Generation of effective pulsed waterjets by ultrasonic nozzle used for energy exploration

Pulsed waterjet has higher energy efficiency ratio and less energy consumption than a continuous waterjet. To achieve more effective and powerful pulsed waterjets, a new ultrasonic nozzle with more compact structure and less energy loss was developed. By designing a hollow flow channel in the piezoelectric ceramic stack and the amplifier, the nozzle enables axial water inlet and avoids energy loss at the turnaround point. The resonant frequency of the ultrasonic nozzle was validated as 19227 Hz by modal analysis and impedance test, which is a deviation of 3.87% compared with the expected frequency of 20000 Hz. Besides, the pulse characteristics of modulated waterjet were analyzed experimentally by high-speed photography. The pulsed waterjet presented obvious periodic pulses and good clustering, and water slugs of "mushroom" shape can be clearly observed. The difference between the waterjet velocity and the theoretical value is less than 7.7%. And the pulse frequency of the modulated waterjet reaches about 19485.1 Hz, with a deviation of 1.3% compared with the nozzle resonant frequency of 19227 Hz. The new ultrasonic nozzle can be widely used in energy exploration for effective pulsed waterjet generation and less energy consumption.