EP3361101A1 - Return channel of a multistage compressor or expander with twisted vanes - Google Patents

Abstract

The invention relates to a recycling stage (RTC) for flowing through a process fluid along a throughflow direction of a radial turbomachine (RTM), in particular a radial turbocompressor recycling stage (RCC), wherein the recycling stage (RTC) extends annularly around an axis (X), wherein the recycling stage (RTC) is defined radially inward of an inner boundary contour (IDC) and radially outward of an outer boundary contour (ODC), wherein at least one vane stage (VST) comprising vanes (VNS) extends at least along a portion of the third portion (SG3); Segmented in the circumferential direction in flow channels, wherein in each case a profile center line (PML) of a profile cross section (PRC) of the guide vanes (VNS) of the vane stage (VST) on the inner boundary contour (IDC) an inner track (ITR) and the outer boundary contour (ODC) defines an outer track (OTR). In addition, the invention relates to a radial turbomachine (RTM), in particular a radial turbocompressor (CO) with at least one such return stage. To improve the aerodynamics, it is proposed to make the guide vanes (VNS) substantially cylindrical in a middle second profile section (PS2) and otherwise to make them three-dimensional.

Description

The invention relates to a recirculation stage for flowing through a process fluid along a throughflow direction of a radial turbomachine, in particular a radial turbocompressor recirculation stage, wherein the recirculation stage extends annularly around an axis, wherein the recirculation stage is defined radially inward by an inner boundary contour and radially outwardly by an outer boundary contour. wherein along a first flow direction, the return stage extends radially outwardly in a first portion, wherein the return stage extends in a second portion along the first flow direction arcuate deflection descriptive from radially outside to radially inside, wherein the return stage along the first flow direction in a third portion extending from radially outward to radially inward, wherein the return stage is a bend in a fourth portion along the first flow direction descriptively extending from radially inward to axially, at least one vane stage comprising vanes extending at least along a portion of the third portion and the return stage circumferentially segmented into flow channels, wherein each profile center line of a profile cross section of the vanes of the vane stage on the inner boundary contour an inner Track and defined by the outer boundary contour an outer track. In addition, the invention relates to a radial turbomachine, in particular a radial turbocompressor with at least one such feedback stage.

Radial turbomachines are known as either radial turbo compressors or radial turboexpanders. The following statements relate - unless otherwise stated - to the design as a compressor. The invention is basically just as applicable to expanders as it is to compressors a radial turboexpander relative to a radial turbocompressor essentially provides a reverse flow direction of the process fluid.

Under relaxation and deflection of a process fluid in a Radialturboexpander a conversion of the thermodynamically stored in the process fluid energy into technical work by means of drive of the impeller instead.
In radial turbo compressors, this process is reversed, these convert or store technical work in flow work, which is stored thermodynamically in the process fluid. For this purpose, impellers of the compressor generally suck a process fluid axially to an axis of rotation or obliquely to the axis of rotation with an axial velocity component and accelerate and compress this process fluid by means of the respective impeller - which is also referred to as an impeller -, the flow direction of the process fluid in the deflects radial direction. The impeller is followed by a return stage downstream of a multi-stage radial turbocompressor when at least one further impeller is provided downstream.

A multi-stage radial turbomachine means in the terminology of this invention that multiple impellers are rotatably mounted about the same axis of rotation. Here, an impeller equate to one stage of the radial turbomachine. The multistage results in the requirement that in the case of the compressor, the process fluid flowing radially out of the impeller must be guided back in the direction of the axis of rotation and can flow into the downstream impeller of the downstream stage with an axial velocity component. The flow guide, which allows this return of the process fluid is called "return stage". In the case of the expander, the component can be designed identically and is only flowed through in the reverse direction.

In addition to the return of the process fluid in the direction of the axis of rotation and the deflection of the flow direction of the process fluid in the axial direction and guide vanes are regularly provided in the return stages, which at least partially or completely neutralize an impinged in the flow of the upstream impeller twist or even a twist in the opposite direction imprint for entry to the next downstream stage.

