EP3205883A1 - Rotor for a centrifugal turbocompressor - Google Patents

Abstract

The invention relates to an impeller (IMP) of a turbocompressor (TCO), for rotation about an axis (X), comprising an inlet cross-section (IN) for substantially axial inflow of a process fluid (PF) into the impeller (IMP), comprising an outlet cross-section (IMP). EX) for the substantially radial exit of the process fluid (PF) from the impeller (IMP), comprising a wheel disc (HW), which defines a hub-side deflection contour from the axial flow direction in the radial flow direction, comprising blades attached to the wheel disc (HW) ( B) defining flow channels (FC) through the impeller (IMP) over at least a portion of the flow path of the process fluid (PF), each blade (B) extending in the direction of flow at an extension end edge (IE) proximal to the wheel disc (HW) defined inside track (IT), wherein each blade (B) defines a linear outer track, wherein a relative blade length (BLL) for each position on a track (T) which is an inside track (IT) or outside track (OT), respectively defined as a proportion of the blade length located downstream of this position to the entire blade length of the relevant track (T), namely inside track (IT) or outside track (OT ), wherein a meridional angle (MA) for each position of a track (T) is defined as the upstream trapped angle between a meridional plane (MPL) through that position and a tangent to the track (T). So that the flow with improved efficiency largely free of detachment passes the impeller, it is proposed that a local extremum of the meridional angle (MA) of the inner track (IT) is present.

Description

The invention relates to an impeller of a turbocompressor, for rotation about an axis, comprising an inlet cross section for substantially axial inflow of a process fluid into the impeller, comprising an outlet cross section for substantially radial outlet of the process fluid from the impeller, comprising a wheel disc having a hub-side Umlenkkontur from the axial flow direction to the radial flow direction, comprising paddles attached to the wheel disc defining flow channels from an entrance edge to a circumferential exit edge over at least a portion of the process fluid flow path through the impeller, each paddle at a tip end extension end proximate the wheel disc a line-like inner track extending in the flow direction is defined, such that on both sides the inner track has orthogonal equal distances to a blade surface on a pressure side or a suction side of the blade v Orliegen, wherein the blade at a distal end to the wheel distal end defines a linear outer track extending in the flow direction, such that on both sides of the outer track orthogonal equidistant to the blade surface on the pressure side and the suction side of the blade, with a relative blade length for each position on a lane, which is an inside lane or outside lane, respectively defined as the proportion of blade length downstream of that position to the entire blade length of the particular lane, namely inside lane or outside lane, wherein a meridional angle for each position of a lane is defined as the upstream included angle between a meridional plane through this position and a tangent to the track.

Generic turbocompressors are already out of the DE 10 2013 207 220 B3 known. This turbo compressor type is also referred to as a centrifugal compressor, because the conveyed process fluid is accelerated radially outward in the impeller as a result of centrifugal forces. In principle, mechanical energy is added to the gas or the process fluid for the purpose of compaction by means of a rotating blading of the impeller. The aspirated process fluid is delayed within the flow channels of the impeller formed between the individual blades relative to the movement of the impeller and thus compressed according to the physical laws of fluid mechanics to a higher pressure level. Since the impeller is moving at a high speed, the fluid is further retarded after flowing out of the impeller in the radial direction in a subsequent diffuser and additionally compressed in this way according to the laws of Bernoulli.

In such fluid energy machines inevitable fluid mechanical losses always occur. The reduction of these losses is an optimization problem, in the processing of which care is taken that, in particular, no separation of the flow from the blade or other impeller surfaces occurs. The result of this optimization task is generally described with regard to the blade in a so-called angular distribution and thickness distribution over the run length of the blade on the wheel and cover disk. These two-dimensional profiles on the wheel and cover plate are geometrically connected, for example by means of straight lines, which are also referred to as "straight line". The resulting three-dimensional figure can be produced by the flank milling method. In order to avoid that such a design effort for each only slightly different compression task must be fully processed, such a blade is initially designed geometrically larger than this is usually used. This, beyond the boundaries of the leading edge, trailing edge, wheel disc and cover disc outgoing 3-dimensional figure consisting of a pressure side and a suction side is referred to as a definition surface. For the purpose of order processing, this definition surface of the blade is used, which by means of the angular distribution at the Wheel disc and the cover plate and the blade thickness distribution is described. Within certain limits, partial surfaces are extracted from this definition surface, depending on the wheel disc and cover disc geometry, and used in an individual impeller design.

Geometrical indications, such as axial, radial, tangential or circumferential direction always refer to a rotational axis of the impeller, unless the reference is otherwise stated.

The invention has set itself the task of developing an impeller for a turbocompressor such that the efficiency over conventional wheels for the same purpose is improved.

