Energy storage air turbine low-Mach-number last-stage long blade based on load optimization

Abstract

The invention belongs to the field of compressed air energy storage turbines, discloses an energy storage air turbine low-Mach-number last-stage long blade based on load optimization, and aims to remarkably improve the pneumatic performance of turbine blades so as to meet the specific high-performance requirement of an air energy storage system for turbine equipment. According to the method, the blade is divided into three areas, and the load coefficient distribution form in each area is subjected to optimization design, so that secondary flow loss and mixing loss at the root of the blade, shock wave loss and steam leakage loss at the top of the blade and the like are reduced, and the comprehensive aerodynamic performance of the air turbine blade is improved. According to the low-Mach-number last-stage long blade, the load coefficient is in a special distribution rule along the blade height, root and top loads can be effectively reduced, comprehensive loss is reduced, the strength performance is improved, the top relative Mach number is controlled, the overall aerodynamic performance is improved, and the low-Mach-number last-stage long blade is particularly suitable for a high-power and large-volume-flow energy storage air turbine, and has a wide application prospect. And the economical efficiency and the safety of the unit are greatly improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of compressed air energy storage turbines, and particularly relates to a low Mach number last stage long blade of an energy storage air turbine based on load optimization. BACKGROUND

[0002] Compressed air energy storage technology has advantages of green, low carbon, economic efficiency, safety and reliability, and has become an important part of new power systems. By the end of 2023, the market size of compressed air energy storage in China was 1.365 billion yuan, and it is expected to exceed 5.9 billion yuan in 2025. In recent years, the single machine power of compressed air energy storage turbines has developed from kilowatt level to megawatt level and even to hundreds of megawatts. Among the already put into operation units, the maximum single machine power reaches 300 MW, and there is a trend of continuous increase in the future.

[0003] Air turbine is the core equipment of compressed air energy storage power generation system. The last stage blade in the air turbine has a large enthalpy drop ratio and long blade, and must have higher aerodynamic performance to improve the unit efficiency and high strength performance to resist the centrifugal force, so as to ensure the long-term efficient and stable operation of the air turbine and the energy storage system.

[0004] The gradual increase of single machine power leads to the increase of air turbine low pressure cylinder volume flow, the increase of last stage blade height, the increase of blade load and relative Mach number, and the gradual increase of aerodynamic performance difference between blade root and top, which puts forward higher requirements for the aerodynamic and structural performance of the last stage blade.

[0005] The energy storage air turbine is generally started and stopped daily, and the exhaust pressure is atmospheric pressure. The working medium, operation mode and back pressure are very different from conventional thermal power and nuclear power steam turbines, which leads to the fact that the last stage blade cannot be used universally. Therefore, the last stage blade must be customized and developed for the energy storage air turbine.

[0006] The selection of load coefficient is directly related to the aerodynamic performance of turbine blade. The load coefficient of traditional reaction blade is defined as: ; in the formula: is the enthalpy drop value, and U is the peripheral velocity at the blade mean diameter, that is, the load coefficient is selected based on the blade mean diameter. The last stage blade of the energy storage air turbine has the characteristics of large flow rate, long blade and large flow area, and the aerodynamic characteristics of the root, middle and top positions are quite different. In addition, the long blade structure also brings about large stress and torsional deformation. Therefore, the conventional load coefficient design concept is no longer applicable to the long blade of the energy storage air turbine. SUMMARY

[0007] In view of the deficiencies of the prior art, the present application provides a load-optimized long blade for the last stage of a low-Mach number energy storage air turbine, which aims to improve the aerodynamic performance of the blade by dividing the long blade into three regions and optimizing the load coefficient distribution in each region to reduce the secondary flow loss and mixing loss at the root of the blade, the shock loss and steam leakage loss at the top of the blade, and further improve the aerodynamic performance of the blade.

[0008] To achieve the object of the present application, the technical solution adopted is: A load-optimized long blade for the last stage of a low-Mach number energy storage air turbine, which is composed of a plurality of two-dimensional blade profiles, the two-dimensional blade profiles are continuously and smoothly stacked in the height direction to ensure good transition of aerodynamic and structural performance.

