Blind cutting process with high-pressure jet for an engine block

Description

Technical Field

[0001] The invention relates to the thrusters of an aerospace transport vehicle, and more particularly to a method of cutting a thruster body by high-pressure jet, the cutting being carried out in a non-through manner. Prior art

[0002] As illustrated in the Figure 1 which presents a schematic sectional view of a body 1 of a known propellant, the body has the general shape of a cylinder closed at each axial end by a domed cover 2. Each cover 2 comprises a plug 3. The plug is inserted into an orifice provided in the cover and delimited by a shoulder 4 over its entire circumference, the shoulder extending in axial projection towards the interior of the body of the propellant.

[0003] Thus, the geometry of the propellant bodies used as illustrated in the Figure 1is not suitable for the draining method used. In fact, the presence of the retracting bottoms formed by the annular shoulder 4 can, on the one hand, generate a puddle of water which will alter the quality of the draining, and on the other hand, hinder the evacuation of the propellant residues resulting from the draining.

[0004] These two problems require either vertical emptying, which can be very complex for large loads, or emptying large loads by rotating on a steeply inclined plane using a residue suction device. Both of these solutions are very complex to implement.

[0005] To overcome these two problems, it is possible to consider removing the rear bottom of the loads before emptying in order to eliminate the retracting bottoms. Emptying these loads will thus be simplified thanks to the absence of rotation of the loads, and the presence of a slight inclination (around 20°) of the load during emptying.

[0006] The rear bottom can be opened using a high-pressure water jet. However, the cutting must not damage the propellant contained in the thruster.

[0007] While abrasive water jet cutting is widespread throughout the world, non-through machining or non-through cutting is very little developed scientifically and almost non-existent industrially.

[0008] Single or multi-pass non-through cutting processes are known which attempt to reduce the depth variability of the non-through cutting by multiplying these passes.

[0009] However, known processes deal with continuous cutting and not transition zones. Indeed, to make a complete cut, the jet must pass back over the area it has already passed to close the cut. By passing over an existing cut line, the depth obtained locally is doubled. This singularity is not acceptable because there is a risk of reaching the propellant contained inside the thruster.

[0010] Furthermore, the known processes only deal with non-through cutting by abrasive water jet, which has the disadvantage of presenting a high potential for pollution of the materials to be treated.

[0011] Document WO 20218 / 087701 discloses a method of non-through cutting according to the preamble of claim 1. Statement of the invention

[0012] The main aim of the present invention is therefore to propose a solution making it possible to cut only the body of a propellant of an aerospace vehicle, without altering the propellant contained inside the propellant in order to simplify the process of emptying a known propellant.

[0013] In a first aspect of the invention, a method for non-through cutting by water jets of a body of a propellant of an aerospace vehicle is proposed, the method comprising a plurality of passes of a high-pressure water jet along the same cutting path running around the external perimeter of the propellant body, the cutting path describing a closed-loop circuit, and each water jet pass starting from a starting point located on the cutting path and stopping just after passing back over the starting location.

[0014] According to a general characteristic of the invention, the starting point of each high-pressure water jet passage is different from the starting points of the other water jet passages.

[0015] The use of high-pressure water jet cutting allows for clean cutting quality (without delamination of the composite) and without significant heating as might be encountered with mechanical cutting, for example.

[0016] Furthermore, water jet cutting in several passes according to the invention, i.e. by shifting the starting point of the cutting path with each new pass, makes it easier to manage the transition phases, in other words the phase of the cutting pass during which the water jet passes back over its starting point and thereby generates a deeper cut than on the rest of the path for this same pass.

[0017] In fact, to make a complete cut, the jet must go back over the area where it has already passed in order to close the cut. By going back over an existing cutting line, the depth obtained locally is doubled compared to the rest of the path traveled during the same cutting pass.

[0018] The water jet cutting method according to the invention thus makes it possible to carry out a cut in a plurality of passes, or passages, by offsetting, at each pass, the singularity due to the closure of the path.

[0019] According to a first aspect of the non-through cutting method, at least the first high-pressure water jet pass may use an abrasive water jet.

[0020] Propellant bodies are generally composed of a stack of several different materials: cork on the outside forming an external thermal protection (PTE), then a composite material structure, then an internal thermal protection made of elastomer (PTI and detached skin). The body of the propellant contains propellant inside.

