CN101705900B - A new type of blade for ocean current power generation turbines - Google Patents

Abstract

A new type of blade for an ocean current power generation turbine, the blade includes a wing root close to the turbine rotor and a wing tip away from the rotor, the cross-section of the blade adopts the NACA series airfoil; the blade The chord length of the blade changes continuously from large to small along the root of the blade to the tip of the blade, and the thickness of the blade gradually becomes thinner from the root of the blade to the tip of the blade. The invention has the advantages of small self-weight of the blades, high efficiency of the turbine, high rotational speed of the turbine with only low velocity seawater, and avoiding cavitation of the blades of the turbine at high rotational speed.

Description

A new type of blade for ocean current power generation turbines

technical field

The invention relates to a blade of a turbomachine, in particular to a blade used for an ocean current power generating turbine.

technical background

Ocean current energy is a clean and renewable energy source. The use of ocean current energy technology to generate electricity is conducive to improving the energy structure and reducing environmental pollution and climate change problems caused by fossil energy consumption. Ocean current energy is the most accessible and flexible energy in ocean energy. The ocean current power generation turbine is to drive the turbine to rotate through the flow of seawater, and convert the kinetic energy of seawater into the mechanical energy of the turbine. Among them, the efficiency, cavitation performance and stability of the turbine are three important indicators affecting the performance of the generating set.

Cavitation is a physical phenomenon unique to flowing liquids. It is a fluid dynamics phenomenon in which cavitation occurs when the partial pressure in the liquid is lower than the vaporization pressure at this temperature. Cavitation in hydraulic machinery will bring Serious consequences. Cavitation will lead to unstable flow, produce severe vibration and noise, reduce its hydraulic performance, cause cavitation damage on the surface of the material, and reduce the service life. During turbine operation, cavitation often begins before it is sufficiently severe to have a measurable effect on the operating characteristics of the turbine. Since the water flow in hydraulic machinery is relatively complex, cavitation can appear in different parts and form cavitation under different conditions. Cavitation often occurs in the flow channel of the turbine runner and on the local surface of its flow-passing parts. Then cause cavitation. In the slight case, only a small amount of corrosion spots are formed on the surface of the blade, and in severe cases, the metal material in the cavitation area of the blade is eroded in large quantities, resulting in a honeycomb-like surface, and even the phenomenon of perforation or edge loss of the blade, which seriously threatens the safe operation of the unit.

Existing turbine blades adopt a two-dimensional airfoil section with equal chord length and equal thickness. The self-heavy weight of this two-dimensional blade consumes a lot of energy for seawater to drive the blade to rotate, resulting in low efficiency of converting seawater kinetic energy into mechanical energy of the turbine, and requires The high speed seawater can make the turbine obtain high speed, and the blades are prone to cavitation and cavitation.

Contents of the invention

In order to overcome the disadvantages of the blades in the prior art that the blades are self-heavy, the kinetic energy of the turbine seawater is converted into mechanical energy, the efficiency is low, seawater with a high flow rate is required to obtain a high speed of the turbine, and the blades are prone to cavitation and cavitation erosion, the present invention proposes a blade with a small weight 1. The efficiency of the turbine is high, cavitation cavitation does not occur, and only low-velocity seawater is needed to enable the turbine to obtain high-speed blades for the turbine for ocean current power generation.

A new type of blade for an ocean current power generation turbine, the blade includes a wing root close to the turbine rotor and a wing tip away from the rotor, the cross-section of the blade adopts NACA series airfoils; it is characterized in that: The chord length of the blade changes continuously from large to small along the root of the blade to the tip of the blade, and the thickness of the blade gradually becomes thinner from the root of the blade to the tip of the blade.

Further, the trailing edge of the blade is a forward concave 1/4 ellipse curve, and the leading edge of the blade is straight.

Further, the ratio of the length of the blade tip to the root of the blade is 1:3.

The concept of the present invention is: gradually shorten the chord length and thickness of the blade from the root of the wing to the tip of the wing, reduce the volume of the blade, reduce the self-weight of the blade, and improve the efficiency of the turbine to convert seawater kinetic energy into mechanical energy. With lower flow rates, the turbine can also achieve high rotational speeds.

The trailing edge of the blade tapers along the direction from the wing root to the wing tip according to the 1/4 elliptic curve, which reduces the flow area of the blade by more than half. The smaller the flow area of the blade, the easier it is for the blade to be supercavitated When the cavity is completely covered, the position of cavitation and cavitation is different, so as to avoid the cavitation of the blade surface at high speed.

