Turbine compressor blade capable of preventing airflow separation

Abstract

The invention relates to the technical field of blades, in particular to a turbine compressor blade capable of preventing airflow separation. The blade comprises a plurality of protrusions distributed on the suction surface of the blade, a connecting line of boundary layer separation points on the suction surface of the blade in the spreading direction of the blade serves as a datum line, and all the protrusions are located on the datum line. The main body structure of the blade is not changed, a complex external control device is not needed, the structural strength of the blade is guaranteed, the blade is easy to machine, flowing can be effectively improved, and engineering application is facilitated.

Description

Technical Field

[0001] This invention relates to the field of blade technology, specifically a turbine compressor blade designed to prevent airflow separation. Background Technology

[0002] Turbine compressors, as an important type of compressor, are widely used in micro gas turbines and Brayton cycle power generation systems due to their advantages such as compact structure, small size, light weight, high single-stage pressure ratio, and simple manufacturing process.

[0003] The aerodynamic performance of turbine compressor blades directly determines the overall efficiency, pressure ratio, and stable operating range of the compressor. On the suction side of the blades, the accelerated airflow often faces a strong adverse pressure gradient (i.e., static pressure increases along the flow direction), leading to boundary layer separation. This separation generates large-scale vortices and flow blockage, causing significant flow losses and reducing pressure ratio and efficiency. In severe cases, separation can induce rotating stall or even surge, posing a serious threat to the safe operation of the entire compressor unit.

[0004] Traditional methods for suppressing boundary layer separation mainly fall into two categories: First, optimizing blade profiles from the aerodynamic design stage to reduce the adverse pressure gradient. This is illustrated in Chinese Patent Publication No. CN115163553A, titled "Impeller Assembly, Centrifugal Impeller, and Steam Compressor." These methods often involve creating grooves / holes on the blade surface or altering the blade structure, increasing manufacturing difficulty and weakening blade structural strength, making them difficult to apply in practical engineering. Second, employing complex active or passive flow control devices, such as boundary layer suction, treatment casings, and adjustable guide vanes, significantly increases system complexity, weight, and manufacturing costs, thus requiring further solutions. Summary of the Invention

[0005] In order to avoid and overcome the technical problems existing in the prior art, the present invention provides a turbine compressor blade that prevents airflow separation. It does not change the main structure of the blade and does not require a complex external control device. It ensures the structural strength and ease of processing of the blade, and can effectively improve the flow, making it convenient for engineering applications.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A turbine compressor blade for preventing airflow separation includes several protrusions distributed on the suction surface of the blade, with the line connecting the boundary layer separation points on the suction surface as the reference line, and all protrusions located on the reference line.

[0007] As a further aspect of the present invention: the protrusion is cylindrical or conical with its axis perpendicular to the suction surface of the blade.

[0008] As a further aspect of the present invention: the axial height of the protrusion is... The boundary layer displacement thickness at the baseline on the blade is ,in, .

[0009] As a further aspect of the present invention: the length of the blade in the span direction is taken as... The diameter of the bottom of the protrusion is The number of protrusions is set to ,in, ,when At that time, all protrusions are arranged at equal intervals along the length of the baseline, and the distance between the axes of adjacent protrusions is... ,in, .

[0010] As a further embodiment of the present invention: the intervals between the leaf root and leaf tip along the leaf spread direction and the axis of their respective nearest protrusions are all the same.

[0011] As a further aspect of the present invention, the protrusion is made of steel.

[0012] As a further aspect of the present invention, the protrusion is made of an elastic carbon fiber composite material, so that the protrusion can undergo elastic deformation under air pressure.

[0013] Compared with the prior art, the beneficial effects of the present invention are: 1. By defining the line connecting the boundary layer separation points on the suction surface as a baseline, and fixing several protrusions along this baseline on the blade's suction surface, the structural strength of the blade is ensured while also facilitating manufacturing. Simultaneously, this effectively promotes the transition of the blade surface boundary layer from laminar to turbulent flow in the critical region, solving the problem of separation zones easily forming near the blade outlet under high pressure ratio and high speed conditions in traditional compressor blades. Furthermore, utilizing the stronger momentum exchange capacity of the turbulent boundary layer effectively resists the adverse pressure gradient, preventing or delaying airflow separation in the compressor blades, significantly improving the compressor's pressure ratio and efficiency.