[0009] Among them, the axial width Cx of the two-dimensional blade profile is equal; the installation angle θ decreases from the root to the top along the height direction; the relative chord length Bx increases from the root to the top along the height direction based on the two-dimensional blade profile at the root; the relative maximum thickness Lx monotonically decreases from the root to the top along the height direction; and the relative area monotonically decreases along the height direction.

[0010] As a preferred, the two-dimensional blade profile is 5.

[0011] Further, the long blade of the last stage is divided into three blade regions according to its aerodynamic and strength characteristics in different relative heights h / H , which are the root region, the middle region, and the top region; wherein, H is the blade height, h is the height of the two-dimensional blade profile, is the relative height of the key two-dimensional section for dividing the blade region.

[0012] By optimizing the distribution of the aerodynamic load coefficient along the height, the overall loss is reduced, the top Mach number is controlled, and the aerodynamic efficiency is improved.

[0013] Further, the distribution of the load coefficient of the three blade regions along the height direction satisfies the following rules: (1) when , in this region, , that is, the load coefficient remains constant along the height direction; (2) when , , the value range of is 0.8~1.0, which is determined by a quadratic function about the relative height h / H . ; (3) when , , the value range of is 0.4~1.0, and satisfies the relationship: ; wherein, the relative load coefficient is the ratio of the difference between the load coefficient of the target region of the blade and the load coefficient of the middle region of the blade; wherein, The specific value of needs to be specifically limited after comprehensive consideration according to the specific design requirements of the aerodynamic efficiency, power and flow capacity of the target blade type; wherein, the coefficient is a pre-set constant, and the specific value is related to the load coefficient and height of the blade; wherein the coefficient , , is a pre-set constant, and the specific value is related to the load coefficient and height of the blade.

[0014] The secondary flow loss, end loss and leakage loss of the blade have high correlation with the blade height. The regions of the blades of different heights that affect the end secondary flow loss and leakage loss are different. With the increase of the relative blade height, the proportion of the middle main flow area increases, and the proportion of the root and top secondary flow area correspondingly decreases. Therefore, with the increase of the radial height ratio H / ( H+Dm ), the relative blade height of the key section is smaller.

[0015] According to the relative blade height H / (H+Dm) of the key section of the blade of different radial height ratios , the value is limited, and further: (1) when H / (H+Dm) ≤0.08, ; (2) when 0.08 H / (H+Dm) <0.16, ; (3) when H / (H+Dm) ≥0.16, .

[0016] wherein ，H / ( H+Dm ) is the radial height ratio of the blade; Dm is the root diameter of the blade.

[0017] wherein, the characteristic parameters of the blade mainly include the blade height H , the height where the two-dimensional blade type is located h , and the root diameter of the blade Dmaxial width of two-dimensional airfoil Cx Installation angle of two-dimensional blades θ chord length of a two-dimensional leaf Bx The maximum thickness of a two-dimensional airfoil Lx Relative leaf height at the location of the key section for leaf region division .

[0018] The above technical solution has the following beneficial effects: 1. Divide the last-stage long blade into three blade regions along the blade height direction: root, middle, and top. Control the load coefficient distribution pattern in each region in a targeted manner to make the load distribution more compatible with the loss characteristics and strength characteristics at different relative blade heights, effectively improving the economy and safety of the last-stage long blade.

[0019] 2. ~ Within the relative leaf height range, that is, the middle area of ​​the leaf, Aspect ratio of blade diameter to height H / (H+Dm) Figure 1 The losses in the middle blade region mainly include airfoil losses (including friction losses) and potential weak shock wave losses, and the aerodynamic efficiency tends to be the highest in this region. Using a larger and more uniformly distributed load factor in this region allows more heat-work conversion to occur in the high-efficiency middle region, improving the overall efficiency of the long last-stage blades.

