WO2025098802A1

WO2025098802A1 - Damping assembly for damping torsional vibrations of a shaft, turbomachine including the same, and method of damping torsional vibrations of a shaft

Info

Publication number: WO2025098802A1
Application number: PCT/EP2024/080273
Authority: WO
Inventors: Moritz MOSDZIEN; Martin Seiler
Original assignee: Accelleron Switzerland Ltd
Current assignee: Accelleron Switzerland Ltd
Priority date: 2023-11-07
Filing date: 2024-10-25
Publication date: 2025-05-15
Anticipated expiration: 2026-05-07

Abstract

A damping assembly (10) for damping torsional vibrations of a shaft (11), particularly a main shaft of a turbomachine (20), is described. The damping assembly (10) includes a one-piece shaft sleeve (12) provided around the shaft (11). The one-piece shaft sleeve (12) has an aspect ratio L/D_out ≥ 2, wherein L is an axial length of the one-piece shaft sleeve (12) and D_out is an outer diameter of the one-piece shaft sleeve (12). Further, the damping assembly (10) includes an axial clamping (14) of the one-piece shaft sleeve (12), a first perimetric press fit (131) between a first end portion (121) of the one-piece shaft sleeve (12) and the shaft (11), and a second perimetric press fit (132) between a second end portion (122) of the one-piece shaft sleeve (12) and the shaft (11). Between the first perimetric press fit (131) and the second perimetric press fit (132) a radial gap (13) between the one-piece shaft sleeve (12) and the shaft (11) is provided.

Description

DAMPING ASSEMBLY FOR DAMPING TORSIONAL

VIBRATIONS OF A SHAFT, TURBOMACHINE INCLUDING THE SAME, AND METHOD OF DAMPING TORSIONAL VIBRATIONS

OF A SHAFT

TECHNICAL FIELD

[0001] Embodiments of the present disclosure relate to damping assemblies and methods for damping torsional vibrations of a shaft, particularly a main shaft of a turbomachine. Further embodiments of the present disclosure relate turbomachines including a damping assembly according to embodiments described herein.

BACKGROUND

[0002] Turbochargers are used to increase the power of reciprocating engines. They have a high-speed rotor unit comprising a turbine, a compressor and a shaft connecting the turbine and compressor. In exhaust gas turbochargers, the turbine of the turbocharger is driven by the exhaust gas of an internal combustion engine. The turbine drives the compressor by means of the common shaft. The gas compressed by the compressor is fed to the combustion chambers to supercharge the engine. The pressure of the exhaust gas from the internal combustion engine driving the turbine is not constant, so the turbocharger shaft can be excited to vibrate. The pressure pulsations depend, among other things, on the characteristics of the opening and closing of the engine's exhaust valves and on the exhaust line design. The frequency spectrum of these pressure pulsations is clearly dominated by the engine ignition frequency, which depends on the number of cylinders, the working method (2-stroke/4-stroke) and the engine speed. When designing mechanical systems or structures, the interaction between torsional excitation and resonance eigenfrequencies should be carefully considered and managed to ensure the safety, reliability, and longevity of the system. Special attention to material properties, geometry, damping, and monitoring can help mitigate the risks associated with torsional vibrations near resonance frequencies.

[0003] Turbochargers on modern 4-stroke engines often use pulse charging to achieve good part-load and response behavior. With these shock charging systems, strong and high-frequency pressure fluctuations occur in the exhaust lines. Depending on the engine load or engine speed, this excites the torsional natural frequency of the rotor. Since turbocharger rotors are normally very stiff and have low torsional damping, inadmissibly high torque amplitudes can occur in the resonance, which place excessive stress on the joints of the turbocharger shaft and in extreme cases lead to torsional fracture of the shaft.

[0004] Furthermore, investigations and measurements have shown that, in addition to the frequency of engine order, higher harmonics of the engine frequencies also occur in the pressure pulsation spectrum. These higher-order pressure pulsations can also coincide with the torsional natural frequency of the turbocharger shaft. These resonant oscillations, which cannot be avoided at variable engine speeds, also lead to torsional stresses in the turbocharger shaft. Steeper camshaft flanks and increasing pressure ratios in engines and turbochargers are likely to result in stronger excitations and therefore greater torsional stresses in the turbocharger shaft. The required increasing power density of the turbocharger shaft can aggravate the problem.

