DESC:FIELD OF THE INVENTION:
This invention relates to the field of mechanical engineering, wind energy, aerodynamics, and fluid dynamics.

Particularly, this invention relates to blade profile for a Vertical Axis Wind Turbine.

BACKGROUND OF THE INVENTION:
A vertical-axis wind turbine (VAWT) is a type of wind turbine where its main rotor shaft is set transverse to wind (but not necessarily vertically) while its main components are located at the base of the turbine.

It was observed that existing VAWT technology is plagued with at least the following drawbacks:
a) High Startup wind Speed;
b) Low Power to Weight ratio;
c) Inefficient power production at low wind speed operating range;
d) No retrofitting design;
e) Costly, with 5-6 years payback period;
f) Failure in high cyclonic winds;
g) No modular design.

OBJECTS OF THE INVENTION:
An object of the invention is to provide a blade profile which initiates on lower wind speeds, preferably, when used with vertical-axis wind turbines.

Another object of the invention is to provide a blade profile which increases power to weight ratio, preferably, when used with vertical-axis wind turbines.

Yet another object of the invention is to provide a blade profile, to be used, with vertical-axis wind turbines, such that it can be retrofitted in existing vertical-axis wind turbines.

Still another object of the invention is to provide a blade profile which does not fail in high cyclonic winds.

An additional object of the invention is to provide a modular design of a blade profile, preferably, for use with vertical-axis wind turbines.

Yet an additional object of the invention is to provide a blade profile which improves efficiency, preferably, when used with vertical-axis wind turbines.

Still an additional object of the invention is to provide a blade profile, preferably, when used with vertical-axis wind turbines, reducing costs.

SUMMARY OF THE INVENTION:
According to this invention, there is provided a blade profile for a Vertical Axis Wind Turbine comprising:
- an opening introduced, in a portion of a trailing edge of a conventional airfoil, on its pressure side in order to increase starting torque and power generation at low wind speeds, said opening being defined by a locus of points, as per its cross-section, on a lower surface, starting from a point beyond a midpoint of said lower surface, towards a trailing edge, and ending at the side trailing edge.

In at least an embodiment, said opening being an opening equivalent to about 35% to about 65%, of chord length.

In at least an embodiment, said profile having 50% opening, chord length to airfoil thickness ration of 4.77 : 1.
- aerodynamic drag is enough to angularly displace an associated wind turbine at low wind speeds;
- aerodynamic lift acts more due to high lift-to-drag ratio at higher wind speeds.
thereby, increasing efficiency.

In at least an embodiment, an associated entirety of said blade using said profile, and one or more blades, being located on a locus of points equidistant from a centre which houses a generator.

In at least an embodiment, an associated blade, forming a turbine assembly, angularly displaces about a generator, said opening located circumferentially when considered with respect to said generator, said opening being located on an interior side of said turbine assembly while its upper surface is on the outer side of said entire turbine assembly.

In at least an embodiment, said opening, from an operative top to an operative bottom provides an open cut profile, on a lower surface of a blade, made up on splines without any bends.

In at least an embodiment, chord length being selected from a range of 200 mm to 300 mm in order to extract the maximum torque out of the blades keeping RPM low.

In at least an embodiment, Solidity Ratio being selected from a range of 0.60 to 0.75.

In at least an embodiment, Tip Speed Ratio being selected from a range of 0.5 to 1.5

