A high-load diffuser cascade structure with a local non-smooth drag-reducing rib surface and a design method thereof

Abstract

The application provides a high-load diffuser cascade structure with a local non-smooth drag-reducing rib surface and a design method thereof. The diffuser cascade structure is a planar cascade structure or a ring cascade structure, and the planar cascade structure and the ring cascade structure are provided with a non-smooth drag-reducing rib surface. The application can control various resistances in the cascade channel, thereby reducing separation and vortex loss caused by increased resistance, mixing loss of the main flow and the backflow, and friction loss of the airflow and the blade wall, and further improving the performance of the compressor.

Description

Technical Field

[0001] This invention relates to the field of turbomachinery technology, and more particularly to a high-load diffuser cascade structure with locally non-smooth drag-reducing rib surfaces and its design method. Background Technology

[0002] Drag reduction technology has always been a focus, key area, and hot topic in the field of fluid mechanics. Common drag reduction methods mainly fall into two categories: active drag reduction and passive drag reduction. Active drag reduction includes wall vibration drag reduction, biomimetic jet drag reduction, fluid displacement, and air intake methods, while passive drag reduction mainly includes biomimetic non-smooth surface drag reduction, hydrophobic surface drag reduction, polymer drag reduction, and compliant wall drag reduction. Active drag reduction technology can actively adjust flow separation and turbulent eddies to varying degrees, thereby changing the motion state in the flow field. It has good applicability to different operating conditions, but requires additional devices and energy sources, which not only consumes extra energy but also increases design complexity. Passive drag reduction, on the other hand, does not require external application of additional momentum or energy; it only requires changing the surface geometry according to needs, and has advantages such as simple structure, low design cost, and ease of implementation. Regardless of whether it is active or passive drag reduction, the core focus is on rationally organizing the flow, reducing resistance, suppressing separation, and improving performance. For machines like air compressors, which are highly complex in design and operate under extremely harsh conditions, passive drag reduction methods with simple structures have great application potential.

[0003] The losses caused by resistance within the compressor have a significant impact on further improving overall performance. Therefore, reducing resistance is crucial for enhancing the performance of various blade profiles or the entire machine. The main types of resistance within the compressor include frictional resistance and pressure differential resistance. Frictional resistance further includes viscous frictional resistance and Reynolds stress. The diffuser cascade, as the basis for compressor blade design, is directly related to the compressor's performance. The performance requirements of modern advanced gas turbines have led to further increases in compressor load. Under the premise of a limited number of stages and minimizing weight increase, the increased stage load results in a higher single-stage pressure ratio and a smaller blade aspect ratio. This makes boundary layer separation more likely to occur within the compressor flow channel. This separation dramatically increases the Reynolds stress and pressure differential resistance of the airflow, and the resulting concentrated vortex systems cause significant mixing losses, leading to compressor blockage, reduced efficiency, and a series of other adverse effects. Therefore, taking effective measures to reduce various resistances within the compressor and further control or weaken flow separation and related losses is of great significance for further improving the performance of the compressor and even the gas turbine. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a high-load diffuser cascade structure with locally non-smooth drag-reducing rib surfaces and its design method. The invention primarily achieves passive drag reduction by adjusting the microstructure and arrangement of the non-smooth drag-reducing rib surfaces, thereby reducing vortex losses, mixing losses, and frictional losses between the airflow and the blade surface caused by separation, ultimately improving the diffuser capacity of the cascade.

[0005] The technical means employed in this invention are as follows:

[0006] A high-load diffuser cascade structure with locally non-smooth drag-reducing rib surfaces, wherein the diffuser cascade structure is a planar cascade structure or an annular cascade structure, and the planar cascade structure and the annular cascade structure are provided with non-smooth drag-reducing rib surfaces.

[0007] Furthermore, the planar blade cascade structure includes a planar blade cascade plate and a blade. The blade is fixedly connected to the planar blade cascade plate through a blade-shaped groove provided on the planar blade cascade plate. The non-smooth drag-reducing rib surface is arranged separately on the blade; or, the non-smooth drag-reducing rib surface is arranged separately on the planar blade cascade plate; or, the non-smooth drag-reducing rib surface is arranged simultaneously on the blade and the planar blade cascade plate.

[0008] The non-smooth drag-reducing rib surface is locally present on the blade and / or planar blade cascade plate.

[0009] Furthermore, the annular blade cascade structure includes a casing, a hub, and blades, with the non-smooth drag-reducing rib surface arranged separately on the blades; or, the non-smooth drag-reducing rib surface arranged separately on the casing or the hub; or, the non-smooth drag-reducing rib surface arranged simultaneously on the blades and the casing; or, the non-smooth drag-reducing rib surface arranged simultaneously on the blades and the hub; or, the non-smooth drag-reducing rib surface arranged simultaneously on the blades, the casing, and the hub.

[0010] The non-smooth drag-reducing rib surface is partially present on the blade, casing, or hub; or, the non-smooth drag-reducing rib surface is partially present on the blade and casing; or, the non-smooth drag-reducing rib surface is partially present on the blade and hub; or, the non-smooth drag-reducing rib surface is partially present on the casing and hub; or, the non-smooth drag-reducing rib surface is partially present on the blade, casing, and hub.

[0011] Furthermore, the non-smooth drag-reducing rib surface on the blade is a structure composed of an array of transverse microrib structures arranged at a 90° angle to the flow direction, and the non-smooth drag-reducing rib surface on the planar blade cascade plate is a structure composed of an array of transverse or flow-oriented microrib structures.

[0012] Furthermore, the non-smooth drag-reducing rib surface on the blade is a structure composed of an array of transverse microrib structures arranged at a 90° angle to the flow direction, and the non-smooth drag-reducing rib surface on the casing and hub is a structure composed of an array of transverse or flow-oriented microrib structures.

[0013] Furthermore, the cross-sectional shape of the microrib structure is a regular shape, a partially irregular shape, or an asymmetrical shape. The regular shape includes at least a rectangle, an isosceles trapezoid, a V-shape, and a circular arc. The partially irregular shape includes at least an angled V-shape, and the asymmetrical shape includes at least a higher order curve.

