TURBINE BLADE COMPRISING A TWO-PHASE THERMAL CONTROL SYSTEM (HEAT PIPE)

Description

2 SUMMARY OF THE INVENTION The invention offers a solution to the problems mentioned above, by allowing the blades to be defrosted without requiring an external energy supply, electricity, or hot air. The turbine blade according to the invention, in particular a stator blade, 5 comprises: a leading edge, a trailing edge, an intrados surface and an extrados surface extending from the leading edge to the trailing edge, the whole constituting the body of the blade, a head and a foot, the blade comprising a hollow part extending from the head to the body, the hollow part comprising a capillary heat pipe comprising a reservoir and a circuit extending from the head to the body, and a fluid 10 in a liquid-vapor equilibrium state filling said reservoir in the total absence of any other gas in said reservoir, said fluid being configured to circulate in the heat pipe during deformation of temperature gradients on the reservoir.The heat pipe is a two-phase thermal control system. It has the advantage of being passive and therefore does not require energy. Furthermore, it has demonstrated long-term reliability (15 to 20 years) in space applications. This results in a self-heating blade, making it more robust and lighter to manufacture. Thanks to the heat pipe, in icing conditions, the reservoir at a higher temperature is chosen to act as the evaporator, while the blade body acts as the condenser. The fluid is a heat transfer fluid in a liquid state within the reservoir; it vaporizes, absorbing thermal energy emitted by the heat source. The vapor then circulates within the blade body where it takes a second to return to a liquid state. Condensation allows thermal energy to be transferred to the cold source and thus defrosts the blade. Heat transfer capacities can range from 25 to several hundred watts. Advantageously, the capillary heat pipe comprises a fluid in a liquid-vapor equilibrium state in the total absence of air or any other gas, the fluid being ammonia, ethanol, or acetone.Since the heat pipe is sealed, the fluid circulates between the hot and cold zones, heating the cold zone where the liquid is located. In the hot zone (or evaporator), corresponding to the blade head, the liquid evaporates and the vapor condenses in the zone to be cooled (or condenser), corresponding to the zone to be defrosted. The condensate, in liquid form, returns to the evaporator thanks to the capillary action developed in a porous surface that coats the inner wall of the heat pipe. The choice of fluid is made according to the target temperatures. Advantageously, the reservoir is located in the blade head. Placing the reservoir in the blade head allows it, when in operation, to be at a higher temperature than the body and thus allows it to be heated. Advantageously, the circuit winds through the blade body. The winding circuit allows for heating of a larger surface area of ​​the blade body. The shape of the circuit can vary depending on the size and geometry of the blade. Advantageously, the circuit is located on the leading edge side.The leading edge is one of the areas most exposed to cold, because the cold air arrives there first. Advantageously, the circuit is arranged on the trailing edge side. The trailing edge is also an exposed area.15 The invention also relates to a first method of manufacturing a blade having at least one of the preceding characteristics, characterized in that it comprises the following steps: -additive manufacturing of the blade in which the hollow part is integrated, -then depowdering of the blade produced,20 -injection of the fluid into the hollow part, -sealing of the hollow part. The blade produced by additive manufacturing can, for example, be printed in a laser powder bed fusion (LPBF) machine with an integrated circuit and the fluid reservoir. The powder used can be aluminum. The printed blade thus includes a circuit in which fluid can circulate and a reservoir.After printing, the blade is depowdered and the fluid is then injected into the internal volume thus created. The circuit and the reservoir are then sealed by brazing, gluing, or any other mechanically attached element. Additive manufacturing or 3D printing makes it possible to create a circuit with a shape that is difficult to achieve by conventional processes. BE2025 / 5348 4 The invention also relates to a second method for manufacturing a blade having at least one of the preceding characteristics, the method comprising the following steps: - sintering with insertion of a ceramic core into the sintering mold, the ceramic core having the shape of a circuit in which fluid can circulate, - removal of the ceramic core, - injection of the fluid in place of the ceramic core, - sealing of the conduit. When the blade is sintered with metal powder, the internal volume is obtained with a ceramic core integrated into the sintering mold. After sintering, the ceramic core is removed, for example, by cold treatment or by chemical dissolution.Sintering allows for the industrial production of parts with high strength. The invention also relates to a third method for manufacturing a blade 15 having at least one of the preceding characteristics, which comprises the following steps: - forging with a machined or forged groove, - fixing the circuit, - positioning the reservoir, 20 - injecting the fluid - plugging the alopipe. The forging is done either with a groove in the body and / or a hollow in the head, made during the last forging operation, or without; in the latter case, the part must be machined