A passive pitch control system

Abstract

The present invention discloses a passive variable pitch system, comprising a main shaft and a plurality of blades distributed around the axis of the main shaft, characterized in that it also comprises: an elastic movement steering mechanism for guiding the blade to deflect when the blade moves relative to the blade cavity shell, and for applying elastic force to the blade; a generator, or an electric motor, or an engine connected to the rotating shaft. The system can automatically obtain the best combination of pitch angle and rotation speed in different types of turbine machinery, and the use of a purely mechanical structure will not be affected by power outages, inaccurate anemometers or user errors, thereby enhancing system reliability, rigor and control efficiency, and overcoming the shortcomings of the existing active control system, which is extremely complex and expensive.

Description

Technical Field

[0001] The invention relates to blade technology, and in particular to a passive variable pitch system. Background Art

[0002] At present, devices that use rotating blades to achieve power input or power output are widely used, for example: they are widely used in wind turbines, water turbines, propellers, turbines, rotary machines and other equipment. Among them, since the blades are affected by the speed of the fluid (gas or liquid) during rotation, it is usually necessary to adjust the pitch angle of the blades according to different flow rates. In the prior art, the pitch angle of the blades is usually adjusted by electronic control, and the pitch angle of the blades is adjusted by using a computer system to detect the wind speed. However, all of the above rely on several subsystems, such as computers, software, anemometers, thermometers, etc., and these subsystems are easily affected by errors and failures, which causes the entire system to become very complicated, with low reliability and high manufacturing and maintenance costs. How to design a passive variable pitch system with high reliability and low cost is a technical problem to be solved by the present invention. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a passive pitch system to solve the defects of low reliability and high cost of the automatic pitch system in the prior art, thereby improving the reliability of the automatic pitch system and reducing its manufacturing cost and maintenance cost.

[0004] The technical solution provided by the present invention is a passive pitch system with a counterweight device, comprising a main shaft and a plurality of blades distributed around the axis of the main shaft, and further comprising:

[0005] An elastic movement steering mechanism, used for guiding the blade to rotate around its own center line to change the pitch angle when the blade moves longitudinally relative to the blade cavity shell, and for applying an elastic force to the blade;

[0006] The blade counterweight assembly is used to offset the component force effect formed by the blade gravity in the direction of the blade centerline during the rotation of the blade.

[0007] A generator, or an electric motor, or an engine is connected to the rotating shaft.

[0008] Furthermore, it also includes a blade cavity shell, which is arranged on the main shaft for mounting the blade. When the rotation of the blade causes the centripetal force of the blade to change, the blade can move on the blade cavity shell along the longitudinal axis of the blade.

[0009] Furthermore, the blade counterweight assembly includes an annular guide rail and a gravity roller, the center of the annular guide rail is located above the axis of the main shaft, each blade is configured with the gravity roller, the elastic member is connected between the gravity roller and the blade, and the gravity roller is rolling or slidingly arranged in the annular guide rail.

[0010] Furthermore, the moving steering mechanism includes a slide groove and a guide member arranged in the slide groove.

[0011] Further, the slide groove is arranged in the blade cavity shell, and the guide member is arranged on the blade; or, the slide groove is arranged on the blade, and the guide member is arranged on the blade cavity shell.

[0012] Furthermore, the guide member is a guide column or a sliding block or a shaft ring slidably arranged on the sliding groove.

[0013] Furthermore, the guide member is a guide roller that can roll in the slide groove.

[0014] Furthermore, two or more blade cavity shells are distributed in the circumferential direction of the main shaft, each of the blade cavity shells is provided with a mounting hole, and the root of the blade is mounted in the mounting hole.

[0015] Furthermore, a fixing ring is provided on the blade cavity shell, and the fixing ring is sleeved on the blade and fixed on the blade cavity shell; or, a fixing ring is provided on the blade, and the fixing ring is sleeved on the blade cavity shell and fixed on the blade.

[0016] Furthermore, the elastic component refers to a component that generates a restoring force to resist the deformation when subjected to tension, compression, rotation, or torsion, including a spring.

[0017] Furthermore, the outer diameter of the blade cavity shell is smaller than the inner diameter of the blade root of the blade, and the blade root can slide on the outer surface of the blade cavity shell; or, the inner diameter of the blade cavity shell is larger than the outer diameter of the blade root of the blade, and the blade root can slide in the blade cavity shell.

