EP4215759A1 - Diffuser for a radial turbocompressor - Google Patents

Abstract

Diffuser (3) for a radial turbocompressor, the diffuser (3) extending annularly around a central axis (2), the diffuser (3) having an inflow which, along at least a first section of the flow, ensures an at least largely radial flow by means of a process fluid is formed during operation, the diffuser (3) having stationary first guide vanes (12) which divide the diffuser (3) into individual circumferential segments at least along a radial section, the first guide vanes (12) being in the direction of flow from a first leading edge (14) to a first trailing edge (15) along a first chord length S1, the diffuser (3) having stationary second guide vanes (13) which divide the diffuser (3) into individual circumferential segments at least along a radial section , wherein the second guide vanes (13) extend in the direction of flow from a second leading edge (16) to a second trailing edge (17) along a second chord length S2, the diffuser (3) in the region of the first section on a first axial side has a first diffuser delimitation contour and on a second axial side a second diffuser delimitation contour, the first guide vanes (12) and second guide vanes (13) extending at least along part of the extension in the flow direction transversely thereto from the first diffuser delimitation contour to the second diffuser delimitation contour along a blade height extend, the first vane (12) having a first vane height H1, the second vane (13) having a second vane height H2, the second vane (13) being arranged on the first vane (12) along the vane height H2, wherein the second chord length S2 is shorter than the first chord length S1.

Description

The invention relates to a diffuser for a radial turbocompressor, the diffuser extending annularly around a central axis, the diffuser having an inflow which is formed along at least a first section of the flow for an at least largely radial flow by means of a process fluid during operation, the diffuser having standing first guide vanes which divide the diffuser into individual circumferential segments at least along a radial section, the first guide vanes dividing in the direction of the flow from a first leading edge to a first trailing edge along a first chord length S1, with the diffuser having stationary second guide vanes which divide the diffuser into individual circumferential segments at least along a radial section, with the second guide vanes extending in the direction of flow from a second leading edge to a second trailing edge along a second chord length S2, with the diffuser having a first diffuser boundary contour in the region of the first section on a first axial side and has a second diffuser delimitation contour on a second axial side, wherein the first guide vanes and second guide vanes extend at least along part of the extension in the direction of flow transversely thereto from the first diffuser delimitation contour to the second diffuser delimitation contour along a blade height, the first guide vane having a first vane height H1, the second guide vane having a second vane height H2.

In the case of centrifugal compressors, the fluid leaves the impeller radially outwards and from there reaches the diffuser, which is typically also flown through radially from the inside outwards. The diffuser according to the invention is designed with blades. With regard to the blading, a distinction is made between low-solidity diffusers [LSD] with low blade overlap (with vanes, which have a relatively large distance from each other in the circumferential direction in relation to their radial extension) and channel diffusers - also referred to as aerodynamic diffusers [AE diffusers] - distinguished.

With a combined use of ribbed guide vanes and guide vanes, which - unlike the ribbed guide vanes - extend over the entire axial duct height of the diffuser, with the ribbed guide vanes being located upstream of the other guide vanes, it is disadvantageous that the ribbed guide vanes can trigger detachment phenomena in the throughflow in the area of their axial termination in the flow duct. In addition, it is disadvantageous that the ribbed guide vanes can cause a dead water region downstream that extends over part of the channel height, so that from an axial perspective, the flow pattern through the diffuser can also become less uniform through the use of ribbed guide vanes, so that positive effects in aerodynamic terms are at least partially canceled out again.

The invention has set itself the task of providing a more uniform flow control.

The object directed towards the device is solved by patent claim 1.

The subclaims which are dependent on and refer back to patent claim 1 relate to advantageous developments of the invention.

Terms such as radial, axial, tangential or circumferential refer to the initially defined axis around which the diffuser extends annularly. In the case of a turbo compressor or a radial turbo compressor, this axis is coaxial to the axis of rotation of the rotor.

The invention understands a profile center line to be an imaginary line that extends through the center of a blade profile. Here, the blade profile is interpreted as a two-dimensional shape. The profile centerline can be constructed in this two-dimensional form, for example by connecting the centers of all inscribed circles with a line - the profile centerline.

