EP1462617B1 - Blading for an axial-flow turbomachine - Google Patents

Description

Technical area

The invention relates to the field of power plant technology. It relates to an axial flow thermal turbomachine according to the preamble of claim 1, which has a reduced rotor weight compared to the known prior art.

State of the art

Thermal turbomachinery, z. As high-pressure compressor for gas turbines or turbines consist essentially of a rotor equipped with blades and a stator, are hung in the vanes. The blades and vanes each have an airfoil and a blade root. To be able to fasten the blades on the rotor or in the stator, grooves are inserted in the stator and on the rotor shaft. In these grooves, the feet of the guide vanes and blades are inserted and locked there.

The fixed guide vanes have the task of directing the flow of the compressed or the gaseous medium to be relaxed on the rotating rotor blading so that the energy conversion takes place with the best possible efficiency.

It is known, blades in one piece from a single material, for. B. stainless steel for gas turbine compressor or a nickel-based superalloy for gas turbines to produce and to equip with these similar blades a row of blades. Such blades are hereinafter referred to as conventional blades.

For certain applications, the average mass of a row of blades is limited by the carrying capacity of the rotor.

Therefore, solutions have become known to produce blades in hybrid construction. In the hybrid construction method, different materials with different physical properties are combined with one another to produce a blade, in order to obtain an optimum design of a blade. So z. B. a hybrid rotor blade for an engine DE 101 10 102 A1 known, in which the trailing edge of the airfoil, which has only an aerodynamic function, made of a lightweight material, preferably a fiber composite material, for. As carbon fiber composite material is produced. By such a (slight) trailing edge can be advantageous to reduce the weight of the blade. The connection of the two airfoil parts (heavy metal leading edge and light trailing edge made of fiber composite material) is done by gluing or riveting.

A similar solution is in WO 99/27234 described. There is disclosed a rotor with integral blading, in particular for an engine, are circumferentially arranged on the rotor blades, wherein the rotor blade to reduce vibrations, a metallic blade root, a metallic blade leaf portion, at least part of the Blade leading edge and the adjoining portion of the blade surface, and having a blade made of fiber reinforced plastic. Again, the attachment of the blade made of plastic to the metallic blade section by gluing / riveting or by clamping takes place.

This known prior art has the following disadvantages. On the one hand, the mentioned types of fastening do not withstand great loads over a long period of time; on the other hand, the fiber-reinforced plastics can only be used in certain temperature ranges, so that these known technical solutions are suitable in particular only for engine technology. In addition, the characteristic of the airfoil (mechanical properties, oxidation resistance, friction properties) is changed compared to the blades made of a single material, which can adversely affect the performance of the machine.

Furthermore, it is off EP 0 513 407 B1 a turbine blade made of an alloy based on a dopant-containing gamma titanium aluminide known which consists of the blade, blade root and possibly blade shroud. In the production of this blade, the cast body is partially heat-treated and hot-formed so that the blade then has a coarse-grained structure, which leads to high tensile and creep strength, and that the blade root and / or the blade cover strip has a fine-grained structure facing one Increased ductility leads to the airfoil.

While the use of these gamma-titanium aluminide blades advantageously reduces the mass of the rotor as compared to conventional blades, it is disadvantageous in this prior art that the blade tips burst away due to their brittleness when in contact with the blade Stator come into contact. This friction is usually unavoidable.

Experiences with steel blades in high-pressure compressors have shown that even with so-called abrading layers on the stator, the blade tips of the blades can be ground during operation of the compressor. This is associated with a considerable frictional force which results in a blade burst if the blade is not ductile.

From the document DE 44 39 726 A1 is an impeller for use in a turbomachine, which is the promotion of a dirt-laden gas, such as a flue gas known. In order to avoid dirt deposits, at least one arranged between the blades enlarged blade is provided on the impeller, the tips of a corrosion-resistant material, such as high-strength steel or titanium, or the total may also consist of such a material. Preferably, armor and / or armor are provided at the tip of each enlarged blade to maintain a clearance in the dirt deposited near the impeller through which the other blades can pass away from the dirt, thus causing friction problems and associated overhead Energy to operate the turbomachine can be prevented.

In the document U.S.-A-5,474,421 an impeller of a turbomachine, in particular a turbine of a gas turbine engine is described, which is alternately equipped with blades of the same shape and size, but lesser and greater mass, the blades of lesser mass consist of intermetallic compounds and the heavier blades are made of high-alloy high-temperature metallic materials , The lightweight blades can support themselves at comparatively high bending stress in each case on the next, for example, consisting of a metallic superalloy blade. The high bending stress can be caused, for example, by a hard stripping operation of the relevant blade tip on the housing. Since every second blade compared to turbine wheels, which are made entirely with blades made of a high-alloy temperature-resistant material, is relatively lightweight, the entire rotor is lighter. However, this solution has the disadvantage that, because of the different vibration behavior of the blade materials, expensive precautions must be taken to dampen the vibration.

Presentation of the invention

The aim of the invention is to avoid the mentioned disadvantages of the prior art. The invention is based on the object to develop a thermal turbomachine, which is characterized on the one hand by a reduced total weight of the rotor, and in the other hand, a blade brittle fracture is prevented, so that the life of the machine is increased.

