Diffuser, power generation device, and hydroelectric power generation system

Abstract

The present invention provides a diffuser, power generation device, and hydroelectric power generation system that can increase power generation by accelerating the flow of water. [Solution] A diffuser in which a water flow entering from a first opening is discharged from a second opening that is larger than the first opening, comprising: an enlarged diameter portion connecting the edge of the first opening and the edge of the second opening; an intake portion having an arc-shaped lip formed on the outer edge of the first opening; and a flange extending outward from the outer edge of the second opening, perpendicular to the central axis connecting the centers of the first and second openings, a diffuser for water flow power generation, a power generation device using the same, and a power generation method.

Description

Technical Field

[0001] The present invention relates to a diffuser, a power generation device, and a water flow power generation system.

Background Art

[0002] As a water flow power generation technology, there is a technology in which a rotating body such as a propeller is rotated using the water flow of the sea or a river, and the kinetic energy of the water flow is converted into electrical energy for power generation. Naturally, the faster the water flow, the greater the amount of electricity that can be generated. For this reason, attempts have been made conventionally to increase the power generation amount by arranging a casing called a diffuser around the power generation turbine to accelerate the water flow. Patent Document 1 describes a power generation device in which a casing that acts as a current collector is arranged around a turbine, and a flow stronger than the natural tidal current hits the turbine. The casing is formed in an annular funnel shape that penetrates from a circular inlet opening toward a larger outlet opening. Patent Document 1 describes that since a vortex is formed on the downstream side of this casing, the pressure near the opening that is the outlet of the casing decreases, the flow of seawater becomes faster, and the power generation efficiency improves.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Although the invention of Patent Document 1 describes that the shape of the casing is funnel-shaped, there is no description regarding a shape that enhances the water flow acceleration effect. For this reason, the inventor considered that by devising the shape of the casing, a further acceleration effect could be brought about, and thus the present invention was completed.

[0005] The present invention aims to provide a diffuser, a power generation device, and a hydroelectric power generation system that can increase the amount of electricity generated by accelerating the flow of water. [Means for solving the problem]

[0006] (1) The invention described in claim 1 is a diffuser for hydroelectric power generation in which a water flow that flows in from a first opening is discharged from a second opening that is larger than the first opening, and comprises an enlarged diameter portion connecting the edge of the first opening and the edge of the second opening, an intake portion having an arc-shaped lip formed on the outer edge of the first opening with a central angle in the range of 90 to 110 degrees, and a flange extending outward from the outer edge of the second opening perpendicular to the central axis connecting the centers of the first and second openings, wherein when a water flow flows perpendicularly into the first opening at a flow velocity of 2 knots, the rate of acceleration of the water flow at the first opening is doubled or more. (2) The invention described in claim 2 is a diffuser for hydroelectric power generation according to claim 1, wherein the enlarged diameter portion forms an inclined surface at an angle of approximately 10 degrees from the central axis, the length of the enlarged diameter portion in the direction of the central axis is 1.5 or less from the diameter of the first opening, and the ratio of the width h of the flange to the radius R of the lip of the intake portion is 1.0 or more and 1.8 or less. (3) The invention described in claim 3 is a power generation device comprising a turbine that rotates by the water flow, a generator that generates electricity by the rotation of the turbine, and a water flow power generation diffuser according to claim 1 that holds the turbine and the generator inside and has a mooring point formed on the outside. (4) The invention described in claim 4 is the power generation device according to claim 3, wherein the turbine blades are positioned closer to the first opening than to the second opening. (5) The invention described in claim 5 is a power generation device according to claim 4, wherein the blades have a pitch angle greater than 0°, and the blades are arranged within a range of approximately 0.1 times the diameter of the turbine, with respect to the point of the minimum inner diameter D of the first opening. (6) The invention described in claim 6 is a hydroelectric power generation system comprising the power generation device described in claim 3 and a mooring rope that is anchored to the bottom of the water and extends from the bottom of the water to the diffuser and is anchored to the mooring point. (7) The invention described in claim 7 is a water flow power generation system according to claim 6, wherein the water flow is an ocean current and comprises a mooring cable that is attached to a floating body floating on the surface of the seawater and extends from the floating body to the diffuser and is attached to the mooring point. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a diffuser, a power generation device, and a water flow power generation system that can increase the amount of power generated by accelerating the flow of water. [Brief explanation of the drawing]

