DE2418840A1 - HEAT EXCHANGERS, IN PARTICULAR REGENERATIVELY COOLED COMBUSTION CHAMBERS FOR LIQUID ROCKET ENGINES AND THE PROCESS FOR THEIR PRODUCTION - Google Patents

Description

Heat exchangers, in particular regeneratively cooled combustion chambers for liquid rocket engines and processes for their manufacture

The invention relates to heat exchangers, in particular regeneratively cooled combustion chambers for liquid rocket engines, consisting of a one-piece base body a highly thermally conductive metallic material, in particular oxygen-free copper, with running through, of at least one cooling liquid, in particular at least cooling channels through which a fuel component can flow,

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which are galvanized onto the base body through an outer wall, relatively thin-walled intermediate layer and a relatively thick-walled one on the intermediate layer galvanized pressure jacket made of a metallic material of high strength are covered, as well as a method for the production of such heat exchangers

In the case of liquid rocket engines, it is customary to use at least one of the am Fuel components involved in the combustion process at the rear end of the exhaust nozzle via an inlet ring in within the Introduce thrust nozzle and combustion chamber wall longitudinal cooling channels and lead through them to the front, where the Fuel component is collected in a ring and fed to the injection head of the combustion chamber · A rocket engine represents in terms of combustion technology and in In terms of its construction, it is a complex machine with numerous, often contradicting requirements must be sufficient, which must be coordinated in the design and construction of the engine to an optimal whole. The rocket burning process, which takes place at extreme temperatures, is required to achieve a high degree of efficiency a great pressure ratio. Since until today there is no material or no suitable metal that is extremely unprotected could withstand high furnace temperatures, must for this. Care must be taken that the amount of heat generated is dissipated very quickly. This task is taken over by the flowing through Coolant, which has to keep the mean wall temperature of the combustion chamber and exhaust nozzle in one area, in which sufficient wall strength is still guaranteed. In the previously known constructions, however, for technological and constructional reasons, the upper strength limit in relation to temperature usually very soon and pressure achieved

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Combustion chambers made in one piece from steel have cast-in or otherwise incorporated cooling channels and a welded-on steel outer jacket covering this (US Pat. No. 3,154,914) which increases the efficiency of the Firing process increasing temperature increase therefore set relatively narrow limits because of the occurring Heat build-up an overheating of this material occurs, the heat resistance of which decreases rapidly with increasing temperatures.

To control the very high combustion chamber temperatures is It is also already known to produce the combustion chamber with a thrust nozzle from a coil of copper tubing lying one turn on one turn and the individual turns lying against one another firmly together by copper welding or bronze soldering connect to. However, there is a considerable risk that during the operation of the combustion chamber the numerous, directly Joints exposed to fire between the individual pipe windings are thermally overstressed.

Furthermore, a structure of the Brennkaramerwand is known the individual elements assembled to form a "raw" wall mechanically strong and mechanically strong by means of a relatively thick-walled layer which is electroformed on one or both sides are connected pressure-tight. It can be used to absorb large mechanical loads, as is the case with high-performance combustion cameras occur, reinforcement in the form of a rolled steel band must also be provided (German Auslegeschrift 1 264 160).

Finally, heat exchangers or combustion chambers are also the initially referred to known, in which the base body and the intermediate layer made of oxygen-free copper or equivalent material such as silver or molybdenum exist (German patent specification 1 751 691). These known combustion chambers versus the others discussed above

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Combustion chambers according to the state of the art represent a considerable advance, even an almost ideal solution. In these, in contrast to other known combustion chambers, especially when the intermediate layer is made of the same material as the base body, there is radial everywhere between the combustion chambers Outward-facing surfaces of the individual webs and the inside of the intermediate layer ensures a secure connection. In addition, this measure results in an intensive heat transfer to the coolant flowing through the material and over the entire cross-section of the cooling duct. Furthermore, the pressure jacket, which envelops the intermediate layer in an absolutely form-fitting manner and is firmly bonded to it at all points, which should be made of nickel or a similar material with high strength, guarantees a solid support of this intermediate layer and thus its tear-proof connection with the webs of the base body.