[0020] 3. Below the relative blade height, in the blade root region, blade losses include mixing losses, secondary flow losses, endwall losses, and friction losses. The closer to 0% relative blade height, the greater the mixing and secondary flow losses. By employing a smaller load coefficient distribution pattern that increases parabolically along the blade height in this region (smaller at the root), the load can be transferred from the high-loss area at the root to the high-efficiency area in the upper middle section, releasing the root flow potential and further improving the overall aerodynamic efficiency of the long, final-stage blades. Furthermore, since the blade's strength characteristics mainly depend on the root, reducing the root load is beneficial for improving the strength performance of the long, final-stage blades and ensuring safety.

[0021] 4. Within the region above the relative blade height, i.e., the blade tip region, blade losses include shock wave losses, leakage losses, secondary flow losses, and friction losses. The closer to 100% relative blade height, the greater the shock wave losses, leakage losses, and secondary flow losses become. Adopting a smaller load coefficient distribution pattern that decreases parabolically along the blade height (smaller at the tip) in this region can effectively reduce the lateral pressure gradient in the tip region, significantly suppress the intensity and development of leakage flow in the tip region, and the reduction of the tip load helps control the relative Mach number at the tip, avoid the risk of shock wave losses, and comprehensively improve the aerodynamic performance of long last-stage blades.

[0022] The low Mach number last-stage long blade provided by this invention exhibits a unique distribution pattern of load coefficient along the blade height, which can effectively reduce root and top loads, reduce overall losses, improve strength performance, control the relative Mach number at the top, and improve overall aerodynamic performance. It is particularly suitable for high-power, high-volume flow energy storage air turbines, significantly improving the economy and safety of the unit. Attached Figure Description

[0023] Figure 2 This is a schematic diagram of the low Mach number last stage long blade of the energy storage air turbine based on load optimization according to the present invention; Figure 3 This is a schematic diagram of the two-dimensional blade shape of the last stage long blade of the present invention; Figure 4 This is a schematic diagram of the two-dimensional leaf shape feature parameters of the present invention; h / H The relative load factor of this invention Relative leaf height Figure 5 Corresponding curve; H / (H+Dm) The relative blade height at the location of the key section for dividing the blade region in this invention. Aspect ratio of blade diameter to height Cx- θ- Corresponding curve; In the diagram: 1-blade, 2-two-dimensional leaf shape. H- Leaf height, Bx- Axial width, Lx- Installation angle, Figure 1 String length, Figure 2 Maximum thickness. Detailed Implementation

[0024] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0025] Example 1 like Figure 3 As shown, a low Mach number last-stage long blade for an energy storage air turbine based on load optimization is constructed by continuously and smoothly stacking five two-dimensional blade profiles along the blade height direction from the root to the tip, with the center of gravity aligned. The five two-dimensional blade profiles are denoted by AA, BB, CC, DD, and EE, and are located at 0%. 50% And 100% relative to the leaf height, and The two-dimensional leaf shape at the relative height of the leaf divides the leaf blade into three regions, namely: area, Region and area.

[0026] likeCx As shown, the centroids of the five two-dimensional airfoils coincide. The least squares optimization technique is used, combined with the characteristics of the Bezier curve, to fit the contour line of the two-dimensional airfoil section and generate a feature section composed of 28 discrete points (X, Y).

[0027] Table 1 shows the outline of the AA two-dimensional airfoil using the coordinates (X, Y) of the following discrete points.

[0028] Table 2 shows the outline of the BB two-dimensional airfoil using the coordinates (X, Y) of the following discrete points.

[0029] Table 3 shows the contour lines of the CC two-dimensional airfoil using the coordinates (X, Y) of the following discrete points.

[0030] Table 4 shows the outline of the DD two-dimensional airfoil using the coordinates (X, Y) of the following discrete points.

[0031] Table 5 shows the outline of the EE two-dimensional airfoil using the coordinates (X, Y) of the following discrete points.

[0032] like θ As shown, the characteristic parameters of the two-dimensional airfoil include axial width. Bx Installation angle Lx String length Cx and maximum thickness θ Axial width of 5 two-dimensional airfoils Figure 4 Equal, installation angle h / H The angle decreases from 46° to 32.3° from AA to EE; based on the AA two-dimensional blade shape, the relative chord length increases from 1.0 to 1.18 along the blade height direction; the relative maximum thickness decreases monotonically from 1.0 to 0.64 along the blade height direction; and the relative area decreases monotonically from 1.0 to 0.76 along the blade height direction.

