Flow field characteristic and test on concentration device of concentrated wind energy turbine

Abstract: The hazard of wind shear to large wind turbines cannot be ignored. Concentrated Wind Energy Turbine Generator Systems (CWETS) can increase wind energy density and improve wind energy instability. In order to reveal the flow law of wind energy in a concentrated device, theoretical analysis, numerical calculations, and experimental verification on the concentrated wind energy turbine were carried out. To start, this paper introduces the topic background, reveals the wind shear problem that large wind turbines face, summarizes the research situation of wind turbines wind shear, and presents the research status and advantages of the CWETS. Secondly, the report gives detailed analysis of the concentrated wind energy theory basis, basic thought, technical feasibility, and the relative knowledge of computational fluid dynamics. Then, the concentrated equipment is placed in uniform and parallel to the wind flow in the flow field. With the methods of numerical simulation and test-in-truck experiment, the concentrated equipment is studied. Finally, the concentrated equipment model is set in the flow field with wind speed gradient; using the methods of numerical simulation and tunnel experiment, the traditional concentrated equipment and improved concentrated equipment are studied. The results showed that there was good agreement in the numerical calculation and experiment. Conventional concentrated equipment with the central cylinder of 900mm diameter is fixed in uniform and parallel flow fields when wind fluid flows through the concentrated equipment. First, the close inner surface fluid is accelerated. At 0.22m in front of the middle section of the central cylinder, the speed of the close inner surface fluid is faster than the speed at the center axial fluid. The former speed reaches its maximum near the middle of the central cylinder; then with the axial distance increasing, the flow field comes into being, with the faster speed of the center axial fluid than that of close inner surface fluid. It also can be seen, in the central cylinder with 900mm diameter, the boundary layer effect appears near 50mm away from the inner surface of the central cylinder. Wave crest 1 appears at 0.11m section in front of the middle section; wave crest 2 appears at 0.07m section behind the middle section; wave trough appears at 0.02m section behind the middle section. In the central cylinder with the 300mm diameter, the boundary layer effect appears near 15mm away from the inner surface of the central cylinder. At wind flow sections into the central cylinder and out of the central cylinder, each has a crest, and in the middle of the two peaks is a trough. Uniformity and stability is tested in the experimental wind tunnel, and the wind speed gradient for simulated atmospheric boundary layers in the wind tunnel is also tested. The fluid close to the wall is first accelerated when flowing through the concentrating device. The velocity is greater than the central velocity at 0.22 m before the intermediate section, and then, the central velocity becomes gradually greater than the marginal velocity with the increasing distance. The central cylindrical department has the radial velocity gradient centered in the intermediate axis. The radial velocity gradient in the intermediate section is 2.35 m/s when the flow is 10.74 m/s. For the concentrated equipment models with the same size, values obtained by the numerical calculation are always greater than the experimental data, but the overall trend is the same. The main reason is the simplified numerical simulation model, while the actual constraints of the experiment cannot be embodied in the numerical simulation.