Turbomachine with optimised cooling of the sliding ring seal

Abstract

NOT VISIBLE DUE TO STATUS OF PATENT

Description

[0001] Description

[0002] Turbomachine with optimized cooling of the mechanical seal

[0003] The present invention relates to a turbomachine having a housing and a shaft rotating therein, wherein the shaft is sealed from the housing by means of at least one mechanical seal and the rotation of the shaft generates a swirling flow of a working fluid located in the region of the mechanical seal.

[0004] Turbomachines include all machines through which a working fluid or a fluid containing solids flows and which are equipped with a bladed impeller to convert mechanical energy (e.g., rotational energy of a shaft) into fluid energy (e.g., total pressure of the fluid). Depending on the direction of energy transfer, whether from the turbomachine shaft to the fluid or from the fluid to the shaft, a distinction is made between the "working machine" (e.g., centrifugal pump, turbocompressor, fan) and the "power machine" (e.g., steam, gas, wind, liquid, and especially water turbines).

[0005] The outlet of the rotating shaft from the housing of the turbomachine is usually reliably and safely sealed by a mechanical seal. The heat generated by friction in the sealing contacts of the mechanical seal leads to a local temperature increase, which must be minimized to extend the service life and increase the reliability of the seal. Cooling of the mechanical seal by the working fluid flowing around the seal is often insufficient due to its design and application. In particular, unfavorable flow conditions can arise in the area of ​​the mechanical seal due to the design, which means that heat dissipation by the working fluid is inadequate. For example,The generation of local vortexes and / or recirculation areas in the area of ​​the mechanical seal results in the thermal energy absorbed by the working fluid being circulated only locally, but not being transported away from the mechanical seal and transferred to the housing. In practice, external cooling circuits have so far been used to provide dedicated cooling for the seal. However, external circuits require additional design measures, which increases the complexity of the machine and raises manufacturing and maintenance costs.

[0006] The problem of unfavorable flow conditions in the area of ​​the mechanical seal will be illustrated below using the schematic representation in Fig. 1, which shows only the relevant section of the housing 1 of a turbomachine with the mechanical seal mounted there. A partial section of the rotating working shaft 5 of the turbomachine, in particular of a centrifugal pump, is shown. The shaft 5 emerges from the housing at one end; the shaft outlet is sealed by the mechanical seal consisting of the stationary counter ring 3 and the slide ring 4. The stationary counter ring 3 is fixed to the housing 1 via the counterholder 2, with the connection sealed by the static seal 9. The rotating slide ring 4 is mounted on the shaft 5 in a rotationally fixed manner.Reference numeral 6 denotes a static seal, and reference numeral 7 denotes a preloading element, which preloads the mechanical seal ring 4 axially toward the counter ring 3. The housing 1 also provides a sealing gap 8 toward the pump's bearing bracket, through which the working fluid can flow from the pump chamber into the area of ​​the mechanical seal. The rotating shaft creates a swirling flow of the working fluid in the area of ​​the mechanical seal.

[0007] In particular, the surface contour 4a of the rotating seal ring 4, which slopes downwards toward the stationary counter ring 3, results in the creation of a local vortex 11 in the immediate vicinity of the mechanical seal in the housing chamber. This vortex 11 is separated from the remaining flow 13 of the working fluid by a jet stream 12 extending radially / axially outward from the mechanical seal toward the housing. Due to the locally limited turbulence / recirculation 11, the thermal energy absorbed by the working fluid there, generated by the frictional work in the seal contact, cannot be effectively dissipated, as heat exchange is only possible at the interface between the vortex 11 and the jet 12. The same applies to particles abraded by the sliding surfaces.In addition to the vortex 11, several smaller unfavorable vortices 14 are created by detachment on the inner and outer contours of the housing 1 and the counterholder 2, in particular in the corner areas or in the area of ​​radial shoulders, in particular in the axial transition between the rings 3, 4.

[0008] The object of the present invention is to achieve improved flow of the working fluid in the area of ​​the mechanical seal through design measures, thus achieving better heat dissipation and cooling of the mechanical seal. Furthermore, the convective removal of particles from the area of ​​mechanical seal contact is to be optimized.

