Blade hub sweepback type self-rectification axial flow air turbine runner

Abstract

The invention discloses a blade hub sweepback type self-rectification axial flow air turbine runner, and belongs to the field of wave energy power generation devices. The impeller comprises a hub, the hub is rotationally arranged in a runner chamber, the hub is arranged between a front guide vane and a rear guide vane, a plurality of blades are arranged on the hub, the blades are evenly arranged in the circumferential direction with the axis of the hub as the center, and each blade comprises an air inlet edge adjacent to the front guide vane and an air outlet edge adjacent to the rear guide vane. Axial airflow flows out along the front guide vane, enters the positions among the blades of the hub through the air inlet side, acts to generate torque, flows out from the air outlet side, is rectified by the rear guide vane and flows out in the axial direction of the hub. The invention aims at solving the problems that the local loss is increased and the efficiency is influenced due to the large difference of liquid flow angles from a hub to a rim inlet of the current axial flow air turbine, reducing the local loss of an impeller and improving the turbine efficiency.

Description

Technical Field

[0001] This invention relates to a blade hub swept-back self-rectifying axial flow air turbine runner, belonging to the field of wave energy power generation devices. Background Technology

[0002] Oscillating water column wave energy generators, also known as air turbine wave energy generators, are a widely used type of wave energy generator. The process involves three stages: first, converting wave energy into airflow energy through an air chamber; second, converting airflow energy into shaft work on a motor shaft through an air turbine; and finally, converting the shaft work into electrical energy through a generator.

[0003] The axial-flow air turbine is a key component in the secondary conversion of an oscillating water column wave energy power generation device. It mainly consists of three parts: a front guide vane, a turbine rotor, and a rear guide vane. The front and rear guide vanes are arranged in a mirror-symmetric configuration, with the plane of symmetry perpendicular to the center of the rotation axis. This ensures that the air turbine provides the turbine rotor with pre-rotation in the same direction under bidirectional flow conditions. The turbine rotor itself has a mirror-symmetric geometry, with its center plane of symmetry being the same as that of the front and rear guide vanes. This ensures that the turbine rotor rotates in the same direction under bidirectional flow conditions, thus achieving self-rectification.

[0004] In axial-flow turbine blades, the radius gradually increases from the hub to the rim. Therefore, the circumferential velocity at each span position gradually increases from the hub to the rim. Under uniform inflow conditions, the axial velocity of the blade is equal from the hub to the rim. It can be seen that the relative airflow angle of the blade in the span direction from the hub to the rim gradually changes from the hub to the rim. Furthermore, the smaller the hub-to-rim ratio of the turbine blades, the greater the difference in the relative airflow angle (the angle between the airflow velocity relative to the blade velocity and the blade circumferential velocity) between the hub and the rim. Figure 2 beta h and β s As shown.

[0005] Currently, the traditional structure of this type of axial flow air turbine is that the blades have the same geometry from the hub to the rim, and are stretched radially from the hub to the rim. The inlet angles of the blades at the hub and rim are consistent. Figure 3 As shown. In this case, the incoming flow forms a large angle of attack at the blade inlet, resulting in significant local losses and making it difficult to improve the hydraulic efficiency of the runner. The highest efficiency of this type of turbine is 30% to 50%.

[0006] In summary, there is an urgent need to propose a blade hub swept-back self-rectifying axial air turbine runner to solve the above-mentioned technical problems. Summary of the Invention

[0007] The purpose of this invention is to address the problem of increased local losses and reduced efficiency in current axial-flow air turbines due to the significant difference in airflow angle between the hub and the rim inlet. A brief overview of the invention is provided below to offer a basic understanding of certain aspects. It should be understood that this overview is not an exhaustive summary of the invention. It is not intended to identify key or essential parts of the invention, nor is it intended to limit the scope of the invention.