[0005] A well-known measure to reduce loads due to torsional vibrations in turbomachinery is to select larger shaft diameters to stiffen the shaft. This increases torsional natural frequencies and reduces vibration amplitudes. However, the vibration behavior is still undamped and the power losses in the turbocharger shaft bearings are increased. [0006] Known torsional vibration dampers for relatively slowly rotating crankshafts are, for example, oil displacement dampers, rubber dampers, viscous torsional vibration dampers or silicone oil rubber dampers. Such dampers typically feature a flywheel mass that is mechanically coupled to the crankshaft via a damping mechanism. Flywheel mass dampers are mounted at the end of the crankshaft, since this is where the largest torsional vibration amplitudes occur.

[0007] Accordingly, in view of the above, there is a demand for improved damping assemblies and methods for damping torsional vibrations of a shaft, particularly a main shaft of a turbomachine, which at least partially overcome some of the problems of the state of the art.

SUMMARY

[0008] In light of the above, a damping assembly for damping torsional vibrations of a shaft and a method of damping torsional vibrations of a shaft according to the independent claims are provided. Further aspects, advantages, and features are apparent from the dependent claims, the description, and the accompanying drawings.

[0009] According to an aspect of the present disclosure, a damping assembly for damping torsional vibrations of a shaft, particularly a main shaft of a turbomachine, is provided. The damping assembly includes a one-piece shaft sleeve provided around the shaft. The one-piece shaft sleeve has an aspect ratio L/D_out > 2, wherein L is an axial length of the one-piece shaft sleeve and D_out is an outer diameter of the one-piece shaft sleeve. Further, the damping assembly includes an axial clamping of the one-piece shaft sleeve, a first perimetric press fit between a first end portion of the shaft one-piece sleeve and the shaft, and a second perimetric press fit between a second end portion of the one-piece shaft sleeve and the shaft. Between the first perimetric press fit and the second perimetric press fit a radial gap between the one-piece shaft sleeve and the shaft is provided.

[0010] Accordingly, compared to conventional damping assemblies used for damping torsional vibrations of a shaft, the damping assembly of the present disclosure is improved, particularly with respect to simplicity, cost efficiency, damping quality and operational behavior. In particular, embodiments of the damping assembly as described herein beneficially enhance the reliability, performance, and lifespan of the machinery in which the damping assembly is employed by reducing the negative effects of torsional vibrations, such as fatigue, wear, and potential structural damage.

[0011] According to a further aspect of the present disclosure, a turbomachine including a damping assembly for damping torsional vibrations of a shaft according to any embodiments describe herein is provided. In particular, the turbomachine can be a turbocharger. For instance, the shaft may connect a compressor wheel of a compressor with a turbine wheel of a turbine.

[0012] According to another aspect of the present disclosure, a method of damping torsional vibrations of a shaft, particularly a main shaft of a turbomachine, is provided. The method includes damping torsional vibrations by friction, particularly micro friction, between a one-piece shaft sleeve provided around the shaft. The one-piece shaft sleeve has an aspect ratio L/Dout > 2, wherein L is an axial length of the one-piece shaft sleeve and D_out is an outer diameter of the one-piece shaft sleeve. The friction is provided at interfaces of an axial clamping of the one-piece shaft sleeve, at a first perimetric press fit interface between a first end portion of the one-piece shaft sleeve and the shaft, and at a second perimetric press fit interface between a second end portion of the one-piece shaft sleeve and the shaft. Between the first perimetric press fit and the second perimetric press fit a radial gap between the one-piece shaft sleeve and the shaft is provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments. The accompanying drawings relate to embodiments of the disclosure and are described in the following:

Fig. 1 to 4 show a schematic views of a damping assembly for damping torsional vibrations of a shaft according to exemplary embodiments described herein; and

Fig. 5 shows a flowchart for illustrating a method of damping torsional vibrations of a shaft according to embodiments described herein.

DETAILED DESCRIPTION OF EMBODIMENTS

[0014] Reference will now be made in detail to the various embodiments, one or more examples of which are illustrated in each figure. Each example is provided by way of explanation and is not meant as a limitation. For example, features illustrated or described as part of one embodiment can be used on or in conjunction with any other embodiment to yield yet a further embodiment. It is intended that the present disclosure includes such modifications and variations.

[0015] Within the following description of the drawings, the same reference numbers refer to the same or to similar components. Generally, only the differences with respect to the individual embodiments are described. Unless specified otherwise, the description of a part or aspect in one embodiment can apply to a corresponding part or aspect in another embodiment as well. [0016] With exemplary reference to Figs. 1 to 4, a damping assembly 10 for damping torsional vibrations of a shaft 11 according to embodiments of the present disclosure are described.

