News Column

"Aircraft Propulsion Unit Including at Least One Turbojet Engine and a Nacelle" in Patent Application Approval Process

June 12, 2014



By a News Reporter-Staff News Editor at Politics & Government Week -- A patent application by the inventor Caruel, Pierre (Le Havre, FR), filed on January 28, 2014, was made available online on May 29, 2014, according to news reporting originating from Washington, D.C., by VerticalNews correspondents.

This patent application is assigned to Aircelle.

The following quote was obtained by the news editors from the background information supplied by the inventors: "The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.

"An aircraft is moved by several turbojet engines each housed in a nacelle also housing a set of connected actuating devices related to its operation and performing various functions when the turbojet engine is operating or stopped. These connected actuating devices in particular comprise a mechanical thrust reverser device.

"The propulsion assembly of the aircraft formed by the nacelle and the turbojet engine is designed to be suspended from a stationary structure of the aircraft, for example below a wing or on the fuselage, by means of a suspension pylon.

"The nacelle generally has a tubular structure comprising an air intake upstream from the turbojet engine, a middle section designed to surround a fan of the turbojet engine, a downstream section housing the thrust reverser means and designed to surround a combustion chamber and the turbines of the turbojet engine, and generally ends with a jet nozzle whereof the outlet is situated downstream from the turbojet engine.

"This nacelle may be designed to house a dual flow turbojet engine, i.e., a turbojet engine capable of generating a hot air flow (also called primary flow) coming from the combustion chamber of the turbojet engine and by means of the rotating fan blades, and a cold air flow (secondary flow) that circulates outside the turbojet engine through a flow tunnel of the cold air flow.

"An outer structure called OFS (Outer Fan Structure), housing the thrust reverser means, and an inner structure IFS (Inner Fan Structure), designed to cover a downstream section of the turbojet engine, both belonging to the downstream section of the nacelle, define the flow tunnel of the cold air flow as well as a passage section of the cold air flow.

"The thrust reverser device is able, during landing of the aircraft, to improve the braking capacity thereof by reorienting at least part of the thrust generated by the turbojet engine forward. During that phase, it obstructs the flow tunnel for the cold air flow and orients the latter toward the front of the nacelle, thereby generating a counterthrust that is added to the braking of the wheels of the aircraft.

"In the case of a so-called cascade reverser, the cold air flow is reoriented by cascade vanes associated with a cowl having a sliding function serving to expose or cover said vanes.

"Additional blocking doors, also called flaps, activated by the sliding of the cowl, allow closing of the flow tunnel of the cold air flow, downstream from the vanes so as to allow the reorientation of the cold air flow toward the cascade vanes.

"These flaps are mounted pivotably on the cowl sliding between a retracted position, in which they provide, with said moving cowl, the aerodynamic continuity of an inner wall of the outer structure of the nacelle, and a deployed position in which, in the thrust reversal situation, they at least partially close off the tunnel so as to deflect the flow of cold air toward the cascade vanes exposed by the sliding of the cowl.

"Traditionally, the pivoting of each flap is guided by connecting rods attached on the one hand to the flap, and on the other hand to a stationary point of the inner structure of the nacelle delimiting the flow tunnel for the flow of cold air.

"The installation of such a cascade thrust reverser device on a turbojet engine below the wing is made complex when the maximum nacelle height constraint is critical due to a low ground clearance of the aircraft and a proximity between the turbojet engine and the wing of the aircraft.

"Such an installation furthermore involves delicate management of the passage section for the cold air flow.

"In the context of this issue, it has already been proposed to place, in an aircraft with low ground clearance, a cascade thrust reverser device by reducing the length of the cascade vanes and increasing the axial air leaks naturally present between the reverser flaps (so as to avoid interference), when they are deployed in the reverse jet of the device, and axial air leaks between each flap and the inner structure of the nacelle delimiting the flow tunnel for the flow of cold air.

"The leaks between each flap and the inner structure of the nacelle delimiting the tunnel are even greater when the length of the cascade vanes is reduced so as to preserve substantially the same flow rate of the cold air flow.

"This makes it possible to reduce the thickness of the moving cowl and, consequently, the nacelle, which may retain a substantially circular section.

"However, the assembling choice for such a device involves a reduced and low reverser efficiency, since the leak flow rate affects the reverser efficiency.

"In the context of this issue, it has also been proposed to reduce the height of the nacelle by proposing a nacelle that is not of revolution around the central axis of the turbojet engine, called 'flattened nacelle'.

"Such a priori flat nacelle has no impact on the reversal efficiency. It is possible to retain the same leakage level as on a reverser in a normal configuration.

"In that case, the thrust reverser flaps are of different heights to adapt to the different tunnel height at 12 o'clock (i.e., in the upper part of the nacelle) and at 6 o'clock (i.e., in the lower part of the nacelle), and the connecting rods actuating the thrust reverser flaps have different lengths to ensure that the flaps all pivot with the same angle.