[0008] The technical solution of this invention:

[0009] A bladed hub swept-back self-rectifying axial flow air turbine rotor includes a hub rotatably disposed in a rotor chamber. The hub is arranged between a front guide vane and a rear guide vane. Multiple blades are disposed on the hub. The blades are evenly arranged circumferentially around the axis of the hub. Each blade includes an inlet side adjacent to the front guide vane and an outlet side adjacent to the rear guide vane. The axial airflow flows out along the front guide vane, enters between the blades of the hub through the inlet side, performs work to generate torque, and then flows out from the outlet side. After being rectified by the rear guide vane, it flows out along the axial direction of the hub.

[0010] Preferably, all blades are arranged symmetrically in a plane perpendicular to the hub axis.

[0011] Preferably: the sweep angle on the hub side The value of is related to the number of leaves N, and the range of values ​​is . .

[0012] Preferably, the side mounting angle of the hub is smaller than the side mounting angle of the blade rim.

[0013] Preferably, the flow channels of the hub and the blade rim are both made of rotating surfaces, and the inlet and outlet sections of the hub are both planes perpendicular to the axis.

[0014] Preferably, the hub and blade are integral structures, the rim side of the blade and the inner wall of the rotor chamber are clearance fit, the clearance value between a single blade and the inner wall of the rotor chamber is 0.02%~0.05% of the inner diameter of the rotor chamber, and the clearance tolerance is ±0.001mm by precision grinding process.

[0015] The present invention has the following beneficial effects:

[0016] 1. This invention combines the internal flow characteristics of an axial-flow air turbine impeller and improves the geometry of the air turbine by sweeping the blades near the hub back, thereby reducing the flow area on the hub side of the impeller, changing the flow distribution from the hub to the rim, reducing the axial velocity on the hub side, increasing the axial velocity on the rim side, and thus reducing the relative airflow angle difference between the hub and the rim, reducing local impeller losses, and improving turbine efficiency;

[0017] 2. In this invention, the inlet and outlet angles corresponding to each span section of the blade are equal. Based on the internal flow characteristics of the axial-flow air turbine rotor, the hub-side installation angle β... A <Flange side mounting angle β B This allows the blades to have better flow matching, reduces local losses at the inlet, enhances flow stability, and improves energy utilization. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of a blade hub swept-back self-rectifying axial flow air turbine runner according to the present invention;

[0019] Figure 2 The diagram below illustrates the inlet velocities of the wheel hub and rim as described in the background art, where (a) is the inlet velocity triangle on the wheel hub side and (b) is the inlet velocity triangle on the rim side.

[0020] Figure 3 This is a schematic diagram illustrating the positional relationship between a traditional axial flow impinging air turbine and a single-blade hub rim, as described in the background art.

[0021] Figure 4 This is a schematic diagram showing the positional relationship between the hub and the blades of the present invention;

[0022] Figure 5 This is a schematic diagram of the inlet velocity of the hub and the rim of the present invention, wherein (a) is the inlet velocity triangle on the hub side and (b) is the inlet velocity triangle on the rim side;

[0023] Figure 6 This is a schematic diagram showing the position angle of the neutral plane section of the blade of the present invention;

[0024] Figure 7 This is a schematic diagram illustrating the fit between the hub and the blade of the present invention;

[0025] Figure 8 This is a comparative schematic diagram of the spanwise cross-sectional shapes of the blades of the present invention and those of a conventional turbine runner. (a) shows the spanwise cross-sectional shape of a conventional turbine runner blade, and (b) shows the spanwise cross-sectional shape of the blade of the present invention. From bottom to top, these represent... Figure 7 H A -H A Cross-sectional diagram, H M -H M Cross-sectional diagram and H B -H B Cross-sectional diagram;