[0018] Furthermore, the blade cavity shell is completely or partially contained inside the central hub, or completely outside the central hub.

[0019] Furthermore, a linear bearing or a ball bearing array is used on the blade root or the blade cavity shell.

[0020] Compared with the prior art, the advantages and positive effects of the present invention are as follows: the passive variable pitch system provided by the present invention applies elastic force to the blades by setting an elastic component. During the change of the blade speed, the centrifugal force generated by the blades changes, so that the elastic force applied by the elastic component to the blades is different. The blades will move relative to the blade cavity shell in a direction perpendicular to the main shaft axis at different speeds. At this time, the blades are guided by the moving steering mechanism so that the blades rotate while moving, thereby automatically adjusting the pitch angle to automatically configure the optimal pitch angle for each blade rotation rate. The automatic adjustment of the blade pitch angle is achieved mechanically by using the elastic component in conjunction with the moving steering mechanism, without the need to configure a complex electronic control system, and with better operating reliability. In addition, the structure of the entire system is simple, and the manufacturing cost and maintenance cost are low.

[0021] In summary, compared with the prior art, the advantages of the present invention are summarized as follows:

[0022] 1) Relatively simple.

[0023] 2) Not subject to user error.

[0024] 3) Not affected by loss of power.

[0025] 4) Not affected by computer failure or malfunction.

[0026] 5) Not affected by failure or errors in electronic subsystems (such as anemometers).

[0027] 6) Durability and service life are extremely high.

[0028] 7) Low maintenance. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0030] Figure 1 It is a structural schematic diagram of an embodiment of a passive pitch control system of the present invention;

[0031] Figure 2 A partial cross-sectional view of an embodiment of a passive pitch system of the present invention;

[0032] Figure 3 A partial exploded view of an embodiment of a passive pitch control system of the present invention;

[0033] Figure 4It is an assembly diagram of the annular guide rail, gravity roller and spring of the passive pitch system embodiment of the present invention;

[0034] Figure 5 It is an assembly diagram of the annular guide rail and the main shaft of an embodiment of the passive pitch system of the present invention;

[0035] Figure 6 The ring guide rail and gravity roller assembly of the passive pitch system embodiment of the present invention Figure 1 ;

[0036] Figure 7 The ring guide rail and gravity roller assembly of the passive pitch system embodiment of the present invention Figure 2 ;

[0037] Figure 8 The ring guide rail and gravity roller assembly of the passive pitch system embodiment of the present invention Figure 3 ;

[0038] Fig. 9 The structure of the annular guide rail of the passive pitch system embodiment of the present invention is schematically shown. Figure 1 ;

[0039] Fig.10 The structure of the annular guide rail of the passive pitch system embodiment of the present invention is schematically shown. Figure 2 ;

[0040] Fig.11 The structure of the annular guide rail of the passive pitch system embodiment of the present invention is schematically shown. Figure 3 ;

[0041] Fig.12 The structure of the annular guide rail of the passive pitch system embodiment of the present invention is schematically shown. Figure 4 ;

[0042] Fig.13 The structure of the annular guide rail of the passive pitch system embodiment of the present invention is schematically shown. Figure 5 ;

[0043] Fig.14 The structure of the gravity roller of the passive pitch system embodiment of the present invention is schematically shown. Figure 1 ;

[0044] Fig.15 The structure of the gravity roller of the passive pitch system embodiment of the present invention is schematically shown. Figure 2 ;

[0045] Fig.16 The structure of the gravity roller of the passive pitch system embodiment of the present invention is schematically shown. Figure 3 ;

[0046] Fig.17 This is the assembly diagram of the blade hub and blade cavity shell;

[0047] Fig.18 This is the coordinate analysis diagram of the blade;

[0048] Fig.19 This is the force analysis diagram of the blade;

[0049] Fig. 20 This is the coordinate analysis diagram of the blade cavity shell.

