WO2006111520A1 - Turbine rotor and turbine engine - Google Patents

Turbine rotor and turbine engine Download PDF

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Publication number
WO2006111520A1
WO2006111520A1 PCT/EP2006/061626 EP2006061626W WO2006111520A1 WO 2006111520 A1 WO2006111520 A1 WO 2006111520A1 EP 2006061626 W EP2006061626 W EP 2006061626W WO 2006111520 A1 WO2006111520 A1 WO 2006111520A1
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WO
WIPO (PCT)
Prior art keywords
shaft part
turbine rotor
turbine
hot
cool
Prior art date
Application number
PCT/EP2006/061626
Other languages
French (fr)
Inventor
Andrew Shepherd
Paul Mathew Walker
Original Assignee
Siemens Aktiengesellschaft
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Siemens Aktiengesellschaft filed Critical Siemens Aktiengesellschaft
Publication of WO2006111520A1 publication Critical patent/WO2006111520A1/en

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
    • F01D5/00—Blades; Blade-carrying members; Heating, heat-insulating, cooling or antivibration means on the blades or the members
    • F01D5/02—Blade-carrying members, e.g. rotors
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C19/00—Alloys based on nickel or cobalt
    • C22C19/03—Alloys based on nickel or cobalt based on nickel
    • C22C19/05—Alloys based on nickel or cobalt based on nickel with chromium
    • C22C19/051—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W
    • C22C19/055—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W with the maximum Cr content being at least 20% but less than 30%
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C19/00—Alloys based on nickel or cobalt
    • C22C19/03—Alloys based on nickel or cobalt based on nickel
    • C22C19/05—Alloys based on nickel or cobalt based on nickel with chromium
    • C22C19/051—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W
    • C22C19/056—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W with the maximum Cr content being at least 10% but less than 20%
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
    • F01D5/00—Blades; Blade-carrying members; Heating, heat-insulating, cooling or antivibration means on the blades or the members
    • F01D5/02—Blade-carrying members, e.g. rotors
    • F01D5/022—Blade-carrying members, e.g. rotors with concentric rows of axial blades
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05C—INDEXING SCHEME RELATING TO MATERIALS, MATERIAL PROPERTIES OR MATERIAL CHARACTERISTICS FOR MACHINES, ENGINES OR PUMPS OTHER THAN NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES
    • F05C2201/00—Metals
    • F05C2201/04—Heavy metals
    • F05C2201/0433—Iron group; Ferrous alloys, e.g. steel
    • F05C2201/0466—Nickel

