BEST MODE FOR CARRYING OUT THE INVENTION

[0025] As seen in FIG. 1, a simplified illustration of a turbo fan type jet engine is illustrated with the majority of parts either eliminated or shown in outline for simplicity so as to not detract from the invention.

[0026] FIG. 1 is illustrative of two phases of the current invention, with the top portion of the figure illustrating the engine configuration in the noise suppressing configuration for takeoff and landing, and the bottom half of the illustration depicts the configuration during the thrust reversing process. At the center of the illustration and overlapping both halves is the main engine 2 which may include a mixer 4 toward the rear of the turbine casing 6 , and also includes an exhaust nozzle.

[0027] Surrounding the engine components 2 through 6 is a nacelle or cowling 8 having a forward section 10 and an aft section 12 , which during normal operation, assume the configuration as shown in FIG. 2 , wherein identical numerals are used to identify identical parts in FIG. 1 .

[0028] The aft portion 12 of the nacelle, however, is translated rearwardly in FIG. 1 exposing a plurality of apertures or cascades 14 around the nacelle 8 which as illustrated in FIG. 1 , top half, admit ambient air which mixes with the fan air and eventually with the exhaust out of the exhaust nozzle. The mixture has the effect of reducing the overall velocity of the jet exhaust and increasing the velocity of the attached ambient air relative to the overall jet exhaust mass air. This gas velocity modification reduces the level of kinetic energy created by the differences in the untreated jet velocity and the untreated ambient air speed, thereby, dramatically reducing ambient engine noise.

[0029] It is acknowledged that there exist fixed inducers attached to an airplane's engine in various configurations. The present invention introduces similar ambient air induction theory without the corresponding drag during normal cruise operation. The present invention introduces ambient air without the corresponding drag and, properly applied, can be adapted to existing thrust reversers without the addition of either forward or aft inducer.

[0030] Referring to the bottom half of FIG. 1 , it can be seen that when the thrust reverser blocker door 16 , which was stowed in the upper half, has been deployed, air is forced forwardly through the cascades 14 , creating a reverse air flow to stop the forward motion of the engine and plane to which it is attached.

[0031] Direct reference is now had to FIGS. 3, 4 and 5 which illustrate a ducted fan engine utilizing the same principle as with respect to (the high by-pass) turbo fan illustrated in FIGS. 1 and 2 . The structure of FIGS. 3 and 4 includes a nacelle 20 having a forward section 22 and a rearward section 24 surrounding an engine 26 . FIG. 3 illustrates the engine in the noise suppression mode, wherein the aft portion of the nacelle 24 has been translated rearwardly exposing the apertures or cascades 27 around the cowling for the induction of ambient air to mix with the fan and exhaust air. The reverser buckets 28 are stowed allowing the air to pass therethrough, again by inducing the ambient air, reducing the relative velocities and thus reducing the resultant noise.

[0032] FIG. 4 is similar to FIG. 1 in that the illustration is divided into two halves, wherein the upper half illustrates the bucket 28 deployed in the thrust reversing position as shown by the air flow arrows, and the lower portion in the normal cruise position, wherein the aft portion 24 of the nacelle or cowling 20 is adjacent the forward portion 22 covering the cascades or apertures 27 and forming a relatively unrestricted air stream past the stowed buckets 28 .

[0033] Looking now at FIG. 5 , the aft portion of a jet engine is shown, including the nacelle having a forward section 30 and thrust reverser rearward section 32 as shown surrounding a shrouded actuation system 34 . The rearward end of the nacelle 32 is also utilized as a reverser sleeve, and although shown in two dimensions, it is to be understood that it is in fact two halves surrounding the engine plug when in its stowed position 32 a . As explained in greater detail hereinafter, the section 32 is translated to 32 b during takeoff and landing, causing ambient air to flow inwardly through the now open space 34 and, because of the configuration of the inner wall of 32 , this air is forced by the forward motion of the airplane to pass through a nozzle portion 36 , causing an increase in the flow rate closer to the flow of exhaust from the engine, and therefore, having a reduced velocity difference, again causing a noise suppression.

[0034] As explained hereinbefore, the third position of 32 is shown at 32 c , which is the thrust reverser position for stopping the engine and the attached airplane.

[0035] Thus, as can be seen, the present invention does not burden the currently existing engines with additional weight and/or hardware, but by modifying the operation and controls of the existing hardware, allows the pilot to selectively use the hardware to reduce engine noise.

[0036] The container formed in modern jet and turbo jet engines by the retracted aft portion of the nacelle or cowling and the restricted exhaust nozzle create a condition addressed in the standard kinetic theory, and releases the contained pressurized kinetic energy as pollutant noise.

