Anti-cavitation turbine blade

Abstract

The utility model discloses a kind of anti-cavitation steam turbine blades, including sequentially connected and integrally formed blade, blade root, blade crown;Multiple flow channel grooves from blade root to blade crown are arranged on the front and back of blade, tail end and blade crown inner and outwardly open through hole intercommunication. Flow channel groove is arranged along blade span camber line / broken line, along blade height, the slope of flow guide is increased, main flow / branch flow is parallelly connected and converges, groove section and size are gradually increased from bottom to top;Through hole is arranged in row along blade crown arc, axis is towards radial outer side and is provided with chamfer / horn mouth;Flow channel groove can be equipped with microtexture and hydrophobic / hard coating, front and back mirror image arrangement and with profile line tangential angle 10°~30°. The utility model forms "collecting-guiding and draining-throwing out" continuous passage, shortens condensate residence time, inhibits water droplet erosion and cavitation, maintains aerodynamic stability, improves blade life and unit efficiency, and is suitable for batch manufacturing.

Description

Technical Field

[0001] This utility model relates to the field of turbine blade technology, specifically to an anti-cavitation turbine blade. Background Technology

[0002] When steam turbine blades operate in the medium and low pressure stages, steam expands and cools, producing condensed water droplets. These droplets form thin liquid films or micro-droplet clusters on both sides of the blade profile, and under the influence of high relative velocities, they cause water droplet erosion and localized cavitation. Long-term operation will lead to surface pitting, groove expansion, airfoil distortion, and decreased efficiency. To reduce droplet retention and impact energy, engineering practices generally require a continuous path on the blade surface for rapid collection, directional drainage, and reliable ejection, while simultaneously considering erosion resistance and aerodynamic stability.

[0003] Existing technologies mainly fall into the following categories: (1) Smooth surface + corrosion-resistant coating. A hard or hydrophobic coating is deposited on the entire or partial surface of the blade to improve its erosion resistance. This type of solution can suppress initial wear to a certain extent, but it does not establish an effective droplet discharge channel. The water film is still retained on the surface, and the coating is prone to failure and peeling under cyclic impact, resulting in high maintenance costs.

[0004] (2) Local groove / pit texture. Short grooves or dot matrix textures are made on the pressure or suction surface of the blade to induce microflow. Due to the limited depth and length of the grooves, it is difficult to continuously transport the root droplets to the canopy area, the drainage link is interrupted, and new retention zones are easily formed on the surface; at the same time, setting it on one side will cause uneven drainage on both sides.

[0005] (3) Drainage holes or edge openings in the leaf crown. Several drainage holes or edge notches are set in the leaf crown to eject liquid by centrifugal force. Since most of these designs are not connected to the flow guiding structure on the leaf body, the liquid absorption capacity of the holes is weak, and the back pressure inside the holes is high and easy to block, resulting in limited drainage efficiency; the sharp edge of the hole also has an adverse effect on local aerodynamics.

[0006] In summary, existing technologies generally suffer from the following problems: lack of a continuous guide and discharge link from the blade root to the blade crown, resulting in long droplet residence time on the profile surface and difficulty in suppressing the initiation and spread of erosion / cavitation; guide grooves and through holes are mostly point-like or short-range structures, failing to form a main-branch flow coordination and gradually increasing slope acceleration mechanism along the flow path, resulting in insufficient confluence and anti-clogging capabilities; the blade crown through holes are not matched to the centrifugal discharge direction, leading to prominent problems of backflow and reattachment, and the sharp edges of the orifices are aerodynamically detrimental. Therefore, there is an urgent need for a method that constructs mirrored or near-mirror-shaped vein-like flow channels on both sides of the blade, and employs a geometric structure with gradually increasing cross-section and slope in the blade height direction, so that droplets are rapidly collected from the blade root side and stably transported to the blade crown; simultaneously, a collection cavity—directional through-hole—is formed on the inner side of the blade crown, combined with chamfering / flaring to achieve low-resistance discharge; further, a composite protection of microtexture and hydrophobic / hard coating is applied to balance aerodynamic stability, erosion / cavitation resistance, and manufacturability, thereby improving the long-term service reliability and efficiency of turbine blades. Utility Model Content

[0007] This utility model aims to solve one of the technical problems existing in the prior art or related technologies.