The diffuser is defined axially by diffuser boundary contours. Here, the term "diffuser boundary contours" is not to be understood in such a way that the diffuser boundary contours always have an axial surface normal. Rather, this term is intended to mean that the diffuser boundary contours in any case have a radial extension and—even if they have a course that is inclined relative to the radial or axial—bound the diffuser in the axial direction. A further advantageous development of the invention provides that the axial distance between diffuser boundary contours widens in the radial direction.

Particularly in the case of the centrifugal turbocompressor, the diffuser is a flow-guiding component of the stator, which is located downstream of the impeller outlet. The flow speed of the process fluid is generally delayed in the diffuser, so that a pressure build-up results according to Bernoulli's laws.

In the case of the radial turbocompressor and a diffuser that extends essentially radially outwards, the diffuser effect results simply from the radial increase in the cross-sectional area through which flow occurs. A change in the diffuser channel width, which usually results from the axial extension of the clear width of the diffuser, is also of importance. In principle, the diffuser can also extend in a manner deviating from the radial direction. Most diffusers extend largely radially. The diffuser channel width is limited by provided on both sides diffuser boundary contours. In the case of a purely radially extending diffuser without axial widening, the diffuser boundary contours also run purely radially. Due to the axial suction of a centrifugal turbo compressor and the radial output of the process fluid from the impeller, a deflection from axial to radial takes place in the impeller. The impeller is usually constructed with a wheel disk that connects the impeller to the shaft with a shaft-hub connection. The side that does not have the axial suction of the impeller is referred to as the hub side. The other opposite axial side is referred to as the housing side. In the case of impellers that have a cover plate on the housing side, this side of the housing is also often referred to as the cover plate side.

The invention understands a blade height to be the extent of the blade perpendicular to the main direction of flow. If one follows a flow thread—representative of the main flow direction—through the arrangement of the invention, for example through the diffuser, then this flow thread extends essentially perpendicularly to the direction of the blade height. If this streamline extends approximately in the middle of the arrangement, it will be at approximately 50% of the blade height.

The invention understands stationary guide vanes to mean guide vanes which are firmly connected to the stator and cannot be moved relative to the rest of the stator in order to change the aerodynamic conditions during operation. These guide vanes divide the diffuser into individual circumferential segments at least along a radial section. As a rule, such a division does not take place strictly by means of guide vanes running purely radially, but rather by means of guide vanes extending obliquely to the radial. In the area of the curved entry edge, such a segmentation is not given over the entire axial channel width. However, the invention provides that at least radially in sections Guide vanes extend over the entire width of the channel, thereby separating circumferential segments from one another. The peripheral segments of claim 1 or the set of patent claims are conceptually synonymous with flow channels between the guide vanes of the diffuser, which extend essentially from radially inside to radially outside or are flown through along this direction.

The chord length is the length of the profile chord - i.e. an imaginary connecting line between the profile nose and the profile trailing edge or the leading edge of the guide vane and the trailing edge.

In order to increase the efficiency of radial compressor stages, blading is used in the radial diffuser, which, in addition to advantages, all have specific disadvantages.

So far, blading has been used which uses the full channel width of the radial diffuser over the entire blade length (full blade) or only a small part (RIB diffusers).

Both variants have advantages and disadvantages. For example, full vane diffusers cannot generally be positioned close to the impeller outlet, as this would lead to undesirable interactions between the two components. This leads to larger radial extensions and thus costs. Furthermore, the aerodynamic advantages are somewhat lower, but the aerodynamic robustness is very high. This robustness is particularly necessary when operating the stages with inlet guide vanes, through which the outflow of the impeller changes significantly in the area of application. RIB diffusers, on the other hand, can be positioned very close behind the impeller, which leads to advantages in terms of radial extension. Aerodynamic benefits are also higher when used near design conditions. However, the aerodynamic robustness is limited, which means that use with an induction vane is not advantageous.

The present proposal solves this problem by combining the advantages of both variants and minimizing the disadvantages.

By combining the two diffuser types, the respective advantages can be used and the disadvantages minimized.

