JP2014111941A - Axial flow compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-performance compressor blade form capable of reducing a secondary loss or a cross flow and ensuring reliability.SOLUTION: In an axial flow compressor comprising a stator blade row and a rotor blade row in an annular flow passage formed between a rotor and a casing, a flow passage partitioned by a pressure surface and a suction surface of blades neighboring in a circumferential direction of the stator blade row or the rotor blade row is constituted in such a manner that, at least on a rotor-side or casing-side cross section which is a sidewall part, axial flow passage width distribution which is distribution of a flow passage width in a direction, vertical to a rotation axis, from a blade front edge to a blade rear edge of a blade partitioning the flow passage has a deflection point at a downstream side of a throat part where the flow passage width becomes minimum, and is monotonously increased toward the rear edge at the downstream side of the throat part.

Description

  The present invention relates to a gas turbine or industrial axial compressor, and more particularly to an axial compressor having high-performance axial compressor blades.

  Conventionally, subsonic blades located downstream of an axial compressor have been developed through systematic and extensive experimental research using cascade wind tunnels as described in Non-Patent Document 1 (NACA, SP-36). NACA65 wings are applied. In recent years, axial compressors are required to have a high load that achieves both high pressure ratio and low cost by reducing the number of stages. In the subsonic blade at the downstream stage of the high load machine, the secondary flow increases due to the development of the side wall boundary layer, so that the corner stall occurs on the blade surface, and the loss may increase in the conventional blade. Therefore, applying a high-performance airfoil that can suppress corner stall is an important technology for improving the performance of a high-load compressor.

  Patent Document 1 discloses a method for suppressing the secondary flow of an axial compressor. In this method, the airfoil shape at the tip of the blade, where secondary flow is likely to occur, is fixed to the front edge of the blade center line while the blade leading edge position is fixed so that the static pressure gradient between the ventral side and the back side becomes small. The radius of curvature from the trailing edge is adjusted.

JP-A-8-135597

“Aerodynamic Design of Axial-Flow Compressors”, NATIONAL AERONAUTICS AND SPACE ADMINISTRATION, 1965.

  In the conventional technology for reducing the secondary flow loss generated near the side wall as described in Patent Document 1, the blade load on the side wall is reduced by improving the blade mounting angle and the blade shape near the side wall. As a result, methods that suppress secondary flow loss and corner stall are the mainstream. However, there is a concern that the loss increases except for the side wall portion where the blade load increases. Further, unsteady fluid vibrations such as flow disturbance and buffeting due to separation may reduce the reliability of the compressor.

  Accordingly, an object of the present invention is to provide a high-performance compressor blade shape that achieves reduction of loss and securing of reliability.

  To achieve the above object, according to the present invention, in an axial flow compressor having a stationary blade row and a moving blade row in an annular flow path formed between a rotor and a casing, the stationary blade row or the moving blade row is provided. The flow path defined by the pressure surface and the suction pressure surface of the blade adjacent to each other in the circumferential direction is at least from the blade leading edge of the blade defining the flow channel in the cross section on the rotor side or the casing side that is the side wall portion. The axial flow width distribution, which is the flow width distribution in the direction perpendicular to the rotation axis along the blade trailing edge, has an inflection point on the downstream side from the throat portion where the flow path width is minimum, It is configured to monotonously increase toward the rear edge on the downstream side of the throat portion.

  According to the present invention, it is possible to provide a high-performance compressor blade shape that achieves reduction of loss and securing of reliability.

The axial direction flow path width distribution map between the wing | blade of embodiment of this invention. The meridian plane sectional view of the axial flow compressor of the embodiment of the present invention. The two-dimensional sectional view of the axial flow compressor blade which is one of the embodiments of the present invention. The curvature distribution map of the axial flow compressor blade | wing surface which is one of the embodiments of this invention. The two-dimensional sectional view of the axial flow compressor blade which is one of the embodiments of the present invention. The curvature distribution map of the axial flow compressor blade | wing surface which is one of the embodiments of this invention. The blade-to-blade and blade-surface static pressure distribution diagram for explaining the operation of the embodiment of the present invention. The comparison of the total pressure loss distribution in embodiment of this invention. Comparison of streamline distributions near the blade suction surface in the embodiment of the present invention. Comparison of blade surface static pressure distribution in an embodiment of the present invention.