"The combination of leakage flaps and flattened nacelle, with no offset kinematics, is therefore feasible with connecting rods of different lengths."

In addition to the background information obtained for this patent application, VerticalNews journalists also obtained the inventor's summary information for this patent application: "The present disclosure provides a nacelle for an aircraft with low ground clearance that has reduced dimensions while penalizing the reversal efficiency as little as possible.

"To that end, the present disclosure proposes an aircraft propulsion assembly comprising at least a turbojet engine and a nacelle, said turbojet engine nacelle comprising: an outer structure provided with a thrust reverser device, and an inner structure designed to cover a downstream section of the turbojet engine, the outer structure and the inner structure defining a flow tunnel for a flow of air from the turbojet engine, the thrust reverser device comprising: means for deflecting at least part of the flow of air from the turbojet engine, and at least one moving cowl translatable in a direction parallel to the longitudinal axis of the nacelle, the cowl being able to alternate between a closed position, in which it ensures the aerodynamic continuity of the nacelle, and an open position, in which it opens a passage in the nacelle intended for the deflected air flow, flaps mounted pivoting between a retracted position, in which they ensure the aerodynamic continuity of the nacelle, and a deployed position in which, in the thrust reversal situation, they partially close off the tunnel so as to deflect the flow of air toward the deflection means exposed by the sliding of the cowl, each flap being associated with a drive system.

"The nacelle is remarkable in that: the tunnel has a transverse section that is not constant over the periphery of the nacelle, such that at least one flap is radially offset with respect to the central axis of the turbojet engine, relative to the adjacent flaps, and the system for driving the radially offset flaps is suitable for offset kinematics of said flaps relative to the kinematics of the flaps mounted on the rest of the periphery of the tunnel, in particular to provide a different closing angle of said flaps.

"According to other features of the aircraft propulsion assembly according to the present disclosure, considered alone or in combination: the tunnel has a zone with a reduced transverse section on either side of upper and/or lower beams connected to a suspension pylon of the propulsion assembly; the radius of an inner shroud of the cowl, on either side of the upper and/or lower beams, is smaller than the radius of said shroud along the horizontal axis, perpendicular to the central axis of the turbojet engine; the drive system is suitable for implementing offset pivoting of the flaps mounted on the zone with a reduced transverse section of the tunnel relative to the flaps mounted on the rest of the periphery of the tunnel; the drive system is suitable for deploying the flaps mounted on the zone of the tunnel with a reduced transverse section upstream or downstream from the other flaps mounted on the rest of the periphery of the tunnel; the drive system is suitable for limiting an offset deployment of the flaps mounted on the zone of the tunnel with a reduced transverse cross-section relative to the flaps mounted on the rest of the periphery of the tunnel; the drive system comprises at least one driving connecting rod for each of the flaps, said connecting rods having an identical length and the anchoring points of the connecting rods situated on the flaps mounted on the zone of the tunnel with a reduced transverse cross-section are offset along the central axis and placed downstream from the anchoring points of the connecting rod situated on flaps mounted on the rest of the periphery of the tunnel; the drive system comprises at least one driving connecting rod for each of the flaps, said connecting rods having an identical length and the anchoring points of the connecting rods, situated on the inner structure of the nacelle, of the flaps mounted on the zone of the tunnel with a reduced transverse cross-section being offset relative to those of the flaps mounted on the rest of the periphery of the tunnel.

"The present disclosure further proposes a nacelle as described above.

"Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

DRAWINGS

"In order that the disclosure may be well understood, there will now be described various forms thereof, given by way of example, reference being made to the accompanying drawings, in which:

"FIG. 1 is a longitudinal cross-sectional view of an aircraft propulsion assembly;

"FIG. 2 is a transverse cross-sectional view of a discharge section of the nacelle according to one form of the present disclosure;

"FIGS. 3 and 4 are longitudinal cross-sectional views of a thrust reverser device of the nacelle of FIG. 2, in the direct jet position and the reverse jet position, respectively, the cross-sectional views of said device at a reduced tunnel section of the nacelle (solid lines) and at a nominal tunnel section of the nacelle (in dotted lines) having been superimposed in each of the figures;

"FIG. 5 is a top view of the thrust reverser device of FIG. 4.

"In all of these figures, identical or similar numbers designate identical or similar members or sets of members.

"The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way."

URL and more information on this patent application, see: Caruel, Pierre. Aircraft Propulsion Unit Including at Least One Turbojet Engine and a Nacelle. Filed January 28, 2014 and posted May 29, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=6383&p=128&f=G&l=50&d=PG01&S1=20140522.PD.&OS=PD/20140522&RS=PD/20140522

Keywords for this news article include: Aircelle.

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Source: Politics & Government Week


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