EP3205885A1 - Compressor rotor blade and method for profiling said blade - Google Patents

Abstract

The invention relates to a compressor blade for a compressor in Axialbauweise, with a blade profile having a transonic portion, and extending in the transonic portion profile section (21) of the blade profile having a concave suction side region (10) on its suction side (5) at least partially upstream of a compression surge (18) having a flow established in the compressor at a nominal operating condition of the compressor, whereby the surge (18) is located downstream of a compression surge which would have a flow that would be at a pressure conventional compressor blade, which differs from the compressor blade (1) only in that it is formed on its suction side (5) exclusively convex, and would set in the nominal operating condition.

Description

The invention relates to a compressor blade and a method of profiling the compressor blade.

An axial-flow compressor has at least one blade ring with a plurality of compressor blades for compressing a working fluid. The compressor blade has a radially inner subsonic section, in which the compression takes place by means of a deflection of the flow of the working medium. Furthermore, the compressor blade on a transonic section, in which the compression takes place for the most part by means of a compression shock, in which the working fluid is delayed from supersonic to subsonic speed.

Losses in the flow of the working fluid in the transonic section arise, for example, in the compression shock and by separation of the boundary layer on the compressor blade in the region of the compression shock. The losses cause a reduction in the efficiency of the compressor.

The object of the invention is therefore to provide a compressor blade and a method for profiling the compressor blade, with which an increase in the efficiency of the compressor blade having a compressor can be achieved.

The compressor blade according to the invention for an axial compressor has a blade profile which has a transonic section and a profile section of the blade profile which extends in the transonic section and which has a concave suction side region on its suction side which is disposed at least partially upstream of a compression stroke exhibited by a flow established in the compressor at a nominal operating condition of the compressor whereby the surge is located downstream of a compression surge which would have a flow similar to a conventional compressor blade and the prior art Set nominal operating condition.

The inventive method for profiling a compressor blade for an axial design compressor, the compressor blade having a blade profile with a transonic section, comprises the steps of providing a geometric model of the blade profile, the blade profile having a profile cut extending in the transonic section ; Determining boundary conditions for a flow around the blade that occurs at a nominal operating condition of the compressor; Changing the profile section such that the suction side has a concave suction side region located at least partially upstream of a compression stroke exhibited by a flow adjusting in the compressor at the boundary conditions whereby the surge is located downstream of a compression surge that would have flow; which would occur in the geometric model prior to changing the profile section and at the nominal operating condition.

It has been found that the compressor with the compressor blade according to the invention and / or with the compressor blade profiled with the method according to the invention has a higher efficiency with at least the same operating range than a compressor with the conventional compressor blade. In addition, the Mach numbers on the suction side of the compressor blade according to the invention prior to the compression shock are lower than on the suction side of the conventional compressor blade. Thus, separations of the flow on the suction side of the invention Compressor blade less likely than the conventional compressor blade. In addition, the compressor blade according to the invention can be performed with a shorter length of chord profile than is the case with the conventional compressor blade, without thereby sacrificing efficiency or a reduction of the working area.

It is preferred that the profile section of the conventional compressor blade is formed exclusively concave on the pressure side and / or is formed exclusively convex on the suction side.

It is preferable that in the concave suction side region, the curve of the curvature multiplied by the length of the chord has a minimum value that is from -1.2 to -0.5. The profile section preferably has on its suction side a convex suction side region, which is arranged downstream of the concave suction side region. It is preferable that in the convex suction side portion, the curve of the curvature of the convex suction side portion has a maximum value larger than the maximum value of the curve of the curvature in the corresponding portion of the conventional compressor blade. In the convex suction side region, the curve of the curvature multiplied by the length of the chord has preferably a maximum value that is from 2 to 4. It is preferred that the point of the concave suction side region with the minimum curvature when projecting perpendicularly onto the chord of the profile section on this prescribes a projection point which is from the leading edge of the profile section of 40% to 80% of the length of the chord. The profile section preferably has on its pressure side a convex pressure side region, which is arranged in a region which is arranged opposite the concave suction side region. Each of these measures can further increase the efficiency of the compressor.

It is preferred that the profile section on a cylindrical surface whose axis coincides with the axis of the compressor lie on a conical surface whose axis coincides with the axis of the compressor on an S ₁ flow area of the compressor or in a tangential plane of the compressor. The S ₁ flow area extends in the circumferential direction and in the axial direction of the axial flow machine and describes a surface that follows an idealized flow.

