EP3577347B1 - Turbo-compressor with return flow channels - Google Patents

Description

The invention relates to a turbo compressor with a recirculation geometry for an optimized flow connection of a first and second compressor stage of the turbo compressor.

Solutions for connecting the first and second compressor stage in turbo compressors are known from the prior art, in which rotationally symmetrical return channels (also known as so-called "return channels") can be used.

They usually consist of a recirculation geometry arranged after the compressor impeller of the first compressor stage, a 180° bend, a radial nozzle usually provided with stators and a 90° deflection for entry into the area of the subsequent compressor impeller. A corresponding structure is, for example, from the publication EP 3056741 A1 or the EP 2918848 A1 famous.

US984189A discloses a turbo compressor according to the preamble of claim 1.

In the case of the turbo compressors known from the prior art, an undesired swirl occurs in the flow in the first compressor stage. In addition, the inflow into the second compressor stage is uneven. Furthermore, it is disadvantageous that in the case of low mass flows within the one rotationally symmetrical return channel provided, undesired flow separation can occur. Furthermore, the pressure loss in the return channel is comparatively high.

The invention is therefore based on the object of providing a recirculation geometry for a turbo compressor which reduces the risk of flow separation and minimizes the pressure loss.

This object is achieved by the combination of features according to claim 1.

According to the invention, a recirculation geometry of a turbo compressor is proposed, which is designed for flow connection of a first and second compressor stage of the turbo compressor. The recirculation geometry has a plurality of partial spirals which are arranged uniformly distributed in the circumferential direction and run at least partially in the circumferential direction. The word component "geometry" is included in "return geometry", but determines the resulting flow line due to the formation of the flow channels.

The plurality of flow channels reduces the flow cross section of each individual flow channel and offers a more even inflow into the second compressor stage. In addition, the maximum extent, in particular in the radial direction, of each individual channel can be increased compared to a single rotationally symmetrical return channel without large-area flow separations or backflows being observed at operating points with low mass flow.

According to the invention, it is provided that the flow channels form a plurality of elbows arranged one after the other, which repeatedly deflect the flow between the first and second compressor stages. In this way it is possible to realize an optimal axial flow against the compressor impeller of the second compressor stage from the radial outflow direction of the compressor impeller of the turbocompressor in the first compressor stage.

According to the invention is an embodiment of the recirculation geometry in which the elbows of the flow channels direct the flow from a radial outflow direction first into a first axial direction in the direction of the second compressor stage and then back into a radial inflow direction, which runs counter to the outflow direction. Even more advantageous is the design in which the last elbow of the flow channels, viewed in the flow direction, then directs the flow to the inflow direction in a second axial direction, which runs counter to the first axial direction. The second axial direction corresponds to the intake direction of the compressor impeller of the second compressor stage, so that a predefined inflow exactly to the intake area via the flow channels of the compressor impeller of the second compressor stage can take place. The bends each produce an essentially 90° deflection.

Depending on the design of the turbo compressor, the compressor impeller of the second compressor stage can be arranged in the same direction as the compressor impeller of the previous compressor stage, i.e. the direction of entry is the same for both compressor impellers. Likewise, both compressor impellers can also be arranged in opposite directions, i.e. in a so-called back-to-back arrangement, which is mainly useful for two-stage turbo compressors, with the outflow geometry of the second compressor stage, which is designed as a spiral, for example, and the subsequent outlet pipe passing through the area between the individual Partial spirals of the return geometry can be performed. In principle, the invention is not limited to two-stage turbo compressors, but can also be applied to multi-stage designs.

In a further development of the recirculation geometry, it is provided that the flow channels of the partial spirals extend from an inlet area of the first compressor stage, in particular from the outlet area of the impeller of the first compressor stage, to an outlet area of the first compressor stage, in particular to the inlet area of the impeller of the second compressor stage, and in the Combine the outlet area to form a circumferentially symmetrical overall channel. The overall channel then forms the inflow for or into the second compressor stage. This functions particularly advantageously in an embodiment in which the flow channels combine to form the overall channel after the last elbow, viewed in the direction of flow, which directs the flow in the second axial direction.

Furthermore, an exemplary embodiment of the return geometry is characterized in that the individual flow channels each have curved walls and/or curved twist struts in a transition to the overall channel exhibit. The swirl struts are designed to impart a predefined swirl to the flow as it enters the overall channel, which effectively promotes intake through the compressor wheel of the second compressor stage.

