GB2197045A

GB2197045A - Injector

Info

Publication number: GB2197045A
Application number: GB08722230A
Authority: GB
Inventors: Claude Girard; Michel Bridou; Gerard Passagot
Original assignee: Societe Europeenne de Propulsion SEP SA
Current assignee: Societe Europeenne de Propulsion SEP SA
Priority date: 1986-09-26
Filing date: 1987-09-22
Publication date: 1988-05-11
Anticipated expiration: 2007-09-22
Also published as: GB2197045B; FR2604373B1; FR2604373A1; GB8722230D0

Abstract

The composite injector (100) comprises an outer sleeve (10) made of a material which is a poor heat conductor, and an internal nozzle (20) separated from the sleeve (10) by a heat barrier space (31,32). The outer sleeve (10) has a cylindrical rear part (17) of small thickness, one end of which is assembled in tight manner on the rear part (23) of the nozzle (20) by means of a welding bead (27) creating stresses on the nozzle which tend to apply the tip (33) of the nozzle against the inner front part (16) of the outer sleeve, The injector is intended for use in a corrosive, high temperature environment, particularly for injecting sulphur hexafluoride into an enclosure containing lithium. <IMAGE>

Description

SPECIFICATIO Composite injector for introducing a first corrosive product into an enclosure containing a second corrosive product The present invention relates to a composite injector for introducing a first chemical product which becomes corrosive when heated above a certain temperature, such as sulphur hexafluoride or its decomposition products, into an enclosure containing a second chemical product heated to a high temperature and equally corrosive at that temperature, such as lithium, comprising, on the one hand, an outer sleeve which is joined to the walls of the enclosure, and of which the part which is exposed to the second chemical product contained inside the enclosure, is made from a material which is resistant under heat to that second chemical product and to its reaction products with the first chemical product, and on the other hand, inside the sleeve, a nozzle produced in a material which is chemically resistant to the first product and to its decomposition products and which is provided with an injection duct having at least one outlet issuing opposite at least one perforation made in the sleeve, a free space forming a heat barrier over the major part of the outer face of the nozzle situated opposite the sleeve.

An injector of this type is described in Applicant's French Patent No. 2 498 946.

To achieve tightness at the level of the heat barrier and to prevent the chemical product from penetrating into the clearance which exists between the nozzle and the outer sleeve, tightness means have to be used which, according to the aforesaid patent, are preferably constituted by one or more annular pieces compressed between the nozzle and the sleeve around and in extension of the outlet of the injection duct. The added annular piece or pieces must form a joint to obtain a permanent and reliable tightness.

It is therefore understandable that the use of added annular pieces or of a spring exerting an action on the back of the nozzle are embodiments which are ill-adapted to the massproduction of products required to show great qualities of strength, especially as when a spring is provided at the back of the nozzle, it is difficult to avoid having to use a conventional annular joint between the back of the nozzle and the sleeve.

It is precisely the object of the invention to eliminate the aforesaid drawbacks and to produce a composite injector of simpiified structure, hence of reduced cost and reduced overall dimensions, which shows qualities of great reliability of operation and increased strength.

These objects are reached with a composite injector of the type described hereinabove, wherein the outer sleeve is produced in a material which is a poor conductor of heat, has a cylindrical rear part of small thickness, the free end of which is assembled in tight manner on the back of the nozzle by means of a welding bead creating on the nozzle, stresses which tend to apply the downstream part of said nozzle against the inner wall of the outer sleeve.

Preferably, the free space which forms a heat barrier, stretches around the nozzle over the entire area situated opposite the thickerwalled part of the outer sleeve, and said outer sleeve is essentially in contact with the nozzle by its thinner cylindrical rear part.

According to one advantageous embodiment, the nozzle comprises an insert in a refractory material which is also a good conductor of heat, said insert being placed at the downstream end of the nozzle and, in the axis thereof, the downstream end of the injection duct being provided in said insert and said insert defining the outlet, of which the edge bears directly onto the inner front face of the sleeve by a zone of reduced area, around the perforation provided in the outer sleeve.

The insert can be made, for example, of tungsten whereas the rest of the nozzle body is made of a material such as stainless steel or nickel.

The insert is preferably assembled by brazing in the nozzle body.

The nozzle body can be provided on its periphery and inside its downstream part with an annular guiding part in contact with the inner face of the sleeve over a small surface and defining a first free space between the front face of the nozzle and the inner front face of the sleeve, and a second free space between the peripheral wall of the outer sleeve and the inner face of the thicker peripheral wall of the sleeve.

