CH472571A - Turbomachine blade, and method of manufacturing said blade - Google Patents

Description

Turbomachine blade, and process for manufacturing said blade The invention relates to a turbomachine blade comprising a sealed cavity containing a substance present under normal operating conditions of the blade, both in liquid and vapor phase.

When such a vane is subjected externally, at one of its ends, to a flow at a high temperature, and at its other end, to a flow at a lower temperature, this substance, for example a molten metal such as sodium, plays in known manner, a heat transfer role from one end to the other of the blade, and can contribute to the uniformity of the blade to a value not exceeding a predetermined limit.

This heat transfer is based, in the first place, on the natural convection which is established in the closed circuit constituted by the sealed cavity.

In the cis of a rotor blade, this convection is favored considerably by the action of the centrifugal force which establishes, inside the blade, currents due to the differences in density, in the various zones of the blade. , heat transfer substance.

But this favorable factor does not come into play for fixed stator vanes, for which it is very difficult to establish a natural circulation, especially in the Gas of stator vanes located in the lower half of a turbine. Ort could consider forced circulation of the heat transfer medium, for example by means of a pump and an external circuit, but the complication brought about by such forced circulation (Problem of installation of metal pumps fluid on an aircraft, tightness of fittings and circuits, general reliability) is such that it does not allow, in practice, to retain such a solution. The problem of natural circulation, that is to say the problem of the return of the liquid phase from the zone where the condensation takes place towards Gelle where the vaporization takes place, therefore remains posed in the cry of fixed blades. and, in particular, in the gas of stator vanes.

A second difficulty encountered in the known installations is linked to the fact that the use, as heat transfer substance, of molten metal undergoing, in operation, a liquid-vapor phase change, leads to a only partial filling by the molten metal of the cavity provided for this purpose inside the blade. However, in the Gas where this molten metal is solid at the ordinary temperature, the solidification of the latter when the machine is stopped occurs, due to gravity, in preferential zones, namely the bisse part of the dawn, this bisse part being able to be found both at the foot and at the head of the dawn.

In the cis of rotor blades, this phenomenon causes the rotor carrying them to appear unbalanced when starting the turbomachine. In the cis of stator blades, the solidification of the liquid metal, in certain pv-eferential zones of the blade, leads for certain blades to the annihilation of the cooling of said blades, the evaporation zones bathed in the start-up by the working fluid of the turbomachine then being devoid of molten heat transfer metal.

Another difficulty encountered in the gas of known hollow blades is the cooling of the trailing edge region of the blade. The latter being very slender and the molten metal channels being almost circular, an encounter, for lack of space, a limitation of a technological nature to accommodate such a channel along the trailing edge of the blade.

The dawn that the invention comprises is characterized by the first fact that the sealed cavity internally presents a capillary network imprzgne by the substance in the liquid phase.

According to one embodiment of the invention, the capillary network is constituted by a set of grooves made on the interior wall of the cavity. According to another embodiment, the capillary network is constituted by a fine-mesh fabric lining the interior wall of the cavity.

The capillary structure acts in all the Gas as a wick and ensures the pumping of the liquid phase which circulates through this capillary structure from the cold part of the blade (where there is condensation) towards the hot part (where vaporization takes place), while in the central cavity, bordered by the wick, the vapor circulates in the opposite direction, that is to say from the evaporator towards the condenser.

It will be noted that at Parret, the molten metal saturates the capillary structure and solidifies therein in situ with a homogeneous distribution, so that the heat-transmitting metal is in the desired zones when the machine is started. .

It will be noted, moreover, that the circulation of mCal liquid does not require the arrangement in the mass of Taube of special channels having a certain transverse bulk, but of a simple extremely fine capillary structure, an can easily ash this one to the trailing edge mine of dawn.

The invention also comprises a process for the manufacture of the hollow blade according to the invention, characterized in that the capillary network is managed beforehand on the wall of a sheet, that said sheet is then folded in such a way as to form a leading edge and that the two folded ends of the sheet are welded so as to form a trailing edge.

The appended drawing illustrates, by way of example, two embodiments of the blade according to the invention.

fig. 1 illustrates very schematically the phenomenon implemented in the present invention.

Figs. 2 and 3 are schematic cross-sections of Ges two forms of Paube execution.

fig. 4 is a schematic axial half-section by tial illustrating the application of the invention in the context of turbofan engines.