To support the flow deflection, the return geometry is designed according to the invention in such a way that the elbow formed in the flow channels, which deflects the flow from the radial outflow direction into the first axial direction in the direction of the second compressor stage, has a guide strut, which extends along the respective flow channel in Extends radially outward and in the first axial direction. In an advantageous embodiment, the guide struts divide the respective flow channel in the middle, so that both remaining parts of the respective flow channel are flown through with the same large mass flow. It is also provided in a development that the guide struts extend radially outside of a tongue radius of the return geometry, i.e. at a distance radially outwards from an inlet of the respective flow channel formed by the tongue radius.

In terms of flow technology, the return geometry is also provided according to the invention, in which the flow channels have an axial section in which the flow is directed in the first axial direction in the direction of the second compressor stage, and the axial section of the flow channels is designed as a diffuser. By designing the respective axial section as a diffuser, the flow is decelerated, friction losses are reduced and static pressure is built up. The axial section of the recirculation geometry advantageously runs parallel to an axis of rotation of the turbo compressor.

Furthermore, an embodiment of the recirculation geometry is favorable in which the flow channels can be assigned to one of the first compressor stage Inflow radial section and an outflow radial section that can be assigned to the second compressor stage, which direct the flow in each case in the inflow direction or in the outflow direction, before the flow fluid preferably flows out axially from the return geometry. In terms of flow, the embodiment is advantageous in which the flow channels in the outflow radial section widen in terms of their cross section in the direction of flow, so that an acceleration of the flow in the outflow radial section is reduced or even avoided.

The flow channels of the partial spirals of the recirculation geometry are formed in a compact design by an intermediate disk housing of the turbo compressor, which separates the first compressor stage from the second compressor stage. The flow channels may extend in the outer peripheral surface of the washer housing. In a further development, the flow channels of the partial spirals are formed by the intermediate disk housing and the turbo compressor housing, the flow channels being formed by a channel free space between an outer surface of the intermediate disk housing and an inner wall surface of the turbo compressor housing. For example, the flow channels run in the outer peripheral surface of the washer housing and are covered by the turbo compressor housing. In alternative designs, the turbo compressor housing and the intermediate disk housing can also be designed in multiple parts.

A development of the return geometry provides that the intermediate disk housing has an axial opening for receiving the compressor impeller of the first compressor stage with an axial opening radius R1 and the flow channels of the partial spirals extend from the tongue radius R2 of the intermediate disk housing. The tongue radius is set to be 1.4 - 1.8 times larger than the axial opening radius R1. A further enlargement would increase the risk of a salvage flow separation to be avoided.

In an embodiment variant of the return geometry, the partial spirals extend radially outwards at the inlet of the flow channels determined by the tongue radius R2 at an angle a3=60°-80° relative to a radial plane in the circumferential direction. The outflow direction of the compressor impeller of the first compressor stage and the inflow direction into the flow channels can thus be matched to one another with regard to the outflow angle and inflow angle.

With regard to the size of the flow channels of the return geometry, an advantageous embodiment provides that the ratio of the extension (a1) of the flow channels of the partial spirals in the circumferential direction to adjacent circumferential sections (a2) without flow channels is formed, so that 0.2 ≤ a1/(a1 +a2) ≤ 0.5.

Fig. 1

eine schematische Ansicht eines Turboverdichters;

Fig. 2

eine Explosionsdarstellung der Teile des Turboverdichters aus Fig. 1;

Fig. 3

eine Draufsicht auf ein Zwischenscheibengehäuse aus Fig. 2 mit Teilspiralen, welche die Strömungskanäle bilden;

Fig. 4

eine einlassseitige Draufsicht auf eine schematisch dargestellte, sich durch einen Strömungsverlauf ergebende Strömungsgeometrie;

Fig. 5

eine seitliche Schnittansicht der Strömungsgeometrie aus Fig. 4;

Fig. 6

eine rückseitige Draufsicht der Strömungsgeometrie aus Fig. 4;

Fig. 7

eine Seitenansicht der Strömungsgeometrie aus Fig. 4.

Other advantageous developments of the invention are characterized in the dependent claims or are presented in more detail below together with the description of the preferred embodiment of the invention with reference to the figures. Show it:

1

a schematic view of a turbo compressor;

2

an exploded view of the parts of the turbo compressor 1 ;

3

Figure 12 shows a plan view of a washer housing 2 with partial spirals, which form the flow channels;

4

an inlet-side top view of a schematically illustrated flow geometry resulting from a flow path;

figure 5

a side sectional view of the flow geometry 4 ;

6

a rear plan view of the flow geometry 4 ;

7

a side view of the flow geometry 4 .

The figures are schematic examples and serve for a better understanding of the invention. Like reference characters identify like parts throughout the several views.