According to the invention this object is achieved in a thermal turbomachine according to the preamble of claim 1, characterized in that at least two uniformly spaced blades are arranged from a ductile material in a row of blades between the intermetallic blades, the blades of the ductile material are either significantly longer than the intermetallic Shovels or the same length have a different blade tip shape than the intermetallic blades, namely blunted blade tips.

The advantages of the invention are that the use of the blades of intermetallic compounds on the one hand, the weight of the rotor is reduced, which leads to an increase in the life of the rotor / blade connection and on the other hand, the brittleness of the intermetallic blades no increased risk for the operation of the machine means that the arranged in the same blade row blades made of the ductile material absorb the frictional / Verschieisskräfte.

It is expedient if, in addition, intermediate pieces made of a lighter material than the rotor material, preferably an intermetallic compound or a titanium alloy, are arranged in the rotor between the rotor blades of a blade row. In this way, the weight of the rotor is additionally reduced.

It is also advantageous if the intermetallic blades and the intermediate pieces consist of an intermetallic γ-TiAl compound or an intermetallic orthorhombic TiAl compound, because this inventive use of material leads to a considerable weight reduction of the rotor. The specific gravity of the intermetallic titanium-aluminide compounds is z. B. only about 50% of the density of stainless Cr-Ni-W steel.

Finally, it is advantageous if the blade tips are coated with a hard phase or by laser welding a wear protection layer is applied to prevent the grinding of the blade tips or to reduce the frictional force.

Brief description of the drawings

Fig. 1

einen Querschnitt durch eine Laufschaufelreihe eines schematisch dargestellten erfindungsgemässen Hochdruckverdichters in einer ersten Ausführungsvariante;

Fig. 2

ein Detail einer zweiten Ausführungsvariante der Erfindung, bei welcher zwischen den Laufschaufeln Zwischenstücke aus intermetallischen Verbindungen im Rotor angeordnet sind und

Fig. 3

eine TiAl-Schaufel mit einer beschichteten Schaufelspitze als dritte Ausführungsvariante der Erfindung.

In the drawing, several embodiments of the invention are shown. Show it:

Fig. 1

a cross section through a blade row of a schematically illustrated inventive high pressure compressor in a first embodiment;

Fig. 2

a detail of a second embodiment of the invention, in which between the blades intermediate pieces of intermetallic compounds are arranged in the rotor and

Fig. 3

a TiAl blade with a coated blade tip as a third embodiment of the invention.

In the figures, the same positions are respectively provided with the same reference numerals.

Ways to carry out the invention

Hereinafter, the invention of embodiments and the FIGS. 1 to 3 explained in more detail.

Fig. 1 shows a cross section through a schematically illustrated blade row of a rotor 1 for a high-pressure compressor of a gas turbine. The rotor 1 is surrounded by a stator 2. In the rotor 1 in a circumferential groove located therein blades 3, 3 'are mounted, while in the stator 2, not shown here vanes are mounted. For example, the blades 3, 3 'are exposed to a temperature of approximately 600 ° C. for several thousand hours at a pressure of approximately 32 bar.

According to the invention, the illustrated blade row is equipped with two different types of blades 3, 3 '. For the purpose of weight reduction, the majority of the blades, namely the blades 3, are made of an intermetallic compound, preferably a gamma titanium aluminide compound. On the other hand, the blades 3 'are made of a more ductile material, such as a stainless Cr-Ni steel, as the material for the blades 3. At least two evenly spaced such ductile blades 3 (According to Fig. 1 in the present embodiment, these are four pieces) are arranged in the blade row of the intermetallic blades 3. The blades 3 'of the ductile material are significantly longer in this embodiment than the intermetallic blades 3, ie in case of accidental contact of the Shoveling with the stator during operation allows these more ductile blades to absorb frictional forces without causing brittle fracture. In another embodiment, to achieve the same effect, both blade types 3, 3 'can also have the same length but different shapes of the blade tip 5, as the more ductile blades 3' have blunt blade tips 5.

In the present exemplary embodiment, the rotor blades 3 'consist of a stainless steel with the following chemical composition (in% by weight): 0.12 C, <0.8 Si, <1.0 Mn, 17 Cr, 14.5 Ni, <0.5 Mo, 3.3 W, <1 Ti, <0.045 P, <0.03 S, balance Fe. The shaft of the rotor 1 is also made of steel. As is known, the density of steel is about 7.9 g / cm ³ . The intermetallic compound from which the blades 3 are made has the following chemical composition (in% by weight): Ti (30.5-31.5) Al- (8.9-9.5) W- (0.3-0.4) Si. The density of this alloy is advantageously only 4 g / cm ³ , so that the rotor 1 according to the invention is substantially lighter than a rotor with exclusively conventional steel blades.

Fig. 2 shows a further embodiment of the invention in a detailed representation. The weight of the rotor 1 can be additionally reduced if - as in Fig. 2 shown - between two adjacent blades of a row of blades of the rotor 1 each intermediate pieces 4 of an intermetallic compound, here of a γ-titanium-aluminide compound, are mounted in the circumferential groove of the rotor 1.

