The Study Of Con-horizontal Tidal Current Self-pitch Turbine With Dual Rotor

With traditional fossil energy verge of depletion and environmental pollution growing,the countries are increasing the use of clean energy development. The Ocean energy,which iswide distribution, large reserves and high energy density, is considered as the most potentialfor development of new energy in the21st century. Human have converted Ocean energy intoelectrical energy by existing technology. Considering the power generation technology andthe energy conversion levels, The power generation of tide current energy is by far the easiestto realize and the most mature of marine energy generation technology. Today, thepitch-regulated technology is widely used to transform tidal current into power energy. Butthere are many difficulties in the traditional pitch-regulated technology,which are high energyconsumption, huge load of the pitching blade and sealing.In this article, the novel design of pitch-regulated technology is used to sovle theseproblems. The pitch change of propeller can be completed in small range automatically toimprove the energy utilization coefficient without additional power consumption,whichreduces huge load and high energy consumption due to wide range of pitch change. In thispaper, the non-metallic polymer material and plasma sprayed ceramic coating technology isapplied on the premise of meeting load requirements. The non-metallic polymer material isapplied to produce bearing roller. The plasma sprayed ceramic coating technology is used totreat the inner and outer surface of bearing to avoid bearing dynamic seal. Thus this kind ofpitch-regulated system eliminates the maintenance and significantly enhances reliability.For turbine system design issues, this article will focus on a study about the followingaspects:Establishing design theories of the horizontal axis tidal current energy turbine and usingthe momentum theory to analysis capture energy peaks of tidal current energy turbine. Byassuming no airstream among blade elements, we simplify three-dimensional blade into atwo-dimensional blade to study its hydrodynamic performance, and derive the loadcalculation method of the horizontal axis tidal current energy turbine blades. Based on bladeelement-momentum theory, we can further determine the geometric parameters of bladeelements and the relationship between velocity and load of blade elements. The mathematicalmodel of self-pitch turbines can be derived.By the numercial simulate research of flow field, we can use mass equation,momentumequation and energy equation to express the fluid. The numerical solution of the flow fieldcan be obtained by solving these equations. But it is difficult to solve these equations directly,we need to discrete these control equations to obtain linear equations in a predetermined area.At last the iteration method is used to solve these linear equations.According to self-pitch turbine model and its flume tests to verify the feasibility of theself-pitch turbine. Based on blade element-momentum theory self-pitch, turbine can bedesigned and its geometric model can also be builded by three-dimensional mechanical software. Based on the numerical simulate theory, the geometric model can be meshed by useof software Gambit, and the grid file is imported to CFD software Fluent to make iterativesolution. The self-pitch technology is proved to be available by physical model testing andCFD numerical simulation. According to the study, it was effective to enhance the propellertorque, decrease starting pitch flow rate and easy to overcome bearing friction by forwardingpitch axis and increasing leaf area.We design con-horizontal tidal current self-pitch turbine with dual rotor and study itshydrodynamic performance by flume experiments and CFD software. According to flumeexperiments and CFD software, it shows that compared with single fixed blade turbine, thereis a great improvement of efficiency for the con-horizontal tidal current self-pitch turbine withdual rotor; With the installation angle increasing, there is sharp decline in its efficiency, butthe increasement of installation angle contributes to the startup of self-pitch turbine. So for thetidal current energy self-pitch turbine, it is very important to choose the fixed angle. Fortandem distribution of double turbines, there is a large interfere to downstream turbine. Withthe shortening distance between upstream and downstream turbines, the interfere effects todownstream turbine increases gradually. The downstream turbine will produce a delayedeffect on the upstream turbine, which reduces capacitation efficiency of con-horizontal axisdouble turbine system. It is effective to increase the distance of turbines to reduce theinfluence of upstream turbine to downstream turbine and improve the overall efficiency ofpower generation. But for con-horizontal self-pitch turbine with dual rotor, the increasingdistance of turbines will lead to difficulties in processing, increase in the cost of manufactureand maintenance and also reducing reliability of underwater operation.In this paper, we obtain key technology to pitch-regulated of tidal current energyturbine,and the research contributes to laying a technical foundation for industrialization oftidal current energy generator.