FR2696784A1 - Shutter, for propulsive nozzle - is opened by bellows operated by pressure difference between propulsive chamber pressure and reference pressure of internal volume of these bellows - Google Patents

Abstract

The nozzle shutter is constructed with a cavity (20), formed by the body of the device, and which has the external faces (23) in contact with an internal surface (24) of the nozzle (10). Beneath the cavity is attached an air tight elastic bellows (34), of which the internal volume is set at a reference pressure. The difference in pressure between the reference pressure and the propulsion chamber pressure produces a displacement which in turn causes the opening of the shutter (40), which is closing off the cavity (20). The shutter remains open until the pressure difference becomes zero. USE/ADVANTAGE - It provides a simple and reliable shutter, which provides effective sealing of the propulsion chamber.

Description

Thruster nozzle shutter
Field of the invention.

 The present invention relates to a nozzle shutter, the implementation of which can be carried out at the level of any powder or liquid propellants, whether they are aircraft, spacecraft or satellite propellants or even missiles or rockets. powder or biliquid type propellants.

Prior art.

 Conventionally, the shutters essentially seek to avoid any pollution inside the propellant chamber of the engine and to ensure a seal during storage.

 The first of these problems finds its solution in the use of permeable membranes, filters or cloths, sealing the diverging part of the engine and thus ensuring insulation of the chamber and of the injection or catalysis device with respect to external impurities, such as dust, which may cause the engine to malfunction.

 The answer to the storage leakage problem is given by the use of engine shutter membranes, in particular elastomer plugs, which are broken and ejected when the engines are first started.

 Patent FR-1 179567 attempts to provide a solution to these problems by disclosing a shutter in the form of a sail nut screwing onto the diverging portion of the nozzle of a jet propellant. This system, however, seems hardly capable of limiting pollution.

 In addition, in particular in the case of monergol or liquid bi-propellant engines, to optimize operating precision or reinforce reliability, it is necessary to proceed before filling the lines with propellant and switching on the engines when draining air or gases contained in the supply lines of these engines as well as of the engine itself.

 In addition to the use of floor emptying by a vacuum pump, a conventional solution consists in equipping the supply pipes of engines with specific devices, such as electric valves, thus making it possible to ensure this emptying in flight and thus eliminating any gas bubble that may exist in these pipes and is likely to affect the proper functioning of the engine. However, the engine itself needs to be drained.

 To date, there are no devices capable of fully solving all of the above problems, the permeable membranes not ensuring a sealing function during storage and the plugs and other plugs not allowing emptying before their ejection through the motors.

Subject and brief description of the invention
An object of the present invention is to provide a nozzle obturator allowing both a storage and impurity seal and an above-ground drain of the supply pipes as well as of the motors.

 Another object of the invention is to provide a simple and reliable device, the mounting of which is ensured without the use of complex apparatus.

 These objects are achieved by a propellant nozzle obturation device comprising a cavity forming the body of the device and the external faces of which are in contact with an internal surface of the nozzle and at the bottom of which is an elastic bellows sealed against the '' inside which prevails a determined reference pressure and whose displacement, for a pressure inside the given combustion chamber, causes, from a pressure level outside this determined chamber, 1 'opening a closure element initially closing this cavity, this closure element remaining open when the pressure difference between the interior and the exterior of the combustion chamber has become zero.

 Protection against impurities and humidity is total and the seal during storage is perfect. In addition, the device according to the invention allows automatic emptying in flight, from a certain level of external pressure, of the propellant chamber and of the supply lines of the motors (provided that the valves 'injection of the engine), this emptying being moreover possible on several occasions thanks to the reversibility of the system, which represents another advantage compared with the irreversible devices of the prior art.

 In a first configuration, the cavity is turned towards the outside of the nozzle. The shutter element located downstream thereof is then subjected on the one hand to the external pressure and on the other hand to the pressure prevailing in the propellant chamber which is also exerted inside this cavity .

 In a second configuration, the cavity is turned towards the inside of the nozzle. The shutter element located upstream thereof is then subjected on the one hand to the pressure prevailing in the propellant chamber and on the other hand to the external pressure which is also exerted inside this cavity .

 This double configuration makes it possible to adapt the device to any type of engine and to choose the most interesting configuration according to the components available.

 Advantageously, the reference pressure determined corresponds to zero pressure.

