Effects of the geometry of impinging surface on the pressure oscillations of self-resonating pulsed waterjet

Abstract

A preliminary experimental investigation was performed with a focus on the axial pressure oscillations of self-resonating pulsed waterjet under different impinging surfaces. Five target plates of different impinging surfaces were impinged by self-resonating pulsed waterjets at various standoff distances and under four inlet pressures. It was found that the geometry of impinging surface significantly affects the pressure oscillation peak and amplitude of self-resonating pulsed waterjet, and the influences largely depend on the inlet pressure. Both the pressure oscillation peak and the amplitude increase to their maximum and then drop with increasing standoff distance, which is regardless of the geometry of impinging surface. But the geometry influences the values of the optimum standoff distance and the oscillation peak and amplitude. Compared with the trend of pressure oscillation peak against standoff distance, the oscillation amplitude can be more obviously changed by the impinging surface. Moreover, an assumption that the geometry affects the pressure oscillation peak by the rebound waterjets and hydroacoustic waves has been proposed based on related literature. Further study should be conducted to clarify the relations between the axial pressure oscillation and the geometry of impinging surface.

The Effects of the Downstream Contraction Ratio of Organ-Pipe Nozzle on the Pressure Oscillations of Self-Resonating Waterjets

“…Moreover, it should be noticed that this development trend of the pressure oscillation peak and amplitude is a typical feature of SRWJs that had been demonstrated by Johnson et al [15], Chahine et al [17], and Li et al [19]. In addition, the results of our previous research have also confirmed this typical feature of SRWJ [29][30][31]35]. So, that is to say, at an inlet pressure of 10 MPa, only organ-pipe nozzles with a downstream contraction ratio of 2.5 can generate effective SRWJ that has large pressure oscillations.…”

“…A schematic diagram of the experimental setup for measuring the axial pressures of SRWJs under different values of the downstream contraction ratio is shown in Figure 2. It should be noticed that the experimental method and the main equipment and facilities shown in the figure were all the same with those used in our previous investigations [25][26][27][28][29][30][31][32], except for the organ-pipe nozzles. Therefore, the schematic of the experimental set-up is the same as the previous ones [31,35].…”

“…Ding et al [25] took advantage of SRWJs to improve the mechanical properties of the aluminum alloy and claimed that the hardness and residual stress could be increased by 61.69% and 148%, respectively. In addition, the authors have already conducted a series of experiments on SRWJs, such as the effects of the nozzle inner surface roughness, feeding pipe diameter, and the area discontinuity at the nozzle inlet on the characteristics of pressure oscillations and cavitation erosion of the jet [26][27][28][29][30][31][32][33][34][35].…”

“…Despite a great many investigations on SRWJ, it should be noticed that the optimal values of the downstream contraction ratio of organ-pipe nozzles are still unknown and need to be studied. So far, the organ-pipe nozzles used in the research are all manufactured using an equation that only gives the ratio of the chamber length to the exit diameter [13][14][15][16][17][18][19][20][21][22][25][26][27][28][29][30][31][32], and the detailed physical parameters required for fabricating an effective nozzle have not been reported.…”

Effects of Nozzle Exit Angle on the Pressure Characteristics of SRWJs Used for Deep-Hole Drilling

“…Most recently, we studied the preferred Strouhal number used in SRWJs, and found that the optimum values are 0.315 and 0.278 respectively, corresponding to inlet pressures of 10 MPa and 20 MPa [20]. Furthermore, a series of experimental investigations on SRWJs have also been conducted, ranging from the effects of nozzle inner surface roughness to the influence of feeding pipe diameter [21][22][23][24][25][26][27][28][29]. These investigations on the mechanisms and principles of SRWJs have contributed to the understanding of the jet and improvement of the jet's performance.…”