Definitions

  • the present invention relates to a turbine rotor, in particular a gas turbine rotor, which comprises a hot shaft part being operable at a high temperature and a cool shaft part being operable at a lower temperature than the high temperature.
  • the invention relates to a turbine engine, in particular a gas turbine engine, comprising such a rotor .
  • Gas turbine engines in particular axial gas turbine engines, comprise a compressor section, a combustor section and a turbine section which are arranged after each other in an axial direction and through which a turbine rotor extends in the axial direction.
  • the turbine rotor may be supported on plain, hydrodynamic bearings.
  • the bearing journal of such bearings is usually arranged in a part of the rotor which is not exposed to a high temperature.
  • the bearing journal is arranged in a so-called exit shaft part of the rotor which adjoins the compressor shaft part, which extends through the compressor section, towards the combustor section.
  • the temperature of the rotor in the compressor section, in particular at the compressor exit, is rather high during operation of the gas turbine engine compared to the temperature of the exit shaft part due to the compression of air in the compressor section.
  • gas turbine engines it is common practice to use a low alloy carbon steel for the bearing journal of the turbine rotor, and a high alloy steel or nickel based alloy for the rotor components that operate at high temperatures.
  • a difficulty is that the different materials need to be joined together, which leads to difficulties in reliability and an increase of costs.
  • high alloy steels are used for exit shafts, i.e. steels with a chrome fraction of about 10% by weight.
  • steel containing more than 1% by weight chrome is prone to wire wooling, hence the journal surface is always protected by chrome plating, by cladding with low alloy steal (less than 1% chrome), or by using a low alloy steel sleeve.
  • Nickel alloy journals with low alloy steel sleeves are also known to be used.
  • Chrome plating is process sensitive, can have adhesion problems and is known to have caused bearing failures in the past. Cladding by welding process would overcome those issues, however the welding process is expensive. Added sleeves, on the other hand, can only be used where the journal diameter is not smaller than the end of the shaft. If an overhung construction where the bearing is located between the turbine discs and compressor rotor is used, the joint at the turbine discs is usually of a larger diameter than the bearing journal, so that the sleeve cannot be used.
  • the first objective is solved by a turbine rotor according to claim 1, the second objective by a turbine engine, in particular a gas turbine engine, according to claim 8.
  • a turbine engine in particular a gas turbine engine, according to claim 8.
  • An inventive turbine rotor comprises a hot shaft part, in particular a hot end shaft part, being operable at a high temperature and a cool shaft part, e.g. an exit shaft part as described in the introduction, being operable at a lower temperature than the high temperature.
  • the cool shaft part adjoins the hot shaft part.
  • High and low temperatures refers temperatures above and below 400 0 C, respectively.
  • both the cool shaft part and the hot shaft part are in metallic continuity and are composed from the same nickel based superalloy, in particular an austenitic superalloy, with nickel content in the range of 30 to 65 wt%.
  • the use of a nickel based superalloy with nickel content in the range of 30 to 65 wt% allows the turbine rotor to be formed from a single piece of metal in the hot shaft part and the cool shaft part.
  • the mentioned nickel based superalloy has been found to be suitable for forming the hot shaft part as well as the cool shaft part. It shows a high hot strength, is resistant to galling or rubbing wear on the bearing material, which is usually lead-bronze, and is not subject to wire wooling damage.
  • the mentioned nickel based superalloy has been shown to be able to withstand high compressive stress from running on rollers during balancing. In addition, it is suitable for use with inductive vibration monitoring probes.
  • the mentioned nickel based superalloy has a minimum hardness ratio relative to the bearing material and a suitable thermal expansion coefficient to maintain the required bearing clearances .
  • the inventive turbine rotor provides the following advantages: as the material is not prone to wooling damage, the use of a sleeve around the bearing journal, chrome plating on the bearing journal or cladding of the bearing journal is not necessary. Moreover, as the hot shaft part and the cool shaft part are composed of the same material it is possible to form both parts as one single seamless piece. Bolting the hot shaft part to the cool shaft part, which is the current state of the art, is less stable than a single seamless piece. Welding the hot shaft part to the cool shaft part is also known in the state of the art to be a viable solution. However this solution is expensive and may have difficulties regarding to life time of the welded joint.
  • the nickel based superalloy of which the hot shaft part and the cool shaft part are composed may comprise a chromium content above 10 wt%, in particular above 16%, for oxidation and/or corrosion resistance.
  • a chromium content above 10 wt%, in particular above 16%
  • steel with more than 3% chromium and in particular stainless steel with 12% chromium is usually subject to wire wooling
  • nickel based superalloys with a nickel content in the range of 30 to 65 wt% comprising a chromium content of at least 10 wt% are not prone to wire wooling.
  • a high chromium content, however, is desired for the bearing journal. If a steel shaft with 19% chromium were to be used one would expect to get wire wooling problems.
  • Suitable nickel based superalloys comprise:
  • the inventive turbine rotor may be provided with a bearing part being designed for reception into a bearing, e.g. with a bearing journal in the cool shaft part.