To achieve the object according to the invention, it is proposed that a local extremum of the meridional angle of the inner track is present in the range between 10% and 90% of the relative blade length.

It has been found that the advantageous geometry of the blades of an impeller recognized by the invention leads to a particularly good efficiency, because in particular only a small separation compared to conventional geometries of the process fluid in the operation of the impeller surfaces.

The definition of relative blade lengths chosen by the invention allows for the inclusion of positions of the inner track and the outer track with respect to the respective relative distances to the leading edge and trailing edge.

Basically, the invention provides an advantageous geometry of wheels both for so-called closed wheels (wheels with a cover plate) and for so-called open wheels, which have no cover plate. The preferred embodiment of the invention are impellers with a Cover disc, which defines the flow channels adjacent to the extension end edges of the blades and is attached to the blades in the region of the end extension edges of the blades. The designs that are made here for closed wheels and partially relate to a cover plate, also apply to open wheels that have no cover plate. In this case, the linear inner track extends along an end face of the blades that is distal from the wheel disc between the leading edge and the trailing edge. During operation, the open flow channels of the open impeller border on a stator contour, sealing the openings distal to the wheel disc, so that the fluidic boundary conditions are similar for purposes of the invention.

The geometry according to the invention is particularly advantageous if the course of the meridional angle is monotonically decreasing between 10% and 90% of the relative blade length of the outer track. The findings of the invention indicate that the efficiency of the impeller can be increased if, in contrast to the inner track, the outer track has no local extremum in the angular course along the relative blade length.

An advantageous development of the invention provides that in the range between 10% and 90% of the relative blade lengths, the maximum difference between the inner track and the outer track for a specific position along the relative blade lengths of the meridional angle between 10 ° and 25 °. Here, it is the special finding of the invention that the meridional angle distribution on the inner track and the outer track differ significantly. The maximum difference in this context does not mean the highest possible difference, but the highest actually occurring difference. The invention thus provides in this advantageous development that an actual maximum difference occurs, which is between 10 ° and 25 ° between the inner track. Particularly advantageous is the fluidic Efficiency when the location of the maximum difference between the inner and outer tracks is between 15% and 45% of the relative blade length.

Another advantageous development of the invention provides that the trailing edge of the blades is not inclined with respect to a meridional plane. Accordingly, it is proposed that the trailing edge of the blade enclose an angle with a meridional plane between 0 ° to 5 °. The target specification that the trailing edge of the blade lies in a meridional plane is also referred to in the professional world as rake = 0.

An advantageous development of the invention provides that the blade inlet edge forms an angle between 35 ° to 45 °, preferably 41 ° with a radial plane. The leading edge of the blade is accordingly set back slightly with respect to the inflow into the impeller.

A particularly advantageous embodiment of the invention provides that in the range between 10% to 90% of the relative blade length, the course of the meridional angle of the inner track has a turning point between 40% to 80% of the relative blade length. The geometry recognized as advantageous in this manner contributes to a further improvement in the efficiency of the fluid mechanics on the blade of the impeller according to the invention.

It has been found that, in the range between 10% and 90% of the relative blade length, the profile of a blade thickness distribution of the inner track in the direction of flow should preferably be monotonically increasing. In a further advantageous development, the blade thickness distribution on the outer track can be selected substantially constant.

Figur 1

eine Sicht auf ein erfindungsgemäßes Laufrad mit teilweise geschnittener Deckscheibe in axialer Richtung,

Figur 2

einen Meridionalschnitt entlang der Rotationsachse durch eine schematische Darstellung eines Laufrades gemäß dem Schnitt II-II in Figur 1,

Figur 3

in synoptischer Wiedergabe eine Meridionalwinkelverteilung entlang der relativen Schaufellänge sowie der Veränderung des Meridionalwinkels entlang der relativen Schaufellänge.

Figur 4

eine Schaufeldickenverteilung entlang der relativen Schaufellänge.

Figur 5

eine Detaildarstellung einer Eintrittskante als schematischer Umfangstangentialschnitt aus radialer Sicht.

In the following the invention with reference to a specific embodiment with reference to drawings and diagrams is illustrated in more detail. Show it:

FIG. 1

a view of an inventive impeller with partially cut cover plate in the axial direction,

FIG. 2

a Meridionalschnitt along the axis of rotation by a schematic representation of an impeller according to the section II-II in FIG. 1 .

FIG. 3

in synoptic representation a meridional angle distribution along the relative blade length and the change of the meridional angle along the relative blade length.

FIG. 4

a blade thickness distribution along the relative blade length.

FIG. 5

a detailed representation of an entrance edge as a schematic Umfangstangentialschnitt from a radial perspective.

