JP4257578B2 - Exhaust nozzle for jet engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust nozzle for a jet engine including a convergent and divergent flap that forms a flow path of exhaust gas from an engine.
[0002]
[Prior art]
When operating a jet engine, it is known that not only the combustion efficiency in the combustor can be improved, but also the thrust efficiency can be improved by utilizing the combustion air flow (jet flow) in the exhaust nozzle arranged at the rear stage of the combustor. ing. A convergent / divergent (CD) type exhaust nozzle is employed as an exhaust nozzle for using the combustion airflow.
[0003]
FIG. 2 is a schematic cross-sectional view showing the structure of a CD type exhaust nozzle. The exhaust nozzle 20 has a plurality of strip-shaped flaps arranged side by side in the circumferential direction, and forms a flow path for exhaust gas C in which the cross-sectional area gradually decreases by inclining the downstream side radially inward. 21 and a plurality of strip-shaped flaps connected to the downstream side of the convergent flap 21 and arranged side by side in the circumferential direction of the exhaust gas C whose sectional area gradually increases by inclining the downstream side radially outward. It is comprised from the convergent flap 22 which forms a flow path. When the exhaust nozzle 20 is configured in this manner, the exhaust gas C flowing through the exhaust nozzle 20 is once throttled by the throat portion S formed by the connection point between the convergent flap 21 and the divergent flap 22, thereby increasing the Mach number. By accelerating to about 1 and then diverging, it is accelerated to supersonic speed, and thrust efficiency is improved. In addition, since the nozzle opening ratio that achieves optimum thrust efficiency according to each navigation speed is realized, there is an advantage that high thrust efficiency can be obtained over a wide navigation speed range.
[0004]
In the exhaust nozzle 20, the direction of the opening of the exhaust nozzle 20 can be changed by changing the plurality of flaps arranged side by side in the circumferential direction from an axially symmetric arrangement state to an asymmetric arrangement state. ing. For example, with the front ends of a plurality of flaps arranged in an axisymmetric manner, the rear ends are arranged in an asymmetrical arrangement from the axial symmetry, that is, by arranging the opening centers of the rear ends away from the axes, the orientation of the openings is changed from the axial direction Can tilt. Thus, by changing the direction of the opening of the exhaust nozzle 20, the thrust direction of the engine can be changed to an arbitrary direction, and the maneuverability of the aircraft can be improved. The technology related to the CD type exhaust nozzle described above is disclosed in the following Patent Document 1, Patent Document 2, Patent Document 3, Patent Document 4, and the like.
[0005]
[Patent Document 1]
JP-A-2-275050 [Patent Document 2]
JP-A-5-86979 [Patent Document 3]
Japanese Patent Laid-Open No. 10-103154 [Patent Document 4]
Japanese Patent Laid-Open No. 2000-310159
[Problems to be solved by the invention]
As shown in FIG. 2, the rear end of the convergent flap 21 and the front end of the divergent flap 22 are connected by a hinge 24, and this connecting portion has a certain degree of mechanism in order to ensure the degree of freedom of operation of the drive mechanism. It is necessary to allow a certain margin. However, when the nozzle is variably operated when the engine is started, stopped, or when the operating state is changed, the exhaust gas flow flowing in the exhaust nozzle 20 becomes unstable. This unstable exhaust gas flow and the presence of backlash cause the self-excited vibration of the connection, and this self-excited vibration of the connection affects the exhaust gas flow and causes vibration of the exhaust gas flow. Then, the vibration of the exhaust gas flow affects the entire nozzle and develops to the vibration of the entire nozzle, and the aircraft falls into a very dangerous state.
[0007]
The present invention has been developed to solve the above-described problems. That is, an object of the present invention is to provide an exhaust nozzle for a jet engine that can prevent the occurrence of structural vibration caused by the instability of the exhaust gas flow when the engine is started, stopped, and when the operating state is changed. For the purpose.
[0008]
[Means for Solving the Problems]
According to the present invention, a convergent flap that forms an exhaust gas flow path that is disposed behind the jet engine and that gradually decreases in cross-sectional area, and an exhaust gas flow path that is disposed behind the convergent flap and that increases in cross-sectional area gradually. An exhaust nozzle for a jet engine that forms a throat portion by an outlet-side flow path of the convergent flap and an inlet-side flow path of the divergent flap, and a rear end of the convergent flap A slot is provided to be separated from the front end of the divergent flap, and a plurality of connecting members are provided on the outer side of the tip of the divergent flap to be connected to the outer side of the rear end of the convergent flap by hinges. An intermediate member is disposed between the members, the connecting member, the middle Member, wherein the convergent flap and a space surrounded by said divergent flaps, to form a recessed space functions as a pressure damper for absorbing the turbulence of the exhaust gas stream flowing through the throat portion, a jet engine, characterized in that An exhaust nozzle is provided.
[0009]
In the present invention, since a slot portion is formed between the rear end of the convergent flap and the front end of the divergent flap so as to form a recessed space that can absorb the disturbance of the exhaust gas flow that flows through the throat portion. Even when the exhaust gas flow becomes turbulent and unstable due to the variable operation of the exhaust nozzle, this slot functions as a pressure damper and absorbs the turbulence of the exhaust gas flow, so when the exhaust gas flow passes through the throat part Does not cause throat vibration. Therefore, vibration of the exhaust nozzle can be suppressed by stabilizing the exhaust gas flow.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings.
