Impeller wheel for a centrifugal turbocompressor

Abstract

An impeller wheel of a turbocompressor, for rotation about an axis, has an inflow cross-section for inflow of a process fluid into the impeller wheel, an outflow cross-section for outflow of the process fluid from the impeller wheel, a wheel disk that defines a hub-side deflection contour from the axial flow direction into the radial flow direction. Blades are applied to the wheel disk, which define flow channels through the impeller wheel, each blade defining a linear inner track and a linear outer track. A meridional angle is defined for each position of a track as the upstream included angle between a meridional plane through the position and a tangent on the track. So that the flow passes through the impeller wheel with improved efficiency, as far as possible without separation, a local extremum of the meridional angle of the inner track is defined.

Claims

1. An impeller wheel of a turbocompressor, for rotation around an axis, comprising: an inlet cross section for the axial inflow of a process fluid into the impeller wheel, an exit cross section for the radial exit of the process fluid from the impeller wheel, a wheel disk which defines a hub-side deflection contour from the axial flow direction to the radial flow direction, blades, attached on the wheel disk, which define flow passages from a leading edge to a trailing edge in the circumferential direction, at least over a part of the flow path of the process fluid through the impeller wheel, wherein the blade leading edge forms an angle of between 35 and 45, with a radial plane, wherein each blade, on an extent end edge which is proximal to the wheel disk, defines a linear inner track extending in the flow direction in such a way that orthogonally equal distances to a blade surface on a pressure side and a suction side of the blade exist on both sides of the inner track, wherein the blade, on an extent end edge which is distal to the wheel disk, defines a linear outer track extending in the flow direction in such a way that orthogonally equal distances to a blade surface on the pressure side and the suction side of the blade exist on both sides of the outer track, wherein a relative blade length for each position on a track, which is an inner track or outer track, is defined in each case as a proportion of the blade lengths located upstream of this position to the overall blade length of the subject track, specifically inner track or outer track, wherein a meridional angle for each position of a track is defined as the upstream included angle between a meridional plane through this position and a tangent to the track, wherein in the region of between 10% and 90% of the relative blade length a local extremum of the meridional angle of the inner track exists.

2. The impeller wheel as claimed in claim 1, wherein the local extremum of the variation of the meridional angle of the inner track lies between 25% and 45% of the relative blade length.

3. The impeller wheel as claimed in claim 1, wherein the impeller wheel has a shroud disk which defines the flow passages, adjacent to the extent end edge, and is attached on the blades in the region of the extent end edge.

4. The impeller wheel as claimed in claim 1, wherein in the region of between 10% and 90% of the relative blade lengths the maximum difference of the meridional angle between the inner track and the outer track for a defined position along the relative blade lengths is between 10 and 25.

5. The impeller wheel as claimed in claim 4, wherein the maximum difference of the meridional angle between the inner track and the outer track along the relative blade lengths lies in the region of between 15% and 45% of the relative blade lengths.

6. The impeller wheel as claimed in claim 1, wherein a middle extent of the trailing edge of the blade includes an angle with a meridional plane of between 0 and 5.

7. The impeller wheel as claimed in claim 6, wherein the middle extent of the trailing edge of the blade includes an angle with a meridional plane of 0.

8. The impeller wheel as claimed in claim 1, wherein in the region of between 10% and 90% of the relative blade lengths the variation of the meridional angle of the inner track has a turning point between 40% and 80% of the relative blade length.

9. The impeller wheel as claimed in claim 1, wherein in the region of between 10% and 90% of the relative blade lengths the variation of a blade thickness distribution of the inner track is monotonically increasing in the flow direction.

10. The impeller wheel as claimed in claim 1, wherein the variation of the meridional angle of the outer track is monotonically decreasing between 10% and 90% of the relative blade length.

11. The impeller wheel as claimed in claim 1, wherein the blade leading edge forms an angle of 41 with the radial plane.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the following text, the invention is explained in more detail based on a specific exemplary embodiment with reference to drawings and graphs. In the drawing:

(2) FIG. 1 shows a view of an impeller wheel according to the invention, with a partially sectioned shroud disk, in the axial direction,

(3) FIG. 2 shows a meridional section along the rotation axis through a schematic view of an impeller wheel according to the section II-II in FIG. 1,

(4) FIG. 3 shows in a synoptic representation a meridional angle distribution along the relative blade length and also the variation of the meridional angle along the relative blade length.

(5) FIG. 4 shows a blade thickness distribution along the relative blade length.

(6) FIG. 5 shows a detailed view of a leading edge as a schematic circumferential tangential section of a radial view.

DETAILED DESCRIPTION OF INVENTION

(7) FIG. 1 shows an axial plan view of an impeller wheel IMP according to the invention, comprising a shroud disk COV, blades B and a wheel disk HW. Indicated in the middle of the wheel disk HW is the rotation axis X around which the impeller wheel rotates along a rotation direction ROT during operation. Schematically indicated in a radial direction is a meridional section II-II along a meridional plane MPL, which is reproduced in FIG. 2. The individual blades B have in each case a pressure side PRS and a suction side SCS. In the axial plan view shown in FIG. 1, the leading edge LE of the blade B is made apparent to the viewer. Where the shroud disk COV is cut away in FIG. 1, an outer track OT is reproduced by a dash-dot line on the outer extent end edge OE of the blade B. An inner track IT, also represented by a dash-dot line, is shown directly on the wheel disk HW on the inner extent end edge IE which is proximal to the wheel disk HW. These facts can also relate to FIG. 2. Each blade B, on an extent end edge IE which is proximal to the wheel disk HW, has a linear inner track IT extending in the flow direction in such a way that orthogonally equal distances to a blade surface on the pressure side PRS or the suction side SCS of the blade B exist on both sides of the inner track. Each blade B, on an extent end edge OE which is distal to the wheel disk HW, has a linear outer track extending in the flow direction in such a way that orthogonally equal distances to the blade surface on the pressure side PRS and the suction side SCS exist on both sides of the outer track.