In fig. 1, an has represented in a rudimentary way a hollow blade 1 containing sodium in the liquid phase and in the gaseous phase, this blade being exposed, on the one hand, at <B>1</B> a, to a flux at a high temperature said flux hot F and, on the other hand, in 1b, at a flow at lower temperature called cold flow F'.

Under the effect of the heat of the hot flux F On Part la of Paube, sodium in the liquid state is transformed into vapor and the vapor moves according to the arrow f from Part la towards Part 1b where it is located. condenses under the effect of cooling exerted by the cold flow F. The resulting liquid sodium returns RTI ID="0002.0276" WI="8" HE="4" LX="812" LY="2105"> then to Part 1 a according to arrow f'.

A transfer of heat is thus established between two geometrically distinct places la and 1b, by phase change of the sodium: evaporation in the hot zone la which plays the role of evaporator and condensation in the cold zone 1b which therefore plays the role of condenser, assuming that the sodium vapor moves from the evaporator la to the condenser lb along the arrow f and that the liquid sodium performs the reverse course along the arrow f'.

In the representation shown, Part 1 a of Tau be is the head and Part 1 b is the foot.

The return movement of the liquid phase in the direction of the evaporator (arrow f') is ensured by capillarity using a wick. This wick can be incorporated and constituted by a body of capillary structure 2 (fig. 2) obtained very simply by longitudinal and possibly transverse grooving of the mine wall of the hollow blade 1, the internal capacity 3 of the latter allowing the circulation of steam.

As a variant, the wick can be attached and constituted by a fine-mesh metal screen 4 lining the wall of the hollow blade 1 (FIG. 3).

In both Gases, the capillary network is thin enough to be extended to the lowest trailing edge of the blade, however thin it may be. Ort will benefit from making the hollow blade in a manner known per se from a sheet metal bent around the leading edge and welded along the trailing edge, the capillary network 2 or 4 being laid out beforehand.

Thus, the hollow Taube 1 is in the form of a sealed capsule which constitutes a bar of almost infinite conductivity transferring, under a small temperature difference, the heat from the zone la exposed to the hot gases F towards Gelle 1b exposed to the cooling fluid F .

fig. 4 represents a double-flow turbojet engine called a turbofan, of which at 5 the fan or low-pressure compressor is seen, at 6 the high-pressure compressor, at 7 the combustion chamber, and at 8 the moving blades of the turbine. The hot internal primary flow is separated from the cold external secondary flow by a casing 9.

In the application of the invention to such a turbofan, the secondary air coming from the fan 5 is used for the cooling of the root of the fixed blades 1, which makes it possible to have a large flow of air as well as an exchange surface which can be developed considerably in the form of a kind of radiator 10 external to the dispenser.

One of the appreciable advantages of RTI ID="0002.0549"WI="7" HE="4" LX="1777" LY="1540"> this solution is that it does not require any special air sampling at the compressor, which would be to the detriment of the thermodynamic efficiency of the machine, as is the case with Gas for current solutions where Fon uses a high-pressure air sample at a low flow rate, this sample having to be necessarily limited.

Claims (6)

CLAIMS I. Turbomachine blade, comprising a sealed cavity containing a substance occurring, Jans lös normal operating conditions of the blade, both in the liquid phase and in the vapor phase, characterized by the fact that the sealed cavity internally presents a capillary network impregnated by the substance in the liquid phase. 1I. Process for the manufacture of blade according to claim I, characterized in that the capillary network is managed beforehand on the wall of a sheet, that said sheet is then folded over so as to form a leading edge and that the two folded ends of the sheet are welded so as to form a trailing edge. SUB-CLAIMS 1. Turbomachine blade according to claim I, characterized in that the first capillary network is constituted by a set of grooves made on the wall of the cavity. 2. Turbomachine blade according to claim 1, characterized in that the capillary network is constituted by a fine-mesh fabric lining the interior wall of the cavity. 3. Turbomachine blade according to claim 1, characterized in that it comprises a first zone intended to be exposed externally to the action of heat, and a second zone intended to be exposed externally to the action of a cooling fluid. cooling. 4. Turbomachine blade according to claim 1 and sub-claim 3, characterized in that it comprises, in the zone intended to be exposed to the cooling fluid, a set of fins. 5. Turbomachine blade according to claim 1, characterized in that the first capillary network extends to the trailing edge of the blade. 6. Turbomachine blade according to claim 1, characterized in that the substance contained in the cavity of the blade consists, at least partially, of a molten metal or alloy, such as sodium.