A flapping-wing type wind energy utilization device with a blunt trailing edge and surface jet

Abstract

The present invention relates to a flapping-wing type wind energy utilization device with surface jetting, and the flapping-wing blade adopts a blunt trailing edge airfoil. The blunt trailing edge airfoil is symmetrically thickened at the trailing edge of the airfoil, and the symmetric thickening thickness l t The ratio l t / c to the chord length c of the airfoil is 0.02, and the ratio l p / c of the initial position of the symmetric thickening of the blunt trailing edge to the chord length of the airfoil is 0.90. Jet ports with a diameter of 0.5%c are opened on the upper and lower surfaces of the blunt trailing edge airfoil, and the distance from the center of the jet port to the leading edge is 90%c. The present invention combines the advantages of passive and active control technologies, can flexibly control the jet volume according to the change of the oncoming flow conditions, expand the adaptation range of the device, and at the same time can also have high wind energy utilization efficiency when the jet is closed under certain conditions, reducing the demand for external energy input. Compared with the prior art, it has outstanding characteristics such as simple structure, wide adaptability, high flexibility and high wind energy utilization efficiency.

Description

Technical Field

[0001] The present invention relates to a flapping - type wind energy utilization device, and particularly to a flapping - type wind energy utilization device with a blunt trailing edge. Background Art

[0002] Wind energy is one of the most economical power - generation resources in renewable energy. Developing wind power is of great significance for ensuring national energy security, adjusting the energy structure, and reducing environmental pollution.

[0003] Different from traditional rotary - impeller wind turbines, a flapping - type wind energy utilization device (as Figure 1 shown) utilizes the superposition of heaving and pitching motions of the blades (the heaving motion is the up - and - down translation of the airfoil in a plane, and the pitching motion is the motion of the flapping airfoil 1 around a point in the translation plane. As Figure 2 shown, A is the highest point of the heaving motion, and B is the lowest point of the heaving motion) to obtain energy from the fluid. The component of the resultant force generated on the airfoil surface by the fluid flowing through the blade in the vertical direction is called the heaving force. Since the direction of the heaving force is consistent with the motion direction of the airfoil, positive work is done on the airfoil. The flapping - type energy - harvesting device has the advantages of simple design, low noise, wide adaptability, etc., and has less destructive impact on the environment. However, its efficiency is still lower compared with traditional horizontal - axis wind turbines. If the heaving force generated by the fluid on the blade can be effectively increased during the flapping of the airfoil, the wind - energy utilization efficiency of such energy - harvesting devices can be improved, and their competitiveness in the wind - power market can be enhanced.

[0004] In the existing methods for flapping - wing lift augmentation, passive methods such as slotted / slitted, cavities, forced - transition devices, etc. have a narrow applicable working - condition range and poor variable - condition performance, so the lift - augmentation effect is limited. Active - control methods can have good variable - condition performance and can change their own structure or flow parameters according to the changes in the external flow field, so as to obtain the optimal control effect within a large working - condition range. However, these methods rely on the input of external energy and consume a high amount of energy. Therefore, exploring simple, efficient, lower - energy - consuming, and reliable lift - augmentation means to improve the wind - energy utilization efficiency of this type of energy - harvester has important engineering application value and broad market development prospects.

[0005] In the existing methods for flapping-wing lift augmentation, passive methods such as slotting / slitting on the blade surface, cavities, adding forced transition structures, etc. do not require external energy input. However, due to their fixed forms, they cannot be flexibly adjusted according to the changes in the oncoming flow conditions. As a result, the applicable operating conditions of these technologies are narrow, the performance under variable operating conditions is poor, and the lift augmentation effect is very limited. Active control methods can have good performance under variable operating conditions and can correspondingly change their own structures or flow parameters according to the changes in the external flow field, so as to obtain the optimal control effect within a large range of operating conditions. However, most of the active control methods adopted at the present stage usually require a large amount of external energy input. Therefore, the wind energy utilization efficiency is still low after deducting the energy consumption. Summary of the Invention

[0006] In view of the defects existing in these current existing technologies, the present invention proposes a blunt trailing-edge flapping-wing wind energy utilization device with surface jetting, combining the advantages of the above passive and active control technologies. It can not only flexibly control the jet volume according to the changes in the oncoming flow conditions, expand the adaptation range of the device, but also have high wind energy utilization efficiency when the jetting is turned off under certain conditions, reducing the demand for external energy input.