[0033] like Figure 5 As shown, relative load factor Relative leaf height H / (H+Dm) The corresponding curve, where, ;when hour, ; when hour, The value ranges from 0.8 to 1.0, and satisfies the following relationship: , , , In this embodiment, the constant is a pre-set value. , , The values ​​are -1.623, 1.182, and 0.803; when hour, The value ranges from 0.4 to 1.0, and satisfies the following relationship: , , , In this embodiment, the constant is a pre-set value. , , The values ​​are -5.017, 6.988, and -1.432.

[0034] For long blades, the relative Mach number at the tip is higher than at the root, resulting in greater aerodynamic losses. Therefore, the tip region of the blade ( The load factor curve of the root region shows a higher load factor than that of the root region. A faster downward trend.

[0035] like H / (H+Dm) As shown, the relative blade height at the location of the key section for blade region division. Aspect ratio of blade diameter to height H / (H+Dm) H / (H+Dm) Corresponding curve; the ratio of the blade region designed for blade load distribution to the diameter-to-height ratio of the blade of this invention. H / (H+Dm) Highly correlated ， Among them when ​ When ≤0.08, =40%; when 0.08 < ​ When <0.16, =30%; when ​ When ≥0.16, =20%.

[0036] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A load-optimized energy-storage air turbine low-Mach number last stage long blade consisting of several two-dimensional blade profiles, characterized in that: The two-dimensional leaf shape is formed by continuous and smooth stacking along the leaf height direction at the center of gravity; the final stage long blades are constructed according to different relative leaf heights. The aerodynamic and strength characteristics requirements within the specified range are divided into three blade regions, namely... area, area, Area; the H The blade height; h The height of the two-dimensional airfoil; The relative blade height position of the key two-dimensional cross-section for segmenting the blade region.

2. The load-optimized energy-based air turbine low-Mach number last stage long blade according to claim 1, characterized in that: the load coefficient of the three blade regions distribution along the blade height direction: (1) when , in this region, i.e. the loading coefficient remains constant along the spanwise direction;​ (2) when , , the value range is 0.8~1.0, and satisfies the relationship ; (3) when , , The value range is 0.4-1.0, and the relationship is satisfied ; The relative load coefficient is the ratio of the difference between the load coefficient of the target region of the blade and the load coefficient of the middle region of the blade; the is specifically defined according to the aerodynamic efficiency, the power capacity and the flow capacity of the target blade profile; the , , is a pre-set constant, and the specific value is related to the load coefficient and the specific height of the blade; the , , is a pre-set constant, and the specific value is related to the load coefficient and the specific height of the blade.

3. The load-optimized energy-based air turbine low-Mach number last stage long blade according to claim 1, characterized in that: H / (H+Dm) ≤0.08, the ; 0.08 H / (H+Dm) <0.16, the ; H / (H+ Dm) ≥0.16, the ; the H / ( H+Dm ) is a ratio of the blade height to the blade diameter; the Dm is a root diameter of the blade.

4. The load-based optimization based energy storage air turbine low Mach number last stage long blade of claim 1, wherein: The axial width Cx of the two-dimensional airfoil is equal.

5. The load optimized energy based air turbine low Mach number last stage long blade of claim 1, wherein: The installation angle θ of the two-dimensional airfoil decreases from the root to the tip along the blade height direction.

6. The load-based optimization based energy storage air turbine low Mach number last stage long blade of claim 1, wherein: The relative chord length Bx of the two-dimensional airfoil increases from the root to the tip along the blade height direction, with the root of the two-dimensional airfoil as the reference.

7. The load optimization based energy storage air turbine low Mach number last stage long blade of claim 1, wherein: The relative maximum thickness Lx of the two-dimensional airfoil monotonically decreases from the root to the tip along the blade height direction.

8. The load optimized energy based air turbine low Mach number last stage long blade of claim 1, wherein: The relative area of the two-dimensional airfoil monotonically decreases along the blade height direction.

9. The load optimized energy based air turbine low Mach number last stage long blade of claim 1, wherein: The two-dimensional airfoil is 5.

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