Research on the performance of a valveless piezoelectric pump with a herringbone bluffbody.

Aiming to improve the output performance of a valveless piezoelectric pump, this article presents a valveless piezoelectric pump with a herringbone bluffbody. The bluffbody is herringbone shaped and distributed in a tapered chamber. The tapered chamber and the bluffbody create a large reverse resistance in the chamber, thus effectively mitigating the backflow problem of the valveless pump. The theoretical analysis determined the relationship between the flow rate and the flow resistance coefficient as well as the variation of the pump chamber volume. It was also concluded that the piezoelectric pump has the best output flow at intrinsic frequencies. Through simulation calculations, the effectiveness of the bluffbody structure in mitigating backflow in piezoelectric pumps is analyzed to provide a reference for experimental prototype design parameters. Finally, a range of prototypes is produced for experimentation. The experimental results show that the designed bluffbody shape can increase the return energy loss to effectively mitigate the return flow issues of the valveless piezoelectric pump, thus improving the output performance. The optimum output flow rate is 158.5 ml/min at 200 V and 52.5 Hz and the tapered chamber angle of 6°, and the bluffbody height, angle, and quantities are 2 mm, 40°, and 2, respectively. The construction of the valveless piezoelectric pump proposed in this research can be used as a reference for subsequent improvements in the performance of valveless piezoelectric pumps, and due to the high output performance, experimental studies can be carried out in applications such as dispensing and heat dissipation in electronic products.

Performance analysis of a novel flat lay-type synthetic jet pump with Y-shaped jet chamber.

Recently, synthetic jet pumps have been expected to be used in electronic heat dissipation devices due to the vortex suction phenomenon for transporting fluids. Aiming to improve the delivery ability of the jet pump to output fluid continuously, a novel flat lay-type synthetic jet pump (FLTSJP) with a Y-shaped jet chamber is proposed in this paper. Based on the synthetic jet effect, the pump chamber continuously outputs fluid in one cycle. The output performance of FLTSJP is theoretically analyzed to be affected by the outlet cone angle. The one-cycle flow mechanism of the fluid in the Y-shaped jet chamber is simulated. FLTSJP is manufactured, and a test system is built. Experiments show that the Y-shaped jet chamber effectively improves the output performance. The optimum flow rate and outlet pressure were both reached at 160 V and 40 Hz, which were 20.63 ml/min and 333.43 Pa, respectively. This FLTSJP effectively improves the output performance of synthetic jet pumps and provides a new research concept of water-cooled devices for electronic heat dissipation.

Performance study of a valveless piezoelectric pump with built-in semi-arc bluffbody antique tower channel.

According to the bluffbody bypass effect, the irregular bluffbody can be used to improve the valveless piezoelectric pump. This paper designs a semi-arc bluffbody based on the bluffbody bypassing principle to alleviate the phenomenon of fluid backflow. The fluid passes through the shape of the antique tower to further enhance pumping efficiency. A positive fluid flow mechanism in the pump cavity is theoretically derived. The simulation of the velocity and pressure distribution in the tower-shaped channel of the pump cavity leads to the conclusion that the forward flow has better performance than the reverse flow, and the correctness of the theory is also verified. Experiments further proved that the volume of fluid in the forward direction was reduced by 10.8% when compared to the reverse direction. The study of the height of different semi-arc bluffbody and the angle of the tower trough shows that as the height and angle increase, the flow rate grows first and then reduces. The maximum flow rate is 243.83 ml/min when the bluffbody height is 4 mm and the channel angle is 20° (220 V, 85 Hz).

Piezoelectric energy harvesting systems using mechanical tuning techniques.

In this review, we review the recent research progress and results of piezoelectric energy harvesters applying mechanical tuning techniques in terms of literature background, methods of mechanical tuning, and practical applications. In the past few decades, piezoelectric energy harvesting techniques and mechanical tuning techniques have received increasing attention and made significant progress. Mechanical-tuning techniques are those that allow the resonant vibration energy harvesters the mechanical resonant frequency values to be adjusted to coincide with the excitation frequency. According to the different tuning methods, this review classifies mechanical-tuning techniques based on magnetic action, different piezoelectric materials, axial load, the variable center of gravity, various stresses, and self-tuning and summarizes the corresponding research results, comparing the differences between the same methods. In addition, the current application of the mechanical-tuning techniques is introduced, and the future development of mechanical tuning techniques is analyzed, facilitating the reader to better understand how mechanical-tuning techniques can improve the output performance of energy harvesters.

Research on nonlinear isometric L-shaped cantilever beam type piezoelectric wind energy harvester based on magnetic coupling.

