GB2068090A - Closure for ram-jets - Google Patents

Abstract

Closure for air inlet apertures 2 leading to a combustion chamber especially in a ramjet rocket propulsion engine with a pyrotechnically functioning striker device for the destruction of the closure at the end of the launching phase and at the beginning of the cruising phase of the engine, the cover being constructed as a hollow body 4 and consisting of a prestressed material such as glass, in which the prestressing in relation to the wall thickness decreases from the inside surface 4a towards the outside surface 4b, the pyrotechnic striker device 6, comprising charge 5 and balls 7, being situated in the interior of the hollow body. <IMAGE>

Description

SPECIFICATION Combustion chamber closure means primarily for the air inlet aperture of a rocket combustion chamber This invention relates to a destructible closure for an inlet duct communicating with a combustion chamber especially one in a rocket ramjet propulsion engine and a striker device for destroying the cover at the end of the launching phase and begining of the cruise phase, the striker being activated by generated pressures.

In a ramjet rocket engine, as disclosed in U.S.

Patent 3901028, a solid rocket propellant is provided for the launching phase which brings the projectile up to the high flight velocity required for operation of the ramjet to provide sufficient air at adequate pressure for the cruising phase. During the latter phase oxygen from the ar is caused to react in the combustion chamber with gases which have a high proportion of propellant and which are generated by a solid fuel. The chamber is followed by a convergent-divergent thrust nozzle serving to convert the pressure energy generated in the combustion chamber into reaction force.In order to ensure that the air inlet apertures leading into the combustion chamber will remain closed during the launching phase, the inlets are provided with closures of frangible material which, after the termination of the launching phase and at the commencement of the cruising phase, are destroyed by extraneous forces, so that the air inlet apertures are then unobstructed. Owing to the prevailing ram air pressure the fragments of the cover are forced out through the combustion chamber and the thrust nozzle. The closure may be destroyed by a pyrotechnic charge or mechanical striker device using a prestressed spring.

The difficulties arising are to ensure that the closure will be destroyed at the desired instant and caused to break-up into small fragments, so as not to cause damage to the projectile or internal parts of the propulsion unit or other projectiles in the vicinity.

This invention seeks to provide a closure with a material which, on the destruction of the cover, will not be detrimental to the safety of the engine unit or other projectiles used at the same time, and wherein the destruction of the cover will take place at a moment calculated in advance.

According to this invention there is provided a closure means for the air inlet aperture of a combustion chamber, the closure comprising a hollow body of a prestressed material of which the degree of prestressing in relation to the wall thickness decreases from the inside towards the outside, a pyrotechnic striker device being located within the interior of the body and serving to destroy the closure on activation.

Free destruction bodies, such as a large number of small balls, may be associated with the striker device.

The closure of this invention serves to seal the entry to the air inlet of a combustion chamber and disintegrates when destroyed into tiny fragments which cause no damage, owing to the nature of its material. Furthermore, the pyrotechnical activation of the striker device makes it possible to ensure that the destruction will take place at a precise instant. The striker device, in the form of a large number of separate balls, driven together by gass pressure, provides instant disintegration of the closure. The graduation of the prestressing of the material from the inside towards the outside produces a closure insensitive, from the outside, to normal mechanical stresses and thus representing a reliable sealing device, while it only affords little resistance to the intentional destruction from the inside.

An embodiment is shown as an example in the accompanying drawing.

Referring to the drawing the entry 1 to an air inlet duct 2 feeding a combustion chamber 3 is closed until the end of the launching phase of a projectile by a closure 4 of hollow construction. The closure is of a prestressed material, preferably an internally pre stressed glass.

Ordinary commercially available thermally prestressed glass such as that used for motor vehicle windscreens is preferred and this disintegrates into very small fragments when subject to mechanical overloading. This is a result of the high compressive stresses generated in the surface of the glass by the prestressing. The prestressing is usually effected by thermal treatment. Chemical treatments are also possible wherein sodium ions in the surface of the glass, for example, are replaced by calcium ions.

Glass is not the only material that can be thermally or chemically prestressed and processes can be applied to ceramic materials, for example aluminium oxide.

A striker means with a pyrotechnic charge 5 is built into the closure 4, with bodies such as metal balls 7 provided in the charge housing 6. The pyrotechnical charge 5 has an electric detonator 8 to which a firing circuit 9 is connected.

The material of the cover 4, as already mentioned, is prestressed and the prestressing being at a maximum on the internal surface 4a of the wall of the cover and decreasing towards the outside. On the outer surface 4b on prestressing is present. The cover 4, being a hollow body has the property of being insensitive to mechanical loads to which it is normally exposed from the outside, while from the inside it is immediately and easily destructible in its entirety by the balls 7 accelerated by the detonation of the charge 5.

1. Closure means for the air inlet aperture of a combustion chamber, the closure comprising a hollow body of a prestressed material of which the degree of prestressing in relation to the wall thick ness decreases from the inside towards the outside, a pyrotechnic striker device being located within the interior of the body and serving to destroy the closure on activation.