 The use of a device provided with an aneroid capsule allows better controllability of the shutter, in particular in the event of failure of this capsule, the open position of the shutter element then being easily detectable.

 a sealing zone is formed between the shutter and the combustion chamber, this sealing being effected by bonding of at least one of the walls of the cavity with the internal surface of the nozzle.

 The simplicity of the connection of the shutter with the nozzle of the engine avoids the need for complex and expensive apparatus and facilitates the use of such a device.

 Preferably, the sealed elastic bellows comprises guide sleeves intended to prevent any flapping of the closure element during opening or in the open position.

 Likewise, greased O-rings can be placed between the guide elements and provide a viscous damping of the displacement of the closure element.

 According to an alternative embodiment, the closure element comprises a guide element intended to cooperate with the internal surface of the cavity in order to avoid any flapping of the closure element.

 As before, a greased O-ring can be placed between the guide element and the internal surface of the cavity to ensure a viscous damping of the displacement of the closure element.

 According to another variant, the shutter element is guided by the body of the device which comes into direct contact or by means of a greased seal with the connecting element secured to this shutter element.

 Finally, it is preferable to provide the shutter with a stop intended to limit the opening of the movement of the shutter element.

 A stop in the closed position also makes it possible to limit the work of the sealing zone in the event of high external pressure.

Brief description of the drawings.

Other characteristics and advantages of the present invention will emerge more clearly on reading the description which follows, given by way of non-limiting example, with reference to the appended drawings in which:
FIG. 1 shows in a simplified manner an assembly for supplying propellant to a rocket engine,
FIG. 2 represents a first embodiment of a shutter according to the invention,
FIG. 3 shows a characteristic curve of the theoretical sealing of the shutter in the first embodiment of the invention,
- Figure 4 shows the variations in operation of the internal and external pressures acting on the shutter according to the invention.

FIG. 5 represents a second embodiment of the shutter according to the invention,
FIG. 6 shows a characteristic curve of the theoretical sealing of the shutter in the second embodiment of the invention,
- Figures 7a, 7b, 8a, 8b, 9a, 9b, 10a, 10b show guide and damping means intended to limit the beating and the movement of the shutter member of the shutter.

Detailed description of particular embodiments.

 Figure 1 shows in a simplified manner a propellant supply system of a spacecraft engine provided with a shutter of the prior art.

 The propellant chamber or thrust chamber 1 of the engine is supplied with propellant through the supply lines 2 from at least one propellant tank 3 with gas / liquid phase separation 4 or fitted with a separation device phase, the pressurization of this tank being provided by a conventional pressurization system, for example a small helium 5 tank and regulation means not shown. Valves 6 arranged on the supply lines make it possible, for example, to ensure sealed storage of the propellants of the reservoir 3.

Once opened, this valve ensures the flow of the flow necessary for the supply.

This supply of propellant is carried out by injection valves 8 disposed at an injection plate 9 placed at one end of the combustion chamber 7, the other end being provided with a convergent-divergent assembly forming a nozzle of this engine. Inside this nozzle 10 is placed a shutter device, an elastomeric plug 11 for example, fixed to the free end of the nozzle and ensuring a seal of the combustion chamber 7.

 Such a device, if it makes it possible to ensure a seal during storage or against impurities, cannot in any way drain the air contained in the engine propellant supply lines which, in this case, cannot be brought into the open air in flight only by the use of specific valves placed on these lines.

 Figure 2 shows a first embodiment of a nozzle closure device according to the invention.

 The device comprises a cavity 20 whose walls form the body of the device and which is intended to be placed inside the nozzle 10 of the engine, the axis of this cavity coinciding with the axis of the nozzle. This cavity may have a frustoconical shape like that of the nozzle or any other shape, for example cylindrical, provided that it is connected in a substantially rigid and sealed manner to this nozzle.

 In the exemplary embodiment of FIG. 2, the cylindrical cavity 20, the opening of which is directed towards the outside of the nozzle 10, comprises, at its two ends, upstream 21 and downstream 22 radial walls extending radially from the cylindrical external face 23 of this cavity and coming into contact with the internal surface 24 of the nozzle 10. A fixing 25, for example by means of an adhesive, of the circumferential part of at least the downstream radial wall 22 with the internal surface of the nozzle, ensures a sealing zone between the shutter and the engine.

