ROTOR
A rotor for a gas-turbine engine, is provided having a first and a second rotor disc that are suitable to be joined directly. The first and second rotor discs are symmetric with respect to an axis of rotation common to the two rotor discs. The first rotor disc provides an interrupted screw on one side. The second rotor disc provides an interrupted screw on another side. The interrupted screw of the second rotor disc reciprocates the interrupted screw of the first rotor disc.
This application claims priority to European application 13162666.5 filed Apr. 8, 2013, the contents of which are hereby incorporated in its entirety.
TECHNICAL FIELDThe present invention relates to a rotor, for example for a gas-turbine engine. More particularly, the present invention also relates to mechanical coupling between the rotor discs of the rotor.
BACKGROUNDState-of-the-art gas-turbines engines typically comprise three sections: A compressor, a combustor, and a turbine. Before entering the combustor, pressure of the working medium, typically air, is increased to approximately by the compression section. The compressed air then leaves the compression section and enters the combustor, where it is mixed with fuel and the combustion process takes place. After combustion, hot air leaves the combustor and is fed into the turbine.
A gas-turbine engine comprises a rotor. The rotor can be assembled from discs in a stack-up operation where components such as the compressor discs and the turbine discs are connected coaxially together along the axis of rotation. Various ways of connecting the discs of a rotor have been put forward. U.S. Pat. No. 3,976,399 discloses rotor discs stacked on a central connecting rod. The rotor discs of U.S. Pat. No. 3,976,399 are held in place by half-shells which are clamped together by clamping rings. U.S. Pat. No. 3,976,399 also discloses heat-shrinking rotors discs onto a central connecting rod. U.S. Pat. No. 7,384,075 discloses threaded joints between the components of a rotor. The threaded joint is additionally secured by an anti-rotation locking mechanism. U.S. Pat. No. 5,537,814 and U.S. Pat. No. 8,100,666 disclose a clamping nut and a tie shaft to axially clamp a turbine disc together with other rotor components. U.S. Pat. No. 4,310,286 discloses bolted joints to fixate the discs of a rotor.
The mechanical connections between the rotor discs of a gas-turbine engine have to meet a number of conflicting technical requirements: The rotor of a gas-turbine engine may deflect, so the axis of rotation and the center of mass of the rotor will no longer coincide. The connections between the rotors discs of a gas-turbine engine shall thus be torsionally stiff. The connections between the rotor discs of a gas-turbine engine shall be designed for a critical speed of the rotor well above the operational speed of 1500 or 15000 rpm.
The pressures inside the gas-turbine engine may be severe. The rotor of a gas-turbine engine shall be designed to withstand the corresponding stresses.
The new stack of rotor discs shall minimize the effort involved in its fabrication. In particular, the fabrication of the stack of rotor discs shall minimize the use of special tools.
Despite the aforementioned requirement of torsional stiffness, the joints between rotor discs shall allow easy and effortless removal and replacement of discs when the rotor is in stationary position. In other words, any rotor discs shall be easily displaceable during maintenance or repair.
The present application is oriented towards providing the aforementioned needs and towards overcoming the aforementioned difficulties.
SUMMARYThe present disclosure is about improved mechanical connections between the discs of a rotor. In order to arrive at a connection that is torsionally stiff and leakage-proof, an interrupted screw on each side of a reciprocally connected rotor disc is proposed. An interrupted screw is a screw whose surface is divided longitudinally into several blank or cutaway sections. The two rotor discs are locked together by a fraction of a turn.
After connecting the two rotor discs, the surfaces of the interrupted screw of the first rotor disc and of the reciprocally made nut of the second rotor disc align. The alignment of the two surfaces results in a connection that is torsionally stiff and allows for a critical speed of the rotor well above 1500 to 15000 rpm.
The interrupted screw on each side of the reciprocally connected rotor discs can be made of the same metals. That way, corrosion issues due to the use of dissimilar metals are eliminated.