[0008] Therefore, the technical solution adopted by this utility model is as follows: a cavitation-resistant turbine blade, comprising an integrally formed blade, a blade root, and a blade crown connected in sequence; several flow channel grooves extending from the blade root to the blade crown along the blade height direction are provided on both sides of the blade, and the tail end of each flow channel groove is connected to a through hole provided in the blade crown and opening to the outside of the blade crown; each flow channel groove is arranged in an arc or zigzag shape in the blade span direction, and forms a gradually increasing guide slope from bottom to top with the blade profile, forming a continuous guide system from the blade root to the blade crown.

[0009] This invention features multiple flow channels on both sides of the blade, with each flow channel extending from the blade root to the blade crown and communicating with the through hole. The flow channels are arranged in an arc or zigzag shape in the blade span direction, forming a guide slope that gradually increases along the blade height direction and the blade profile.

[0010] In a preferred example, the guide slope increases monotonically from 1° to 6° from the blade root to the blade crown, and the groove spacing is arranged equidistantly or in segments with unequal spacing according to the pressure distribution of the profile.

[0011] Specific technical effects: Establishing a stable collection and drainage channel from root to crown, shortening droplet residence time, reducing the probability of erosion and cavitation initiation, and maintaining the aerodynamic stability of the profile.

[0012] In a preferred example, the flow channel is further configured such that: the flow channel includes a main flow channel located in the middle of the blade and a number of branch flow channels that intersect with it in the blade span direction; the branch flow channels are connected in parallel or merged with the main flow channel at one end near the blade crown and then communicate with the corresponding through hole.

[0013] Specific technical effects: Increase the collection area and reduce flow pulsation in a single tank, improve drainage throughput and anti-clogging ability, and keep the drainage path continuous under different operating conditions.

[0014] In a preferred example, the flow channel is further configured such that the cross-section of the channel is a rounded trapezoid, arc, or V-shape, the width and depth of the channel gradually increase from the blade root to the blade crown, and the two sides of the channel opening are provided with transition rounded corners.

[0015] Specific technical effects: The root quickly gathers droplets, the crown forms an expanded main channel, the friction resistance is reduced, the drainage is smoother, and the disturbance to the boundary layer is reduced.

[0016] In a preferred example, the through holes are arranged in rows along the arc of the leaf crown, with the axis of the through holes facing the radially outward direction of the blade rotation, and a chamfer or flared opening is provided at the port near the outer surface of the leaf crown.

[0017] Specific technical effects: Directional discharge in the same direction as centrifugation increases outflow velocity and suppresses backflow and secondary adhesion, reducing local erosion at the leaf edge.

[0018] In a preferred example, the configuration is further as follows: micro-ribs or micro-dimples array micro-textures arranged along the channel direction are provided on the bottom and sidewall surfaces of the channel, with a pitch of 50-μm and a height or depth of 10-80 μm.

[0019] Specific technical effects: Microtexture provides directional wetting and microscale air cushion effect, reduces adhesion work and retention probability, stabilizes liquid film migration, and improves erosion resistance and cavitation resistance.

[0020] In a preferred example, the surface of the flow channel or the surface of the blade near the blade crown is further configured to have a hydrophobic coating or a hard corrosion-resistant coating applied, the coating covering at least the bottom of the flow channel and the adjacent area of ​​the channel opening.

[0021] Specific technical effects: The hard layer resists solid-liquid erosion, and the hydrophobic layer reduces wetting and deposition. The two work together to delay wear and pitting expansion, and improve long-term service life.

[0022] In a preferred example, the flow channel grooves are arranged in a mirror or near-mirror configuration on the front and back sides of the blade, and the angle between each flow channel groove and the tangential direction of the blade profile is 10° to 30°.

[0023] Specific technical effects: Maintaining the symmetry of drainage and force on both sides, ensuring the formation of a stable tangential velocity component under different angles of attack, and reducing the generation of new retention zones and new erosion hotspots.