The usual version of a return stage provides that this entire component is supported and aligned by means of a so-called intermediate floor by means of suitable supports usually in a housing or other support device. Furthermore, the return stage comprises a so-called paddle bottom, which is attached to the intermediate bottom with the already explained guide vanes to form a return channel. Through the return channel, the process fluid flows to the next impeller inlet. In this structure, the guide vanes have two functions. On the one hand, the vanes have the aerodynamic function of imparting a counterangle to the process fluid to the extent that at least the swirl from the upstream stage is largely compensated, and on the other hand, the vanes have the mechanical task of securing the blade bottom to the false floor in such a way that despite the dynamic load secure hold is guaranteed.

In the scriptures DE102014203251A1 . DE 34 303 07 A1 and EP 592 803 B1 In each case the feedback stages of a multi-stage turbo-compressor are shown. An aerodynamic view of feedback stages include the US 2010/0272564 A1 and the WO2014072288A1 ,

The prior art conventional recycle stages have several disadvantages that the invention seeks to avoid. The geometrically rather simply designed return stages are for the most part aerodynamically less adapted to the fluidic task, so that the Complex three-dimensional flow situation remains at least partially disregarded, especially on the blade height differences remain unnoticed and accordingly occur disproportionately large flow losses, which reduce the efficiency. Other solutions, especially the return stage after WO2014072288A1 provide a completely three-dimensional trained blading the feedback stage, which is technically very difficult to implement and requires a complex individual design, so that in any case results in a better efficiency than the simple geometry. In addition, there are major problems in the assembly of the return stage, since the blading is often not able due to the three-dimensional design to allow conventional fasteners between the blade bottom and intermediate floor extending through the vanes. At this point expensive special solutions may have to be used, so that such a concept has no chance on the market.

The invention has therefore taken on the task of combining the characteristics of simplified production, optimized aerodynamics and ease of assembly with each other.

To achieve the object, a return stage or a radial turbomachine according to claims 1 and 8 is proposed according to the invention. The respective dependent claims contain advantageous developments of the invention.

Basically, the recirculation stage of a radial turbomachine serves to redirect the process fluid from an upstream impeller radially outward from the radially outwardly directed flow direction and to supply it axially to the downstream downstream impeller. The terms axial, radial, tangential, circumferential direction and the like are in this case or in this document in each case based on the central axis around which the return stage extends annularly. This axis is in a radial turbomachine also the axis of rotation of a rotor or the shaft with the wheels.

The vane stage located in the recirculation stage includes vanes that circumferentially segment the annular shape of the recirculation stage into individual channels. In principle, these guide vanes may also have interruptions (split), but according to the invention are preferably designed to be continuous along the first flow direction. The vanes have profiles that can be displayed in two dimensions - accordingly unwound. A two-dimensional representation is possible, for example, when the annular channel of the return stage is cut along a circumferentially extending central surface. This sectional surface of a single vane can be unwound into a plane to a two-dimensional representation. A profile center line of the stacked profiles of the guide vanes can be generated by means of centers of inscribed circles in the profile.

In this way, a profile center line travel coordinate along the first flow direction along an average height of the respective vane can be defined. The length of the vane along this coordinate is expediently normalized to a total length of 1.

The height direction of the guide blade is presently defined as the direction which is oriented perpendicular to the flow direction - in particular to the first flow direction - and perpendicular to the circumferential direction.

The profile centerline of the vane immediately adjacent the outer limit contour of the annular channel of the recirculation stage is referred to herein as the outer track of the vane and the profile centerline of the profile profile of the vane located immediately adjacent the inner limit contour is referred to as the inner track of the vane. In this context, the outer limit contour of the return stage Also referred to as cover plate side boundary contour, because a provided with a cover disc impeller has this cover plate on the side of the outer boundary contour. The hub-side flow contour of the impeller is located opposite to the inner boundary contour of the feedback stage, so that the inner limit contour of the feedback stage can also be referred to as a hub-side boundary contour. Along the complex geometry of the recirculation stage, the inner limit contour may not always be considered to be radially inward than the outer limit contour for equal positions along a mean flow line through the recirculation stage, so that such alternative terms are convenient for better understanding.

The circumferential position angle determines the respective position in the circumferential direction of the referenced components - here substantially reference points or lines of the vanes, e.g. Points on profile center lines of certain profile cross sections. The positive course direction of the circumferential position angle is in this case selected counter to the direction of rotation of the shaft or of the rotor. The vertex of this angle coincides with the central axis. For the expert, the return stage is always connected to a fluidic task, so that a detachment of the terminology of the feedback stage of the rotational direction of the turbomachine is basically not appropriate.