In figure 1 a turbo compressor 1 is shown schematically with a turbo compressor housing 3 and an intermediate disc housing 2 accommodated therein. A compressor impeller 6 of the first compressor stage is arranged on the intermediate disc housing 2 at the flow inlet 4, partially inserted into an axial opening, which sucks in a flow fluid axially and blows it out radially in the direction of the second compressor stage. In the intermediate disc housing 2, the compressor impeller 7 of the second compressor stage is arranged axially separated from the compressor impeller 6, which also sucks in the flow fluid axially and blows it out radially in the direction of the outlet 11 of the intermediate disc housing 2 and finally the outlet 12 on the turbo compressor housing 3.

The turbo compressor housing 3 and the intermediate disk housing 2 provide a recirculation geometry for the flow connection of the first and second compressor stages with several partial spirals arranged evenly distributed in the circumferential direction, the flow channels running separately from one another 5 for establishing the flow connection from the inlet area of the first compressor stage to the outlet area of the second compressor stage, as shown in the exploded view according to FIG figure 2 and 3 can be seen. The flow channels 5 are each created by a channel free space between the outer surface of the intermediate disk housing 2 and the inner wall surface of the turbo compressor housing 3. The geometry of the respective flow channels 5 can be determined by both components or, for example, only by the intermediate disk housing 2, as in the case shown.

In the in the figures 2 and 3 In the illustrated embodiment, the recirculation geometry for the flow connection of the first and second compressor stage is generated by seven partial spirals, each with identical flow channels 5, which extend radially outwards from the flow inlet 4 and at the same time in the circumferential direction. The flow is deflected multiple times by the manifolds 15, 16 provided in the flow channels 5, namely through the first manifold 15 from a substantially radial outflow direction into a first axial direction in the direction of the second compressor stage and then through the second manifold 16 back into the radial direction Inflow direction, which runs counter to the outflow direction. The third elbow of the flow channels 5 is located within the intermediate disc housing 2 and is therefore not visible, but then directs the flow to the inflow direction in a second axial direction, which runs counter to the first axial direction.

A guide strut 8 is provided in each of the flow channels 5, which extends in the radial and axial direction over the first bend 15 and divides the flow fluid in the respective flow channel 5 centrally during the first deflection.

The geometric design of the flow connection of the return geometry is in the Figures 4 - 7 shown based on the resulting flow geometry, ie in the Figures 4 - 7 No components are shown, but rather the geometric shape of the freely flowable recirculation geometry resulting from the structure of the turbo compressor housing 3 and in particular the intermediate disk housing 2 and consequently the resulting flow from the first to the second compressor stage. Therefore, the shape of the flow channels 5 representing flow in the Figures 4 - 7 marked 5'. The geometric shape of the intermediate disk housing 2 is designed in such a way that the flow channels 5 extend from the inlet area with the flow inlet 4 of the first compressor stage to the outlet area of the first compressor stage and in the outlet area to form a circumferentially symmetrical overall channel 9 with a radius R9 and a central section through which there is no flow extend the axis of rotation with a radius R10.

The return geometry is divided into a number n flow channels 5 (in the present case n=7) each with a circumferential extension a1, the intermediate areas without flow channels are marked with a2. The ratio a1/(a1+2) is set in a range of 0.2-0.5. In the exemplary embodiment shown, all flow channels 5 have the same size and the same flow cross section, but they can also be designed differently from one another, so that, for example, the length a1 of each flow channel or some flow channels 5 varies, so that a1 ₁ +a2 ₁ ≠a1 ₂ + would apply a2 ₂ .

The individual flow channels 5 each have curved twist struts in the transition to the overall channel 9, which impart a twist to the flow as it enters the overall channel 9, so that the flow at the outlet into the second compressor stage has a predefined twist. The twist struts are as a negative in the in 7 indicated flow with the reference numeral 22 'and have an opening angle a5.

The flow channels 5 are designed as diffusers in their axial section z, in which the flow is directed in the first axial direction in the direction of the second compressor stage, and have a diffuser angle a4, the condition [R5(z) ² -R4(z) ² ] (a1 π n)/360 ≤ 2 π R2 b2 is satisfied. R5 is the outer radius as a function of the axial coordinate z, R4 is the radius of the inner wall of the flow channel 5 as a function of the axial coordinate z, R2 is the tongue radius or outlet radius of the return geometry and b2 is the flow channel width in the outflow radial section. The diffusion ratio R2/R1 is set in a range of 1.4-1.8. Following the tongue radius R2 are the partial spirals of the flow channels 5 with a tongue angle a3 between 60° and 80° with the tongue radius R11 and the smallest flow-through area 27 at the inlet the smallest flow-through area in the respective flow channel 5 is not further narrowed. The diffuser angle is formed in section z2 of the axial section z, which defines part of the straight axial extension z1. The flow channel width b2 in the radial outflow direction section is smaller than the flow channel widths b6 and b7 in the opposite radial inflow direction section.