  • the cool shaft part may represent an exit shaft part and the hot shaft part a compressor shaft part which is designed to be arranged in a compressor section of a gas turbine engine.
  • the bearing journal is then arranged in the exit shaft part which adjoins the compressor shaft part.
  • the hot shaft part may comprise at least one rotor disc, e.g. a compressor disc in the case of the hot shaft part being at least a part of the compressor shaft part .
  • An inventive turbine engine which may in particular be a gas turbine engine, comprises an inventive turbine rotor.
  • the rotor may extend at least partly through a compressor section and at least partly through a combustor section of the gas turbine engine, where the hot shaft part of the rotor is located in the compressor section and the cool shaft part is located in the combustor section.
  • the advantages of the inventive turbine rotor can be used to increase the reliability of the turbine engine or to reduce the manufacturing costs.
  • Figure 1 shows a gas turbine engine in a sectional view.
  • Figure 2 shows a part of the rotor of the turbine engine shown in Figure 1 in detail.
  • FIG. 1 shows an example of a gas turbine engine 100 in a sectional view.
  • the gas turbine engine 100 comprises a compressor section 105, a combustor section 106 and a turbine section 112 which are arranged adjacent to each other in a longitudinal direction of a rotation axis 102. It further comprises a rotor 103 which is rotatable about the rotational axis 102 and which extends longitudinally through the gas turbine engine 100.
  • air 135 which is taken in through an air inlet 104 of the compressor section 105, is compressed by the compressor section and output to the burner section 106.
  • the temperature of the air raises to about 400 0 C to 700 0 C at the compressor exit 108.
  • the burner section 106 comprises one or more combustion chambers 110 and at least one burner 107 fixed to each combustion chamber 110.
  • the compressed air from the compressor exit 108 enters the burner 107 where it is mixed with a fuel, for example gas or oil.
  • the air fuel mixture is then burnt and the exhaust gas 113 from the combustion is led through the combustion chamber 110 to the turbine section 112.
  • a number of blade carrying discs 120 are fixed to the rotor 103 in the turbine section 112 of the engine. In the present example, two discs carrying turbine blades 121 are present.
  • guide vanes 130 which are fixed to a stator 143 of the gas turbine engine 100, are disposed between the turbine blades 121. Between the exit of the combustion chamber 110 and the leading turbine blades 121 inlet guide vanes 140 are present.
  • the exhaust gas from the combustion chamber 110 enters the turbine section 112 and transfers momentum to the turbine blades 121 which results in a rotation of the rotor 103.
  • the guide vanes 130, 140 serve to optimise the impact of the exhaust
  • the turbine rotor 103 is shown in Figure 2 in greater detail.
  • the figure shows a section of the rotor 103.
  • the shown section of the rotor 103 comprises a shaft 200 which comprises a cool shaft part 201 and a hot shaft part 203.
  • the hot shaft part 203 is formed from at least a part of the shafts compressor section, i.e. at least from that part of the shaft 200 which extends through the compressor and carries the last compressor disc 218 (compressor disc located at the compressor exit) .
  • the cool shaft part 201 is, in the present embodiment, an exit shaft part which adjoins the hot shaft part 203 in the combustor section 106.
  • the shaft 200 is supported by a bearing 205 in the exit shaft part 201.
  • the bearing 205 which is implemented as a hydrodynamic bearing, comprises a bearing race 207 and bearing journal 209 which is formed at the bottom of a recess 211 running around the circumference of the shaft 200.
  • a bearing clearance 213 is present between the bearing race 207 and the bearing journal 209. It is filled with a liquid or a gas supporting the load.
  • the material temperature of the cool shaft part 201 is usually below 400 0 C
  • the material temperature of the hot shaft part 203 is usually higher than 400 0 C and typically in the range of 400 0 C to 700 0 C.
  • the shaft 200 is therefore made from a nickel based superalloy which can sustain such high temperatures.
  • the superalloy comprises the following elements:
  • the nickel based superalloy can, in general, be any composition with elements in the above ranges, in the present embodiment the nickel based superalloy comprises :
  • At least the exit shaft part 201 and the compressor shaft part 203 which carries the last compressor disc 218 are made as a single seamless piece from the same nickel based superalloy.
  • the whole shaft 200 can be made as a single seamless piece from this alloy.
  • a test program testing the nickel based superalloy provided the result that the material is resistant to galling or rubbing wear on the lead-bronze material the bearing race is usually made from, and that the bearing journal is not subject to wire wooling damage. Rubbing tests were performed at various combinations of pressure loading and temperature, with and without lubrication, to represent all possible service conditions. The same tests were carried out with surface hardened low alloy steel (hardened low chromium steel EN25) currently used in the state of the art for forming the bearing journals, and comparison of the results showed that the above-specified nickel based superalloy had a better performance .
  • the specified nickel based superalloy is an austenitic alloy. Due to the high nickel content the austenitic material will be thermally stable, in particular with respect to carbide precipitation.
  • the chromium content provides for oxidation and corrosion resistance.
  • the alloy is precision hardenable for mechanical properties and hardness for journal race wear resistance.
  • the last compressor disc i.e. the disc carrying the last compressor blades towards the combustor section 106, may be made from the same material as the hot shaft part 203 and the exit shaft part 201 which provides the possibility of machining the last compressor disc and the exit shaft as one component. This has a cost saving effect.

