylon/nacelle support structure, the aircraft parasitic drag can be reduced by up to <NUM> to <NUM>%, thus improving cruise efficiency and range.

Attempts to provide a cross-flow fan in aircraft wings have been largely unsuccessful. For example, some system designs use cross-flow fans embedded within the middle of a conventional airplane wing. Other system designs distribute fully embedded cross-flow fans near the trailing edge of a conventional transport aircraft, with shafts and couplings connecting them to wing-tip and root-mounted gas turbines. Air is ducted into the fan from both wing surfaces and expelled out at the trailing edge. These system designs, however, limit the fan size and ducting. Also, the CFF may not be a viable option for high-speed applications due to compressibility effects (i.e. choking). These configurations fall short of expectations due to poor fan placement and poor housing design. These deficiencies result in low fan performance, reduced circulation control and low thrust production.

Some attempts have also been made to vary the geometry of the CFF exit region to vector the exit flow through relatively small angles for flight at high angles of attack and/or pitch control in forward flight during STOL flight for example. However, efficient VTOL flight using the same fan and exit ducting has not been contemplated due to the difficulty of achieving an aerodynamically efficient geometry for both applications.

In particular in the prior art, Kummer and Dang et al disclose changes to the various surfaces of a flap that is mounted aft of a crossflow fan to assist in Short Take Off and Landing (STOL) and stall characteristics at high angles of attack. In particular, <CIT> discloses an inlet face that rotates about its leading edge and also discloses a lower flap face that is distorted about its leading edge and a fan rear face that will vary the clearance from the rotor.

It is noted that this may be applicable to VTOL operation. However, this form of VTOL, where the craft occupants must take-off and land while facing skyward, with the ground semi-visible behind them is generally judged as unacceptable. <CIT> later discloses adding axial fans to a craft with a crossflow fan to avoid this issue and to provide further thrust directed downward to achieve effective VTOL operation albeit with the added complexity and weight.

Many VTOL craft which transport personnel are therefore arranged so that the fuselage remains roughly horizontal and the thrust for propulsion and VTOL is vectored by rotating the propulsive elements on a wing or a rotor and motor pod for example. Another popular alternative is to provide separate rotors for vertical flight and horizontal flight (Aurora etc.). This design has the further advantage that the thrust required for VTOL is many times greater than that required for horizontal flight and this can provide significant improvements in both forward flight propulsive efficiency and lifting efficiency. However, this adds to the cost and complexity of the system. <CIT>, <CIT>, <CIT>, <CIT> disclose other aircraft with cross-flow fans.

Therefore, there is a need for an improved and advanced propulsion system with a vector thrust mechanism. Moreover, there is a need for a propulsion system of modular design provided with vector thrust mechanisms for imparting VTOL/STOL capabilities to a vehicle with better efficiency and reduced complexity.

The present invention provides a system for lift, propulsion and control for an aircraft vehicle to facilitate Vertical take-off and landing (VTOL)/Short takeoff and landing (STOL) operations as per claim <NUM>.

The exit duct is further configured to eject a longitudinal jet of air, when in use, required for producing the vertical lift in combination with a predefined fan speed of the cross flow fan and position of the flexlip and the flap. In an example, the predefined speed may be a suitable speed of the fan to produce the longitudinal jet of air required for the vertical lift of the aircraft.

In an embodiment, the flap and the flexlip are connected and moved through an angle so that the thrust can be vectored through an angle of more than <NUM> degrees.

In an embodiment, the present invention provides the exit duct as described wherein the flap and flexlip are connected and actuated or moved through an angle so that the thrust can be vectored through an angle of more than <NUM> degrees.

In an embodiment, the present invention provides the exit duct as described wherein a change in the actuated angles of the flap and lip produce a change in the magnitude and/or direction of said thrust the change being used to control the attitude of the aircraft.

In an embodiment, the present invention provides the exit duct as described wherein the inner edge of the upper face of the flap consequentially rotates to increase the inlet flow area to the rotor such that, when combined with increased rotor speed, increased mass flow is available from the fan when the flap is rotated to the position to produce vertical thrust for VTOL operation.