The intermetallic compound used for the production of the intermediate pieces 4 has the same chemical composition as the compound used for the blades 3 and described above.

Titanium-metal intermetallic compounds with aluminum have some interesting properties that make them attractive as engineering materials in the medium and higher temperature range. This includes their opposite Superiegierungen and against stainless Steels lower density. However, their technical usability often stands in the way of their brittleness.

The above-described γ-titanium-aluminide intermetallic compound is characterized by about 50% lower density than the steel used in this embodiment for the rotor 1 and the blades 3 '. Furthermore, it has an E-modulus at room temperature of 171 GPa and a thermal conductivity λ of 24 W / mK.

Table 1 compares the physical properties of the two alloys. Table 1: Physical properties of the different materials Density in g / cm ³ Thermal expansion coefficient in K ^-1 γ-Ti-Al 4 ^{10x10 -6} Stainless steel 7.9 18.6 x 10 ^-6

Since the rotating components of the high pressure compressor of a gas turbine plant are stressed at temperatures up to about 600 ° C, the weight reduction of the inventive rotor 1 has an advantageous effect on increasing the life of the machine. The stresses in the blade root fixation in the rotor 1 are reduced.

The production of the intermetallic blades 3 and the intermediate pieces 4 is carried out in a known manner by casting, hot-isostatic pressing and heat treatment with a minimum of mechanical post-processing.

In Fig. 3 a further preferred embodiment is shown. It is shown a blade 3, the blade tip 5 is coated. The coating of the blade tip can be done with a hard phase or it can by means of laser welding a wear protection layer be applied. In both cases, the grinding of the blade tips is prevented or reduces the frictional force.

Of course, the invention is not limited to the described embodiments.

For example, an orthorhombic titanium-aluminide alloy having a density of 4.55 g / cm ³ can also be used as the material for the intermetallic blades 3 or the intermediate pieces 4. Orthorhombic titanium aluminide alloys are based on the ordered compound Ti ₂ AlNb and have the following chemical composition in (% by weight): Ti (22-27) Al- (21-27) Nb.

The intermediate pieces 4 can also be made of a cheaper titanium alloy instead of a gamma titanium-aluminide intermetallic compound, in which case the weight reduction is not quite as strong.

Furthermore, it is conceivable that the invention is used not only for high-pressure compressor rotors but also for turbine rotors with turbine blades made of known turbine steel, heat-resistant steel or a superalloy, for example a nickel-based superalloy, in which the intermediate pieces between the blades of an intermetallic γ Titanium-aluminide alloy or an intermetallic orthorhombic titanium-aluminide alloy. This can also be advantageous to achieve weight reductions and increase the life of the machine.

Their brittleness does not play a disadvantageous role for the described use according to the invention of the Ti-Al intermetallic alloys, since they are not exposed to any sliding contact or frictional wear when used as intermediate pieces and the frictional / wear forces are absorbed by the corresponding more ductile blades when used as a blade.

LIST OF REFERENCE NUMBERS

1

rotor

2

stator

3, 3 '

blade

4

connecting piece

5

blade tip

Claims (8)

1. Axial-flow thermal turbomachine having a metallic rotor (1), in which rotor blades are mounted in a circumferential groove to form a row of blades, the plurality of rotor blades of a row of blades being rotor blades (3) made of an intermetallic compound, characterized in that at least two rotor blades (3') which are at a uniform distance from one another and are made of a more ductile material are arranged in said row of blades between the intermetallic rotor blades (3), and the rotor blades (3') made of the more ductile material either are considerably longer than the intermetallic blades (3) or, if they are of the same length, have blunted blade tips (5) which are of a different blade tip shape than the intermetallic blades (3).
2. Turbomachine according to Claim 1, characterized in that intermediate pieces (4) made of a more lightweight material than the material of the rotor (1), preferably made of an intermetallic compound or a titanium alloy, are additionally arranged between two adjacent rotor blades (3, 3') of a row of blades.
3. Turbomachine according to Claim 1 or 2, characterized in that the intermetallic compound is a γ-titanium aluminide alloy or an orthorhombic titanium aluminide alloy.
4. Turbomachine according to Claim 3, characterized in that the γ-titanium aluminide alloy has the following chemical composition (in % by weight): Ti-(30.5-31.5)Al-(8.9-9.5)W-(0.3-0.4)Si.
5. Turbomachine according to one of Claims 1 to 4, characterized in that the blade tips (5) of the rotor blades (3) are coated with a hard phase.
6. Turbomachine according to Claim 5, characterized in that a wear-resistant layer is applied to the blade tips by means of laser welding.
7. Turbomachine according to one of Claims 1 to 6, characterized in that the turbomachine is a highpressure compressor of a gas turbine with a rotor (1) which consists of a stainless Cr-Ni steel.
8. Turbomachine according to one of Claims 1 to 7, characterized in that the rotor blades (3') which are more ductile than the intermetallic rotor blades (3) consist of a stainless Cr-Ni steel or a heat-resistant turbine blade steel or a superalloy.

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