[0014] 2. The preferred shape of the protrusion is a cylinder or cone with its axis perpendicular to the suction surface of the blade at its location. These two geometric shapes are simple to manufacture, provide uniform stress distribution, and can effectively induce the desired flow vortex structure.

[0015] 3. Height of the protrusion Based on the boundary layer displacement thickness at the blade baseline To determine, among which, This height ensures that the top of the protrusion extends into part of the mainstream outside the boundary layer, drawing in high-energy airflow, while avoiding excessive height that would cause unnecessary shape drag and wake loss.

[0016] 4. Based on the above-mentioned layout concept, this application also provides a complete design system for the geometric parameters of the protrusions. The protrusion height h is directly correlated with the boundary layer thickness δ, ensuring a scientifically reasonable disturbance depth. Simultaneously, the number of protrusions n, especially the spacing s between adjacent protrusions, is further correlated with the protrusion height h, ensuring the formation of a uniform, continuous, and sustainable "vortex barrier" along the entire blade span direction. This achieves globally optimal collaborative control, avoiding the blindness of traditional designs that rely on trial and error or local optimization.

[0017] 5. Depending on the required operating conditions, the protrusion can be made of stainless steel and fixed to a preset position on the suction surface of the blade using a precision welding process. This method is convenient and quick, and offers excellent high-temperature resistance, erosion resistance, and mechanical strength. Alternatively, the protrusion can be made of elastic carbon fiber composite material, which can be bonded to the blade. When airflow passes over it, the pressure difference between the windward and leeward sides of the protrusion causes it to undergo slight elastic bending deformation. This deformation has two advantages: first, under low-load conditions, the deformation is small, resulting in moderate interference with the airflow and avoiding excessive drag; second, under high-load conditions and with increased separation tendency, the stronger airflow impact intensifies the deformation of the protrusion, and the change in its attitude can enhance the generation intensity of vortices or change the direction of the vortices, thereby dynamically adapting to the need to suppress separation under different operating conditions and broadening the stable operating range of the blade. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of the present invention.

[0019] Figure 2 This is a schematic diagram of the flow field distribution on the blade surface when the protrusion is not installed in this invention.

[0020] Figure 3 This is a schematic diagram of the flow field distribution on the blade surface in Embodiment 1 of the present invention.

[0021] Figure 4 This is a schematic diagram of the flow field distribution on the blade surface in Embodiment 2 of the present invention.

[0022] Figure 5 This is a schematic diagram of the flow field distribution on the blade surface in Embodiment 3 of the present invention.

[0023] Figure 6 This is a schematic diagram of the flow field distribution on the blade surface at the midpoint of two adjacent protrusions in Embodiment 1 of the present invention.

[0024] Figure 7 This is a schematic diagram of the flow field distribution on the blade surface at the midpoint of two adjacent protrusions in Embodiment 4 of the present invention.

[0025] Figure 8This is a schematic diagram of the flow field distribution on the blade surface at the midpoint of two adjacent protrusions in Embodiment 5 of the present invention.

[0026] In the image: 1. Blade; 2. Protrusion; 3. Leading edge. Detailed Implementation

[0027] 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. 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.

[0028] For ease of understanding, the specific structure and operation of the present invention will be further described below with reference to the accompanying drawings: The specific structure of this invention is as follows: Figure 1 As shown, its main structure includes a blade 1 and several protrusions 2 fixed on the suction surface of the blade 1.

[0029] It should be noted that the term "blade span direction" refers to the direction of blade 1 from the blade root to the blade tip; "suction surface" refers to the side of the blade with lower static pressure when it is working; "boundary layer separation point" is the location where the boundary layer separates along the blade chord length direction. There is a boundary layer separation point at any location in the blade span direction. It can be determined under specific design conditions by numerical simulation (CFD) or experimental means (such as oil flow display, hot wire measurement). This determination method is a well-known existing technology.

