Research On Piezoelectric Wind Energy Harvester And Its Dynamic Characteristics

In recent years,technological progress has rapidly promoted the development of the Internet of Things.The wireless sensor network is an application technology of the Internet of Things,and the wireless sensor network technology has been widely used in structural health monitoring and other fields.At present,the main power source of sensor nodes still relies on chemical batteries,but this model has certain drawbacks.Compared with the traditional power supply mode,environmental energy collection technology can provide stable and convenient power supply for miniaturized sensors,and they have great application prospects in wireless sensor systems.Wind-induced vibration energy harvesters utilize the aeroelastic instability characteristics to convert wind energy into vibration energy,while vibration piezoelectric energy harvesters have attracted much attention due to their small size and compact structure.Aiming at the problem of the collection capability of the wind-induced vibration piezoelectric energy harvester under the condition of the working range,this paper systematically studies the piezoelectric wind-induced vibration energy harvester through wind tunnel experiments and numerical simulation methods.First,evaluate the flow field quality of different types of wind tunnels and analyze the wind field environment in Guangzhou;Then,several new piezoelectric wind energy harvesters are designed based on the aerodynamic characteristics of different wind-induced vibrations in wind engineering.At the same time,bistable,multi-modal vibration and lever technology are introduced to enhance the energy capture efficiency of the harvester.Finally,the energy harvesting efficiency of the wind-induced vibration energy harvester is focused on,and the dynamic characteristics of several typical wind-induced vibrations are systematically investigated.In this study,the output performance of the energy harvester prototype was tested through wind tunnel experiments,and the corresponding CFD model was established and the structural control equations were deduced,and then the fluid-structure interaction numerical simulation was carried out using the Fluent software combined with the self-compiled UDF program.The effects of the incoming wind speed on the wake vortex shedding,wind speed distribution and pressure changes on the surface of different bluff body structures were compared and analyzed,and the aerodynamic characteristics of the structures were also analyzed.Then,the influence of load resistance,wind speed and structure type on the energy harvesting efficiency is systematically evaluated.For the square-column wind-induced vibration energy harvesting system,the structure will experience four wind-induced vibration stages,including the upper and lower branches of vortex-induced vibration,the coupling of vortex-induced vibration and galloping vibration,and the complete galloping vibration.obvious coupling effect.When the wind speed increased to6m/s,it was in the transition zone of vortex-induced vibration and galloping vibration.When the wind speed reached 10m/s,it started to completely gallop,and the collector system experienced low-frequency and high-amplitude vibration.Among them,with the increase of wind speed,the main frequency first increases and then decreases,and finally lowers than the natural frequency.The vortex shedding mode also changes and shows a certain regularity.The vortex shedding mode is np+2s,where n increases with the increase of Reynolds number.When the T-shaped bluff body flutters,there is a phase difference between the instantaneous aerodynamic force acting on the structure and the elastic displacement,which makes it possible for the vibrating piezoelectric material to absorb energy from the airflow.However,within a certain wind speed range,the limit cycle vibration will eventually appear and maintain constant amplitude vibration.As the wind speed increases,the aerodynamic forces(lift and torque)also increase,due to the vortex shedding that interferes with the rear structure to a certain extent,accompanied by not very obvious buffeting.In addition,for the nonlinear energy harvester,compared with the results of the linear energy harvester,the nonlinear force between the magnets is an important factor affecting the harvesting efficiency.When the distance between the magnets is relatively large or small,the energy harvesting efficiency will not be significantly improved.Only by reasonably optimizing the distance between the magnets can the performance of the wind-induced vibration-based energy harvesting system be improved.Among them,the voltage and power of the energy harvesting system introduced with magnets are nonlinear with the wind speed.When the wind speed reaches a certain value,the system will break through the potential energy barrier,and its output performance will increase rapidly.The above research content and related achievements have an in-depth understanding of the piezoelectric wind energy harvesting efficiency and dynamic characteristics,providing a reference for the design of wind-induced vibration energy harvesters,and further promoting the application of energy harvesters in structural health monitoring and other fields.