[0014] The microrib structure can be in the form of a groove or a protrusion.

[0015] The present invention also provides a design method for a high-load diffuser cascade structure with locally non-smooth drag-reducing rib surfaces, comprising the following steps:

[0016] S1. Determine the incoming flow conditions based on the selected compressor or blade cascade operating conditions, and base the flow on the dimensionless width w of the microrib structure. + Dimensionless height d + The actual dimensions of the microrib structure are determined by combining the incoming flow conditions, thus obtaining the width and depth of the microrib structure.

[0017] S2. Determine the cross-sectional shape of the microrib structure based on the width and depth of the microrib structure obtained in step S1;

[0018] S3. After determining the cross-sectional shape of the microrib structure, numerical calculations are performed to determine the spacing and coverage area. Combined with the corresponding position parameters, the final arrangement of the microrib structure on the planar blade cascade structure or the annular blade cascade structure is determined. The microrib structure is then arranged in an array to form the profile of the non-smooth drag-reducing rib surface. Then, using drafting software, a new blade profile with a non-smooth drag-reducing rib surface is generated in combination with the original blade profile. The corresponding blade with a non-smooth drag-reducing rib surface is generated using 3D drafting software. Combined with the blade installation angle and pitch parameters, the corresponding high-load diffuser cascade structure is obtained.

[0019] Furthermore, in step S1, the incoming flow conditions include at least the incoming flow Mach number and Reynolds number;

[0020] dimensionless width w + Dimensionless height d + Satisfy the following formula:

[0021]

[0022] In the formula, μ τ denoted as wall shear velocity, w as actual width, d as actual height, and v as kinematic viscosity;

[0023] Wall shear rate μ τ Satisfy the following formula:

[0024]

[0025] In the formula, Here, ρ is the near-wall shear stress, and ρ is the density.

[0026] Near-wall shear stress Satisfy the following formula:

[0027]

[0028] In the formula, V ∞ Let σ be the inflow velocity and σ be the near-wall shear stress.

[0029] The near-wall shear stress σ satisfies the following formula:

[0030] σ=0.37×(Re b ) 0.2 ;

[0031] In the formula, Re b is the Reynolds number, and b is the characteristic length, i.e., the chord length of the leaf shape;

[0032] Reynolds number Re b Satisfy the following formula:

[0033]

[0034] The width and depth of the final microrib structure satisfy the following formula:

[0035]

[0036] Furthermore, in step S2, the method for determining the cross-sectional shape of different types of microrib structures is as follows:

[0037] Once the rib width and depth are determined, the shape of a rectangular cross-section can be uniquely determined.

[0038] For V-shaped or trapezoidal cross-sectional shapes, it is necessary to determine the side wall angle γ, that is, the angle between the two sides of the apex of the V-shape, and the angle between the side and the base of the trapezoid.

[0039] Once the rib width and depth are known, the sidewall angle γ of the V-shaped section can be uniquely determined. Additionally, the hypotenuse length l needs to be determined, satisfying the following formula:

[0040]

[0041] Given the rib width and depth of an isosceles trapezoidal section, determine the sidewall angle γ, where 90 < γ < 180, and based on this, determine the upper base a and the leg length l, satisfying the following formula:

[0042]

[0043] a = w - 2lsin(γ - 90);

[0044] Given the rib width and depth, the radius of curvature r of a circular arc section can be calculated, satisfying the following formula:

[0045]

[0046] Based on the rectangular cross-section, a two-dimensional rectangular coordinate system is established with a vertex of the rectangle as the origin. Given the flow conditions w and d, the vertex of the V-shaped section moves along one side of the rectangular cross-section with length w and coordinates (x0, d), where x0 ≠ 0.5w. When x0 = 0.5w, it is a symmetrical V-shape. The coordinates of the other two vertices are (0, 0) and (w, 0). Based on this, the slopes k1 and k2 of the two sides and the sidewall angle γ are obtained, satisfying the following formula:

[0047]

[0048] In the formula, x0 is the x-coordinate of the vertex of the V-shaped deflection, that is, the distance of the vertex from the vertical axis.

[0049] Based on the circular arc cross-section, the cross-sectional shape can also be an irregular curved shape composed of multiple adjustable spline curves. The curve modeling methods include natural cubic spline curves, quadratic and cubic Bézier curves, and the specific parametric equations are as follows:

[0050] L i (x)=a i (xx i ) 3 +b i (xx i ) 2 +c i (xx i )+d i ;

[0051] G(t)=(1-t) 2 G0+2(1-t)tG1+t 2 G2;

[0052] H(t)=(1-t) 3 G0+3(1-t) 2 tG1+3(1-t)t 2 G2+t 2 G3;

[0053] In the formula, L i(x) is the governing equation of the natural cubic spline curve, where x is the x-coordinate (independent variable) of any point on the spline curve. i Let represent the x-coordinate of the data points, and be the control points of the spline curve. G(t) is the governing equation of the quadratic Bézier curve, H(t) is the governing equation of the cubic Bézier curve, and a i b i c i d i G0, G1, G2, and G3 are control points, and t is a parameter with a value range of [0,1].

[0054] Furthermore, in step S3, when the microrib structure on the non-smooth drag-reducing rib surface is arranged on the planar blade cascade plate, casing, or hub, the arrangement is in the same transverse direction as the blade rib, or in a flow direction similar to the airflow direction.

[0055] Compared with the prior art, the present invention has the following advantages:

[0056] 1. The drag reduction and efficiency enhancement structural design of the high-load compressor planar blade / annular blade cascade provided by the present invention, by adding non-smooth drag reduction rib surfaces composed of rib structure arrays on the surfaces of blades, cascades, casings and hubs, can control various resistances in the blade cascade channel, thereby reducing separation and vortex losses, mixing losses between the main flow and the backflow, and friction losses between the airflow and the blade wall caused by increased resistance, and further improving the performance of the compressor.

