FR2700583A1 - Method of manufacturing a fluid-cooled wall formed from small assembled tubes. - Google Patents

Abstract

The invention relates to a method for manufacturing a wall cooled by a combustion chamber fluid or the like of a composite type gas turbine, formed from small tubes. The tubes 3 are connected to each other directly and / or indirectly on the face opposite to the hot gases by a coating 5, leaving gaps on the hot gas side 10. The thermal protection layer 8 is applied to the surface of the tubes previously heated and put under duress. On cooling, cracks form which act like expansion joints.

Description

Method of manufacturing a fluid-cooled wall formed of small

assembled tubes

  The invention relates to a method for manufacturing a paper.

  composite type king formed of small assembled tubes that withstands

  cyclic stresses of thermal and mechanical origin is

  laid on one side by hot gases, is cooled by fluid and is

  view of a thermal protection layer on the hot gas side, in particular a method for manufacturing a wall of a combustion chamber or of a nozzle for ejecting gas from a reactor, formed of small tubes of rectangular section, the small tubes being linked directly and / or indirectly between them at the face opposite the hot gases by an additional reinforcing coating and the thermal protection layer forming in operation a flow surface which is

  at least substantially smooth and free from gaps.

  Walls of this type are mainly used in

  combustion chambers and nozzles of rocket boosters work

  operating with liquid propellants By document US-PS 3 190

  , rocket boosters are known in which the walls

  devices, of the composite type, are formed of small tubes and are

  rounds of an outer envelope supporting the mechanical stresses

  which envelope can be produced by projection

  cheerfulness is ensured by the outer casing or by a solder or weld connection, etc. between small tubes, in particular rectangular section. The main advantages of a construction of this type are

  high mechanical strength and rigidity combined with low weight

  due to efficient cooling of the inner wall, hot gas side A certain drawback of this solution is that, during the first start-up, high stresses appear in the parts located on the hot gas side of the walls of the small tubes, which stresses cause permanent deformation The reason for this is the generally insufficient freedom of expansion in the direction

  peripheral, especially when the section of the small tubes is rectan

  gular and that said tubes are already in direct cold contact Under

  the action of thermal stress and pressure of the coolant

  cooling circulating inside the small tubes, the parts of the pa-

  kings located on the hot gas side deform elastically and plastic-

  that is to say permanently towards the middle of the

  propellant During subsequent cooling, for example due to ar-

  stopping operation when the thruster is used improperly

  termittent, it forms as a result of the contraction of the wall parts which have undergone a permanent deformation of the wedge-shaped interstices open between the radial parts of the walls of the small tubes At the time of the possible resumption of operation, the interstices

  close and there is essentially only elastic deformations

  ques with greatly reduced constraints.

  Document DE-AS 21 37 109 discloses a wall structure for rocket combustion chambers which is produced by electroplating and in which rectangular slots open on the hot gas side are fitted at the time of manufacture between the cooling channels in the purpose of allowing almost free thermal deformation in operation For this purpose the galvanizing core is provided with narrow radial projections which are then

  chemically detached from the wall structure This method of manufacture

  particular cation of the walls is long, expensive and poses problems

  my; this is why it has not imposed itself in practice.

  It is also known to reduce the thermal stress on metal walls in contact with hot gases in propellants by using protective ceramic coatings, for example at

  level of the combustion chamber and at the level of the propeller

  gas turbine blowers Generally, these protective coatings are brittle, crack easily under the action of tensile stresses and detach quickly from the metal support in the presence

  internal compression stresses.

  If we apply a thermal protection layer of this type

  eg, a layer of zirconium oxide, on the hot gas side of a new composite type wall formed of small tubes of a

  propellant, there is a high risk that the protective layer is

  damaged from the first operating cycle due to deformation

  The above-mentioned open areas, unprotected from the metal walls of the small tubes, are particularly exposed to deformation and burns, given that the layer of combustion chamber is considered to be

  protective is perfectly active.