[0050] Explanation of the reference numerals: 1-blade, 2-blade cavity shell, 3-elastic member, 4-guide, 5-slide groove, 6-fixing ring, 7-blade root, 8-hub, 9-gravity roller, 10-annular guide rail, 11-motor / generator, 12-main shaft, 13-casing, 14-rotating cover. DETAILED DESCRIPTION

[0051] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0052] like Fig.18 As shown in Figure 1, the centrifugal force acting on all rotating blades is proportional to the square of the hub speed. The higher the speed, the greater the centrifugal force pulling the blades away from the hub. This centrifugal force is counteracted by a linear spring that stretches as the speed increases. As the spring stretches, the blades rotate along their axis under the action of the rollers and guides. The guides can be designed to strictly increase the blade pitch angle as the speed increases (such as for propellers), or to increase the blade pitch angle within a safe speed range (such as for turbines), and then reduce the blade pitch angle and / or drop to zero when the speed increases too high.

[0053] A simple model of a system with a hub rotating at a constant speed in a vertical plane can be derived for typical wind turbines, various axial fans, propellers in horizontal straight flight, etc. This model can be used to analyze its dynamics and its performance in order to make more appropriate designs for various applications.

[0054] A useful method is to define a coordinate system fixed to the ground and a coordinate system fixed to the hub, with the two coordinate systems having the same origin. Use XYZ to represent the coordinate system fixed to the ground, and xyz to represent the coordinate system fixed to the hub.

[0055] The centers of both coordinate systems are located at the intersection of the blade cavity shell centerline. The x-axis is vertical, the y-axis is out of the paper, and the z-axis is horizontal. The y- and y-axes are always collinear, but when the hub rotates, the x- and z-axes change their directions, expressed as β, while the z-axis always points to the centerline of a blade cavity shell.

[0056] like Fig.19 As shown, the free body force diagram.

[0057] It is necessary to consider the forces and moments acting on the blades to simulate and understand their motion, including their response to disturbances. These forces come from aerodynamic forces, gravity, roller and guide interactions, centrifugal forces, springs, and blade housing interactions. Free body diagrams help to understand these forces and moments.

[0058] There are four key points, A, C, R and G. A is the aerodynamic center of the blade, where the aerodynamic forces and moments act, C is the mass center of the blade, where the centrifugal force and gravity are applied. R is the point of action of the reaction force / moment, and G is the center of the circular section of the blade roll plane. It is assumed here that the aerodynamic force in the z direction is negligible, and the aerodynamic moments acting in the x-axis and y-axis directions are also negligible.

[0059] In addition, F represents a force and M represents a moment. The subscript a represents "aerodynamic", c represents "centrifugal", g represents "groove", and relates to the force or moment acting on the guide or groove, r represents "reaction", s represents "spring", x represents "in the x direction", y represents "in the y direction", and z represents "in the z direction".

[0060] As the blades rotate, the weight of the blades will act in different directions in the fixed coordinate system of the hub. Unfortunately, gravity acts primarily in the xz plane and affects the forces in the z direction, creating a periodic pull on the blades, which in turn affects the pitch angle of the blades. As the pitch angle of each blade varies periodically, all forces and moments will also vary periodically at the frequency of the blade rotation. The center rail and center roller are designed to correct for this periodic action, pushing up when the blade is at the top of its periodic rotation and pulling up when the blade is at the bottom of its periodic rotation. As a result of this correction, the z-coordinate position of the blade will not depend on its angular coordinate, β, but only on the rotational speed of the hub. Mathematically, we can correct this by changing the free length of the spring, z s0, the effects of the central rail and rollers are modeled as a function of the angular coordinate, β. An important consideration is whether the added cost and complexity of the central roller and rail assembly can be avoided. The weight of the blade is constant, and the centrifugal force is proportional to the square of the hub speed. Therefore, when the speed is high, the centrifugal force dominates the weight. In addition, the influence of centrifugal force relative to gravity can be further increased by designing the material with higher density near the tip of the blade. To avoid resonance, the system should be designed so that its natural frequency is outside the speed domain. Damping systems can also be used and adjusted. We can consider a simple point mass rotating in a vertical plane and connected to its center of rotation by a rope. When the point mass is in the lowest position, the centrifugal force and gravity act in the same direction. In this case, the tension on the rope is: l is the length of the rope, m is the mass, g is the acceleration due to gravity, and the dot above represents the time derivative. is the angular velocity of the blades about the hub. A small UAV propeller has a radius of about 0.1 m, which corresponds to a "tether length" of about 0.035 m. The propellers of a small UAV can rotate at speeds of 78.5-130.9 rad / s when in flight; these frequencies should be avoided as much as possible from the natural frequencies of the system. When the small UAV is simplified to a point mass and tether, gravity is 1.6% to 4.5% of the centrifugal force over the entire speed range of the hub. In this case, the pitch angle fluctuations are slight, and it is feasible to omit the central roller and central guide assembly. All systems that rotate in the horizontal plane, or operate without gravity, can work well without the central guide and roller assembly. As another example, consider a typical large wind turbine rotating in a vertical plane at a speed of 1.05 rad / s, with blades that are 40 meters long and have a mass of 5500 kg. In this case, gravity is 67% of the centrifugal force, so the central guide and roller assembly cannot be omitted.

