Aeronautics and astronautics – Aircraft – heavier-than-air – Airplane and fluid sustained
Reexamination Certificate
1999-02-08
2001-11-20
Swiatek, Robert P. (Department: 3643)
Aeronautics and astronautics
Aircraft, heavier-than-air
Airplane and fluid sustained
C244S02300R, C239S265190
Reexamination Certificate
active
06318668
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to thrust vectoring techniques, and more particularly, but not exclusively, relates to techniques to control thrust vectoring and nozzle throat area with variable pitch guide vanes.
Typically, a jet powered aircraft is controllably propelled by thrust substantially parallel with and in a direction opposite working fluid exiting a nozzle. Consequently, if the direction of the working fluid is changed, the direction of propulsive thrust and the aircraft direction is corresponding varied. As used herein, “nozzle” means an aircraft passage or outlet for discharging working fluid to produce thrust.
With the advent of vertical or short take off and vertical landing (V/STOVL) aircraft, the need for efficient, uninterrupted vectoring of thrust has arisen. The hot gases exhausted from a gas turbine engine are one source of working fluid which may be vectored. Alternatively, “cold flow” from a lift fan may also serve as a working fluid source. Such a lift fan is typically driven indirectly by a coupling to a gas turbine engine. U.S. Pat. No. 5,209,428 to Bevilaqua et al. is cited as a source of further information concerning lift fan aircraft.
For the V/STOVL mode of aircraft operation, a continuous, uninterrupted vectoring of thrust is required throughout a wide angular range to provide lift for the aircraft. Also, a smooth and reliable transition to a horizontal cruise mode is often required. Moreover, as with most aircraft equipment, thrust vectoring systems generally must be lightweight, reliable, and compact, occupying as little space as possible. U.S. Pat. Nos. 5,769,317 to Sokhey et al.; U.S. Pat. No. 5,485,958 to Nightingale; U.S. Pat. No. 3,640,469 to Hayes et al.; U.S. Pat. No. 3,397,852 to Katzen; U.S. Pat. No. 3,179,353 to Peterson; and U.S. Pat. No. 2,989,269 to Le Bel illustrate various guide vane bank arrangements for vectoring thrust.
One typical drawback of these systems is the inability to selectively adjust the exit area presented to working fluid as it passes through the vanes while simultaneously and independently deflecting the exiting working fluid to vector thrust. The ability to select the working fluid exit area or throat area generally improves vectoring system efficiency.
One approach to this problem is to simultaneously adjust vectoring and throat area by using an independently controllable actuator for each vane in the bank. Unfortunately, this approach is often impractical because of the attendant increase in weight, complexity, and space required for the separate actuators.
Furthermore, proposed systems do not appear to account for changes in thrust efficiency of a given vectoring nozzle design that occur in response to changes in pivotal orientation of the vanes.
Thus, there remains a need for improved techniques to selectively vector thrust with a number of guide vanes.
SUMMARY OF THE INVENTION
One form of the present invention is to discharge working fluid from an aircraft to produce thrust and vector thrust by deflecting the working fluid with a number of vanes.
In an alternative form an improved thrust vectoring system is provided.
In another alternative form, a thrust vectoring system includes a plurality of thrust directing members positioned across a discharge outlet. These members include a plurality of leading edge caps and a corresponding plurality of articulating vanes. The vanes are each nested within a recess defined by a corresponding one of the leading edge caps to pivot relative thereto. The directing members may span across a generally rectangularly shaped outlet. Also, in one preferred embodiment, the leading edge caps are fixed to a wall of the passage and arranged in a convergent pattern relative to a reference axis.
A further alternative form of the present invention is a method and technique for discharging a working fluid through an outlet of an aircraft nozzle to produce thrust; where the nozzle is in fluid communication with an aircraft working fluid source and has at least four vanes pivotally mounted across the outlet. The vanes are pivoted to change thrust direction during this discharge including adjusting convergence of the vanes to maintain a first throat area. Also, magnitude of the thrust is modulated while the working fluid is being discharged by pivoting the vanes to change from the first throat area to a second throat area while maintaining a generally constant direction of the thrust.
Another alternative form includes a thrust vectoring nozzle with a number of guide vanes. Variation of the nozzle's discharge coefficient with changes in vane orientation results in an attendant change in effective throat area of the nozzle. Changes in effective throat area may not be uniform with respect to changes in the geometric throat area of the nozzle. As used herein, the “discharge coefficient” of a nozzle refers to the ratio between actual fluid mass flow through the nozzle and the ideal or theoretically attainable fluid mass flow through the nozzle. For practical nozzle designs, the discharge coefficient is generally less than one (<1) due to the formation of boundary layers and other non-ideal conditions. The “geometric throat area” of a nozzle refers to the measured throat area of the nozzle configuration. The “effective throat area” of a nozzle refers to a nozzle area that is required to attain a desired actual mass flow rate through a given nozzle configuration and is defined by the expression:
effective throat area=(AFR/IFR)*GTA;
where AFR=actual flow rate, IFR=ideal or theoretically attainable flow rate, and GTA=geometric throat area of the nozzle. The term (AFR/IFR) is the discharge coefficient for the given nozzle. For a discharge coefficient less than one (<1), the effective throat area is less than the geometric throat area. Maintaining a generally constant geometric throat area while discharge coefficient varies with changes in vane orientation, typically results in a change in thrust vector magnitude for a constant level of working fluid supplied to the nozzle. In contrast, a generally constant effective throat area accounts for discharge coefficient changes and results in an approximately constant thrust magnitude for a constant level of working fluid supplied to the nozzle.
In an additional alternative form, an aircraft is operated that has a passage with an outlet. The aircraft has at least four vanes pivotally mounted across the outlet. This operation includes discharging a working fluid through the outlet to produce thrust. The vanes are pivoted to change thrust direction during discharge of the working fluid. Also, while the working fluid is being discharged, the vanes are splayed to modulate thrust magnitude while maintaining a generally constant thrust vector direction.
Another alternative form of the present invention includes operating an aircraft with a passage having an outlet; where at least four vanes are pivotally mounted across the outlet. This operation includes discharging a working fluid through the outlet to produce thrust. During this discharge of the working fluid, the vanes are pivoted to vector the thrust over a predetermined range of directions. Geometric throat area is changed during this pivoting to maintain a generally constant effective throat area over the range of directions.
Other alternative forms include an aircraft defining a passage having an outlet and a lift fan mounted in the passage operable to discharge working fluids through the outlet to produce thrust. Also, at least four vanes are pivotally mounted across the outlet to vector the thrust. An actuator controlled linkage couples the vanes which simultaneously pivot in response to movement of the linkage. A controller generates a vane control signal to provide a desired thrust vector; where the control signal corresponds to a desired pivotal orientation of each of the vanes and is determined in accordance with data corresponding to a relationship between thrust vector direction and throat area. The linkage responds to this
Baker Von D.
Sokhey Jagdish S.
Ulanoski Michael S.
Vittal Baily R.
Allison Advanced Development Company
Swiatek Robert P.
Woodard Emhardt Naughton Moriarty & McNett
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