  Given the drawbacks of known solutions, the object of the present invention is to indicate a method for the manufacture of a composite type wall formed of small tubes which resists

  thermal and mechanical stresses, is cooled by circu-

  lation of a fluid and is provided with a thermal protection layer which, by largely avoiding the compressive stresses inside the protective layer, guarantees a durable bond and

  reliable between the protective layer and the wall and thus provides

  if a longer service life of the propellant operating in a cyclical manner as well as a better performance of said propellant thanks to

  higher hot gas temperatures.

  The problem is solved according to the invention by the fact A) that the small tubes are connected together so that when cold, that is to say in the unsolicited state on the hot gas side, these be

  applied against each other without play or leave gaps between them

  those whose width is at most equal to the deformation of the small

  tubes provided for in operation, i.e. at their transverse expansion

dirty,

  B) only immediately before application or during application

  tion of the thermal protection layer, the gas side is heated

  assembly of small tubes at operating temperature

  expected in the thermally protected state, so that the in-

  terstices close, after which the protective layer is applied

  thermal protection on a surface which is largely free of intersti-

  ces, C) that as a result of the subsequent cooling, through the interstices which open between the small tubes, there are through cracks, the lar-

  geur corresponds to that of the interstices below.

  Note with regard to point A that we can act very effectively on the dimension cold and in new condition (from "zero" to the maximum) of the gap between the small tubes through the shape

  in section of said small tubes, rectangular and trapezoidal shapes

  dales being particularly advantageous.

  Please note with regard to point B that when applying

  tion of the thermal protection layer, the hot gas side of the as-

  the appearance of small tubes is appreciably at the temperature expected

  due in operation, with plastic / elastic deformations in

  consequence and closed interstices.

  In accordance with point C, during the subsequent cooling of the assembly coated with the protective layer, there are formed in the protective layer, through cracks at the level of the interstices

  the width of which increases During subsequent operating cycles

  laughing, these cracks close so that the protective function of

  the layer is not altered Furthermore, the cracks which act at the

  expansion joints prevent the appearance of compression stresses inside the protective layer and thus avoid

  sure that it comes off the wall of the small tubes.

  In accordance with a characteristic of the invention, when

  that after bonding, the small tubes are applied without play against each other or when there are gaps between them whose width is substantially smaller than the deformation of the tubes expected in operation, the assembly is subjected to small single cycle tubes

  thermal / mechanical which corresponds at least to the operating conditions

  predictable operation before applying the coat

  thermal protection The small tubes then undergo a deformation

  plastic such that after cooling and disappearance of the stresses

  between them, on the hot gas side, defined gaps

  whose width corresponds to the foreseeable deformation in operation-

  is lying. According to another characteristic of the invention, the stresses for the thermal / mechanical cycle, at least one in number, are greater than those which appear in operation. These are chosen so that the plastic deformations thus produced from the small tubes correspond to the sum of the deformations

  elastic and plastic expected in operation.

  Preferably, small walls are used to make the wall.

  bes of rectangular, square or trapezoidal cross section The pro-

  thermal protection is applied by hot spraying, for example

  by vacuum or low pressure plasma spraying.

  When the small tubes are connected together in a di-

  the connection between the small tubes can be made by welding

  and / or by soldering When the small tubes are connected together

  indirectly by a reinforcing layer, the reinforcing layer is ap-

  plicated by plasma spraying and / or by galvanization and / or by a pro-

  ceded with fiber-reinforced composite material.

  In accordance with a characteristic of the invention, the layer

  thermal protection is made of zirconium oxide.

  The invention is described below in detail in detail.

  sant reference to the drawings These represent in a simplified manner, without respecting the dimensions: FIG. 1, a partial section of a wall in new condition, when cold,

  without protective layer, version with external reinforcement layer

  being represented to the left of the median axis and an execution without

  reinforcement layer with direct assembly of the small tubes being represented

felt right,

  Figure 2, a partial section of a wall with reinforcing layer

  strong outside, in the warm state before (left half) and after (right half) application of the protective layer, Figure 3, a partial section corresponding to the right half

  of Figure 2, in the cooled state.

