Study On A Pipe Airflows Energy Harvester With Longitudinal Vibration Based On Piezoelectric Simple Beam

In order to meet the self-powered demand of the pipeline flow monitoring system,a pipe airflows energy harvester with longitudinal vibration based on piezoelectric simple beam(PAPEH)is proposed to solve the problem of effective excitation of a piezoelectric vibrator in a flow-rate/direction constant and space-limited pipeline flow environment.The characteristics of power generation are studied theoretically and experimentally.The main contents are summarized as follows:1.The piezoelectric vibrator is a key feature of the PAPEH and directly affects the power generation performance of the PAPEH.According to the theory of piezoelectric and material mechanics,the finite element model of piezoelectric simple beam was established using COMSOL finite element software.The influence of the structural parameters(length,width and thickness ratio)of the piezoelectric vibrator,additional mass and external load(static load and sinusoidal force.)on its structural stress,natural frequency,and power generation performance(output voltage and power)were studied.The results show that changing the structural parameters of the piezoelectric vibrator can adjust its compressive strength,natural frequency and optimal load;the natural frequency decreases with the length and the additional mass,and increases with the increase of width,thickness ratio and static load;the piezoelectric vibrator should be guaranteed to operate in a first-order vibration.When the exciting force is constant,a smaller thickness ratio is used and the load and the natural frequency are matched to achieve the maximum power output.2.According to the vortex-induced vibration theory,the working principle of the PAPEH is described,and the COMSOL finite element model of the vortex excitation force is established.The lift coefficient and drag coefficient(CL and CD)is extracted by the reaction force operator.The key factors affecting the amplitude-frequency characteristics of the vortex excitation force(flow velocity,spoiler thickness and width ratio)are given,and the variation law such as frequency,mean and amplitude of CL and CD is obtained;based on the Morrison equation,the dynamic model of the PAPEH is established and calculated.The influence of the relevant parameters on its output performance was obtained.The results show that the vortex-induced force(drag force)is a forward-biased harmonic force whose amplitude and frequency increase with the increase of flow rate;the presence of hb(10mm)maximizes the amplitude of flow force and is preferably thin.An ideal vortex force flow stimulating effect can be obtained with an appropriate width ratio(between 0.6 and 0.93);the optimal flow rate makes the amplitude of the piezoelectric oscillator peak,and the optimal flow rate increases with the increase of system stiffness,and decreases with the increase of the additional mass.3.In order to verify the correctness of the theory and simulation,prototypes were made and tested.Probability density analysis was used to extract the voltage amplitudes for the characteristics of output voltage waveforms(non-sinusoidal waveforms).The effect of diameter ratio,spoiler thickness,pre-pressure and additional mass on the output voltage of the PAPEH was analyzed.The optimum structure parameters of the PAPEH were selected to test the load power characteristics.The influence of the flow velocity,diameter ratio and load resistance on the output performance of the PAPEH was obtained.In this paper,the feasibility of the PAPEH to generate electricity through longitudinal excitation of pipeline airflow is realized.The results show that optimal flow rate decreases with the increase of the diameter ratio,and the peak voltage is the maximum when the diameter ratio is 0.93.By changing the pre-pressure and additional mass,the output voltage of the energy harvester can be adjusted.When the diameter ratio is 0.93,the maximum output power is 1.25mW,and the best load resistance is 240K?.