The radial deflection and merging of the flow 5' is designed in such a way that the flow velocities are changed as little as possible or not at all. In the exemplary embodiment shown, the condition is therefore met that b6*R6*a1/360*n=b7*R7. Where b6 is the flow channel width adjacent to the second bend 16 at radius R6 and b7 is the flow channel width immediately before the third bend at radius R7, according to FIG figure 6 .

Claims (12)

1. A turbocompressor (1) of radial design having a return geometry for fluidically connecting a first and a second compressor stage of the turbocompressor (1), wherein the return geometry comprises multiple partial helices which are arranged evenly or unevenly distributed in the circumferential direction and extend at least in part in the circumferential direction and which form flow channels (5) extending at least in some sections separately from each other for fluidically connecting the first and second compressor stages, wherein the flow channels (5) form multiple successively arranged bends (15, 16) which multiply deflect the flow between the first and second compressor stages, wherein the bends of the flow channels (5) guide the flow from a radial outflow direction into a first axial direction in the direction of the second compressor stage and subsequently back into a radial inflow direction which runs counter to the outflow direction, wherein the flow channels (5) in which the flow is guided into the first axial direction in the direction of the second compressor stage, have an axial section, wherein the axial section of the flow channels (5) is designed as a diffuser, characterized in that the bend (15) formed in each case in the flow channels (5), which deflects the flow from the radial outflow direction into the first axial direction in the direction of the second compressor stage, in each case has a guide strut (8) which extends along the respective flow channel in radial direction outward and into the first axial direction.
2. The turbocompressor (1) according to Claim 1, characterized in that, subsequently to the inflow direction, one of the bends of the flow channels (5) guides the flow into a second axial direction which runs counter to the first axial direction.
3. The turbocompressor (1) according to any one of the preceding claims, characterized in that the flow channels (5) extend from an inlet region which can be associated with the first compressor stage to an outlet region which can be associated with the first compressor stage and merge in the outlet region to form a circumferentially symmetrical overall channel (9).
4. The turbocompressor (1) according to the preceding Claims 2 and 3, characterized in that, after the bend which guides the flow into the second axial direction, the flow channels (5) merge in flow direction to form the overall channel (9).
5. The turbocompressor (1) according to the preceding claim, characterized in that, in a transition to the overall channel (9), the individual flow channels (5) in each case have curved walls or curved vortex struts, which are designed to impart a vortex to the flow as it enters the overall channel (9), so that the flow at the outlet into the second compressor stage has a predefined vortex.
6. The turbocompressor (1) according to any one of the preceding Claims 1 to 5, characterized in that the flow channels (5) have an inflow radial section which can be associated with the first compressor stage and an outflow radial section which can be associated with the second compressor stage, which guide the flow into the inflow direction and into the outflow direction, wherein the flow channels (5) in the outflow radial section broaden with respect to their cross section in the flow direction.
7. The turbocompressor (1) according to any one of the preceding claims, characterized in that it is formed by a spacer housing (2) of a turbocompressor (1) which separates the first compressor stage from the second compressor stage.
8. The turbocompressor (1) according to the preceding claim, characterized in that the flow channels (5) of the partial helices are formed by the spacer housing (2) and a turbocompressor (3) housing, wherein the flow channels (5) are formed by a channel clearance between an outer surface of the spacer housing (2) and an inner wall surface of the turbocompressor housing (3).
9. The turbocompressor (1) according to any one of the preceding two claims, characterized in that the spacer housing (2) has an axial opening for receiving the compressor impeller of the first compressor stage with an axial opening radius R1, and the flow channels (5) of the partial helices extend starting from a tongue radius R2 of the spacer housing (2), wherein the tongue radius is greater than the axial opening radius R1 by the factor of 1.4-1.8.
10. The turbocompressor (1) according to the preceding claim, characterized in that the partial helices extend radially outward in the circumferential direction at an inlet of the flow channels (5), which is determined by the tongue radius R2, at an angle a3 = 60° - 80° with respect to a radial plane.
11. The turbocompressor (1) according to any one of the preceding two claims, characterized in that a ratio of the extension (a1) of the flow channels (5) of the partial helices in circumferential direction with respect to adjoining circumferential sections (a2) without flow channels is formed so that 0.2 ≤ a1/(a1+a2) ≤ 0.5.
12. The turbocompressor (1) according to any one of the preceding claims, characterized in that at least two of the flow channels (5) for fluidically connecting the first and second compressor stages have a different overall flow cross section.

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