High speed vertical take-off and land aircraft with active fan balancing system

A high-speed vertical take-off and land aircraft includes a body with an engine supported by the body. A fan assembly is also carried by the body. The fan assembly includes a hub and a plurality of blades to provide vertical lift for the aircraft. A nozzle ring is provided on the fan assembly. The nozzle ring includes an annular nozzle array. Hot gases from the engine are fed to the nozzle array by a feed duct. A bearing mechanism supports the fan assembly on the body. The bearing mechanism is carried in a work space. A brush seal assembly thermally isolates the work space from the hot exhaust gases passing through the feed duct to the nozzle array.

TECHNICAL FIELD

The present invention relates generally to aircraft and, more particularly, to an aircraft with improved features for enhanced vertical take-off and landing (VTOL) capabilities and high speed (HS) horizontal flight.

BACKGROUND OF THE INVENTION

U.S. Pat. No. 6,382,560 to Ow discloses a high speed vertical take-off and land (HSVTOL) aircraft. The aircraft includes a disk-shaped fuselage with a rotatable fan assembly having a nozzle ring driven by hot jet gases and/or cool fan air from jet engines. High efficiency air bearings serve to support the rotatable fan assembly on the fuselage in the vertical direction and rollers around the perimeter provide horizontal support and stability. The present invention relates to an improvement of this basic design by incorporating an active system for sensing vibration and balancing the fan assembly as it is rotated.

SUMMARY OF THE INVENTION

In accordance with the purposes of the present invention, an improved HSVTOL aircraft is provided. The aircraft includes a body or fuselage. An engine is supported on that body. In addition, the body carries a fan assembly. The fan assembly includes a hub and a plurality of blades to provide vertical lift off for the aircraft.

A nozzle ring on the fan assembly provides an annular nozzle array for ejecting hot exhaust gases from the engine. A feed duct receives the hot exhaust gases from the engine and directs those gases to the annular nozzle array. An interface is formed between the feed duct and the annular nozzle array. The hot exhaust gases pass through this interface and have a pressure P1. In addition, a bearing mechanism vertically supports and horizontally centers the fan assembly on the body. The bearing mechanism is carried in a work space defined between the body and the fan assembly. Still further, a brush seal assembly thermally isolates the work space from the hot exhaust gases moving through the feed duct and the annular nozzle array.

More specifically, the brush seal assembly includes (a) a brush seal positioned across an entry to the work space, (b) a brush seal manifold provided between the brush seal and the interface and (c) an air source. The air source provides pressurized air to the brush seal manifold. The pressurized air is provided at a pressure P2that is equal to or greater than the pressure P1of the hot exhaust gases at the interface. The pressurized air in the manifold essentially provides a curtain of relatively cool air between the brush seal and the hot exhaust gases whereby the work space is thermally isolated from the hot exhaust gases.

Further describing the invention, the brush seal manifold is open to the interface between the annular nozzle array and the feed duct. In addition, the brush seal assembly includes a pressure sensor that senses the pressure of the exhaust gases in one of the annular nozzle array, feed duct or interface.

Still further, the brush seal assembly includes a controller responsive to the pressure sensor. The controller is connected to the air source. The controller adjusts the pressure of the pressurized air in the brush seal manifold in order to maintain the air curtain and a desired temperature in the work space. The brush seal and the brush seal manifold may both be annular in shape and extend around the body.

In accordance with an additional aspect of the present invention a brush seal assembly is provided for thermally isolating a first space from hot gases in a second space having a pressure P1. The assembly comprises a brush seal positioned across an entry to the first space, a brush seal manifold provided between the brush seal and the second space and an air source providing pressurized air to the brush seal manifold at a pressure P2where P2is equal to or greater than P1. The pressurized air effectively forms a curtain of relatively cool air between the brush seal and the hot gases whereby the first space is thermally isolated from the hot gases.