[0011]
FIG. 1 is a schematic cross-sectional view of an embodiment of an exhaust nozzle for a jet engine according to the present invention. As shown in FIG. 1, the exhaust nozzle 10 is installed at the rear end of an engine (not shown).
[0012]
The exhaust nozzle 10 is an axially symmetric (circular cross-section) nozzle, and a plurality of strip-shaped flaps arranged side by side in the circumferential direction are inclined inward in the radial direction on the downstream side to thereby flow the exhaust gas C. And a plurality of strip-shaped flaps arranged on the downstream side of the convergent flap 1 and arranged in the circumferential direction by inclining the downstream side radially outward. A divergent flap 2 that forms a diffusion portion in the flow path of the exhaust gas C is provided. When the exhaust nozzle 10 is configured in this manner, the exhaust gas C flowing through the exhaust nozzle 10 is once throttled by the throat portion S formed by the outlet side flow path of the convergent flap 1 and the inlet side flow path of the divergent flap 2. And then accelerated to a supersonic speed by being diffused by the diffusion part of the divergent nozzle 2.
[0013]
The convergent flap 2 is supported by a driving means such as a hydraulic cylinder (not shown) provided on the outer periphery of the engine body at the rear end of the engine so as to be swingable about the swing shaft a1. Further, a connecting member 3 connected to the convergent flap 1 is provided on the outer side of the distal end portion of the divergent flap 2. The hinge 4 provided on the outer side of the rear end portion of the convergent flap 1 swings around the swing axis a2. The divergent flap 2 is movably connected and can be swung by driving means such as a hydraulic cylinder (not shown).
[0014]
As shown in FIG. 1, the exhaust nozzle 10 is provided with a slot portion 5 that forms a recessed space having a predetermined volume in the circumferential direction between the rear end of the convergent flap 1 and the front end of the divergent flap 2. Furthermore, an intermediate member (not shown) is provided between the connecting members 3 adjacent to each other and spaced from the slot portion 5 in the radially outward direction. That is, the annular recess space A is formed by the connecting member 3, the intermediate member, the convergent flap 1 and the divergent flap 2. The annular recess space A and the outer space of the exhaust nozzle 10 are appropriately sealed.
[0015]
As described above, when the nozzle is variably operated at the time of engine start, stop, and operation state change, the exhaust gas flow flowing in the exhaust nozzle becomes unstable, but the exhaust nozzle of the present invention Then, since the part which produces mechanical backlash, such as a hinge, in the throat part S is eliminated, even when the exhaust gas flow C in the throat part S becomes unstable, the vibration of the exhaust gas flow C in the throat part S is suppressed. it can.
[0016]
The reason why the vibration of the exhaust gas flow C in the throat portion S can be suppressed in this way is because the dent space A functions as a pressure damper. That is, when the exhaust gas flow C is disturbed and becomes unstable, the exhaust gas C existing in the vicinity of the slot portion 5 enters and exits the recessed space A and the exhaust nozzle 10 as shown by a bidirectional arrow in FIG. By doing so, the disturbance of this flow is absorbed. Thereby, generation | occurrence | production of the vibration of the whole nozzle can be prevented effectively. In addition, even if this slot portion 5 is provided, there is no great difference in terms of the nozzle mechanism, and there is little increase in parts due to the addition of such an exhaust gas flow stabilization mechanism, so that there is almost no cost penalty.
[0017]
In the above-described embodiment, an example in which the present invention is applied to an axially symmetric nozzle has been described. However, the present invention is not limited to this, and includes a pair of opposing flaps and a divergent flap. Needless to say, the present invention can be applied to a two-dimensional nozzle having a rectangular cross-sectional shape, and can be variously modified without departing from the gist of the present invention.
[0018]
【The invention's effect】
As described above, according to the exhaust nozzle for a jet engine of the present invention, it is possible to prevent the occurrence of structural vibration caused by instability of the exhaust gas flow when the engine is started, stopped, and when the operating state is changed. You can enjoy excellent effects such as
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of an embodiment of an exhaust nozzle for a jet engine according to the present invention.
FIG. 2 is a schematic cross-sectional view of a conventional exhaust nozzle for a jet engine.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Convergent flap 2 Divergent flap 3 Connection member 4 Hinge 5 Slot part 10 Exhaust nozzle A Recessed space C Exhaust gas S Throat part a1, a2 Swing axis

Claims (1)

A convergent flap that forms an exhaust gas flow path that is disposed behind the jet engine and that gradually decreases in cross-sectional area, and a divergent flap that is disposed behind the convergent flap and forms a flow path for exhaust gas that gradually increases in cross-sectional area. In an exhaust nozzle for a jet engine that forms a throat portion by an outlet side flow path of the convergent flap and an inlet side flow path of the divergent flap,
A slot portion is provided by separating a rear end of the convergent flap and a front end of the divergent flap,
Provided with a plurality of connecting members that are connected to the outside of the rear end of the convergent flap by hinges on the outer side of the tip of the divergent flap, and an intermediate member is arranged between the adjacent connecting members,
Said connecting member, said intermediate member, the space surrounded by said convergent flaps and said divergent flaps, to form a recessed space functions as a pressure damper for absorbing the turbulence of the exhaust gas stream flowing through the throat portion, that A featured exhaust nozzle for jet engines.

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