Patent Application
20250012294
The present invention relates to turbo machine, e.g., a cryogenic turbo machine, with an impeller mounted on a shaft and one or more guide vanes, and to a method of manufacturing such turbo machine.
Turbo machines can be used in different applications. For example in cryogenic applications, i.e. applications with process gases at cryogenic temperatures, e.g., plants for air separation or the like, cryogenic turbo machines like turbo expanders and/or compressors are often used. Such turbo machines typically comprise an expander impeller and/or a compressor impeller, which are fixed on a shaft.
Such turbo machines typically also comprise guide vanes configured to guide operating fluid, e.g., gas like the mentioned process gas, to or from such impeller. Such guide vanes can be movably arranged in the turbo machine in order to change the angle with which the fluid arrives on or leaves the impeller. Moving guide vanes can cause wear, scratches and rubbing; this can lead to the turbo machine (and possibly other parts of a system) to get stuck. It is therefore an object of the present invention to provide an improved turbo machine.
This object is achieved by providing a turbo machine and a method of manufacturing such a turbo machine with the features of the independent claims. Embodiments of the invention are the subject of the dependent claims and of the description that follows.
The invention relates to turbo machines, in particular cryogenic turbo machines, like turbo compressors or turbo expanders with an impeller arranged or mounted on a shaft. Cryogenic turbo machines are used with operating fluid like gases or process gases at cryogenic temperatures, i.e., very low temperatures of, e.g., less than-100° C. at the expander outlet or at the compressor inlet. Depending on the kind of turbo machine, such gases are compressed and/or expanded. Turbo machines in other applications can also be used with operating fluids at higher temperatures.
Such turbo machine also comprises one or more guide vanes configured to guide operating fluid, e.g., gas like the mentioned process gas, to or from the impeller. Typically, several guide vanes are arranged, preferably, in an equally distributed manner. These guide vanes are used to properly guide or direct the fluid in a desired manner or desired angle onto the impeller (for an expander) or away from the impeller (for a compressor).
One or several or all of such guide vanes (often also referred to as nozzles) can be movably arranged in the turbo machine in order to change the angle with which the fluid arrives on or leaves the impeller. This allows, for example, regulating the flow according to process requirements, changing efficiency and the like. The guide vanes can be moved, e.g., continuously and/or with small steps. In particular, the turbo machine can be configured to automatically move the guide vanes, e.g., according to current needs.
These guide vanes can be arranged in relation to one or more (other) components of the turbo machine, e.g., support rings, such that the guide vanes are in contact with this one or more components and such that the guide vanes are movable relative to such one or more components. This avoids any bypassing of operating fluid flowing along the guide vanes and onto or from the impeller; aerodynamic expansion and/or compression efficiency is increased in this way.
Since frequencies and amplitudes of the moving or displacements of moving of such guide vanes are variable, this can cause wear, scratches and rubbing; this can lead to the turbo machine (and possibly other parts of a system) getting stuck. The flow can then not be modified anymore and not be adapted to the process requirements. The turbo machine needs then to be stopped and dismantled.
It has now been recognized that providing diamond like carbon coating very efficiently reduces friction between the guide vanes and other components, i.e., when at least one contact surface between said one or at least one of the more guide vanes and said one or more components comprises a diamond like carbon coating. In particular, such diamond like carbon coating (also referred to as diamond like coating or just diamond like carbon) efficiently reduces friction also for low operating temperatures, i.e., it can be used in cryogenic turbo machines.
Said at least one contact surface can comprise at least one surface of said one or at least one of the more guide vanes. Also, said at least one contact surface can comprise at least one surface of said one or more components. In order to even more reduce friction and to even better avoid wear, the contact surfaces can comprise both, i.e., diamond like carbon coating is provided on the guide vane(s) and the one or at least one of the more components.
Diamond like carbon coating—also referred to as diamond like coating or just diamond like carbon (DLC)—is a class of amorphous carbon (a-C) material that displays some of the typical properties of diamond, and also of graphite. Diamond like carbon can be applied as coatings to other materials that could benefit from such properties. Diamond like carbon exists in different forms. All forms typically contain significant amounts of sp3 hybridized carbon atoms. The reason that there are different types is that even diamond can be found in two crystalline polytypes. The more common one uses a cubic lattice, while the less common one, lonsdaleite, has a hexagonal lattice. By mixing these polytypes at the nanoscale, diamond like carbon coatings can be made, which at the same time are amorphous, flexible, and yet purely sp3 bonded “diamond”. Fillers such as hydrogen (H), tungsten (W), graphitic sp2 carbon, and other metals can be used to reduce production expenses or to impart other desirable properties. Also, additional layers (also indicated with a “+” symbol) like chrome nitride (CrN) can be used, which typically are provided between the support material and the actual diamond like carbon. Then, the diamond like carbon coating can be considered comprising diamond like carbon and a further layer.
Preferred diamond like carbon forms to be provided at the surfaces of the guide vanes and/or other components comprise at least one of: a-C:H:W, a-C:H:W+a-C:H, CrN+a-C:H, a-C:H, Cr+a-C:H:W, Cr+a-C:H:W+a-C:H, Cr+CrN+a-C:H, Cr+a-C:H.