Further describing this invention, the brush seal manifold is open to the second space. In addition, the brush seal assembly includes a pressure sensor that senses the pressure of the hot gases in the second space. Further, the brush seal assembly includes a controller responsive to the pressure sensor. The controller is connected to the air source and adjusts the pressure P2of the pressurized air in the brush seal manifold in order to maintain an effective air curtain and the desired temperature in the first space.

In accordance with yet another aspect of the present invention a method is provided for thermally isolating a first space from hot gases in a second space. The method comprises the steps of providing a brush seal between the first space and the second space, providing a brush seal manifold between the brush seal and the second space and delivering pressurized air to the brush seal manifold at a pressure necessary to form an air curtain between the first space and the second space. The method further includes the step of sensing pressure in the second space and adjusting the pressure of the pressurized air in the brush seal manifold in order to maintain the air curtain and a desired operating temperature in the first space. Still further, the method may include the step of adjusting the temperature of the pressurized air delivered to the brush seal manifold by the air source.

In the following description there is shown and described a preferred embodiment of the invention, simply by way of illustration of one of the modes best suited to carry out the invention. As it will be realized, the invention is capable of other different embodiments, and its several details are capable of modification in various, obvious aspects all without departing from the invention. Accordingly, the drawings and descriptions will be regarded as illustrative in nature and not as restrictive.

Reference will now be made in detail to the present preferred embodiment of the invention, an example of which is illustrated in the accompanying drawings.

DETAILED DESCRIPTION OF THE INVENTION

Reference is now made toFIG. 1illustrating the HSVTOL aircraft10of the present invention. The aircraft10is similar in design to that disclosed in my prior U.S. Pat. No. 6,382,560, the full disclosure of which is incorporated herein by reference. The center of the aircraft10is formed by a disk-shaped fuselage or body, generally designated by reference numeral12. An outer fan assembly14surrounds the fuselage12and includes an inboard nozzle ring16with the perimeter being defined by a full periphery rim or shroud18. The interface between the fuselage12and the nozzle ring16is provided with a rotary bearing and seal arrangement that allows the fan assembly14to freely rotate with respect to the fuselage12. As described, the rotary motion is in the clockwise direction, and is generally represented by the action arrow R inFIG. 1. A pod mounted fan jet engine20extends along the horizontal axis of the aircraft10behind the pilot canopy C. Two additional fan jet engines22and24are viewed in dashed line form since in this preferred embodiment these two engines are submerged within the fuselage12.

As made clear in my previous U.S. Pat. No. 6,382,560, pilotless operation is made possible by an onboard CPU controller that operates the engines20,22,24as well as all of the other flight components of the aircraft10. In a piloted craft, a control stick or similar manual or automatic interface is employed by the pilot to fly the aircraft10through the controller. Flight attitude transducers can also be provided to provide input. Further, the onboard CPU controller, GPS and radio systems enable optimal unmanned autonomous operation.

The exhaust from the fan jet engines20,22,24is fed to an array of nozzles25that are arrayed around the full periphery of the nozzle ring16through an annular, feed duct26(see alsoFIG. 2). As the gases are discharged from the nozzles25, the fan assembly14is rotated with respect to the fuselage12to provide vertical lift (see action arrow L). The fan assembly14provides a vertical fan thrust augmentation factor that multiplies the propulsion thrust that drives the fan by a factor of approximately 2.5. The fan thrust augmentation factor enables vertical takeoff of the HSVTOL with significant fuel and payload fractions which in turn enables extremely high VTOL performance.

More specifically describing the invention, the nozzle ring16is the component of the fan assembly14that is mated with the outer periphery of the fuselage12. Each of the nozzles25are held in a separate segment of the nozzle ring16. Between the nozzle ring16and the feed duct or plenum26is a transition zone through which the exhaust is transferred to the nozzle ring16. A peripheral series of nozzle intake receptors28are formed on the inboard face of the nozzles25. The receptors28extend through ceramic spacers29and are surrounded by a sleeve of thermal insulation31. The feed duct26includes a plurality of matching feed orifices30positioned peripherally around the fuselage12. The orifices30extend through the structural ring85of the body12and the ceramic spacers33. Each of the interacting orifices30and the rapidly moving receptors28function to efficiently transfer the supply of jet separated exhaust core gases and fan air through an interface106.