[0009] This object is achieved by a turbomachine having the features of claim 1. Starting with the generic turbomachine, it is proposed to provide at least one drive component driven by the shaft in the immediate vicinity of the mechanical seal, which drive component is suitable for generating a secondary flow superimposed on the swirl flow in the region of the mechanical seal. By arranging the additional drive component rotating with the shaft in the immediate vicinity of the mechanical seal and by its suitable design, a specifically defined secondary flow can be actively generated in the region of the mechanical seal, which ensures improved heat dissipation and / or particle removal, since local unfavorable vortex formation is prevented and efficient convective dissipation of the thermal energy by the working fluid is possible.At the same time, the convective removal of abraded particles in the seal contact area is promoted, thus achieving improved flushing of the mechanical seal. The secondary flow is primarily a large-scale flow circulating within an available space in the housing. The swirling flow of the working fluid in the area of ​​the mechanical seal can be generated by the rotating shaft.

[0010] The fluid machine can be a pump, in particular a centrifugal pump.

[0011] The at least one drive component can either be located directly on the shaft or instead be arranged on a component rotating with the shaft, e.g. a preloading element for axially preloading the rotating seal ring. The drive component can be designed in the form of a rotating disk or a rotating bladed impeller. Preferably, the rotating drive component(s) is / are designed such that pressure conditions are generated in the vicinity of the mechanical seal that form one or more secondary flows with axial and radial components in addition to the swirl flow of the working fluid. The secondary flow(s) are directed in a targeted manner to the most important surfaces of the mechanical seal components that are to be cooled. Both the axial and the radial flow components are to be understood as a flow direction relative to the shaft axis.In particular, at least one secondary flow is guided in a targeted manner along the surface of the mechanical seal, in particular the rings of the mechanical seal. Targeted guidance along the relevant surface of a counterholder is also conceivable.

[0012] It is particularly advantageous if one or more flow-guiding components are arranged in the space between the mechanical seal and the housing, in particular in the radial and / or axial space. For example, such a flow-guiding component can be arranged centrally in the space between the outer housing wall and the mechanical seal. The flow-guiding component extends in both the axial and radial directions; preferably, the component extends in a ring around the mechanical seal in the housing space. Such a flow-guiding component enables, in particular, a circulating secondary flow in the flow paths formed by the flow-guiding component itself and optionally one or more further components, such as the housing, the seal rings, the preload element, and the counterholder.It is conceivable, for example, that this flow-guiding component defines an axial flow channel between the housing wall and the flow-guiding component, as well as a parallel channel between the mechanical seal and the flow-guiding component. Radial sections of the flow channel are preferably formed by the end surfaces of the housing or by a counterholder and the flow-guiding component.

[0013] The material used as the flow-guiding component can be solid or, alternatively, hollow. Any hollow space can preferably be filled with the working fluid or another fluid or material. The mounting of the flow-guiding component in the turbomachine can preferably be realized via one or more fixing points, via which the component is secured to the inner housing wall or to the counterholder of the mechanical seal. It is particularly advantageous if the component has an internal structure with optimized thermal conductivity and / or the one or more fixing points have high thermal conductivity, thus ensuring good heat transfer from the components to the housing or the counterholder.

[0014] It is particularly advantageous if, due to the design according to the invention, an external circuit for cooling and / or flushing the mechanical seal can be completely dispensed with and cooling and / or flushing of the mechanical seal is provided exclusively via the working fluid.

[0015] Furthermore, it can be provided that one or more guide elements are provided in the area of ​​the housing wall, which lies in the immediate area of ​​the secondary flow or the mechanical seal, and / or in the area of ​​a counter-holder of the stationary counter ring and / or in the area of ​​the drive component and / or in the area of ​​the pretensioning device and / or in the area of ​​the rings of the mechanical seal in order to prevent undesired vortex formation in corner areas or at radial steps. It is conceivable, for example, that corners and edges of the housing parts or transitions between different components, in particular the transition between the slide rings, are optimized in such a way that radial steps are minimized and local, unfavorable vortex formation, e.g. due to flow separation, is avoided.It is also conceivable that surfaces wetted with working fluid could be optimized for heat exchange by means of suitable texturing or other microscopic or macroscopic properties. The achievable drag effect of the drive component can also be improved through suitable surface design.

[0016] Further advantages and features of the invention will be explained in more detail below using an exemplary embodiment illustrated in the figures. They show:

[0017] Fig. 1 : a schematic structure of a turbomachine according to the state of the art,

[0018] Fig. 2: an embodiment of the turbomachine according to the invention.

[0019] Fig. 1 has already been described in detail in the introductory section, so a repetitive description will be omitted here. Components of the turbomachine according to the invention that are identical to the design shown in Fig. 1 are designated by identical reference numerals. The following will primarily address the modifications made to optimize the flow pattern of the working fluid in the area of ​​the mechanical seal.