[0057] 2. The non-smooth drag-reducing rib surface design provided by this invention can control various resistances in the blade channel without the need for auxiliary devices, thereby achieving the control of boundary layer separation and vortex caused by resistance. It can also adjust the type of friction between the airflow and the blade wall to a certain extent. Furthermore, by changing the structure of the biomimetic ribs based on the existing blade shape, the difficulty of redesigning new blades is reduced.

[0058] 3. The biomimetic rib structure design provided by this invention slightly reduces or basically keeps the mass of the blade by changing the local structure, and has the advantages of simple structure and good adaptability to working conditions.

[0059] Based on the above reasons, this invention can be widely applied in fields such as drag reduction. Attached Figure Description

[0060] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0061] Figure 1 This is a schematic diagram of a high-load diffuser cascade structure with non-smooth drag-reducing blades and cascade plates in Embodiment 1 of the present invention.

[0062] Figure 2 This is a schematic diagram of a high-load diffuser cascade structure with blades having a non-smooth drag-reducing surface in Embodiment 1 of the present invention.

[0063] Figure 3 This is a schematic diagram of a high-load diffuser cascade structure with a non-smooth drag-reducing surface cascade plate in Embodiment 1 of the present invention.

[0064] Figure 4 This is a schematic diagram of a high-load diffuser cascade structure with a flow-oriented non-smooth drag-reducing surface cascade plate in Embodiment 1 of the present invention.

[0065] Figure 5 This is a schematic diagram of a two-dimensional airfoil with a non-smooth drag-reducing surface in a high-load diffuser cascade according to Embodiment 1 of the present invention.

[0066] Figure 6 This is a schematic diagram showing the position and parameters of the non-smooth drag-reducing surface relative to the airfoil in this invention.

[0067] Figure 7 This is a schematic diagram of the non-smooth drag-reducing surface structure and parameters of the present invention.

[0068] Figure 8 This is a schematic diagram of the annular blade cascade structure with non-smooth drag-reducing surface blades in Embodiment 2 of the present invention.

[0069] Figure 9 This is a schematic diagram of the high-load annular cascade blade structure with a non-smooth drag-reducing surface in Embodiment 2 of the present invention.

[0070] Figure 10 This is a schematic diagram of a high-load annular blade cascade structure with non-smooth drag-reducing blades and hub (transverse ribs) in Embodiment 2 of the present invention.

[0071] Figure 11 This is a schematic diagram of a high-load annular blade cascade structure with non-smooth drag-reducing blades and hub (flow ribs) in Embodiment 2 of the present invention.

[0072] In the figure: 1. Planar blade cascade; 2. Blade; 3. Non-smooth drag-reducing rib surface; 4. Casing; 5. Hub; 6. Suction surface; 7. Flow direction starting position of the non-smooth drag-reducing rib surface of the blade; 8. Flow direction ending position of the non-smooth drag-reducing rib surface of the blade. Detailed Implementation

[0073] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0074] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0075] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0076] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0077] Example 1

[0078] This invention provides a high-load diffuser cascade structure with locally non-smooth drag-reducing rib surfaces, specifically a compressor planar blade cascade structure with non-smooth drag-reducing rib surfaces, comprising a planar blade cascade plate 1, blades 2, and non-smooth drag-reducing rib surfaces 3. The non-smooth drag-reducing rib surfaces 3 can be individually arranged on the blades 2 (e.g., ...). Figure 2 As shown), it can also be arranged separately on the planar blade plate 1 (e.g. Figure 3 As shown), it can also be arranged simultaneously on blade 2 and planar blade cascade plate 1 (as shown). Figure 1 As shown in the figure, there are three possible combinations, and the non-smooth drag-reducing rib surface 3 is partially present on the blade 2 and / or the planar blade cascade plate 1. The blade 2 is fixed to the planar blade cascade plate 1 by air-shaped grooves provided on the planar blade cascade plate 1.

[0079] The specific structural form of the non-smooth drag-reducing rib surface 3 on the blade 2 mainly consists of an array of transverse microrib structures arranged at a 90° angle to the flow direction, i.e., the microrib structures are arranged parallel to the blade height direction. The specific structural form of the non-smooth drag-reducing rib surface 3 on the grid plate 1 can be composed of an array of transverse microrib structures arranged at a 90° angle to the flow direction, or it can be composed of an array of microrib structures arranged approximately in the flow direction. The cross-sectional shapes of the microrib structures mainly include relatively regular shapes such as rectangles, isosceles trapezoids, V-shapes, and arcs, as well as some irregular shapes such as angular V-shapes and higher-order curves, which are asymmetrical. The main parameters involved in the arrangement of the non-smooth drag-reducing rib surface 3 on the blade 2 surface include flow direction parameters and spanwise parameters. The rib structure parameters included in the non-smooth drag-reducing rib surface 3 mainly include rib width, width-to-depth ratio (or width-to-height ratio), and spacing (or density).

[0080] The design method or steps for the non-smooth drag-reducing rib surface 3 mentioned above are as follows:

[0081] First, determine the incoming flow conditions based on the selected compressor or blade cascade operating conditions, including the incoming Mach number and Reynolds number. Then, determine the dimensionless width w of the ribs. + Dimensionless height d + The actual dimensions of the ribs are determined by combining the definitions (1) and (2) with the incoming flow conditions.

[0082]

[0083] In the formula, μ τ denoted as the wall shear velocity, w as the actual width, d as the actual height, and v as the kinematic viscosity.

[0084] Wall shear rate μ τ The calculation formula is as follows:

[0085]

[0086] In the formula, Here, ρ represents the near-wall shear stress, and ρ represents the density.

[0087] Near-wall shear stress It can be obtained from the following formula:

[0088]

[0089] In the formula, V ∞ Let σ be the incoming flow velocity, and σ be the near-wall shear stress.

[0090] The near-wall shear stress σ is obtained by the following formula:

[0091] σ=0.37×(Re b ) 0.2 (5)

[0092] In the formula, Re b is the Reynolds number, and b is the characteristic length (i.e., the chord length of the leaf shape).