[0017] According to embodiments, which can be combined with other embodiments described herein, the damping assembly 10 includes a shaft one-piece sleeve 12 provided around the shaft 11. The one-piece shaft sleeve 12 has an aspect ratio L/D_out > 2, wherein L is an axial length of the one-piece shaft sleeve 12 and D_out is an outer diameter of the one-piece shaft sleeve 12. The "axial length L" of the one-piece shaft sleeve refers to the distance measured along the axis of the sleeve, which typically corresponds to the length of the sleeve in the direction parallel to the shaft it encases. In other words, it is the linear measurement of the shaft sleeve from one end to the other end along its central axis. The "outer diameter" of the one-piece shaft sleeve refers to the measurement of the total distance across the shaft sleeve, measured from one outer edge to the opposite outer edge, passing through the central axis of the shaft sleeve.

[0018] According to embodiments, which can be combined with other embodiments described herein, aspect ratio L/D_out can be L/D_out > 3, particularly L/D_out > 4, more particularly L/D_out > 5. As shown in Figs. 1 to 3, the outer diameter D_out is typically constant, at least at the first end portion 121 and/or the second end portion 122 of the shaft sleeve 12. Figure 1 shows an example in which the outer diameter D_outis constant over the full length L of the shaft sleeve. Figure 2 shows an example in which the outer diameter D_out is constant from the first axial pressing 141 up to the enlarged diameter shaft sleeve portion 125, particularly up to the first end shoulder 127. Further, figure 2 shows that the outer diameter D_out can be constant from the second axial pressing 141 up to the enlarged diameter shaft sleeve portion 125, particularly up to the second end shoulder 128. [0019] Further, the damping assembly 10 includes an axial clamping 14 of the one-piece shaft sleeve 12, a first perimetric press fit 131 between a first end portion 121 of the one-piece shaft sleeve 12 and the shaft 11, and a second perimetric press fit 132 between a second end portion 122 of the shaft sleeve 12 and the shaft 11. Between the first perimetric press fit 131 and the second perimetric press fit 132 a radial gap 13 between the one-piece shaft sleeve 12 and the shaft 11 is provided.

[0020] Accordingly, the damping assembly according to embodiments of the present disclosure is improved compared to conventional damping approaches for damping torsional vibrations of a shaft. In particular, embodiments of the damping assembly as described herein beneficially provide a simple and cost-effective damping assembly with high torsional damping capability against excitation of the shaft, for example induced by an electric machine and/or at the shaft end, i.e. at a rotor position, e.g. a compressor or turbine position, as described further down below. Accordingly, embodiments described herein beneficially provide for a smooth operational behavior minimizing the risk for a rotor breakdown.

[0021] In the present disclosure, a “damping assembly for damping torsional vibrations of a shaft” can be understood as a mechanical system configured to reduce or control unwanted oscillations and vibrations that occur along the length of a rotating shaft, particularly detrimental oscillations and vibrations that involve twisting or torsional motion. Torsional vibrations can be understood as oscillations or vibrations that occur when a shaft rotates. Torsional vibrations typically involve a twisting or torsion motion along the length of the shaft. Such vibrations can be harmful may lead to mechanical failures, reduced performance, and noise.

[0022] In the present disclosure, an “shaft sleeve” can be understood as cylindrical or tubular element configured to fit around a shaft. A one-piece shaft sleeve refers to a single, continuous shaft sleeve. In other words, the term "one-piece" emphasizes that the shaft sleeve is constructed as a single, integral unit, without seams or joints. It is to be understood that the term “shaft sleeve” as used in the present disclosure refers to a one-piece shaft sleeve.

[0023] In the present disclosure, an “axial clamping of the shaft sleeve” can be understood as a mechanism that involves applying clamping force or pressure along the length of the shaft sleeve in an axial direction. In particular, it is to be understood that the axial clamping secures or affixes the shaft sleeve in place along the axis of the shaft. Further, it is to be understood that the axial clamping typically has clamping interfaces on each axial end of the shaft sleeve.

[0024] In the present disclosure, an “perimetric press fit” can be understood as a specific type of mechanical fastening or assembly method used to join two components, typically cylindrical or tubular in shape. In a perimetric press fit, one component is inserted into the other, and the fit is achieved primarily by applying pressure around the perimeter or circumference of the components rather than along their axial length. In other words, a “perimetric press fit” can be understood as a connection of two parts, particularly with a cylindrical or tubular shape, where one part is inserted into the other with a snug and secure fit. This connection relies on the interference between the outer perimeter or circumference of the inserted component and the inner perimeter or circumference of the receiving component. In a perimetric press fit, an interference fit is intentionally created, where the dimensions of the inner and outer diameters of the components are such that they do not fit together with ease. This interference provides the necessary friction between the components.

