GB2293359A

GB2293359A - Jet engine thrust reversal

Info

Publication number: GB2293359A
Application number: GB9518811A
Authority: GB
Inventors: Peter Tracksdorf
Original assignee: MTU Motoren und Turbinen Union Muenchen GmbH
Current assignee: MTU Aero Engines GmbH
Priority date: 1994-09-22
Filing date: 1995-09-14
Publication date: 1996-03-27
Anticipated expiration: 2015-09-14
Also published as: GB2293359B; FR2724978B1; FR2724978A1; GB9518811D0; DE4433759C1

Description

1 Jet Engine with Thrust Reversal This invention relates to a jet engine

with thrust reversal.

To reduce aircraft landing distances, aircraft jet engines are provided with thrust reversing means.

293359 With state-of-the-art aircraft, thrust reversal is achieved by deploying a pair of buckets into the exhaust jet at the aft end of the engine nacelle to deflect the jet. This thrust reverser design is embarrassed by hot gas disadvantageously being ingested into the jet engine's intake duct.

Disclosed in U.S. Pat. No. 29 38 335 is a thrust reversing means for Jet engines where the exhaust gas flow is deflected outward by means of variable flaps of a turbine exit cone and is redirected through a permeable shroud.

Disclosed in U.S. Pat. No. 29 52 124 is a jet engine together with thrust reversing means where the nozzle throat area can be varied by means of variable exit cone flaps.

2 It is a broad object of the present invention to provide a jet engine with thrust reversal the deflected gas flow of which can be directed well enough to keep the risk of hot gas ingestion into the engine intake duct minimal while achieving maximum reverse thrust.

Claims

It is a particular object of the present invention to provide a jet engine

with thrust reverser in accordance with the features of Claim 1. Further advantageous aspects of the present invention are given in the sub-claims.

Jet engines with thrust reversal in accordance with the present invention give up to 30% more reverse thrust than conventional mixed-flow Jet engines, so that when the Jet engine of the present invention is used in aircraft, the aircraft can be landed also on very short or partially damaged landing runways and can be moved also on poorly prepared ground, up a ramp or rearward without external help. In accordance with the present invention, flaps arranged in a nozzle downstream of the basic engine and secondary duct are used to block portions of the hot gas flow from the basic engine to cause pressure losses in the hot gas flow. The forward thrust of the preferably long-duct mixed-flow jet engine is thus reduced in a comparatively simple manner. In a further aspect of the present invention the inner walls 3 of the jet engine are lined with a heat-resistant material to shield them from hot exhaust gas flows.

In a further aspect of the present invention the flaps in the nozzle downstream of the basic engine and the secondary duct are pivotally mounted about pivot axes, so that the flaps can be attached in a simple and safe manner and can readily be varied to change the degree of flow blockage in the nozzle.

In a further aspect of the present invention the number of flaps is limited to two or four to benefit the design of the engine nozzle's crosssectional area.

In a still further aspect of the present invention hydraulic actuators mounted on a rear wall of the turbine exit casing and isolated from hot air by a partition are used to safely operate the flaps in nozzle of the jet engine.

An embodiment of the invention will now be described by way of example with reference to the accompanying drawings, in which:

FIG. 1 is a cross-sectional view illustrating a jet engine of the present invention in the forward thrust mode, 4 FIG. 2 is an axial view illustrating the Jet engine of Fig. 1 in the forward thrust mode, FIG. 3 is a cross-sectional view illustrating the jet engine of Fig. 1 in the reverse thrust mode, and FIG. 4 is an axial view Illustrating the jet engine of Fig. 3 in the reverse thrust mode.

With reference now to Fig. 1 a jet engine 1 has an air intake 2 and a nozzle 3. Contained in the jet engine 1 is a secondary duct 4 and, indicated schematically, a conventional basic engine 5. The secondary duct 4 has a shroud 6 and the basic engine as a liner 7.

Downstream of the secondary duct 4 and the basic engine 5, a lobe-type mixer 8 is arranged to divide and then mix the hot flow from the basic engine 5 with the cold flow from the secondary duct 4 in a mixer tube 9 of the jet engine 1. Blending the hot and cold flows reduces the jet noise and infrared emission, the latter being an important factor especially with military transport aircraft. The lobe-type mixer 8 is arranged in the mixer tube 9 at a point relatively far upstream. The lobe- type mixer 8 and a turbine exit cone 40 are preferably configured such that the cold flow from the secondary duct 4 is drawn as far inward as possible to permit maximally thorough dissolution of the hot flow from the basic engine 5. This preferred configuration results in a relatively voluminous turbine exit cone 40.

Downstream of the lobe-type mixer 8, two or four flaps 10, 11 are arranged in the turbine exit cone 40 for pivotal motion about pivot axes 12, 13.

