EP3376041A1 - Return stage and radial turbo fluid energy machine - Google Patents

Abstract

The invention relates to a return stage (BFS) of a radial turbofluid energy machine (RTFEM), in particular of a radial turbocompressor (RTC), for deflecting a flow direction (FD) of a process fluid (PF) emerging from an impeller (IMP) rotating about an axis (X) from radially on the outside radially inward, comprising an annular passage (BFC) extending around the axis (X) and comprising four adjacent sections (S1, S2, S3, S4) through which flow in the direction of flow of the process fluid (PF), a first section (FIG. S1) is designed to conduct the process fluid (PF) radially outward, wherein a second section (S2) for deflecting the process fluid (PF) is formed from radially outside to radially inside, wherein a third section (S3) for conducting the process fluid ( PF) is formed radially inward, wherein a fourth section (S3) for the diversion of the process fluid (PF) is formed in the axial direction, wherein the third portion (S3 ) comprise first vanes (L1) which define flow channels (FC) of the return duct (BFC) circumferentially to each other, the return stage (BFS) having second vanes (L2) downstream of the first vanes (L1), the flow ducts (FC) of the return duct (BFC) in the circumferential direction to each other. It is proposed that the first guide vanes (L1) are arranged exclusively in the third section (S3), wherein the second guide vanes (L2) are arranged exclusively in the third section (S4).

Description

The invention relates to a recirculation stage of a radial turbofluid energy machine, in particular a radial turbocompressor, for deflecting a flow direction of a process fluid emerging from an impeller rotating about an axis from radially outside to radially inside, comprising an annular channel extending around the axis of the four adjacent adjacent flow direction wherein a first portion for guiding the process fluid is formed radially outward, wherein a second portion for deflecting the process fluid from radially outside to radially inside is formed, wherein a third portion for conducting the process fluid is formed radially inward, wherein a fourth Section is formed for redirecting the process fluid in the axial direction, wherein the third portion comprises first guide vanes, which define flow channels of the return channel in the circumferential direction to each other, the return stage downstream ts of the first vanes second vanes defining the flow channels of the return duct in the circumferential direction to each other.

In a centrifugal compressor (see FIG. 1 ), the fluid to be compressed leaves an impeller rotating about an axis in the radial direction with a significant velocity component in the circumferential direction (twist). The static aerodynamically active components following in the flow direction have the task of converting the kinetic energy supplied in the impeller into pressure. In a multi-stage single-shaft compressor, such as from the JP000244516 known, the fluid must also be passed to the next impeller. Furthermore, the flow of the swirl is to escape, so that the following impeller is flowed largely swirl-free. This object is achieved by a so-called recirculation stage, comprising a first section, which leads the process fluid radially outward, a second section which substantially corresponds to a 180 ° arc and a third section for directing the process fluid radially inward for entry into the downstream succeeding impeller. A fourth section defines a redirection of the process fluid from the radially inward flow in the axial direction to the impeller inlet of the downstream impeller.

A generic return blading is already out of the JP 11173299-A known.
Different radial Leitschaufelerstreckungen or chord lengths of adjacent vanes generic return stages are already out of the DE723824 known.

The known from the prior art arrangements are not very compact - so relatively large space - and the flow is each relatively lossy. Return stages of the prior art are also complex in manufacturing and assembly.

Based on the problem and disadvantages of the prior art, it has the object of the invention to develop a feedback stage of the type defined in such a way that a less expansive feedback stage generates a less lossy flow, which is particularly particularly low swirl and low vortex.

To achieve the object of the invention, a feedback stage of the type defined above is proposed with the additional features of the characterizing part of patent claim 1. Furthermore, the invention proposes a radial turbofluid energy machine with such a return stage.

In technical usage, it is also common to refer to only the combination of the second section with the third section as the return stage and the first section as a downstream in the flow direction Define diffuser. The fourth section is not always attributed to the feedback stage. The terminology of this document designates the four downstream sections (S1, S2, S3, S4, see figures) as the feedback stage. It should be noted that the first section can be designed freely within the scope of the invention, so that the first section with or without blades, in Meriodinalschnitt in the flow direction, for example, can be widening, constant or tapered.