The invention has the advantages of small self-weight of the blades and high efficiency of the turbine, only needs low flow rate sea water to make the turbine obtain high rotation speed, and avoids cavitation of the blades of the turbine when the rotation speed is high.

Description of drawings

Fig. 1 is the three-dimensional schematic diagram of the present invention

Fig. 2 is a cross-sectional schematic view of the present invention

Fig. 3 is a longitudinal sectional schematic view of the present invention

Fig. 4 is the relation figure that adopts embodiment two to obtain seawater flow velocity and turbine speed

Fig. 5 is the relation figure of turbine speed and cavitation number obtained by adopting embodiment two

Detailed ways

Embodiment one

Refer to Figure 1-3

A new type of blade for an ocean current power generation turbine, the blade 1 includes a wing root 11 close to the turbine rotor and a wing tip 12 away from the rotor, and the cross section of the blade 1 adopts NACA series airfoils; It is characterized in that: the chord length of the blade 1 gradually becomes shorter along the blade root 11 to the wing tip 12, and the thickness of the blade 1 gradually becomes thinner along the blade root to the wing tip.

The leading edge 13 of the blade 1 is straight, and the trailing edge 14 of the blade 1 is an elliptic curve of a quarter of the front concave.

The ratio of the length of the wing tip 12 of the blade 1 to the length of the wing root 11 is 1:3.

The concept of the present invention is: the blade 1 is gradually shortened along the wing root 11 to the wing tip 12 chord length 15, and the thickness is gradually thinned, so that the volume of the blade 1 is reduced, the self-weight of the blade 1 is reduced, and the turbine converts seawater kinetic energy into Efficiency in mechanical energy, even with low seawater flow rates, the turbines can achieve high rotational speeds.

The trailing edge 14 of the blade 1 tapers along the direction from the root 11 to the tip 12 according to a 1/4 elliptic curve, so that the flow area of the blade 1 is reduced by more than half. The smaller the flow area of the blade 1, the more It is easier to be completely covered by the cavity when supercavitation occurs, because the positions of cavitation and cavitation are different, so as to avoid cavitation on the surface of blade 1 at high speed.

Embodiment two

With reference to Fig. 4,5, in conjunction with actual situation, illustrate present embodiment:

The specific implementation of the present invention will be further described below with the airfoil chord length c as the unit 1.

The cross section of the blade adopts NACA4415 airfoil, the maximum camber f is 4% of the chord length, the maximum camber position x _f is 40% of the chord length from the leading edge, and the maximum thickness d is 15% of the chord length.

The blade adopts an elliptical airfoil whose length ratio between the wing tip and the wing root is 1:3 in the longitudinal section, the length a of the wing tip is about 0.333, the length b of the wing root is 1, the leading edge 1 is a vertical straight line, and the trailing edge gradient line 2 is a quarter elliptic curve $\frac{x^2}{0.667^{2}a}+\frac{{\mathrm{the\; y}}^2}{a}=1.$

Tests have shown that when using the existing two-dimensional airfoil section blades of equal chord length and equal thickness, the average conversion efficiency of the turbine for converting seawater kinetic energy into mechanical energy is 37%. When the blade of the invention is adopted, the maximum conversion efficiency of the seawater kinetic energy into mechanical energy by the turbine can reach 56%, and the average conversion efficiency is 45%.

The content described in the embodiments of this specification is only an enumeration of the implementation forms of the inventive concept. The protection scope of the present invention should not be regarded as limited to the specific forms stated in the embodiments. Equivalent technical means that a person can think of based on the concept of the present invention.

Claims (2)

1. novel blade that is used for ocean current power generation turbine, described blade comprise that NACA series aerofoil profile is adopted in the cross section of described blade near the wing root of turbine rotor with away from the wingtip of described rotor; It is characterized in that: the chord length of described blade along the wing root of blade to the descending continuous variation of wingtip, the thickness of blade along the wing root of blade to wingtip attenuation gradually; Recessed 1/4 elliptic curve before described vane trailing edge is, described blade inlet edge is straight.

2. a kind of novel blade that is used for ocean current power generation turbine as claimed in claim 1, it is characterized in that: the wingtip of described blade and the length ratio of wing root are 1: 3.

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