[0008] [Figure 1] This figure shows the shape of the diffuser to which this embodiment is applied. [Figure 2] This is a cross-sectional view illustrating the velocity of seawater around the diffuser to which this embodiment is applied. [Figure 3] This is a cross-sectional view illustrating the velocity of seawater around a diffuser as a comparative example. [Figure 4] This is a cross-sectional view illustrating the change in seawater velocity when the lip and brim are modified. [Figure 5] This figure shows the effect of increasing flow velocity in various shapes. [Figure 6] This is a diagram illustrating the shape of the diffuser. [Figure 7] This diagram shows the requirements for the shape of the diffuser. [Figure 8] This figure shows the distribution of the rate of increase in flow velocity for cases 1 to 8. [Figure 9] This figure shows the distribution of the rate of increase in flow velocity for cases 9 to 16. [Figure 10] This figure shows the flow rate and acceleration rate as results of the simulation. [Figure 11] This figure shows the rate of increase for each case. [Figure 12]A diagram showing the relationship between the lip center angle and the growth rate for different lengths of the flange. [Figure 13] (A) is a front view of the rotating body 21a, (B) is a front view of the rotating body 21b, (C) is a side view of the rotating body 21a, and (D) is a side view of the rotating body 21b. [Figure 14] A diagram showing the relationship between the peripheral speed ratio λ and the output coefficient Cp. [Figure 15] (A) is a front view of a power generation device with a rotating body disposed in the diffuser, and (B) to (F) are diagrams showing cases where the position of the rotating body is shifted little by little within the diffuser. [Figure 16] A diagram showing the relationship between the relative position with the diffuser and the output coefficient Cp in the case of a peripheral speed ratio of 1.5 of the rotating body 21b. [Figure 17] (A) is a diagram showing the relationship between the peripheral speed ratio and the output coefficient Cp of the rotating body 21a with and without a diffuser, and (B) is a diagram showing the relationship between the peripheral speed ratio and the output coefficient Cp of the rotating body 21b with and without a diffuser. [Figure 18] (A) is a diagram showing the flow velocity when the rotating body 21a is disposed at the reference position, and (B) is a diagram showing the flow velocity when the rotating body 21b is disposed at the optimum position. [Figure 19] A diagram showing a power generation device to which the present embodiment is applied. [Figure 20] A diagram showing a power generation device to which the present embodiment is applied. [Figure 21] A front view of a power generation device to which the present embodiment is applied. [Figure 22] A rear view of a power generation device to which the present embodiment is applied. [Figure 23] A diagram showing an example of the water flow power generation system of the present embodiment. [Figure 24] A diagram showing an example of the water flow power generation system of the present embodiment.

Embodiments for Carrying Out the Invention

[0009] Embodiments of the present invention will be described in detail below with reference to the attached drawings. Figure 1(A) is a cross-sectional view showing the shape of a diffuser 10 to which this embodiment is applied. A diffuser is a device with a shape in which the cross-sectional area of ​​the fluid flow path gradually widens. The flow inside a diffuser set to an appropriate shape is amplified compared to when there is no diffuser. The diffuser 10 to which this embodiment is applied has a first opening 20, a second opening 30 which is larger than the first opening, an enlarged diameter section 40, an intake section 50, and a flange 60. Both the first opening 20, which is the fluid inlet, and the second opening 30, which is the fluid outlet, are circular. The first opening 20 is smaller than the second opening 30 on the outlet side. For this reason, the diffuser 10 has an enlarged diameter section 40 which expands from the inlet to the outlet. When viewed in cross-section, the enlarged diameter section 40 is in the shape of a straight line connecting the edge of the first opening 20 and the edge of the second opening 30. The straight line connecting the center of the circle of the first opening 20 and the center of the circle of the second opening 30 is called the central axis of the diffuser 10. The distance of the straight line connecting the center of the circle of the first opening 20 and the center of the circle of the second opening 30 is expressed as length Lt [m]. The enlarged diameter section 40 is inclined at an angle that makes an opening angle θ with the central axis. The diameter of the circle of the first opening 20 is called the inlet diameter Din [m], and the diameter of the circle of the second opening 30 is called the outlet diameter Dout [m]. The diffuser 10 is positioned so that the ocean current flows in through the first opening and out through the second opening. Here, the X direction is the direction of the ocean current field, and is the direction from the center of the circle of the first opening to the center of the circle of the second opening.

[0010] The intake section 50 is formed on the outer edge of the first opening and has the function of collecting or straightening the water flowing into the inlet, with the fluid flowing in the direction of arrow U. Furthermore, it also has the function of shaping the flow at the outer edge of the intake section 50. For example, when viewed in cross-section, the intake section 50 forms a lip with a circular arc shape and a central angle of 105 degrees. The size of the radius R of the arc affects not only the flow inside the diffuser 10 but also the formation of the flow at the outer edge of the intake section 50, as will be described later. The central angle of the circular arc shape of the intake section 50 is not limited to 105 degrees, but may be 60 to 145 degrees. In particular, the central angle of the circular arc shape of the intake section 50 is preferably 90 to 125 degrees. The connection between the arc of the intake section 50 and the enlarged diameter section 40 is made such that the tangent to the arc coincides with the straight line of the enlarged diameter section 40. Therefore, when the water flow enters the opening of the diffuser 10 perpendicularly, the water flows in smoothly without obstruction.

[0011] The flange 60 is formed to extend outward from the edge of the second opening of the diffuser 10 in a direction perpendicular to the central axis (X direction). The flange is a perforated disc-shaped member and is connected to the enlarged diameter portion 40. The width h of the flange affects the formation of the flow at the outer edge of the intake portion 50, as will be described later, and also affects the flow inside the diffuser 10.