[0030] Specifically, such as Figure 1 As shown, on the suction surface of blade 1, the line connecting the boundary layer separation points on the suction surface of blade 1 serves as the baseline, and all protrusions 2 are located on this baseline. The placement of these protrusions 2 effectively promotes the transition of the boundary layer on the blade 1 surface from laminar to turbulent flow in the critical region, solving the problem of separation zones easily forming near the blade outlet under high pressure ratio and high speed conditions in traditional compressor blades. Furthermore, by utilizing the stronger momentum exchange capacity of the turbulent boundary layer, it effectively resists the adverse pressure gradient, preventing or delaying airflow separation in compressor blade 1, significantly improving the compressor's pressure ratio and efficiency.

[0031] Furthermore, it is worth mentioning that the structure of the protrusion 2 eliminates the need for slotting on the surface of the blade 1, maintaining the original structural integrity of the blade 1 and avoiding the flow resistance that may be caused by the traditional flow splitting structure, thereby further improving the overall efficiency of the compressor.

[0032] In practice, the protrusion 2 is preferably a cylinder or cone with its axis perpendicular to the suction surface of the blade 1 at its location. These two geometric shapes are simple to process, have uniform stress distribution, and can effectively induce the required vortex structure.

[0033] In further implementation, the height of protrusion 2 Based on the boundary layer displacement thickness at the baseline To determine, among which, This height ensures that the apex of the protrusion extends into the mainstream outside the boundary layer, drawing in high-energy airflow, while avoiding excessive height that would cause unnecessary shape drag and wake loss. The bottom diameter of protrusion 2... Based on strength requirements and processing capabilities, typically Less than .

[0034] In addition, the number of protrusions 2 Based on the length of the blade in the span direction , height of protrusion and bottom diameter Calculate, where, ,when At that time, all protrusions 2 are arranged at equal intervals along the length of the baseline, and the distance between the axes of adjacent protrusions 2 is... ,in, .

[0035] For height is A single protrusion 2, when the medium flows through it, will generate a pair of protrusions with a strength of The reverse vortex, in which This is the magnitude of the outer edge velocity of the boundary layer, which is the maximum velocity along the normal at the separation point of the blade's suction surface. As the eddy develops downstream, spanwise diffusion also occurs, induced laterally by a single eddy. The velocity of the flow field at a distance is approximately Therefore, the flow field between the two cylinders or spikes (at a distance of 0.5 meters from the vortex) is... ) speed .when This means that the eddy-induced flow can overcome the momentum deficit in the boundary layer caused by the adverse pressure gradient, from which we can obtain... ,Right now However, to avoid rapid dissipation caused by two adjacent vortices being too close together, an initial spacing between them is required. Not less than In summary Should be between arrive The results were verified in subsequent embodiments. At the same time, this spacing design ensures that the generated vortex can cover the blade suction surface in the spanwise direction before it develops and decays downstream, forming a continuous "vortex wall" to continuously and stably suppress separation.

[0036] Furthermore, the distances between the leaf root and leaf tip of leaf 1 and the axis of their nearest protrusion 2 along the leaf spread direction are all the same; these distances are denoted as follows: Figure 1 shown ,Should Based on the length of the blade in the span direction The distance between the axis of the adjacent protrusion 2 This is determined to ensure that flow in the leaf root and leaf tip wall regions is also controlled.

[0037] In actual implementation, the protrusion 2 is preferably made of stainless steel and is fixed to a preset position on the suction surface of the blade 1 by precision welding process, which has excellent high temperature resistance, erosion resistance and mechanical strength.

[0038] In another embodiment, the protrusion 2 is made of elastic carbon fiber composite material and can be fixed to the blade 1 by adhesive bonding. When airflow passes over it, the pressure difference acting on the windward and leeward sides of the protrusion 2 causes the protrusion 2 to undergo slight elastic bending deformation. This deformation has two advantages: first, under low-load conditions, the deformation of the protrusion is small, and the interference with the airflow is moderate, avoiding excessive drag; second, under high-load conditions and when the separation trend is enhanced, the stronger airflow impact intensifies the deformation of the protrusion, and the change in its attitude can enhance the generation intensity of vortices or change the direction of vortices, thereby dynamically adapting to the need to suppress separation under different operating conditions and widening the stable operating range of the blade 1.