• in dem ersten Profilabschnitt (PS1): $${\mathrm{\theta }}_{\mathrm{OTR}}\left(\mathrm{L}\right)\ne {\mathrm{\theta }}_{\mathrm{ITR}}\left(\mathrm{L}\right)\mathrm{und}\left({\mathrm{\theta }}_{\mathrm{OTR}}\left(\mathrm{L}\right)-{\mathrm{\theta }}_{\mathrm{ITR}}\left(\mathrm{L}\right)\right)\prime \ne \mathrm{0},$$
  
• in dem zweiten Profilabschnitt (PS2): _OTR (L) =θ_ITR (L) und (θ_OTR (L) -θ_ITR (L)) '=0,
• in dem dritten Profilabschnitt (PS3): $${\mathrm{\theta }}_{\mathrm{OTR}}\left(\mathrm{L}\right)\ne {\mathrm{\theta }}_{\mathrm{ITR}}\left(\mathrm{L}\right)\mathrm{und}\left({\mathrm{\theta }}_{\mathrm{OTR}}\left(\mathrm{L}\right)-{\mathrm{\theta }}_{\mathrm{ITR}}\left(\mathrm{L}\right)\right)\prime \ne \mathrm{0.}$$
  

The three profile sections of the vanes of the vane stage differ according to the invention from each other due to the focus of their functions. The first and the third profile section are strongly associated with an arcuate deflection of the process fluid, wherein the second profile section has less the arcuate deflection as fluidic task. All three profile sections are associated with either a delay or acceleration of the process fluid, so that also take place in this respect sophisticated superimposed aerodynamic processes. The second profile section is beyond even more preferred to serve the passage of at least one fastener for the false floor at the blade bottom. These circumstances, the invention contributes to a special degree. Advantageously, the invention homogenizes the flow over the height extent of the guide vanes, in each case for values of L in the profile sections:

• in the first profile section (PS1): $${\mathrm{\theta }}_{\mathrm{OTR}}\left(\mathrm{L}\right)\ne {\mathrm{\theta }}_{\mathrm{ITR}}\left(\mathrm{L}\right)\mathrm{and}\left({\mathrm{\theta }}_{\mathrm{OTR}}\left(\mathrm{L}\right)-{\mathrm{\theta }}_{\mathrm{ITR}}\left(\mathrm{L}\right)\right)\text{'}\ne \mathrm{0}.$$
  
• in the second profile section (PS2): _OTR (L) = θ _ITR (L) and (θ _OTR (L) -θ _ITR (L)) '= 0,
• in the third profile section (PS3): $${\mathrm{\theta }}_{\mathrm{OTR}}\left(\mathrm{L}\right)\ne {\mathrm{\theta }}_{\mathrm{ITR}}\left(\mathrm{L}\right)\mathrm{and}\left({\mathrm{\theta }}_{\mathrm{OTR}}\left(\mathrm{L}\right)-{\mathrm{\theta }}_{\mathrm{ITR}}\left(\mathrm{L}\right)\right)\text{'}\ne \mathrm{0th}$$
  

wobei in dem dritten Profilabschnitt (PS3) gilt: $${\mathrm{\theta }}_{\mathrm{OTR}}\left(\mathrm{L}\right)-{\mathrm{\theta }}_{\mathrm{ITR}}\left(\mathrm{L}\right)<\mathrm{0.}$$

Particularly expedient is a further training in which applies in the first profile section: $${\mathrm{\theta }}_{\mathrm{OTR}}\left(\mathrm{L}\right)-{\mathrm{\theta }}_{\mathrm{ITR}}\left(\mathrm{L}\right)>\mathrm{0}.$$

wherein in the third profile section (PS3): $${\mathrm{\theta }}_{\mathrm{OTR}}\left(\mathrm{L}\right)-{\mathrm{\theta }}_{\mathrm{ITR}}\left(\mathrm{L}\right)<\mathrm{0th}$$

$$\left({\mathrm{\theta }}_{\mathrm{OTR}}\left(\mathrm{L}\right)-{\mathrm{\theta }}_{\mathrm{ITR}}\left(\mathrm{L}\right)\right)\prime =\mathrm{0}\mathrm{f}\ddot{\mathrm{u}}\mathrm{r\; genau\; ein\; L\; PS}2.$$