Furthermore, the galvanic production of the printing man- a precise variation of the layer thickness in a simple manner Considered over the length of the structural unit, so that the Strength of the same can be optimized and the structural weight can be reduced to a minimum. Furthermore, this enables Electroplating the pressure jacket a favorable structural inclusion of connectors for fuel lines and fittings

Due to the poor thermal conductivity of the pressure frame, which is usually made of nickel, it has a relatively low outside temperature, which has a beneficial effect on the airframe of an aircraft or spacecraft. Finally, as a result of the smaller expansion coefficient of the outer jacket or the pressure jacket, if this is made of nickel, the composite construction in question brings about a reduction in the stresses under space conditions compared to a structural unit made entirely of copper

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with itself, namely because the expansion of the base body, which consists of copper, together with the intermediate layer due to the heat load from within and the contraction of the nickel or equivalent material produced outer jacket due to the low ambient temperatures add up against each other.

In addition to advantages, these known combustion chambers also have a disadvantageous property, namely the relatively low corrosion resistance of the materials that can be used for the base body and the intermediate layer, which does not affect their usability in liquid rocket engines operated with cryogenic fuels in the slightest, their use in so-called storable liquids Fuel-powered rocket engines because of the strong corrosiveness of the oxidizers used, such as red fuming nitric acid and ^N 2 ° 4 * ^but becomes impossible

Since rockets operated with storage-stable liquid fuels are fundamentally superior to liquid rockets operated with cryogenic fuels due to their rapid readiness for use in all areas of application in which the start time cannot usually be determined in advance, the invention is based on the object of providing heat exchangers to those mentioned at the beginning Kind to provide that not only have the advantageous properties of combustion chambers of this type compared to other combustion chambers, but also have cooling channels that are corrosion-resistant _{to all known oxidizers of liquid rocket fuel systems that can be stored, in particular to NpO 4} ^{un <* fuming nitric acid (} the term "corrosion-resistant" is always used in the sense defined above) and can therefore also be used in liquid rocket engines for storage-resistant fuels *

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This object is achieved according to the invention by heat exchangers of the type mentioned at the outset, which are characterized in that the walls of the cooling channels located in the base body are coated with galvanically deposited, at least about 4 μm thick corrosion protection layers made of aluminum or are made of a corrosion-resistant material, in particular corrosion-resistant steel and the intermediate layer consists of optionally cold-deformed and / or dispersion-hardened aluminum and is at least about 8 years thick.

This solution to the problem underlying the invention, the on the undeniably obvious, but only seemingly easy to put into practice idea is based on modifying heat exchangers of the type described at the outset in such a way that any oxidizers through the cooling channels known, liquid, storage-stable fuel systems can be passed that you have the cooling channel walls on all sides covered with a thin anti-corrosion layer made of a highly thermally conductive, corrosion-resistant material, could only be put into practice with considerable difficulty and due to the following surprising findings will:

1) Aluminum, which is made up of aprotic, water- and oxygen-free, in particular those containing alurainium organyls Can be electrodeposited baths, forms layers that are not only firmly adhering, but also with the Heat exchangers of the invention grown thermal and mechanical loads and also already at a relatively low strength of about 4 pn so Are corrosion resistant that they provide adequate protection against the attack of oxidizers of all the common ones provide storage-stable liquid rocket propellant systems.

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2) If you use a filling compound for filling, the cooling channels If low-melting metal alloys are used, the outer wall-side surface of the prefabricated Base body with galvanically aluminized cooling channels then filled with filler material, ζ · Β · from "Material Technology" 1972, Issues 9 and 10 known Pretreat methods and then galvanically aluminize them in such a way that they are firmly adhering, closed and corrosion-resistant Interlayers are given, which usually also have sufficient strength to a Sufficient tear or break resistance of the heat exchanger at the connection points between the outer wall and the To ensure webs of the base body

A preferred embodiment of the invention with particularly high mechanical strength are provided by heat exchangers with intermediate layers of electrodeposited dispersion- and / or cold deformation hardened aluminum

The cold deformation hardening of the intermediate layers can be carried out by Shot peening can be effected after or during the electrodeposition.