In an embodiment, the present invention provides an airfoil, embedded cross-flow fan and exit duct element with distributed flow that has low parasitic drag in forward flight.

In an embodiment, the present invention provides an airfoil, embedded cross-flow fan and exit duct element with distributed flow wherein the airfoil has a thickness to chord ratio greater than <NUM>% and any flow separation is limited by boundary layer ingestion into the crossflow fan.

In an embodiment, the present invention provides an airfoil, embedded cross-flow fan and exit duct element wherein the rotor speed of the cross-flow fan is independent of any other fans on the craft and the speed is varied relative to the other fans to assist in controlling the attitude and flight direction of the aircraft.

In an embodiment, the present invention provides an airfoil, embedded cross-flow fan and exit duct element wherein the crossflow fan has a rotor diameter between <NUM>% to <NUM>% and more specifically in the ranges of <NUM>% to <NUM>% of the chord of the airfoil.

In an embodiment, the present invention provides an airfoil, embedded cross-flow fan and exit duct element wherein the airfoil has an upper surface radius that is between the ranges of <NUM>% to <NUM>%. In an example, the range may be configured to be <NUM> and <NUM>% of chord and extending over more than one third of the upper surface, a lower surface that is substantially flat and extends over more than one third of the lower surface and a rear surface that forms the rear wall of the embedded crossflow fan.

In an embodiment, the present invention provides an airfoil, embedded cross-flow fan and exit duct element that facilitates parasitic drag in forward flight that decreases with increasing angle of attack up to a maximum of between <NUM> and <NUM> degrees. In another embodiment, the angle of attack may be varied outside the ranges of <NUM> to <NUM> degrees.

In an embodiment, the present invention provides an airfoil, embedded cross-flow fan and exit duct element wherein the cross-flow fan ingests the boundary layer the airfoil and thereby facilitates stall free operation at angles of attack between <NUM> and <NUM> degrees. In another embodiment, the angle of attack may be varied outside the ranges of <NUM> to <NUM> degrees.

In an embodiment, the present invention provides an airfoil, embedded cross-flow fan and exit duct element wherein the exit duct can be configured to deflect the jet from the trailing edge of the element through an angle of between <NUM> and <NUM> degrees from the jet direction for optimal forward flight.

The drawings herein are appended to facilitate the understanding of the invention.

The drawings show embodiments of the invention and do not intend to limit the invention. The drawings will now be described by way of example only, where:.

In the detailed description, different alternatives will be discussed in more detail with reference to the appended drawings. It should be understood, however, that the drawings are not intended to limit the scope of the invention to the subject-matter depicted in the drawings.

In the exemplary embodiments, various features and details are shown in combination. The fact that several features are described with reference to a particular example should not be construed as implying that those features as a necessity have to be included together in all the embodiments of the invention. Conversely, features that are described with reference to different embodiments should not be construed as mutually exclusive. As those skilled in the art will readily understand, embodiments that incorporate any subset of features described herein and that are not expressly interdependent have been contemplated by the inventor and are part of the intended disclosure. However, explicit descriptions of all such embodiments would not contribute to the understanding of the principles of the invention, and consequently some permutations have been omitted for the sake of simplicity.

In an embodiment, some terminologies such as 'airborne craft and aircraft' are used alternatingly throughout the description and do not intent to limit the scope of the invention.

<FIG> is illustrating a prior art cross-flow fan. The CFF is provided with an inlet and an outlet, padding region, a rear wall and vortex wall. A first stage and a second stage to manage the through flow through the CFF. As indicated earlier, <FIG> shows a sectional view of a Heating, Ventilating and Air Conditioning (HVAC) configuration of the cross-flow fan. For efficient forward flight of an airborne craft, the propulsor must ingest and expel the flow at a small angle to the forward flight direction. The conventional HVAC-type CFF housing, characterized by approximately a <NUM> degree turn from inlet to outlet, is not well suited for this application.

<FIG> is an illustration of a baseline inline housing according to an embodiment of the present invention. The crossflow fan (CFF) assembly <NUM> consisting of a rotor <NUM>, a rear wall <NUM> and a vortex wall <NUM>. The through flow achieved is illustrated by <NUM>.