An advantageous development of the invention provides that the following applies: $$\left({\mathrm{\theta }}_{\mathrm{OTR}}\left(\mathrm{L}\right)-{\mathrm{\theta }}_{\mathrm{ITR}}\left(\mathrm{L}\right)\right)\text{'}=\mathrm{0}\mathrm{f}\ddot{\mathrm{u}}\mathrm{exactly\; one\; <figure-callout\; id="1"\; label="L\; PS"\; filenames="imgf0004.png"\; state="\{\{state\}\}">L\; PS</figure-callout>}\mathrm{1}.$$

$$\left({\mathrm{\theta }}_{\mathrm{OTR}}\left(\mathrm{L}\right)-{\mathrm{\theta }}_{\mathrm{ITR}}\left(\mathrm{L}\right)\right)\text{'}=\mathrm{0}\mathrm{f}\ddot{\mathrm{u}}\mathrm{exactly\; one\; L\; PS}\mathrm{Second}$$

The middle, second profile section advantageously extends from at most L = 0.4 to at least L = 0.6.

For fastening the false floor to the blade bottom, it makes sense if at least some of the guide blades in the second profile section have a recess extending from a point of the inner track to a point of the outer track for passing a fastening element between the inner boundary contour and the outer boundary contour. This recess is preferably closed towards the lateral blade profile surfaces. Particularly preferably, the recess has a central straight extension axis and can be designed in particular as a bore.

The efficiency of the return stage can be further optimized if the guide vanes are each arranged with an inlet edge in each case in the second section, preferably in a region of the arcuate deflection of the second section between 0 ° -90 ° of a first deflection angle to the central axis.

In the case of the curved deflections in the return stage, the deflection angle is in each case the angular difference of a projection of the respective throughflow direction, in particular of the first throughflow direction, of the return stage in an axial-radial plane at the exit to the considered deflecting section.

A further improvement of the aerodynamics results from the fact that the guide vanes are each arranged with an exit edge in each case in the fourth section, preferably in a region of the arcuate deflection of the fourth section between 0 ° -60 ° second deflection angle to the axis.

A radial turbomachine according to the invention comprises a return stage of the type already described, wherein the axis about which the return stage extends annularly with the axis of rotation of a rotor or a shaft carrying wheels, is identical. The return stage in this case leads the flow along the first direction of flow from an impeller to a downstream impeller.

Particularly expediently, the invention makes it possible for the ratio of an intermediate diameter to an outlet diameter to be less than 1.5, in particular less than 1.4, wherein the exit diameter is the exit diameter of the impeller located upstream of the recirculation stage and the intermediate diameter is the diameter of the transition cross section of the recirculation stage from the first section to the second section.

Figur 1

ein axialer Längsschnitt durch den Ausschnitt eines Gehäuses einer Radialturbomaschine mit einer Rückführstufe und Laufrädern,

Figur 2

zeigt eine Darstellung eines Querschnitts gemäß dem in Figur 1 ausgewiesenen Schnitt II-II,

Figur 3

zeigt eine dreidimensionale Widergabe der Leitschaufelstufe einer erfindungsgemäßen Rückführstufe zusammen mit einem Zwischenboden und

Figur 4

zeigt den Umfangspositionswinkeldifferenzverlauf zwischen der äußeren Spur und der inneren Spur der Profilmittellinie einzelner Leitschaufeln der Leitschaufelstufe der Rückführstufe aufgetragen über die auf 1 (dimensionslos) normierte Profillängenlaufkoordinate entlang der ersten Strömungsrichtung.

In the following the invention with reference to a specific embodiment with reference to drawings is explained in more detail. They show schematically:

FIG. 1

an axial longitudinal section through the cutout of a housing of a radial turbomachine with a return stage and wheels,

FIG. 2

shows a representation of a cross section according to the in FIG. 1 designated section II-II,

FIG. 3

shows a three-dimensional reproduction of the vane stage of a return stage according to the invention together with an intermediate bottom and

FIG. 4

Figure 12 shows the circumferential angular position difference curve between the outer track and the inner track of the profile center line of individual vanes of the vane stage of the recirculation stage plotted against the 1 (dimensionless) normalized profile length run coordinate along the first flow direction.