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
The invention will now be described in relation to the accompanying drawings, in which:
Figure 1 illustrates the custom hybrid open airfoil profile with 50% opening, 250 chord and 52.35mm thickness and designed in such a way so that the aerodynamic drag is enough to rotate the wind turbine at low wind speed of 1.5m/s and at higher wind speeds the aerodynamic lift acts more due to high lift to drag ratio at winds speed of 7m/s and above, giving an efficiency in range between 27% - 34% in low wind speeds and high wind speeds.
Figure 2 illustrates the diameter of the open airfoil blade profile of this invention;
Figure 2A illustrates a complete turbine assembly using bladed made of open airfoil design of Figure 1;
Figure 3 illustrates the height of the open airfoil blade profile of this invention;
Figures 4 and 5 shows a Drag and Lift force graph which clearly depicts that at lower wind speeds drag force is more dominant than lift force hence the blade is able to start rotating at lower wind speeds and at high wind speeds the lift force is more dominant hence generating high efficiency power at higher wind speeds;
Figures 6 and 7 shows the Pressure contour of the custom hybrid open airfoil blade at low and high wind speed;
Figure 8 shows the Velocity contour at high wind speeds;
Figure 9 and 10 shows the static structural analysis (Equivalent stress and Total Deformation) of the blade at 750N force acting due to wind;
Figure 11 illustrates a post-processing result simulated using ANSYS Fluent which can be used to observe air particle interaction with this invention’s turbine assembly.
Figure 12 illustrates a post-processing result simulated using ANSYS Fluent which shows where wind is accelerating and decelerating because of this invention’s turbine motion; and
Figure 13 illustrates a time step torque analysis where the resultant pattern is a torque variation in the turbine, of this invention, with each rotation.

DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
According to this invention, there is provided a blade profile for a Vertical Axis Wind Turbine.

Figure 1 illustrates blade profile, of this invention, with custom hybrid open airfoil profile with 50% opening, 250 chord, 52.35 mm thickness, and designed in such a way that the aerodynamic drag is enough to angularly displace the wind turbine at low wind speeds, typically of 1.5m/s, and, at higher wind speeds, the aerodynamic lift acts more due to high lift-to-drag ratio at winds speed, typically, of 7m/s and above, giving an efficiency in range between 27% to 34% in low wind speeds and high wind speeds.

Figure 2 illustrates the diameter of the blade of this invention.
Figure 2A illustrates a complete turbine assembly using bladed made of open airfoil design of Figure 1.

Figure 3 illustrates the height of the blade of this invention.

In at least an embodiment, the airfoil blade (100), according to this invention, as defined per its cross-section, comprises an opening (20) introduced, in a portion of a trailing edge (10) of a conventional airfoil, on its pressure side. The objective of introducing such an opening is to increase starting torque and power generation at low wind speeds, typically in the range of 3-5 m/s, especially for small wind turbines. According to preferred embodiment, an opening equivalent to about 35% to about 65%, of chord length, = was selected as the lift-to-drag ratio and torque is highest at different wind speeds. Due to this profile, the blade airfoil profile, in outer blades, can, now, utilize aerodynamic drag force as well as aerodynamic lift force. At lower wind speeds, typically, of 1 m/s to 4 m/s, a turbine, which uses this invention’s blades, sets to motion and produces power utilizing aerodynamic drag force and at wind speed greater, typically, than 4 m/s, aerodynamic lift force is the dominant driving force.

In at least an embodiment, the opening (20) is defined by a locus of points, as per its cross-section, on the lower surface, starting from a point beyond midpoint of lower surface, towards the trailing edge (10), and ending at the trailing edge. The entirety of the blade, and one or more blades, is located on a locus of points equidistant from a centre which houses a generator. As the blades angularly displace about the generator, the generator actuates. Thus, the opening (20), is also located circumferentially when considered with respect to a generator; by the opening (20) happens to be on an interior side of the entire turbine assemble while the upper surface is on the outer side of the entire turbine assembly.

In at least an embodiment, the opening, from operative top to operative bottom provides an open cut profile, on a lower surface of a blade, made up on splines without any bends.

It was observed, by the inventors, that this ‘hybrid open airfoil design’ results in low cut in speed and high efficiency power production utilizing both aerodynamic drag and aerodynamic lift force. This design harnesses energy in low and high wind speeds and in turbulent winds as well. This airfoil blade is deemed to be ‘hybrid’ because it utilizes both type aerodynamic forces: aerodynamic drag at low winds, and aerodynamic lift at high winds.

Typically, openness of edge correlates with aerodynamic drag
profile which correlates with aerodynamic lift.