The invention also relates to a method for manufacturing such turbo machine as described above. Said method comprises providing said at least one contact surface with said diamond like carbon coating, i.e., said diamond like carbon coating is provided onto said one or at least one of the more guide vanes and/or onto said one or more components. This can be by at least one of: CVD (Chemical Vapour Deposition) or PVD (Physical Vapour Deposition). The PVD methods can be divided into: arc, sputter, and laser vapour deposition methods. The CVD methods like plasma-assisted chemical vapour deposition (PACVD), or plasma enhance chemical vapour deposition, (PECVD) methods can be divided into: radio-frequency (RF), direct current (DC) discharge, Penning ionization gauge (PIG), and self-discharge methods.
The provision of the diamond like carbon coating typically takes place before assembling the entire turbo machine, such that the guide vanes and/or components to be provided with the coating, are accessible.
Plasma-assisted chemical vapour deposition is a chemical vapour deposition process used to deposit thin films from a gas state (vapour) to a solid state on a substrate. Chemical reactions are involved in the process, which occur after creation of a plasma of the reacting gases. The plasma can be created by radio frequency (RF), using alternating current (AC) frequency, or direct current (DC) discharge between two electrodes, the space between which is filled with the reacting gases.
Ion beam deposition (IBD) is a process of applying materials to a target through the application of an ion beam. https://en.wikipedia.org/wiki/File:Ion_implanter_schematic.png An ion beam deposition apparatus typically consists of an ion source, ion optics, and the deposition target. Optionally a mass analyser can be incorporated. In the ion source, source materials in the form of a gas, an evaporated solid, or a solution (liquid) are ionized. For atomic IBD, electron ionization, field ionization (Penning ion source) or cathodic arc sources are employed. Cathodic arc sources are used particularly for carbon ion deposition. Molecular ion beam deposition employs electrospray ionization or so-called MALDI sources.
Sputter deposition is a physical vapour deposition (PVD) method of thin film deposition by sputtering. This involves ejecting material from a “target” that acts as a source onto a “substrate” such as the guide vane or the other components, which are typically made of metal like steel.
Depending on the desired thickness and/or hardness of the DLC coating, for example, an appropriate deposition method can be chosen. we can get thicker or smoother or harder coatings.
The advantages of the present invention are, in particular, reducing the friction coefficient and avoiding any stuck of the guide vanes (or nozzle) when moving them. This, in particular, is possible for low temperatures like down to −100° C. and below at the guide vanes, what is a typical temperature for operational fluid at the guide vanes in cryogenic turbo machines.
Turbo machine 200 comprises an impeller 220, mounted on a shaft 230. The turbo machine 200 comprises openings 222 and 224 on the side of the impeller 220, the openings used as inlet 222 and outlet 224 for operating fluid to be expanded. An inlet flow of operating fluid is denoted 223, and an outlet flow of operating fluid is denoted 225.
The turbo machine 200 comprises several guide vanes 240 movably arranged therein and arranged in relation to, by means of example, two components in the form of support rings 250 and 252. A channel following the inlet 222 is formed such that the operating fluid (See flow 223) is guided from radial outwards in the direction of the guide vanes 240.
Each of the guide vanes 240 is mounted onto the support ring 252 by means of a pin 264, for example, such that the guide vane 240 is movable relative to the support ring 252. This can be performed, for example, by means of a moving arrangement 260, comprising an (outer) ring 262 having support elements 261 therein, each of which is connected to a respective guide vane 240 by means of a pin 263. When the ring 262 is slightly rotated in the one or the other direction, the guide vanes 240 are moved such that the angle or direction for the flow 223 is changed.
As can be seen from
When the guide vanes 240 are moved as described above, the mentioned contact surfaces, abutting each other, move relative to each other; this can cause wear, scratches and rubbing, in particular, because frequencies and amplitudes of the moving or displacements of such moving guide vanes are variable.
In order to reduce the friction coefficient between these contact surfaces and to avoid (or at least reduce) wear, scratches and rubbing, a diamond like carbon coating 270 is provided on the respective components, the guide vanes 240 and the support rings 250, 252, such that the mentioned contact surfaces comprises said diamond like carbon coating 270. It is noted that such diamond like carbon coating 270 should, preferably, be provided at every possible area of contact.
The way of how to provide the diamond like carbon coating (deposition method) in step 602 and/or in step 604 is, e.g., one of chemical vapour deposition (CVD), or physical vapour deposition (PVD). PVD methods can be divided into, e.g. arc, sputter, and laser vapour deposition methods. CVD methods can be divided into, e.g., radio-frequency (RF), direct current (DC) discharge, Penning ionization gauge (PIG), and self-discharge methods. Depending on the specific needs or requirements, different deposition methods can be used in step 602 and in step 604, i.e., the guide vanes on the one hand and the support rings on the other hand can be coated in the same way or in different ways; this may lead to different kind of diamond like carbon coatings, some of which are mentioned above.
| Number | Date | Country | Kind |
|---|---|---|---|
| 21315248.1 | Nov 2021 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/025525 | 11/21/2022 | WO |