When changing the profile section whose skeleton line is preferably moved, in particular only the skeleton line is moved. As a result, it is advantageously achieved that the width of the channel between two compressor blades arranged adjacent in a rotor blade ring remains unchanged. It is preferred that the geometric model before the modification of the profile section on its pressure side exclusively concave and / or formed exclusively convex on the suction side.

It is preferable that the profile section is changed such that in the concave suction side area, the curve of the curvature multiplied by the length of the chord has a minimum value that is from -1.2 to -0.5. The profile section is preferably modified such that the profile section has on its suction side a convex suction side region, which is arranged downstream of the concave suction side region. It is preferable that the profile section is changed such that in the convex suction side area, the curve of the curve has a maximum value larger than the maximum value of the curve of the curve in the corresponding area of the conventional compressor blade. The profile section is preferably changed in such a way that in the convex suction side region the course of the curvature multiplied by the length of the chord has a maximum value which is from 2 to 4. It is preferred that the profile section is changed such that the point of the concave suction side region with the minimum curvature when projecting perpendicularly onto the chord of the profile section on this one projection point which is from 40% to 80% of the length of the chord from the leading edge of the profile section. Each of these measures can further increase the efficiency of the compressor.

• Figur 1 die erfindungsgemäße Verdichterlaufschaufel mit einem rechnerisch bestimmten Strömungsfeld,
• Figur 2 Machzahlverläufe an der herkömmlichen Verdichterlaufschaufel und an der erfindungsgemäßen Verdichterlaufschaufel,
• Figur 3 einen Profilschnitt der erfindungsgemäßen Verdichterlaufschaufel und
• Figur 4 Krümmungsverläufe an der erfindungsgemäßen Verdichterlaufschaufel.

The invention will be explained in more detail below with reference to the accompanying schematic drawings and mathematically determined data. Show it

• FIG. 1 the compressor blade according to the invention with a computationally determined flow field,
• FIG. 2 Mach number curves on the conventional compressor blade and on the compressor blade according to the invention,
• FIG. 3 a profile section of the compressor blade according to the invention and
• FIG. 4 Curves of the compressor blade according to the invention.

Like it out FIGS. 1 and 3 As can be seen, a compressor blade 1 for a compressor in axial construction on a blade profile. The blade profile has a radially inner subsonic section and a radially outer transonic section, wherein FIGS. 1 and 3 only the transonic section is shown. The blade profile has a profile section 21 which extends in the transonic section. For example, the profile section 21 is located on a cylindrical surface whose axis coincides with the axis of the compressor, on a conical surface whose axis coincides with the axis of the compressor, on an S ₁ flow area of the compressor or in a tangential plane of the compressor.

The profile section 21 has a front edge 2, a trailing edge 3, a pressure side 4 and a suction side 5. In figure 3 In addition, a chord 22 is drawn, which extends as a straight line from the front edge 2 to the trailing edge 3. Further shows FIG. 3 a skeleton line 23 which extends from the front edge 2 to the trailing edge 3 and is always located in a direction perpendicular to the chord 22 midway between the pressure side 4 and the suction side 5.

FIG. 1 shows a two-dimensional flow distribution of a working medium flowing in the compressor in a region of the compressor. In FIG. 1 1, a blade row 15 with the compressor blades 1, a blade row 15 downstream blade row 16 and a blade row 15 upstream blade row 17 are shown. The profile section 21 has on its suction side 5 a concave suction side region 10, which is arranged at least partially upstream of a compression joint 18, which has an adjusting in the compressor at a nominal operating condition of the compressor flow. The compression shock 18 is in FIG. 1 arranged in the areas of flow in which the Mach number decreases from higher than 1 to lower than 1.

By the concave suction side region of the compression shock 18 is disposed downstream of a compression shock, which would have a flow which is in a conventional compressor blade, which may differ from the compressor blade 1 in that it is formed exclusively convex on its suction side 5, and in the Set nominal operating condition.

FIG. 2 FIG. 4 shows a comparison of the Mach number curves on the compressor blade 1 and the Machzahlverläufe on the conventional compressor blade. About the horizontal axis 19 is a point on the chord 22 of the profile section 21 and over the vertical axis 20, the Mach number is plotted. Reference numeral 6 denotes the Mach number characteristic at the pressure side of the conventional compressor blade, with the reference numeral 7 Machzahlverlauf on the suction side of the conventional compressor blade is designated by the reference numeral 8 is the Machzahlverlauf on the pressure side 4 of the compressor blade 1 and the reference numeral 9 Machzahlverlauf on the suction side 5 of the compressor blade 1 is designated.