to create this groove and / or hollow. The alopipe circuit 25 can then be fixed in the groove thus formed by brazing or bonding, for example. A reservoir is then brought into the hollow of the blade and sealed to the circuit. The heat transfer fluid is then injected into the internal volume thus created and sealed either by brazing, gluing or any other mechanically added element.Since the circuit is in relief, to recover the aerodynamic profile of the blade, it is possible to coat the circuit with a cold spray coating, or with a high-levelling electrolytic coating. BE2025 / 5348 5 Another object of the invention relates to a turbomachine comprising a blade having at least one of the preceding characteristics. Other advantages will also become apparent to those skilled in the art upon reading the examples below, illustrated by the attached figures, given for illustrative purposes. BRIEF DESCRIPTION OF THE FIGURES 5 The figures are presented by way of indication and in no way limit the invention. [Fig. 1] shows the operation of a heat pipe represented schematically; [Fig.2] is a cross-sectional view of a blade of the invention produced according to a first manufacturing method; [Fig.3] is a cross-sectional view of a blade of the invention produced according to a second manufacturing method; [Fig.4] is a cross-sectional view of figure2; [Fig.5] is a cross-sectional view of a blade of the invention produced according to a third manufacturing method before the installation of the cable. 15 DETAILED DESCRIPTION Unless otherwise specified, the same element appearing in different figures has a single reference. Throughout the description, the upper part of figures 2, 3 and 5 will be called "top" or "upper", and the lower part of said figures will be called "bottom" or "upper". The part located upstream in the direction of the airflow will be called "upstream" and the part downstream in the direction of the airflow will be called "downstream". As schematically illustrated in Figure 1, the heat pipe 1 comprises a sealed enclosure 10 filled with a fluid 11 in equilibrium between its liquid form 110 and its gaseous form 111. A first zone 13 is exposed to heat C (called 25 evaporator), heat which causes the liquid to evaporate into a gas which will cool down by condensing and become liquid in a second zone 14 (called condenser) BE2025 / 5348 6 emitting heat R. The heat pipe will therefore cool the hot zone 13 and heat the cold zone 14.The enclosure comprises several walls 100, 101, 102 and 103, a hot end wall 103, a cold end wall 101 and two walls 102 and 104 connecting the end walls 101 and 103. The walls 102 and 104 are covered internally with a capillary network 12 connecting the hot zone 13 and the cold zone 14. The liquid form 110 of the fluid circulates from the cold zone 14 to the hot zone 13 via the capillary network while the gaseous form 111 of the fluid emitted in the hot zone 13 moves towards the cold zone 14. Figure 2 shows an example of a blade 2 according to the invention, which includes a heat pipe 10. Air A flows along the upwind / downwind axis. The blade 2 comprises a leading edge 20 located at the upwind end and a trailing edge 21 located at the downwind end, a foot 22 positioned at the bottom, a body 23 and a tip 24 positioned at the top, an intrados 25 and an extrados 26 (see Figure 4). The heat pipe 1 includes a reservoir 130 located in the tip 24 of the blade 2 and a circuit 140 disposed in the body 23. The circuit 140 consists of a certain number of loops 140a, 140b, and 140c, here three, but it may have only one, two, or more than three without departing from the scope of the present invention.The circuit 140 is preferably extended along the entire height of the wing body 23 and the reservoir 130 along the entire height of the wing head 24. The wing head 24 is in a warm zone while the wing body 23 is in the airflow A which is particularly cold at altitude. The leading edge 20 is particularly exposed since the air A hits it first; therefore, it is on this part of the wing that icing can occur and which needs to be heated. The circuit 140 will therefore be positioned closer to the leading edge 20 than to the trailing edge 21. This blade 2 of Figure 2 can be produced by additive manufacturing using Laser Powder Bed Fusion (LPBF) technology. The powder used will be aluminum. The blade 2 will be printed with a hollow section for the circuit 140 and the reservoir 130. Once the blade 30 is finished and the powder is removed, the fluid is injected into the reservoir 130 and the circuit 140, and then the resulting calocopipe 1 is plugged. The plugging can be done either by brazing, gluing, or inserting a plug.The blade 1 of figures 3 and 4 is externally identical to the blade of figure 2, but it is made differently. The heat pipe 1 comprises a reservoir 130 and a circuit 141 with several branches 141a, 141b, 141c parallel to each other. In the example illustrated in figure 4, the branches 141a and 141b, 141 and 141c are equidistant, but they can be closer together towards the leading edge 20 and / or not be parallel to each other without going out of the scope of the present invention. It is produced by sintering a metallic powder. The hollow part of the circuit 141 and the reservoir 130 is obtained by integrating a ceramic core into the sintering mold. This core has the shape of the circuit 141 and the reservoir 130. Once the sintering is complete, the ceramic core is removed by chemical dissolution or by cooling, which leads to the rupture of the ceramic through a phenomenon of differential expansion. The aubedel.

Images