[0061] Point R is drawn at the outer edge of the blade shell and in the center of the circular cross section. The location of R is somewhat arbitrary, since for any assumed point of application, an exact value of a reaction force-torque system can be determined. The reaction torque and force in the z direction are both small enough to be negligible (good lubrication, no friction). The spring force is also a result of the geometric analysis through point R.

[0062] The last key point is G, which is the center of the circular cross section in the plane of the blade roller. The forces applied to the blade roller can be simplified to a force applied at point G and the corresponding moment. It is assumed that the blade rail is deep enough to prevent the end of the blade roller from contacting the bottom of the blade rail, so that there is no force applied to the blade roller in the direction of the blade rail's binormal. In addition, friction is neglected, so that there is no force applied to the blade roller in the direction tangential to the rail. Therefore, the forces that the rail can apply can be simplified to only the forces in the direction normal to the rail. The subscript n stands for "normal", the arrow above stands for vector, and ^ stands for unit vector. Assuming a completely rigid blade, we can derive the equation of motion.

[0063] Equations of motion

[0064] (1)F ax +F rx +F gx +W x =0

[0065] (2)F ay +F ry +F gy =0

[0066]

[0067] (4)-F ay ·(z A -z R )+F gy ·(z R -z G )+M rx =0

[0068] (5)F ax ·(z A -z R )-F gx ·(z R -z G )+W x ·(z C -z R )+M ry =0

[0069]

[0070] These six equations of motion have eight unknowns: F gx , F gy , F gz , M gz , F rx , F ry , M rx , M ry; however, with the rail-roller interaction, more equations can be obtained.

[0071]

[0072]

[0073]

[0074] The three new equations obtained contain four new unknown quantities: but will be determined during the rail design process. Then F gx , F gy , and F gz will become an unknown function F g , we will have nine equations in nine unknowns, which is a solvable system with a unique solution.

[0075] like Fig. 20 As shown, the guide rail design is in the normal direction.

[0076] For this particular invention, the rail design is novel. For convenience, a coordinate system with a subscript of g is defined here, starting from the inside edge of the rail, such that z = z g +z g0 ,Then:

[0077] Each rail has a constant radial distance from the centerline of the blade chamber shell, so cylindrical coordinates are more convenient.

[0078]

[0079] It can be represented as a variable z g function, where the function θ g (z g ) determines when the blade has been pulled to a specific z g For a particular blade design operating on a particular domain, several optimal rotation rate / pitch angle combinations can be calculated. Curve fitting can be applied to the optimal rotation rate / pitch angle within the domain to obtain θ g (z g ). Converting back to the master Cartesian coordinate system fixed to the hub gives the following useful description of the guideway:

[0080]

[0081] Next, we determine the length of the curve "s" of the guide rail, which is described as a function of z (the symbol "~" represents the integration variable z to distinguish it from the integration limit z)

[0082]

[0083] Introduction Etc., the symbol ′ represents the differential with respect to z, and we determine the unit normal vector as:

[0084]

[0085] Forces and moments

[0086] Air power

[0087] For a propeller or turbine, it is usually designed around the central values ​​of flow rate, pitch angle, rotation speed, etc. to achieve its efficient operation. Then its aerodynamics are characterized and modeled, including the variation of different parameters and dimensionless coefficients in the application domain. These models are synthesized into the equations of motion of the passive pitch control system.

[0088] The centrifugal force is described by the following formula:

[0089]

[0090] Where m is the mass of the blade, is the rotation speed of the wheel hub, z c is the location of the blade mass center, and is function.

