Power plants – Reaction motor – Interrelated reaction motors
Reexamination Certificate
1999-12-02
2001-07-10
Freay, Charles G. (Department: 3746)
Power plants
Reaction motor
Interrelated reaction motors
C239S265370, C244S11000H
Reexamination Certificate
active
06256979
ABSTRACT:
The present invention relates to a gas-ejection structure for jet engines and more particularly for aircraft engines of the bypass type, that is to say those equipped with a fan situated upstream of the engine and providing for a cold-air current to flow in an annular channel formed between an outer cowling and an axial nozzle for ejecting the flow of hot propulsion gases, the cold and hot flows flowing out and then being mixed in a downstream passage of substantially circular cross-section.
More specifically, the invention relates to an ejection structure of the type indicated above incorporating a thrust-reverser system including two doors each having an upstream edge and a downstream edge, by reference to the direction of flow of the gases, the said doors being arranged downstream and each being mounted pivoting about axes of articulation between a stowed position (not interfering with the ejection of the gases in forward-thrust mode) in which, in association with two fixed lateral beams which are symmetric with respect to the axis of the engine, they contribute to defining the said outer cowling, and a deployed position (causing the thrust reversal) in which the said doors clear a passage in the cowling for reversal of the gases while blocking off the channel, the two lateral beams, onto which the said doors are articulated, forming part of a fixed structure and including downstream ends which are independent and spaced apart from one another.
A reverser assembly of this type is already known from the French patent No 2 382 594, filed on Mar. 4, 1977. However, whereas it completely fulfils its role of deflecting the flow of gases and thus of effective braking in doors-deployed position, the reverser assembly described in this prior patent exhibits a certain number of drawbacks. This is because, in this patent, on the one hand, the axes of articulation of the doors are situated at the end of narrow lateral beams and, on the other hand, the downstream edges of the doors, which, in doors-stowed position, or “forward thrust” position, are in inclined planes with respect to the longitudinal axis of the engine, form a V-shaped or “fish's mouth” section between them, which is prejudicial to the efficiency of the engine in forward-thrust mode and does not correspond to the specifications which require a gas-exit cross-section which is as close is possible to a plane perpendicular to the axis of the engine.
A thrust reverser is known moreover from EP-A-0 774 578, comprising two shells in which cut-outs are formed allowing the shells to deflect and to come face-to-face in reversal mode, in such a way that the mid-parts of the downstream edges of the shells, with the beams to which the shells are articulated, form a cowling edge in the form of a discontinuous circle.
The main drawback of this known structure is that the cut-outs formed in the shells create geometric discontinuities on the exit cross-section of the reverser, having a negative effect on the efficiency of the engine in forward-thrust mode.
The present invention intends to remedy this drawback and is characterized, to this end, in that the downstream end of each of the beams includes lateral protrusions on either side of the longitudinal axis thereof, and in that, in doors-stowed position or forward-thrust position, the distance between the mid-part of the downstream edges of the said doors and the plane perpendicular to the axis of the engine passing through the axes of articulation of the doors, is equal to the distance separating the said perpendicular plane and the downstream ends of the lateral beams, so that the mid-parts of the downstream ends of the doors and the downstream ends of the beams constitute a cowling edge through which the gases exit, which is at the same time substantially circular and substantially continuous, this assembly being contained in a plane parallel to the plane passing through the axes of pivoting of the doors.
In order to obtain a gas-exit cross-section in forward-thrust mode as indicated above, one specific embodiment of the invention makes provision, in doors-stowed position, that:
the outline, or first outline, of the plane containing the mid-part of the downstream edges of each door on a reference plane consisting of the vertical plane containing the axis of the engine, and
the outlines, or second and third outlines, on this same reference plane, of the planes containing the lateral parts of the downstream edge of the said doors respectively
together define an isosceles triangle the base of which consists of a part of the said first outline and the vertex of which is situated on the upstream side with respect to the said first outline,
the equal angles of the said isosceles triangle being less than 40°, and preferably about 30°.
The consequence of this arrangement is that, in doors-deployed position (reversal position), the downstream edges of the doors, which come to block off the channel, form, between their opposing mid-parts, an elongate aperture through which a small part of the gas flow escapes along the axis of the engine.
Moreover, the downstream end of each of the beams, on either side of the longitudinal axis thereof, includes symmetric lateral protrusions, the distance separating the end of the protrusions of the same beam being greater than the distance separating the two adjacent axes of the doors on the said beam.
REFERENCES:
patent: 4147027 (1979-04-01), Greathouse
patent: 5390879 (1995-02-01), Lair
patent: 0 774 578 (1997-05-01), None
patent: 2 601 077 (1988-01-01), None
patent: 2 697 292 (1994-04-01), None
patent: 2696212A1 (1994-04-01), None
Fournier Alain
Standish Robert
Freay Charles G.
Hayes Eric D.
Societe de Construction des Avions Hurel-Dubois (Societe Anonyme
Young & Thompson
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