By combining the two diffuser types on just one blade cascade on a very small radial extent, it is possible to minimize impeller excitation.

The properties, features and advantages of this invention described above, and the manner in which they are achieved, will become clearer and more clearly understood in connection with the following description of the exemplary embodiments, which are explained in more detail in connection with the drawings.

Identical components or components with the same function are identified with the same reference symbols.

Exemplary embodiments of the invention are described below with reference to the drawings. These are not intended to represent the exemplary embodiments to scale, rather the drawing, where useful for explanation, is in schematic and/or slightly distorted form. With regard to additions to the teachings that can be seen directly in the drawing, reference is made to the relevant state of the art.

Figur 1

Einen schematischen Längsschnitt entlang einer Drehachse durch einen Radialturboverdichter mit einem erfindungsgemäßen Diffusor

Figur 2

Eine schematische perspektivische Ansicht eines Teils des erfindungsgemäßen Diffusors

Figur 3

Eine schematische perspektivische Ansicht eines Teils des erfindungsgemäßen Diffusors

Figur 4

Eine schematische Draufsicht auf einen Teil des erfindungsgemäßen Diffusors

Show it:

figure 1

A schematic longitudinal section along an axis of rotation through a radial turbo compressor with a diffuser according to the invention

figure 2

A schematic perspective view of part of the diffuser according to the invention

figure 3

A schematic perspective view of part of the diffuser according to the invention

figure 4

A schematic plan view of part of the diffuser according to the invention

The figure 1 shows a schematic longitudinal section along an axis of rotation 2 through a radial turbocompressor 1 with a diffuser 3 according to the invention.

figure 1 shows a centrifugal turbocompressor 1 with a diffuser 3 and an impeller 4 arranged upstream of the diffuser 3. The impeller 4 and the diffuser 3 extend annularly along a circumferential direction 5 of an axis X with an axis of rotation 2. The impeller 4 is fixed in a specific axial position on a shaft 6 rotatably mounted about the axis of rotation 2 or the axis X, which is arranged coaxially with the axis of rotation ROT. The impeller 4 has a wheel disk 7 , impeller blades 8 and a cover disk 9 , the impeller blades 8 forming flow channels being fastened between the wheel disk 7 and the cover disk 9 . A process fluid is sucked in axially and deflected outwards in the radial direction, where it exits the rotating impeller 4 during operation and reaches a static diffuser 3 .

An advantageous development of the Radiaturbol compressor 1 according to the invention is given by the arrangement of an open impeller 4 without a cover plate 9. This variant is not shown separately, but the cover plate 9 - shown in figure 1 - can be taken as optional.

The process fluid flows from the diffuser 3 into a collecting spiral 10 . From there, the process fluid is fed from the radial turbocompressor 1 to units located downstream in a manner that is not shown.

The figure 2 shows a schematic perspective view of a part of the diffuser 3 according to the invention. The diffuser 3 comprises a plurality of guide vanes 11 distributed in the circumferential direction. These guide vanes 11 are distributed at equidistant intervals around the circumference.

An essential feature of the guide vane 11 is that it comprises a first guide vane 12 and a second guide vane 13 . This will be in the figure 3 explained in more detail.

The diffuser 3 extends annularly around a central axis 2 and has an inflow which is formed along at least a first section of the flow for an at least largely radial flow by means of a process fluid during operation.

The diffuser 3 has standing first guide vanes 11 which divide the diffuser 3 into individual circumferential segments at least along a radial section.

The first guide vane 11 extends in the direction of flow from a first leading edge 14 to a first trailing edge 15 along a first chord length S1.

The diffuser 3 has standing second guide vanes 13 which divide the diffuser 3 into individual circumferential segments at least along a radial section.

The second guide vane 13 extends in the direction of flow from a second leading edge 16 to a second trailing edge 17 along a first chord length S2.

In the region of the first section, the diffuser 3 has a first diffuser boundary contour on a first axial side and a second diffuser boundary contour on a second axial side, with the first guide vanes 12 and second guide vanes 13 at least along part extending in the direction of flow transversely thereto from the first diffuser boundary contour to the second diffuser boundary contour along a blade height, the first guide vane 12 having a first vane height H1, the second guide vane 13 having a second vane height H2.