Harvesting wind energy using piezoelectric materials is expected to be an alternative solution for powering wireless sensing networks. This paper proposed a nonlinear isometric L-shaped cantilever beam type piezoelectric wind energy harvester based on magnetic coupling (L-PWEH). The transducer consists of an array of equidistant L-shaped piezoelectric vibrators that are sealed inside the shell. It greatly improves the equivalent piezoelectric coefficient, robustness, and wind speed range for reliable operation. Theoretical and simulation analyses of the structural parameters related to the widening of the L-PWEH were performed. The prototype was built and the experimental system was constructed to verify the feasibility of the L-PWEH and the results of the analyses. Experiments have shown that increasing the magnetic force, additional springs, and the appropriate quantity of excitation magnets can effectively increase the output voltage and widen the wind speed range at high voltage output. When the wind speed is 16.35 m/s and the load resistance is 2 MΩ, the best output power of the piezoelectric vibrator is 142.3 µW. At this time, the height of the middle excitation magnet of the prototype is 12 mm, the number is 5, and the wire diameter of the additional spring is 1 mm. The prototype can successfully make the electronics work properly.

A piezoelectric-driven resonant unit for high-viscosity-liquid injection.

In this paper, a piezoelectric-driven resonant unit for high-viscosity-liquid injection is introduced. For high-viscosity-liquid delivery in low voltage and frequency, a vibrating block is fixed under the rectangular piezoelectric actuator, to transport the vibration to the chamber, leading the unit into resonant state. The valveless chamber is designed eccentrically to promote the tendency of positive flow and diminish the backflow. Numerical simulation and analyses are carried out to optimize the chamber design, and the experiments with liquid in different viscosity, radius of the vibrating block, and the influence of gravity are conducted. The unit achieves a fast delivery speed with a relatively high liquid viscosity compared to the similar study, as the highest flow rate of 52.4, 88.4, and 103.9 ml/min at 100 V, 60 Hz with the liquid of 54.42, 21.13 cP, and water, respectively. The flow rate drops by 40.7%, while the liquid viscosity increases 157.5%.

A compound cantilever beam piezoelectric harvester based on wind energy excitation.

In this paper, a compound cantilever beam based piezoelectric energy harvester (CCBPH) is proposed. This piezoelectric energy harvester uses vibrations caused by vortex excitation behind the winding fluid to harvest wind energy. In particular, this structure uses vortex excitation formed behind a vertically suspended cylindrical winding fluid to cause the vibration of the cylindrical winding fluid, which then indirectly excites the piezoelectric element. The CCBPH consists of a fixed support, a cantilever beam, magnet-1 and magnet-2, a support beam, two piezoelectric units-PVDF (polyvinylidene fluoride), a compound cantilever beam, and a cylindrical winding fluid. We investigated the parameters affecting the structure and verify the effectiveness of the energy harvester through the design of the structure, simulation analysis, and experiments. The experimental results show that the CCBPH can obtain the maximum output voltage from the energy harvester at a wind speed of 18 m/s. The maximum output power was achieved with an external load resistance of 2000 kΩ. By comparison, it is found that the maximum output power is 0.095 mW when the distance between two magnets is 20 mm and the mass ratio is 1:2 for copper.

Numerical simulation and experimental verification of a valveless piezoelectric pump based on heteromorphic symmetric bluff body.

To improve the output performance of valveless piezoelectric pumps, this paper designed a heteromorphic symmetrical bluff body based on the Karman vortex street principle, to optimize the flow direction and velocity of the liquid. The bluff body dome height, trapezoidal unilateral angle, and rounded corner structure height at different dimensional parameters and their relationship with the pump performance were studied. The pump pressure in both positive and negative directions was simulated and analyzed. At last, a prototype of the pump was made and the output performance was tested. The experimental results show that the maximum flow rate reaches 220.6 ml/min at 190 V, 45 Hz when the bluff body dome is 8 mm, the trapezoidal unilateral angle is 5°, and the rounded corner structure is 6 mm. Moreover, when the driving voltage is 190 V and the driving frequency is 130 Hz, the maximum output pressure reaches 670 Pa.

Development of an inertial piezoelectric pump with separable chamber.

This paper presents an inertial pump with rectangular piezoelectric actuators. The mass block adhered at the free end of the actuator increases the actuator deformation, and the pump chamber is separable. Theoretical and experimental analyses are conducted. The different drive modes with the mass block, different excitation electric signals, and their influence on the performance of the piezoelectric pump are investigated. The drive mode is divided into the mass block adhered with two rectangular piezoelectric actuators, one of the actuators, and actuators without mass blocks. The square wave, sine wave, and triangle wave constitute different excitation electric signals. The experimental results prove that the pump with the mass block adhered with two rectangular piezoelectric actuators and driven by the square wave has a wide working frequency range and high performance. The highest flow rate reached is 72 ml/min at 160 V, 20 Hz. The pump with the mass block adhered with one of the actuators and driven by the square wave generates the loudest noise of 97.6 dB at 160 V, 35 Hz.