Abstract

A turbine rotor (103) comprises a hot shaft part (203) being operable at a high temperature and a cool shaft part (201) being operable at a lower temperature than the high temperature, the cool shaft part (201) adjoining said hot shaft part (203) . The cool shaft part (201) and the hot shaft part (203) are composed from the same nickel based superalloy with a nickel content in the range of 30 - 65 wt%.

Description

Description
Turbine Rotor and Turbine Engine
The present invention relates to a turbine rotor, in particular a gas turbine rotor, which comprises a hot shaft part being operable at a high temperature and a cool shaft part being operable at a lower temperature than the high temperature. In addition, the invention relates to a turbine engine, in particular a gas turbine engine, comprising such a rotor .
Gas turbine engines, in particular axial gas turbine engines, comprise a compressor section, a combustor section and a turbine section which are arranged after each other in an axial direction and through which a turbine rotor extends in the axial direction. The turbine rotor may be supported on plain, hydrodynamic bearings. The bearing journal of such bearings is usually arranged in a part of the rotor which is not exposed to a high temperature. For example, in some engines the bearing journal is arranged in a so-called exit shaft part of the rotor which adjoins the compressor shaft part, which extends through the compressor section, towards the combustor section. The temperature of the rotor in the compressor section, in particular at the compressor exit, is rather high during operation of the gas turbine engine compared to the temperature of the exit shaft part due to the compression of air in the compressor section. In such gas turbine engines it is common practice to use a low alloy carbon steel for the bearing journal of the turbine rotor, and a high alloy steel or nickel based alloy for the rotor components that operate at high temperatures. A difficulty is that the different materials need to be joined together, which leads to difficulties in reliability and an increase of costs.
Sometimes high alloy steels are used for exit shafts, i.e. steels with a chrome fraction of about 10% by weight. However, steel containing more than 1% by weight chrome is prone to wire wooling, hence the journal surface is always protected by chrome plating, by cladding with low alloy steal (less than 1% chrome), or by using a low alloy steel sleeve. Nickel alloy journals with low alloy steel sleeves are also known to be used.
Chrome plating is process sensitive, can have adhesion problems and is known to have caused bearing failures in the past. Cladding by welding process would overcome those issues, however the welding process is expensive. Added sleeves, on the other hand, can only be used where the journal diameter is not smaller than the end of the shaft. If an overhung construction where the bearing is located between the turbine discs and compressor rotor is used, the joint at the turbine discs is usually of a larger diameter than the bearing journal, so that the sleeve cannot be used.
It is therefore an objective of the present invention to provide a turbine rotor which overcomes the mentioned difficulties. It is a further objective of the present invention to provide a turbine engine, in particular a gas turbine engine, which comprises an improved turbine rotor.
The first objective is solved by a turbine rotor according to claim 1, the second objective by a turbine engine, in particular a gas turbine engine, according to claim 8. The depending claims define advantageous developments of the invention .
An inventive turbine rotor comprises a hot shaft part, in particular a hot end shaft part, being operable at a high temperature and a cool shaft part, e.g. an exit shaft part as described in the introduction, being operable at a lower temperature than the high temperature. The cool shaft part adjoins the hot shaft part. High and low temperatures refers temperatures above and below 4000C, respectively. In the inventive turbine rotor, both the cool shaft part and the hot shaft part are in metallic continuity and are composed from the same nickel based superalloy, in particular an austenitic superalloy, with nickel content in the range of 30 to 65 wt%.
The use of a nickel based superalloy with nickel content in the range of 30 to 65 wt% allows the turbine rotor to be formed from a single piece of metal in the hot shaft part and the cool shaft part. The mentioned nickel based superalloy has been found to be suitable for forming the hot shaft part as well as the cool shaft part. It shows a high hot strength, is resistant to galling or rubbing wear on the bearing material, which is usually lead-bronze, and is not subject to wire wooling damage. Moreover, the mentioned nickel based superalloy has been shown to be able to withstand high compressive stress from running on rollers during balancing. In addition, it is suitable for use with inductive vibration monitoring probes. Finally, the mentioned nickel based superalloy has a minimum hardness ratio relative to the bearing material and a suitable thermal expansion coefficient to maintain the required bearing clearances .