  FIG. 2 is a partial cross-sectional view of a multistage axial compressor to which the airfoil of the present invention is applied.

  The axial compressor 1 includes a rotating rotor 2 to which a plurality of moving blade rows 4 are attached and a casing 3 to which a plurality of stationary blade rows 5 are attached. An annular flow path is formed by the rotor 2 and the casing 3. . The moving blade rows 4 and the stationary blade rows 5 are alternately arranged in the axial direction, and a single moving blade row and a stationary blade row constitute a stage. The rotor 2 is driven by a drive source (not shown) such as a motor or a turbine installed on the same rotary shaft 6. The inflow airflow 10 passes through the plurality of stationary blade rows and the plurality of rotor blade rows and becomes a high-temperature, high-pressure outflow airflow 11 while being decelerated.

  In the axial flow compressor, kinetic energy is given to the inflow airflow by the moving blade row, and the kinetic energy is converted to pressure energy and boosted by turning and decelerating the flow by the stationary blade row. Since the boundary layer develops on the side wall of the annular flow path in such a flow field, the secondary flow loss increases in the subsonic cascade located downstream of the axial compressor. Further, in a high-load compressor aimed at reducing the cost by increasing the pressure ratio of the axial compressor and reducing the number of stages, the corner stall on the blade surface, which is the main factor of this secondary flow loss, is expanded. Therefore, the generation of a blade shape that can suppress corner stall is a technical problem.

  However, according to the embodiment of the present invention described below, in the flow path between two adjacent blade cascades, the static pressure gradient from the blade pressure surface to the blade suction surface can be made uniform in the direction perpendicular to the flow, Cross flow from the pressure surface to the suction surface between the blade rows can be suppressed. By suppressing this cross flow, the corner stall generated on the blade suction surface side can be reduced. Since the corner stall that is the main factor of the secondary flow loss can be suppressed, the blade row loss can be reduced, and the efficiency of the entire axial flow compressor can be improved.

  Further, by suppressing the corner stall of the blade row, the outflow angle can be improved, and therefore, the inflow angle of the stationary blade row or the moving blade row located on the downstream side of the blade row to which the present invention is applied is improved. Loss reduction and high performance can be achieved in the paragraph consisting of the moving blade and the stationary blade. Furthermore, unsteady fluid vibration such as buffeting due to separation on the blade surface can be avoided, and the reliability of the axial flow compressor can be ensured.

  Hereinafter, the AA cross section of the stationary blade row 5 will be described by showing a plurality of examples. However, the present invention is not limited to the stationary blade row, and can be similarly applied to the moving blade row.

  FIG. 3 shows an airfoil of the axial compressor according to the first embodiment of the present invention. FIG. 3 illustrates a cylindrical cross section of two airfoils adjacent in the circumferential direction with respect to the AA cross section of the stationary blade row 5 of FIG. The airfoil includes a blade suction surface 21, a blade pressure surface 22, a leading edge portion 23, and a trailing edge portion 24. Then, a flow path having an axial flow path width 31 extending from the front edge portion 23 to the rear edge portion 24 is formed by the suction surface 21 and the pressure surface 22 of the two adjacent blades. The inflow airflow flows through the flow path.