[0093] Reynolds number Re b It can be obtained from the following formula:

[0094]

[0095] The final formulas for calculating the rib width and depth are derived as follows:

[0096]

[0097] The actual dimensions of the ribs, width w and height (or depth) d, obtained from the above formulas, can be used to determine the structural form of the ribs by selecting a suitable cross-sectional shape. For V-shaped or trapezoidal cross-sections, it is also necessary to determine the sidewall angle γ, i.e., the angle between the two sides of the apex of the V-shape and the angle between the side and the bottom of the trapezoid. Different cross-sectional shapes can be selected according to the actual flow control effect, and the sidewall angle γ, as well as the rib width and height, can be adjusted to obtain the optimal biomimetic rib structure parameters for flow control.

[0098] Second, based on the basic dimensions of the ribs obtained in the previous step, such as rib width and depth, determine the specific rib cross-sectional shape. The methods for determining the cross-sectional shape of different types of ribs are as follows:

[0099] 1. Once the rib width and depth are determined, the shape of a rectangular section can be uniquely determined.

[0100] 2. The V-shaped section can be uniquely determined by the sidewall angle γ once the rib width and depth are known. Additionally, the length of the hypotenuse l needs to be determined. The specific formula is as follows:

[0101]

[0102] 3. For an isosceles trapezoidal section, after knowing the rib width and depth, it is also necessary to determine the side wall angle γ (90 < γ < 180), and then determine the upper base a and the leg length l based on this. The specific formula is as follows:

[0103]

[0104] a=w-2lsin(γ-90) (11)

[0105] For an isosceles trapezoidal cross section, the side wall angle γ needs to be determined based on specific numerical calculation results.

[0106] 4. For a circular arc section, given the rib width and depth, the radius of curvature r can be calculated using the following formula:

[0107]

[0108] 5. Based on the rectangular section, establish a two-dimensional rectangular coordinate system with a vertex of the rectangle as the origin. Then, based on the determined w and d of the incoming flow conditions, the vertex of the V-shaped section moves on one side of the rectangular section (side length w), and its coordinates are (x0, d), and x0 ≠ 0.5w (when x0 = 0.5w, it is a symmetrical V-shape). The coordinates of the other two vertices are (0, 0) and (w, 0). Based on this, the slopes k1 and k2 of the two sides can be obtained using the following formula, and the side wall angle γ can be further obtained.

[0109]

[0110] In the formula, x0 is the x-coordinate of the vertex of the V-shaped deflection, that is, the distance of the vertex from the vertical axis.

[0111] 6. Based on the circular arc cross-section, the cross-sectional shape can also be an irregular curved shape composed of multiple adjustable spline curves. The curve modeling methods can include natural cubic spline curves, quadratic and cubic Bézier curves, and their specific parametric equations are as follows:

[0112] L i (x)=a i (xx i ) 3 +b i (xx i ) 2 +c i (xx i )+d i (16)

[0113] G(t)=(1-t) 2 G0+2(1-t)tG1+t 2 G2 (17)

[0114] H(t)=(1-t) 3 G0+3(1-t) 2 tG1+3(1-t)t 2 G2+t 2 G3 (18)

[0115] In the formula, L i (x) is the governing equation of the natural cubic spline curve, where x is the x-coordinate (independent variable) of any point on the spline curve. i Let represent the x-coordinate of the data points, and be the control points of the spline curve. G(t) is the governing equation of the quadratic Bézier curve, H(t) is the governing equation of the cubic Bézier curve, and a i b i c i d i G0, G1, G2, and G3 are control points, and t is a parameter with a value range of [0,1].

[0116] For a natural cubic spline curve, the coefficient 'a' of each segment of the curve... i b i c i and d i It is determined by solving a system of linear equations, satisfying the continuity and boundary conditions of the curve.

[0117] Third, after determining the cross-sectional shape of the ribs, numerical calculations are needed to determine the spacing (or density) and coverage area, combined with corresponding positional parameters, to ultimately determine the arrangement of the ribs on the blade. These ribs are then arrayed and combined to form the profile of the non-smooth drag-reducing rib surface. Next, drafting software is used to generate a new blade profile with the non-smooth drag-reducing rib surface profile, based on the original blade profile. Further, 3D drafting software is used to generate the corresponding blade with the non-smooth drag-reducing rib surface. Finally, by combining parameters such as the airfoil installation angle and pitch, the corresponding grid structure can be obtained.

[0118] Similarly, the rib structures on the non-smooth drag-reducing rib surface described above can be arranged on the grid plate (i.e., endwall) in a certain form. The arrangement can be transverse, similar to the blade ribs, or flow-oriented, similar to the airflow direction. The transverse ribs on the non-smooth drag-reducing rib surface on the endwall are stretched or swept along the pitch direction by the rib parameters described above, with the specific length determined based on the corresponding numerical calculation results. The flow-oriented ribs on the non-smooth drag-reducing rib surface are stretched or swept along the suction surface airfoil from different flow-oriented positions by the rib parameters described above, with the specific data determined based on the numerical calculation results. The design method or determination method for the parameters, cross-sectional shape, and structure of the grid plate ribs is consistent with the above method.

[0119] The designed non-smooth drag-reducing rib surface structures can be either grooves or protrusions on the blade and endwall surfaces. Based on the above description, the resulting planar blade cascade with non-smooth drag-reducing rib surfaces can have the following structural forms: ① Non-smooth drag-reducing rib surfaces are arranged alone on the blade surface; ② Non-smooth drag-reducing rib surfaces are arranged alone on the endwall; ③ Non-smooth drag-reducing rib surfaces are arranged simultaneously on both the blade surface and the endwall. This corresponds to several different blade and cascade combination schemes: ① Non-smooth drag-reducing rib surface blades combined with prototype (smooth) cascades; ② Prototype (smooth) blades combined with non-smooth drag-reducing rib surface cascades; ③ Non-smooth drag-reducing rib surface blades combined with cascades. All non-smooth drag-reducing rib surface structures include both groove and protrusion types, while the arrangement of the cascade (or endwall) ribs can be either flow-oriented or transverse.