FIG. 1 shows an axial plan view of an inventive impeller IMP, comprising a cover plate COV, blades B and a wheel disc HW. In the middle of the wheel disc HW the axis of rotation X is indicated, around which the impeller rotates in operation along a direction of rotation ROT. In a radial direction, in principle, a meridional section II-II along a meridional plane MPL is given, which in FIG. 2 is reproduced. The individual blades B each have a pressure side PRS and a suction side SCS. In the in FIG. 1 shown axial plan view shows the viewer the leading edge LE of the blade B. Where the cover disc COV in FIG. 1 is cut away, an outer trace OT dash-dotted lines at the outer end edge OE of the bucket B is reproduced. Directly on the wheel disc HW at the inner extension end edge IE, which is located proximal to the wheel disc HW, an inner track IT is also shown in phantom. These facts can also be at the FIG. 2 comprehend. Each vane B has a line-like inner track IT extending in the direction of flow at an extension end edge IE which is proximal to the wheel disc HW such that orthogonal distances to a vane surface on the pressure side PRS or the suction side SCS of the vane B are present on both sides of the inner track. Each blade B has at a distance to the wheel HW distal end edge OE extending in the flow direction linear outer track, such that on both sides of the outer track orthogonal equal distances to the blade surface on the pressure side PRS and the suction side SCS are present. These corresponding inner and outer tracks on the blades can also be defined such that these tracks are respectively the set of centers of circles inscribed in the blade profiles.

The FIG. 3 shows in each case as a function of the relative blade length BLL in the upper diagram area the course of the meridional angle for the inner lane IT and the outer lane OT and in the lower diagram area the derivative of the meridional angle MA 'to the relative blade length BL for the inner lane IT and the outer lane OT.

The blade leading edge LE here forms an angle LEA of 41 ° with a radial plane RP. The leading edge of the blade B is accordingly set back slightly.

The diagram of FIG. 4 shows the blade thickness distribution as a course over the relative blade length BLL for the inner track IT and the outer track OT.

In this case, it should be noted that deviating from this course, a widening of the inlet edges and outlet edges of the blades is designed. By way of example, FIG. 5 shows details of such a sharpening at an entry edge of a wheel disc or cover disk in a schematic Circumferential tangential section from radial view. The example shown there is dimensioned in such a way: parameter wheel disc cover disc SDS 2.42 mm SRS 3.73 mm LZ 11.2 mm 12.0 mm LU 4.7 mm 2.5 mm SU 3.1 mm 1.8 mm Where:
SDS: blade thickness cover disc COV,
SRS: Vane thickness wheel disc HW
LZ: length of the increase
LU: transition thickness
SU: Transition length.

These parameters are scalable so that application to other blade thicknesses is possible.

The diagrams of Figures 3 and 4 each show a course that is continued on both sides beyond the 0% or 100% position of the relative blade length BLL. This is a definition surface that is bounded in the concrete impeller by the inner and outer extension end edge OE, IE, the leading edge LE and the trailing edge TE of the blade B, respectively. The findings according to the invention on the distribution of the meridional angle MA for a blade B, also in conjunction with the blade thickness distribution for the inner track IT and the outer track OT, apply essentially independently of the section of this definition surface, provided that certain limits are not exceeded. Within limits, an extrapolation of this area can also take place. The description of the blades B by means of the distribution of the meridional angle MA and the thickness distribution over the extension of the blades B in the direction of flow and the relative blade length BLL results in a connection of the inner track and the outer track by means of the thickness distribution spanned blade profiles by means of straight lines to a three-dimensional surface in the room, which can be produced by means of a flank milling process. In principle, the three-dimensional blade spanned by the so-called regular straight line between the outer and inner blade profiles is basically preferred, although a geometry other than a straight line is also conceivable according to the invention, for example an arc defined by means of a polygon or splines and support points.

• V: Volumenstrom in Kubikmeter pro Sekunde
• U: Umfangsgeschwindigkeit in Meter pro Sekunde
• d₂: Laufraddurchmesser in Meter.

So that this so-defined general area, which is also referred to as a definition area or also as a maximum area, can be used for different compaction tasks or impellers IMP, partial areas are extracted from this definition area by means of meridional sections for the purpose of use in an impeller design. The definition surface according to the invention is suitable for a range of application of the specific flow rate Ψ = V / u * d ₂ ² between 0.05 and 0.16, where:

• V: Volume flow in cubic meters per second
• U: peripheral speed in meters per second
• d ₂ : impeller diameter in meters.