[0012] The basic shape of the diffuser 10 has been described above. Next, numerical experiments were conducted to calculate the fluid flow around the diffuser 10 by varying the inlet diameter Din[m], length Lt[m], outlet diameter Dout[m], flange width h[m], lip radius R[m], and opening angle θ[deg] of the first opening 20. The calculation software used was STAR-CCM+Ver.16, a computational fluid dynamics (CFD) calculation software from Siemens. The turbulence model was RANS (Reynolds-Averaged Navier-Stokes), and the eddy viscosity model was k-ω SST (Shear Stress Transport). The grid had approximately 2.2 million grid cells, and the Reynolds number was 6.7 × 10⁻¹⁶. 6 It was calculated as follows. The target average current velocity of the Kuroshio Current in the area where the power generation equipment is actually expected to be installed is 2 knots or more. The simulation was performed under the assumption that a steady current with a velocity of 2 knots (=1.029 m / s) flows vertically into the first opening in the seawater.

[0013] Figure 1(B) is a table showing the calculation conditions for each parameter from Case A to Case I. Here, the inlet diameter Din is fixed at 8m, and the calculation conditions are given by varying the length Lt[m], flange width h[m], lip radius R[m], and opening angle θ[deg]. If the inlet diameter Din and opening angle θ are determined, the outlet diameter Dout is also determined. The flow velocity amplification effect of Diffuser 10 is described as follows: "Excellent" for superior effect, "Good" for moderate effect, and "Acceptable" for any effect. "Excellent" indicates a maximum amplification of approximately 2 times or more, "Good" indicates an amplification of approximately 1.7 times, and "Acceptable" indicates an amplification of approximately 1.2 times.

[0014] First, we examined the opening angle θ. Comparing the cases with an opening angle of 20 degrees (Cases A, B, E) and 10 degrees (Cases C, D, F~I), the amplification effect is not good when the opening angle is 20 degrees. In particular, the only difference between Case D and Case E is the opening angle, which is 10 degrees versus 20 degrees. Regarding the amplification effect, the case with an opening angle of 20 degrees was "acceptable," while the case with an opening angle of 10 degrees was mostly "excellent" or "good," suggesting that an opening angle of 10 degrees is optimal. Note that if the opening angle is smaller than 10 degrees, the diffuser becomes elongated and becomes impractical when considering installation. For this reason, we determined that an opening angle θ of approximately 10 degrees is suitable. The diffusers in Case A, Case B, ..., and Case I will be referred to as Diffuser A, Diffuser B, ..., and Diffuser I, respectively. In all cases A through I, the lip has a central angle of 105°.

[0015] Figure 2 shows the average flow velocity calculated by computational fluid dynamics for case D, and Figure 3 shows the average flow velocity calculated by computational fluid dynamics for case E. In both Figure 2 and Figure 3, the calculations were performed in a flow field with a flow velocity of 1 m / s. The only difference between case D and case E is the opening angle θ, which is 10 degrees and 20 degrees, respectively. A region with an average flow velocity of 2.0 m / s or more appears near the inlet inside the diffuser 10. This indicates that in a 1 m / s environment, the diffuser 10 produced an amplification effect of more than 2 times. Furthermore, lines of constant velocity converge along the straight line of the enlarged diameter section 40 of the diffuser D, indicating that the flow is formed along the straight line of the enlarged diameter section 40. In addition, several vortices are formed behind the flange of the diffuser D. In other words, vortices are formed downstream of the diffuser 10, the pressure near the opening (the outlet of the diffuser 10) decreases, and the flow of seawater inside the diffuser 10 becomes faster.

[0016] On the other hand, in the case of diffuser E shown in Figure 3, the degree of amplification is smaller compared to diffuser D. Furthermore, in the case of diffuser E, it can be seen that the flow formed along the straight line of the enlarged diameter section 40 separates midway. Due to the presence of this separated flow, the flow velocity is slower at the rear of diffuser E. A comparison of Figure 2 and Figure 3 also suggests that an opening angle of 10 degrees is optimal.

[0017] Furthermore, we investigated how the size of the intake section 50 and the flange 60 affects the flow. Figures 4(A), (B), and (C) show the computational fluid dynamics calculation results for diffusers D, H, and I, respectively. In all of these cases, the opening angle θ is 10 degrees, but diffuser D has a flange width h = 2.4 m and a lip radius of 2.0 m, diffuser H has a flange width h = 3.5 m and a lip radius of 3.0 m, and diffuser I has a flange width h = 1.0 m and a lip radius of 1.0 m. The ratio of flange width h to lip radius R is 1.2, 1.16, and 1.0, respectively. In all of Figures 4(A), (B), and (C), when the ratio of flange width h to lip radius R is between 1 and 1.2, the flow outside the enlarged section forms a flow parallel to the straight line of the enlarged section. Therefore, it was found that vortices are easily formed behind the flange of diffuser D, the pressure near the opening which is the outlet of diffuser 10 decreases, and the flow of seawater inside diffuser 10 becomes faster. According to the results of numerous simulations, the ratio of the flange width h to the lip radius R is preferably 1 to 1.2. A ratio of about 0.6 (case G) to 1.8 (case F) does not significantly reduce the internal amplification effect.

[0018] Figure 5 shows the effect of increasing the flow velocity of the diffuser under the various conditions shown in Figure 1. The horizontal axis represents the horizontal distance relative to the length L, and the vertical axis represents the ratio of the maximum flow velocity inside the diffuser to the flow velocity in the seawater environment. As a result, the flow velocity increase effect is greatest near the inlet of diffuser I, with an increase rate of more than 2. Furthermore, even near the outlet of diffuser I (X / L=1.0), the increase rate is maintained at around 1.4 times, indicating that a high increase rate can be maintained inside diffuser I.