[0025] In the present disclosure, an “radial gap between the shaft sleeve and the shaft” can be understood as a space or clearance between the inner surface of the shaft sleeve and the outer surface of the shaft, where the shaft sleeve is not in direct contact with the shaft. The term "radial" pertains to a direction extending from the central axis of the shaft outwards in the radial direction. The central axis 110 of the shaft, the radial direction r, and the axial direction x are indicated in Figs. 1 to 4.

[0026] According to embodiments, which can be combined with other embodiments described herein, the axial clamping 14 is provided by a first axial pressing 141 at a first axial end 123 of the shaft sleeve 12 and a second axial pressing 142 at a second axial end 124 of the shaft sleeve 12. In other words, the axial clamping 14 is provided by an axial pressing provided at both ends of the shaft sleeve.

[0027] According to embodiments, which can be combined with other embodiments described herein, an aspect ratio of L_pi/D_pi equal or larger than 0.6 is provided, wherein L_pi is the axial distance between the first perimetric press fit 131 and the first axial pressing 141, and wherein D_pi is the inner diameter of one-piece shaft sleeve 12 at the first perimetric press fit 131, as exemplarily shown in figures 1 to 3. In other words, the aspect ratio L_pi/D_pi can be L_pi/D_pi > 0.6, particularly L_pi/D_pi > 0.7. Additionally or alternatively, an aspect ratio of L_p2/Dp2 equal or larger than 0.6 is provided, wherein L_p2 is the axial distance between the second perimetric press fit 132 and the second axial pressing 142, and wherein D_p2 is the inner diameter of the one-piece shaft sleeve 12 at the second perimetric press fit 132. In other words, the aspect ratio L_p2/D_p2 can be L_p2/D_p2 > 0.6, particularly L_p2/D_p2 > 0.7.

[0028] According to embodiments, which can be combined with other embodiments described herein, a radial gap 135 at the first axial end 123 of the shaft sleeve 12 and the shaft 11 can be provided. Additionally or alternatively a radial gap 136 at the second axial end axial end 124 of the shaft sleeve 12 and the shaft 11 can be provided.

[0029] According to embodiments, which can be combined with other embodiments described herein, the shaft 11 includes a shaft shoulder 111 for providing a stop for the axial clamping 14 of the shaft sleeve 12. In particular, the shaft shoulder 111 can be provided on a turbine side of the main shaft of the turbomachine, particularly when the turbomachine is a turbocharger.

[0030] A "shaft shoulder" can be understood as a designed feature or component on the shaft that serves as a stop. Typically, the shaft shoulder is provided by widened or thickened section of the shaft. The function of the shaft shoulder is to act as a stop for the axial clamping 14 of the shaft sleeve 12. In other words, typically the axial clamping presses or abuts directly or indirectly (i.e. via an intermediate element, e.g. a ring element as described in the following) against the shaft shoulder, preventing further movement of the shaft sleeve in the axial direction, such that the shaft sleeve is axially clamped.

[0031] According to embodiments, which can be combined with other embodiments described herein, a ring element 15, particularly a thrust ring, is arranged between the shaft shoulder 111 and the shaft sleeve 12. Typically, the ring element 15 is arranged between the shaft shoulder 111 and the second axial end 124 of the shaft sleeve 12. Alternatively, (not explicitly shown in the figures) the ring element 15 can be arranged around the shaft 11 on the first axial end 123 of the shaft sleeve 12. For instance, the ring element 15 on the first axial end 123 can be arranged between the shaft sleeve 12 and a radial disc 19, particularly a sealing disc, as described herein. Further, it is to be understood that one or more ring elements, particularly thrust rings, can be arranged around the shaft 11 on the first axial end 123 of the shaft sleeve 12 and/or on the second axial end 124 of the shaft sleeve 12. Typically, the one or more ring elements are separate elements. According to embodiments, which can be combined with other embodiments described herein, at least one of the one or more ring elements can be an integral part of the shaft sleeve 12.

[0032] According to embodiments, which can be combined with other embodiments described herein, the axial clamping 14 is provided by a preload exerted by a screw connection 16. In particular, the pre-load may exclusively be provided by a screw connection as described herein. For instance, the screw connection 16 providing the pre-load can be a screw connection of a rotor 17 with the shaft 11. Alternatively, the screw connection 16 providing the pre-load can be a screw connection of a nut 18 with the shaft 11. In particular, the nut 18 is used to axially fix a rotor on the shaft 11. The rotor 17 fixed to the shaft 11 by the screw connection 16 may be a compressor wheel 211. Although not explicitly shown in the figures, it is to be understood that alternatively the rotor fixed to the shaft 11 by the screw connection 16 can be a turbine wheel.