FIG. 1 shows a recycling stage RC of a radial turbomachine RTM, which is designed as a radial turbocompressor CO.

The components explained here by way of example for a radial turbocompressor CO are identical in construction according to the invention as a radial turboexpander, wherein a process fluid PF flows through these components in a radial turbocompressor CO in a first flow direction FD1 and in a radial turboexpander in an opposite second flow direction FD2. The descriptions in this document always refer to the first flow direction FD1, unless stated otherwise.

FIG. 1 shows parts of two successively flowed through stages, a first stage ST1 and a second stage ST2 a partially illustrated radial turbomachine RTM or radial turbocompressor CO, wherein a feedback stage RTC between the two stages ST1, ST2 is shown here completely schematically. The two stages ST1, ST2 are shown here with wheels rotatably arranged about the rotation axis X, a first impeller IP1 and a second impeller IP2.

In the representation of FIG. 1, a process fluid PF first flows through the first impeller IP1 in an axially inflowing and radially outflowing manner along a first throughflow direction FD1. By way of example only, an oppositely directed second flow direction FD2 is also indicated, as is the case with a radial expander. Downstream of the first impeller IP1, the process fluid PF reaches a radially outwardly directed first section SG1 and is decelerated there, passes downstream into an approximately 180 ° deflection of a second section SG2 and then into a radially inward direction Returning a third section SG3 of the feedback stage RTC. Downstream of the third section SG3, the process fluid PF flows in a fourth section SG4 from radially inward into the second impeller IP2 in a direction of axial flow and is then again accelerated radially outward.

The return stage RTC comprises a blade floor RR, vanes VNS and an intermediate floor DGP. The intermediate bottom DGP is supported by means of at least one support SUP in a support device - here in a housing CAS - and positioned there. The support SUP and the supporting portion of the housing CAS are in this case designed as a tongue and groove connection form-fitting.

In a manner not shown in detail, the return stage RTC or the blade bottom RR and the intermediate bottom DGP have a parting line which extends in a common plane substantially along the axis X. Expedient for the assembly, this parting line is located in the identical part of the joint plane, such as a parting line of the housing CAS, not shown.

In principle, it is also conceivable that the rotor is divisible between two wheels or the wheels are axially displaceable to each other for the purpose of assembly, so that the return stages RTC can be formed undivided and gradually with the wheels IP1, IP2 of the rotor are mounted together before merging with a surrounding enclosure. The housing CAS can in any case be formed horizontally or vertically divided.

The conventional design of the feedback stage RTC, which in the FIG. 1 2, it is provided that the blade floor RR, the guide vanes VNS and the intermediate floor DGP are fastened to each other. In the present case this is done by means of screws SCR, which are shown simplified by dash-dotted lines. So that the screws SCR, on the one hand, adequately fasten the blade floor RR to the intermediate floor DGP and thus have to have a minimum thickness, on the other hand a sufficiently large through-hole must be provided in the guide vanes VNS, so that the profile of the guide vanes VNS must be sufficiently strong.

• einen ersten Profilabschnitt PS1,
• einen zweiten Profilabschnitt PS2,
• einen dritten Profilabschnitt PS3.

The guide vanes are divided along the first flow direction FD1 into three successive profile sections PS:

• a first profile section PS1,
• a second profile section PS2,
• a third profile section PS3.

FIG. 2 schematically shows a cross section through a radial turbomachine RTM according to the invention, as shown in the FIG. 1 with II-II. The first impeller IP1 mounted on the shaft SH is rotatably supported about the axis X along the rotational direction ROT. By way of example, the directions are marked radially horizontally and vertically. The circumferential position angle θ is positive against the rotational direction ROT. The first impeller IP1 has, by way of example, rotor blades IPB of a rotor blade stage. For a bucket IPB, the trailing edge TEI is entered. Downstream of the first impeller IP1 extends the feedback stage RTC. The feedback stage RTC has a vane stage VST, with guide vanes VNS, one of which is shown by way of example. The schematically drawn vane VNS is shown only with its leading edge LER. Overall, the shows FIG. 2 the relationship between the direction of rotation ROT of the shaft SH and the wheels IP1, IP2 and the circumferential position angle θ.