[0024] The beneficial effects achieved by this utility model are as follows: 1. In this invention, flow channels extending from the blade root to the blade crown are provided on both sides of the blade, and are connected to the outside through through holes at the blade crown, forming a continuous channel of "collection-guidance-discharge". Each flow channel is arranged in an arc or zigzag shape in the blade span direction, and the guiding slope increases from bottom to top. The main flow channel and the branch flow channel are connected / merged in parallel at the blade crown end and then discharged radially outward through the through holes, thereby significantly shortening the residence time of condensate on the blade surface and reducing the probability of water droplet erosion and cavitation. At the same time, the cross-section of the channel gradually changes from small to large and is provided with a bell mouth or chamfer at the through hole end, so that the disturbance to the boundary layer during the discharge process is smaller, maintaining the aerodynamic stability of the blade and the efficiency of the unit.

[0025] 2. In this invention, the bottom and sidewalls of the flow channel can be textured, and the blade crown area and the surface of the flow channel can be coated with hydrophobic and hard corrosion-resistant coatings, forming a composite protection system of "micro-scale viscosity reduction + surface erosion resistance"; the mirror (or near-mirror) arrangement and angle range design of the front and back sides take into account the consistency of the drainage path and strength requirements under different working conditions. Therefore, it can effectively improve cavitation and erosion resistance during long-term operation, slow down material wear and pitting corrosion expansion, extend blade life and reduce maintenance costs. Furthermore, the integrated structure and mature manufacturing method facilitate mass production and application. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the overall structure of one embodiment of the present utility model; Figure 2 This is a schematic diagram of the back structure of a blade according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the leaf crown surface structure according to an embodiment of the present invention.

[0027] Figure label: 100, blade; 200, leaf root; 300, leaf crown; 110, flow channel; 310, through hole. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to specific embodiments and accompanying drawings. It should be noted that, unless otherwise specified, the embodiments and features of the present utility model can be combined with each other.

[0029] It should be understood that these descriptions are merely exemplary and not intended to limit the scope of this invention.

[0030] The following describes, with reference to the accompanying drawings, some embodiments of the present invention, providing an anti-cavitation turbine blade.

[0031] Combination Figures 1-3As shown, this utility model provides an anti-cavitation turbine blade, comprising a blade 100, a blade root 200, and a blade crown 300 connected sequentially and integrally formed. The blade 100 has a spatially torsional aerodynamic profile. Both the front and back surfaces of the blade 100 are provided with several flow channel grooves 110 extending from the blade root 200 towards the blade crown 300 along the blade height direction. The tail end of each flow channel groove 110 communicates with a through hole 310 located inside the blade crown 300 and opening to the outside of the blade crown 300. Each flow channel groove 110 is arranged in an arc or zigzag shape in the blade span direction, forming a guiding slope with the blade profile along the blade height direction. The guiding slope gradually increases from the end near the blade root 200 to the end near the blade crown 300, providing an accelerated drainage path for droplets / condensate from the root to the crown during operation.

[0032] In this embodiment, the blade 100, blade root 200 and blade crown 300 can be integrally machined after precision casting and heat treatment; the flow channel grooves 110 are arranged at equal intervals along the profile or at unequal intervals according to the local pressure distribution of the profile, with a typical number of 3-7 grooves.

[0033] Technical effect: Under the action of steam, condensate is collected on the surface of blade 100 by guide groove 110 and accelerated upward along the guide slope to the blade crown 300. It is then thrown out through the through hole 310 under the action of centrifugal force, which significantly shortens the residence time of droplets and reduces the causes of water droplet erosion and cavitation.

[0034] In this embodiment, the flow channel 110 includes a main flow channel located in the middle of the blade 100 and several branch flow channels that intersect with the main flow channel in the blade span direction. The branch flow channels connect in parallel with or merge with the main flow channel near the blade crown 300 at their ends along the blade height direction, and then communicate with the corresponding through-holes 310. To avoid abrupt changes in aerodynamic performance, the branch flow channels use a rounded transition (R0.5-1.5 mm) at their junctions with the main flow channel.