[0019] The next highest velocity increase rate after diffuser I is with diffuser D. The velocity increase effect is greatest near the inlet of diffuser D, with a velocity increase rate of approximately 2x. The velocity increase waveforms of diffuser D and diffuser I are very similar.

[0020] The next highest velocity increase is observed in diffuser F. The velocity increase is greatest near the inlet of diffuser F, with a velocity increase of approximately 1.9 times. Even near the outlet of diffuser F (X / L=1.0), the velocity increase is maintained at around 1.35 times, indicating that a high velocity increase can be maintained inside diffuser F.

[0021] The next highest velocity increase is observed in diffuser H. The velocity increase is greatest near the inlet of diffuser H, with a velocity increase of approximately 1.8 times. Even near the outlet of diffuser H (X / L=1.0), the velocity increase remains at around 1.3 times, indicating that a high velocity increase can be maintained inside diffuser H.

[0022] Furthermore, the next highest velocity increase is observed in diffuser G. The velocity increase is greatest near the inlet of diffuser G, with a velocity increase of approximately 1.8 times. Even near the outlet of diffuser G (X / L=1.0), the velocity increase remains at around 1.2 times, indicating that a relatively high velocity increase can be maintained inside diffuser G.

[0023] In diffuser C, the amplification factor is 1.7 times near the inlet, but as the air enters the diffuser from the inlet, the amplification factor drops rapidly, and near the outlet, the amplification factor is less than 1. Therefore, the internal space of diffuser C from the inlet to the outlet cannot maintain an amplification factor of 1 or more. Looking at the waveform of diffuser C in Figure 5, the amplification factor levels off at 1.2 when X / L is around 0.5, and drops to 1.0 or less when X / L is greater than 0.8. In the case of diffuser C, X / L around 0.5 means half of the length of 24 [m], that is, 12m from the inlet. A length of 12m is 1.5 times the length of the inlet diameter of 8m. Therefore, since the amplification factor drops rapidly when the horizontal distance exceeds about 1.5 times the inlet diameter, it can be said that it is preferable for the length of diffuser 10 to be 1.5 times or less the length of the inlet diameter of 8m.

[0024] Furthermore, while diffusers A, B, and E have an acceleration rate of approximately 1.2 times near the inlet, diffusers A and B experience a rapid decrease in acceleration rate within the diffuser's internal space. Although diffuser E maintains an acceleration rate of around 1.2 within its internal space, its amplification rate is inferior to that of diffusers I, D, F, H, and G mentioned above.

[0025] From the results of the above numerical experiments, it was found that diffusers I, D, F, H, and G are suitable shapes for diffuser 10 to improve power generation efficiency. Among them, diffusers I and D are preferred. Next, we will consider the flow when the rotating body 21 is placed inside the diffuser 10. Any of the above-mentioned excellent diffusers can be used for diffuser 10, but here we will use diffuser D.

[0026] We have explained the velocity-increasing effect of the diffuser 10 in seawater, but we also investigated whether the flow velocity increases even when a rotating body 21 is incorporated, and whether there is an optimal position for the rotating body 21. Figures 13 to 18 illustrate the investigation using a rotating body 21 with two types of turbines 24 having different blade shapes.

[0027] The fluid dynamics calculation software used was ANSYS Fluent, with a flow velocity of 2 m / s, a turbine diameter of 3 m, and a density ρ of 1025 kg / m³. 3 , kinematic viscosity coefficient 1.18 × 10 -6 The turbulence model used was k-ω SST (Shear Stress Transport). Three-dimensional steady-state calculations were performed using a turbine-fixed coordinate system, where the coordinates rotate with the turbine. More than six rotational speeds were set, ranging from the stationary state to near the free-spinning speed.

[0028] Here, we further investigated how changing the shape of the inlet opening and the angle of the lip of the diffuser 10 affects the acceleration effect. Of the diffusers D and I shown in Figure 1(B), which had a high velocity-increasing effect, simulations were performed using the basic configuration of an inlet diameter Din of 8m, a length Lt of 8m, and an opening angle θ of 10°, while changing the conditions of the inlet shape, lip angle, and flange length. As shown in Figure 6, conditions were set for cases where the inlet shape is a circular arc of a lip with radius R, and for cases where it is a straight line, which is the chord of the circular arc of the lip. When the intake part of the diffuser is a lip, the connection between the circular arc of the lip and the widening part 40 is made such that the tangent of the arc coincides with the straight line of the widening part. However, when the intake part of the diffuser is a straight line, the straight line of the intake part and the straight line of the widening part form a shape that is a broken line in cross-sectional view. As calculation conditions, conditions were set to further change the central angle α1 of the lip and the flange length h. Specifically, the conditions for cases 1 to 16 shown in Figure 7 were set. In cases 1 to 12, the inlet shape is a lip, and in cases 13 to 16, the inlet shape is a straight line.

[0029] Numerical simulations of axially symmetric and steady-state conditions were performed for diffusers in cases 1-16 using Siemens Star CCM+ CFD software. The flow velocity was set to 2 knots (1.029 m / s), and the calculations were performed without a turbine. The k-ω SST model was used for the turbulence model.