FIG. 3 shows three-dimensional parts of the feedback stage RTC, namely the vane stage VST with the vanes VNS and their three-dimensional design.

The FIG. 4 FIG. 12 shows the variation of the circumferential position angle of the outer track to the inner track plotted against the profile centerline running coordinate L which is normalized to a total length of 1. A first alternative ALT1 provides that the difference is initially positive and then drops to 0 at approx. 0.3L and remains constant there until it drops to negative at approx. 0.65LΔθ. A second alternative ALT2 provides that the circumferential position angle difference Δθ is initially positive in the region of the leading edge LER, then decreases to the negative, has a local minimum there and rises again up to a difference of 0 at approximately 0.3L. There, Δθ remains constant up to about 0.65L and then increases to positive, up to a local maximum, before dropping back into negative. In both cases is in a first profile section PS1 the circumferential position angle difference (except for a crossing point with the 0-axis) not equal to 0, as well as in the third profile section PS3. In the second profile section PS2 in the middle of the respective vane VNS, a circumferential position angle difference of 0 is constant.

Claims (9)

Return stage (RTC) for the flow through a process fluid along a flow direction of a radial turbomachine (RTM), in particular radial turbocompressor return stage (RCC),
wherein the return stage (RTC) extends annularly about an axis (X),
wherein the return stage (RTC) is defined radially inward of an inner boundary contour (IDC) and radially outward of an outer boundary contour (ODC),
wherein along a first through-flow direction (FD1) the return stage (RTC) extends radially outwardly into a first section (SG1),
wherein the return stage (RTC) extends in a second section (SG2) along the first throughflow direction (FD1) describing an arcuate deflection from radially outside to radially inside,
wherein the return stage (RTC) extends in a third section (SG3) from radially outside to radially inward along the first throughflow direction (FD1), wherein the return stage (RTC) extends along the first throughflow direction (FD1) in a fourth section (SG4) descriptively extending an arcuate deflection from radially inward to axial,
wherein at least one vane stage (VST) comprising vanes (VNS) extends at least along a portion of the third portion (SG3) and segments the recirculation stage circumferentially into flow channels,
wherein each profile center line (PML) of a profile cross section (PRC) of the guide vane (VNS) of the vane stage (VST) defines an inner track (ITR) on the inner boundary contour (IDC) and an outer track (OTR) on the outer boundary contour (ODC) .
wherein the tracks of the inner track (ITR) and outer track (OTR) are definable as: $$\mathrm{\theta }\left(\mathrm{L}\right)={\mathrm{F}}_{\mathrm{\theta }}\left(\mathrm{L}\right)$$

$$\mathrm{R}\left(\mathrm{L}\right)={\mathrm{F}}_{\mathrm{R}}\left(\mathrm{L}\right)$$

With θ: circumferential position angle in the direction of rotation of the radial turbomachine (RTM) with vertex on axis (X), L: profile centreline run coordinate along the first flow direction (FD1) along an average height of the respective guide vane (VNS) normalized to a total length 1, F _θ (L): functional relationship between circumferential position angle θ and position L on the profile center line, R: radius of position of inner track (ITR) or outer track (OTR), wherein the guide vanes (VNS) along the first flow direction (FD1) have three successive profile sections (PS): a first profile section (PS1), a second profile section (PS2), a third profile section (PS3), characterized,
that applies in each case to values of L in the profile sections: in the first profile section (PS1): $${\mathrm{\theta }}_{\mathrm{OTR}}\left(\mathrm{L}\right)\ne {\mathrm{\theta }}_{\mathrm{ITR}}\left(\mathrm{L}\right)\mathrm{and}\text{'}\left({\mathrm{\theta }}_{\mathrm{OTR}}\left(\mathrm{L}\right)-{\mathrm{\theta }}_{\mathrm{ITR}}\left(\mathrm{L}\right)\right)\text{'}\ne \mathrm{0}.$$

in the second profile section (PS2): $${\mathrm{\theta }}_{\mathrm{OTR}}\left(\mathrm{L}\right)\ne {\mathrm{\theta }}_{\mathrm{ITR}}\left(\mathrm{L}\right)\mathrm{and}\left({\mathrm{\theta }}_{\mathrm{OTR}}\left(\mathrm{L}\right)-{\mathrm{\theta }}_{\mathrm{ITR}}\left(\mathrm{L}\right)\right)\text{'}=\mathrm{0}.$$