2. Closure means in accordance with Claim 1, wherein free destruction bodies are associated with the striker device.

3. Closure means in accordance with Claim 2,

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Combustion chamber closure means primarily for the air inlet aperture of a rocket combustion chamber This invention relates to a destructible closure for an inlet duct communicating with a combustion chamber especially one in a rocket ramjet propulsion engine and a striker device for destroying the cover at the end of the launching phase and begining of the cruise phase, the striker being activated by generated pressures. In a ramjet rocket engine, as disclosed in U.S. Patent 3901028, a solid rocket propellant is provided for the launching phase which brings the projectile up to the high flight velocity required for operation of the ramjet to provide sufficient air at adequate pressure for the cruising phase. During the latter phase oxygen from the ar is caused to react in the combustion chamber with gases which have a high proportion of propellant and which are generated by a solid fuel. The chamber is followed by a convergent-divergent thrust nozzle serving to convert the pressure energy generated in the combustion chamber into reaction force.In order to ensure that the air inlet apertures leading into the combustion chamber will remain closed during the launching phase, the inlets are provided with closures of frangible material which, after the termination of the launching phase and at the commencement of the cruising phase, are destroyed by extraneous forces, so that the air inlet apertures are then unobstructed. Owing to the prevailing ram air pressure the fragments of the cover are forced out through the combustion chamber and the thrust nozzle. The closure may be destroyed by a pyrotechnic charge or mechanical striker device using a prestressed spring. The difficulties arising are to ensure that the closure will be destroyed at the desired instant and caused to break-up into small fragments, so as not to cause damage to the projectile or internal parts of the propulsion unit or other projectiles in the vicinity. This invention seeks to provide a closure with a material which, on the destruction of the cover, will not be detrimental to the safety of the engine unit or other projectiles used at the same time, and wherein the destruction of the cover will take place at a moment calculated in advance. According to this invention there is provided a closure means for the air inlet aperture of a combustion chamber, the closure comprising a hollow body of a prestressed material of which the degree of prestressing in relation to the wall thickness decreases from the inside towards the outside, a pyrotechnic striker device being located within the interior of the body and serving to destroy the closure on activation. Free destruction bodies, such as a large number of small balls, may be associated with the striker device. The closure of this invention serves to seal the entry to the air inlet of a combustion chamber and disintegrates when destroyed into tiny fragments which cause no damage, owing to the nature of its material. Furthermore, the pyrotechnical activation of the striker device makes it possible to ensure that the destruction will take place at a precise instant. The striker device, in the form of a large number of separate balls, driven together by gass pressure, provides instant disintegration of the closure. The graduation of the prestressing of the material from the inside towards the outside produces a closure insensitive, from the outside, to normal mechanical stresses and thus representing a reliable sealing device, while it only affords little resistance to the intentional destruction from the inside. An embodiment is shown as an example in the accompanying drawing. Referring to the drawing the entry 1 to an air inlet duct 2 feeding a combustion chamber 3 is closed until the end of the launching phase of a projectile by a closure 4 of hollow construction. The closure is of a prestressed material, preferably an internally pre stressed glass. Ordinary commercially available thermally prestressed glass such as that used for motor vehicle windscreens is preferred and this disintegrates into very small fragments when subject to mechanical overloading. This is a result of the high compressive stresses generated in the surface of the glass by the prestressing. The prestressing is usually effected by thermal treatment. Chemical treatments are also possible wherein sodium ions in the surface of the glass, for example, are replaced by calcium ions. Glass is not the only material that can be thermally or chemically prestressed and processes can be applied to ceramic materials, for example aluminium oxide. A striker means with a pyrotechnic charge 5 is built into the closure 4, with bodies such as metal balls 7 provided in the charge housing 6. The pyrotechnical charge 5 has an electric detonator 8 to which a firing circuit 9 is connected. The material of the cover 4, as already mentioned, is prestressed and the prestressing being at a maximum on the internal surface 4a of the wall of the cover and decreasing towards the outside. On the outer surface 4b on prestressing is present. The cover 4, being a hollow body has the property of being insensitive to mechanical loads to which it is normally exposed from the outside, while from the inside it is immediately and easily destructible in its entirety by the balls 7 accelerated by the detonation of the charge 5. CLAIMS

1. Closure means for the air inlet aperture of a combustion chamber, the closure comprising a hollow body of a prestressed material of which the degree of prestressing in relation to the wall thick ness decreases from the inside towards the outside, a pyrotechnic striker device being located within the interior of the body and serving to destroy the closure on activation.

2. Closure means in accordance with Claim 1, wherein free destruction bodies are associated with the striker device.

3. Closure means in accordance with Claim 2, wherein the destruction bodies comprise a plurality of balls.

4. Closure means in accordance with any preceding claim wherein the hollow body comprises prestressed glass.

5. Closure means as described herein with reference to the drawing.