[0030] Figure 8 shows the distribution of velocity increase rates for cases 1 to 8. Figure 9 shows the distribution of velocity increase rates for cases 9 to 16. Figure 10 shows the flow rate and velocity increase rate as a result of the simulation. The velocity increase rate is the ratio of the flow velocity with a diffuser to the flow velocity without a diffuser. The flow rate and velocity rate are average values ​​from the axis center of the opening near the inlet of the diffuser to the inlet surface. Cases 1 to 12 have a velocity increase rate of more than 2, while cases 13 to 16 have a velocity increase rate of less than 1.6. As can be seen in Figure 9, the chord (straight) shape in cases 13 to 16 results in a small velocity increase effect because separation occurs at the corners of the inlet. On the other hand, the lip shape results in a high velocity increase rate because the flow is formed smoothly from the inlet along the inner surface of the diffuser.

[0031] Since the flow rate through the diffuser is constant, the rate of increase at each cross-section is inversely proportional to the diffuser cross-sectional area. If the rate of increase at the inlet with a radius of 4 m is Rin, the rate of increase Ra at the cross-section x [m] (0 < x < 8) from the inlet is expressed by Equation 1.

Equation

[0032] Figure 11 is a diagram showing the rate of increase for each case. The cases where the rate of increase exceeds 2.6 are Case 2, 3, 5, 6, 9, and 10. The cases where the rate of increase exceeds 2.6 are those where the center angle of the lip is 90° or more and 125° or less. In particular, the case with a large rate of increase was Case 9 (lip center angle 106°) with a rate of increase of 2.804. Next, the case with a high rate of increase was Case 5 (lip center angle 90°) with a rate of increase of 2.768.

[0033] Figure 12 is a diagram showing the relationship between the lip center angle and the rate of increase for different lengths of the flange. From Figure 12, it can be seen that the larger the diameter of the flange, the greater the rate of increase effect. Also, as shown in Figure 12, even when the flange is changed, the rate of increase is high around 90° - 110°. Therefore, the center angle of the lip is considered to be optimal at about 90° - 110°.

[0034] Figure 13(A) is a front view of the rotating body 21a, and Figure 13(B) is a front view of the rotating body 21b. Figure 13(C) is a side view of the rotating body 21a, and Figure 13(D) is a side view of the rotating body 21b. Compared with the rotating body 21a, the rotating body 21b has a larger area of the blade 110. And while the pitch angle α of the blade 110 of the rotating body 21a is almost zero, the pitch angle α of the blade 110 of the rotating body 21b is 30°. Both the rotating body 21a and the rotating body 21b have a turbine diameter of 3m.

[0035] Figure 14 shows the relationship between the peripheral speed ratio λ and the power coefficient Cp of the rotating bodies 21a and 21b. In the legend of Figure 14, shape (1) represents the rotating body 21a, and shape (2) represents the rotating body 21b. The peripheral speed ratio λ is expressed by equation 2.

number

number

[0036] Figure 15(A) is a front view of the power generation device 100 with the rotating body 21b positioned in the diffuser 10. The inner diameter of the throat portion (first opening) of the diffuser 10 is set to 1.02 times the turbine diameter D. Figures 15(B) to (F) show cases in which the position of the rotating body 21 is shifted slightly within the diffuser 10. The front-to-back position of the diffuser 10 and the rotating body 21 is determined by using the point where the maximum diameter position of the turbine 24 coincides with the throat as the reference point (0), and then moving forward and backward from there to find the position where the output is maximized. Figure 15(B) shows the case in which the rotating body 21 is positioned at -0.2D, which is the deepest position (downstream side) inside the diffuser 10 from the reference point. Figure 15(F) shows the case in which the rotating body 21 is positioned at +0.2D, which is upstream from the reference point in the diffuser 10.

[0037] Figure 16 shows the relative position of the diffuser 10 and the power multiplier when the peripheral speed ratio of the rotating body 21b is 1.5. The power multiplier is the power multiplier with and without the diffuser. The highest power multiplier occurs when the turbine is positioned 0.1 of the turbine diameter inside the inlet of the diffuser 10. In other words, the power is maximized when the diffuser 10 is positioned about 0.1D behind (downstream) the reference position. This was determined to be the optimal position for the rotating body 21b. It can be seen that the range in which the power multiplier can be maintained at 1.4 or higher is -0.08 to 0.15. A similar study was conducted for the rotating body 21a with a peripheral speed ratio of 3.5, but the output did not increase. Therefore, for the rotating body 21a, the diffuser 10 was placed in the reference position.

[0038] Figure 17(A) shows the relationship between the peripheral speed ratio and the power coefficient Cp of the rotating body 21a with and without a diffuser. In the legend in the figure, "Shape (1)" represents the case of the rotating body 21a alone, and "Shape (1) + diffuser" represents the case where the rotating body 21a and the diffuser 10 are arranged together. From these results, it can be seen that for the rotating body 21a, the power coefficient increases only slightly with or without the diffuser 10, and no significant effect is observed. Figure 17(B) shows the relationship between the peripheral speed ratio and the power coefficient Cp of the rotating body 21b with and without a diffuser. In the legend in the figure, "Shape (2)" represents the case of the rotating body 21b alone, and "Shape (2) + diffuser" represents the case where the rotating body 21b and the diffuser 10 are arranged. From these results, it can be seen that with the rotating body 21b, the power coefficient Cp increases by about three times when the diffuser 10 is attached compared to when the diffuser is not attached. The projected area of ​​the diffuser is approximately four times that of the turbine. Considering that a four-fold increase in projected area means four times the energy of the water flow that can be used, the figure of three times is considered reasonable.