[0026] Figure 9The diagrams show a comparison of the numerical simulation results of the speed distribution and efficiency of the present invention and the traditional turbine runner, where (a) is a comparison of the speed distribution of the present invention and the traditional turbine runner, and (b) is a comparison of the numerical simulation results of the efficiency of the present invention and the traditional turbine runner. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is described below with reference to specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0028] Specific implementation method one: Combining Figures 1 to 9 This embodiment describes a bladed hub-swept self-rectifying axial air turbine rotor, comprising a hub 1 rotatably disposed within a rotor chamber 7. The hub 1 is arranged between a front guide vane 5 and a rear guide vane 6, with the front guide vane 5 positioned as the inlet and the rear guide vane 6 as the outlet. Multiple blades 2 are disposed on the hub 1, evenly arranged circumferentially around the axis of the hub 1. Each blade 2 includes an inlet edge 3 adjacent to the front guide vane 5 and an outlet edge 4 adjacent to the rear guide vane 6. Axial airflow exits along the front guide vane 5, enters the space between the blades 2 of the hub 1 via the inlet edge 3, generates torque, and then exits from the outlet edge 4. After being rectified by the rear guide vane 6, it exits along the axial direction of the hub 1. The number of blades 2 is 28 to 36.

[0029] The side of the hub 1 is the hub surface 8, and the end face of the blade 2 is the rim surface 9.

[0030] This embodiment improves the air turbine geometry so that the inlet edge 3 is swept back near the hub side 1, such as... Figure 4 As shown. This method reduces the flow area on the hub side of the impeller, changes the flow distribution from the hub surface 8 to the rim surface 9, reduces the axial velocity on the hub side, increases the axial velocity on the rim side, and thus reduces the relative airflow angle difference between the hub surface 8 and the rim surface 9, as shown. Figure 5 As shown, this reduces localized losses at the impeller inlet, improving turbine efficiency and flow stability.

[0031] The blades 2 are all mirror-symmetrically arranged along a plane perpendicular to the axis of the hub 1. In the air chamber of the oscillating water column wave energy generator, the roles of the inlet and outlet sides of the blades 3 are interchangeable without difference under both exhalation and inhalation conditions. Under bidirectional flow conditions, the blade-hub swept-back self-rectifying axial flow air turbine rotor of this embodiment rotates in the same direction, achieving self-rectification and meeting the secondary energy conversion requirements of the oscillating water column wave energy generator.

[0032] When observed from the end face in the direction from inlet to outlet, blade 2 sweeps back at the side position angle of hub 1, i.e. Figure 7 and Figure 8 As shown, three radially perpendicular sections H are taken along the length direction, from the hub surface 8 to the rim surface 9". A -H A H M -H M and H B -H B The three cross-sections intersect with blade 2, forming three streamlines. Unlike traditional air turbines where the three streamlines coincide, in this embodiment, the projection of the air turbine across the three cross-sections gradually approaches the runner center from the hub 1 cross-section to the rim cross-section. The opening of blade 2 on the hub 1 side decreases, creating a non-uniform flow distribution within the runner channel. This results in a decrease in axial velocity on the hub 1 side and an increase in axial velocity on the rim side. The theoretical angle of attack difference between the rim and hub airfoils decreases. This improves the turbine's adaptability to incoming flow, reduces local turbine losses, and enhances hydraulic efficiency.

[0033] The flow channels of both the hub surface 8 and the rim surface 9 are rotary surfaces, and the inlet and outlet sections of the hub 1 are both planes perpendicular to the axis. Figure 6 As shown, the side surfaces of the hub surface 8 and the rim surface 9 are both cylindrical surfaces. From the inlet to the outlet, n cross-sections F1~F2 perpendicular to the main axis of the hub 1 can be defined. n Viewed from the inlet to the outlet, let l be the intersection line between the neutral plane of blade 2 and the i-th section. i The intersection point on the hub side is A, and the position angle is defined as φ. Ai Let B be the intersection of the wheel rims, and let φ be the position angle. Bi .,when At this time, it is called the hub sweep of blade 2. The sweep angle on the hub 1 side. The value of is related to the number N of blades 2, and the range of values ​​is . The effect is best at this time. The hub angle is slightly angled at each section from the inlet to the outlet. The value is either constant or exhibits a continuous change that first increases and then decreases to ensure the mirror symmetry of the turbine runner; except for the section from point A to point B, the intersection line l between the neutral plane of blade 2 and the i-th section... i The position angles of other points change monotonically and continuously from the hub 1 to the rim, ensuring a smooth transition of blade 2.