  FIG. 1 shows the distribution of the channel width with respect to the axial code length. In FIG. 1, the flow path width distribution 41 of the conventional blade is represented by a dotted line, and the flow path width distribution 42 of the blade of the present invention is represented by a solid line for comparison. In the conventional blade, the flow path width becomes the minimum in the vicinity of 30% of the axial cord length, and monotonously increases toward the trailing edge on the downstream side. However, the flow path width distribution 42 in the embodiment of the present invention is configured to have an inflection point 42a on the downstream side from the position where the axial flow path width is minimum (hereinafter, the throat portion). Further, as shown in FIG. 1, the axial flow path width distribution is configured to be maximum at the trailing edge without having a local maximum value or a local minimum value on the downstream side of the throat portion. That is, the axial flow path width distribution on the downstream side of the throat portion is a curve having a positive slope.

  Next, the blade shape of FIG. 3 will be described using the blade surface curvature distribution of FIG. FIG. 4 is a comparison of the blade surface curvature distribution 51 of the conventional blade and the solid line the blade surface curvature distribution 52 of the blade of the first embodiment of the present invention. FIG. 4A shows a blade surface curvature distribution of the pressure surface in FIG. In FIG. 4A, the position where the curvature is minimum corresponds to the throat portion where the flow is accelerated most. As shown in FIG. 4B, the blade of the present embodiment has a curvature distribution that once has a maximum value 52a and then has a minimum value 52b on the downstream side of the throat portion of the axial cord length on the pressure surface. It is configured as follows. This maximum value 52a is preferably in the range of 50% to 70% code length. Further, in this embodiment, the curvature of the suction surface is the same as that of the conventional blade, and the blade surface curvature distribution monotonously increases.

  FIG. 5 shows an airfoil of an axial compressor according to the second embodiment of the present invention. FIG. 5 illustrates a cylindrical cross section of two airfoils adjacent in the circumferential direction with respect to the AA cross section of the stationary blade row of FIG. The blade pressure surface 22, the front edge portion 23, and the rear edge portion 24 are configured. The difference between the blade of this embodiment shown in FIG. 5 and the first embodiment shown in FIG. 3 is that the flow width distribution on the downstream side of the throat portion of the axial cord length shown in FIG. As a method of doing this, not the curvature of the pressure surface 22 but the curvature on the downstream side of the throat portion on the negative pressure surface 21 is increased.

  However, also in the airfoil shown in the present embodiment, the flow path width distribution of the flow path formed by adjacent blades is the same as the airfoil shown in the first embodiment, as shown in FIG. Become.

  FIG. 6 shows the blade surface curvature distribution of the blade of this embodiment (FIG. 5), where the dotted line is the blade surface curvature distribution 51 of the conventional blade and the solid line is the blade surface curvature distribution 52 of the blade of this embodiment. FIG. 6 (a) shows the blade surface curvature distribution on the suction surface side, and FIG. 6 (b) shows the blade surface curvature distribution on the pressure surface side. In the blade of this embodiment, the curvature on the pressure surface side is the same as that of the conventional blade. On the other hand, the curvature on the suction surface side of the blade 52 of the present invention is configured to have a curvature distribution that once has a maximum value 52a downstream from the throat portion of the axial code length, and from the maximum value 52a toward the trailing edge. The curvature is gradually reduced. This maximum value 52a is preferably in the range of 50% to 70% code length.

  In a general blade structure, the pressure surface side and the suction surface side are smoothly connected. Therefore, precisely, the curvature distribution shows a rapid change in the vicinity of the front edge portion 23 and the rear edge portion 24 of the blade surface position. However, in the figure, such a connection portion is not particularly mentioned.

  In the first embodiment and the second embodiment, the curvature distribution on either the pressure surface or the suction surface is changed to satisfy the axial flow width distribution 42 of the blade of the present invention shown in FIG. The case where it is made to have been explained. These can be combined, and the flow distribution as shown in FIG. 1 can be obtained by simultaneously adopting the curvature distribution of the pressure surface described in the first embodiment and the curvature distribution of the suction surface described in the second embodiment. It is possible to satisfy the road width distribution. However, in that case, it is necessary from the viewpoint of blade strength and reliability that the blade thickness distribution on the downstream side of the throat portion of the axial cord length is larger than the trailing edge thickness of the blade.