Out FIG. 2 It can be seen that the Machzahlverlauf 9 on the suction side 5 of the compressor blade 1 immediately upstream of the compression shock 18 lower supersonic Mach numbers than the Machzahlverlauf 7 on the suction side of the conventional compressor blade immediately upstream of the compression shock. These lower supersonic Mach numbers are maintained over a longer extent along the chord 22 than in the conventional compressor blade. Due to the lower supersonic Mach numbers before the compression shock 18 losses are reduced. By keeping the supersonic Mach numbers over the longer extent, the total profile load correlated with the Mach number difference on the pressure side 4 and the suction side 5 is comparably high in the subsonic region downstream of the inspection shock 18 as in the conventional compressor blade. Moreover, it is off FIG. 1 It can be seen that the compression stroke 18 is arranged obliquely, which means that with increasing distance from the suction side 5, the compression shock 18 moves upstream. This also leads to a reduction of losses. Furthermore, the FIG. 2 It can be seen that the profile load on the compressor blade 1 after the compression stroke 18 is significantly higher than in the conventional compressor blade. Due to the reduced losses and higher profile load in the subsonic region, a higher efficiency can be achieved with the compressor rotor blade 1 than with the conventional compressor rotor blade. Due to the higher efficiency, the compressor blade 1, as it is in FIG. 2 is shown to be shorter than the conventional compressor blade, thereby reducing losses can be reduced by friction of the working fluid to the compressor blade 1.

wobei Δs die Länge eines Kreisbogens und Δα der Differenzwinkel zwischen den Tangenten an den Endpunkten des Kreisbogens ist. FIG. 4 shows a curvature 27 along the pressure side 4 and a curvature 28 along the suction side 5. About the horizontal axis 25, the length of the chord 22 and the vertical axis 26, the curvature multiplied by the length of the chord 1 is applied. The curvature k is defined as $$\mathit{k}=\underset{\mathrm{\Delta }\mathit{s}\to 0}{\lim }\frac{\mathrm{\Delta }\mathit{\alpha }}{\mathrm{\Delta }\mathit{s}}=\frac{\mathit{d.alpha}}{\mathit{ds}}.$$

where Δs is the length of a circular arc and Δα is the difference angle between the tangents at the end points of the circular arc.

Concave suction side areas and convex pressure side areas are characterized by a negative sign of the curvature. Convex suction side regions and concave pressure side regions are characterized by a positive sign of the curvature.

In the concave suction side region 10, the curve of the curvature multiplied by the length of the chord 22 has a minimum value that is from -1.2 to -0.5. The profile section 21 has on its suction side 5 a first convex suction side region 11, which is arranged downstream of the concave suction side region 10. The profile section 21 has on its suction side 5 a second convex suction side region 12, which is arranged upstream of the concave suction side region 10. In the convex suction side region 11, the curve of curvature has a maximum value greater than the maximum value of the curve of the curvature in the corresponding region of the conventional compressor blade. Specifically, in the convex suction side region 11, the curve of the curvature multiplied by the length of the chord 22 has a maximum value which is from 2 to 4.

The point of the concave suction side region 10 with the minimum curvature when projecting perpendicularly onto the chord 22 of the profile section 21 on this projecting point 24, which is from the leading edge of the profile section 21 of 40% to 80% of the length of the chord 22. The point of the convex suction side region 11 with the maximum curvature when projecting perpendicularly onto the chord 22 of the profile section 21 on this projecting point 24, which is from the leading edge of 21 of 80% to 100% of the length of the chord 22. The profile section 21 has on its pressure side 4 a convex pressure side region 14, which is arranged in a region which is arranged opposite the concave suction side region 10.

The compressor blade 1 is exemplary profiled as follows: Providing a geometric model of the blade profile, which is exclusively convex on its suction side and concave on its pressure side, wherein the blade profile has a profile section 21 which extends in the transonic section and on a Cylinder surface, whose axis coincides with the axis of the compressor, on a conical surface whose axis coincides with the axis of the compressor, on an S ₁ flow area of the compressor or in a tangential plane of the compressor; Determining boundary conditions for a flow around the blade 14, 15 that occurs at a nominal operating condition of the compressor; Modifying the profile section 21 such that only the skeleton line is displaced and the suction side 5 has a concave suction side portion 10 which is at least partially upstream of a compression shock 18, which has a set in the compressor at the boundary conditions flow, whereby the compression shock 18 downstream is arranged a compression shock, which would have a flow, which in the geometric model before changing of the profile section and at the nominal operating condition.