[0007] To achieve the above object, the technical solution of the present invention is: a blunt trailing-edge flapping-wing wind energy utilization device with surface jetting, the flapping wing blade adopts a blunt trailing-edge airfoil, and the blunt trailing-edge airfoil is symmetrically thickened at the trailing edge of the airfoil, and the symmetric thickening thickness l t The ratio l t / c to the chord length c of the airfoil is 0.02, and the ratio l p / c of the initial position of the blunt trailing-edge symmetric thickening to the chord length of the airfoil = 0.90; jet ports with a diameter of 0.5%c are opened on the upper and lower surfaces of the blunt trailing-edge airfoil, and the distance from the center of the jet port to the leading edge is 90%c.

[0008] Furthermore, when the flapping wing blade moves from the highest position to the lowest position, the jet ports on its lower surface eject a gas jet with a certain speed perpendicular to the airfoil surface; when the blade moves to the lowest position and starts to flap upward for 1 / 2T, where T is the time for the blade to complete one movement cycle, the lower surface jet is stopped, and the jet ports on the upper surface are opened to eject a jet perpendicular to the airfoil surface, ensuring that the jet is only ejected on the suction side of the flapping wing blade, so as to effectively increase the circulation at the trailing edge of the airfoil and improve the lift of the blunt trailing-edge airfoil.

[0009] Furthermore, a high-pressure air chamber is arranged inside the flapping wing blade, and the high-pressure air chamber is connected to the jet ports on the upper and lower surfaces of the airfoil through internal air paths respectively.

[0010] Furthermore, the flapping wing blade is connected to a swing arm, and two micro air pumps are installed on the upper and lower sides of the swing arm. The micro air pumps are connected to the high-pressure air chamber and the jet ports through air paths, and are used to forcibly eject the pressure air flow from the jet ports to form a high-speed air jet.

[0011] The beneficial effects of the present invention are as follows:

[0012] A blunt trailing edge flapping wing wind energy utilization device with surface jet proposed by the present invention combines the advantages of passive and active control technologies. It can not only flexibly control the jet volume according to the change of oncoming flow conditions, expand the adaptation range of the device, but also have high wind energy utilization efficiency when the jet is closed under certain conditions, reducing the demand for external energy input. Therefore, compared with the prior art, it has the outstanding characteristics of simple structure, wide adaptability, high flexibility and high wind energy utilization efficiency. Brief Description of the Drawings

[0013] Figure 1 It is a schematic structural diagram of a flapping wing wind energy utilization device;

[0014] Figure 2 It is a motion trajectory diagram of a cross-section of a flapping wing of a flapping wing wind energy utilization device within one cycle;

[0015] Figure 3 It is a schematic cross-sectional structure diagram of a blunt trailing edge flapping wing blade with a surface jet orifice;

[0016] Figure 4 It is a comparison result of the wind energy utilization efficiency (η) of a blunt trailing edge flapping wing energy harvesting device and an existing flapping wing energy harvesting device under different working conditions obtained by research;

[0017] Figure 5 It is a schematic diagram of a blunt trailing edge blade with a surface jet and a micro air pump;

[0018] Figure 6 Schematic diagram of the internal structure of the blunt trailing edge blade. Detailed Embodiment

[0019] The present invention will be further described below in conjunction with the drawings and embodiments.

[0020] As Figure 1 , shown in Figure 2, a blunt trailing edge flapping wing wind energy utilization device with a surface jet of the present invention includes a flapping wing blade 1, a swing arm 2, two side end plates 3, and a base 4.

[0021] The flapping wing blade 1 adopts a blunt trailing edge airfoil (as Figure 3 shown, the black solid line is the form of the airfoil of the blade of the existing flapping wing device; the black dashed line is the airfoil of the blunt trailing edge blade with a surface jet orifice proposed by the present invention), that is, symmetric thickening is carried out at the trailing edge of the airfoil. The ratio of the symmetric thickening thickness (l t ) to the chord length (c) of the airfoil, l t / c is 0.02, and the ratio of the initial position of the symmetric thickening of the blunt trailing edge A to the chord length of the airfoil, l p / c = 0.90, that is, the method of rotationally symmetric thickening starting from the trailing edge position of the airfoil is adopted. At this time, the wind energy utilization efficiency of the flapping wing is significantly improved compared with the same type of flapping wing (as Figure 4 shown).

