The Electromechanical Coupling And Distributed Parameter Modeling And Experimental Study Of Piezoelectric Energy Harvester With Wake-induced Vibration

In order to alleviate global warming and reduced carbon emissions,the development of new clean energy has become a hot topic.Piezoelectric energy harvester is a device that can convert fluid induced vibration energy into electrical energy.The available water energy is not limited by topography and landform.It has the advantages of simple structure,long work life,clean and low carbon and has been widely studied in the fields of micro-electronic equipment,self-powered energy system and wireless sensing,etc.At present,most of the researches on piezoelectric energy harvester are focused on wind energy harvesting,while the researches on water energy with higher energy density are rare.The starting velocity of wake-induced vibration is low and the amplitude is large.The research of cantilever piezoelectric energy harvester based on wakeinduced vibration is the key to improve the efficiency of low-speed water flow power generation.On the basis of summarizing the research status and future development direction of piezoelectric energy harvesters,this paper analyzes the key problem existing at present.A cantilever beam piezoelectric energy harvester driven by wake-induced vibration was proposed.The theoretical modeling and experimental test of the piezoelectric energy harvester with wake-induced vibration are carried out.The main work is as follows:(1)Using Hamilton’s principle and Guass’ law,the fluid-structure coupling and electromechanical coupling processes of the cantilever piezoelectric energy harvester were modeled.The distributed parameter model of the fluid-solid-electric three-phase coupling system was established based on the wake-induced vibration theoretical model.The equivalent structure method and Galerkin modal analysis method were used to reduce order,simplify and decouple the coupling model,and the analytical solutions of the output voltage and power of the cantilever piezoelectric energy harvester model were obtained.According to the test results,the parameters were optimized and the theoretical model was verified.(2)An experimental scheme of piezoelectric energy harvesting with wake-induced vibration of flow around double cylinders in open water channel was designed,the energy harvesting characteristics of circular cylinder,D-shaped cylinder and inverted D-shaped cylinder are studied.The flow around three cylinders alone and in pairs and their force characteristics are studied numerically.The experimental results show that the output power of the piezoelectric energy harvester driven by wake-induced vibration of double cylinders is much higher than that of the single-cylinder energy harvester.At the flow velocity of 0.65 m/s,the output power of the Dshaped cylinder,circular cylinder and inverted D-shaped cylinder harvester at the wake of inverted D-shaped cylinder reaches 1169 μW,756 μW and 57.94 μW,which are 287,273 and 37 times of that without wake-induced vibration,respectively.(3)The output power of the wake-induced vibration piezoelectric energy harvester is affected by the spacing and flow velocity.The overall power increases with the increase of flow velocity,increases first and then decreases with the increase of spacing.The flow in the gap between two cylinders has a great influence on the downstream energy harvester.When the flow velocity increases to a certain level,the pressure difference increases,the shear layer passes through the gap,and produces a greater force on the downstream energy harvester,and the output power increases.This phenomenon occurs under the wake of cylinder and inverted D-shaped cylinder,that is,when the upstream surface of the upstream disturbing cylinder is arc face,the reason may be that the vortex wake is more likely to flow to the center line and easier to pass through the gap when flowing along the circular arc face.While the vortex wake flowing along the D-shaped cylinder diverges outwards and it is difficult to pass through the gap.By comparing the influence of the upstream interference cylinder,the downstream cylinder on the output power,it is found that the output power of energy harvester under the wake of inverted D-shaped cylinder is the maximum.The output power of the D-shaped cylinder is the largest.It is shown that the interference characteristics and mechanical characteristics of the cylinder have a great relationship with the shape of the upstream side of the cylinder.The wake flow pattern and the shape of the upstream side affect the output of the energy harvester together.The circular arc surface on the upstream side can produce better wake and the plane mechanical performance is better.