[0033] In the present disclosure, a “pre-load exerted by a screw connection” can be understood as referring to a controlled application of force or tension for providing the axial clamping of the shaft sleeve, as described herein, by tightening the screw connection. In other words, the pre-load can be achieved by applying force through the screw connection to create the axial clamping effect, particularly with a pre-defined force or tension.

[0034] According to embodiments, which can be combined with other embodiments described herein, the damping assembly 10 further includes a radial disc 19 provided at the first axial end 123 of the shaft sleeve 12. In particular, the radial disc may be arranged between a rotor 17 as described herein and the first axial end 123 of the shaft sleeve 12. For instance, the radial disc 19 can be a sealing disc. A “sealing disc” can be understood as disc specifically configured to provide a seal or barrier between two adjacent components, e.g. the rotor and the shaft sleeve described herein, particularly to prevent leakage or ingress of fluids, such as lubricants or contaminants, into or out of the damping assembly.

[0035] According to embodiments, which can be combined with other embodiments described herein, the damping assembly 10 further includes a third perimetric press fit 133 between the shaft sleeve 12 and the shaft 11. For instance, the third perimetric press fit 133 can be provided at the first end portion 121. Additionally or alternatively, the damping assembly 10 may further include a fourth perimetric press fit 134 between the shaft sleeve 12 and the shaft 11. The fourth perimetric press fit 134 can be provided at the second end portion 122. Typically, the third perimetric press fit 133 is provided in proximity of or adjacent to the first perimetric press fit 131. Depending on the axial position of the first perimetric press fit 131, the third perimetric press fit 133 may be arranged closer to the first axial end 123 than the first perimetric press fit 131 or farther away from the first axial end 123 than the first perimetric press fit 131. Typically, the fourth perimetric press fit 134 is provided in proximity of or adjacent to the second perimetric press fit 132. Depending on the axial position of the second perimetric press fit 132, the fourth perimetric press fit 134 may be arranged closer to the second axial end 124 than the second perimetric press fit 132 or farther away from the second axial end 124 than the second perimetric press fit 132. Further, it is to be understood, that according to embodiments, which can be combined with other embodiments described herein, only one of the third perimetric press fit 133 and the fourth perimetric press fit 134 can be provided, e.g. arranged in an area of the enlarged diameter shaft sleeve portion 125 described in the following.

[0036] According to embodiments, which can be combined with other embodiments described herein, the shaft sleeve 12 has an enlarged diameter shaft sleeve portion 125 with a maximal diameter D_max and an axial length 1, wherein a ratio D_max/1 is 0.54 < D_max/1 < 2.8. Additionally or alternatively a ratio D_max/L is 0.24 < D_max/L < 0.38, wherein L is the total axial length of the sleeve 12. With exemplary reference to Fig. 2, it is to be understood that D_max may be the diameter of one or more end shoulders of the enlarged diameter shaft sleeve portion 125, particularly a first end shoulder 127 and/or a second end shoulder 128. In the case that no end shoulders are provided, it is to be understood that D_max refers to the diameter of the enlarged diameter shaft sleeve portion 125. Accordingly, it is to be understood that the enlarged diameter shaft sleeve portion 125 may include first end shoulder 127 on a first end of the enlarged diameter shaft sleeve portion 125. Additionally or alternatively, the enlarged diameter shaft sleeve portion 125 may include a second end shoulder 128 on a second end of the enlarged diameter shaft sleeve portion 125. With exemplary reference to Fig. 2, it is to be understood that the first end of the enlarged diameter shaft sleeve portion 125 and the second end of the enlarged diameter shaft sleeve portion 125 are axially opposite ends.

[0037] According to embodiments, which can be combined with other embodiments described herein, wherein the shaft sleeve 12 has a radial outer seat 126 for one or more magnets 231 of an electric machine 23. In particular, the electric machine 23 is a permanent excited e-machine, particularly a permanent excited synchronous machine. For instance, the radial outer seat 126 can be provided at the enlarged diameter shaft sleeve portion 125 as described herein. The enlarged diameter shaft sleeve portion 125 may have a first diameter DI and a second diameter D2, wherein the first diameter DI is larger than the second diameter D2, as exemplarily shown in FIG. 2.

