Study On Aerodynamic Characteristics Of Nested Counter-rotating Vertical Axis Wind Turbine

The vertical axis wind turbine(VAWT)has the characteristics of strong wind direction adaptability,high structural strength and low cost.VAWT can realize wind energy conversion in a variety of complex environments and it is an important research direction for future in area of green energy development.Among them,the H-type vertical-axis wind turbine is more suitable for the flow characteristics of the vertical-axis wind turbine because of its simple shape,so the research on the VAWT is mostly carried out around the H-type vertical-axis wind turbine.In this paper,the dynamic stall characteristics of the H-type VAWT are proposed.The layout of the nested counter-rotating configuration is proposed.It is expected that the torque coefficient of the main blade will be improved by the inner layer reversal to the auxiliary blade.The main work of this paper is to carry out numerical values for traditional vertical axis wind mechanism type,2.5D nested reverse configuration VAWT,VAWT with winglet,nested counter-rotating VAWT and nested counter-rotating VAWT with winglet.This paper studied the simulation results through the comparative analysis of the flow field and aerodynamic forces of the 5configurations,and the feasibility of the nested counter-rotating configuration in aerodynamics.The following three sections summarize the main work and conclusions of this article:· Study on aerodynamic characteristics of traditional VAWT based on high resolution solver.The adaptive Grid encryption process is applied to the vortex system in the flow field by using the high-resolution solver developed by the research group.This calculation method improves the resolution of the vortex structure in the wake flow field of the wind turbine,and more accurately reveals the space-time evolution process of the three-dimensional vortex structure.The three-dimensional vortex system of the VAWT mainly includes the wing tip vortex system on the upper and lower sides of the blade and the vortex system extending along the blade.The span vortex mainly includes the leading edge vortex and the trailing edge vortex,which directly affects the pressure distribution on the blade,and is the most direct factor affecting the tangential force and the torque coefficient.The influence of the wing tip vortex on the blade torque coefficient is indirectly reflected in the mutual induction process of the leading edge vortex and the trailing edge vortex,and this induction is enhanced with the decrease of the tip speed ratio.· 2.5D nesting counter-rotating VAWT aerodynamic characteristics.In order to eliminate the induced phenomenon of the wing vortex to the vortex system,the influence of the nested counter-rotating configuration on the dynamic stall characteristics of the VAWT vortex system is studied.The calculation domain is set to 2.5D space.It is found that the configuration can effectively inhibit the dynamic stall phenomenon of the blade.The inner auxiliary blade can promote the leading edge vortex of the main blade to fall off in advance;the downstream blade is in the wake of the inner auxiliary blade,so that the main blade is in the downstream region.The phenomenon of flow separation is weakened.The results of the torque factor indicate that the nested counter-rotating configuration can increase the torque factor of the VAWT,especially at low tip speed ratios· 3D nested counter-rotating configuration VAWT aerodynamic characteristics.In order to extend the nested counter-rotating configuration to the 3D model,this paper first installs the winglet on the wing tip of the 3D VAWT model,and weakens the interference of the wing tip vortex to the expanding vortex system.The results show that the wing tip vortex of the VAWT with small wing is weakened to induce the vortex system,and the torque coefficient is also improved to some extent.Compared with the aerodynamic characteristics of the nested counter-rotating VAWT mechanism type of the winglet,the torque coefficient is not significantly improved due to the complicated three-dimensional vortex interference.