[0039] Figure 18(A) shows the flow velocity in the X direction when the rotating body 21a is placed in the reference position, and Figure 18(B) shows the flow velocity in the X direction when the rotating body 21b is placed in the optimal position. The X direction is the direction of the ocean current field, and is the direction from the center of the first opening of the diffuser 10 to the center of the second opening. With the rotating body 21a, the effect of the diffuser 10 is almost negligible, while with the rotating body 21b, the output is increased by approximately three times due to the diffuser 10. In Figure 18(A), flow separation occurs near the inner wall of the diffuser 10, and the velocity is not increased. In contrast, in Figure 18(B), it can be seen that there is no flow separation near the inner wall of the diffuser 10, and the velocity is increased. It is presumed that the reason for this is that with the rotating body 21a, the pitch at the tip is almost zero (see Figure 13(C)), so the increased velocity flow at the tip of the diffuser 10 cannot be utilized, and instead it becomes a resistance. On the other hand, in the rotating body 21b, the pitch at the tip exceeds 0° and forms a relatively large angle of 30° (see Figure 13(D)). Therefore, it is presumed that this does not create resistance to the water flow and instead guides the flow into the diffuser 10, thus minimizing resistance to the flow.

[0040] Figures 19 and 20 show a power generation device 100 to which this embodiment is applied. In Figures 19 and 20, the diffuser 10 is shown as a cross-sectional view, and the rotating body 21 is shown as a side view. From the experimental results in Figure 5, it was confirmed that the velocity amplification rate by the diffuser 10 is high near the inlet within the inner space of the diffuser 10. For this reason, it is desirable to position the turbine blades 110 closer to the first opening than to the second opening. By positioning the blades 110 in the region with a high amplification rate, high velocity flows can be captured and used for power generation. In particular, it is desirable to position the blades 110 near the first opening, which is near the inlet of the diffuser 10. In particular, as examined in Figure 16, regarding the relative position of the diffuser 10 and the rotating body 21, it is desirable that the turbine 24 of the rotating body 21 be positioned approximately 0.1 in diameter D downstream from the inlet of the diffuser 10.

[0041] The rotating body 21 consists of a turbine 24 that rotates due to ocean currents, a stationary part 25 that does not rotate due to ocean currents, a generator (not shown), and the like. Since the stationary part 25 is connected to a rotating body support member 23 fixed to the diffuser 10, the rotating body 21 is supported and fixed in the inner space of the diffuser 10. In the example in Figure 19, the fixed part 25 is located downstream of the turbine 24. In the example in Figure 20, the fixed part 25 is located upstream of the turbine 24. As long as the rotating body 21 is supported in a predetermined position within the inner space of the diffuser 10, the fixing position of the rotating body support member 23 may be in front of or behind the diffuser 10.

[0042] Figure 21 is a front view of the power generation device 100 in this embodiment. Figure 22 is a rear view of the power generation device 100 in this embodiment. The power generation device 100 consists of a diffuser 10, a rotating body 21, a rotating body support member 23, and a cable support member 28. A generator (not shown) is housed in the rotating body 21, and the generated electricity is ultimately sent to land via a power transmission cable 90. The power transmission cable 90, which is connected to the generator, extends to land along the mooring cable 80. The diffuser 10 used was the diffuser D shown in Figure 1(B). The diffuser 10 has an annularly widened diameter section 40 extending from the first opening 20 to the second opening 30. Both the first opening 20 and the second opening 30 of the diffuser 10 are circular. The second opening 30 of the diffuser 10 is larger than the first opening 20. A pair of horizontal wings 27 protrude horizontally from both sides of the outer surface of the diffuser 10.

[0043] The power generation device 100 is coupled to the rotating shaft of the turbine 24 (see Figure 20) of the rotating body 21, and generates electricity through the rotation of the turbine 24. A power transmission cable 90 is connected to the power generation device 100, and the generated electricity is connected to a power transmission line on land. The power generation device 100 as a whole may be formed such that its buoyancy in seawater is greater than that of gravity.

[0044] Inside the diffuser 10, a turbine 24 with blades 110 attached is supported by a rotating support member 23. The turbine 24 consists of the turbine 24 itself and a fixed part 25. One end of the rotating support member 23 is fixed to the enlarged diameter portion 40 of the diffuser 10, and the other end is fixed to the non-rotating fixed part 25 of the turbine 24, thereby supporting the turbine 24. The rotating support member 23 may be made of metal or a high-strength resin.

[0045] The side end of the mooring rope 80 branches into two and is attached to rope support members 28 located at both ends of the horizontal wings 27 of each diffuser 10. It is preferable that the attachment portion of the mooring rope 80 to the horizontal wings 27 is rotatable. The cable 70 is a cable connecting the power generator 100 to the floating body 130 (see Figure 23) on the sea. The side end of the cable 70 branches into two, and these are attached to cable support members 28 located at both ends of the horizontal wings 27 of each diffuser 10. It is preferable that the attachment portion of the cable 70 to the horizontal wings 27 is rotatable. A power transmission cable 95 connecting the generator and a battery (not shown) mounted on the floating body 130 may be routed along the cable 70.