The exhaust from the nozzles25extends down at an approximately 15° angle and is ejected at high speed at this optimal angle through a restricted nozzle orifice. The nozzle ring16being inboard of the fan assembly14provides the appropriate spin action to the fan assembly without interference with the individual fan blades32. After transitioning from vertical to horizontal flight, the exhaust from the fan jet engine20is gradually redirected through extension ducting and out of the tailpipe20a. Similarly, the engines22and24have tailpipes22a,24afor horizontal cruise propulsion. The redirection of flow from these engines22,24takes place directly through the section of the duct or plenum26extending along the aft quadrants of the aircraft.

The fan assembly14comprises a selected number of individual fan blades32illustrated rotating in the clockwise direction as noted by action arrow R inFIGS. 1 and 3. These blades32extend upwardly at a selected angle of attack designed to provide optimum performance.

As illustrated schematically inFIG. 3, the plurality of fan blades32are mounted to or carried by a structural ring or fan hub34. A first bearings mechanism35serves to support the fan assembly14on the fuselage12in the vertical direction (seeFIGS. 2 and 2a). The bearings mechanism35includes a series of opposed air cushion modules36radially arrayed around the body12and forming an annular tract for vertical support by engagement along the top and bottom of a portion of the fan hub34that forms an annular support race38of the fan assembly14. Each module36is mounted to a first end of a beam82through a gimbel46that allows free floating action. Each beam82is pivotally mounted on a support bracket84that is fixed to the outer structural ring on hub85of the fuselage12. A second opposite end of the beam82is connected to a hydraulic adjuster86. The hydraulic adjuster86functions to set the height of the associated module36so that the desired gap is provided between the module36and the support race38to allow the bearings mechanism35to operate efficiently and effectively. This process is automated so that the bearing modules36are all properly set prior to fan operation. Each of the modules36includes a pressurized air inlet40. During fan operation, a thin air gap42allows controlled escape of the pressurized air around the periphery of the module36, thus providing an air cushion support between the module36and the adjacent support race38.

A second bearings mechanism37(seeFIGS. 2a,4and5) serves to center the fan assembly14in the fuselage12(see alsoFIG. 3). In the illustrated embodiment the mechanism37comprises spaced idler rollers50connected to the fan hub34by rocker arms52. More specifically and as best illustrated inFIG. 2a, each rocker arm52is pivotally connected to the inner wall of the fan hub34by means of a trunnion51so as to allow the rocker arm to freely pivot. A first end of the rocker arm52includes a yoke53for holding the associated idler roller50by means of a shaft55about which the roller freely rotates. A second end of the rocker arm52includes a counter weight61(not needed for alternative embodiment shown inFIG. 5). A preload spring57mounted between the fan hub34and the rocker arm52provides a force that biases the idler roller50toward the continuous race59extending around the support ring85of the fuselage12.

The preload springs57function to provide a radial preload on the idler rollers50that works to maintain centering of the fan assembly14on the fuselage12. The radial preload results in generating a tangential friction force on the fuselage12from the rollers50. The preload is sized to balance the impulse from the engine gases passing from the orifices30in the fuselage12into the receptors28of the fan assembly14. The impulse from the engine gases works in a direction opposite to the tangential friction force from rollers50. More specifically, engine exhaust gases exit the fuselage12at an angle of approximately 60 degrees which results in an overall impulse of approximately 894 lbs. For a fifteen foot diameter fan assembly14, preload force for each of seven idler rollers50will be approximately 1300 lbs. Such a preload creates an overall frictional force that counteracts the impulse force while maintaining the centering of the fan assembly14on the fuselage12up to an unbalance force of 0.73 ounces at approximately 880 RPM.