[0039] Working principle

[0040] When airflow passes over the suction surface of the blade equipped with protrusions 2, each protrusion 2 acts as a disturbance source. Because of these protrusions 2, the boundary layer on the blade surface transitions from laminar to turbulent flow prematurely in the critical region. This turbulence continuously draws and transports the high-energy mainstream air outside the blade's suction surface downwards into the low-energy boundary layer near the wall. The injection of high-energy airflow replenishes the boundary layer's momentum, significantly enhancing its ability to resist the downstream adverse pressure gradient, thereby effectively delaying boundary layer separation or disrupting existing separation zones and promoting reattachment of the airflow.

[0041] In addition, the vortex array generated by multiple protrusions 2 arranged at equal intervals along the blade span direction constitutes a flow control domain, ensuring the uniformity and consistency of the separation suppression effect throughout the entire blade span.

[0042] During implementation: Protrusion 2 is a 2mm diameter steel cylinder; Blade 1 is an axial compressor blade; Blade 1 has a conventional airfoil structure; Blade 1 has a chord length of 80mm and a span of 90mm; the angle between the medium's flow direction and the chord line of Blade 1 is 10°; and the flow velocity is 30m / s. The velocity distribution was obtained through flow field simulation calculations, as follows: Figure 2As shown, observation reveals that the location of airflow separation is at a distance of 3 from the leading edge of blade 1 (the position of leading edge 3 is as follows). Figure 1 The boundary layer displacement thickness is calculated using the velocity distribution along multiple normal lines (straight lines perpendicular to the blade surface) within the range of 45mm-48mm (as shown in the diagram) to accurately locate the separation point. and boundary layer momentum thickness The location of the boundary layer separation point in this application is determined based on the ratio of the two. Among them, the velocity distribution on the aforementioned normal and The calculation results are shown in Tables 1-4, including the boundary layer displacement thickness. and boundary layer momentum thickness Solve according to the following formulas:

[0043]

[0044] In the formula: It is the magnitude of the velocity at the outer edge of the boundary layer, which is the maximum velocity along the normal. The normal line extends from the suction surface to... The number of nodes between them; It is the first on the legal line The distance from each node to the suction surface; It is the first on the legal line Fluid velocity at each node.

[0045] Table 1. Velocity distribution along the normal at 45 mm from the leading edge of the blade and Calculation results

[0046] Table 2. Velocity distribution along the normal at a distance of 46 mm from the leading edge of the blade and Calculation results

[0047]

[0048] Table 3. Velocity distribution along the normal at a distance of 47 mm from the leading edge of the blade and Calculation results

[0049]

[0050] Table 4. Velocity distribution along the normal at 48 mm from the leading edge of the blade and Calculation results

[0051]

[0052] Based on the above calculations, at a distance of 47 mm from the leading edge of the blade... If this value is greater than 3.5 and closest to 3.5, then this is the separation point of the suction surface of blade 1 (i.e., the baseline). Therefore, the height of protrusion 2 is taken as Because the blade span is 90mm, and It should be every Set a protrusion 2, and based on the number of protrusions 2 Calculation formula ,get Rounding down gives Therefore, five protrusions need to be evenly distributed along the spread of leaf 1, with the leaf root and leaf tip spaced apart from the nearest protrusion 2 along their axis. It is 4mm.

[0053] In Example 1, according to the above-described calculation structure, five cylindrical protrusions 2, each 2 mm in diameter and 4.1 mm in height, are arranged. The interval between adjacent protrusions 2 is 16.4 mm, and the distances from the axes of the two edge protrusions 2 to the blade tip and blade root are 4 mm, respectively. Based on the determined location of the boundary layer separation point, and after determining the baseline, all protrusions 2 are welded and fixed to the suction surface of the blade 1 along the length of the baseline, according to the arrangement of protrusions 2 in this application. The flow field distribution on the surface of the blade 1 is as follows: Figure 3 As shown, the flow field distribution on the surface of blade 1 at the midpoint of two adjacent protrusions 2 is as follows: Figure 5 As shown, after installing the array of cylindrical protrusions 2, the airflow separation on the suction surface of blade 1 is significantly suppressed, as can be seen from the flow field distribution.

[0054] Example 2 differs from Example 1 in that the welding position of protrusion 2 is located between the baseline and the leading edge 3, while the size and spacing of protrusion 2 remain consistent with Example 1. In this example, the flow field distribution on the surface of blade 1 is as follows: Figure 4 As shown, airflow separation cannot be completely eliminated, and vortex backflow caused by airflow separation still exists at the tail of blade 1.