The invention will be more readily understood on reading the following description with reference to the drawings, in which: Figure 1 is a diagrammatical view of an axial section of an injector according to-the invention, Figure 2 is a detailed view of Figure 1, on an enlarged scale, and showing the downstream end of the nozzle according to one particular embodiment of the invention, and Figure 3 is a detailed view similar to that shown in Figure 1 but according to a second embodiment of the invention.

Referring first to Figure 1, this shows, mounted on the wall 1 of an enclosure, an injector 100 for injecting for example gaseous sulphur hexafluoride inside an enclosure already containing lithium, for example.

The injector is essentially constituted by an outer sleeve 10 inside which is inserted a nozzle 20 provided with an axial central injection duct 24. The outer shell 10 comprises a lateral portion 11 which is for example cylindrical and a downstream end 12 with an inner face 16. Said outer shell 10 is made from a material capable of resisting the product contained inside the enclosure and the reaction products thereof. In the case where the enclosure contains lithium, the sleeve 10 can, like wall 1, be in stainless steel.

The nozzle 20 is also produced from a material capable of resisting, up to a certain temperature, the attack of the injected product or of the decomposition products thereof.

Outer sleeve 10 comprises a relatively thick cylindrical lateral wall 11 extended rearwardly by a cylindrical wall 17 of smaller thickness.

The body of the nozzle 20 in turn presents in its downstream part, an outer wall 22 of diameter smaller than that of the inner face 15 of sleeve 10, this in order to leave an annular free space 32 which forms a heat barrier.

Similarly, a free space 31, which also forms a heat barrier, is provided between the front face 21 of the nozzle and the inner front face 16 of the sleeve. On the other hand, the diameter of the nozzle body 20, in the rear part 23 of said nozzle situated opposite the cylindrical wall 17 of reduced thickness, is adapted to the inner diameter of sleeve 10.

The free end of the cylindrical wall 17 of sleeve 10 can also be welded on the rear part 23 of the nozzle 20 in order to set up a metallic continuity between the nozzle 20 and the sleeve 10, without it being necessary to insert a joint between the nozzle 20 and sleeve 10. The welding 27 further creates stresses within the material, these stresses tending to apply the tip 33 of the nozzle 20 against the inner wall 16 of the front face 12 of sleeve 10, and by doing so, ensuring tightness by a permanent metal-over-metal contact in a zone of reduced surface area around the outlet 25 of the nozzle and the perforation 13 of the sleeve 10.

Because of the existence of a contact zone of reduced surface area between the tip of the nozzle 20 and the sleeve 10, of free spaces 31, 32 forming a heat barrier between the downstream part of the nozzle 20 and the sleeve 10 of the contact of the rear part 23 of the nozzle 20 with a cylindrical wall 17 of smaller thickness and made of a material which is a poor heat conductor, thus forming an important heat barrier, the heat prevailing at the level of the front part 12 of the sleeve 10 cannot be transmitted by conduction towards the nozzle 20.

The welded joint 27 between the rear part 17 of the sleeve 10 and the nozzle 20 improves the tightness with respect to the surroundings, while preventing the use of conventional joints which are known not to stand up well to the heat, and of springs or other pre-stressing means, thereby preserving the efficiency of the heat barrier generated by the recesses provided between the nozzle 20 and the sleeve 10.

A collar 26 can be formed at the level of the peripheral part of the nozzle 20 in its downstream part, for guidingothe nozzle 20 inside the sleeve 10 and preserving the coaxiality of the axes of the duct 24 and of perforation 13 throughout assembly. Collar 26 bears against the inner face 15 of the sleeve 10 over a very small surface area.

According to one advantageous feature, the end part 24a of injection duct 24 of the nozzle is produced in a different material from that constituting the rest of the nozzle. A cylindrical insert 28 is then placed in the axis of the nozzle 20 and in its downstream part.

Insert 28 is perforated longitudinally in the extension 24a of injection duct 24, and thus carries the outlet 25 of injection duct 24, 24a.

The nozzle body 20 is assembled with insert 28 by high temperature brazing on the peripheral cylindrical surface 29 of insert 28.