[0021] Using an abrasive water jet at the beginning of the cutting process, i.e. for the first pass(es) of the high-pressure water jet, allows cutting to begin cleanly, particularly for cutting the composite material layer, which is generally harder than the other layers. For such hard layers, using an abrasive water jet allows cutting to be carried out without creating delamination or fiber loosening.

[0022] According to a second aspect of the non-through cutting method, at least the last high-pressure water jet pass may use a pure water jet.

[0023] Using a pure water jet for the last pass(es) reduces the risk of pollution of the materials to be treated.

[0024] Pure water jet can be used after several passes with an abrasive water jet, especially after layers of hard material, such as composite materials, have been cut. Pure water jet can be used, for example, to cut a layer of elastomer without risk of water pollution.

[0025] According to a third aspect of the non-through cutting method, the method may further comprise, at each passage of a water jet, a step of detecting the end of cutting in order to control the cutting depth at all times and avoid altering the material contained in the propellant.

[0026] According to a fourth aspect of the non-through cutting method, the step of detecting the end of cutting may comprise applying a pulling force to a portion of the propellant body located on one side of the cutting path, and, if said pulled portion is displaced relative to the other portion, an indication of the end of cutting.

[0027] The method thus includes a step of tensioning the cut area, during each pass, or between passes, in particular the last passes, to directly assess how many passes are sufficient.

[0028] Furthermore, the use of the method according to the invention combining the offset of the starting point of each cutting pass, the use of an abrasive water jet for said at least one first pass and the use of a pure water jet for said at least one last pass, and an end of cutting detection makes it possible to maximize the safety and efficiency of the method of cutting a propellant body making it possible to avoid altering the contents of the propellant body.

[0029] According to a fifth aspect of the non-through cutting method, the propellant body to be cut may have the shape of a cylinder closed at its two axial ends by outwardly curved covers, the body comprising a multi-layer wall comprising a stack from the outside to the inside of an external thermal protection layer, a layer of composite material, and an internal thermal protection layer, and the curved covers further having an elastomer skin intended to be in contact with the fuel contained in the body and separated from the internal thermal protection layer by a space, and the non-through cutting method may comprise a step of centering the cutting path on a curved cover, the cutting being carried out until the space separating the elastomer skin and the internal thermal protection layer is reached.

[0030] To prevent the contents of the propellant, usually the propellant, from being altered, the cut must be non-opening. And to ensure that the cut is large enough to remove the cover and allow access to the propellant without risking alteration of the propellant, the cut stops in the gap, that is, in the space between the elastomer skin and the internal protective layer, which is usually also made of elastomer.

[0031] The method according to the invention thus provides a solution making it possible to cut only the external thermal protection (PTE), the composite structure and the internal thermal protection (PTI) of a propellant body of an aerospace vehicle, without altering the propellant contained inside the propellant. Brief description of the drawings

[0032] Other characteristics and advantages of the present invention will emerge from the description given below, with reference to the appended drawings which illustrate an exemplary embodiment thereof without any limiting character. [ Fig. 1 ] There Figure 1 , already presented, schematically presents a sectional view of a known propellant. Fig. 2 ] There Figure 2 presents a flowchart of a method for non-through cutting of a propellant body according to an embodiment of the invention. Description of the embodiments

[0033] On the Figure 2 a flowchart of a method of non-through cutting by water jets of a propellant body of an aerospace vehicle according to an embodiment of the invention is presented.

[0034] The propellant body of the aerospace vehicle to be cut may have the shape of a cylinder closed at its two axial ends by outwardly curved covers. The body comprises a multi-layer wall comprising a stack, from the outside of the body towards the inside of the body, of an external thermal protection layer, a layer of composite material, and an internal thermal protection layer. The curved covers further have an elastomer skin intended to be in contact with the fuel contained in the body and separated from the internal thermal protection layer by a space.

[0035] To prevent the contents of the propellant, usually the propellant, from being altered, the cut must be non-opening. And to ensure that the cut is large enough to remove the cover and allow access to the propellant without risking alteration of the propellant, it is preferable for the cut to stop in the gap, that is, in the space between the elastomer skin and the internal protective layer, which is usually also made of elastomer.

[0036] To this end, the method according to the invention comprises, first of all, a first step 200 of centering the cutting path on a curved hood during which the cutting water projection system is centered opposite the starting point of the cutting of the propellant body to be cut.