in the third profile section (PS3): $${\mathrm{\theta }}_{\mathrm{OTR}}\left(\mathrm{L}\right)\ne {\mathrm{\theta }}_{\mathrm{ITR}}\left(\mathrm{L}\right)\mathrm{and}\left({\mathrm{\theta }}_{\mathrm{OTR}}\left(\mathrm{L}\right)-{\mathrm{\theta }}_{\mathrm{ITR}}\left(\mathrm{L}\right)\right)\text{'}\ne \mathrm{0th}$$

Feedback stage (RTC) according to claim 1,
wherein in the first profile section (PS1): $$\mathrm{\theta OTR}\left(\mathrm{L}\right)-\mathrm{\theta ITR}\left(\mathrm{L}\right)>\mathrm{0}.$$

wherein in the third profile section (PS3): $${\mathrm{\theta }}_{\mathrm{O{\rm T}R}}\left(\mathrm{L}\right)-{\mathrm{\theta }}_{\mathrm{ITR}}\left(\mathrm{L}\right)<\mathrm{0th}$$

Feedback stage (RTC) according to claim 1 or 2, wherein: $$\left({\mathrm{\theta }}_{\mathrm{OTR}}\left(\mathrm{L}\right)-{\mathrm{\theta }}_{\mathrm{ITR}}\left(\mathrm{L}\right)\right)\text{'}=\mathrm{0}\mathrm{f}\ddot{\mathrm{u}}\mathrm{exactly\; one\; L\; PS}\mathrm{1}$$

$$\left({\mathrm{\theta }}_{\mathrm{OTR}}\left(\mathrm{L}\right)-{\mathrm{\theta }}_{\mathrm{ITR}}\left(\mathrm{L}\right)\right)\text{'}=\mathrm{0}\mathrm{f}\ddot{\mathrm{u}}\mathrm{exactly\; one\; L\; PS}\mathrm{Second}$$

Feedback stage (RTC) according to claim 1, 2 or 3,
wherein the second profile section (PS2) extends from at most L = 0.4 to at least L = 0.6. Feedback stage (RTC) according to claim 1, 2, 3 or 4,
wherein at least some of the vanes (VNS) in the second tread portion (PS2) have a recess extending from a point of the inner lane to a point of the outer lane for passing a fastener between the inner limit contour (IDC) and the outer limit contour (ODC). Feedback stage (RTC) according to claim 1, 2, 3, 4 or 5,
wherein the guide vanes (VNS) are each arranged with an entry edge (VLE) respectively in the second section (SG2), preferably in a region of the arcuate deflection of the second section (SG2) between 0 ° -90 ° of a first deflection angle (BA1). Feedback stage (RTC) according to claim 1, 2, 3, 4, 5 or 6,
wherein the guide vanes (VNS) are each arranged with an exit edge (VTE) respectively in the fourth section (SG4), preferably in a region of the arcuate deflection of the fourth section (SG2) between 0 ° -60 ° of a second deflection angle (BA2). Radial turbomachine (RTM), in particular radial turbocompressor, with at least one return stage (RTC) according to claim 1, 2, 3, 4, 5, 6 or 7, wherein the radial turbomachine (RTM) has a rotor (ROT) rotatably mounted about the axis (X). comprising at least two wheels (IP1, IP2), wherein the return stage (RTC) the flow along the first flow direction (FD1) of an impeller (IP1, IP2) leads to a downstream impeller (IP1, IP2). Radial turbomachine (RTM) according to claim 8,
wherein the impellers (IP1, IP2) have an exit diameter (D2) upstream of the return stage (RTC), the transitional cross section of the return stage being disposed from the first section (SG1) to the second section (SG2) at an intermediate diameter (DRR) applies: $$\mathrm{DRR}/\mathrm{D}\mathrm{2}<\mathrm{1}.\mathrm{5}.\mathrm{especially\; DRR}/\mathrm{D}\mathrm{2}<\mathrm{1}.\mathrm{4}$$

With: D2: exit diameter impellers (IP1, IP2) DRR: intermediate diameter Transitional cross section of the return stage from the first section (SG1) to the second section (SG2).

Images