The rotor discs can also be made of different metals, in particular of different steel alloys. A gas-turbine engine may require different alloys to be used for the rotor discs of the compressor and for the rotor discs of the combustor. The present disclosure allows rotor discs made of different metals or alloys to be connected.
To assemble a rotor, the two or more rotor discs are engaged and one rotor disc is rotated by a fraction of a turn against the other rotor disc. The rotation is carried out about the axis of rotation common to the two rotor discs. That axis will later become the axis of rotation of the rotor. As soon as the two discs are connected, yet another rotor disc is connected the stack of previously joined rotor discs by engaging said disc and the stack of rotor discs. The process continues until the assembly of the rotor is complete.
Likewise, during repair or maintenance of a rotor, a disc is removed from the stack of rotor discs by rotating it by a fraction of a turn. The direction of the rotation is now opposite to the direction when two discs were connected. The disc can then be removed from the remaining stack rotor discs. The process may continue until the stack of rotor discs has been completely disassembled.
The foregoing objects and many of the attendant advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description when taken in conjunction with the accompanying drawings, wherein:
On the other side 4 of the rotor disc 1, segments 9a, 9b, 9c have been arranged. Each segment on one side 4 of the rotor disc 1 reciprocates with a slot on the other side 5 of the disc 1. In a preferred embodiment, the segments 9a, 9b, 9c are arranged evenly like the slots 6a, 6b, 6c, 6d on the other side 5 of the rotor disc 1.
The segments 9a, 9b, 9c and the slots 6a, 6b, 6c, 6d are arranged so they act like plugs and sockets. In a preferred embodiment, the segments 9a, 9b, 9c can slide into the clamping surfaces 7 provided by each slot 6a, 6b, 6c, 6d. In this embodiment, the clamping surfaces 7 of the slots 6a, 6b, 6c, 6d narrow towards one of their ends. The segments 9a, 9b, 9c narrow in the same way. The segments 9a, 9b, 9c can thus slide into the clamping surfaces 7 until the surfaces of the segments 9a, 9b, 9c and the surfaces of the clamping surfaces 7 engage. A rigid connection between two adjacent discs is formed as the segments 9a, 9b, 9c eventually get wedged inside the slots 6a, 6b, 6c, 6d.
In another embodiment, the disc 1 with the slots 6a, 6b, 6c, 6d is heated before the segments 9a, 9b, 9c can slide into the slots 6a, 6b, 6c, 6d. By heating the disc 1 with the slots 6a, 6b, 6c, 6d, the material expands, so the inner diameter of each clamping surface 7 increases. The segments 9a, 9b, 9c may then slide into the slots 6a, 6b, 6c, 6d. The temperatures of the slots 6a, 6b, 6c, 6d lower after introducing the segments 9a, 9b, 9c and a rigid connection providing a rotor with torsional stiffness will be formed. The segments 9a, 9b, 9c will then also exert an inward force on the clamping surfaces 7 of the slots 6a, 6b, 6c, 6d. The inward force counter-acts the centrifugal force when the rotor disc 1 rotates as part of a rotor. In other words, heat treatment will not only result in torsional stiffness but also in compensation of centrifugal forces when the rotor is in service.
It should be mentioned the clamping surfaces 7 of the slots 6a, 6b, 6c, 6d as shown on
The clamping surfaces 7 of the slots 6a, 6b, 6c, 6d, 6e, 6f and the surface of the segments 9a, 9b, 9c, 9d, 9e, 9f get wedged when the discs 1a, 1b are connected. In a preferred embodiment, wedged joint between the discs 1a, 1b then essentially becomes leakage-proof.