[0120] For example, a trapezoidal cross-section can be chosen for the rib structure. As shown in the attached figure, w is the rib width and d is the rib depth. The rib shape can be controlled by changing the rib width, rib depth, and sidewall angle.

[0121] The high-load annular cascade blade drag reduction and efficiency enhancement structural design provided by this invention can control various resistances in the stator channel by adding a non-smooth drag reduction rib surface composed of rib arrays on the blade surface. This reduces separation and vortex losses, mainstream and backflow mixing losses, and friction losses between airflow and blade wall caused by increased drag, thereby further improving compressor performance.

[0122] The non-smooth drag-reducing rib surface design provided by this invention can control various resistances within the blade channel without the need for auxiliary devices, thereby enabling the regulation of boundary layer separation and vortices caused by drag. It can also adjust the type of friction between the airflow and the blade wall to a certain extent. Furthermore, by modifying the structure of the biomimetic ribs based on existing blade shapes, the difficulty of redesigning new blades is reduced.

[0123] The biomimetic rib structure design provided by this invention slightly reduces or essentially maintains the mass of the annular cascade blades by changing the local structure, and has the advantages of simple structure and good adaptability to working conditions.

[0124] Example 2

[0125] In today's world, with the energy crisis and environmental issues becoming increasingly prominent, drag reduction and efficiency improvement have always been goals pursued by the fields of fluid machinery and fluid mechanics. The internal resistance of a compressor mainly originates from the frictional resistance generated by the contact between the airflow and the wall, and the pressure difference resistance induced by diffusion and airflow separation. Due to the highly complex and unsteady flow conditions inside the compressor, its frictional resistance includes viscous frictional resistance and Reynolds stress. Currently available flow drag reduction methods are mainly divided into two categories: active and passive. Active drag reduction measures include wall vibration drag reduction, biomimetic jet drag reduction, fluid displacement, and intake methods; passive drag reduction methods include biomimetic non-smooth surface drag reduction, hydrophobic surface drag reduction, polymer drag reduction, and compliant wall drag reduction. For high-precision, complex, and demanding mechanical equipment like compressors, active control methods often require additional adjustment mechanisms and power sources, increasing not only operating costs and structural complexity but also the difficulty and cost of compressor design. Therefore, the non-smooth surface drag reduction method, as one of the passive control methods, has shown great application potential in the field of compressors. This method has the advantages of simple structure, low design cost and easy implementation. It achieves drag reduction and efficiency improvement inside the compressor by only changing the microstructure of the compressor blades and channel walls. On the one hand, it can effectively control or weaken the channel vortex loss near the corner separation region and the resulting mixing loss. On the other hand, it can also reduce the various resistances and related losses generated in the blade channel, while keeping the blade mass slightly changed.

[0126] In the field of fluid machinery, reducing drag is crucial for minimizing energy consumption and improving performance. The performance requirements of future next-generation advanced gas turbines necessitate further increases in the load of their multi-stage axial compressors. Under the premise of a limited number of stages and minimizing weight increase, the increased stage load results in a higher single-stage pressure ratio and a smaller blade aspect ratio. The increased stage pressure ratio further amplifies the directional adverse pressure gradient and lateral pressure gradient within the blade passages, while the decreased blade aspect ratio leads to a thicker boundary layer on the endwalls. This thickened boundary layer is more prone to boundary layer separation under higher pressure gradients. Separation causes a sharp increase in Reynolds stress and differential drag, while also generating various concentrated vortices that induce strong airflow mixing effects, resulting in significant mixing losses. Furthermore, the low-energy fluid blockage caused by separation further contributes to compressor blockage and efficiency reduction, and in severe cases, even compressor stall and surge, posing a serious threat to the safe and stable operation of the compressor. Therefore, taking effective measures to reduce the various resistances caused by turbulence or separation inside the compressor, and weakening the flow separation and related losses inside the compressor, is of great significance for further improving the performance of the compressor and even the gas turbine.

[0127] This invention provides an annular blade cascade structure with locally non-smooth drag-reducing rib surfaces. By adjusting the structural form and arrangement of the biomimetic ribs, an annular blade cascade structure (stator structure) with biomimetic ribs is obtained, thereby weakening the corner separation intensity in the annular blade cascade channel (stator channel), reducing vortex losses, mixing losses and friction losses between the airflow and the blade surface caused by separation, thereby improving the diffusion capability of the annular blade cascade (stator), and ultimately improving the performance of the compressor.

[0128] The structure of the present invention is as follows Figure 8 The diagram shows a schematic of an annular blade cascade structure with non-smooth drag-reducing rib surfaces. It includes blades 2 (high-load annular blades, stator blades), non-smooth drag-reducing rib surfaces 3, a casing 4, a hub 5, and a suction surface 6. The non-smooth drag-reducing rib surface 3 can be arranged alone on blade 2, alone on casing 4 or hub 5, simultaneously on blade 2 and casing 4, simultaneously on blade 2 and hub 5, simultaneously on casing 4 and hub 5, or simultaneously on blade 2, casing 4, and hub 5—there are seven possible combinations. The placement of the non-smooth drag-reducing rib surface 3 depends on the specific flow conditions within the annular blade cascade. Furthermore, this non-smooth drag-reducing rib surface 3 is partially present on blade 2, casing 4, and hub 5. Figure 9 As shown, the two sides of the non-smooth drag-reducing rib surface 3 are the starting position 7 and the ending position 8 of the flow direction of the non-smooth drag-reducing rib surface of the blade, respectively.

