Study On Indirect Excited Piezoelectric Wind Energy Harvester Based On Flow Around A Cylinder

In order to meet the self-power supply requirements,improve the reliability and wind speed adaptability of the micro-power wireless sensor monitoring system in the natural environment,this paper proposes an indirect-excited piezoelectric wind harvest based on flow around a cylinder,The transducer realizes one-way deformation of the piezoelectric vibrator with the shell indirect excitation,and systematically studies it from two aspects of theoretical simulation and experiment.The specific research contents are as follows:1.A COMSOL simulation model of a combined transducer consisting of a piezoelectric vibrator and a bracket was established.The piezoelectric vibrator length ratio(piezoelectric ceramic length to substrate ratio)/ thickness ratio(piezoelectric ceramic thickness to substrate ratio)was studied,the influence of structural parameters such as width and bracket height,additional mass and excitation frequency on the surface stress of the piezoelectric vibrator,the natural frequency of the combined transducer and the output characteristics(output voltage and power).The results show that:(1)The largest surface stress of the piezoelectric vibrator increases with the increase of the length ratio and the height of the bracket,and decreases with the increase of the width and thickness ratio.(2)When the combined transducer works in the first-order mode,the charge polarity on the surface of the piezoelectric vibrator is the same;the natural frequency and the effective stiffness increases with the length ratio/thickness ratio/width and the height of the bracket,and decreases with the increase of the additional mass;(3)The optimal additional mass,load resistance and excitation frequency respectively maximize the output power.2.The COMSOL simulation model of piezoelectric wind harvest is established,and the effects of wind speed,shell diameter,diameter ratio(ratio of spacing to shell diameter)and high parameters on wind field distribution and lift characteristics of shell(amplitude and vortex shedding frequency)are studied.The dynamic model of harvest is established,and the dynamic responses of shell mass and spring equivalent stiffness are studied.The results show that:(1)when there is no spoiler,the lift coefficient is a standard sinusoidal signal,and the frequency of vortex shedding increases with the increase of wind speed and the decrease of shell diameter;(2)when there is spoiler,the coupling relationship between shell and fluid is affected by the parameters of spoiler.When the diameter ratio is between 0 and 1.3 and the height of spoiler is more than 100 mm,turbulence region,lift amplitude and vortex shedding appear on the back surface of shell.The frequency decreases with the increase of diameter ratio/height between spoilers.3.In order to verify the correctness of the theory and simulation results,a harvest test system was built and tested.The time-domain voltage waveform was analyzed by probability density analysis method.The effects of shell/composite transducer quality,diameter ratio/height between spoilers and shell diameter on harvest output voltage and shell amplitude were obtained.On this basis,wind speed and diameter were studied.The results show that:(1)the output voltage decreases with the increase of the shell mass,and there exists an optimum combined transducer mass(65g)to maximize the output voltage,and the shell amplitude decreases with the increase of the shell/combined transducer mass;(2)there is an optimum diameter ratio(about 0.6)/ a high spoiler plate(160mm)/ a shell diameter to make the output voltage/vibration best.The optimum load resistance is 200 K and the maximum output power is 0.28 mW when the ratio of diameters to diameters is 0.57.