 On the bottom 26 of the cavity 20 is fixed by one of its faces 29 a sealed elastic bellows 30, the other face 31 being connected by a connecting element 32 to a closing element 40 coming from, in a position of closing, wear on the downstream radial wall 22 and thus close the cavity 20 whose internal atmosphere is then isolated from the outside. The connection of the lower and upper faces 29, 31 with the elastic bellows 30 can simply be carried out by a weld 33, the assembly forming in a way a deformable capsule 34 inside which a determined reference pressure can be fixed. Thus, an axial orifice 35 formed, for example in the underside 29 of the capsule, will easily make it possible to evacuate therein and transform this capsule into an aneroid capsule, a ball 36 fixed by welding then closing the end of this orifice and fix the internal reference pressure in the capsule at this zero pressure.

 Openings 37 to 39 are made respectively at the upstream radial wall 21, the external cylindrical face 23 and the connecting element 32 in order to subject all the external walls of the capsule 24 to the upstream pressure, that is that is to say the pressure prevailing at the combustion chamber 7 of the engine.

 The shutter element 40 is itself subjected on the one hand to this upstream pressure denoted P1 thereafter, which is exerted on its internal face 41 and to the downstream pressure denoted P2 thereafter, that is to say that is to say at the pressure prevailing outside the motor, which is exerted on its external face 42. It can advantageously be made in a thermosetting resin or in a material of the plexiglass type so as to be able to easily control its positioning relative to the radial wall 22 serving as a support.

 The contact between this wall and the closure element will preferably take place on an annular surface 43 forming a rim at the end of this element 40, the wall being provided at the location of this surface with a ring made in a material with a low coefficient of friction.

 The operation of such a nozzle shutter will now be described with reference to FIGS. 3 and 4.

FIG. 3 shows the characteristic curve of the theoretical sealing of the shutter according to the invention. For a given dimensioning of this shutter, which depends on the various components constituting it, in particular on the internal pressure of the capsule or on the various effective sections on which the internal P1 and external pressure forces P2 are exerted on the combustion chamber, the characteristic theoretical sealing 60 separates the plane defined by the upstream pressures P1 and downstream P2 into two zones, one I corresponding to the closure element in the closed position and therefore to a sealed shutter and the other II corresponding to this shutter element in the open position, the shutter then being leaktight. It is important to note that, when the upstream pressure is equal to the downstream pressure and also equal to zero pressure (P1 = 0), the shutter element is in the open position. This position is maintained, at zero upstream pressure, for any downstream pressure, therefore external to the chamber P2, less than a pressure
P2 * positive and determined.

 Figure 4 shows in the plane defined in Figure 3 the evolution of an operating point representative of the pressure variations at the shutter.

When the propellants are stored on the ground in the engines, the external pressure
P2 is the atmospheric pressure Pat, fixing the operating point for example at A in the predefined zone I in which the shutter is sealed.

 In flight, the external pressure P2 changes and tends to decrease with altitude.

 Up to a threshold defined by the theoretical reference B, the shutter is sealed and therefore the pressure in the combustion chamber P1 remains constant and equal to its original value (that at A). From this threshold B, the operating point enters zone II in which the shutter is no longer sealed and its evolution then depends on the internal characteristics of the chamber and of the supply lines of the engine when the valves injection are open. FIG. 4 shows, by way of indication, three examples of paths, passing through C, D or E for the displacement of the operating point and depending on the respective decreases in pressures P1 and P2.

 The opening of the shutter, under the action of external pressure forces, thus allows the emptying of the chamber and that of the engine supply pipes, the opening of the shutter (its non-sealing) being of the greater the lower the external pressure. In the extreme, when the external pressure P2 is almost zero (high altitude) and that in the chamber P1 is almost zero at the end of emptying, the operating point is fixed at F.

 It can be noted that with such a device, any leaks which may appear in flight at the junction between the engine and the shutter have no effect on the normal operation of the shutter, the opening of which must increase with the drop in outside pressure.

 Returning to FIG. 1. A simple modeling of the device can be made by considering the bellows as a deformable capsule without elastic stiffness containing a purely elastic spring, the point of contact between the closure element 43 and the downstream radial wall 42 being modeled by a very stiff spring.

 Under these conditions, the examination of the general equation of the shutter according to the invention shows that it is possible by intervening on the different variables involved (maximum lifting of the shutter element, maximum section of opening, maximum closing force, choice of bellows, etc.) to precisely define the characteristic curve of the theoretical seal mentioned above and thus determine, for a given chamber pressure, the external pressure level below which l the shutter is no longer waterproof. This pressure level is easily adjustable, especially for different types of mission, and can be determined with precision. A value of the order of 0.5 bar seems appropriate for an orbiting or ballistic flight mission.