[0034] The blade 2's spanwise cross-section corresponds to a placement angle that monotonically and continuously changes from the hub surface 8 to the rim surface 9, ensuring a smooth transition for the blade 2. The inlet and outlet placement angles β of each cross-sectional streamline are equal.

[0035] The placement angles of the streamlined sections of the air intake edge 3 of the blade 2 are designed in conjunction with the internal flow characteristics of the axial flow air turbine impeller, with the placement angle β closest to the hub 1 side section. A The angle β of the wheel rim side B Compared to smaller, i.e., β A <β M <β B Based on the internal flow characteristics of the axial-flow air turbine rotor, it can be seen that this design gives blade 2 better flow matching, reduces inlet local losses, enhances flow stability, and improves energy utilization.

[0036] This implementation method is compared with the numerical simulation results of the velocity distribution of the air turbine at the symmetrical center section of the runner and the turbine efficiency over a wide flow range using traditional methods, as follows: Figure 9 As shown.

[0037] The hub 1 and blade 2 are integral structures. The impeller in this embodiment is an open structure. The rim side of the blade 2 and the inner wall of the impeller chamber 7 are clearance fit. The clearance between a single blade 2 and the inner wall of the impeller chamber 7 is 0.02% to 0.05% of the inner diameter of the impeller chamber 7. Precision grinding process is used to ensure that the clearance tolerance is ±0.001mm. Under the condition that the structural characteristics allow, a small amount of leakage at the impeller clearance is ensured.

[0038] It should be noted that in the above embodiments, as long as the technical solutions are not contradictory, they can be permuted and combined. Those skilled in the art can exhaust all possibilities based on the mathematical knowledge of permutation and combination. Therefore, the present invention will not describe the technical solutions after permutation and combination one by one, but it should be understood that the technical solutions after permutation and combination have been disclosed by the present invention.

[0039] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A blade-hub swept-back self-rectifying axial air turbine runner, comprising a hub (1), the hub (1) being rotatably disposed within a runner chamber (7), the hub (1) being arranged between a front guide vane (5) and a rear guide vane (6), characterized in that: Multiple blades (2) are provided on the hub (1). The blades (2) are evenly arranged in the circumferential direction with the axis of the hub (1) as the center. The blades (2) include an air inlet side (3) adjacent to the front guide vane (5) and an air outlet side (4) adjacent to the rear guide vane (6). The axial airflow flows out along the front guide vane (5), enters the space between the blades (2) of the hub (1) through the air inlet side (3), generates torque after doing work, and flows out from the air outlet side (4). After being rectified by the rear guide vane (6), it flows out along the axial direction of the hub (1).

2. The blade hub swept-back self-rectifying axial air turbine runner according to claim 1, characterized in that: The blades (2) are all mirror-symmetrically arranged along a plane perpendicular to the axis of the hub (1).

3. The blade hub swept-back self-rectifying axial air turbine runner according to claim 1, characterized in that: The sweep angle on the side of the hub (1) The value of is related to the number N of blades (2), and the range of values ​​is . .

4. The blade hub swept-back self-rectifying axial air turbine runner according to claim 1, characterized in that: The side placement angle of the hub (1) is smaller than the side placement angle of the blade (2) rim.

5. The blade hub swept-back self-rectifying axial air turbine runner according to claim 1, characterized in that: The flow passages of the hub (1) and blade (2) rims are both made of rotating surfaces, and the inlet and outlet sections of the hub (1) are both planes perpendicular to the axis.

6. The blade hub swept-back self-rectifying axial air turbine runner according to claim 1, characterized in that: The hub (1) and the blade (2) are integral structures. The rim side of the blade (2) and the inner wall of the wheel chamber (7) are in clearance fit. The clearance value between a single blade (2) and the inner wall of the wheel chamber (7) is 0.02%~0.05% of the inner diameter of the wheel chamber (7). The clearance tolerance is ±0.001mm by using precision grinding process.

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