In the context of the invention, geometric expressions, such as axial, tangential, radial or circumferential direction are always related to a rotational axis of an impeller of a radial turbofan energy machine, unless otherwise specified in the immediate context. The return stage according to the invention has a clear relationship to such an impeller, since the return stage extends circumferentially around the impeller downstream of the impeller outlet in a radial turbocompressor. As a rule, the feedback stage is designed to be rotationally symmetrical with respect to the axis, at least with regard to the aerodynamically relevant aspects of the boundaries of the annular space of the invention.

As a result of the first guide vanes and second guide vanes arranged one behind the other in the direction of flow, the return stage according to the invention is less bulky than a return stage which does not have the two guide vanes one behind the other. Alignment of the flow to entry into the downstream succeeding impeller is aerodynamically more efficient by means of the stepped vane design.

Aerodynamically, the invention enables a task sharing between the two rows of vanes, the first vanes and the second vanes, which is particularly efficient. The first vanes substantially deflect the flow and the second vanes substantially break the vortices forming in the first vanes. This leads to a more homogeneous inflow to the next impeller and to a middle swirl-free inflow to the next impeller.

The arrangement of the first vanes and the second vanes exclusively in the third section of the recirculation stage combines aerodynamically advantageous preparation of the process fluid to the downstream impeller after the 90 ° turn. It can be seen that the flow guidance in the third section, which is divided into two guide stages, works particularly efficiently in the swirl-free alignment of the process fluid. In addition, the arrangement of the Leitbeschaufelung exclusively in the third section is particularly easy to manufacture and easy to install. The arrangement in the third section advantageously allows for a solid attachment of the false bottom to the blade bottom and is also particularly well suited due to the relatively simple geometry of the radial feedback in the region of the third section for mounting and manufacturing the two rows of vane. The finding of the invention is, in particular, that an arrangement of guide vanes in adjacent regions increases the tendency for undesirable secondary flows due to the complexity of the further deflection of the process fluid. The multiple task separation according to the invention between multiple radial deflection (180 °, 90 ° bends), swirl relief (first vanes) and breakage of vortices (in the second vanes) forming in the first vanes is particularly aerodynamically efficient. The fact that the second guide vanes are arranged exclusively in the third section of the return stage, any vortex are broken efficiently and hardly or no new vortex generated. In this way, a largely swirl-free and eddy-free flow enters the fourth section of the return stage and can be deflected at this point unaffected by other aerodynamic measures in the axial direction for entry into the downstream impeller.

mit:

• D2: Eintrittskantendurchmesser der ersten Leitschaufeln,
• D3: Austrittskantendurchmesser der ersten Leitschaufeln.

An advantageous development of the invention provides that an outlet edge diameter of the first guide vanes in relation to an inlet edge diameter of the first guide vanes between $$\mathrm{0}.\mathrm{5}*\mathrm{D}\mathrm{2}<\mathrm{D}\mathrm{3}<\mathrm{0}.\mathrm{68}*\mathrm{D}\mathrm{2}\mathrm{lies}.$$

With:

• D2: inlet edge diameter of the first guide vanes,
• D3: outlet edge diameter of the first guide vanes.

mit
L1EA: Metallaustrittswinkel der ersten Leitschaufeln (L1) zur Radialrichtung.This arrangement proves to be particularly favorable to the achievement of swirl and vortex freedom at the exit of the return stage. Another advantageous development for the liberation of vortices and swirls provides that the first guide vanes have a metal outlet angle to the radial direction with: $$-\mathrm{5}\mathrm{°}<\mathrm{L}\mathrm{1}\mathrm{EA}<\mathrm{5}\mathrm{°}.$$

With
L1EA: Metal exit angle of the first vanes (L1) to the radial direction.

mit:

• D3: Austrittskantendurchmesser der ersten Leitschaufeln
• D4: Eintrittskantendurchmesser der zweiten Leitschaufeln.

According to a further advantageous development, the second guide vanes can be arranged in such a way that an inlet edge diameter of the second guide vanes in relation to an outlet edge diameter of the first guide vanes between $$\mathrm{0}.\mathrm{9}*\mathrm{D}\mathrm{3}<\mathrm{D}\mathrm{4}<\mathrm{D}\mathrm{3}.$$

With:

• D3: outlet edge diameter of the first guide vanes
• D4: leading edge diameter of the second vanes.

mit

• RAS: Profilsehnenlänge
• CDT: Bogenlängenabstand.