[0055] Example 3 differs from Example 1 in that the welding position of protrusion 2 is located between the baseline and the trailing edge, while the dimensions and spacing of protrusion 2 remain consistent with those in Example 1. In this example, the flow field distribution on the surface of blade 1 is as follows: Figure 5 As shown, the airflow separation downstream of blade 1 is eliminated, but it will cause airflow separation upstream, that is, a vortex backflow caused by airflow separation is generated before the protrusion 2.

[0056] Example 4 differs from Example 1 in that the interval s between adjacent protrusions 2 is adjusted to... , that is s ,at this time, ,Right now Rounding down gives Therefore, five protrusions need to be evenly distributed along the spread of leaf 1, with the leaf root and leaf tip spaced apart from the nearest protrusion 2 along their axis. The thickness is 1.95 mm. Based on the determined location of the boundary layer separation point, and after determining the baseline, all protrusions 2 are welded and fixed to the suction surface of the blade 1 along the length of the baseline, according to the arrangement of protrusions 2 in this application. In this embodiment, the flow field on the surface of the blade 1 at the midpoint of two adjacent protrusions 2 is as follows: Figure 7 As shown, the vortex generated by the cylindrical disturbance cannot cover the entire flow field along the spanwise direction, resulting in airflow separation at the rear end of the blade.

[0057] Example 5 differs from Example 1 in that the interval s between adjacent protrusions 2 is adjusted to... , that is s ,at this time, ,Right now Rounding down gives Therefore, five protrusions need to be evenly distributed along the spread of leaf 1, with the leaf root and leaf tip spaced apart from the nearest protrusion 2 along their axis. The length is 8.1 mm. Based on the determined location of the boundary layer separation point, and after determining the baseline, all protrusions 2 are welded and fixed to the suction surface of the blade 1 along the length of the baseline, according to the arrangement of protrusions 2 in this application. In this embodiment, the flow field on the surface of the blade 1 at the midpoint of two adjacent protrusions 2 is as follows: Figure 8 As shown, the two vortices generated by the two adjacent protrusions 2 are too close together, causing the vortex structure to dissipate quickly. Airflow separation also occurs at the rear end of blade 1.

[0058] Therefore, it can be seen that, according to the arrangement of the protrusions 2 protected by this application in Embodiment 1, the protrusion array has the best effect on preventing airflow separation.

[0059] Of course, those skilled in the art will recognize that the present invention is not limited to the details of the exemplary embodiments described above, but also includes the same or similar structures that can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0060] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0061] The technologies, shapes, and structures not described in detail in this invention are all known technologies.

Claims

1. A turbine compressor blade for preventing airflow separation, characterized in that, It includes several protrusions (2) distributed on the suction surface of the blade (1), with the line connecting the boundary layer separation points on the suction surface of the blade (1) as the reference line, and all protrusions (2) are located on the reference line.

2. The turbine compressor blade for preventing airflow separation according to claim 1, characterized in that, The protrusion (2) is cylindrical or conical with its axis perpendicular to the suction surface of the blade (1).

3. A turbine compressor blade for preventing airflow separation according to claim 2, characterized in that, Taking the axial height of protrusion (2) as The boundary layer displacement thickness at the baseline on blade (1) is ,in, .

4. A turbine compressor blade for preventing airflow separation according to claim 3, characterized in that, The length of the leaf (1) in the leaf span direction is taken as The bottom diameter of protrusion (2) is The number of protrusions (2) is set to ,in, ,when At that time, all the protrusions (2) are arranged at equal intervals along the length direction of the baseline, and the distance between the axes of adjacent protrusions (2) is ,in, .

5. A turbine compressor blade for preventing airflow separation according to claim 4, characterized in that, The leaf root and leaf tip along the leaf spread direction are spaced at the same distance from the axis of their nearest protrusion (2).

6. A turbine compressor blade for preventing airflow separation according to any one of claims 1-5, characterized in that, The protrusion (2) is made of steel.

7. A turbine compressor blade for preventing airflow separation according to any one of claims 1-5, characterized in that, The protrusion (2) is an elastic carbon fiber composite material, so that the protrusion (2) can undergo elastic deformation under air pressure.

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