The second vane 13 is disposed on the first vane 12 along the vane height H2 with the second chord length S2 being shorter than the first chord length S1.

The following applies to the first blade height H1 and the second blade height H2: H1<H2.

The following also applies: H1=a*H2, where a has a value between 0.1 and 0.5, in particular a value between 0.2 and 0.4 and very particularly a value between 0.25 and 0.35.

The following applies to the first chord length S1 and to the second chord length S2: S2<S1, where the following applies: S2=b*S1, where b assumes a value between 0.3 and 0.7, in particular a value between 0.4 and 0.6 and very particularly between 0.45 and 0.55.

The first leading edge 14 of the first guide vane 12 and the second leading edge 16 of the second guide vane 13 are formed essentially parallel to one another.

The first trailing edge 15 of the first vane 12 and the second trailing edge 17 of the second vane 13 form a common axis. This means that the trailing edges of the first guide vane 12 and the second guide vane 13 are essentially identical to one another.

The figure 4 shows a plan view of the first guide vane 12 and the second guide vane 13, the second guide vane 13 being arranged on the first guide vane 12. FIG.

The first guide blade 12 has a first profiling 18 .

The second vane 13 has a second profiling 19 .

The first profiling 18 is essentially identical to the second profiling 19, with the second profiling 19 being scaled compared to the first profiling.

Claims (9)

diffuser (3) for a radial turbo compressor, wherein the diffuser (3) extends annularly around a central axis (2), wherein the diffuser (3) has an inflow, which is designed along at least a first section of the flow for an at least largely radial flow by means of a process fluid during operation, wherein the diffuser (3) has stationary first guide vanes (12) which divide the diffuser (3) into individual circumferential segments at least along a radial section, wherein the first guide vanes (12) extend in the direction of flow from a first leading edge (14) to a first trailing edge (15) along a first chord length S1, wherein the diffuser (3) has stationary second guide vanes (13) which divide the diffuser (3) into individual circumferential segments at least along a radial section, wherein the second guide vanes (13) extend in the direction of flow from a second leading edge (16) to a second trailing edge (17) along a second chord length S2, wherein the diffuser (3) in the region of the first section has a first diffuser delimiting contour on a first axial side and a second diffuser delimiting contour on a second axial side, the first guide vanes (12) and second guide vanes (13) extending at least along part of the extension in the flow direction transversely thereto from the first diffuser delimiting contour to the second diffuser delimiting contour along a blade height, wherein the first guide vane (12) has a first vane height H1, wherein the second guide vane (13) has a second vane height H2,
characterized in that the second guide vane (13) is arranged on the first guide vane (12) along the vane height H2, the second chord length S2 being shorter than the first chord length S1. Diffuser (3) according to claim 1,
where the following applies to the first blade height H1 and the second blade height H2: H1<H2. Diffuser (3) according to claim 2,
where: H1=a*H2, where a has a value between 0.1 and 0.5, in particular a value between 0.2 and 0.4 and very particularly a value between 0.25 and 0.35. Diffuser (3) according to one of claims 1 to 3,
where the following applies to the first chord length S1 and to the second chord length S2: S2<S1, where the following applies: S2=b*S1, where b assumes a value between 0.3 and 0.7, in particular a value between 0.4 and 0.6 and very particularly between 0.45 and 0.55. Diffuser (3) according to one of the preceding claims, wherein the first leading edge (14) of the first vane (12) and the second leading edge (16) of the second vane (13) are formed substantially parallel to one another. Diffuser (3) according to one of the preceding claims, wherein the first trailing edge (15) of the first vane (12) and the second trailing edge (17) of the second vane (13) form a common axis. Diffuser (3) according to one of the preceding claims, wherein the first guide vane (12) and the second guide vane (13) are profiled. Diffuser (3) according to claim 7,
wherein the profiling of the first guide vane (12) and the profiling of the second guide vane (13) in the area of the trailing edge (15, 17) are essentially identical. Diffuser (3) according to claim 7 or 8,
wherein the profiling of the first guide vane (12) and the profiling of the second guide vane (13) are essentially identical.

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