[0129] The specific structural form of the non-smooth drag-reducing rib surface 3 on the blade 2 mainly consists of an array of transverse microrib structures arranged at a 90° angle to the flow direction, i.e., the microrib structures are arranged parallel to the height direction of the blade 2. The specific structural form of the non-smooth drag-reducing rib surface 3 on the casing 4 and hub 5 can be either an array of transverse microrib structures arranged at a 90° angle to the flow direction or an array of microrib structures arranged approximately in the flow direction. The cross-sectional shapes of the microrib structures mainly include relatively regular shapes such as rectangles, isosceles trapezoids, V-shapes, and arcs, as well as some irregular shapes such as angular V-shapes and higher-order curves, which are asymmetrical. The main parameters involved in the arrangement of the non-smooth drag-reducing rib surface 3 on the blade 2 surface include flow direction parameters and spanwise parameters. The rib structure parameters included in the non-smooth drag-reducing rib surface 3 mainly include rib width, width-to-depth ratio (or width-to-height ratio), and spacing (or density).

[0130] The design method or steps for the non-smooth drag-reducing rib surface 3 mentioned above are as follows:

[0131] First, determine the incoming flow conditions based on the selected compressor or blade cascade operating conditions, including the incoming Mach number and Reynolds number. Then, determine the dimensionless width w of the ribs. + Dimensionless height d+ The actual dimensions of the ribs are determined by combining the definitions (1) and (2) with the incoming flow conditions.

[0132]

[0133] In the formula, μ τ denoted as the wall shear velocity, w as the actual width, d as the actual height, and v as the kinematic viscosity.

[0134] Wall shear rate μ τ The calculation formula is as follows:

[0135]

[0136] In the formula, Here, ρ represents the near-wall shear stress, and ρ represents the density.

[0137] Near-wall shear stress It can be obtained from the following formula:

[0138]

[0139] In the formula, V ∞ Let σ be the incoming flow velocity, and σ be the near-wall shear stress.

[0140] The near-wall shear stress σ is obtained by the following formula:

[0141] σ=0.37×(Re b ) 0.2 (5)

[0142] In the formula, Re b is the Reynolds number, and b is the characteristic length (i.e., the chord length of the leaf shape).

[0143] Reynolds number Re b It can be obtained from the following formula:

[0144]

[0145] The final formulas for calculating the rib width and depth are derived as follows:

[0146]

[0147] The actual dimensions of the ribs, width w and height (or depth) d, obtained from the above formulas, can be used to determine the structural form of the ribs by selecting a suitable cross-sectional shape. For V-shaped or trapezoidal cross-sections, it is also necessary to determine the sidewall angle γ, i.e., the angle between the two sides of the apex of the V-shape and the angle between the side and the bottom of the trapezoid. Different cross-sectional shapes can be selected according to the actual flow control effect, and the sidewall angle γ, as well as the rib width and height, can be adjusted to obtain the optimal biomimetic rib structure parameters for flow control.

[0148] Second, based on the basic dimensions of the ribs obtained in the previous step, such as rib width and depth, determine the specific rib cross-sectional shape. The methods for determining the cross-sectional shape of different types of ribs are as follows:

[0149] 1. Once the rib width and depth are determined, the shape of a rectangular section can be uniquely determined.

[0150] 2. The V-shaped section can be uniquely determined by the sidewall angle γ once the rib width and depth are known. Additionally, the length of the hypotenuse l needs to be determined. The specific formula is as follows:

[0151]

[0152] 3. For an isosceles trapezoidal section, after knowing the rib width and depth, it is also necessary to determine the side wall angle γ (90 < γ < 180), and then determine the upper base a and the leg length l based on this. The specific formula is as follows:

[0153]

[0154] a=w-2lsin(γ-90) (11)

[0155] For an isosceles trapezoidal cross section, the side wall angle γ needs to be determined based on specific numerical calculation results.

[0156] 4. For a circular arc section, given the rib width and depth, the radius of curvature r can be calculated using the following formula:

[0157]

[0158] 5. Based on the rectangular section, establish a two-dimensional rectangular coordinate system with a vertex of the rectangle as the origin. Then, based on the determined w and d of the incoming flow conditions, the vertex of the V-shaped section moves on one side of the rectangular section (side length w), and its coordinates are (x0, d), and x0 ≠ 0.5w (when x0 = 0.5w, it is a symmetrical V-shape). The coordinates of the other two vertices are (0, 0) and (w, 0). Based on this, the slopes k1 and k2 of the two sides can be obtained using the following formula, and the side wall angle γ can be further obtained.

[0159]

[0160] In the formula, x0 is the x-coordinate of the vertex of the V-shaped deflection, that is, the distance of the vertex from the vertical axis.

[0161] 6. Based on the circular arc cross-section, the cross-sectional shape can also be an irregular curved shape composed of multiple adjustable spline curves. The curve modeling methods can include natural cubic spline curves, quadratic and cubic Bézier curves, and their specific parametric equations are as follows:

[0162] L i (x)=ai (xx i ) 3 +b i (xx i ) 2 +c i (xx i )+d i (16)

[0163] G(t)=(1-t) 2 G0+2(1-t)tG1+t 2 G2 (17)

[0164] H(t)=(1-t) 3 G0+3(1-t) 2 tG1+3(1-t)t 2 G2+t 2 G3 (18)

[0165] In the formula, L i (x) is the governing equation of the natural cubic spline curve, where x is the x-coordinate (independent variable) of any point on the spline curve. i Let represent the x-coordinate of the data points, and be the control points of the spline curve. G(t) is the governing equation of the quadratic Bézier curve, H(t) is the governing equation of the cubic Bézier curve, and a i b i c i d i G0, G1, G2, and G3 are control points, and t is a parameter with a value range of [0,1].

[0166] For a natural cubic spline curve, the coefficient 'a' of each segment of the curve... i b i c i and d i It is determined by solving a system of linear equations, satisfying the continuity and boundary conditions of the curve.

[0167] Third, after determining the cross-sectional shape of the ribs, numerical calculations are needed to determine the spacing (or density) and coverage area, combined with corresponding positional parameters, to ultimately determine the arrangement of the ribs on the blade. These ribs are then arrayed and combined to form the profile of the non-smooth drag-reducing rib surface. Next, drafting software is used to generate a new blade profile with the non-smooth drag-reducing rib surface profile, based on the original blade profile. Further, 3D drafting software is used to generate the corresponding blade with the non-smooth drag-reducing rib surface. Finally, by combining parameters such as the blade mounting angle and pitch, the corresponding hub structure can be obtained.