[0037] In a second step 210, the method comprises a pass of a first cut, the first cut being carried out using an abrasive water jet, and the pass being carried out over the entire external circular perimeter of the cylindrical body.

[0038] Using an abrasive water jet at the beginning of the cutting process, i.e. for the first pass(es) of the high-pressure water jet, allows cutting to begin cleanly, particularly for cutting the composite material layer, which is generally harder than the other layers. For such hard layers, using an abrasive water jet allows cutting to be carried out without creating delamination or fiber loosening.

[0039] At the end of the pass, the method comprises a third step 220 in which the number of passes of the first cut carried out, i.e. of the cutting by abrasive water jet, is compared to a threshold of passes of the first cut.

[0040] If the number of passes made is less than the threshold, the second and third steps 210 and 220 are repeated. When the number of passes made is equal to the threshold, the method performs, in a fourth step 230, a pass of a second cut using a pure water jet. The use of a pure water jet for the last pass(es) makes it possible to reduce the risks of pollution of the materials to be treated.

[0041] Pure water jet can be used after several passes with an abrasive water jet, especially after layers of hard material, such as composite materials, have been cut. Pure water jet can be used, for example, to cut a layer of elastomer without risk of water pollution.

[0042] Each first or second cutting pass is performed around the entire circular perimeter of the propellant body. And each pass, that is, each passage, of a pure water jet or an abrasive water jet, is performed by projecting a high-pressure water jet along the same cutting path running around the outer perimeter of the propellant body.

[0043] The cutting path thus described during each pass is a closed loop circuit. And each water jet pass, abrasive or pure, begins from a starting point located on the cutting path and stops just after passing back over the starting location. The path traveled by the water jet during each pass is therefore longer than the closed loop formed by the cutting path, in other words longer than the circular perimeter of the body.

[0044] The starting point of each high-pressure water jet pass, whether pure or abrasive, is therefore different from the starting points of the other water jet passes, whether previous or subsequent passes.

[0045] After each second cutting pass, the method performs, in a fifth step 240, a detection of the end of cutting of the body cover. The step of detecting the end of cutting comprises in this example the application of a traction force on a part of the propellant body located on one side of the cutting path, and, if said towed part is moved relative to the other part, an indication of the end of cutting in a last step 250, since it reflects the fact that the cutting has reached the space separating the elastomer skin and the internal thermal protection layer.

[0046] The method according to the invention thus provides a solution making it possible to cut only the external thermal protection (PTE), the composite structure and the internal thermal protection (PTI) of a propellant body of an aerospace vehicle, without altering the propellant contained inside the propellant.

Claims

1. A method for cutting, in a non-through manner, a body of a thruster of an aerospace vehicle, using water jets, said cutting being made along a cutting path describing a closed loop circuit, characterized in that the method comprises a plurality of passes of a high-pressure water jet (210, 230) along the same cutting path extending across the external perimeter of the thruster body, each water jet passage starting from a starting point located on the cutting path and stopping just after returning on the starting location, characterized in that the starting point of each high-pressure water jet pass is different from the starting points of the other water jet passes.

2. The non-through cutting method according to claim 1, wherein at least the first high-pressure water jet pass (210) uses an abrasive water jet.

3. The non-through cutting method according to any of claims 1 or 2, wherein at least the last pass (230) of the high-pressure water jet uses a pure water jet.

4. The non-through cutting method according to any of claims 1 to 3, further comprising, at each pass of a water jet, a step of detecting the end of cutting (240).

5. The non-through cutting method according to claim 4, wherein the step of detecting the end of cutting (240) comprises the application of a pulling force on a portion of the thruster body located on one side of the cutting path, and, if said pulled portion is moved relative to the other portion, comprises an indication of the end of cutting (250).

6. The non-through cutting method according to any of claims 1 to 5, wherein the thruster body to be cut has the shape of a cylinder closed at both its axial ends by covers curved outwardly, the body comprising a multilayer wall including a stack, from outside to inside, of an external thermal protection layer, of a layer made of composite material and of an internal thermal protection layer, and the convex covers also having an elastomer skin intended to be in contact with the fuel contained in the body and separated from the internal thermal protection layer by a space, and the non-through cutting method comprises a step of centering (200) the cutting path on a convex cover, the cutting being carried out until the space separating the elastomer skin and the internal thermal protection layer is reached.