 FIG. 5 shows a second embodiment of a nozzle obturator according to the invention in which a cavity 200 whose walls form the body of the device is turned towards the inside of the engine. As in the previous embodiment, this cavity 200 has upstream 210 and downstream 220 radial walls extending from the cylindrical external face 230 of the cavity. A bonding zone 250 providing a seal between the combustion chamber 7 and the outside is present at least between the circumferential part of the upstream radial wall 210 and the internal surface 24 of the nozzle 10.

 A waterproof elastic bellows 300 is fixed by its lower face 290 to the bottom 260 of the cavity 200, which to allow the mounting of the bellows from the outside can be removable, its upper face 310 being connected by a connecting element 320 to an element shutter 400 coming, in a closed position, bear on the upstream radial wall 210 and thus isolate the combustion chamber 7 from the internal atmosphere of the cavity 200 inside which prevails the external pressure.

 In fact, openings 370 to 390 are made respectively at the level of the downstream radial wall 220 or of the bottom 260, of the external cylindrical face 230 and of the connecting element 320, in order to subject this cavity to the pressure prevailing at l outside the combustion chamber. The bellows and its lower and upper faces form a deformable capsule 340 inside which a determined reference pressure can be fixed produced from the orifice 350 formed in the lower face 290 of the bellows. As before, a ball 360 fixed for example, by brazing to the external end of this orifice, can ensure sealing to leave the capsule under pressure (or even under vacuum).

 The operation of this alternative embodiment is analogous to that of the embodiment of FIG. 2. The theoretical sealing characteristic curve 70 of this shutter however has, unlike the previous one, a negative slope (see FIG. 6). We also find zones I and II in which the shutter is respectively waterproof and non-waterproof, this characteristic like the previous one having a value at the origin strictly positive, that is to say allowing the opening of the shutter , at a pressure in the chamber P1 less than P1 * or zero, for a pressure less than P2 than a pressure P2 * of a determined positive value and thus ensuring total emptying of the chamber.

 By taking again the hypotheses formulated previously, the general equation of this obturator can be determined simply and from this one can dimension the obturator so that one can obtain starting from a determined external pressure level , for example P2 * equal to 0.75 bar for a pressure in the combustion chamber of 1 bar, an automatic emptying in flight of this chamber and of the supply lines of the engines when the injection valves are open.

 Note that, for this example and for this embodiment with an internal pressure at the bellows zero, these conditions impose for correct operation an effective section of the bellows strictly larger than the section of the closure element subjected to the pressure P1 whereas in the context of the previous embodiment, with these same conditions, it was necessary for the effective section of the bellows to exceed at least a quarter of the passage section of the closure element subjected to the pressure P1.

 Figures 7a, 7b, 8a, 8b, 9a, 9b, 10a, 10b show different types of possible guidance to avoid possible flapping of the shutter element.

 In FIGS. 7a and 7b, this guidance is carried out in the capsule 34, 340 by two sleeves 44,45; 440,450 fitting one inside the other, and each secured to one side of the bellows forming this capsule.

 A passage 46, 460 made for example in the sleeve 45 integral with the upper face 31, allows communication between the different spaces of this capsule 34,340.

 Figures 8a and 8b show an alternative embodiment in which greased annular O-rings 47,48; 470,480 are interposed between the two sleeves to thereby create additional viscous damping.

 In FIGS. 9a, 9b and 10a, 10b, the shutter element is guided no longer inside the bellows but on the body of the shutter.

 In FIGS. 9a and 10a, the guidance is carried out by an annular sleeve 49 integral with the closure element 40 and sliding, directly or by means of a greased O-ring seal, against the internal cylindrical surface 50 of the cavity. A passage 52 is made in the sleeve 49 to ensure, when the closure element 40 is opened, the progressive communication or not of the combustion chamber with the outside.

 In FIGS. 9b and 10b, the guidance is carried out on the connecting element 320 by the extension of the upstream radial wall 210 until contact with this element, this contact possibly being direct or by means of a seal. greased 510. As for the embodiments of FIGS. 9a and 10a which correspond to the first embodiment of the invention, the embodiments of FIGS. 9b and 10b, which relate to the second embodiment, incorporate a passage 520 in the extension of the wall radial 210 for, once the closure element 400 is open, ensuring communication between the combustion chamber and the outside.