[0168] Similarly, the rib structures on the non-smooth drag-reducing rib surface described above can be arranged on the hub (i.e., end wall) or casing in a certain form. The arrangement can be transverse, similar to the blade ribs, or flow-direction similar to the airflow direction. The transverse ribs on the non-smooth drag-reducing rib surface of the hub or casing are stretched or swept along the pitch direction by the rib parameters described above, with the specific length determined based on the corresponding numerical calculation results. The flow-direction ribs on the non-smooth drag-reducing rib surface are stretched or swept along the suction surface blade profile from different flow-direction positions by the rib parameters described above, with the specific data determined based on the numerical calculation results. The design method or determination method for the parameters, cross-sectional shape, and structure of the grid ribs is consistent with the above method.

[0169] The designed non-smooth drag-reducing rib surface structures can all be based on grooves on the blade and hub (or casing) surfaces, or on protrusions on the blade and hub (or casing) surfaces. Based on the above description, the annular blade cascade with non-smooth drag-reducing rib surfaces can have the following structural forms: ① Non-smooth drag-reducing rib surfaces are arranged alone on the blade surface; ② Non-smooth drag-reducing rib surfaces are arranged alone on the hub or casing; ③ Non-smooth drag-reducing rib surfaces are arranged simultaneously on the blade surface and the hub (or casing); ④ Non-smooth drag-reducing rib surfaces are arranged simultaneously on the casing and the hub; ⑤ Non-smooth drag-reducing rib surfaces are arranged simultaneously on the blade surface, the hub, and the casing. This corresponds to several different blade and hub (or casing) combination schemes: ① combination of non-smooth drag-reducing rib surface blades with prototype (smooth) hubs and casings; ② combination of prototype (smooth) blades with non-smooth drag-reducing rib surface hubs (or casings); ③ combination of non-smooth drag-reducing rib surface blades with hubs (or casings); ④ combination of non-smooth drag-reducing rib surface casings and hubs; ⑤ combination of non-smooth drag-reducing rib surface blades, hubs, and casings. All non-smooth drag-reducing rib surface structures include both grooved and raised types, while the hub (or casing) ribs have two arrangement forms: flow-oriented and transverse.

[0170] For example, a trapezoidal cross-section can be chosen for the rib structure. As shown in the attached figure, w is the rib width and d is the rib depth. The rib shape can be controlled by changing the rib width, rib depth, and sidewall angle.

[0171] The high-load annular cascade blade drag reduction and efficiency enhancement structural design provided by this invention can control various resistances in the stator channel by adding a non-smooth drag reduction rib surface composed of rib arrays on the blade surface. This reduces separation and vortex losses, mainstream and backflow mixing losses, and friction losses between airflow and blade wall caused by increased drag, thereby further improving compressor performance.

[0172] The non-smooth drag-reducing rib surface design provided by this invention can control various resistances within the blade channel without the need for auxiliary devices, thereby enabling the regulation of boundary layer separation and vortices caused by drag. It can also adjust the type of friction between the airflow and the blade wall to a certain extent. Furthermore, by modifying the structure of the biomimetic ribs based on existing blade shapes, the difficulty of redesigning new blades is reduced.

[0173] The biomimetic rib structure design provided by this invention slightly reduces or essentially maintains the mass of the annular cascade blades by changing the local structure, and has the advantages of simple structure and good adaptability to working conditions.

[0174] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A design method for a high-load diffuser cascade structure with locally non-smooth drag-reducing rib surfaces, characterized in that, The diffuser cascade structure is a planar cascade structure or an annular cascade structure, and the planar cascade structure and the annular cascade structure are provided with non-smooth drag-reducing rib surfaces (3). The design method for the high-load diffuser cascade structure with locally non-smooth drag-reducing rib surfaces includes the following steps: S1. Determine the incoming flow conditions based on the selected compressor or cascade operating conditions, and base the analysis on the dimensionless width of the microrib structure. w + Dimensionless height d + The actual dimensions of the microrib structure are determined by combining the incoming flow conditions, thus obtaining the width and depth of the microrib structure. S2. Determine the cross-sectional shape of the microrib structure based on the width and depth of the microrib structure obtained in step S1; S3. After the cross-sectional shape of the microrib structure is determined, numerical calculations are performed to determine the interval and coverage range. Combined with the corresponding position parameters, the arrangement of the microrib structure on the planar blade cascade structure or the annular blade cascade structure is finally determined. The microrib structure is arranged in an array to form the profile of the non-smooth drag-reducing rib surface (3). Then, the original blade profile is combined with the drawing software to generate a new blade profile with the non-smooth drag-reducing rib surface (3) profile. The corresponding blade with the non-smooth drag-reducing rib surface (3) is generated by the three-dimensional drawing software. The corresponding high-load diffuser cascade structure is obtained by combining the blade installation angle and pitch parameters. In step S1, the incoming flow conditions include at least the incoming flow Mach number and Reynolds number; Dimensionless width w + Dimensionless height d + Satisfy the following formula: ； ； In the formula, The wall shear rate, w This is the actual width. d This is the actual height. v Kinematic viscosity; Wall shear rate Satisfy the following formula: ； In the formula, Near-wall shear stress, Density; Near-wall shear stress Satisfy the following formula: ； In the formula, For the incoming flow velocity, σ This refers to the near-wall shear stress. Near-wall shear stress σ Satisfy the following formula: ； In the formula, Re b The Reynolds number is... b The characteristic length is the leaf chord length; Reynolds number Re b Satisfy the following formula: ； The width and depth of the final microrib structure satisfy the following formula: ； 。 2. The design method for a high-load diffuser cascade structure with locally non-smooth drag-reducing rib surfaces according to claim 1, characterized in that, The planar blade cascade structure includes a planar blade cascade plate (1) and a blade (2). The blade (2) is fixedly connected to the planar blade cascade plate (1) through a blade-shaped groove provided on the planar blade cascade plate (1). The non-smooth drag-reducing rib surface (3) is arranged separately on the blade (2); or, the non-smooth drag-reducing rib surface (3) is arranged separately on the planar blade cascade plate (1); or, the non-smooth drag-reducing rib surface (3) is arranged on both the blade (2) and the planar blade cascade plate (1). The non-smooth drag-reducing rib surface (3) is partially present on the blade (2) and / or the planar blade cascade plate (1).

