GB1182504A - Jet Propulsion Nozzle - Google Patents

Abstract

1,182,504. Jet propulsion nozzles. SOC. NATIONALE D'ETUDE ET DE CONSTRUCTION DE MOTEURS D'AVIATION. April 19, 1967 [April 20, 1966], No. 17901/67. Heading F1J. The invention relates to a propulsion nozzle for a jet engine which provides two coaxial jet streams. The nozzle comprises a central body 1, an inner casing 3 disposed around the central body and defining therewith an inner annular duct 2, and an outer casing 7 disposed around the inner casing and defining therewith an outer annular duct 6. The inner jet stream flows through the inner duct 2 and the outer jet stream flows through the outer duct 6. A set of angularly adjustable flap members 4 is mounted at the downstream end of the inner casing 3 the flaps being shown in the position in which they close off the inner duct 2 at the upper part of Fig. 1, and in the position in which they do not close off the duct 2 at the lower part of Fig.1. A further set of angularly adjustable flaps 8 is mounted at the downstream end of the outer casing 7. A further casing 11 is disposed around the outer casing 7 and defines therewith a cooling air duct 10. A set of angularly adjustable flap members 13 is disposed at the downstream end of the further casing 11, and a further set of angularly adjustable flaps 12 is provided on the further casing 11, the flaps being shown in the closed position at the upper part of Fig.1 whereby cooling air in the annular duct 10 discharges through the passage 18. The flaps 12 are shown in the open position at the lower part of Fig.1 whereby boundary layer air adjacent the outer surface of the further casing 11 may also flow into the passage 18 together with cooling air from the annular duct 10. In a second embodiment Fig.4 (not shown) the pivotal point of the flaps 4 is upstream of the pivotal point of the flaps 8 instead of being down-stream thereof as in Fig.1. In Fig.3 the invention is applied to a jet propulsion unit comprising a gas turbine jet engine 16 which supplies gases to the inner duct 2 and a ram jet unit 15 disposed in the outer duct 6. In the low speed range the gas turbine engine only is operative and the flaps 4 are open to allow exhaust gas flow through the duct 2. The flaps 8 are also open to allow air flow through the ram jet duct 6 and cooling air flow through the duct 10. In the high speed range the ram jet unit 15 only is operative and the flaps 4 are moved so as to close off the gas turbine exhaust duct 2 as shown in Fig.3. A further set of flaps 20 disposed at the upstream end of the inner casing 3 is also moved to close off the inlet to the gas turbine engine in the high speed phase. In a further embodiment Fig.6 the engine comprises a gas turbine jet of the by-pass type with high-pressure and low-pressure rotor assemblies; combustion equipment 15 is provided in the by-pass duct 6. In Fig.7 the engine is operating as a by-pass engine with no burning in the by-pass duct. The turbine exhaust gases discharge through the inner duct 2, the flaps 4 being positioned as shown; also the by-pass air stream discharges through the outer duct 6, the flaps 8 being positioned as shown. Cooling air also flows through the duct 10, the duct 10 not being shown in Fig. 7. In Fig.6 the combustion equipment 15 in the by-pass duct is operative and the flaps 4 are now positioned as shown. In Fig.5 which is the high speed mode of operation, the gas turbine engine is shut down, the flaps 4 being moved to close off the inner duct 2 and the flaps 20 also being moved to close off the inlet to the gas turbine engine. Ram air now passes to the outer duct 6 the combustion equipment 15 being operative and the engine operates as a ram jet unit.