  Next, the blade structure described as the embodiment, that is, the throat portion having the smallest flow path width is provided on the upstream side from the axial code length of 50%, and the blade is formed from the blade leading edge of the blade defining the flow path. By adopting a wing (hereinafter referred to as an invention wing for the sake of simplicity) that has an inflection point downstream of the throat portion in the axial flow path width distribution along the trailing edge. The operation will be described.

  FIG. 7A shows the static pressure distribution between two adjacent blades, and FIG. 7B shows a conceptual diagram of the static pressure distribution on the blade surface. The solid line in FIG. 7A represents the isostatic pressure line 61 between the blades, and the alternate long and short dash line represents the pressure gradient 62 in a cross section perpendicular to the flow along the pressure surface of the isostatic line. Further, an axial distance 65 determined from the intersection 64 between the isostatic line 61 and the negative pressure surface and the intersection 63 with the pressure surface is illustrated. The axial distance 65 is represented by the difference in axial position between the negative pressure surface and the pressure surface having the same static pressure value as the isostatic pressure line in FIG. 7B.

  By adopting the invention blade as described above and enlarging the flow path so that the flow path width distribution has an inflection point on the downstream side from the throat part of the axial code length, it is shown in FIG. The axial distance can be shortened.

  Thus, by shortening the axial distance 65 of the isostatic line, the isostatic line 61 and the static pressure gradient 62 between the blades shown in FIG. The pressure gradient in the direction perpendicular to the flow between the blades can be reduced. Thereby, the cross flow generated between the blades can be suppressed, and the secondary flow loss can be reduced and the corner stall can be reduced.

  Further, the blade according to the present invention is configured such that the inter-blade channel width distribution downstream of the throat portion of the axial code length has an inflection point. The throat portion has the smallest flow path width between the blades, and the flow is accelerated to the maximum. Then, the flow is decelerated on the downstream side, and the static pressure is recovered (increased). Therefore, in the region where the flow is decelerated and the static pressure rises, the turbulent boundary layer on the blade surface develops and the flow is easily separated, so that the static pressure gradient 62 between the blades in that region can be made uniform. This is effective in reducing secondary flow loss and corner stall.

  A three-dimensional blade can be designed by arranging a plurality of the inventive blades as described above in the blade height direction and stacking them in accordance with the center of gravity of the blade. For example, for the stationary blade row 5 shown in FIG. 2, the shapes of the 0% cross section 71 on the casing side, the 50% cross section of the average diameter, and the 100% cross section 72 on the rotor side are designed, and the other cross sections are obtained by interpolation. It is also possible to design a three-dimensional wing by stacking the center of gravity of each airfoil. Further, by applying the blades shown in the embodiments only to the 0% cross section 71 and the 100% cross section 72 which are the side wall portions, and applying the conventional blades to the other cross sections, a three-dimensional flow that reduces only the secondary flow loss is achieved. It is also possible to design a wing.

  The effect of the blade of the present invention designed as described above on the three-dimensional flow field will be described. FIG. 8 represents the total pressure loss coefficient 82 with respect to the inflow angle of the inventive blade by a solid line, and compares it with the total pressure loss coefficient 81 with respect to the inflow angle of the conventional blade, which is represented by a dotted line. In the figure, a design inflow angle 83 is indicated by a one-dot chain line. With the inventive blade, corner stall is suppressed at the design inflow angle, so it can be confirmed that the total pressure loss is reduced as compared with the conventional blade. In addition, even on the stall side where the inflow angle is large, the total pressure loss coefficient of the inventive wing is suppressed compared to the conventional wing, so it can be seen that it has a wide operating range and high performance can be achieved. .

  FIG. 9 shows a comparison of streamlines near the suction surface of the inventive blade 85 and the conventional blade 84. In the flow field of the conventional blade in FIG. 9A, it can be confirmed that a corner stall 86 is generated in which the flow is separated in the vicinity of both side walls of the trailing edge. On the other hand, in the invention wing, the corner stall is suppressed. In particular, it can be remarkably confirmed that the peeling region is reduced in the 0% cross section 71 on the outer peripheral side.