  For a better understanding, the interstices, the distortions

  walls and the curvature of the wall are strongly exaggerated compared to reality Similarly the ratios of wall thicknesses,

  layer thicknesses, weld seam dimensions, etc. do not

  There are no conclusions as to the actual reports.

  The left part of FIG. 1 represents a wall 1 in which the small tubes 3 are linked indirectly by the intermediary

  diary of an outer reinforcing layer 5.

  The right part of the figure represents a wall 2 in the-

  which small tubes 4 are assembled directly by cor-

  weld donations 6 The two walls 1, 2 are in new condition, cold, this

  which means that the small tubes have not yet been subjected to sol-

  thermal and mechanical licenses.

  The small tubes 3 have a trapezoid-shaped section and are

  applied directly against each other at the level of their

  face with the reinforcing layer 5 The wall parts 7 gas side

  hot spaces leave free gaps 9 whose dimension is at most

  mum equal to the deformation in operation We can act ma-

  niere targeted on the dimension of the interstices 9 through the shape

  in section of the small tubes 3 The reinforcing layer 5 which is formed

  mé of a metallic material or not having a mechanical resistance

  that and sufficient temperature resistance fulfills the functions of

  connection, reinforcement and sealing of small tubes.

  For wall 2, small more ordinary tubes 4 with rectangular or square section are used which are applied against each other substantially without gap on the hot gas side The gaps due to the shape on the "cold" outside side are particularly well suited for a connection by welding between the small tubes 4, see cord

solder 6 shown.

  Figure 2 shows the construction of the wall with reinforcement layer The part of the figure to the left of the median axis represents

  the state just before application of the thermal protection layer 8.

  The small tubes are brought to the hot gas side at a temperature which

  responds substantially to the expected operating temperature

  with thermal protection Due to thermal expansion, the pe-

  tits tubes 3 are applied without gaps against each other La

  coolant pressure in operation being higher than

  higher than the pressure of the hot gases (pressure of the combustion chamber

  bustion, nozzle pressure) it makes sense for an opti-

  male operating conditions at the time of application of

  the protective layer to apply a pressure corresponding to the interior

  laughing small tubes 3 The wall parts 7 then undergo a defined deformation towards the hot gas side, as shown in Figure 2 The deformation can also be caused by the fact that the thermal expansion of the wall parts 7 is greater at the gap

9 existing cold.

  The right part of FIG. 2 shows the thermal protection layer 8 which is applied by hot spraying, is preferably formed from zirconium oxide and which, immediately after application, is

  substantially smooth and free from cracks.

  When heating (preheating) the wall 1 just before

  the application of the thermal protection layer 8, it is advisable to

  Take into account that there is a significant additional rise.

  aunt of the temperature due to the projection.

  FIG. 3 corresponds to the rest of the process applied on the right-hand side of FIG. 2 and shows the cold state, without stress,

  of the wall 1 provided with a protective layer 8 Between the small tu-

  bes 3 cooled which underwent permanent deformation are found

  defined interstices 10 which act like dilatation joints

  tion and extend into the protective layer 8 in the form of a fissure

  defined through res The cracks 11 are formed in a "self-

  matic "during cooling" since the protective layer

  this relatively brittle ceramic oxide-based 8 cracks easily -

  in the presence of tensile stresses Grip on surfaces

  these metal wall parts 7 prevents cracking of the

  protective layer 8 in these areas.

  During each subsequent operating cycle, the cracks

  res it closes so that there is a protective flow contour

  ge and smooth The protective layer remains substantially free of

  compression stresses and does not tend to come off.

  In practice, it is often difficult to achieve in the

  cold wall of the interstices which have a width of

  finished (see figure 1 left part) The large number of tubes to assemble

  bler (up to several hundred) and the deviations of their shape lead to new and cold interstices which can vary locally in significant proportions To avoid the presence locally of residual interstices in operation we adopt as an average dimension of gap in new condition and when cold, a value which is significantly lower than the value of the expected thermal expansion and the necessary thermal expansion joints are made at the time

  of the application of the protective layer by application of the stress

thermal / mechanical.