Hinges 14, 15 connect to actuating rods 16, 17 of two actuators 18, 19 mounted on a rear wall 20 of a turbine exit casing 21. A partition 22 intervenes between the flaps 10, 11 and the actuators 18, 19 to shield the latter from the hot gas. In a preferred aspect of the present invention the actuators 18, 19 are hydraulically operated.

In the forward thrust mode of the jet engine 1, edges 24, 25 of the flaps 10, 11 extend in parallel with a longitudinal centerline 26 of the jet engine 1. Upstream edges 27, 28 of the flaps 10, 11 are arranged radially aft of the lobe-type mixer 8 such that the flows from the secondary duct 4 and the basic engine 5 can, e.g. in cruise flight, envelope the turbine exit cone 40 with no interference from the flaps 10, 11.

Extensions 30, 31 of the flaps 10, 11 extend beyond the 6 pivot axes 12, 13 and converge relative to the longitudinal centerline 26 of the Jet engine 1 such that at the aft end of the turbine exit cone 9, an opening 23 is formed for effective venting.

With reference now to Fig. 2, where reference numerals for identical features are taken from Fig. 1, the flaps 10, 11 are concentric with the longitudinal centerline 26 of the jet engine 1. The extensions 30, 31 of the flaps 10, 11 converge towards the opening 23 to provide for effective venting.

In the forward thrust mode of the jet engine 1, the edges 24, 25 of the flaps 10, 11 extend in parallel with a transverse centerline 29 of the jet engine 1. The flaps 10, 11 are arranged radially aft of the lobe-type mixer 8 such that the flows from the secondary duct 4 and the basic engine 5 envelope the turbine exit cone 40 with no interference from the flaps 10, 11.

With reference now to Fig. 3, where reference numerals for identical features are taken from Figs. 1 and 2, thrust reversal of the jet engine 1 is effected by flaps and/or cascades (omitted on the drawing) in the shroud 6 of the secondary duct 4 to deflect the cold flow from the secondary 4 duct forward and block the secondary duct 4 in the mixer tube 9.

7 The actuating rods 16, 17 are extended from the actuators 18, 19 and the flaps 10, 11 are pivoted outward about the rotational axes 12, 13. The edges 27, 28 of the flaps 10, 11 lie in the zone of flow from the lobetype mixer 8 and block the hot gas flow from the basic engine 5 and the leakage flow from the secondary duct 4, so that flow losses result between the lobe-type mixer 8 and the nozzle 3 and the forward thrust opposing the reverse thrust is reduced. The extensions 30, 31 of the flaps 10, 11 abut one on the other along the longitudinal centerline 26 and close off the opening 23. Parting lines 32, 33 are formed between the movable flaps 10, 11 and a stationary member of the turbine exit cone 40.

With reference now to Fig. 4, where the reference numerals from Figs. 1 and 2 are used for identical features, the flaps 10, 11 are pivoted outward about their pivot axes 12, 13 when the thrust reversal means in the secondary duct 4 of the jet engine 1 is actuated. The edges 27, 28 of the flaps 10, 11 lie in the zone of flow from the lobe-type mixer 8 and block the hot gas flows from the basic engine 5 and the leakage flow from the secondary duct 4, or they displace the hot gas flows radially outward such that the reverse thrust from the secondary duct 4 is assisted by a reduction in the residual forward thrust in the mixer 8 tube 9 and in the nozzle 3, so that in the aggregate, the thrust reversal performance of the Jet engine 1 is augmented by as much as 30%.

The extensions 30, 31 of the flaps 10, 11 abut one on the other along the transverse centerline 29 and close off the opening 23. The shroud 6 is lined with a heat-resistant material at least inside the mixer tube 9.

Claims:

9 1. A jet engine with thrust reversal having an air intake, a nozzle, an engine and an annular secondary duct formed between a shroud, which in the reverse mode of the engine is permeable and variable, and a liner wall of the engine, wherein a turbine exit cone having variable flaps is arranged upstream of the nozzle, said flaps being designed to vary the degree of flow blockage in the nozzle, and inner walls of the shroud are lined with a heat-resistant material.
2. A jet engine in accordance with Claim 1, wherein the flaps are pivotable about respective pivot axes.
3. A jet engine in accordance with Claim 1 or 2, wherein two or four flaps are provided in the turbine exit cone.
4. A jet engine in accordance with Claim 1, 2 or 3, wherein the flaps are concentric with the longitudinal centerline.
A jet engine in accordance with any one of the preceding claims, wherein the flaps are provided with hydraulic actuators mounted on a rear wall of a turbine exit casing and are shielded from hot air by means of a partition.
6. A jet engine substantially as herein described with reference to the accompanying drawings.

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