As illustrated inFIG. 3, the idler rollers50are equally angularly spaced 360° around the fan hub34to engage and roll along the continuous race59. Seven idler rollers50are illustrated inFIG. 3at spaced intervals of approximately 51.43°. While seven idler rollers50are illustrated, it should be appreciated that more or less could be provided (e.g. nine idler rollers spaced at 40° intervals and six idler rollers spaced at 60° intervals).

An active system, generally designated by reference numeral60and best illustrated inFIGS. 3 and 4, is provided for sensing vibration and balancing the fan assembly14during its rotation relative to the fuselage12. In the illustrated embodiment, the system60includes multiple strain gauges62. One strain gauge62is mounted to a lever D which is sized to bend linearly within the operating range of the strain gauge. Each lever D is connected to each rocker arm52that supports the rollers50. Thus, there are seven strain gauges62in all. Each strain gauge62is connected to additional components of the system60including an amplifier64that is connected to a DC/AC converter66that is in turn connected to a primary coil68that is associated with an induction coil72, another amplifier74, a motor76, a screw jack78and a balancing weight80. The various system components64,66,68,72,74,76,78and80associated with a strain gauge62may all be held in an internal cavity70in the fan blade32adjacent the rocker arm52and strain gauge62. Where seven sensors or strain gauges62are provided, seven related component systems are mounted in the internal cavity70of the adjacent fan blades32. Thus, if the fan assembly14includes a total of twenty-eight fan blades32, every fourth blade is equipped with a displaceable balancing weight80and the related system components62,64,66,68,72,74,76and78.

In an alternative embodiment of the active balance system illustrated inFIG. 5, the rollers50and its support including the preload spring57, the strain gauge62, the amplifier64, the DC/AC converter66and the primary coil68are mounted on the structural ring85of the fuselage12. The secondary induction coil72is mounted on the fan14, along with the amplifier74, the screw jack78and the balance weight80. The primary coil68is connected to the roller50to maintain a close spacing from the secondary coil72.

Vibration, as sensed by a radial displacement of the fan assembly14exceeding preload force of the springs57, produces a radial load on the idler rollers50riding on the smooth surface of the fuselage race59. This load is continuously detected in real time by the strain gauges62that are mounted on lever D that restrains rotation of the rocker arms52holding the idler rollers50. As a result, each strain gauge62produces an EMF or current signal proportional to the load sensed. That signal is amplified by the amplifier64associated with each strain gauge62. Each amplified signal is then converted from direct current to alternating current by the associated converter66before being transmitted to the primary coil68associated with each roller50. Thus, at any given moment, the system60produces seven signals for correcting the balance of the fan assembly14, one signal at each primary coil68. Vibration sensing in the alternative embodiment is similarly conducted.

The primary coils68transfer the signals to the adjacent induction coils72. The seven signals are then sent to the amplifiers74for amplification before being sent to the associated motors76which drive the screw jacks78that in turn radially adjust the position of the balancing weights80provided in the fan blades32. The balancing weights80are displaceable in either direction as illustrated by action arrow A within the cavities70of the seven fan blades32in order to restore balance to the fan assembly14. For so long as vibration is detected, the strain gauges62will produce a proportional current that results in a correction signal. Thus, the motors76are driven continuously to move the balancing weights80in the various fan blades32until balance is achieved. At that time, vibration ceases, the strain gauges62fail to produce a current, the motors78stop and the balancing weights80remain stationary.

The application will dictate installation requirements. For example, for a fan assembly14with a diameter of about 15 feet, the balancing weights80may each weigh on the order of about 1.0 to about 4.0 lbs. The range of motion for each balancing weight80within each fan blade32is less than one foot. In contrast, for a fan assembly of about 84 feet the balancing weights80each weigh on the order of about 12.3 lbs and the range of motion is on the order of five feet. Further, while the components of the active system60just described are connected to each of the idler rollers50inFIG. 3, it should be appreciated that such a system may be provided on fewer than all the idler rollers50if desired (e.g. every other idler roller, every third idler roller).

