Experimental Study On Flow Field Characteristic Of Concentrated Wind Energy Equipment In Wind Shear

The research is a part of the National Natural Science Foundation of China Project“Wind Tunnel Experiment and Research on Series Blades of Concentrated Wind EnergyTurbine”[NO:59776033]. The hazard of wind shear to large wind turbines cannot beignored. CWETS (Concentrated Wind Energy Turbine Generator Systems) can increasewind energy density and improve wind energy instability. In order to study the ability ofconcentrated equipment to weaken the hazard to the CWETS from wind shear, thecombination study method of numerical simulation, test-in-truck experiment and the windtunnel experiment are used in this thesis. The main jobs are as follows:At first, this paper introduces the topic background, reveals the wind shear problemof large wind turbines, summarizes the research situation of wind turbines wind shear, andpresents the research status and advantages of the CWETS. Secondly, detailed analysis ofthe concentrated wind energy theory basis, basic thought, technical feasibility and therelative knowledge of computational fluid dynamics is carried. Then, the concentratedequipment model is placed in uniform and paralleled to the wind flow in the flow field,with the methods of numerical simulation and test-in-truck experiment, the concentratedequipment model is studied. At last, the concentrated equipment model is set in flow fieldwhich with wind speed gradient, with the methods of numerical simulation and tunnelexperiment, the traditional concentrated equipment and improved concentrated equipmentare studied. Research results are as follows:(1) Conventional concentrated equipment with the central cylinder of900mmdiameter is fixed in uniform and paralleled flow field, when wind fluid flow through theconcentrated equipment, First of all, the close inner surface fluid is accelerated. In front0.22m of the middle section of the central cylinder, the speed of the close inner surfacefluid is faster than the speed of center axial fluid, the former speed reaches its maximumnear the middle of the central cylinder, then with the axial distance increasing, the flowfield is come into being, which with the faster speed of center axial fluid than the that ofclose inner surface fluid.(2) Uniformity and stability are tested for the experimental wind tunnel, and the windspeed gradient for simulated atmospheric boundary layer in the wind tunnel is also tested;wind shear tests of conventional concentrated equipment model, improved for theconventional concentrated equipment model I and improved concentrated model II arecarried out in this tested wind tunnel. Tests results show that the conventional concentrated equipment has the ability to decrease the influence of wind shear. The conventionalconcentrated equipment can reduce the coming wind speed gradient from4.2/s to3.4/s ofthe central cylinder wind speed gradient and decrease the coming wind gradient by20%.The improved concentrated model I can reduce the coming wind speed gradient from4.2/s to2.08/s of the central cylinder wind speed gradient and decrease the coming windgradient by50%. The improved concentrated model II can reduce the coming wind speedgradient from4.2/s to1.36/s of the central cylinder wind speed gradient and decrease thecoming wind gradient by68%.（3）Wind shear numerical simulation model is set up for concentrated equipmentmodels, and the wind shear values of the concentrated equipments are calculated by takingthe wind speed gradient tested in the wind tunnel as the coming wind speed gradient.Simulated results show the ability to reduce the wind shear of the conventionalconcentrated equipment, of the improved model I and of the improved model II enhancedgradually.（4）Inthe central cylinder with900mm diameter, boundary layer effect appears near50mm away from the inner surface of the central cylinder. In the central cylinder with300mm diameter, boundary layer effect appears near15mm away from the inner surfaceof the central cylinder.（5）The results of the experiments and simulation show, that the concentratedequipment can improve the quality of wind power and load uniformity.（6）It can be seen through the results of the experiments and simulation for theconventional concentrated equipment model, improved concentrated model I andimproved concentrated model II, the numerical calculation results are coincide with theresults of experiments. Values obtained by the numerical calculation are always greaterthan the experimental data. The main reason is the idealized numerical simulation model,while the asymmetric degree and wall thickness of the actual experiment model can not beembodied and constrained in numerical simulation.