Patent US4068469A successfully refreshed from Google Patents.
US4068469A
Expired / Lapsed
US
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Variable thrust nozzle for quiet turbofan engine and method of operating same
Assignee: National Aeronautics and Space Administration
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Filing: 1975-05-29
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Granted: 1978-01-17
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Expires: 1995-05-29
Abstract
Abstract An improved method of operating a gas turbine engine is presented wherein engine-generated noise is maintained at a reduced level during reduced thrust operation. Fan speed is maintained at a constant level while fan nozzle area is increased. This maintains high inlet Mach numbers for reduced forward noise propagation and also permits reduced nozzle exhaust velocity for reduced shear noise. In another embodiment, airflow is increased by means of a fan blade pitch change or speed increase while the fan nozzle area is increased, yielding both a net reduction in engine thrust and noise.
Inventors
- 👤 Arthur P. Adamson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 23:31
CPC Classifications
F; F02; F02K; F02K1/00; F02K1/06; F02K1/15; F02K1/16
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
123 words
A method of operating an aircraft gas turbofan engine in a forward flight mode including the steps of: pressurizing air flowing through a stage of rotating fan blades disposed within an inlet duct; passing a portion of the air through an annular bypass duct of generally fixed geometry; discharging said portion through a nozzle of the type having a generally constant inlet area and variable exit area; and modulating the nozzle exit area from a first value associated with a flight cruise operating condition which is convergent with respect to the nozzle inlet to a second value which is at least five percent greater than the first value, thereby reducing engine thrust and noise; and wherein fan blade rotational speed is essentially constant.
Claim 2
Independent Claim
123 words
A method of operating an aircraft gas turbofan engine in a forward flight mode including the steps of: pressurizing air flowing through a stage of rotating fan blades disposed within an inlet duct; passing a portion of the air through an annular bypass duct of generally fixed geometry; discharging said portion through a nozzle of the type having a generally constant inlet area and variable exit area; and modulating the nozzle exit area from a first value associated with a flight cruise operating condition which is convergent with respect to the nozzle inlet to a second value which is at least five percent greater than the first value, thereby reducing engine thrust and noise; and wherein fan blade rotational speed is essentially constant.
Claim 3
Independent Claim
124 words
A method of operating an aircraft gas turbofan engine in a forward flight mode including the steps of: pressurizing air flowing through a stage of rotating fan blades disposed within an inlet duct; passing a portion of the air through an annular bypass duct of generally fixed geometry; discharging said portion through a nozzle of the type having a generally constant inlet area and variable exit area; and modulating the nozzle exit area from a first value associated with a flight cruise operating condition which is convergent with respect to the nozzle inlet to a second value which is at least five percent greater than the first value, thereby reducing engine thrust and noise; and wherein the inlet duct Mach number is essentially constant.
Claim 4
Independent Claim
124 words
A method of operating an aircraft gas turbofan engine in a forward flight mode including the steps of: pressurizing air flowing through a stage of rotating fan blades disposed within an inlet duct; passing a portion of the air through an annular bypass duct of generally fixed geometry; discharging said portion through a nozzle of the type having a generally constant inlet area and variable exit area; and modulating the nozzle exit area from a first value associated with a flight cruise operating condition which is convergent with respect to the nozzle inlet to a second value which is at least five percent greater than the first value, thereby reducing engine thrust and noise; and wherein the inlet duct Mach number is essentially constant.
Claim 5
Independent Claim
125 words
A method of operating an aircraft gas turbofan engine in a forward flight mode including the steps of: pressurizing air flowing through a stage of rotating fan blades disposed within an inlet duct; passing a portion of the air through an annular bypass duct of generally fixed geometry; discharging said portion through a nozzle of the type having a generally constant inlet area and variable exit area; modulating the nozzle exit area from a first value associated with a flight cruise operating condition which is convergent with respect to the nozzle inlet to a second value which is at least five percent greater than the first value; and increasing the Mach number of the air flowing through the inlet duct, thereby reducing forward propagating noise.
Claim 6
Independent Claim
125 words
A method of operating an aircraft gas turbofan engine in a forward flight mode including the steps of: pressurizing air flowing through a stage of rotating fan blades disposed within an inlet duct; passing a portion of the air through an annular bypass duct of generally fixed geometry; discharging said portion through a nozzle of the type having a generally constant inlet area and variable exit area; modulating the nozzle exit area from a first value associated with a flight cruise operating condition which is convergent with respect to the nozzle inlet to a second value which is at least five percent greater than the first value; and increasing the Mach number of the air flowing through the inlet duct, thereby reducing forward propagating noise.
Claim 7
Dependent Claim
19 words
The method of claim 3 wherein the increase in Mach number is accomplished by increasing fan blade rotational speed.
Claim 8
Dependent Claim
21 words
The method of claim 3 wherein the increase in Mach number is accomplished by changing the pitch of the fan blades.
Claim 9
Independent Claim
121 words
A method of operating an aircraft gas turbofan engine in a forward flight mode including the steps of: pressurizing air flowing through a stage of rotating fan blades disposed within an inlet duct; passing a portion of the air through an annular bypass duct of generally fixed geometry; discharging said portion through a nozzle of the type having a generally constant inlet area and variable exit area; and modulating the nozzle exit area from a first value associated with a flight cruise operating condition which is convergent with respect to the nozzle inlet to a second value associated with a landing approach operating condition which is at least five percent greater than the first value, thereby reducing engine thrust and noise.
Claim 10
Independent Claim
121 words
A method of operating an aircraft gas turbofan engine in a forward flight mode including the steps of: pressurizing air flowing through a stage of rotating fan blades disposed within an inlet duct; passing a portion of the air through an annular bypass duct of generally fixed geometry; discharging said portion through a nozzle of the type having a generally constant inlet area and variable exit area; and modulating the nozzle exit area from a first value associated with a flight cruise operating condition which is convergent with respect to the nozzle inlet to a second value associated with a landing approach operating condition which is at least five percent greater than the first value, thereby reducing engine thrust and noise.
Claim 11
Dependent Claim
29 words
The method of claim 6 wherein the second value of nozzle exit area is generally between five and thirty percent greater than the first value of nozzle exit area.
Claim 12
Dependent Claim
60 words
The method of claim 6 wherein the first value of nozzle exit area is established such that the flow area converges approximately thirty percent from the inlet to the exit of the variable area nozzle and wherein the second value of nozzle exit area is established such that the flow area distribution through the variable area nozzle is substantially constant.
Claim 13
Dependent Claim
41 words
The method of claim 8 wherein the second value of nozzle exit area is established such that the flow area distribution through the variable area nozzle is divergent to the extent that the airflow is diffused without separation within the nozzle.
References Cited (Backward Citations)
US2934966A
Cited
US3060680A
Cited
US3514952A
Cited
US3261164A
Cited
US3484847A
Cited
US3401524A
Cited
US3747341A
Cited
US3913626A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1981-01-16 | 1981-07-18 | 1982-01-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-01-16 | 1985-07-18 | 1986-01-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-01-16 | 1989-07-18 | 1990-01-17 | $7700.00 | Window Closed / Lapsed |