A novel piezoelectric screw pump is proposed in this study to improve the output flowrate of piezoelectric valveless pump. Piezoelectric screw pump is composed of a piezoelectric driving system and a screw pump body, which could realize the separation of driving and pump body. The driving system consists of two groups of piezoelectric vibrators and a ring hinge. The piezoelectric vibrators are made of four displacement amplifiers and four piezoelectric stacks. The screw pump body consists of an outer cylinder, a threaded pipe and a screw. The threaded pipe and screw are designed with rectangular threads. A certain clearance exists on their matching surface as the liquid flow channel. The screw pump body is made by 3D printing. This paper introduces the operating principle of the piezoelectric screw pump, and analyzes the factors influencing the output performance by finite element simulation. Four groups of piezoelectric screw pump prototypes with different parameters are made. The simulation results are verified by experiments. The experimental results show that under the driving voltage of 600 V pp , the maximum back pressure of the prototypes is 5.3 kPa, and the maximum flowrate is 71.4 ml min −1 .

No abstract

This study designs, fabricates and tests a piezoelectric pump with the structure of a polystyrene ball check valve. The structure of the check valve consists of three layers of specially designed polymethylmethacrylate plates and six polystyrene balls, which forms a particular three-layer constraint mechanism to limit the lateral and vertical displacement of the balls. The assembly of the ball valve can be completed with a simple placing operation, which simplifies the assembly process of the entire pump. The balls are lightweight, which is beneficial for working at high frequencies. The current design adopts two compressible spaces, and the equivalent analogue circuit of compressible spaces is established and analysed. Experimental results indicate that compressible spaces can alleviate the burden in the actuator and smoothen the flow rate pulsation in the long flow channel. The theoretical analysis and experimental tests reveal that this new piezoelectric pump is self-priming. A high flow rate of 99.6 mL/min and the maximum back pressure of 15.3 kPa are obtained when the pump is driven with a sinusoidal voltage of 448 Vpp at the resonant frequency of 790 Hz.

To improve the speed of a piezoelectric motor based on centrifugal force, a method is proposed on the basis of mass transfer from the rotor to the stator. Multi-degree-of-freedom vibration models are established before and after mass transfer. A mass of 150 g is transferred from the six-hole rotor to the stator. This process increases the rotation frequency of the rotor under the same friction loss and increases the energy fed into the rotor by the stator. The motor operates at a frequency close to the resonance frequency. The change in the initial phase with the operating frequency close to the resonance frequency is analyzed, and the phase adjustment device and the signal processing circuit are designed. Two prototypes, one with and one without mass transfer, are fabricated and measured. As the initial phase is adjusted from 0° to 75°, the motor rotation frequency gradually increases, approaching the resonant frequency of the motor. When the excitation voltage is 790 Vp-p, the speed of the piezoelectric motor with a mass transfer of 150 g reaches 11 004 rpm, which is 89% faster than the speed of that without mass transfer.