The inventive turbine rotor provides the following advantages: as the material is not prone to wooling damage, the use of a sleeve around the bearing journal, chrome plating on the bearing journal or cladding of the bearing journal is not necessary. Moreover, as the hot shaft part and the cool shaft part are composed of the same material it is possible to form both parts as one single seamless piece. Bolting the hot shaft part to the cool shaft part, which is the current state of the art, is less stable than a single seamless piece. Welding the hot shaft part to the cool shaft part is also known in the state of the art to be a viable solution. However this solution is expensive and may have difficulties regarding to life time of the welded joint.
Making the hot shaft part and the cool shaft part from one single seamless piece therefore reduces the production costs and improves the strength of the rotor compared to the state of the art .
The nickel based superalloy of which the hot shaft part and the cool shaft part are composed may comprise a chromium content above 10 wt%, in particular above 16%, for oxidation and/or corrosion resistance. Whereas steel with more than 3% chromium and in particular stainless steel with 12% chromium is usually subject to wire wooling, nickel based superalloys with a nickel content in the range of 30 to 65 wt% comprising a chromium content of at least 10 wt% are not prone to wire wooling. A high chromium content, however, is desired for the bearing journal. If a steel shaft with 19% chromium were to be used one would expect to get wire wooling problems.
Suitable nickel based superalloys comprise:
0 - 0.08 wt-% carbon
0 - 0.35 wt-% manganese 0 - 0.015 wt-% phosphorus
0 - 0.015 wt-% sulphur
0 - 0.35 wt-% silicon
10 -21 wt-% chromium
30 - 65 wt-% nickel 2.80 - 3.30 wt-% molybdenum
4.75 - 5.50 wt-% niobium
0.65 - 1.15 wt-% titanium
0.20 - 0.80 wt-% aluminium
0 - 1.00 wt-% cobalt 0 - 0.006 wt-% boron
0 - 0.30 wt-% copper
0 - 0.05 wt-% tantalum balance iron, and are known as inconel 718.
The inventive turbine rotor may be provided with a bearing part being designed for reception into a bearing, e.g. with a bearing journal in the cool shaft part. The cool shaft part may represent an exit shaft part and the hot shaft part a compressor shaft part which is designed to be arranged in a compressor section of a gas turbine engine. The bearing journal is then arranged in the exit shaft part which adjoins the compressor shaft part. The hot shaft part may comprise at least one rotor disc, e.g. a compressor disc in the case of the hot shaft part being at least a part of the compressor shaft part .
An inventive turbine engine, which may in particular be a gas turbine engine, comprises an inventive turbine rotor. In particular, the rotor may extend at least partly through a compressor section and at least partly through a combustor section of the gas turbine engine, where the hot shaft part of the rotor is located in the compressor section and the cool shaft part is located in the combustor section. The advantages of the inventive turbine rotor can be used to increase the reliability of the turbine engine or to reduce the manufacturing costs.
Additional features, properties and advantages of the present invention will become clear from the following description of an embodiment by reference to the accompanying drawings.
Figure 1 shows a gas turbine engine in a sectional view.
Figure 2 shows a part of the rotor of the turbine engine shown in Figure 1 in detail.
Figure 1 shows an example of a gas turbine engine 100 in a sectional view. The gas turbine engine 100 comprises a compressor section 105, a combustor section 106 and a turbine section 112 which are arranged adjacent to each other in a longitudinal direction of a rotation axis 102. It further comprises a rotor 103 which is rotatable about the rotational axis 102 and which extends longitudinally through the gas turbine engine 100. In operation of the gas turbine engine 100 air 135, which is taken in through an air inlet 104 of the compressor section 105, is compressed by the compressor section and output to the burner section 106. During compression, the temperature of the air raises to about 4000C to 7000C at the compressor exit 108.
The burner section 106 comprises one or more combustion chambers 110 and at least one burner 107 fixed to each combustion chamber 110. The compressed air from the compressor exit 108 enters the burner 107 where it is mixed with a fuel, for example gas or oil. The air fuel mixture is then burnt and the exhaust gas 113 from the combustion is led through the combustion chamber 110 to the turbine section 112. A number of blade carrying discs 120 are fixed to the rotor 103 in the turbine section 112 of the engine. In the present example, two discs carrying turbine blades 121 are present. In addition guide vanes 130, which are fixed to a stator 143 of the gas turbine engine 100, are disposed between the turbine blades 121. Between the exit of the combustion chamber 110 and the leading turbine blades 121 inlet guide vanes 140 are present. The exhaust gas from the combustion chamber 110 enters the turbine section 112 and transfers momentum to the turbine blades 121 which results in a rotation of the rotor 103. The guide vanes 130, 140 serve to optimise the impact of the exhaust gas on the turbine blades 121.
