Nozzle For Rocket Engine

Abstract

An improved structure and method of making are provided for cooling the conical nozzle of a rocket engine. The nozzle is constituted of a number of curved segments welded together along their side edges to form the cone member. In order to provide for cooling the metal of each segment, the latter is laid as a flat plate on the bed of a planing machine and by means of a gang-cutting tool, grooves are cut in the plate across its entire width. Thereafter a flat-facing sheet of metal is diffusion bonded to the grooved plate to leave closed channels across the plate composite. The plate is then curved to proper shape and the abutting edges are welded together so as to leave channels extending lengthwise of the member. These channels are made to coincide with similar channels formed along the combustion chamber. In the event of a jet engine powered by a mixture of gases, an auxiliary conduit is taken from one of the gas supply lines and forced through the channels for cooling purposes and finally returned to the source of the gas.

Description

BACKGROUND OF THE INVENTION

It is necessary in a rocket engine to provide some form of cooling means for the thrust chamber assembly. The cooling fluid which is usually contained in a built-in jacket or a cooling coil surrounding the wall of the combustion chamber and nozzle, usually constitutes either the oxidizer or the fuel. The coolant is returned to its original source so that the heat absorbed by the coolant is not wasted but augments the initial energy content of the propellant prior to injection.

Various structures have been proposed to provide the jacket or the cooling coil. But, such structures are complicated, not only from the manufacturing standpoint but also in the assembly of the various parts. Moreover, the cooling means are not altogether reliable in operation. Rocket engines run for short periods of time and must develop their full power almost instantaneously so that any malfunction of the cooling system which must also respond immediately can be most detrimental, even causing the engine to destroy itself by the tremendous heat developed within the combustion chamber. The most vulnerable portion of the engine, from the cooling standpoint, is the throat section of the nozzle which is located at the place of the highest heat-transfer energy intensity and is therefore the most difficult to cool. It is therefore important that the coolant be given unrestricted access to the nozzle and particularly to the throat section which immediately precedes the nozzle.

SUMMARY OF THE INVENTION

An object of the invention is to provide an improved cooling system for a rocket engine and, in particular, provide an improved nozzle and its throat section.

Another object is to provide an improved nozzle for an aerospike engine and in which its construction is such as to facilitate its integration with the combustion chamber.

Another object is to improve the accessibility of all parts of the engine, especially the nozzle and throat portions to the coolant.

Another object is to provide an improved method of fabrication of the cooling system including the nozzle and throat section of a rocket engine. These objects are attained in brief, by employing a cylindrical combustion chamber having channels which extend longitudinally of the chamber and in employing complementary segments of a nozzle with integral channels, the latter serving as extensions of matching channels in the chamber. The channels in the nozzle segments are obtained by milling out parallel grooves in a flat sheet of metal and overlying the grooves with a separate metal sheet. Thereafter, the two sheets of metal are joined by a diffusion bond and after trimming and bending the metal composite to shape, welding the edges of a number of the segments together to form a nozzle in which the longitudinal channels conform precisely to the longitudinal channels of the combustion chamber.

Other objects and features will be apparent as the specification is perused in connection with the accompanying drawings, in which:

FIG. 1 represents a vertical section of an "aerospike" jet engine provided with the improved nozzle but showing the parts of the fuel supply and the cooling system in schematic form.

FIGS. 2, 3, and 4 are cross-sectional views taken through the nozzle at the positions marked by section lines 2, 3, and 4 respectively in FIG. 1.

FIG. 5 represents a perspective view of the improved nozzle attached at one end to a typical combustion chamber.

FIG. 6 shows the use of a gang-cutter milling machine for cutting the initial grooves in the metal plate, which, when formed, become a nozzle segment.

FIGS. 7, 8, 9 and 10 are views in perspective of the additional operations performed to obtain the improved nozzle and parts thereof.

FIG. 1 represents a longitudinal section but partly schematic of a rocket engine, and in which the combustion chamber is designated generally by the reference character "1." The nozzle is designated by the general reference character "2." The chamber and nozzle are joined by the inwardly curved throat section 3. The chamber constitutes the combustion portion of the engine and is fed by the combination of an oxidant e.g. liquid oxygen) and a fuel e.g. hydrogen) in proper proportion, fed through the conduits 4, 5, respectively. As seen in FIG. 5, the chamber is preferably constructed of a number of elongated rectangularly shaped conduits or hollow rods 6 (FIG. 2) made of relatively thin metal, the conduits being pressed inwardly to a curvilinear "S" shape as indicated at 3 to form a throat section. The conduits are preferably formed by extrusion having a square configuration so as to provide complete peripheral continuity, and can be bent to the proper curvature in a forming machine without severe deformation of the opening in each conduit. However, the latter could also be made of a standard round-tubing e.g. of stainless steel formed to a square shape. The upper ends of the conduits 6 are held in place by a relatively thick end plate 7 and communicate with an enclosed compartment 8 which extends around the plate. The pipes 4, 5 extend through the plate 7 and, at one end, communicate with the interior of the combustion chamber and, at the other end, make connection respectively to a liquid oxidant and a source of fuel under pressure. There is also a pipe or conduit 9 which is connected to the pipe 5 at one end and at the other end communicates with the annular compartment 8. The purpose of this conduit and the compartment 8 will be explained hereinafter. The lower ends of the parallel-arranged conduits 6, as indicated at 10, are held in position by being received by certain matching channels formed within the nozzle section 3.