The inventive design of the blade B of an impeller IMP looks after FIG. 3 in that between about 10% to 60% of the relative blade length BLL there is a local extreme LEX of the meridional angle MA of the inner track IT. Preferably, this local extremum LEX is between 25% to 45% of the relative blade length BLL. Particularly preferred is - as in FIG. 3 , the first diagram shown - the course of the meridional angle MA for the outer track OT monotonically decreasing between 10% to 90% of the relative blade length. Furthermore, there is a difference in the meridional angle MA between the inner track IT and the outer track OT, which increases to a maximum difference DLTM along the relative blade length, this actual maximum difference, between 10 ° and 25 °. Particularly preferably, this maximum difference DLTM occurs in the range between 15% to 45% of the relative blade length BLL. Particularly preferably, the inner track IT and the outer track OT in the region of the trailing edge TE - ie at 100% of the relative blade length BLL - the same meridional angle MA. It follows that the average extent of the trailing edge TE of the blade B forms an angle with a meridional plane MPL of approximately 0 ° or is parallel to this meridional plane MPL. Preferably, this angular deviation from the meridional plane MPL of the trailing edge TE should be less than 5 °. A further particularly preferred embodiment of the invention shown in the exemplary embodiment provides that the course of the meridional angle MA of the inner track IT has a point of inflection TP in the range between 40% and 80% of the relative blade length BLL.

Claims (10)

Impeller (IMP) of a turbocompressor (TCO), for rotation about an axis (X), comprising an inlet cross-section (IN) for substantially axial inflow of a process fluid (PF) into the impeller (IMP),
comprising an outlet cross-section (EX) for the substantially radial outlet of the process fluid (PF) from the impeller (IMP),
comprising a wheel disc (HW), which defines a hub-side deflection contour from the axial flow direction in the radial flow direction,
comprising vanes (B) mounted on the wheel disc (H) which at least over part of the flow path of the process fluid (PF) through the impeller (IMP) flow channels (FC) from an inlet edge (LE) to an outlet edge (TE) in the circumferential direction define,
wherein each blade (B) at a to the wheel disc (HW) proximal Endende end edge (IE) defines a direction extending in the flow direction linear inner track (IT), such that on both sides of the inner track orthogonal equidistant to a blade surface on a pressure side (PRS) or a suction side (SCS) of the blade (B) are present,
wherein the blade (B) at a distance to the wheel disc (HW) distal end edge (OE) defines a extending in the flow direction linear outer track, such that on both sides of the outer track (OT) orthogonal equal distances to the blade surface to the pressure side (PRS) and suction side (SCS) of the bucket (B), wherein a relative bucket length (BLL) for each position on a track (T) which is an inside track (IT) or outside track (OT) are respectively defined as a fraction downstream thereof Position blade length to the entire blade length of the relevant track (T), namely inner track (IT) or outer track (OT),
wherein a meridional angle (MA) for each position of a track (T) is defined as the upstream trapped one Angle between a meridional plane (MPL) through this position and a tangent to the track (T),
characterized in that
in the range between 10% -90% of the relative blade length (BLL) there is a local extremum (LEX) of the meridional angle (MA) of the inner track (IT). Impeller (IMP) according to claim 1, wherein the local extremum (EX01) of the course of the meridional angle (MA) of the inner track (IT) is between 25% - 45% of the relative blade length (BLL). The impeller (IMP) of claim 1, wherein the meridional angle (MA) profile is monotonically decreasing between 10% -90% of the relative blade length (BLL) of the outside track (OT). Impeller (IMP) according to claim 1, wherein the impeller (IMP) comprises a cover disc (COV) defining the flow channels (FC) adjacent to the end extension edge (OE) and attached to the blades (B) in the region of the end extension edge (OE) is. Impeller (IMP) according to claim 1, wherein in the range between 10% -90% of the relative blade lengths (BLL), the maximum difference (DLTM) between the inner track (IT) and the outer track (OT) for a given position along the relative blade lengths (BLL) BLL) of the meridional angle (MA) is between 10 ° and 25 °. Impeller (IMP) according to claim 5, wherein the maximum difference (DLTM) between the inner track (IT) and the outer track (OT) along the relative blade lengths (BLL) of the meridional angle (MA) ranges between 15% -45% of the relative blade lengths (BLL) is located. Impeller (IMP) according to claim 1, wherein the mean extent of the trailing edge (TE) of the blade (B) encloses an angle with a meriodine plane (MPL) between 0 ° -5 °, preferably 0 °. Impeller (IMP) according to claim 1, wherein in the range between 10% -90% of the relative blade lengths (BLL), the course of the meridional angle (MA) of the inner track (IT) has a turning point (TP) between 40% -80% of the relative blade length ( BLL). Impeller (IMP) according to claim 1, wherein in the range between 10% -90% of the relative blade lengths (BLL), the profile of a blade thickness distribution (BT) of the inner track (IT) in the flow direction is monotonically increasing. Impeller (IMP) according to claim 1, wherein the blade leading edge (LE) forms an angle (LEA) between 35 ° to 45 °, preferably 41 ° with a radial plane (RP).

Images