[0035] Specific technical effects: Parallel / merging of multiple tanks increases the collection area and reduces flow pulsation in a single tank, promotes stable upward movement of the thin liquid film, and reduces stagnation and secondary adhesion on the surface.

[0036] In this embodiment, the cross-section of the flow channel 110 can be a rounded trapezoid, arc or V-shaped structure; the width and depth of the flow channel 110 gradually increase from the leaf root 200 end to the leaf crown 300 end.

[0037] Furthermore, the apex angle of the V-groove is 60°–100°; the radius of the arc-shaped groove increases linearly or piecewise linearly with the blade height.

[0038] Specific technical effects: The gradual change in cross-section and size improves the flow capacity and traction capability along the flow path, which can quickly gather droplets at the root and form a stable main drainage channel at the crown, reducing disturbance to the aerodynamic boundary layer.

[0039] In this embodiment, the through holes 310 are arranged in rows along the arc direction of the blade crown 300, with the hole axis facing the radially outward direction of the blade rotation. The through holes 310 have a chamfered or flared structure at the port near the outer surface of the blade crown 300.

[0040] Specific technical effects: The orifice axis orientation and the trumpet-mouth pressurization effect, combined with centrifugal force, increase the outflow velocity and suppress backflow, reducing droplet accumulation and edge erosion near the leaf crown.

[0041] In this embodiment, the bottom and sidewall surfaces of the flow channel 110 are provided with a micro-rib / micro-dimple array microtexture arranged along the channel direction. The microtexture pitch is 50-500 μm, and the height or depth is 10-80 μm. The microtexture can be achieved by femtosecond laser writing, laser dot cladding, or chemical etching; for arc-shaped channels, convex ribs along the flow direction are preferred, and for V-shaped channels, concave dots along the flow direction are preferred.

[0042] Furthermore, the microtexture density is increased in the 1 / 3 length section of the flow channel 110 near the leaf crown 300 (pitch reduction of 20%–40%).

[0043] Specific technical effects: Microtexture guides the directional sliding of the liquid film and forms a microscale air cushion, reducing adhesion work and retention probability, and improving resistance to erosion and cavitation.

[0044] In this embodiment, the surface of the flow channel 110 or the surface of the blade 100 near the blade crown 300 is coated with a hydrophobic coating or a hard corrosion-resistant coating. The hydrophobic coating may be a fluorosilane self-assembled film, a DLC-type carbon film, etc., with a static contact angle ≥105° and a thickness of 0.2-3 μm; the hard corrosion-resistant coating may be CrN, AlTiN, or Cr3C2-NiCr, etc., with a thickness of 10-80 μm. The coating coverage area includes at least the bottom and adjacent area of ​​each flow channel 110 and may extend outward to the entrance of the through hole 310.

[0045] In a preferred example, the coating is further configured as follows: a composite coating system consisting of a hard, corrosion-resistant underlayer and a hydrophobic toplayer, with the underlayer thickness being 20–50 μm and the toplayer thickness being 0.5–2 μm.

[0046] Specific technical effects: The hard layer resists solid-liquid erosion, and the hydrophobic layer reduces wetting adhesion. The two work together to reduce material loss rate and extend service life.

[0047] In this embodiment, the flow channel grooves 110 are arranged in a mirror or near-mirror configuration on the front and back sides of the blade 100, and the angle between each flow channel groove 110 and the tangential direction of the blade 100 profile is 10°–30°. To accommodate different incoming flow angles of attack, the angle of the flow channel grooves 110 on the back side can be adjusted relative to the front side by ±5°.

[0048] Furthermore, the included angle of the flow channel groove 110 near the blade root 200 region is taken as a smaller value (10°-15°), and the included angle of the flow channel groove near the blade crown 300 region is taken as a larger value (20°-30°).

[0049] Specific technical effects: The mirror arrangement maintains the bilateral symmetry of the blade force and liquid discharge, and the included angle setting ensures the formation of a stable tangential velocity component in the boundary layer, improving collection efficiency and reducing disturbance to the mainstream aerodynamics.