As best illustrated inFIG. 6, a brush seal assembly90thermally isolates the first bearing mechanism35and second bearing mechanism37in the work space92defined between the fuselage12and the fan assembly14from the hot exhaust gases passing through the feed duct26to the nozzles25arrayed annularly around the fan assembly14. As illustrated, a brush seal94extends across the entry to the work space92both above and below the receptors28. A brush seal manifold96is provided between the brush seals94and the interface106between the receptors28and the orifices30. Pressurized air is provided to the brush seal manifold96through the supply lines98that are connected to a pressurized air source100(e.g. the high pressure compressor stage of at least one of the engines20,22,24). A pressure sensor108is mounted in the space92to monitor pressure in that space. Alternatively, a pressure sensor108could be mounted in the intake receptor28or orifice30adjacent the interface106to monitor the hot exhaust gas pressure. Preferably multiple sensors108are mounted in such a position for redundancy. The pressure sensors108are connected to a controller110that is connected to a pressure regulator112that regulates the pressure of the air supplied by the pressurized air source100to the brush seal manifold96by the supply lines98. As the pressurized air from the source100is regulated down in pressure to match the sensed pressure of the exhaust gases at the interface106, it undergoes expansion and cooling. Typically, the pressurized air provided to the brush seal manifold96has a temperature of about 80° F.±20° F. Of course, an optional air cooler could be provided in the lines98if further cooling is desired.

The pressure ratio P2/P1of engine gases at the interface106(P1) and the hot gas nozzle pressure25(P2) should be maintained above 0.524 in order to accelerate the hot gases to sonic velocity at the eyeball nozzle exit. As noted above the brush seal manifold pressure96should be maintained to substantially match the hot gas pressure at the interface106at all times of operation in order to maintain the desired air curtain between the brush seal94and the hot exhaust gases at the interface106between the intake receptors28and orifices30. Stated another way, the pressurized air provided to the brush seal manifold94should have a pressure P2equal to or greater than the pressure P1of the hot exhaust gases at the interface106in order to maintain the integrity of the air curtain.

In summary, numerous benefits result from employing the concepts of the present invention. An HSVTOL aircraft10equipped with the active system60for sensing vibration and balancing the fan assembly14represents a significant advance in the art. By reducing and eliminating vibration with an active system60, the stability of the aircraft10is enhanced. This is a particularly important feature for military aircraft10as the fan assembly14may become damaged in combat, lose balance and produce a vibration that might otherwise make the aircraft10difficult to control during hovering, landing and/or take off. Advantageously, by manipulating the radial position of the balancing weights80in and out along the various fan blades32equipped with the balancing system60, in many instances it will now be possible to compensate for the out-of-balance condition.

The foregoing description of a preferred embodiment of the present invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Obvious modifications or variations are possible in light of the above teachings.

For example, as illustrated in theFIG. 5embodiment, the idler rollers50may be mounted to or carried on the fuselage12if desired. In this embodiment, each rocker arm52is pivotally connected to the fuselage12by means of a trunnion51which allows the rocker arm to freely pivot. A preload spring57is mounted between each of the rocker arms52and the fuselage12to provide a force to bias the idler rollers50toward the continuous race59extending around the fan hub34. Thus, the desired preload is again provided to maintain the centering of the fan assembly14on the fuselage. In this embodiment, the imbalance signal from the strain gauge62is amplified on the body12and transmitted to the fan assembly14by means of magnetic induction between the primary and induction coils68,72. The signal is then sent to the associated motor76to drive the screw jack78and adjust the position of the weight80.

Further, while the horizontal bearing assembly37of the illustrated embodiment includes a plurality of idler rollers50, it should be appreciated that other structures could be utilized for the same purpose. Such alternative structures include but are not necessarily limited to air bearings and/or foil bearings or a combination of these structures with roller bearings.

The embodiment was chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally and equitably entitled. The drawings and preferred embodiments do not and are not intended to limit the ordinary meaning of the claims and their fair and broad interpretation in any way.