Another advantageous embodiment of the invention provides that a blade overlap of vanes is defined in each case as a quotient of a mean chord length and a mean arc distance in the circumferential direction of the mutually adjacent blades, wherein for the second vanes a coverage $$\mathrm{0}.\mathrm{8th}<\mathrm{RAS}/\mathrm{CDT}<\mathrm{1}.\mathrm{2}\mathrm{applies}.$$

With

• RAS: profile chord length
• CDT: arc length distance.

In this context, it is particularly useful if the return stage has the same number of first vanes and second vanes.

DL2A: Differenz zwischen mittleren Metalleintrittswinkel und mittleren Metallaustrittswinkel.So that the second guide vanes work particularly efficiently according to an advantageous development of the invention as a vortex breaker, it is expedient if the second guide vanes have a difference between an average metal inlet angle and average metal outlet angle, for which the following applies: $$-\mathrm{5}\mathrm{°}<\mathrm{DL}\mathrm{2}\mathrm{A}<\mathrm{5}\mathrm{°\; with}:$$

DL2A: difference between mean metal entry angle and mean metal exit angle.

Particularly preferred is the difference between the mean metal entry angle and mean metal exit angle zero. In addition, it is also advantageous if the first guide vanes and / or second guide vanes are cylindrical.
Another advantageous development of the invention provides that exactly one second guide vane is arranged downstream in the circumferential direction between the two closest first guide vanes.

A circumferentially offset second vane stage or the arrangement of the second vanes in the circumferential direction asymmetrically to the outlet edges of the first vanes leads to a reduction of the aerodynamic losses of the process fluid in the flow through the return stage.

The realignment and redirection of the process fluid downstream of the exit from an impeller to the entrance of the downstream impeller following the invention is particularly low loss and little space. The arc length circumferentially characterizing the distance between the two exit edges of adjacent first vanes is shared by the radial jet through the leading edge of the second vanes circumferentially disposed between the first two vanes in a pressure-side portion and a suction-side portion.

A particularly advantageous embodiment of the invention provides that the second guide vanes are designed and arranged such that the second guide blade arranged downstream between the two first guide vanes is arranged in the circumferential direction closer to the suction side of the adjacent first guide vane than on the pressure side of the other adjacent first vane Vane.

It has been found that the division of the arc length, which in the circumferential direction characterizes the distance between the two exit edges of adjacent first guide vanes, is particularly advantageous when the ratio of the suction-side portion to the total arc length is between 0.4 and 0.6 (0, 4 <SSD / BLD <0.6). This characteristic offset towards the suction side of a first vane, which defines the flow channel in the circumferential direction, leads to a turbulence-free and less dissolution-dependent flow, which is particularly low loss.

Figur 1

einen Längsschnitt in schematischer Darstellung durch den Strömungskanal einer Radialturbofluidenergiemaschine am Beispiel eines Einwellenverdichters,

Figur 2

ein Detail der Figur 1, das in Figur 1 mit II ausgewiesen ist,

Figur 3

einen Schnitt durch einen dritten Abschnitt der Rückführstufe gemäß dem in Figur 2 mit III-III ausgewiesenen Schnitt in einer Radialebene an der axialen Position des dritten Abschnitts.

In the following the invention with reference to a specific embodiment with reference to drawings is described in detail. Show it:

FIG. 1

a longitudinal section in a schematic representation through the flow channel of a radial turbofluid energy machine using the example of a single-shaft compressor,

FIG. 2

a detail of FIG. 1 , this in FIG. 1 with II,

FIG. 3

a section through a third portion of the return stage according to the in FIG. 2 with III-III designated section in a radial plane at the axial position of the third section.

FIG. 1 shows a schematic representation of a longitudinal section of a radial turbofluid energy machine RTFEM in the section of a flow channel for a process fluid PF. The section shows five impellers IMP, which rotate as part of a rotor R in operation about an axis X.

On this axis X all the information in this description, such as axial, radial, tangential or circumferential direction are related. The impellers IMP suck in each case the process fluid PF substantially axially and convey this accelerated radially outward. After exiting the impeller IMP, the process fluid PF enters a return stage BFS comprising a return channel BFC.