In at least an embodiment, the following configuration, for a Vertical Axis Wind Turbine, was established using the airfoil blade profile of this invention:
Airfoil Type custom hybrid open airfoil design
Number of Blades 3
Camber percent 2.6
Chord Length to Thickness Ratio 4.77 : 1
Cut opening percent 50

In at least an embodiment, the following parameters (chord length, solidity ratio, tip speed ratio) were considered for the airfoil blade profile of this invention:

Chord Length
The chord length is taken to extract the maximum torque out of the blades keeping RPM low. The Torque generated by blades is directly proportional to the Cp (Coefficient of Performance of the turbine). So, after performing multiple iterations in CFD it was found out that 250mm chord gives us the torque which is needed to generate enough power at a certain RPM range. So, Solidity 0.68 is chosen by:

a) Solidity Ratio = (n*c)/d
Where n= number of Blades
c= chord length
d= diameter of the turbine
Low solidity (0.30) = high speed, low torque.
High solidity (>0.80) = low speed, high torque.

b) Tip Speed Ratio (TSR)
The Diameter of the turbine is decided by a parameter called Tip Speed Ratio (TSR refers to the ratio between the inlet wind speed and the wind speed of the tips of the wind turbine blades), as diameter is also an important aspect in choosing chord length. TSR depends on RPM, Radius and wind velocity, so keeping wind speed and RPM constant we found out the diameter needed for our turbine to generate rated power at 150 - 200 rpm.
where,
TSR = (2*p*N*r)/(V*60)
Where N= RPM
r = Radius
V = Wind Velocity

Table 1, below, shows a comparison made between a prior art’s open airfoil design and this invention’s hybrid open airfoil, on the basis of Lift-to-Drag ratio (The lift-to-drag ratio is the amount of lift generated by a blade, divided by the aerodynamic drag it creates by moving through air):
Airfoil type Wind Speed(m/s) Angle of attack Cl Cd L/D
Prior art’s profile (open airfoil design) 3 0 0.219 0.008 48.67
7 0 1.018 0.003 339.33
0.5 1.048 0.003 349.33
15 0 2.850 0.009 320.22
1 3.150 0.008 420.00
Current Invention’s (open airfoil design) 3 0 0.165 0.003 66.00
7 0 0.911 0.004 227.75
3 1.103 0.004 275.75
15 0 1.910 0.009 224.71
4.5 2.600 0.010 260.00
TABLE 1

Figures 4 and 5 shows a Drag and Lift force graph which clearly depicts that at lower wind speeds drag force is more dominant than lift force hence the blade is able to start rotating at lower wind speeds and at high wind speeds the lift force is more dominant hence generating high efficiency power at higher wind speeds.

Figures 6 and 7 shows the Pressure contour of the custom hybrid open airfoil blade at low and high wind speed.

Figure 8 shows the Velocity contour at high wind speeds.

Figures 9 and 10 shows the static structural analysis (Equivalent stress and Total Deformation) of the blade at 750N force acting due to wind.

Table 2, below, shows CFD Data and On-Site Testing Data; for the turbine using the airfoil of this invention.
Wind Speed (m/s) RPM Avg. Torque (N-m) Ct Cp
3 33 0.85 0.206 0.12
4 45 2.27 0.309 0.18
5 67 3.89 0.339 0.24
6 83 5.29 0.32 0.23
7 110 7.26 0.323 0.27
8 144 9.43 0.321 0.3
9 178 12.72 0.342 0.35
10 215 15.23 0.332 0.37
11 242 16.24 0.292 0.34
12 276 16.72 0.253 0.3
TABLE 2

Table 3, below, shows On-Site Testing Data; for the turbine using the airfoil of this invention.
Wind Speed (m/s) RPM Avg. Torque (N-m) Ct Cp
3 33 0.8 0.193 0.11
4 45 2.1 0.286 0.17
5 67 3.62 0.315 0.22
6 83 4.87 0.294 0.21
7 110 6.83 0.303 0.25
8 144 8.6 0.293 0.28
9 178 11.8 0.317 0.33
10 215 13.95 0.304 0.34
11 242 15.2 0.273 0.31
12 276 15.84 0.239 0.29
TABLE 3

The average deviation in CFD data and on-site test data is roughly 7%.

Figure 11 illustrates a post-processing result simulated using ANSYS Fluent which can be used to observe air particle interaction with this invention’s turbine assembly.

Figure 12 illustrates a post-processing result simulated using ANSYS Fluent which shows where wind is accelerating and decelerating because of this invention’s turbine motion; and

Figure 13 illustrates a time step torque analysis where the resultant pattern is a torque variation in the turbine, of this invention, with each rotation.