[0046] Figure 23 shows an example of a hydroelectric power generation system according to this embodiment. The hydroelectric power generation system 500 includes a power generation device 100, a rope 70, a mooring rope 80, a floating body 130, and an anchor 200. The power generation device 100 includes a diffuser 10 and a rotating body 21 (not shown). The diffuser 10 is formed in an annular shape, penetrating from a first opening 20 to a second opening 30. Both the first opening 20 and the second opening 30 of the diffuser 10 are circular. The second opening 30 of the diffuser 10 is larger than the first opening 20. A pair of horizontal wings 27 (see Figure 21) protrude horizontally from both sides of the outer surface of the diffuser 10.

[0047] The power generation device 100, which functions as a hydroelectric power generation unit, includes a diffuser 10 and a rotating body 21 (not shown). A generator (not shown) is built into the rotating body 21. The rotating body 21 converts the energy of the ocean current into rotational energy, and the generator further converts the rotational energy into electrical energy. The electricity generated by the generator is transmitted to land via a power transmission cable 90 and supplied to the power grid, etc. The rotating body 21 can be any mechanism capable of converting the energy of the ocean current into rotational energy, and a rotary turbine or the like can be used. The water depth at which the power generation device 100 floats is preferably a depth where the ocean current is strong. For example, the power generation device 100 is installed to float at a water depth of several tens to several hundreds of meters.

[0048] The floating body 130 is a buoyant structure and is connected to the power generator 100 via the rope 70. The floating body 130 is a buoyant structure. Since the floating body 130 needs to always float above the sea surface, it has buoyancy that balances the force that causes the power generator 100 to sink towards the seabed.

[0049] In Figure 23, the floating body 130 is connected to the power generation device 100 via the cable 70, but the floating body 130 may also be directly connected to the rotating body support column without the cable 70. In this case, the rotating body support column supports the power generation device 100.

[0050] The propulsion device 140, which serves as the propulsion unit, is fixed to the floating body 130, and can move the floating body 130 on the sea surface in any direction by, for example, rotating a motor-driven propeller. The positioning information receiver 150, which serves as the position detection unit, can receive positioning radio waves from positioning satellites such as GPS and measure its own position. One end of the rope 70 is fixed to the floating body 130, and the other end is fixed to the power generator 100.

[0051] The control device 170 determines whether the floating body 130 is in the correct location based on the position information from the positioning information receiver 150. If it determines that the floating body 130 has deviated from its correct location, it drives the propulsion device 140 to move the floating body 130 to the correct location. Since the floating body 130 is always towing the power generator 100 with the rope 70, the power generator 100 can remain in the correct location. The floating body 130 is equipped with an information receiver (not shown) that constantly monitors the center of the Kuroshio Current by receiving weather and oceanographic information.

[0052] The propulsion system 140 is fixed to the floating body 130, and can move the floating body 130 on the sea surface in any direction by, for example, by rotating a motor-driven propeller. The positioning information receiver 150 acquires the absolute position information of the floating object 130. The positioning information receiver 150 functions as a receiver that receives positioning information by radio waves from positioning satellites such as GPS. The positioning information receiver 150 acquires the three-dimensional position information (latitude, longitude, and altitude) of the floating object 130. The positioning information receiver 150 outputs the acquired absolute position information of the floating object 130 to the control device 170.

[0053] The mooring rope 80 is made of a high-strength wire that connects the power generator 100 and the anchor 200. The mooring rope 80 can be any high-strength metal wire treated with corrosion-resistant technology. The power transmission cable 90 is a cable for transmitting the electricity generated by the generator of the power generator 100. The power transmission cable 90 is less strong than the mooring rope 80, so it is wrapped around the mooring rope 80 to prevent any mechanical stress such as tension on the power transmission cable 90. The mooring rope 80 is fixed to the anchor 200 which is fixed to the seabed. From the anchor 200, the power transmission cable 90 extends along the seabed and reaches the land. The mooring rope 80 and rope body 70 mentioned above are made of synthetic fiber rope, for example. When the mooring rope 80 is extended over long distances in water, there is a risk of it breaking due to its own weight, so a material that is lightweight yet strong is desirable. In particular, a rope that has buoyancy in water can reduce the burden of weight.

[0054] The cable 70 is connected to the floating body 130 on the sea surface S3. The side end of the cable 70 branches into two and is attached to cable support members 28 located at both ends of the horizontal wings 27 of each diffuser 10. It is preferable that the attachment portion of the cable 70 to the horizontal wings 27 is rotatable.

[0055] The electricity generated by the power generator 100 can also be transmitted to a battery (not shown) in the floating body 130. For example, a portion of the electricity generated by the generator can be sent to a battery (not shown) inside the floating body 130 via a power transmission cable along the rope 70 for storage. The battery supplies electricity to the motor that drives the propulsion system 140.