[0091] weight:

[0092] If the hub rotates in the vertical plane, its weight will have no y component. In this case, the force due to the weight in the hub-fixed coordinate system will depend on the angle of rotation of the blade, as follows:

[0093] W x = -W·sin(β)

[0094] W z =-W·cos(β)

[0095] spring:

[0096] If the spring is linear over its operating range, then the force it exerts on the blade is modelled as:

[0097]

[0098] where k is the linear spring constant, z s0 is the z position of the blade roller corresponding to zero spring compression or extension. s0 is a known function of the hub rotation angle β, designed to offset the blade weight W in the z direction zA change in the pitch of the blade will cause the spring to twist and extend. If the moment is large enough, coupling is neglected, and the torque due to twisting is assumed to be linear, then:

[0099]

[0100] where τ s is the torsional spring constant, θ s0 is the pitch angle corresponding to zero spring torsion.

[0101] Roller and reaction forces / torques:

[0102] Using the equations of motion derived previously, the net reaction forces and moments applied to the blade can be determined.

[0103] like Figure 1-Figure 17 As shown, the specific structure of the passive pitch system of this embodiment is described in conjunction with the accompanying drawings:

[0104] The passive pitch control system of this embodiment includes a blade 1, a hub 8 and a main shaft 12, wherein the hub 8 is fixed on the main shaft 12, and further includes:

[0105] A blade cavity shell 2 is arranged on the hub 8 and is used to mount the blade 1. When the centripetal force of the blade 1 changes due to the rotation of the blade 1, the blade 1 can move on the blade cavity shell 2 along the longitudinal axis of the blade 1;

[0106] An elastic member 3, arranged in the blade chamber shell 2 and used for applying an elastic force to the blade 1;

[0107] A moving steering mechanism, used for guiding the blade 1 to rotate around its own center line to change the pitch angle when the blade 1 moves longitudinally relative to the blade chamber shell 2;

[0108] The blade counterweight assembly is used to offset the component force effect in the direction of the center line of the blade 1 formed by the gravity of the blade 1 during the rotation of the blade 1.

