Rotor for Wind Power Stations
Investigation of the Effectiveness Increase of Wind Power Stations By Means Of Application of Rotors with the Possibility of Change of the Geometry Parameters in Dynamics
Tech Area / Field
- NNE-MEC/Miscellaneous Energy Conversion/Non-Nuclear Energy
- NNE-OTH/Other/Non-Nuclear Energy
- SAT-AER/Aeronautics/Space, Aircraft and Surface Transportation
3 Approved without Funding
Georgian Technical University, Georgia, Tbilisi
Project summaryIt is known that since the existence of rotors there has been abrupt problem of creation of the rotor designs with the possibility of change of the basic geometry parameters in dynamics. It is conditioned with fact that the rotors with fixed pitch (RFP) are not optimal for all stages of operation of units of various purposes. The solution to this problem is possible only by use of the variable geometry rotor (VGR) due to the possibility of simultaneous change of the rotor diameter and also setting angle and twist of blades in dynamics.
As a result of manufacture and test o a demonstration model of the rotor with variable geometry parameters in dynamics the performers of the proposed Project have proved that, for example, for aviation the use of VGR gives a possibility of especially effective optimization of flight of planes with vertical takeoff and landing (VTOL) by provision of maximum diameter and minimum twist in hover mode and, contrary, maximum twist in cruise mode [1-10].
For wind energy installations especially with big powers the use of the VGR enables to widen the range of maximum values of efficiency of the setting during the change of the wind speed in big range from 3 to 20÷22 m/sec and also to provide the workability of the setting at those high speeds of the wind (22÷35 m/sec.), at which the existing settings are unable to work. This problem became especially topical after the accident in Fukushima, Japan as a result of which all the leading countries of the world try maximum to change the part of nuclear energy with other types in the general energy balance of the country. For nowadays for this purpose, unfortunately, there is no more effective method than wind energy by economic and ecological criteria and also potentially mastered volume of energy.
Preliminarily conducted aerodynamic and economic calculations prove that as a result of use of such designs it is possible to increase the annual volume of output of each wind power station as minimum by 100% .
Together with publications of investigators of various countries about the essential effectiveness of use of the VGR in wind energy certify the Resolutions of the International Thematic Workshop “Variable Geometry Rotor (VGR)” that was held in Tbilisi from July 13, 2011 to July 15, 2011.
The objective of the proposed Project is creation of the mechanism of the rotor diameter change combined with the system of compensation of centrifugal forces and provision of calculation range of the twist of blades necessary for the selected type of size of wind energy installations.
With this aim several versions of mechanisms have been developed from which together with the Collaborators will be selected the optimal one for fabrication and tests.
The accuracy of scientific conclusions by means of the acting model will be demonstrated and also the prerequisites of certification of the VGR and Brand Management with the strategic aim will be considered. For the estimation of possibilities for promotion of the VGR to the market will be carried out by preliminary SWOT analysis.
State of the Problem and Conducted Works:
Despite the multitude of works of famous companies and scientists of various countries the VGR problem has not been solved yet. There are lots of patents, which did not find the real realization mainly because of a complexity and insufficient reliability of technical solutions.
The Project participants are competent in the mentioned field. They worked in the International Science and Technology Center (ISTC) on Projects as a result of implementation of which was created an original variable geometry rotor (VGR) with combinations of the diameter and twist change in the flight process. The approach priority has been protected by the patents of the Russian Federation and Georgia.
The control mechanism units for the rotor diameter and blades twist change have been developed. The versatile program of the VGR model tests on the especially designed stand has been carried out. The tensometric and dynamometric measurements of the rotor thrust at various loads have been conducted [11-15].
The priority direction of the applied investigations was also the experimental proof of possibility of at least partial discharge of the mechanism of the rotor diameter change from action of centrifugal forces. In the compensation system of centrifugal forces was used accumulation of energy of the centrifugal forces action in hydro-pneuomo-accumulator during the extension of blades with its subsequent use for partial discharge of the mechanism of the rotor diameter change during the retraction of blades. Several designing versions of the system have been developed from which taking into account the opinions of the Collaborators the optimal one was selected and manufactured. The synchronism of the VGR mechanisms functioning has been proved [6, 7, 9, 11, 13-15].