[0056] The mooring rope 80 is anchored to the seabed S1 with anchor 200. The mooring rope 80 extends from the seabed S1 toward the diffuser 10. The end of the mooring rope 80 opposite to the seabed S1 is attached to the diffuser 10.

[0057] Anchor 200 is installed on seabed S1 at depths ranging from several tens to several hundred meters. In the case of seabed S1 with sediment, Anchor 200 is fixed by embedding it in the sediment. In the case of bedrock with little sediment, Anchor 200 is fixed by driving piles or bolts into seabed S1. This method of fixing Anchor 200 is difficult in deep waters. Areas with strong Kuroshio Currents often have depths of 1000 meters or more, making it difficult to fix Anchor 200 to the seabed. For these reasons, Anchor 200 is installed on seabed S1 at depths of several hundred meters or less, where installation is feasible.

[0058] By adopting the above configuration, the hydroelectric power generation system 500 can extend the mooring rope 80 and the power transmission cable 90 to a sea area even deeper than the anchor 200 laying point, making it possible to float the power generation device 100 in the deep sea area S2 where the Kuroshio Current flows. Since the distance between the anchor 200 and the power generation device 100 can range from several kilometers to several hundred kilometers, there is a risk that the power transmission cable 90 may break under its own weight. For this reason, it is desirable to entangle the power transmission cable 90 with the mooring rope 80, which is made of a wire with higher strength than the power transmission cable 90. Figure 24 shows an example of a hydroelectric power generation system according to this embodiment. The hydroelectric power generation system 600 in Figure 24 differs from the hydroelectric power generation system 500 in Figure 23 in that it has floating bodies 132, 134, and 136 and ropes 71, 72, and 73 arranged therein.

[0059] Cables 71, 72, and 73 connect the floating bodies 132, 134, and 136 to the mooring lines 80. The further the ocean current is from land, the longer the mooring lines 80 extending from the anchor 200 need to be. This results in a very large weight for the mooring lines 80, which can lead to instability and breakage. Therefore, by connecting the floating bodies 132, 134, and 136 to the mooring lines 80 as described above, the burden of the mooring lines 80's weight is distributed, allowing for stable placement. For example, by placing cables 71, 72, and 73 every 500m, the burden on the mooring lines 80 due to their own weight can be reduced. The lengths of cables 71, 72, and 73 can be adjusted as needed. For example, in areas where a mooring line 80 crosses a shipping lane, the mooring line 80 needs to be installed at a depth greater than the ship's diving depth. Therefore, the cable 71 needs to be extended to a depth greater than the diving depth so that the mooring line 80 does not affect the ship. Furthermore, floating bodies 132, 134, and 136 may also be equipped with a propulsion device 140, a positioning information receiver 150, and a control device 170, similar to floating body 130. [Explanation of Symbols]

[0060] 10...Diffuser, 20...First opening, 21...Rotating body, 23...Rotating body support member, 24...Turbine, 25...Fixed part, 27...Horizontal blade, 28...Cable support member, 30...Second opening, 40...Enlarged diameter part, 50...Intake part, 60...Flange, 70, 71, 72, 73...Cable body, 80...Mooring rope, 90...Power transmission cable, 100...Power generator, 110...Blade, 130, 132, 134, 136...Floating body, 140...Propulsion device, 150...Positioning information receiver, 170...Control device, 200...Anchor, 500, 600...Water flow power generation system, S1...Seabed, S2...Underwater, S3...Sea surface

Claims

1. A diffuser in which a water flow entering from a first opening is discharged from a second opening that is larger than the first opening, An enlarged diameter portion connecting the edge of the first opening and the edge of the second opening, An intake portion having an arc-shaped lip formed on the outer edge of the first opening with a central angle in the range of 90 to 110 degrees, The second opening has a flange extending outward from its outer edge, perpendicular to the central axis connecting the centers of the first and second openings, When a water flow enters the first opening perpendicularly with a flow velocity of 2 knots, the rate of increase in the water flow velocity at the first opening becomes more than double. A diffuser for hydroelectric power generation.

2. The enlarged portion forms an inclined surface that is at an angle of approximately 10 degrees from the central axis. The diameter of the first opening and the length of the enlarged portion in the direction of the central axis are 1.5 or less. The ratio of the width h of the flange to the radius R of the lip of the intake portion is 1.0 or more and 1.8 or less. A diffuser for hydroelectric power generation according to claim 1.

3. A power generation device comprising: a turbine that rotates by the water flow; a generator that generates electricity by the rotation of the turbine; and a water flow power generation diffuser according to claim 1, which holds the turbine and the generator inward and has a mooring point formed on its outside.

4. The power generation apparatus according to claim 3, wherein the turbine blades are positioned closer to the first opening than to the second opening.

5. The power generation device according to claim 4, wherein the blades have a pitch angle greater than 0°, and the blades are arranged within a range of approximately 0.1 times the diameter of the turbine, with respect to the point of the minimum inner diameter D of the first opening.

6. The power generation device according to claim 3, A mooring rope that is anchored to the seabed and extends from the seabed to the diffuser and is anchored to the mooring point, A hydroelectric power generation system.

7. The aforementioned water current is an ocean current, A mooring cable is attached to a floating body that floats on the surface of the seawater, extends from the floating body to the diffuser, and is attached to the mooring point. A water-power generation system according to claim 6, comprising:

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