<FIG> illustrates a diagram of a lift, propulsion and control system showing the exit duct geometry of the flap and flexlip when configured for forward flight. As shown in <FIG> there is seen an airfoil <NUM>, a flexlip <NUM> attached to and forming part of airfoil <NUM>, a crossflow fan rotor <NUM>, a flap <NUM> rotatable and mounted about the axis of the rotor <NUM> and an exit duct <NUM> from the crossflow fan rotor <NUM> and formed by the lower face <NUM> of flap <NUM> and the upper face <NUM> of flexlip <NUM>. The position of the flexlip <NUM> and flap <NUM> are as shown in <FIG>. With the flexlip <NUM> and flap <NUM> configured in this position and with a suitable fan speed, a longitudinal jet of air from duct <NUM> is ejected from the length of the lift, propulsion and control system to achieve distributed propulsion, and desirably the forward flight propulsive efficiency benefits. Synergistically, the edge <NUM> of face <NUM> of the flap <NUM> restricts the inlet area to the crossflow fan to provide an optimal flow rate through the fan for best propulsive efficiency.

<FIG> is an illustration of a lift, propulsion and control system showing the exit duct geometry of the flap and flexlip when configured for VTOL operation. In the VTOL configuration as shown in <FIG> the flexlip <NUM> and the flap <NUM> are moved to different position as compared to <FIG>. Shown is an airfoil <NUM>, a flexlip <NUM> attached to and forming part of airfoil <NUM>, a crossflow fan rotor <NUM>, a flap <NUM> rotatable and mounted about the axis of rotor <NUM> and an exit duct <NUM> from the crossflow fan rotor <NUM> and formed by the lower face <NUM> of flap <NUM> and the upper face <NUM> of flexlip <NUM>. With the flexlip <NUM> and flap <NUM> configured in this position, ie. with the flexlip and flap rotated with respect to <FIG>, and with a suitable fan speed, a longitudinal jet of air from duct <NUM> is ejected from the length of the lift, propulsion and control system to achieve a substantially vertical jet thereby producing upward thrust or vertical lift for VTOL operation. Synergistically, the edge <NUM> of face <NUM> moves to create a much larger inlet area to the crossflow fan thereby providing an optimal flow rate through the fan for vertical thrust.

<FIG> illustrates a cross section of an airfoil, embedded crossflow fan and exit duct geometry according to the present invention showing the range of movement of the flap and flexlip. Referring now to <FIG>, there is seen an airfoil <NUM> with an upper surface radius <NUM> and an angle of attack <NUM> to the airstream direction <NUM> and a crossflow fan assembly consisting of a rotor <NUM>, a rear wall <NUM> and a vortex wall <NUM>, a rear flexlip24 which flexes through an angle <NUM> and has an upper face <NUM>, a flap <NUM> that rotates about the rotor axis <NUM>, can rotate through an angle <NUM> and has a lower face <NUM>, an exit duct <NUM> formed by upper face <NUM> of the flexlip and lower face <NUM> of the flap. The angle <NUM> can be configured to be different from the angle <NUM>. In an embodiment, according to the invention, the angle of attack <NUM> is set achieve a maximum lift to drag ratio in conjunction with the exit angle of the duct jet. Further, the area ratio of the fan inlet area to fan exit area may be configured to be optimized by the movement of flap <NUM> for both high propulsive efficiency in the upper position and high vertical thrust in the lower position.

Furthermore, despite relatively low fan efficiency, the present invention is competitive with conventional propulsion technologies. The raised inlet formed by flap <NUM> eliminates the fan size restriction created if the fan is fully embedded within the airfoil <NUM>. Also, cross-flow fan performance is quite insensitive to even large amounts of wake ingestion, making it ideal for this type of configuration. The fan of the present invention is capable of drawing in the boundary layer, regardless of its thickness.