The turbine rotor 103 is shown in Figure 2 in greater detail. The figure shows a section of the rotor 103. The shown section of the rotor 103 comprises a shaft 200 which comprises a cool shaft part 201 and a hot shaft part 203. The hot shaft part 203 is formed from at least a part of the shafts compressor section, i.e. at least from that part of the shaft 200 which extends through the compressor and carries the last compressor disc 218 (compressor disc located at the compressor exit) . The cool shaft part 201 is, in the present embodiment, an exit shaft part which adjoins the hot shaft part 203 in the combustor section 106.
The shaft 200 is supported by a bearing 205 in the exit shaft part 201. The bearing 205, which is implemented as a hydrodynamic bearing, comprises a bearing race 207 and bearing journal 209 which is formed at the bottom of a recess 211 running around the circumference of the shaft 200. A bearing clearance 213 is present between the bearing race 207 and the bearing journal 209. It is filled with a liquid or a gas supporting the load.
While in operation the material temperature of the cool shaft part 201 is usually below 4000C the material temperature of the hot shaft part 203 is usually higher than 4000C and typically in the range of 4000C to 7000C. The shaft 200 is therefore made from a nickel based superalloy which can sustain such high temperatures. The superalloy comprises the following elements:
0 - 0.08 wt-% carbon
0 - 0.35 wt-% manganese
0 - 0.015 wt-% phosphorus
0 - 0.015 wt-% sulphur 0 - 0.35 wt-% silicon
10 -21 wt-% chromium
30 - 65 wt-% nickel
2.80 - 3.30 wt-% molybdenum
4.75 - 5.50 wt-% niobium 0.65 - 1.15 wt-% titanium
0.20 - 0.80 wt-% aluminium
0 - 1.00 wt-% cobalt
0 - 0.006 wt-% boron
0 - 0.30 wt-% copper 0 - 0.05 wt-% tantalum balance iron. While the composition of the nickel based superalloy can, in general, be any composition with elements in the above ranges, in the present embodiment the nickel based superalloy comprises :
53 wt-% nickel, 19 wt-% chromium, 18 wt-% iron,
5,125 wt-% niobium and/or tantalum, 3, 05 wt-% molybdenum, 0, 95 wt-% titanium, 0,5 wt-% aluminium, and 0,05 wt-% carbon.
At least the exit shaft part 201 and the compressor shaft part 203 which carries the last compressor disc 218 are made as a single seamless piece from the same nickel based superalloy. In general, the whole shaft 200 can be made as a single seamless piece from this alloy.
While the above-specified nickel based superalloy is suitable for use with vibration monitoring probes, able to withstand high compressive stress from running on rollers during balancing, has a minimum hardness ratio relative to the bearing material and has a suitable thermal expansion coefficient to maintain the required bearing clearances, tests have been performed to show that this alloy is also resistant to galling or rubbing wear and to wire wooling damage. All the literature known by the inventors when the invention was made refers to wire wooling in Fe based materials, with -2% - 30% Cr content. There was no reference to wire wooling in nickel alloys, with any Cr-level, but also nothing to support the view that wire wooling does not occur on Ni-based alloys. Therefore, tests were to give at least a first assurance that wire wooling would not be a problem.
A test program testing the nickel based superalloy provided the result that the material is resistant to galling or rubbing wear on the lead-bronze material the bearing race is usually made from, and that the bearing journal is not subject to wire wooling damage. Rubbing tests were performed at various combinations of pressure loading and temperature, with and without lubrication, to represent all possible service conditions. The same tests were carried out with surface hardened low alloy steel (hardened low chromium steel EN25) currently used in the state of the art for forming the bearing journals, and comparison of the results showed that the above-specified nickel based superalloy had a better performance .
In addition, the above-specified nickel based superalloy was successfully tested on a compressor rig and on a production specification engine. The existing two-piece construction of a compressor intermediate shaft and turbine shaft used in the state of the art was replaced by a single component.
The specified nickel based superalloy is an austenitic alloy. Due to the high nickel content the austenitic material will be thermally stable, in particular with respect to carbide precipitation. The chromium content provides for oxidation and corrosion resistance. The alloy is precision hardenable for mechanical properties and hardness for journal race wear resistance.
It shall also be mentioned that the last compressor disc, i.e. the disc carrying the last compressor blades towards the combustor section 106, may be made from the same material as the hot shaft part 203 and the exit shaft part 201 which provides the possibility of machining the last compressor disc and the exit shaft as one component. This has a cost saving effect.