To disconnect the two discs 1a, 1b, the process as described above is reversed. Heat treatment can be used as well. The disc 1a with the slots 6a, 6b, 6c, 6d, 6e, 6f will have to be heated at a faster rate than the other disc 1b. The two discs 1a, 1b are disconnected as soon as the heat treatment yields a gap between the surfaces of the slots 6a, 6b, 6c, 6d, 6e, 6f and the surfaces of the segments 9a, 9b, 9c, 9d, 9e, 9f. Induction heating may be used for the purpose of heating disc 1a faster than the other disc 1b. The rotor discs 1a, 1b allow for easy dismantling of a rotor, since disconnection of the rotor discs 1a, 1b only requires a reversal of the above process.
While
The rotor discs 1a, 1b, 1c, 1d, 1e shown on
In order to connect the rotor discs shown on
The process of connecting rotor discs continued rotor discs may be continued until a stack of rotor discs is formed.
The disclosure describes a rotor made of rotor discs with interrupted screws in relation to a gas-turbine engine. In another embodiment, the same rotor and the same rotor discs form part of the rotor of a turbogenerator. Other applications such as hydro generators are also envisaged.
Although the present invention has been fully described in connection with preferred embodiments, it is evident that modifications may be introduced within the scope thereof, not considering the application to be limited by these embodiments, but by the contents of the following claims.
Claims
1. A rotor comprising:
- a first rotor disc;
- a second rotor disc;
- wherein the first rotor disc provides a first interrupted screw on at least one side, the second rotor disc provides a second interrupted screw on at least one side, the second interrupted screw of the second rotor disc being connected to the first interrupted screw of the first rotor disc.
2. The rotor according to claim 1, wherein the first and second rotor discs are substantially symmetric with respect to the axis of rotation of the rotor.
3. The rotor according to claim 1, wherein the first and second rotor discs are suitable to be connected directly to one another.
4. The rotor according to claim 1, wherein at least one of the first and second rotor discs provides two interrupted screws on both of its sides.
5. The rotor according to claim 1, wherein the first rotor disc provides a first interrupted screw with a protruding rim with a sidewall, a first set of wedges being arranged along the sidewall of the protruding rim; and
- the second rotor disc provides a second interrupted screw comprising a groove with a sidewall, a second set of wedges being arranged along the sidewall of the groove.
6. The rotor according to claim 5, wherein the first set of wedges is evenly arranged along the sidewall of the protruding rim and the second set of wedges is evenly arranged along the sidewall of the groove.
7. The rotor according to claim 5, wherein the first set of wedges comprises eight wedges and the second set of wedges comprises eight wedges.
8. The rotor according to claim 1, wherein the first rotor disc provides an interrupted screw comprising a plurality of slots, and wherein the second rotor disc provides an interrupted screw comprising a plurality of segments.
9. The rotor according to claim 8, wherein each slot comprises a clamping surface.
10. The rotor according to claim 8, wherein the slots of the first rotor disc are evenly arranged along the inner perimeter of the first rotor disc and the segments of the second rotor disc are evenly arranged along the inner perimeter of the second rotor disc.
11. The rotor according to claim 8, wherein the first rotor disc provides six slots and the second rotor disc provides six segments.
12. A gas-turbine engine with a rotor according to claim 1.
13. A turbogenerator with a rotor according to claim 1.
14. A method for directly joining a first rotor disc and a second rotor disc, the first rotor disc providing an interrupted screw on at least one side, and the second rotor disc provides an interrupted screw on at least one side, the interrupted screw of the second rotor disc reciprocating the interrupted screw of the first rotor disc;
- the method comprising:
- connecting the first rotor disc with the second rotor disc by engaging the first interrupted screw of the first rotor disc with the second interrupted screw of the second rotor disc, and rotating the first rotor disc against the second rotor disc by a fraction of a turn.
15. A method according to claim 11, wherein the size of the interrupted screw of one rotor disc is increased by heating before engaging the interrupted screws of the two rotor discs.
Type: Application
Filed: Apr 4, 2014
Publication Date: Oct 9, 2014
Inventor: Hossein SAFARI ZADEH (Othmarsingen)
Application Number: 14/245,320
International Classification: F01D 5/06 (20060101);