The FIG. 2 shows the feedback stage BFS and the return channel BFC in detail. The process fluid PF passes from the impeller IMP into a first section S1 of the return channel, which is designed to conduct the process fluid PF radially outward. In the downstream second section S2, the process fluid PF is deflected from a flow direction radially outward in a flow direction FD radially inward. In the following section S3, the process fluid PF is guided radially inward and then axially fed to the following impeller IMP. The deflection of the process fluid PF in the second section S2 is essentially in the form of a 180 ° arc. The deflection from a radially inward flow direction FD in the third section S3 in the axial flow direction FD takes place essentially in a 90 ° arc, which represents a fourth section S4.

Only in the third section S3 are first vanes L1 and second vanes L2 arranged. The first vanes have an entrance edge L1LE and a exit edge L1TE. The second vanes L2 have an entrance edge L2LE and an exit edge L2TE. In this preferred embodiment, the leading edge L2LE of the second vane L2 is located in a radial portion RAD downstream and at a smaller radius than the trailing edges L1TE of the first vanes L1 - this arrangement is preferred according to the invention. The scope of the invention also includes embodiments in which this radial section RAD is zero or the entry edges L2LE are located in the radial region of the first guide vanes L1.

The vanes L1, L2, a flow channel FC in the circumferential direction between two first vanes L1 is respectively defined by a pressure side PSL1 of a first vane L1 and a suction side SSL1 of another first vane L1. In a radially extending plane (drawing plane of FIG. 3 ) in the region of the axial extent of the third section S3, a connecting line CLTE can always be indicated by two outlet edges L1TE of adjacent first guide vanes L1. This connecting line CLTE extends with a radius of curvature which corresponds to the distance radius to the axis X. An arc length BLD of this connection line CLTE between the two exit edges L1TE of the adjacent first guide vanes L1 is not divided centrally by a radial jet RS through the leading edge L2LE of the second guide vane arranged circumferentially between the two first vanes L1. A first subsection of this connection line CLTE is located between the leading edge L2LE of the second vane L2 and the trailing edge L1TE of the first vane L1, which delimits the relevant flow channel FC with its suction side SSB1. This suction-side portion SSD is smaller than the corresponding adjacent pressure-side portion PSD. The ratio of the suction-side portion SSD to the entire Arc length BLD of the connecting line CLTE between the two exit edges L1TE of the first vanes L1 is between 0.4 - 0.6 (0.4 <SSD / BLD <0.6). This type of unequal distribution of the flow channel FC between the two first guide vanes L1 by means of the following guide vane L2 leads to a particularly advantageous low-loss flow through the third section S3.

The Figures 2 and 3 have different diameters for different positions of the feedback stage BFS. The first section S1 extends up to a diameter D0. The second section S2 extends in the flow direction up to a diameter D1. These two diameters are almost identical in the exemplary embodiment. The leading edge L1LE of the first vanes L1 is at a diameter D2. The trailing edge L1TE of the first vane L1 is at a diameter D3. The third section S3 extends from the diameter D1 to the diameter D6. The leading edges L2LE of the second vanes L2 are each located on a diameter D4. The exit edges L2TE of the second vanes L2 are each located on a diameter D5. The fourth section S4 following the third section S3 starts at a diameter D6.

Claims (12)

Return stage (BFS) of a radial turbofluid energy machine (RTFEM), in particular a radial turbocompressor (RTC), for deflecting a flow direction (FD) of a process fluid (PF) emerging from an impeller (IMP) rotating about an axis (X) from radially outside to radially inside .
comprising a return passage (BFC) extending annularly about the axis (X),
has four adjacent sections (S1, S2, S3, S4) which can flow in the direction of flow of the process fluid (PF),
wherein a first portion (S1) for conducting the process fluid (PF) is formed radially outward,
wherein a second section (S2) is designed to deflect the process fluid (PF) from radially outside to radially inside,
wherein a third section (S3) for the conduction of the process fluid (PF) is formed radially inward,
wherein a fourth section (S3) is designed to divert the process fluid (PF) in the axial direction,
the third section (S3) having first guide vanes (L1) which define flow channels (FC) of the return passage (BFC) in the circumferential direction to each other,
wherein the recirculation stage (BFS) has second guide vanes (L2) downstream of the first guide vanes (L1), which define flow channels (FC) of the return passage (BFC) in the circumferential direction to each other,
characterized in that
the first guide vanes (L1) are arranged exclusively in the third section (S3),
wherein the second guide vanes (L2) are arranged exclusively in the third section (S4). Feedback stage (BFS) according to claim 1,
wherein an exit edge diameter (D3) of the first guide vanes (L1) is in proportion to an entry edge diameter (D2) of the first guide vanes (L1) $$\mathrm{0}.\mathrm{5}*\mathrm{D}\mathrm{2}<\mathrm{D}\mathrm{3}<\mathrm{0}.\mathrm{68}*\mathrm{D}\mathrm{2}\mathrm{lies}.$$