Whether the compaction shock 18 shifts downstream by changing the profile section can be determined by calculation, in particular by a finite volume method, or experimentally.

Although the invention has been further illustrated and described in detail by the preferred embodiment, the invention is not limited by the disclosed examples, and other variations can be derived therefrom by those skilled in the art without departing from the scope of the invention.

Claims (16)

A compressor blade for an axial compressor having a blade profile having a transonic section and a profile section (21) of the blade profile extending in the transonic section having on its suction side (5) a concave suction side region (10) at least partially upstream of a compression stroke (18) having a flow established in the compressor at a nominal operating condition of the compressor, whereby the surge (18) is located downstream of a compression surge which would have a flow commensurate with a conventional compressor blade set the nominal operating condition. A compressor blade according to claim 1, wherein in the concave suction side region (10), the curve of the curvature multiplied by the length of the chord (22) has a minimum value which is from -1.2 to -0.5. A compressor blade according to claim 1 or 2, wherein the profile section (21) has on its suction side (5) a convex suction side portion (11) disposed downstream of the concave suction side portion (10). A compressor blade according to claim 3, wherein in the convex suction side region (11), the curve of the curvature has a maximum value larger than the maximum value of the curve of the curvature in the corresponding region of the conventional compressor blade. A compressor blade according to claim 3 or 4, wherein in the convex suction side region (11), the curve of the curvature multiplied by the length of the chord (22) has a maximum value which is from 2 to 4. The compressor blade according to any one of claims 1 to 5, wherein the point of the concave suction side region (10) with the minimum curvature when projecting perpendicularly onto the chord (22) of the profile section (21) defines thereon a projection point (24) projecting from the leading edge of the profile Profile section (21) from 40% to 80% of the length of the chord (22) is removed. A compressor blade according to any one of claims 1 to 6, wherein the profile section (21) has on its pressure side (4) a convex pressure side portion (14) disposed in an area opposite to the concave suction side portion (10). A method of profiling a compressor blade (1) for an axial design compressor, the compressor blade (1) having a blade profile with a transonic section and the method comprising the steps of: Providing a geometric model of the airfoil profile, the airfoil profile having a profile section (21) extending in the transonic section; - Setting boundary conditions for a flow around the blade (14, 15), which occurs at a nominal operating condition of the compressor; - Changing the profile section (21) such that the suction side (5) has a concave suction side region (10) which is at least partially upstream of a compression shock (18), which has an adjusting in the compressor at the boundary conditions flow, whereby the Compression shock (18) is arranged downstream of a compression shock, which would have a flow that would occur in the geometric model before changing the profile section and the nominal operating condition. A method according to claim 8, wherein the profile section (21) on a cylindrical surface, whose axis coincides with the axis of the compressor, on a conical surface whose axis coincides with the axis of the compressor, is located on an S ₁ flow area of the compressor or in a tangential plane of the compressor. Method according to claim 8 or 9, wherein, when changing the profile section (21), its skeleton line (23) is displaced, in particular only the skeleton line (23) is displaced. Method according to one of claims 8 to 10, wherein the geometric model before changing the profile section (21) on the pressure side (4) is exclusively concave and / or on the suction side (5) is formed exclusively convex. Method according to one of claims 8 to 11, wherein the profile section is changed such that in the concave suction side region (10) the curve of the curvature multiplied by the length of the chord (22) has a minimum value of -1.2 to -0 , 5 is. Method according to one of claims 8 to 12, wherein the profile section (21) is changed such that the profile section (21) has on its suction side (5) a convex suction side region (11) which is arranged downstream of the concave suction side region (10). Method according to one of claims 8 to 12, wherein the profile section (21) is changed such that in the convex suction side region (11) the curve has a maximum value which is greater than the maximum value of the course of the curve in the corresponding region of the conventional one compressor blade. A method according to claim 13 or 14, wherein the profile cut is changed such that in the convex suction side region (11) the curve of the curvature multiplied by the length of the chord (22) has a maximum value which is from 2 to 4. Method according to one of claims 8 to 15, wherein the profile section (21) is changed such that the point of the concave suction side region (10) with the minimum curvature when projecting perpendicularly onto the chord of the profile section on this one projection point (24), from the leading edge of the profile section of 40% to 80% of the length of the chord (22) is removed.

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