Referring to the thick airfoil <NUM> seen in <FIG>, <FIG> and <FIG>, even for a low angle of attack <NUM>, the wake can be quite large, producing large pressure drag. This renders very thick wing sections impractical for most aircraft applications as the drag penalty outweighs any benefits gained in lift or interior volume. With-out the suction effect of a rear-mounted crossflow fan rotor <NUM>, the flow separates even at only a small angle of attack. The embedded cross-flow fan near the trailing edge eliminate flow separation by drawing the flow back toward the surface and into the fan ducting, yielding very high lift coefficients. This is turn results in low in-flight aircraft stall speed without the use of additional high lift devices, such as slotted flaps and leading edge slats but more importantly, facilitates small short high lift wings that can be readily configured into lifting elements described herein for compact airborne craft.

In forward flight, the distributed propulsion generated by the long spanwise jet of air from duct <NUM> gives rise to the phenomenon known as distributed propulsion which can be used to generate a very high propulsive efficiency in forward flight. This, together with the lower drag resulting from the absence of engine nacelle, pylon, and interference drag offsets any low fan efficiency.

By vectoring the thrust using co-ordinated control of the flap <NUM> and flexlip <NUM>, consequentially opening the inlet to the crossflow fan and increasing fan speed, additional lifting force sufficient to achieve VTOL is possible. This configuration is illustrated in <FIG>. and <FIG> and in <FIG>. where the wide range of authority of the flexlip and flap are shown.

In an embodiment, it is determined that a more ideal Lift, Propulsion and Control Element for a VTOL aircraft with a crossflow fan would desirably vector the flow from a substantially horizontal direction to a substantially vertical direction but would also provide for efficient increased thrust during VTOL because the thrust required for VTOL operation is significantly more than that required for forward propulsion. This additional thrust can be achieved by increasing rotor speed, but this decrease lifting efficiency or power loading. To offset this loss of efficiency fan area is increased.

The embodiments described in <FIG> and <FIG> achieve a system wherein the flap is rotated about the rotor axis in such a way that the ratio of inlet to exit area of the fan is varied synergistically with the redirecting of the exit duct air jet. In a first position, a flexing or morphing lip coordinates with a flap to provide both a desirable exit flow vector for forward flight propulsive efficiency and a desirable area ratio across the fan, the flap and lip then moved to a second position provide sufficient change in the area ratio across the fan and redirection of the exit flow vector to provide effective VTOL operation. The effective VTOL operation allows the wing element and attached fuselage and passengers to remain substantially horizontal during take-off, landing and transition to cruise flight.

<FIG> is a diagram illustrating the flow around and through the wing and crossflow fan element when configured for VTOL, according to the present invention. The variation in the position of the flap and the flexlip can be observed to achieve the required VTOL.

<FIG> is a diagram illustrating the flow around and through the wing and crossflow fan element when configured for horizontal forward flight, according to the present invention. The variation in the position of the flap and flexlip for horizontal forward flight to achieve the required thrust is observed in <FIG> are different from the previous <FIG>.

Claim 1:
A system for providing lift, propulsion, and control for Vertical take-off and landing (VTOL)/Short take-off and landing (STOL) operations of an aircraft vehicle , the system comprising:
a. at least one airfoil (<NUM>) extending from a leading edge to a trailing edge;
b. a cross-flow fan rotor (<NUM>), having a rotation axis, at least partially embedded in the airfoil (<NUM>) and substantially the same length as the airfoil and mounted adjacent to the trailing edge of the airfoil; and
c. an exit duct (<NUM>) for the cross-flow fan configured to provide distributed flow along the trailing edge of the airfoil and configured to provide vectored thrust; and the system further comprises:
d. a flap (<NUM>) arranged rotatable about the cross-flow fan rotation axis (<NUM>), where the flap has an upper face (<NUM>) and a lower face (<NUM>), and
characterized in that the airfoil (<NUM>) includes a flexlip (<NUM>), with an upper face (<NUM>) wherein the lower face (<NUM>) of the flap and the upper face (<NUM>) of the flexlip (<NUM>) form the exit duct (<NUM>); wherein the flap (<NUM>) and the flexlip (<NUM>) forming the exit duct (<NUM>) are further configured to move simultaneously but at different angular rate to deliver a desired change in both the angle and mass flow of the vectored thrust.