FIG. 10 shows the blade surface static pressure distribution in the cross section 87 shown by the one-dot chain line in FIG. As shown in FIG. 9, this section has a small effect of corner stall in the vicinity of the side wall of the conventional blade, and the section on the casing side is selected as a representative. FIG. 10 shows the static pressure distribution on the blade surface with respect to the axial cord length from the leading edge to the trailing edge. The dotted line represents the static pressure distribution 91 of the conventional blade, and the solid line represents the static pressure distribution 92 of the inventive blade. In the invention blade, the static pressure on the suction surface is extremely large on the downstream side of the cord length of 50%. This is equivalent to increasing the curvature of the suction surface. Furthermore, the change in static pressure is moderated downstream from the 70% cord length of the suction surface, which can be achieved by reducing the curvature of the suction surface. The axial distance 65 between the intersections of the isostatic line, the pressure surface, and the suction surface is reduced on the downstream side of the throat portion of the inter-blade channel located near the 30% cord length of the blade of the present invention, compared to the conventional blade. Can be confirmed. By achieving such blade surface static pressure distribution, the static pressure gradient between the blades can be made uniform in a cross section perpendicular to the flow, and crossflow can be suppressed.

  From the above, by using the structure of the blade according to the present invention, it is possible to reduce the secondary flow loss and achieve high efficiency of the axial flow compressor. In addition, since the corner stall can be suppressed in the blade of the present invention, the outflow angle can be made closer to the design value compared to the conventional blade, and the blade row matching can be improved for the moving and stationary blades positioned on the downstream side. Therefore, high performance can be achieved even with multistage blades. Further, unsteady fluid vibration such as buffeting due to flow disturbance such as corner stall on the blade surface can be avoided, and the reliability of the blade can be improved.

  In addition, as a general method for reducing secondary flow loss by improving the performance of conventional blades, for example, by increasing the blade mounting angle on the side wall of the stationary blade row, the blade load on the side wall is reduced. There is a means to suppress corner stall. In order to dispose the stationary blade row in the casing, it is necessary to provide a shroud portion on the side wall of the stationary blade, and to provide a fillet on the side wall of the stationary blade so as to completely ride on the shroud portion. As described above, when the blade attachment angle of the side wall portion is increased, the blade shape may protrude from the shroud portion or the fillet portion may be partially excluded. However, in the blade according to the present invention, the blade attachment angle of the side wall portion is almost the same as that of the conventional blade, so that the shroud portion can be shared and the reliability of the blade can be ensured.

  Next, a method for generating the blade shape of the blade according to the present invention will be described. When generating a two-dimensional blade cross-sectional shape, generally, the maximum Mach number of the blade suction surface and the shape factor of the suction surface are evaluated, and the blade shape is generated so that the maximum Mach number and shape factor can be minimized. To do. The shape factor is expressed as a ratio of the excluded thickness and the momentum thickness in the blade boundary layer, and is an index serving as a standard for boundary layer separation. It is generally known that in the turbulent boundary layer, the flow is separated at a shape factor of 1.8 to 2.4 or more.

  In the blade of the present invention, when generating a two-dimensional blade cross-sectional shape, an axial distance of an isostatic line, which is an index considering a three-dimensional flow field, is added (FIG. 7). An objective function F for generating the wing of the present invention is represented by Expression (1). Here, F1 is the shape factor, F2 is the maximum Mach number, F3 is the axial distance of the isostatic line, and is an index that is made dimensionless by the ratio to each reference value. Α, β, and γ are weighting coefficients. By minimizing the objective function F shown in Equation (1), a high-performance blade shape that simultaneously considers blade shape loss and secondary flow loss can be generated in two-dimensional blade cross-sectional shape generation.