  In the case in particular of walls with cold and in new condition very small mean gaps, for example in the case of the wall

  2 of figure 1, right part of the figure, we must expect

  important formations during the first heating simulating the conditions

  In this case, it is recommended not to use

  plique the fragile protective layer from the first heating process but at best during the second heating process after an intermediate cooling Thanks to this thermal or thermal / mechanical cycle, at least one of conditioning without protective layer, the wall "works "much less during the application of the protective layer thus giving a secure adhesion

of said protective layer.

  An optimal protective layer is obtained which is free from compression stresses and is "closed" in operation by applying, before or during the production of the protective layer, thermal stresses or thermal / mechanical stresses slightly greater than those encountered in operation, the stresses to be such as the plastic deformations which

  result are equal to the sum of elastic deformations and plas-

ticks in operation.

Claims (8)

  1 Method for manufacturing a composite type wall   formed of small tubes which withstands original cyclic stresses   thermal and mechanical, is swept on one side by hot gases, is cooled by fluid and is provided on the hot gas side with a thermal protection layer, in particular for the manufacture of a wall   of small rectangular section tubes for a control chamber   bustion or reactor gas ejection nozzle, the small tubes   being linked together directly and / or indirectly on the oppo-   seized with hot gases by an additional reinforcing coating and the thermal protection layer forming in operation a surface   flow which is at least substantially smooth and free of interstitial   these, characterized by the following stages: A) the small tubes (3, 4) are linked together in such a way   only when cold, in the unsolicited state on the hot gases, these are applied   ques against each other without play or leave between them gaps (9) whose width is at most equal to the deformation of the tubes provided in operation, that is to say their transverse expansion, B) immediately before application or during application of the thermal protection layer (8), the hot gas side of the assembly of small tubes is heated to the temperature expected in the state with thermal protection so that the interstices (9)   close, after which the thermal protection layer is applied   that (8) on a surface which is largely free of gaps, C) following the subsequent cooling, it forms in the thermal protection layer (8), in line with the gaps (10) which open between the small tubes (3), through cracks (11) including   the width corresponds to that of the interstices (10) located below.   2 Method according to claim 1 for a wall whose small tubes, after bonding, are applied one against the other or leave between them interstices whose width is significantly smaller than the deformation of the tubes foreseeable in operation, characterized by the fact that before application of the thermal protection layer, the assembly of small tubes is subjected to a thermal / mechanical cycle which corresponds at least to the foreseeable operating conditions, the small tubes being plastically deformed so that after cooling and disappearance of the stresses there remains between them hot gas side of the defined interstices whose width corresponds to the deformation of the small tubes expected in operation.  3 Method according to claim 2, characterized in that, during the thermal / mechanical cycle at least one in number, the stresses chosen are greater than those which appear subsequently in operation, namely so that the deformations plastics thus produced small tubes correspond to the sum   elastic and plastic deformations expected during operation.   4 Method according to any one of claims 1 to 3,   characterized by the fact that small tubes (3, 4) of section are used   rectangular, square or trapezoidal to make the wall (1, 2).   5 Method according to any one of claims 1 to 4,   characterized in that the thermal protection layer (8) is app-   plication by hot spraying, for example by plasma spraying vacuum or low pressure.   6 Method according to any one of claims 1 to 5   in which the small tubes are directly linked together, ie   characterized by the fact that the connection between the small tubes (4) is made   by welding (weld bead 6) and / or by brazing.   7 Method according to any one of claims 1 to 5   in which the small tubes are indirectly linked together by a reinforcing layer, characterized in that the reinforcing layer (5) is applied by plasma spraying and / or by galvanization and / or   by a fiber reinforced composite coating process.   8 Method according to any one of claims 1 to 7,   characterized in that the thermal protection layer (8) is in zirconium oxide.