CONSTRUCTION OF THE NOZZLE

The present invention pertains more especially to the construction and method of making the improved nozzle with adequate provision for cooling that particular structure. As shown in FIGS. 1 and 5, the nozzle takes the form of a frustrum of a cone diverging outwardly from the throat section 3 and terminating at the lower end in a hollow circular enclosure 11. The complete structure is made up of a plurality of segments as illustrated in FIG. 10 and secured together at their edges. The nozzle is provided with a series of equidistantly spaced channels extending lengthwise of the segments for receiving the coolant. It will be noted that the outward taper of the cone is straight throughout its length (except for the presence of the circular enclosure 11) and such construction lends itself to procuring passageways 12 within straight paths over the entire length of the cone. These passageways or channels are formed in the manner described presently.

Referring to FIG. 6, the material of each segment 13 in flat form is secured to the reciprocatory bed of a mill, generally indicated at 14. A gang tool 15 with cutting edges set apart the distance between the passageways is employed. The gang tool is carried by a head 16 supported on the crossbeam 17 and can be moved across the material by the handle 18. An electrical motor and the necessary gearing and levers all of which are well known and not shown, are contained in the base 19 to drive the bed 20 of the mill along its roller bearing 21 in the cutting and return directions as indicated by the double-headed arrow 22. The grooves 23, which eventually constitute the channels or passageways 12, extend the full length of the metal plate 13, which becomes a segment of the nozzle as pointed out hereinafter. The latter is made of heavy machinable metal such as stainless steel, capable of withstanding extremely high temperature. The next step is to lay over the grooved surface of the material 13 a flat metal plate 24, and then to secure the facing plate to the grooved member by a well-known operation termed "diffusion bond." Thus, the facing plate causes the grooves to be closed along their length and the latter then becomes passageways or channels for receiving a coolant, as will be described hereinafter. The next step in the process of making the nozzle is to trim the edges 25 of the composite member to conform to a template by a suitable and well-known cutting machine. The plate is then given the requisite curvilinear shape to constitute a nozzle segment by being placed in a forming machine (not shown) of any suitable and well-known type. Six, or any other desired number, of these segments are fitted together at their longitudinal edges and the abutting elements are welded to complete the nozzle. Thereafter, the circular enclosure 11 is attached to the lower or wide open end of the nozzle. The smaller diameter end of the nozzle is then provided by machine with a large and fairly deep annular recess 26 for receiving the integrated lower ends 10 of the combustion chamber elements 6. The joint is suitably brazed as indicated at 27. It is apparent that the spacing of the grooves (FIG 6) which eventually form the coolant channel 12, must be accurately determined so that, when the combustion chamber and nozzle elements are fitted together at the recess 26, continuous passageways are provided along the entire length of the chamber and nozzle. A well-known split-filler block 28 is secured to the outside surface of the throat region of the structure in order to provide extra material at this position to dissipate the excess heat. In addition, a number of metal-bracing bands indicated at 29 can also be employed to ensure that the multipart chamber and nozzle elements are held rigidly in the circular direction. In order to return the coolant from the circular enclosure 11 back to its source of supply, an escape pipe 30 extends from said enclosure to the pipe 5. The pipe 30 may be secured in any suitable manner to several of the bracing rings 29 to thus add rigidity to the structure as a whole. The escape pipe contains a one-way check valve 31 of well-known type, which allows fluid to pass only in the direction of the arrow.

OPERATION OF THE COOLING SYSTEM

When the oxidant and fuel are introduced into the combustion chamber 1 through the pipes 4, 5 part of the fuel supply is diverted and flows through the conduit 9 into the annular chamber 8. The latter connects with the upper ends of the chamber 1 and the fuel is caused to flow through the passageways or channels 12 which extend along the chamber, the throat and nozzle sections into the circular compartment 11. The gas is then caused to flow through the return conduit 30, past the check valve 31 into the pipe 5 where it joins the mainstream of the fuel being ejected into the combustion chamber. None of the fuel is lost through the circulatory system and yet the passing gas serves to cool all the parts of the engine including the throat and nozzle portions.

From the foregoing, it is evident that I have disclosed not only an improved nozzle which effectively receives a coolant but also is adapted to serve as accessory for a combustion chamber which is cooled by the use of the fuel or the oxidant. In addition to the improved nozzle as a structure, there is disclosed an effective method of making the nozzle, assuring that the channels 12 are equidistantly spaced from one another and the machine work for producing the channels is kept at a minimum.

Claims

What is claimed is:

1. An article of manufacture comprising a nozzle adapted to be secured to the combustion chamber of a thrust propulsion engine with the combustion chamber having coolant passageways therethrough; said nozzle constituting a hollow circular member of large diameter tapering down to a smaller diameter, said nozzle being constituted of curved segments joined together at their edges to form a peripherally complete conically shaped wall, said segment consisting of two plates of metal bonded together along their faces by diffused heat, with plates forming the outer surface of the combustion chamber and having grooves extending through the wall from the large diameter end to the small diameter end of the nozzle and the other plate serving to form the inner surface of the combustion chamber and to close the open side of the grooves to complete the peripheries thereof to form passageways through the nozzle, said passageways being of a size and are spaced apart to match the coolant passageways of the combustion chamber at the position where the nozzle and combustion chamber are secured together.