  In the embodiment of the present invention, the function and effect are described for the subsonic stage stationary vane positioned downstream of the axial compressor, but by changing the weighting coefficient in Equation (1), The present invention can also be applied to the design of transonic blades located on the upstream side of the compressor or high subsonic blades located in the intermediate stage. Further, it is obvious that the same effect can be obtained even if the present invention is applied not only to the stationary blade but also to the moving blade.

  In addition, by incorporating an index as shown in Expression (1) into the design system, it is possible to design an arbitrary blade shape from the upstream side to the downstream side of the compressor, which is effective in shortening the design time. In addition, it is possible to uniquely design the blade shape without depending on the designer in improving the blade shape.

  In addition to the gas turbine axial compressor, the present invention can also be applied to industrial axial compressors.

DESCRIPTION OF SYMBOLS 1 Axial compressor 2 Rotor 3 Casing 4 Rotor blade row 5 Stator blade row 21 Negative pressure surface 22 Pressure surface 23 Front edge portion 24 Rear edge portion 31 Axial flow passage width 41 Flow passage width distribution 42 of conventional blade Channel width distribution 42a Inflection point 52a Maximum value 52b Minimum value 61 Isostatic pressure line 62 Pressure gradient 63 Intersection point of isostatic line and pressure surface 64 Intersection point of isostatic line and negative pressure surface 65 Isostatic pressure line Axial distance 81, 82 Total pressure loss coefficient for inflow angle 83 Design inflow angle 86 Corner stall 7 10% section 72 100% section 91, 92 Blade surface static pressure

Claims (6)

In the axial flow compressor having a stationary blade row and a moving blade row in an annular flow path formed between the rotor and the casing,
The flow path defined by the pressure surface and the suction surface of the blades adjacent to each other in the circumferential direction of the stationary blade row or the moving blade row, at least in the cross section on the rotor side or the casing side that is a side wall portion
The axial throat width distribution, which is the distribution of the passage width in the direction perpendicular to the rotation axis, from the leading edge of the blade that divides the passage to the trailing edge of the blade, is the throat with the smallest passage width. An axial flow compressor characterized by having an inflection point on the downstream side of the part and monotonously increasing toward the trailing edge on the downstream side of the throat part. The axial compressor according to claim 1, wherein
An axial compressor characterized by having a throat portion with a minimum flow path width on the upstream side of the axial cord length of 50%. The axial compressor according to claim 1, wherein
The curvature of the suction surface of the stationary blade row or the moving blade row is monotonously increased downstream from the throat portion, and the curvature of the pressure surface has a maximum value and a minimum value downstream from the throat portion. An axial flow compressor characterized by that. The axial compressor according to claim 1, wherein
An axial flow compressor characterized in that the curvature of the pressure surface of the stationary blade row or the moving blade row monotonously increases, and the curvature of the suction surface has a maximum value downstream of the throat portion. The axial compressor according to claim 1, wherein
The curvature of the suction surface of the stationary blade row or the moving blade row is configured to have a maximum value downstream of the throat portion, and the curvature of the pressure surface has a maximum value and a minimum value downstream of the throat portion. An axial flow compressor characterized in that it has a configuration. A blade that is arranged in an annular flow path formed between the rotor and the casing to form a stationary blade row or a moving blade row, and that forms a flow passage between the pressure surfaces and suction surfaces of the blades adjacent in the circumferential direction. Design method,
At least a section on the rotor side or the casing side which is a side wall portion,
On the downstream side of the throat portion where the flow path width in the direction perpendicular to the rotation axis of the flow path between the blades is minimized,
A design method for generating a blade shape using an objective function including an axial distance between two points where an isostatic line intersects a pressure surface and a suction surface as a design index, wherein the index of the axial distance is An index indicating a more suitable value as the isobar is closer to a direction perpendicular to the flow along the pressure surface, and the axial distance is shortened within a range that monotonously increases toward the trailing edge downstream of the throat portion. Then, the blade is designed so that the isostatic line approaches a direction perpendicular to the flow along the pressure surface.

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