[0022] Jet ports 5 with a diameter of 0.5%c are opened on the upper and lower surfaces of the airfoil (as Figure 3 shown), and the center of the jet port 5 is 90%c away from the leading edge. When the flapping wing blade 1 moves from the highest position to the lowest position, the jet port 5 on its lower surface ejects a gas jet with a certain speed perpendicular to the airfoil surface; when the flapping wing blade 1 moves to the lowest position and starts to flap upward, that is, at 1 / 2T (T is the time for the blade to complete a movement cycle), the lower surface jet is stopped, and the jet port on the upper surface is opened to eject a jet perpendicular to the airfoil surface, ensuring that the jet is ejected only on the suction surface side of the flapping wing blade, so as to effectively increase the circulation at the trailing edge of the airfoil, further improve the lift of the blunt trailing edge airfoil, and then enhance its work performance.

[0023] When the flapping wing blade moves from the highest position to the lowest position, the jet port on its lower surface ejects a gas jet with a certain speed perpendicular to the airfoil surface; when the flapping wing blade 1 moves to the lowest position and starts to flap upward, that is, at 1 / 2T (T is the time for the blade to complete a movement cycle), the lower surface jet is stopped, and the jet port on the upper surface is opened to eject a jet perpendicular to the airfoil surface for alternating jet ejection. Two micro air pumps 8 are installed on the upper and lower sides of the swing arm 2 of the flapping wing device (as Figure 5 shown), and a high-pressure air chamber 6 is arranged inside the flapping wing blade 1, which is respectively connected to the jet ports 5 on the upper and lower surfaces of the airfoil through internal air paths (as Figure 6 shown). The micro air pump 8 is connected to the high-pressure air chamber 6 and the jet port 5 through an air path 7. The micro air pump 8 will provide a pressure air flow for the working medium gas to force the gas to be ejected from the jet port 5 to form a high-speed air jet. According to the change of the oncoming flow, the speed of the jet is changed by adjusting the flow rate of the micro air pump, so as to achieve the purpose of reducing energy consumption and having good variable working condition performance.

Claims

1. A blunt trailing edge flapping wing type wind energy utilization device with surface jet, characterized in that: The flapping blade adopts a blunt trailing edge airfoil, and the blunt trailing edge airfoil is symmetrically thickened at the trailing edge of the airfoil. The symmetric thickening thickness l t The ratio of the chord length c of the airfoil is l t / c is 0.02, and the ratio of the initial position of the symmetric thickening of the blunt trailing edge to the chord length of the airfoil is l p / c = 0.90; jet ports with a diameter of 0.5%c are opened on the upper and lower surfaces of the blunt trailing edge airfoil, and the distance from the center of the jet port to the leading edge is 90%c; a high-pressure air chamber is arranged inside the flapping blade, and the high-pressure air chamber is connected to the jet ports on the upper and lower surfaces of the airfoil through internal air paths respectively; the flapping blade is connected to a swing arm, and two micro air pumps are installed on the upper and lower sides of the swing arm. The micro air pumps are connected to the high-pressure air chamber and the jet ports through air paths, and are used to forcibly eject the pressured air flow from the jet ports to form a high-speed air jet; by combining passive and active control methods, the air injection volume can be flexibly controlled according to the changes in the oncoming flow conditions, expanding the adaptation range of the device. At the same time, closing the jet also has high wind energy utilization efficiency and reduces the demand for external energy input.

2. The flapping-wing type wind energy utilization device with a blunt trailing edge for surface jet according to claim 1, wherein: When the flapping blade moves from the highest position to the lowest position, the jet nozzles on its lower or upper surface eject gas jets with a certain velocity perpendicular to the airfoil surface; when the blade moves to the lowest position and starts to flap upward for 1 / 2T (T is the time for the blade to complete one motion cycle), the jet flow on the lower or upper surface is stopped, and the jet nozzles on the upper or lower surface are opened to eject jets perpendicular to the airfoil surface. By ejecting jets only on one side of the flapping blade, the flow control effect at the trailing edge of the airfoil can be significantly enhanced, and the lift of the blunt trailing edge airfoil can be effectively improved.

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