By using appropriate dispersoids, intermediate layers can also be made of a dispersion-hardened one Manufacture aluminum, which by a suitable heat treatment in an aluminum alloy with better mechanical Quality values and especially higher heat resistance than pure aluminum is converted · As a dispersoid are suitable for this embodiment of the invention in particular copper, nickel and silicon.

Compared to intermediate layers and, if necessary, anti-corrosion layers made of gold or other corrosion-resistant Precious metals, which are the subject of two patent applications filed at the same time, offer the invention

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Intermediate and anti-corrosion layers with equally satisfactory corrosion resistance have the advantage of not only being made of a cheaper material, but also that flawless, well-adhering intermediate layers can easily be deposited on base bodies with anti-corrosion layers even if the webs are not etched back at least 5 μια deep are·

Particularly preferred are heat exchangers according to the invention with multilayer intermediate layers, the base body side of which is first Layer consists of aluminum, the subsequent second layer preferably made of zinc or copper or gold and the the next layer is made of aluminum, etc.

To activate aluminum surfaces, invention according to zincate pickles known per se preferably used for this purpose ·

The intermediate layers of the heat exchangers of the invention are preferably about 12 to 240 μm thick.

In the case of heat exchangers according to the invention, the pressure jacket preferably consists of copper, nickel, a nickel-cobalt alloy. tion or an equivalent, electrodepositable material · In addition to its excellent properties, copper offers Thermal conductivity in particular has the advantage that it easily and well adheres easily in thick layers can be deposited on the intermediate layers. Nickel and nickel-cobalt alloys are used as the pressure jacket material in particular because of the fact that pressure jackets made of these materials have a certain heat shield effect on the one hand, which is particularly important during use the heat exchanger according to the invention in rocket engines is advantageous, and on the other hand not just a relatively high strength, but also a lower heat.

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have expansion coefficients than the material of the base body, e.g. copper, so that when the heat exchanger heated during use and the base body expands more than the pressure jacket, which is a particularly full one and firm support of the base body against the Druckraantel is achieved, whereby the high pressure difference between relative to the fuel components flowing through the cooling channels and in particular in the rear part low pressure inside the rocket combustion chamber resulting tensile stress on the intermediate layer in the area between the webs and the pressure jacket is significantly reduced and usually even far overcompensated · A Another advantage that is achieved by pressure jackets whose thermal expansion coefficient is less than that of the basic body is, can be seen in the fact that when the heat exchanger is heated between the Druckraantel and the tops the parts of the intermediate layer lying on the webs of the base body are exposed to high compressive stress as a result of any existing defects or pores at the seams between the corrosion protection layers and squeezed into the intermediate layer

They are particularly useful - because of their low weight Pressure jackets made of optionally dispersion and / or cold deformation hardened, electrodeposited Aluminum or, as explained above, aluminum alloys

According to a further preferred embodiment, heat exchangers according to the invention have cooling channels with rounded ones or chamfered edges or transitions between the floor and the side walls, since they are designed in this way The difference between the thickness of the galvanically deposited corrosion protection layers in the cooling channels upper part of the cooling channel side wall and the bottom of the cooling channel considerably less than in the case of rectangular ones Cooling channels is.

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Exemplary embodiments of the invention are shown in the drawing.

Figure 1 shows a heat exchanger according to the invention (combustion chamber with exhaust nozzle) in longitudinal section,

FIG. 2 shows a section along the line II / II in FIG. 1 and

FIG. 3 shows an enlarged detail of the sectional view according to FIG. 2.