[0109] Specifically, in the passive pitch system of this embodiment, the blade 1, the hub 8 and the main shaft 12 rotate together, and the root of the blade 1 is arranged in the blade cavity shell 2. The blade 1 can reciprocate relative to the blade cavity shell 2 along the axial direction perpendicular to the main shaft 12, and can rotate around its center line. The elastic component 3 will apply elastic force to the blade 1 to satisfy the blade 1 in a state of force balance under different rotation speed conditions. The centrifugal force generated by the blade 1 is different due to its different rotation speeds, and the elastic force applied by the elastic component 3 to the blade 1 is also different. The elastic component 3 expands and contracts under different rotation speeds of the blade 1, thereby making the blade 1 move in the blade cavity shell 2, and the moving steering mechanism can guide the blade 1 to perform corresponding rotational deflection to change the pitch angle of the blade 1 during the movement of the blade 1, thereby satisfying the matching ratio of the pitch angle and the rotation speed of the blade 1 to obtain higher efficiency. Compared with the conventional technology that uses an electric control system to adjust the pitch angle, the automatic variable pitch system of this embodiment realizes mechanical adjustment of the pitch angle through the elastic component 3 and the mobile steering mechanism. In actual use, the reliability of pure mechanical adjustment is higher, and the overall structure is simple, and the manufacturing cost and subsequent maintenance cost are both low. Among them, the blade counterweight assembly may also include a fixed annular guide rail 10, the center of the annular guide rail 10 is located above the axis of the main shaft 12, each of the blades 1 is configured with a gravity roller 9, the elastic component 3 is connected between the gravity roller 9 and the blade 1, and the gravity roller 9 is rollingly arranged in the annular guide rail 10, and a plurality of blade cavity shells 2 are distributed in the circumferential direction of the hub 8, and each of the blade cavity shells 2 is provided with a mounting hole, and the blade root 7 of the blade 1 is installed in the mounting hole, and correspondingly, the elastic component 3 is connected to the root of the blade 1, and the elastic component 3 is also located in the mounting hole and connected to the gravity roller 9. Specifically, since the position of blade 1 changes periodically during the rotation process, the gravity effect of blade 1 will also change periodically with the direction of its centrifugal force. In order to reduce the influence of the gravity of blade 1 on the pitch angle adjustment process, the influence of gravity is reduced by cooperating with the eccentrically arranged annular guide rail 10 and gravity roller 9. Specifically, when blade 1 rotates to the lowest end, the gravity of blade 1 is in the same direction as the centrifugal force, and the forces are superimposed. When blade 1 rotates to the highest end, the gravity of blade 1 is in the opposite direction to the centrifugal force, and the forces are offset. When blade 1 is located in the lower area, gravity and centrifugal force are superimposed, thereby increasing the force applied to elastic member 3, increasing the tensile deformation of elastic member 3, and causing blade 1 to move outward from the rotation center. Since the center of annular guide rail 10 deviates from the axis of rotating shaft 12 and is located above the axis, the outward displacement of blade 1 is offset, thereby keeping the absolute position of blade 1 in the axial direction of blade 1 unchanged.Similarly, when the blade 1 is located in the upper area, gravity and centrifugal force weaken each other, causing the elastic member 3 to produce compression deformation or reduce tensile deformation so that the blade 1 moves inward toward the rotation center. Since the center of the annular guide rail 10 deviates from the axis of the rotating shaft 12 and is located above the axis, the inward displacement of the blade 1 is offset, thereby maintaining the absolute position of the blade 1 in the axial direction of the blade unchanged. In order to improve reliability and structural strength, the annular guide rail 10 includes a plurality of guide rail grooves arranged side by side, and each of the blades 1 is configured with a plurality of gravity rollers 9 arranged side by side, and the gravity rollers 9 are rollingly arranged in the corresponding guide rail grooves 71. In particular, the annular guide rail 10 can be a closed loop structure such as a circle, an ellipse, or an approximately triangular structure. In addition, in order to improve reliability and prevent the blade 1 from detaching from the mounting hole, a fixing ring 6 is also provided on the blade chamber shell 2, and the fixing ring 6 is sleeved on the blade 1 and fixed on the blade chamber shell 2. The fixing ring 6 can prevent the guide member 4 from sliding out of the slide groove 5 to prevent the blade 1 from falling off. The elastic member 3 refers to a member that generates a restoring force to resist the deformation when subjected to tension, compression, rotation, or torsion. For example, the elastic member 3 may be a spring or other member with elastic expansion and contraction function. An elastic mechanism may also be designed that does not require a moving steering mechanism, but relies on its own torsion and tension coupling to generate the required pitch angle.

[0110] Further, in order to conveniently realize the mobile steering mechanism to adjust the deflection of the blade 1, the mobile steering mechanism includes a slide groove 5 and a guide member 4 arranged in the slide groove 5. Specifically, the guide member 4 moves along the slide groove 5, follows the arc of the slide groove 5 and can control the deflection of the blade 1, wherein the slide groove 5 can be arranged in the blade cavity shell 2, and the corresponding guide member 4 is arranged on the blade 2; or, the slide groove 5 is arranged on the blade 1, and the guide member 4 is arranged on the blade cavity shell 2. Specifically, the slide groove 5 is arranged on the blade cavity shell 2, and the guide member 4 is arranged on the blade 1 as an example for explanation: after the rotation speed of the blade 1 changes, the blade 1 moves in the mounting hole under the action of centrifugal force, and during the movement of the blade 1, the guide member 4 and the slide groove 5 cooperate to guide, so that the blade 1 rotates and deflects along the curve of the slide groove 5, thereby automatically meeting the pitch angle requirement required under the speed condition. Wherein, the guide member 4 can be a guide column or a slider slidably arranged in the slide groove 5; or, the guide member 4 is a guide roller that can roll in the slide groove 5. Generally speaking, the greater the speed at which blade 1 rotates, the greater the pitch angle of blade 1 needs to be. Therefore, in the conventional design of slide groove 5, slide groove 5 can be designed so that as blade 1 moves outward along slide groove 5, the pitch angle of blade 1 gradually increases. Conversely, as blade 1 moves inward along slide groove 5, the pitch angle of blade 1 gradually decreases.