[0038] A " seat for one or more magnets" can be understood as a specific feature or component of the shaft sleeve configured to position or accommodate one or more magnets. In other words, a radial outer seat for one or more magnets on the shaft sleeve serves as a location or space on the outer surface of the shaft sleeve where one or more magnets are placed.

[0039] A "permanent excited e-machine" refers to an electric machine, e.g. an electric motor or generator, that relies on a permanent magnet for its magnetic field rather than using field windings with an external power source. These machines are also known as permanent magnet machines. In a permanent excited e-machine, the magnetic field required for its operation is generated by permanent magnets. These magnets are typically made from materials like neodymium, samarium-cobalt, or ferrite. They retain their magnetic properties without the need for an external power supply. Permanent magnet machines are known for their simplicity and high efficiency. They eliminate the need for field windings and the associated power consumption required to create a magnetic field, making them more energy-efficient. Further, permanent magnet machines have the advantage that they can be more compact and lightweight than with field-wound machines. Moreover, permanent magnet machines can offer precise control over their output, making them well-suited for applications where variable speed and torque control are important. Yet further, permanent magnet machines can be used for regenerative braking. They can work as generators to convert kinetic energy back into electrical energy during braking or deceleration, which helps to improve overall efficiency.

[0040] With exemplary reference to Fig. 4, is to be understood that according to a further aspect of the present disclosure, a turbomachine 20 including a damping assembly 10 for damping torsional vibrations of a shaft 11 according to any embodiments describe herein is provided. In particular, the turbomachine 20 can be a turbocharger. For instance, the shaft may connect a compressor wheel 211 of a compressor 21 with a turbine wheel 221 of a turbine 22.

[0041] According to embodiments, which can be combined with other embodiments described herein, the turbomachine 20 further includes an electric machine 23. Accordingly, the turbomachine 20 can be an electrified turbocharger, an electrified compressor, or an electrified turbine. In particular the electric machine 23 can be a permanent excited e-machine. For instance, the electric machine 23 can be arranged between the compressor wheel 211 and the turbine wheel 221. More specifically, the electric machine 23 typically includes one or more magnets 231 mounted on a radial outer seat 126 of the sleeve 12. It is to be understood that one or more magnets 231 mounted on a radial outer seat 126 of the sleeve 12 may also be referred to as rotor magnets of the electric machine. Further, as exemplarily shown in Fig. 4, one or more stator magnets 232 surrounding the one or more rotor magnets 231 of electric machine are typically provided. The one or more magnets 231 mounted on a radial outer seat 126 may be held by a sleeve, particularly a carbon fiber sleeve, arranged around the one or more magnets 231. According an example, the one or more magnets 231 may be arranged between balancing plates 24 mounted on the sleeve. The balancing plates can be an integral part of the shaft sleeve 12.

[0042] With exemplary reference to the flow diagram of Fig. 5, embodiments of a method 30 of damping torsional vibrations of a shaft 11 according to the present disclosure are described.

[0043] According to embodiments, which can be combined with other embodiments described herein, the method 30 includes damping (represented by block 31 in Fig. 5) torsional vibrations by friction, particularly micro friction, between a shaft sleeve 12 provided around the shaft 11. The friction is provided at interfaces of an axial clamping 14 of the shaft sleeve 12, at a first perimetric press fit 131 interface between a first end portion 121 of the shaft sleeve 12 and the shaft 11, and at a second perimetric press fit 132 interface between a second end portion 122 of the shaft sleeve 12 and the shaft 11. Typically, the method further includes using (represented by block 32 in Fig. 5) a damping assembly 10 according to any embodiments described herein.

[0044] It is to be understood that in the present disclosure, the terms "friction" and "micro friction" refer to mechanisms used to dampen or reduce torsional vibrations.

[0045] Friction is a force that opposes the relative motion or tendency of motion between two surfaces in contact with each other. It acts tangentially to the surfaces and is caused by the interaction of molecules at the surfaces. It can manifest as a resistance to sliding, rolling, or any other movement between the surfaces. In the context of damping torsional vibrations, friction is used as a means to absorb or dissipate some of the mechanical energy created by these vibrations. By creating resistance within the system, friction helps reduce the oscillations and stabilize the motion.

[0046] Micro friction is a specific type of friction that operates at a very small scale, typically involving very low forces and minute surface interactions. It is often used to describe the frictional behavior at a microscopic or nanoscale level. In the context of the method as described herein, "micro friction" is employed to indicate that the friction used to dampen torsional vibrations is at a tiny or microscale level. This may involve the use of specialized materials, coatings, or surface treatments to generate extremely low levels of friction, which can be effective in reducing the vibrations without causing significant wear and tear on the components.