[0037] As seen in FIG. 3 , by translating the container aft nacelle section, sometimes known as the thrust reverser sleeve, with the blocker doors or buckets still stowed, thereby opening up the reverser cascades or apertures to the ambient air velocity upstream, the average velocity of the gases in the container is reduced. The induction of lower velocity gas into the higher velocity fan and/or jet stream by translating the aft portion without blocking the flow, mechanically creates a flexible, translating inducer. Executing or translating the aft portion or thrust reverser sleeve translation without blocking, creates an inducer as opposed to the thrust reverser which is standard when the flow is blocked by the blocker doors or buckets.

[0038] In the present application of the kinetic theory, the flow in the translated sleeve of the thrust reverser is not blocked, completing the new event that dramatically reduces the kinetic energy and the noise this ineffective energy produces. This resultant, modified gas stream will be quieter and more thrust efficient, since the random kinetic energy producing the noise is reduced by the new induced ambient air flow into the translated sleeve through the cascades, or through the opening created by the translated thrust reverser sleeve or sleeve halves, and the induced mass flow of the gas path particle stream is more uniform in its direction to provide effective thrust with less noise.

[0039] To convert the standard thrust reverser into a noise reducing device, while maintaining the desirable characteristics of the thrust reverser, the buckets and/or blocker doors are operated independently of the translating aft sleeve function.

[0040] This transition is accomplished in the preferred embodiment by introducing an actuator system in the thrust reverser linkage under the control of the flight crew. The actuator or actuators will not function only when thrust reversing is desired. When activated, only forward thrust is produced, and the blocker doors will remain stowed whenever the thrust reverser is translated aft. To disengage these actuators from functioning by not restraining the blocker doors or buckets from blocking the gas stream and forcing it through the reverser cascades, a full reverse event is required in the operating procedure.

[0041] Although, it is certainly subject to further modification, the invention currently utilizes at least two operating cycles. In a fairly standard control configuration, the reverse thrust is engaged by the cockpit throttle, when the throttle is lifted over a reverser gate of the throttle quadrant. This procedure can remain standard. Should this be the objective, the engine noise reduction system will always be deactivated if the throttles are lifted over the reverse gate of the quadrant into the reverser range of the throttle quadrant.

[0042] In this configuration if noise reduction is subsequently desired, the takeoff procedure would have the engine noise reduction feature applied in the forward thrust range only. When activated, this feature will prevent the blocker doors and/or buckets from deploying, while causing the thrust reverser sleeve to translate and open the reverser cascades to the ambient air stream, creating noise reduction. The engine noise reduction feature may be applied every time takeoff is desired, or only when noise reduction is desired.

[0043] The flight crew may introduce the engine noise reduction feature to translate the thrust reverser sleeve with the blocker and/or buckets stowed while taxiing to the takeoff threshold. The throttles would be in the forward thrust range of the throttle quadrant, as the airplane is taxiing. While the engine noise reduction is now activated, and the blockers and/or buckets are stowed with the thrust reverser sleeve translated, and all throttles are forward of the reverser gate, all operating takeoff and initial climb procedures remain unchanged. At cutback, the engine noise reduction feature would then be automatically or manually disengaged by the flight crew. It would appear logical that the engine noise reduction system is activated on each engine independently by depressing an automatic hold-down type button that illuminates to indicate to the flight crew that the engine noise reduction is initiated and the thrust reverser sleeve has translated and that the blocker doors or buckets are stowed. The system can be deactivated by either pulling out this hold-down button, or returning the throttle to the idle range after they have first been advanced to the takeoff range as long as the squat switch has not been activated, or alternatively by lifting the throttles over the full reverse gates of the throttle quadrant. The full reverse selection will always override the engine noise reduction system, thereby rendering the engine noise reduction system as failsafe, either forward of the reverser gate, or aft of the reverser gate.

[0044] It may be preferable on some installations to leave the forward thrust throttle quadrant range unmodified, and to use the full reverse range for full reverse and for engine noise reduction takeoff. If this is desired, the engine noise reduction hold-down buttons would only operate after the gate of the throttle quadrant range. If full reverse is subsequently desired, the engine noise reduction buttons would be manually disengaged, permitting the blocker doors or buckets to deploy. An engine noise reduction would also be automatically disengaged when the throttles are advanced and dropped through the gate at cut back, permitting the thrust reverser sleeve to retract. In this configuration the engine is in engine noise reduction takeoff operation after initial takeoff is performed, and after the first segment of climb has been accomplished, the throttle would be advanced to the idle gate to cut back, causing the thrust reverser sleeve to retract and disarming the engine noise reduction, and when then the throttles are advanced further to initiate the second segment of climb as is normally performed to continue the climb to cruise altitude.

[0045] Thus, as can be seen, the present invention allows selective engine noise reduction with minor modifications to the engine configuration, the only modification being to the control sector.