[0020] The illustration in Fig. 2 shows the relevant section of a centrifugal pump.

[0021] The essential modification compared to the embodiment in Fig. 1 is the provision of a rotating drive component 20 which is actively driven via the shaft 5 and which can be designed, for example, as a disk with a viscous drag effect or as a bladed impeller. The rotating component 20 is used to generate pressure conditions in the vicinity of the mechanical seal which lead to the formation of one or more secondary flows (axial and radial flow components in addition to the swirl flow), whereby working fluid is directed specifically to the most important surfaces of the mechanical seal components that are to be cooled. The drive component 20 is located here on the circumference of the preload element 7 and rotates with the shaft 5 during regular operation of the turbomachine, but could alternatively also be mounted directly on the shaft. It is also conceivable that the preload element 7 itself ora specific section of shaft 5 can be used, of course with certain modifications to its outer contour.

[0022] The rotating drive component 20 generates the flow pattern indicated by arrows in Fig. 2, with axial and radial components, which circulates around a flow guide part 50 located centrally in the radial space between the housing 1 and the mechanical seal 30, 40. This flow guide part 50 can be made of solid material or be hollow, in which case the part 50 can be filled with working fluid or another fluid or material. The flow guide part 50 is mounted on the housing 1 via several fixing points (not shown here) and extends in a ring around the shaft or mechanical seal. The internal structure and the fixing points of the flow guide part 50 are optimized for heat dissipation; in particular, they are made of a material with high thermal conductivity, for example, aluminum or copper.The outer contour of the flow guiding component 50 is preferably designed for one or more operating points and / or operating point ranges of the turbomachine.

[0023] As can be seen from the illustration, the secondary flow is generated by the drive component 20 in the region of the housing end facing the pump bearing bracket and initially flows between the flow-guiding component 50 and the peripheral wall of the housing 1 in the axial direction to the counterholder 2. Guide elements 21 in the region of the housing corners and edges or in the transition area to the counterholder 2 minimize unwanted vortex formation in the area of ​​shoulders and edges, thereby ensuring a separation-free flow deflection at high flow velocity. In the area of ​​the counterholder 2, the working fluid is directed radially downwards towards the mechanical seal and flows there in the axial direction between the flow-guiding component 50 and the seal rings 30, 40 with the preload element 7 back to the drive component 20.In addition, the circumferential surfaces 30a, 40a of the seal rings 30, 40 are aerodynamically optimized to avoid radial steps in the transition area and thus further minimize the risk of local vortex formation. The design of the surface contour of the circumferential surface 30a of the stationary counter ring 30 enables separation-free flow deflection toward the rotating seal ring 40, whereby the working fluid flows along the contours 30a, 40a at the highest possible flow velocity (Reynolds number). The surface contour 40a of the rotating seal ring 40 prevents the generation of an undesirable axial / radial jet stream. In particular, the contour of the seal ring circumferential surfaces is adapted to the contour of the opposite surface of the flow-guiding component 50.

[0024] Due to the large-scale circulating secondary flow, absorbed heat energy in the area of ​​the sliding rings 30, 40 can be effectively transported away from the mechanical seal and released to the outside, for example via the flow-guiding component 50 with its heat-conducting fixing points.

[0025] The following are the individual essential features of the modifications made to the turbomachine in the area of ​​the mechanical seal:

[0026] The aim of the invention is to use design measures to specifically establish a flow condition that optimizes the convective cooling of mechanical seal rings and thus reduces the temperature inside and near the seal contact. The aim is to generate the fastest possible flow (high Reynolds number) in the form of a secondary flow superimposed on the swirl flow with axial and radial velocity components along the surfaces to be cooled. The flow condition thus represents a type of internal circulation, but is generated without additional active devices.

[0027] The secondary flow is driven by the rotational movement itself. The fluid's adhesion to rotating walls, along with the inertial effect of rotation (centrifugal force), can be utilized. Particularly at edges with a larger surface area than a uniform contour, e.g., at edges of cross-sectional discontinuities or lamellar shapes, the drag effect due to the fluid's adhesion can be used to generate radial velocity components. The contour of the rotating mechanical seal rings 40a, surfaces of pretensioning devices 7, or parts 20 installed specifically for this purpose on the shaft 5 or the pretensioning devices 7 can be utilized for this purpose.The flow can be guided by one or more components 21, 50 that are installed in the radial space between shaft 5 / mechanical seal 30, 40 and housing 1 and are connected at one or more points to housing 1 and / or stationary counterholder 2. The targeted flow guidance along the mechanical seal rings 30, 40 can also enable an optimized and controlled removal of particles (which, for example, arise during contact or are of other origin and have deposited there), as well as possibly their targeted transport to a filtration device. The invention does not require any external connections, additional fluid circuits, or further heat exchange devices; instead, the cooling effect is achieved internally through targeted flow guidance, driven by the rotational movement (as the energetic drive source).