Claims

Claims
1. A turbine rotor (103) comprising a hot shaft part (203) being operable at a high temperature and a cool shaft part (201) being operable at a lower temperature than the high temperature, the cool shaft part (201) adjoining said hot shaft part (203) , wherein the cool shaft part (201) and the hot shaft part (203) are composed from the same nickel based superalloy with a nickel content in the range of 30 - 65 wt%.
2. A turbine rotor (103), according to claim 1, in which the nickel based superalloy is an austenitic superalloy.
3. A turbine rotor (103), according to claim 1 or 2, in which the nickel based superalloy comprises a chromium content of at least 10 wt-%.
4. A turbine rotor (103), according to claim 3, in which the nickel based superalloy comprises:
0 - 0.08 wt-% carbon
0 - 0.35 wt-% manganese
0 - 0.015 wt-% phosphorus
0 - 0.015 wt-% sulphur 0 - 0.35 wt-% silicon
10 -21 wt-% chromium
30 - 65 wt-% nickel
2.80 -
3.30 wt-% molybdenum
4.75 - 5.50 wt-% niobium 0.65 - 1.15 wt-% titanium
0.20 - 0.80 wt-% aluminium
0 - 1.00 wt-% cobalt
0 - 0.006 wt-% boron
0 - 0.30 wt-% copper 0 - 0.05 wt-% tantalum balance iron.
5. A turbine rotor (103), according to one of the preceding claims, in which the hot shaft part (203) and the cool shaft part (201) are made as one single seamless piece.
6. A turbine rotor (103), according to one of the preceding claims, in which the cool shaft part (201) comprises a bearing part being designed for reception into a bearing.
7. A turbine rotor according to one of the preceding claims, in which the hot shaft part (203) comprises at least one disc
(218) .
8. A turbine engine (100) comprising a turbine rotor (103), according to one of the preceding claims.
PCT/EP2006/061626 2005-04-19 2006-04-18 Turbine rotor and turbine engine WO2006111520A1 (en)

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EP05008528.1 2005-04-19
EP05008528 2005-04-19

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WO2015197751A1 (en) * 2014-06-27 2015-12-30 Nuovo Pignone Srl Component of a turbomachine, turbomachine and process for making the same
CN106676429A (en) * 2015-11-11 2017-05-17 三菱日立电力系统株式会社 Austenite steel, and austenite steel casting using same

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