3. The design method for a high-load diffuser cascade structure with locally non-smooth drag-reducing rib surface according to claim 1, characterized in that, The annular blade structure includes a casing (4), a hub (5), and blades (2). The non-smooth drag-reducing rib surface (3) is arranged separately on the blade (2); or, the non-smooth drag-reducing rib surface (3) is arranged separately on the casing (4) or the hub (5); or, the non-smooth drag-reducing rib surface (3) is arranged on both the blade (2) and the casing (4); or, the non-smooth drag-reducing rib surface (3) is arranged on both the blade (2) and the hub (5); or, the non-smooth drag-reducing rib surface (3) is arranged on both the casing (4) and the hub (5); or, the non-smooth drag-reducing rib surface (3) is arranged on the blade (2), the casing (4), and the hub (5). The non-smooth drag-reducing rib surface (3) is partially present on the blade (2), the casing (4), or the hub (5); or, the non-smooth drag-reducing rib surface (3) is partially present on the blade (2) and the casing (4); or, the non-smooth drag-reducing rib surface (3) is partially present on the blade (2) and the hub (5); or, the non-smooth drag-reducing rib surface (3) is partially present on the casing (4) and the hub (5); or, the non-smooth drag-reducing rib surface (3) is partially present on the blade (2), the casing (4), and the hub (5).

4. The design method for a high-load diffuser cascade structure with locally non-smooth drag-reducing rib surfaces according to claim 2, characterized in that, The non-smooth drag-reducing rib surface (3) on the blade (2) is a structure composed of an array of transverse microrib structures arranged at a 90° angle to the flow direction, and the non-smooth drag-reducing rib surface (3) on the planar blade grating plate (1) is a structure composed of an array of transverse or flow-direction microrib structures.

5. The design method for a high-load diffuser cascade structure with locally non-smooth drag-reducing rib surface according to claim 3, characterized in that, The non-smooth drag-reducing rib surface (3) on the blade (2) is a structure composed of a transverse micro rib structure array arranged at a 90° angle with the flow direction, and the non-smooth drag-reducing rib surface (3) on the casing (4) and hub (5) is a structure composed of a transverse or flow direction micro rib structure array arranged.

6. The design method for a high-load diffuser cascade structure with locally non-smooth drag-reducing rib surface according to claim 1, 4, or 5, characterized in that, The cross-sectional shape of the microrib structure is a regular shape, a partially irregular shape, or an asymmetrical shape. The regular shape includes at least a rectangle, an isosceles trapezoid, a V-shape, and a circular arc. The partially irregular shape includes at least an angled V-shape. The asymmetrical shape includes at least a higher order curve. The microrib structure can be in the form of a groove or a protrusion.

7. The design method for a high-load diffuser cascade structure with locally non-smooth drag-reducing rib surface according to claim 1, characterized in that, In step S2, the method for determining the cross-sectional shape of different types of microrib structures is as follows: Once the rib width and depth are determined, the shape of a rectangular section can be uniquely determined. For V-shaped or trapezoidal cross-sectional shapes, the sidewall angles need to be determined. γ That is, the angle between the two sides of the V-shaped apex, and the angle between the side and the base of the trapezoid; Given the rib width and depth, the sidewall angle of the V-shaped section... γ This can uniquely determine the location; additionally, the length of the hypotenuse needs to be determined. l It satisfies the following formula: ； Determine the sidewall angles of an isosceles trapezoidal cross section given the rib width and depth. γ 90 γ <180, and determine the upper base accordingly. a Waist length l It satisfies the following formula: ； ； Given the rib width and depth, the radius of curvature of a circular arc section can be calculated. r It satisfies the following formula: ； Based on the rectangular section, a two-dimensional rectangular coordinate system is established with a vertex of the rectangle as the origin for the V-shaped section. Then, according to the already determined inflow conditions... w and d Based on this, the vertex of the V-shape moves along one side of the rectangular cross-section, with a side length of... w The coordinates are ( x 0, d ),and x 0 ≠ 0.5 w , x 0 = 0.5 w The shape is a symmetrical V-shape, with the coordinates of the other two vertices being (0, 0) and (0, 0). w ,0), and from this, the slopes of the two sides can be obtained. k 1. k 2 and sidewall angle γ It satisfies the following formula: ； ； ； In the formula, The x-coordinate of the vertex of the V-shaped deflection is the distance from the vertex to the y-axis. Based on the circular arc cross-section, the cross-sectional shape can also be an irregular curved shape composed of multiple adjustable spline curves. The curve modeling methods include natural cubic spline curves, quadratic and cubic Bézier curves, and the specific parametric equations are as follows: ； ； ； In the formula, The governing equations for a natural cubic spline curve are... Let x be the x-coordinate of any point on the spline curve. The x-coordinates of the data points are the control points of the spline curve; The governing equations for a quadratic Bézier curve are given. The governing equations for cubic Bézier curves are given. a i , b i , c i , d i For coefficients, G 0、 G 1. G 2. G 3 is the control point. t This is a parameter, and its value range is [0,1].

8. The design method for a high-load diffuser cascade structure with locally non-smooth drag-reducing rib surface according to claim 1, characterized in that, In step S3, when the microrib structure of the non-smooth drag-reducing rib surface (3) is arranged on the planar blade cascade plate (1), casing (4) or hub (5), the arrangement is the same as the transverse direction of the blade (2) rib, or the flow direction similar to the airflow direction.

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