With: D2: inlet edge diameter of the first guide vanes (L1) D3: outlet edge diameter of the first guide vanes (L1). Return stage (BFS) according to at least one of the preceding claims 1 or 2,
wherein the first vanes (L1) have a metal exit angle (L2EA) to the radial direction (RAD) with: $$-\mathrm{5}\mathrm{°}<\mathrm{L}\mathrm{1}\mathrm{EA}<\mathrm{5}\mathrm{°}.$$

With
L1EA: Metal exit angle of the first vanes (L1) to the radial direction (RAD). Feedback stage (BFS) according to at least one of the preceding claims 1 to 3,
wherein an entrance edge diameter (D4) of said second vanes (L2) in a ratio to an exit edge diameter (D3) of said first vanes (L1) is between $$\mathrm{0}.\mathrm{9}*\mathrm{D}\mathrm{3}<\mathrm{D}\mathrm{4}<\mathrm{D}\mathrm{3}.$$

With: D3: outlet edge diameter of the first guide vanes (L1) D4: leading edge diameter of the second vanes (L2). Return stage (BFS) according to at least one of the preceding claims 1 to 4,
wherein a blade overlap (QST) of vanes (L1, L2) is defined as a quotient of a mean chord length (RAS) and a mean arc distance (CDT) in the circumferential direction (CD) of the mutually adjacent blades, wherein for the second vanes (L2 ) an overlap $$0.\mathrm{8th}<\mathrm{RAS}/\mathrm{CDT}<1.2\mathrm{applies}.$$

With RAS: profile chord length CDT: arc length distance. Return stage (BFS) according to at least one of the preceding claims 1 to 5,
wherein the second vanes (L2) have a difference (DL2A) between a mean metal entry angle (L2IA) and mean metal exit angle (L2EA), for which: $$-\mathrm{5}\mathrm{°}<\mathrm{DL}\mathrm{2}\mathrm{A}<\mathrm{5}\mathrm{°\; with}:$$

DL2A: difference between mean metal entry angle (L2IA) and mean metal exit angle (L2EA). Return stage (BFS) according to at least one of the preceding claims 1 to 6,
wherein the return stage (BFS) has the same number of first guide vanes (L1) and second guide vanes (L2). The recirculation stage (BFS) according to at least one of the preceding claims 1 to 7, wherein exactly one second vane (L2) is arranged downstream in the circumferential direction (CD) between the two first vanes (L1). The recirculation (BFS) according to at least preceding claim 8, wherein the first guide vanes (L1) each have a concave pressure side (PSL1) and a convex suction side (SSL1) and each flow channel (FC) in the region of the first guide vanes (L1) from a pressure side (PSL1) of a first vane (L1) and a suction side (SSL1) of another adjacent first vane (L1) is defined, wherein the second vane (L2) located downstream between the two first vanes (L1) is closer in the circumferential direction (CD) the suction side (SSL1) of the other adjacent first vane (L1) is arranged. Return stage (BFS) according to at least one of the preceding claims 1 to 3, wherein an arc length in the circumferential direction of the distance (BLD) between the two exit edges (L1TE) of adjacent first guide vanes (L1) from the radial jet (RS) through the leading edge (L1LE) the second vane (L2) arranged in the circumferential direction between the two first guide vanes (L1) is divided into a pressure-side section (PSD) and a suction-side section (SSD), where: $$0.4<\mathrm{SSD}/\mathrm{BLD}<0.6\mathrm{With}$$

With SSD: section BLD: distance. The recirculation stage (BFS) according to at least one of the preceding claims 1 to 4, wherein the first guide vanes (L1) and the second guide vanes (L2) are fixedly and immovably connected to a stator (STAT). Radial turbofluid energy machine (RTFEM) with a feedback stage (BFS) according to at least one of the preceding claims 1 to 3.

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