(8) These corresponding inner tracks and outer tracks on the blades can also be defined in such a way that these tracks are in each case the sum of the middle points of circles inscribed in the blade profiles.

(9) FIG. 3 shows in each case as a function of the relative blade length BLL in the upper graph area the variation of the meridional angle for the inner tack IT and the outer track OT, and in the lower graph area shows the differentiation of the meridional angle MA according to the relative blade length BLL for the inner track IT and the outer track OT.

(10) The blade leading edge LE in this case forms an angle LEA of 41 with a radial plane RP. The leading edge of the blade B is correspondingly located in a slightly set back manner.

(11) The graph of FIG. 4 shows the blade thickness distribution as a variation over the relative blade length BLL for the inner track IT and the outer track OT.

(12) In this case, consideration is to be given to the fact that deviating from this variation a beveling of the leading edges and trailing edges of the blades is designed. By way of example, FIG. 5 shows details of such a beveling on a leading edge of a wheel disk or shroud disk in a schematic circumferential tangential section from the radial view. The example shown there is dimensioned thus:

(13) TABLE-US-00001 Parameter Wheel disk Shroud disk 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

(14) The meanings here being:

(15) SDS: Blade thickness of shroud disk COV

(16) SRS: Blade thickness of wheel disk HW

(17) LZ: Length of the beveling

(18) LU: Transition thickness

(19) SU: Transition length

(20) These parameters can be scaled so that an application to other blade thicknesses is possible.

(21) The graphs of FIGS. 3 and 4 show in each case a variation which is extended on both sides beyond the 0% and 100% positions of the relative blade length BLL. In this case, it is a definition area which in the specific impeller wheel is delimited in each case by the inner and outer extent end edge OE, IE, the leading edge LE and the trailing edge TE of the blade B. The findings according to the invention concerning the distribution of the meridional angle MA for a blade B also apply in conjunction with the blade thickness distribution to the inner track IT and the outer track OT basically independently of the detail from this definition area providing certain limits are not exceeded. Within limits, an extrapolation of this area can also be carried out. The description of the blades B by means of the distribution of the meridional angle MA and the thickness distribution over the extent of the blades B in the flow direction or over the relative blade length BLL leads, in the case of a connection by means of straight lines of the blade profiles spanned by the inner track and the outer track by means of the thickness distribution, to a three-dimensional surface in space which can be produced by means of a flank milling process. In principle, the three-dimensional blade which is spanned by means of so-called regular straight lines between the outer and inner blade profiles is advantageous, wherein in principle a different geometry than a straight line is also conceivable according to the invention, for example a curve, which is defined by means of a polygon or splines and support points.

(22) So that this so-defined general area, which is also referred to as the definition area or as the maximal area, can be used for different compression tasks or impeller wheels IMP, sub-areas are extracted by means of meridional sections from this definition area for the purpose of being used in an impeller wheel design. The definition area according to the invention is suitable in this respect for a field of application of the specific throughflow =V/u*d.sub.2.sup.2 between 0.05 and 0.16, wherein the meanings are:

(23) V: Volumetric flow in cubic meters per second

(24) U: Circumferential speed in meters per second

(25) d.sub.2: Impeller wheel diameter in meters

(26) The embodiment according to the invention of the blade B of an impeller IMP provides according to FIG. 3 that between approximately 10% and 60% of the relative blade length BLL a local extremum LEX of the meridional angle MA of the inner track IT exists. This local extremum LEX advantageously lies between 25% and 45% of the relative blade length BLL. Especially advantageouslyas shown in FIG. 3, first graphthe variation of the meridional angle MA for the outer track OT is monotonically decreasing between 10% and 90% of the relative blade length. Also especially advantageously, between the inner track IT and the outer track OT there is a difference in the meridional angle MA which increases to a maximum difference DLTM along the relative blade length, wherein this actually existing maximum difference is between 10 and 25. Especially advantageously, this maximum difference DLTM occurs in the region of between 15% and 45% of the relative blade length BLL. Especially advantageously, the inner track IT and the outer track OT in the region of the trailing edge TEthat is to say at 100% of the relative blade length BLLhave the same meridional angle MA. It follows from this that the middle extent of the trailing edge TE of the blade B includes an angle with a meridional plane MPL of approximately 0 or is parallel to this meridional plane MPL. This angle deviation in relation to the meridional plane MPL of the trailing edge TE should advantageously be less than 5. A further especially advantageous embodiment of the invention, depicted in the exemplary embodiment, provides that in the region of between 40% and 80% of the relative blade length BLL the variation of the meridional angle MA of the inner track IT has a turning point TP.