[0050] In this embodiment, the blade 100, blade root 200, and blade crown 300 are integrally formed from stainless martensitic steel or nickel-based alloy; the flow channel groove 110 and the through hole 310 are obtained by five-axis CNC milling / electrical discharge machining / laser forming; the microtexture is formed by laser engraving or chemical etching; the coating is completed by PVD, HVOF, or plasma-enhanced chemical vapor deposition. Key tolerances: coaxiality of the connecting section of the through hole 310 and the flow channel groove 110 ≤ 0.05 mm, through hole diameter tolerance ± 0.05 mm, and guide slope linearity error ≤ 0.3°.

[0051] Working mechanism and instructions for use: During operation, the blades 100 rotate at high speed under the action of steam. The condensed water droplets or liquid films are captured by the flow channel 110 and migrate rapidly towards the blade crown 300 along the guide slope. The parallel convergence of the main and branch guide channels increases the drainage flux, and the gradual change in cross-section and size creates a "convergence-expansion" effect along the blade. The through holes 310 of the blade crown 300 throw the liquid out under the action of centrifugal force and local pressure at the bell mouth, reducing the amount of liquid remaining on the blade surface. The microtexture and hydrophobic / hard coating work together to reduce wetting and erosion. The mirrored arrangement maintains the balance of drainage and stress on both sides, thereby significantly inhibiting water droplet erosion and improving cavitation boundary conditions, thus improving the service life of the blades and the efficiency of the unit.

[0052] In the description of this specification, the terms "one embodiment," "some embodiments," "specific embodiment," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0053] Although embodiments of the present invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A cavitation-resistant turbine blade, characterized in that, It includes a leaf blade (100), a leaf root (200), and a leaf crown (300) that are connected in sequence and formed in one piece. The blade (100) has several flow channel grooves (110) extending from the leaf root (200) to the leaf crown (300) along the leaf height direction on both sides. The tail end of each flow channel groove (110) is connected to several through holes (310) provided in the leaf crown (300) and opening to the outside of the leaf crown (300). Each of the flow channels (110) is arranged in an arc or zigzag shape in the blade span direction, and forms a flow guiding slope with the blade (100) profile along the blade height direction. The flow guiding slope gradually increases from the end near the blade root (200) to the end near the blade crown (300).

2. The anti-cavitation turbine blade according to claim 1, characterized in that, The flow channel (110) includes a main flow channel located in the middle of the blade (100) and several sub-flow channels arranged alternately with the main flow channel in the blade span direction. The sub-flow channels and the main flow channel are connected in parallel at one end near the blade crown (300) and then connected to the corresponding through hole (310).

3. The anti-cavitation turbine blade according to claim 1, characterized in that, The cross-section of the flow channel groove (110) is a rounded trapezoid, arc or V-shaped structure. The width and depth of the flow channel groove (110) gradually increase from the end near the leaf root (200) to the end near the leaf crown (300), and the two sides of the groove opening are provided with transition rounded corners.

4. The anti-cavitation turbine blade according to claim 1, characterized in that, The through holes (310) are arranged in rows along the arc direction of the blade crown (300), the axis of the through holes (310) is directed toward the radial outer side of the blade rotation, and a chamfer or flared structure is provided at the port near the outer surface of the blade crown (300).

5. The anti-cavitation turbine blade according to claim 1, characterized in that, The bottom and sidewall surfaces of the flow channel (110) are provided with microtextures arranged along the channel direction. The microtextures are microrib arrays or microdimple arrays. The pitch of the microtextures is 50-500 micrometers, and the height or depth is 10-80 micrometers.

6. The anti-cavitation turbine blade according to claim 1, characterized in that, The surface of the flow channel (110) or the surface of the blade (100) near the crown (300) is covered with a hydrophobic coating or a hard corrosion-resistant coating, and the coverage of the coating includes at least the bottom and adjacent area of ​​each flow channel (110).

7. The anti-cavitation turbine blade according to claim 1, characterized in that, The flow channel grooves (110) are arranged in a mirror or near mirror manner on the front and back sides of the blade (100), and the angle between each flow channel groove (110) and the tangential direction of the blade (100) is 10°-30°.

Images