[0028] The internals 20, 21, and 50 can be integrated into the initial design of a mechanical seal or retrofitted into an existing product. The internals can be optimized for specific operating points (speed, pressure, temperature, density, and viscosity of the fluid) and / or operating point ranges, e.g., operating points or ranges that are predominantly used.

[0029] The wetted surfaces of the internals can be optimized for heat exchange with the fluid, e.g., by texturing or other micro- and macroscopic surface properties. Furthermore, the surface properties can be deliberately adjusted to create a better drag effect of the fluid. The heat transferred from the fluid into the internals 50 can be dissipated from the mechanical seal area by heat transport in the internals 50 and their connection to the housing 1, counterholder 2, or possibly shaft 5. The internals can consist of one or more materials and be manufactured using different processes, e.g., die casting (aluminum), injection molding (plastic), 3D printing, or machining (turned and milled).

Claims

Patent claims 1. Turbomachine with a housing (1) and a shaft (5) rotating therein, wherein the shaft (5) is sealed off from the housing (1) by means of at least one mechanical seal (30, 40) and a swirling flow of a working fluid located in the region of the mechanical seal is generated by the rotation of the shaft, characterized in that in the immediate vicinity of the mechanical seal (30, 40) at least one drive component (20) driven by the shaft (5) is provided for generating at least one secondary flow of the working fluid superimposed on the swirling flow in the region of the mechanical seal (30, 40) for convection cooling of the mechanical seal (30, 40).

2. Turbomachine according to claim 1, characterized in that the drive component (20) is arranged on a prestressing element (7) for axially prestressing the rotating slide ring (40) of the mechanical seal.

3. Turbomachine according to one of the preceding claims, characterized in that the generated secondary flow has an axial and radial flow component.

4. Turbomachine according to one of the preceding claims, characterized in that the secondary flow is guided in a targeted manner along the surfaces (30a, 40a) of the rings (30, 40) of the mechanical seal.

5. Turbomachine according to one of the preceding claims, characterized in that one or more flow-guiding components (50) are arranged in the space between the mechanical seal (30, 40) and the housing (1) to guide the flow of the secondary flow.

6. Turbomachine according to claim 5, characterized in that the secondary flow circulates around at least one of the flow-guiding components (50).

7. Turbomachine according to one of claims 5 or 6, characterized in that the at least one flow-guiding component (50) is hollow or completely filled, in particular by means of the working fluid or is filled with another fluid or material.

8. Turbomachine according to one of claims 5 to 7, characterized in that the at least one flow-guiding component (50) is fixed via one or more fixing points on the housing (1) and / or on the counterholder (2) of the stationary counter ring (30) of the mechanical seal.

9. Turbomachine according to claim 8, characterized in that an internal structure and / or the one or more fixing points of the at least one flow-guiding component (50) are optimized with regard to heat dissipation, ie have good thermal conductivity in order to be able to dissipate the heat emitted by the secondary flow via the fixing points to the housing (1) and / or to the counterholder (2).

10. Turbomachine according to one of the preceding claims, characterized in that the turbomachine has no external circuit for cooling and / or flushing the mechanical seal. 11 . Turbomachine according to one of the preceding claims, characterized in that the drive component (20) is a rotating disc with viscous drag effect or a rotating bladed impeller or a rotating structure deviating therefrom for generating the necessary pressure gradient for driving a secondary flow.

12. Turbomachine according to one of the preceding claims, characterized in that the radial steps in the transition region between different contours in the region of the secondary flows are reduced, in particular a radial step in the transition region between the rings (30, 40) of the mechanical seal is minimal.

13. Turbomachine according to one of the preceding claims, characterized in that surfaces wetted by the working fluid are optimized with regard to heat exchange by means of texturing or other microscopic or macroscopic properties.

14. Turbomachine according to one of the preceding claims, characterized in that in corner or transition areas of the housing (1) and / or a counter-holder (2) of the stationary counter-ring (30) and / or in the area of the drive component (20) and / or the pre-tensioning device (7) and / or the rings (30, 40) one or more guide elements (21) are provided for flow guidance without separation.