Power plants – Reaction motor – Interrelated reaction motors
Patent
1995-09-08
1997-09-16
Freay, Charles G.
Power plants
Reaction motor
Interrelated reaction motors
60230, 60232, 60262, 23926529, F02K 306
Patent
active
056668023
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a turbine engine equipped with a thrust reverser, especially the type used on aircraft. More particularly, the invention relates to a turbine engine of the double flow type provided with a thrust reverser, and providing for area variation of the hot central nozzle.
BACKGROUND AND OBJECTS OF THE INVENTION
In order to reduce the landing distance of a jet engine powered aircraft, as well as to increase the margin of safety when the aircraft is landing on a wet or icy runway, aircraft jet engines are provided with thrust reversers in order to provide a braking thrust for the aircraft. Typically, such thrust reversers are formed by thrust reverser "doors" which are capable of pivoting between two positions about an axis which is transverse and substantially diametrical with respect to the jet of the engine.
The first position finds the doors in a stowed position, out of the direct path of the exhaust blast of the engine. In this position, the doors form the exhaust nozzle of the gas turbine engine so that the thrust of the engine is directly rearward, thereby producing the forward thrust of the aircraft. In the second position, the doors are pivoted about the pivot axis to a transverse, blast deflecting or deployed position, to intercept and redirect the jet blast and produce the braking thrust for the aircraft when needed.
The jet engines which utilize such thrust reversers are typically of the double jet type of gas turbine engines. Such engines comprise a central generator which emits a jet of hot gas, and an annular by-pass conduit surrounding the central generator, and through which passes a jet of relatively cold gas. In practice, the central or hot jet emits gas flow at a high temperature on the order of 500.degree. C. to 600.degree. C., while the by-pass flow is at a temperature considered relatively cold, i.e. on the order of 100.degree. C.
When a thrust reverser is used with such double flow engines, the thrust reverser re-directs in a forward direction the hot and cold flows, in order to produce the braking thrust. Since the hot, central flow impinges on the thrust reverser doors, they must be made of heat resistant material. In general, the material used for the thrust reverser doors is either steel or a titanium alloy. However, steel is a relatively heavy metal, and while titanium alloys are much lighter, they are considerably more expensive. Aluminum is a very desirable material for the thrust reverser doors, but because of the high temperature of the hot flow, aluminum cannot be used.
In the past, attempts to overcome the drawbacks of conventional double flow engines have been made, for example in U.S. Pat. Nos. 4,362,015 and 4,581,890. For example, it has been proposed to provide an obstruction in the nature of flaps for obstructing a portion of the discharge outlet area of the exit end of the by-pass conduit when the thrust reverser is deployed. According to U.S. Pat. No. 4,362,015, the flaps restrict the flow of cold gas in by-pass conduit. In U.S. Pat. No. 4,581,890, the flaps are said to briefly reduce the efficiency of the flow mixing and causing the cold by-pass flow to contact the structure of the reverser, which was thereby maintained at a lower temperature. More precisely, this prior system increased (in thrust-reversing mode) the value of the ratio of the total pressure of the by-pass flow (i.e. the cold flow) to the total pressure of the hot flow, so that only the cold flow impinges on the reverser doors, thereby enabling the use of aluminum alloy doors.
However, it has been found that when such systems are applied to turbine engines that significant drawbacks arise. In essence, tests have shown that the engine rating must be kept reduced in the reverse mode in order to avoid surging the engine and raising the skin temperature of the thrust reverser doors. This is particularly true when the central nozzle of the gas generator is of the mixer type. The limitations found in the prior art systems are primarily due to the means used to control the value of the
REFERENCES:
patent: 4362015 (1982-12-01), Fage
patent: 4581890 (1986-04-01), Giraud
patent: 5372006 (1994-12-01), Lair
Dutton, Jr. Harold H.
Freay Charles G.
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