 The guides produced in the capsule (FIGS. 7a, 7b and 8a, 8b) have the advantage of being confined in a sealed environment (that which prevails in the capsule) and therefore of being much more reliable.

 In order to avoid excessive movement of the bellows 34, 340, it is possible to install stops integral with the body of the device, or even with the bellows. FIG. 7a shows for example such a stop 53 disposed towards the inside of the cavity in the extension of the downstream radial wall 22. Likewise, FIG. 9b shows a stop 530 arranged opposite the upper face 310 of the bellows.

 In both cases, when the closure element is opened, the stop will have the effect of limiting the expansion of the bellows and at the same time that of the closure element.

 The shutter according to the invention, as it could be demonstrated previously, therefore provides both total protection against impurities or humidity and a seal during storage, but in addition it allows automatic emptying in flight, from of a certain level of external pressure, of the combustion chamber and of the engine supply lines, which, by avoiding the presence of any gas bubble in these lines, optimizes the operating precision of the engine and ensures it reproducible ignitions. It should also be noted that this emptying is possible several times due to the total reversibility of the device, the opening or closing of the shutter being carried out below or above the predefined external pressure level, the determination of which can be calculated with great precision.

 In addition, due to this reversibility, the device can be precisely controlled in its manufacturing cycle, in particular as regards the predefined external pressure level. As a result, this pressure level can even be adjustable during manufacturing.

Claims (12)

 1. A propellant nozzle obturation device, characterized in that it comprises a cavity (20,200) forming the body of the device and the external faces (23,230) of which are in contact with an internal surface (24) of the nozzle ( 10) and at the bottom of which is fixed a tight elastic bellows (34,340) inside which a determined reference pressure prevails and whose displacement, for a pressure inside the given combustion chamber, causes, from a pressure level outside this determined chamber, the opening of a closure element (40,400) initially closing the cavity (20,200), this closure element remaining open when the pressure difference between l he interior and exterior of the combustion chamber became zero.  2. obturation device according to claim 1, characterized in that the cavity (20), directed towards the outside of the nozzle (10), is subjected to the pressure of the combustion chamber, the obturation element (40) located downstream of the nozzle and limiting downstream this cavity being subjected to external pressure.  3. Sealing device according to claim 1, characterized in that the cavity (200), directed towards the inside of the nozzle (10), is subjected to the pressure external to the combustion chamber, the element of obturation (400) located upstream of the nozzle and limiting upstream this cavity being subjected to the internal pressure of the chamber.  4. Sealing device according to any one of claims 1 to 3, characterized in that said determined reference pressure corresponds to zero pressure.  5. Sealing device according to any one of claims 1 to 4, characterized in that a sealing zone is formed between the shutter and the combustion chamber, this sealing being produced by gluing (25,250) at least one of the walls (22, 220) of the cavity (20,200) with the internal surface (24) of the nozzle (10).  6. obturation device according to any one of claims 1 to 5, characterized in that the waterproof elastic bellows (34,340) comprises two guide sleeves (44,45; 440,450), one linked to the body of the device and the other moving with the closure element and intended to avoid any flapping of the closure element.  7. Sealing device according to claim 6, characterized in that it further comprises greased O-rings (47,48; 470,480) disposed between the guide sleeves and ensuring a viscous damping of the movement of the element shutter.  8. obturation device according to any one of claims 1 to 5, characterized in that the obturation element (40) comprises an annular guide element (49) intended to cooperate with the internal surface of the cavity ( 50) in order to avoid any flapping of the closure element.  9. obturation device according to claim 8, characterized in that it further comprises a greased O-ring (51) disposed between the annular guide element (49) and the internal surface of the cavity (50) to ensure viscous damping of the displacement of the closure element.  10. Sealing device according to any one of claims 1 to 5, characterized in that the guiding of the shutter element (400) is produced by the body of the device which comes into direct contact or through a greased seal (510) with the connecting element (320) integral with this closure element.  11. obturation device according to any one of claims 1 to 10, characterized in that it further comprises at least one stop (53,530) intended to limit the opening of the displacement of the obturation element ( 40,400).  12. Device according to any one of claims 1 to 10, characterized in that it also comprises at least one stop (54) intended to limit the work of the sealing zone (43) in the event of strong external overpressure .