If sulphur hexafluoride (SF6) is to be injected, the insert 28 is advantageously produced from tungsten which, besides showing a good resistance to corrosion caused by the SF6, has a very high melting point and a low coefficient of expansion. Such refractory metal properties make the tungsten particularly well suited for the production of the nozzle tip 33 in front of which is situated the flame of the chemical reaction taking place inside the enclosure defined by wall 1. It will be further noted that tungsten is advantageous because of the gaseous state of its compounds with the sulphur hexafluoride decomposition products. This particular characteristic eliminates the need for partial closure of the injection duct 24a.

According to the embodiment illustrated in Figure 1, and the two variants shown in Figures 2 and 3, the downstream end of insert 28 projects from the nozzle body 20 in such a way that the front face 33 (33a and 33b in Figures 2 and 3) of insert 28 are brought into contact with the inner front face 16 of the sleeve 10 over a reduced surface area (referenced 16a and 16b in Figures 2 and 3).

Various embodiments of the downstream end of insert 28 are possible in order to create a reduced-surface contact area. For example, the front face 33a of insert 28 can be incurved or have a slight conicity so as to bear against the inner front face 16 of the sleeve 10 only by the edge 16a of perforation 13 (Figure 2).

The front face 33b of insert 28 can also be flat and parallel to the inner front face 16 of the sleeve 10, but in such a case, contact is advantageously achieved on a flange 1 6b provided around perforation 13 (Figure 3).

When the corrosive product to be injected through duct 24, 24a is SF6, the nozzle body 20 can be produced for example from nickel or stainless steel whereas the insert 28 is produced from tungsten or from a metal having similar properties such as molybden.

Claims

1. Composite injector for introducing a first chemical product, which is corrosive when heated to above a certain temperature, such as sulphur hexafluoride or its decomposition products, into an enclosure containing a second chemical product heated to a high temperature, such as lithium, comprising on the one hand, an outer sleeve which is joined to the walls of the enclosure, and of which the part which is exposed to the second chemical product contained inside the enclosure, is made from a material which is resistant under heat to that second chemical product and to its reaction products with the first chemical product, and on the other hand, inside the sleeve, a nozzle produced in a material which is chemically resistant to the first product and to its decomposition products and which is provided with an injection duct having at least one outlet issuing opposite at least one perforation made in the sleeve, a free space forming a heat barrier over the major part of the outer face of the nozzle situated opposite the sleeve, wherein the outer sleeve is produced in a material which is a poor conductor of heat, has a cylindrical rear part of small thickness, the free end of which is assembled in tight manner on the back of the nozzle by means of a welding bead creating on the nozzle, stresses which tend to apply the downstream part of said nozzle against the inner wall of the outer sleeve, by elastic deformation of the sleeve and the nozzle.

2. Injector as claimed in claim 1, wherein the free space which forms a heat barrier, stretches around the nozzle over the entire area situated opposite the thicker-walled part of the outer sleeve, and said outer sleeve is essentially in contact with the nozzle by its thinner cylindrical rear part.

3. Injector as claimed in claim 1, wherein the nozzle comprises an insert in a refractory material which is also a good conductor of heat, said insert being placed at the downstream end of the nozzle and, in the axis thereof, the downstream end of the injection duct being provided in said insert and said insert defining the outlet, of which the edge bears directly onto the inner front face of the sleeve by a zone of reduced area, around the perforation provided in the outer sleeve.

4. Injector as claimed in claim 3, wherein the insert is produced in tungsten.

5. Injector as claimed in claim 4, wherein the nozzle body is made of a material such as stainless steel or nickel and the insert is preferably assembled by brazing in the nozzle body.

6. Injector as claimed in any one of claims 1 to 5, wherein the nozzle body can be provided on its periphery and inside its downstream part with an annular guiding part in contact pith the inner face of the sleeve over a small surface and defining a first free space between the front face of the nozzle and the inner front face of the sleeve, and a second free space between the peripheral wall of the outer sleeve and the inner face of the thicker peripheral wall of the sleeve.

7. Injector as claimed in any one of claims 3 to 5, wherein the front face of the insert is incurved or slightly conical.

8. Injector as claimed in any one of claims 3 to 5, wherein the front face of the insert is flat.

9. Injector as claimed in claim 8, wherein the flat front face of the insert cooperates with a collar produced around the perforation provided in the inner front face of the outer sleeve.

10. Injector according to claim 1, substantially as described with reference to Figure 1, or Figure 2, or Figure 3 of the acconnpanying drawings.