Xiaobiao Shan

A New Mathematical Model for a Piezoelectric-Electromagnetic Hybrid Energy Harvester

This paper presents a new mathematical model of the output power by taking the secondary piezoelectric effect of a piezoelectric-electromagnetic hybrid energy harvester into account. The numerical results show that compared with the single piezoelectric power generator, the optimized external load increases the sytem power output of the hybrid energy harvester by 13.3%. Furthermore, compared with the external load optimization, the damping parameter matching improves the peak output power of the hybrid energy harvester by 23%. Hybrid energy harvesting experiments were carried out to verify the numerical analysis. The experimental results are in accordance with the theoretical results.

Electromechanical modeling and experimental verification of nonlinear hybrid vibration energy harvester

This paper presents a novel nonlinear hybrid energy harvester (NHEH) combining the piezoelectric and electromagnetic harvesting mechanisms. It consists of a piezoelectric cantilever beam with a moving magnet as a part of proof mass and an opposing magnet attached on the frame. In addition, an electromagnetic generator was attached on the beam tip. An electromechanical coupling model of the hybrid energy harvester was established based on energy method. An experimental system was built up to verify the theoretical analysis. Both experiments and simulation show significant improvements in bandwidth and output power from the nonlinear vibration generator. The prototype shows nearly 83.3% increase than the optimized piezoelectric energy harvester in the operating bandwidth at the 1g m/s2 excitation level.

Experimental study on titanium wire drawing with ultrasonic vibration

HighlightsUltrasonic‐assisted wire drawing experimental system design.Unlubricated titanium wire drawing at the room temperature.Comparison of the drawing force and surface finish of the drawn wires.Finite element analysis of the ultrasonic‐assisted wire drawing process. ABSTRACT Titanium and its alloys have been widely used in aerospace and biomedical industries, however, they are classified as difficult‐to‐machine materials. In this paper, ultrasonic vibration is imposed on the die to overcome the difficulties during conventional titanium wire drawing processes at the room temperature. Numerical simulations were performed to investigate the variation of axial stress within the contacting region and study the change of the drawing stress with several factors in terms of the longitudinal amplitude and frequency of the applied ultrasonic vibration, the diameter reduction ratio, and the drawing force. An experimental testing equipment was established to measure the drawing torque and rotational velocity of the coiler drum during the wire drawing process. The result indicates the drawing force increases with the growth of the drawing velocity and the reduction ratio, whether with or without vibrations. Application of either form of ultrasonic vibrations contributes to the further decrease of the drawing force, especially the longitudinal vibration with larger amplitude. SEM was employed to detect the surface morphology of the processed wires drawn under the three circumstances. The surface quality of the drawn wires with ultrasonic vibrations was apparently improved compared with those using conventional method. In addition, the longitudinal and torsional composite vibration was more effective for surface quality improvement than pure longitudinal vibration, however, at the cost of weakened drawing force reduction effect.

Energy harvesting simulation of two piezoelectric flags in tandem arrangement in the uniform flow

At present, energy harvesting from the widely existing fluid in the environment is a hot research field. Piezoelectric flags can be used to generate electric energy with the flow excitation for its positive piezoelectric effect. In this paper, the energy harvesting capacity of two piezoelectric flags in tandem arrangement in the uniform flow is analyzed through 2D numerical simulation. Identical vibration frequency and larger vibration amplitude of the downstream flag are found compared with that of the upstream one. Two coupling modes including the in-phase mode and the out-phase mode are identified. The in-phase mode and out-phase mode can be obtained respectively by arranging the distance of two piezoelectric flags at an odd multiples and an even multiples of adjacent vortexes distance. There are 0 phase difference in in-phase mode and π phase difference in out-phase mode of the vibration as well as the output electric current of two flags. Output power of the downstream piezoelectric flag is larger than that of upstream flag and increases with the separation distance until the maximum energy harvesting capacity of piezoelectric flag. The fixed phase difference of coupled two flags and higher power output of downstream piezoelectric flag indicate that reasonable arrangement of multi-piezoelectric flags in tandem arrangement offers an easier approach to collect the obtained electric energy with post-processing circuit of coupled piezoelectric flags, and higher power can be obtained.

New design of longitudinal ultrasonic vibrator for wire drawing

This paper presents a quarter-wave longitudinal vibrator which is applied to ultrasonic assisted wire drawing. The characteristic of this vibrator is only driven by an axially polarized sandwich PZT stack, which converts electrical energy into mechanical vibration energy. The transducer and horn were designed at the same side of the nodal section to achieve greater vibration at the front of the horn. The four-terminal network method was used to design the vibrator. The finite element method (FEM) was adopted to verify the above design and used for the further analysis about the vibration performances of this vibrator. The numberial caculation results match well with the simulation results. The simulation indicates that the resonance frequency of the longitudinal vibration is about 19.6188u2005kHz and the amplitude of longitudinal vibration at the end of the horn is about 11.48 μm. The present work provides a new longitudinal vibrator for ultrasonic wire drawing.

A piezoelectric energy harvester with vortex induced vibration

This paper presents a piezoelectric energy harvester (PEH) which can convert fluid kinetic energy into electricity with vortex induced vibration (VIV). The PEH is composed by a piezoelectric cantilever beam and a cylinder extension. Dynamic response and energy harvesting of the PEH are studied numerically. It is found that maximum output power can be obtained with optimal resistance and the more power output, the stronger elimination of vibration amplitude. Vibration frequency makes greater contribution on power output at smaller cylinder diameter and decreases with increasing of cylinder diameter. Vibration amplitude plays main role on output power and increases first until reaching peak point with increasing of cylinder diameter. Maximum output power can be obtained with reasonable cylinder diameter.

Dynamic energy harvesting performance of two Polyvinylidene Fluoride piezoelectric flags in parallel arrangement in an axial flow

The dynamic performance and output power of two piezoelectric flags are greatly different from those of a single piezoelectric flag due to the coupling effect of each other. In this paper, the dynamic performance and energy harvesting ability of two piezoelectric flags in parallel arrangement in an axial flow are investigated using immersed boundary-lattice Boltzmann method coupled with Euler-Bernoulli beam and piezoelectric theory, which is fully coupled fluid-structure-electric. A 2D simulation model is presented and a resistance is connected to the piezoelectric flag which is made of Polyvinylidene Fluoride (PVDF). The simulation results show that different vibration phases and coupling modes of two piezoelectric flags are identified, including the in-phase mode, the transition mode and the out-phase mode. When the separation distance of two flags is small, the vibration appears to be the in-phase coupling mode. While the separation distance is large enough, two piezoelectric flags decouple and vibrate individually. Between the in-phase mode and the out-phase mode, the transition mode is found. There is strong interference between each other and the output electric energy seems to be disorders. However, the output power of the piezoelectric flags is nearly identical during the in-phase and the out-phase mode. It means that multi-piezoelectric flags can generate multiple times electric energy in reasonable arrangement compared with a single piezoelectric flag.