# Design and Experimental Verification of a PZT Pump with Streamlined Flow Tubes
## 6 Results and Discussion  
The experimental and simulating flow rate results of the flow tube, under four different orifice pressure differentials of 1000 Pa, 1200 Pa, 1400 Pa, and 1600 Pa, were determined for fluid flow in forward and backward directions. According to the flow resistance test schematic diagram, shown  
Figure 8: Schematic diagram of the flow device. Figure 7: Schematic diagram of piezoelectric oscillator amplitude detection. Figure 9: Traffic test platform. in Figure 6, the pressure differentials can be adjusted by changing the liquid level height H between liquid level and flow pipes. The relationship between liquid level height and pressure difference is  
\[P=\rho gH \tag{16}\]  
where \(P\) is the pressure difference between liquid level and flow tube, \(\rho\) is the liquid density, \(g\) is the gravitational acceleration. The corresponding detail values are shown in Table 3.  
The experimental and simulated flow rate results, under different pressure differences, are shown in Figure 10. As the pressure difference increased, the flow rate increased. Under any pressure difference, the forward flow rate was always greater than the backward flow rate, which proves that the forward flow resistance of the flow tube is less than the backward. According to Figure 10, the trend of the forward and backward flow rate of the streamlined flow tube obtained by simulation was basically consistent with that by experiment. However, the simulated flow rate was larger than the experimental flow rate, as there was significant pressure loss in the peripheral pipe connection system in the actual experiment. The amplitude-frequency relationship of the SLFT PZT pump, form 40-120 V with a step of 20 V, is shown in Figure 11. It can be seen that the amplitude of the center point of the vibrator was positively correlated with the voltage, and these maximum amplitudes were 0.062 mm (40 V, 10 Hz), 0.095 mm (60 V, 10 Hz), 0.136 mm (80 V, 10 Hz), 0.217 mm (100 V, 11 Hz), and 0.228 mm (120 V, 10 Hz), as shown in Figure 11. In the low frequency region (1-25 Hz), firstly, the amplitude of the piezoelectric vibrator increased with the increasing frequency (1-10 Hz), then, when the amplitude increased to a certain value, the amplitude decreased with the increasing frequency (11-25 Hz), and was approximately zero after 25 Hz. In the high frequency region (\(>\)25 Hz), the amplitude decayed with increasing frequency and was accompanied by a few amplitude peak points. These peak points were related to the characteristic properties of the piezoelectric vibrator [16]. Figure 10: Flow resistance experiment and simulation. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Density (\(\rho\))**} & **Gravitational** & \multirow{2}{*}{**Pressure Difference (\(P\))**} & **Liquid Level Height (\(H\))** \\  & **Acceleration (\(g\))** & & 1000 Pa & 0.102 m \\ \hline \multirow{4}{*}{\(1\times 10^{3}\) kg/m\({}^{3}\)} & & 1200 Pa & 0.122 m \\  & & 1400 Pa & 0.143 m \\ \cline{1-1}  & & 1600 Pa & 0.163 m \\ \hline \hline \end{tabular}
\end{table} 
Table 3: The relationship between pressure difference and liquid level. The measured flow-rate-frequency relationships of the SLFT PZT pump at different voltages are shown in Figure 12. It is obvious that the flow rate was positively related to the voltage, and that the overall trends of flow rate were basically consistent with the amplitude-frequency trend. The output flow rate increased with the driving frequency increase, before 11 Hz, and the output flow decreased with the frequency increase after 11 Hz. After the frequency reached 35 Hz, the output flow remained zero. These maximum flow rates of different driving voltages were 4.79 mL/min (40 V, 10 Hz), 7.61 mL/min (60 V, 10 Hz), 10.5 mL/min (80 V, 10 Hz), 16.45 mL/min (100 V, 11 Hz) and 17.01 mL/min (120 V, 10 Hz) respectively.