The following paragraph discusses comparison between the performance of the new custom profile with and without cut

The performance of this invention has been compared in the following two cases:
Case 1. With cut;
Case 2. Without cut (full profile).

Two parameters, i.e. RPM and Cp, were compared to validate self-starting characteristics and better efficiency of the blade profile with cut (this invention) at lower wind speeds. The data obtained by the comparison validates both of these points.
RPM
Wind Speed
(m/s) profile with cut
(this invention) full profile
(prior art)
3 33 0
4 45 0
5 67 15
6 83 40
7 110 64
8 144 98
9 178 150
10 215 205
11 242 245
12 276 291
TABLE 4

Cp
Wind Speed
(m/s) profile with cut
(this invention) full profile
(prior art)
3 0.12 0
4 0.18 0
5 0.24 0.04
6 0.23 0.11
7 0.27 0.17
8 0.3 0.22
9 0.35 0.24
10 0.37 0.29
11 0.34 0.32
12 0.3 0.31
TABLE 5

Technical Advantages:
a) Low startup wind speed, less than 1.5 m/s;
b) High power to weight ratio, 15 W/kg to 20 W/Kg;
c) VAWT technology with highest efficiency, 34% (Experimental);
d) Retrofitting design for easy installation on existing structures;
e) Comparatively cheaper than other models with same tech in the market, payback in 3-4 years;
f) Operation in high cyclonic winds;
g) Modular design enhancing portability.

The TECHNICAL ADVANCEMENT, of this invention, lies in providing an open airfoil blade design configured to utilizes both type aerodynamic forces, aerodynamic drag force at low winds, and aerodynamic lift force at high winds; on account of its design.

While this detailed description has disclosed certain specific embodiments for illustrative purposes, various modifications will be apparent to those skilled in the art which do not constitute departures from the spirit and scope of the invention as defined in the following claims, and it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.
,CLAIMS:WE CLAIM,

1. A blade profile (100) for a Vertical Axis Wind Turbine comprising:
- an opening (20) introduced, in a portion of a trailing edge (10) of a conventional airfoil, on its pressure side in order to increase starting torque and power generation at low wind speeds, said opening (20) being defined by a locus of points, as per its cross-section, on a lower surface, starting from a point beyond a midpoint of said lower surface, towards a trailing edge (10), and ending at the side trailing edge.

2. The profile (100) as claimed in claim 1 wherein, said opening (20) being an opening equivalent to about 35% to about 65%, of chord length.

3. The profile (100) as claimed in claim 1 wherein, said profile having 50% opening, chord length to airfoil thickness ration of 4.77 : 1.
- aerodynamic drag is enough to angularly displace an associated wind turbine at low wind speeds;
- aerodynamic lift acts more due to high lift-to-drag ratio at higher wind speeds.
thereby, increasing efficiency.

4. The profile (100) as claimed in claim 1 wherein, an associated entirety of said blade using said profile (100), and one or more blades, being located on a locus of points equidistant from a centre which houses a generator.

5. The profile (100) as claimed in claim 1 wherein, an associated blade, forming a turbine assembly, angularly displaces about a generator, said opening (20) located circumferentially when considered with respect to said generator, said opening (20) being located on an interior side of said turbine assembly while its upper surface is on the outer side of said entire turbine assembly.

6. The profile (100) as claimed in claim 1 wherein, said opening, from an operative top to an operative bottom provides an open cut profile, on a lower surface of a blade, made up on splines without any bends.

7. The profile (100) as claimed in claim 1 wherein, chord length being selected from a range of 200 mm to 300 mm in order to extract the maximum torque out of the blades keeping RPM low.

8. The profile (100) as claimed in claim 1 wherein, Solidity Ratio being selected from a range of 0.60 to 0.75.

9. The profile (100) as claimed in claim 1 wherein, Tip Speed Ratio being selected from a range of 0.5 to 1.5

Dated this 09th day of March, 2023

CHIRAG TANNA
of INK IDÉE
APPLICANT’S PATENT AGENT
REGN. NO. IN/PA - 1785