# Simulation Analysis and Experiment of Piezoelectric Pump with Tapered Cross-Section Vibrator
## 6 Experiment  
In order to test the pumping performance of the piezoelectric pump with a tapered cross-section vibrator, a prototype pump was made (Figure 13) and a flow rate testing system was built. The principle of the testing system is shown in Figure 14. During the experiment, the flow rate meter sensing head was installed at the outlet pipe of the piezoelectric pump, the power supply of the flowmeter controller was opened, and the piezoelectric pump chamber was filled with water to ensure that there were no bubbles in the pump chamber. The liquid level at the inlet and outlet of the piezoelectric pump was ensured to be consistent. Finally, the AC power supply of the piezoelectric vibrator was connected, and the piezoelectric pump worked. The controller performed A/D conversion and transmitted the test results to the PC end. The experiment was carried out at room temperature with water as the test medium.  
According to the principle of the testing system, a piezoelectric pump test platform was set up, as shown in Figure 15, and the test equipment mainly included: signal generator, power amplifier, water tank, piezoelectric pump, flow rate meter, power supply, and beaker. Among them, the signal generator and power amplifier provided the driving signal for the piezoelectric pump. The driving voltage of the pump was 150 V, which is the same with the driving voltage used in simulation; the water level at the pump inlet was kept constant by a water tank with an automatic water filling system. The heights of lifting table A and lifting table B were adjusted to ensure the water level in the flume of the water tank was consistent with that in the outlet tube. And the flow rate meter was used to monitor the pumping flow at the outlet.  
Figure 12: Flow rate of simulation.  
Figure 13: Prototype of the piezoelectric pump.  
Based on experience, the working length size L and the fixed end thickness H of the vibrator have a crucial impact on pumping performance. With other sizes fixed, the vibrators were made with different L (52-55 mm) and different H (0.3-0.8 mm) size values. The pumping flow rate of the different size vibrators were tested at the driving voltage of 150 V and driving frequency of 588 Hz. The variation curves of simulation and test values are shown in Figure 16. It can be seen from the figure that the trend of simulation and test values was consistent. When L = 52 mm and H = 0.4 mm, the maximum values of simulation flow rate and test flow rate were obtained simultaneously.  
Figure 16: Test–simulation flow rate contrast.  
Figure 14: Schematic diagram of flow test.  
Figure 15: Pump flow test.  
Further, a piezoelectric pump with the vibrator L of 52 mm and H of 0.4 mm, and all other sizes remaining the same, was used as the experimental prototype. The driving voltage was 150 V, and the driving frequency range was 540-660 Hz. The variation of pumping flow rate with different driving frequencies was tested and compared with the simulated flow rate. The results are shown in Figure 17, where these measured values are compared to the simulated pumping flow rates. It can be seen that the tested flow rate changes in the same trend as the simulated flow rates under different driving frequencies. The maximum flow rate values are both near the driving frequency of 588 Hz, which indicated that the fluid-solid coupling analysis could predict the working performance and changing rules of the piezoelectric pump and the piezoelectric vibrator. The maximum flow rate from the simulation was 400.8 mL/min, and the tested maximum flow rate was 367.7 mL/min. Under the same conditions, the simulated flow rate was greater than the tested flow rate, and the overall error was 9%.