Research on a large opening and high flow rate piezoelectric pump with straight arm wheeled check valve.

Piezoelectric pumps are applied in cooling systems of microelectronic devices because of their small size. However, cooling efficiency is limited by the low flow rate. A straight arm wheeled check valve made of silica gel was proposed, which can improve the flow rate of piezoelectric pumps, solve the influence of glue aging on the sealing ability of a wheeled check valve, and reduce the size of piezoelectric pumps. This paper discusses the influence of the valve arm number (N = 2, 3, and 4), the valve arm width (W = 1.0, 1.2, and 1.4 mm), and the valve thickness (T = 0.6, 0.8, and 1.0 mm) on the flow rate characteristics of piezoelectric pumps. When valve opening rises, the flow rate increases. The simulation results show that valves with 2 valve arm number, 0.6 mm valve thickness, and 1.0 mm valve arm width have maximum valve opening. The experimental results show that piezoelectric pumps with different valve parameters have different optimal frequencies. In addition, the maximum flow rate is 431.6 ml/min at 220 V and 70 Hz. This paper provides a reference for the application of piezoelectric pumps in cooling systems.

Design and study of an integral valve piezoelectric pump with a novel working mode.

In this paper, an integral valve is proposed by connecting the inlet cantilever valve and the outlet cantilever valve with a connecting post and a rubber circle plate structure. The integral valve changes the traditional inlet cantilever valve and outlet cantilever valve to work independently and realizes the joint response of the inlet cantilever valve and the outlet cantilever valve. The integral valve was designed, manufactured, and installed, and the performance of the static experimental test equipment of the valve and that of the experimental equipment of the piezoelectric pump were evaluated. The static performance of the integral valve was tested. In addition, the performance of the integral valve piezoelectric pump and the cantilever valve piezoelectric pump was tested and compared. The experimental results show that the integral valve piezoelectric pump reaches up to 270.2 ml/min at 210 Vrms, 45 Hz; the pressure can reach 86.2 cmH2O at 40 Hz. Compared to cantilever valves, integral valves have less forward flow resistance and better reverse shutoff. In particular, the pressure of the integral valve piezoelectric pump can be significantly improved compared to the cantilever valve piezoelectric pump. In terms of efficiency, the integrated valve piezoelectric pump will have better performance in the low-frequency region.

Parametric analysis of the output performance of a valveless piezoelectric pump with a bullhorn-shaped structure.

In response to the serious problem of backflow in valveless piezoelectric pumps, this paper proposes a valveless piezoelectric pump with a bullhorn-shaped structure. In this paper, we analyze the flow guide by using the "tail flow space pressure comparison method" and "fluid unit dynamic analysis method," revealing the working principle of the flow guide in the valveless piezoelectric pump. The effects of the height, sharp angle, and filter angle of the bullhorn-shaped structure on the output flow were investigated separately by the experiment. The experimental results show that the output flow rate is best when the height of the bullhorn structure is 2 mm, the choke of the bullhorn-shaped structure is 2, and the sharp angle and fillet angle are 180°. The output flow rate of this valveless piezoelectric pump can reach 170.6 ml/min at a drive voltage of 210 V and a drive frequency of 45 Hz, indicating that the valveless piezoelectric pump has good pumping capability and can effectively alleviate the backflow phenomenon. This study offers some valuable insights into improving its performance and practical application.

Research and experimental verification of the characteristics of asymmetric multi-stage fluid guiding body piezoelectric pump.

Valveless piezoelectric pumps usually have less flow than valve piezoelectric pumps, but the valve piezoelectric pumps have some limitations, such as high cost, complex structure, and difficult installation. In order to solve the problem of the low flow rate of the valveless piezoelectric pump, a valveless piezoelectric pump with multi-stage fluid guiding bodies is proposed. Based on the structure and working principle of the piezoelectric pump, the forward energy loss equation is established, and analysis on parameters affecting the energy loss of the pump is then conducted. COMSOL Multiphysics is adopted to construct a two-dimensional model of velocity and von Mises stress distribution. The valveless piezoelectric pumps were then fabricated based on 3D printing technologies, and the prototypes were tested. The results show that the output performance of the pump is the best when the working voltage is 220 V, the frequency is 95 Hz, the length of the oblique arm of the fluid guiding body is 3.5 mm, the spacing is 9.05 mm, and the thickness is 0.1 mm. The maximum flow rate is 520.6 ml/min. In addition, the experimental results prove that the asymmetric fluid guiding body placed in the center of the pump chamber can improve the performance of piezoelectric pumps. This study extends the application of piezoelectric valveless pumps in micromechanical cooling.