This design because of the ISTC support received European Patent #08737551.5-2422 PCT/IB2008001041 of April 28, 2008. At present the necessary documentation for acquisition of Patent in the USA is registered and submitted.
The peculiarity of the VGR design is that in the control system of the VGR instead of the jack-screw was used the control by cable, by that many big sized parts in the blade are absent that is very important for the design weight. In this design the diameter increase, i.e. the extension of blades is carried out at the expense of arisen centrifugal forces. The retraction is achieved by means of the hydro-cylinder and special cable the loose ends of which are fixed on the movable parts of blades.
With the aim of the range increase of the twist of blades the rigid casing was changed by elastic elements that are located between the work basic ribs and provide the twist of blades to 28 degrees.
Also the twist mechanisms are updated that are located in the ribs and provide a reliable angle position of separate ribs by the beforehand determined values necessary for various values of the rotor diameter.
Experiments have been conducted for definition of the law of the air flow change along the blade span and the thrust force change at various diameters and speeds of the rotor rotation. A comparison analysis of the obtained results from the data of previous Projects has been conducted.
The results of conducted tests on the all Projects have been reported and approved at the authoritative international scientific and technological conferences and exhibitions; they are patented in proper time and published in scientific articles. In Georgia and Romania the monograph in Russian, Romanian and English has been published.
On the basis of multiple experiments it has been established that for provision of softness of the blades surface at the big twists and increase of reliability of saving profiles at maximum loads it is necessary to decrease the length of elastic elements, i.e. to increase their number.
With this aim a calculation scheme has been compiled for definition of that optimal length of each elastic element at which the errors of violation of softness of the blades surface and the profile change at maximum values of twist will be within the admissible limits.
With the aim of reduction of the blades movable parts and by that the values of centrifugal forces it is desirable to select the easier material for the elastic elements.
For this purpose several versions of setting-up of elastic elements and the technology of their manufacture from various modern materials have been elaborated.
The experiments have also shown that for increase of the positioning precision of the moving parts of blades and by that the iteration of various values of the rotor diameter at different experiments it is expedient to change the hydro-system with mechanical transmissions. This solution also corresponds to the general tendencies extended recently in aviation in accordance with which maximally is attempted to use the possibility of substitution of the hydro-system for mechanical.
For use of the principal solutions to these designs in wind energy installations with high powers one must take into account the fact that the size dimensions and accordingly masses of these designs are much bigger than in aviation. However, must be taken into account the fact that the rotational speed of the above-mentioned wind turbines are not high and are within 20÷30 RPM. Taking into account all these peculiarities and problems for creation of rotors of wind installations with variable basic geometry parameters in dynamics the performers of the proposed Project have several versions of original designing solutions and interesting proposals for energy installations of small, medium and big types of sizes which will be used in the proposed Project.
Together with the Collaborators all these versions will be analyzed and according to the proposed conditions of operation the optimal version of the rotor and test stand for manufacture and testing will be chosen.
Meeting the ISTC Goals and Tasks:
This Project will conduce to the implementation of the ISTC objectives and tasks helping the scientists and specialists connected with weapon more orient their capabilities to the peaceful activities and also to their subsequent integration into the international scientific community. The Project will be conducive to the solution of national and international scientific and technical problems accumulated in the energy system, particularly in organization of additional work places in the Republic and in creation of the necessary conditions for solution to the energy problems of the country.
The scope of activities is characterized by 8 basic tasks that show in details all the carried out stages of the Project and form of accounts of each stage.
The Foreign Collaborators in this Project will play a big and important role as they are rather competent and well-known specialists in the field of energy, aviation, aerodynamics and particularly in experimental and designing aspects of international projects of various profiles. Therefore, they can take active part in the qualified expertise of new designing developments, in specification of compiling plans and methods of conduct of the necessary scientific experiments and search of the newest information materials.
Technical Approach and Methodology:
The technical approaches and methodology are conditioned by the fact that this Project relates to the category of demonstration of technologies. The scientific investigations and designing developments will be directed to the updating of the reliable mechanism of the VGR diameter change combined with the system of compensation of centrifugal forces and the extension of the blade twist range change. This will give the possibility of development of such an approach of demonstration of new designs and technologies, which will conduce to the wide commercialization of the VGR for wind energy installations and also in various fields of engineering.