[0047] In view of the embodiments described herein, it is to be understood compared to the state of the art, an improved damping assembly and an improved method of damping torsional vibrations of a shaft , particularly a main shaft of a turbomachine, are provided. In particular, embodiments of the present disclosure beneficially provide a simple and cost-effective damping approach with high torsional damping capability against excitation of the shaft, for example induced at the electric machine and/or at the shaft end, i.e. at the rotor position, e.g. the compressor or turbine position. Accordingly, embodiments described herein beneficially provide for a smooth operational behavior minimizing the risk for a rotor breakdown.

[0048] Further, it is to be noted that embodiments of the present disclosure are of particularly well suited for shafts of large frame turbochargers, i.e. having shafts with a diameter of more than 150 mm. Large frame turbochargers typically have shafts which are welded to the turbine head, forming an inseparable connection with the shaft. As consequence the assembly of the whole machine is limited or in other words to a certain extend predetermined. Furthermore, due to the high lifetime requirements in the power generation and marine sector (~80 khrs) and in contrast to the automotive industry, such turbochargers are reliant to repetitious service and inspection possibilities.

[0049] While the foregoing is directed to embodiments, other and further embodiments may be devised without departing from the basic scope, and the scope is determined by the claims that follow.

REFERENCE NUMBERS

10 damping assembly

11 shaft

110 central axis of the shaft

111 shaft shoulder

12 one-piece shaft sleeve

121 first end portion of the shaft sleeve

122 second end portion of the shaft sleeve

123 first axial end

124 second axial end

125 enlarged diameter shaft sleeve portion

126 radial outer seat

127 first end shoulder

128 second end shoulder

131 first perimetric press fit

132 second perimetric press fit

133 third perimetric press fit

134 fourth perimetric press fit

13 radial gap

135 radial gap at first axial end

136 radial gap at second axial end

14 axial clamping

141 first axial pressing

142 second axial pressing

15 ring element

16 screw connection

17 rotor

18 nut

19 radial disc

20 turbomachine 21 compressor

211 compressor wheel

22 turbine

221 turbine wheel

23 electric machine

231 one or more rotor magnets of electric machine

232 one or more stator magnets

24 balancing plates

25 coils

30 method for damping torsional vibrations of a shaft

31, 32 blocks of flow diagram for illustrating embodiments of the method for damping torsional vibrations of a shaft

1 axial length of enlarged diameter shaft sleeve portion

L axial length of one-piece shaft sleeve

D_max maximal diameter of enlarged diameter shaft sleeve portion

D_out outer diameter of one-piece shaft sleeve

Dpi inner diameter of one-piece shaft sleeve at first perimetric press fit

L_pi axial distance between first perimetric press fit and first axial pressing D_p2 inner diameter of one-piece shaft sleeve at second perimetric press fit L_p2 axial distance between second perimetric press fit and second axial pressing

Di first diameter of enlarged diameter shaft sleeve portion

D₂ second diameter of enlarged diameter shaft sleeve portion d diameter of the shaft r radial direction x axial direction

Claims

1. A damping assembly (10) for damping torsional vibrations of a shaft (11), particularly a main shaft of a turbomachine (20), the damping assembly (10) comprising: a one-piece shaft sleeve (12) provided around the shaft (11), the one-piece shaft sleeve (12) has an aspect ratio L/D_out > 2, wherein L is an axial length of the one-piece shaft sleeve (12), and wherein D_out is an outer diameter of the one-piece shaft sleeve (12); an axial clamping (14) of the one-piece shaft sleeve (12); a first perimetric press fit (131) between a first end portion (121) of the one-piece shaft sleeve (12) and the shaft (11); and a second perimetric press fit (132) between a second end portion (122) of the one-piece shaft sleeve (12) and the shaft (11); wherein between the first perimetric press fit (131) and the second perimetric press fit (132) a radial gap (13) between the one-piece shaft sleeve (12) and the shaft (11) is provided.

2. The damping assembly (10) of claim 1, wherein the axial clamping (14) is provided by a first axial pressing (141) at a first axial end (123) of the one- piece shaft sleeve (12) and a second axial pressing (142) at a second axial end (124) of the one-piece shaft sleeve (12).

3. The damping assembly (10) of claim 1 or 2, wherein the shaft (11) includes a shaft shoulder (111) for providing a stop for the axial clamping (14) of the one-piece shaft sleeve (12), particularly the shaft shoulder (111) being provided on a turbine side of the main shaft of the turbomachine.