[0111] The outer diameter of the blade cavity shell 2 is smaller than the inner diameter of the blade root 7 of the blade 1, and the blade root 7 can move on the outer surface of the blade cavity shell 2; or the inner diameter of the blade cavity shell 2 is larger than the outer diameter of the blade root 7 of the blade 1, and the blade root 7 can move in the blade cavity shell 2. As for the hub 8 in the system, the blade cavity shell 2 can be located outside the hub 8, or the size of the hub 8 can be increased so that the hub 8 partially or completely wraps the blade cavity shell 2, and the blade cavity shell 2 does not protrude from the hub 8.

[0112] In addition, in actual use, the passive pitch system of this embodiment is configured with additional equipment for input power generation or for power output, for example: the main shaft 12 can be connected to the generator 11, or the motor, or the engine and other related components.

[0113] The passive variable pitch system provided by the present invention adopts a purely mechanical mechanism and will not be affected by power outages, inaccurate anemometers or user errors, thereby enhancing the reliability, rigor and control efficiency of the system. During the change in blade speed, the centrifugal force generated by the blade changes, causing the spring force applied by the spring to the blade to change. The blade will move relative to the blade cavity shell and cooperate with the mobile steering mechanism to guide the blade so that the blade itself rotates to automatically adjust the pitch angle. In addition, an elastic mechanism can also be designed that does not require a mechanical mobile steering mechanism, but relies on its own torsion and stretching coupling to generate the required pitch angle. The system can be slightly adjusted and applied in many aspects. For example, the system can provide anti-overspeed protection for fluid-driven impellers.

[0114] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A passive pitch system, comprising a main shaft and a plurality of blades distributed around the axis of the main shaft, characterized in that: Also includes: A blade cavity shell, arranged on the main shaft for mounting the blade, wherein when the centripetal force of the blade changes due to the rotation of the blade, the blade can move on the blade cavity shell along the longitudinal axis of the blade; an elastic-movement-steering mechanism, used for guiding the blade to rotate about its own center line to change the pitch angle when the blade moves longitudinally relative to the blade cavity shell, and for applying an elastic force to the blade; The two ends of the elastic member of the elastic-moving-steering mechanism are respectively provided with connecting pieces, wherein one of the connecting pieces is fixed on the blade, and the other connecting piece is fixed on the gravity roller; a generator, or a motor, or a generator, connected to the main shaft; A blade counterweight assembly, used to offset the influence of the force component formed by the blade gravity in the direction of the blade centerline during the rotation of the blade; The blade counterweight assembly includes an annular guide rail and a gravity roller, the center of the annular guide rail is located above the axis of the main shaft, each blade is equipped with the gravity roller, and the gravity roller is rollingly arranged in the annular guide rail; The movement and steering mechanism of the elastic-movement-steering mechanism comprises a slide groove and a guide member arranged in the slide groove; Two or more blade cavity shells are distributed in the circumferential direction of the main shaft, each of the blade cavity shells is provided with a mounting hole, and the root of the blade is mounted in the mounting hole; Linear bearings or ball bearing arrays are used on the blade root or blade cavity shell.

2. The passive pitch system according to claim 1, characterized in that: The slide groove is arranged in the blade cavity shell, and the guide member is arranged on the blade; or, the slide groove is arranged on the blade, and the guide member is arranged on the blade cavity shell.

3. The passive pitch system according to claim 1, characterized in that: The guide member is a guide column, a slider or a shaft ring slidably arranged in the slide groove; or, the guide member is a guide roller that can roll in the slide groove.

4. The passive pitch system according to claim 1, characterized in that: A fixing ring is also provided on the blade cavity shell, and the fixing ring is sleeved on the blade and fixed on the blade cavity shell; or a fixing ring is also provided on the blade, and the fixing ring is sleeved on the blade cavity shell and fixed on the blade.

5. The passive pitch system according to any one of claims 1 to 4, characterized in that: The elastic member refers to a member that generates a restoring force to resist the deformation caused by tension, compression, rotation or torsion, including a spring.

6. The passive pitch system according to any one of claims 1 to 4, characterized in that: The inner diameter of the blade cavity shell is greater than the outer diameter of the blade root of the blade, and the blade root can slide in the blade cavity shell.

7. The passive pitch system according to any one of claims 1 to 4, characterized in that: The blade chamber shell is completely or partially accommodated inside the central hub, or completely outside the central hub.

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