The unit combustion chamber with thrust nozzle consists essentially of a highly thermally conductive metal, e.g. oxygen-free copper, manufactured base body 1. This can be made from a copper block in a conventional manner, e.g. by forging, prefabricated (solidified in structure) and finished by machining or in the German Patent 2,015,024 known manner be made by electroforming ·

Cooling channels 2 running in the longitudinal direction are carved out of the base body 1 and are separated from one another by webs 3. The wall surfaces of the cooling channels 2 lying in the base body 1 are coated with corrosion protection layers 6 made of aluminum, which are galvanically deposited thereon, and which cannot be seen in FIGS. 1 and 2. The cooling channels 2 and the tops of the webs 3 are covered with a practically completely closed intermediate layer 4 made of aluminum, which is covered by a relatively thick-walled pressure jacket 5 made of copper, nickel, a nickel-cobalt alloy or an equivalent material, which is electrodeposited thereon.

From the shown in Figure 3, enlarged view of a section through a detail of an invention

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according to the heat exchanger, transversely to the cooling channels 2, it can be seen that the thickness of the anti-corrosion layers 6 along the wall of the webs 3 decreases from top to bottom and in the area of the edge between the side walls and the Bottoms of the cooling channels 2, which in the embodiment shown abut almost at right angles, are extraordinary is thin · The intermediate layer 4 consists of three layers

4a, 4b, 4a ¹ !, where the first layer 4a on the base body is made of aluminum, the following second layer 4b is made of zinc and the third layer 4a 'is made of aluminum.

Patent claims:

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Claims (7)

Claims Heat exchangers, in particular regeneratively cooled combustion chambers for liquid rocket engines, consisting of a one-piece base body made of a gwt thermally conductive metallic material, especially oxygen-free copper, with continuous, of at least one cooling liquid, in particular at least one fuel component through-flow cooling channels, which through an outer wall made of a galvanized onto the base body, relatively thin-walled intermediate layer and a relatively thick-walled one on the intermediate layer galvanized pressure jacket made of a metallic material of high strength are covered, thereby characterized in that the walls of the cooling channels (2) lying in the base body (1) are also galvanically deposited at least 4 iim thick anti-corrosion layers (6) made of aluminum are bare consist of a corrosion-resistant material, in particular corrosion-resistant steel, and the intermediate layer (4) at least on the cooling edge side in a thickness of at least about 8 .mu.m from optionally cold-treated formed and / or dispersion-hardened aluminum -13- 509844/0576 2. Heat exchanger according to claim 1, marked by multilayer, preferably three-layer intermediate layers (4), whose on the cooling channel side first layer (4a) consisting of preferably cold-deformed and / or dispersion-hardened aluminum following layer (4b) made of another, preferably also cold-deformed and / or dispersion-hardened, galvanically deposited metal, in particular zinc, copper or gold, consists 3 · Heat exchanger according to claim 1 or 2, characterized in that the base body (1) made of a non-corrosion-resistant material, in particular copper, and the base body (1) lying walls of the cooling channels (2) with at least about 12 pn thick corrosion protection layers (6) galvanically deposited aluminum 4 · Heat exchanger according to claim 3, characterized through cooling channels with rounded or chamfered transitions between side walls and floor. 5. Heat exchanger according to one of claims 1 to 4, characterized by a pressure jacket (5) made of copper, nickel or a nickel-cobalt alloy 6 heat exchanger according to one of claims 1 to 5, characterized by a pressure jacket made of a material whose coefficient of thermal expansion is smaller than that of the base body material. 7. A method for producing heat exchangers according to any one of claims 1 to 6, by prefabricating one one-piece base body with cooling channels from one 509844/0576 highly thermally conductive metallic material, in particular Copper, filling the cooling channels with an electrically conductive, easily meltable filling compound, Electroplating a thin intermediate layer on the Base body and a relatively thick-walled pressure jacket on the intermediate layer and melted out the filling compound from the cooling channels, characterized in that one on the walls of the cooling channels (2) in the base body (1), if they are not made of a corrosion-resistant material, galvanically closed, approximately 4 to 100 μm A strong anti-corrosion layer of aluminum is deposited, along with the - optionally aluminized - cooling channels a filler made of a low-melting alloy known per se for this purpose and from an aprotic bath an at least about 8 µm thick intermediate layer of aluminum is electroplated deposited on the base body 5098 A A / 0576