4. The damping assembly (10) of claim 3, wherein a ring element (15), particularly a thrust ring, is arranged between the shaft shoulder (111) and the one-piece shaft sleeve (12), particularly the second axial end (124) of the one-piece shaft sleeve (12).

5. The damping assembly (10) of any of claims 1 to 4, wherein the axial clamping (14) is provided by a pre-load exerted by a screw connection (16).

6. The damping assembly (10) of claim 5, wherein the screw connection (16) providing the pre-load is a screw connection of a rotor (17) with the shaft (11) or a screw connection of a nut (18) with the shaft, particularly the nut (18) being used to axially fix a rotor on the shaft (11).

7. The damping assembly (10) of claim 6, wherein the rotor (17) is a compressor wheel (211).

8. The damping assembly (10) of any of claims 2 to 7, further comprising a radial disc (19), particularly a sealing disc, provided at the first axial end (123) of the one-piece shaft sleeve (12), particularly the radial disc (19) being arranged between a rotor (17) and the first axial end (123) of the one-piece shaft sleeve (12).

9. The damping assembly (10) of any of claims 1 to 8, further comprising at least one of a third perimetric press fit (133) between the one-piece shaft sleeve (12) and the shaft (11) and a fourth perimetric press fit (134) between the one-piece shaft sleeve (12) and the shaft (11), in particular wherein the third perimetric press fit (133) is provided at the first end portion (121), and in particular wherein the fourth perimetric press fit (134) is provided at the second end portion (122).

10. The damping assembly (10) of any of claims 1 to 9, wherein the one-piece shaft sleeve (12) has an enlarged diameter shaft sleeve portion (125) with a maximal diameter D_max and an axial length 1, wherein a ratio D_max/1 is

0.54 < D_max/1 < 2.8, and/or wherein a ratio D_max/L is 0.24 < D_max/L < 0.38, wherein L is the total axial length of the sleeve (12).

11. The damping assembly (10) of any of claims 1 to 10, wherein the one- piece shaft sleeve (12) has a radial outer seat (126) for one or more magnets (231) of an electric machine (23), particularly a permanent excited e- machine, particularly the radial outer seat (126) being provided at the enlarged diameter shaft sleeve portion (125) of claim 10.

12. The damping assembly (10) of any of claims 2 to 11, wherein an aspect ratio Lpi/Dpi is > 0.6, wherein L_pi is an axial distance between the first perimetric press fit (131) and the first axial pressing (141), and wherein Dpi is an inner diameter of one-piece shaft sleeve (12) at the first perimetric press fit (131).

13. The damping assembly (10) of any of claims 2 to 12, wherein an aspect ratio L_p2/Dp2 is > 0.6, wherein L_p2 is an axial distance between the second perimetric press fit (132) and the second axial pressing (142), and wherein D_p2 is an inner diameter of the one-piece shaft sleeve (12) at the second perimetric press fit (132).

14. A turbomachine (20), particularly a turbocharger, comprising a damping assembly (10) according to any of claims 1 to 12, particularly the shaft (11) connecting a compressor wheel (211) of a compressor (21) with a turbine wheel (221) of a turbine (22).

15. The turbomachine (20) of claim 13, further comprising an electric machine (23), particularly a permanent excited e-machine, arranged between the compressor wheel (211) and the turbine wheel (221), in particular the electric machine (23) comprising one or more magnets (231) mounted on a radial outer seat (126) of the one-piece shaft sleeve (12), particularly the one or more magnets (231) being arranged between balancing plates (24) mounted on the one-piece shaft sleeve.

16. A method (30) of damping torsional vibrations of a shaft (11), particularly a main shaft of a turbomachine (20), the method (30) comprising damping (31) torsional vibrations by friction, particularly micro friction, between a one-piece shaft sleeve (12) provided around the shaft (11), the one-piece shaft sleeve (12) has an aspect ratio L/D_out > 2, wherein L is an axial length of the one-piece shaft sleeve (12), and wherein D_out is an outer diameter of the one-piece shaft sleeve (12), the friction being provided at interfaces of an axial clamping (14) of the one-piece shaft sleeve (12), at a first perimetric press fit (131) interface between a first end portion (121) of the one-piece shaft sleeve (12) and the shaft (11), and at a second perimetric press fit (132) interface between a second end portion (122) of the one-piece shaft sleeve (12) and the shaft (11), wherein between the first perimetric press fit (131) and the second perimetric press fit (132) a radial gap (13) between the one-piece shaft sleeve (12) and the shaft (11) is provided.

17. The method (30) of claim 16, further comprising using (32) a damping assembly (10) according to any of claims 1 to 13.