Water Jet Generation Research Articles

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.

Theoretical and practical research on micro hydrodynamic nozzles for modulated water jet generation as an innovation to replace continuous water jet in soft materials erosion

This study investigated the functionality of a newly developed micro hydrodynamic nozzle and its ability to generate a modulated water jet (MWJ) used for the erosion of soft materials. The procedure of nozzle design, numerical flow modelling, quality testing and functionality of the nozzle are presented. Well defined modulated jets were observed up to 1.5 MPa of input water pressure with an oscillation frequency of 88 kHz. Erosion characteristics of the modulated jets were investigated on soft gelatine samples. Three basic jet orientations were tested with respect to the eroded samples and to the trajectory of the nozzle movement. The erosion process of the MWJ was monitored using high-speed shadowgraph techniques. Then, the erosion depth was determined by image analysis methods. The test results show that the best erosion effect was obtained using the nozzle with 45° orientation with respect to the traverse direction.

Formation Principle and Characteristics of Self-Supercharging Pulsed Water Jet

High-pressure pulsed water jet technology has considerable development potential in the field of rock fragmentation. To overcome the shortcomings of existing pulsed jets, a self-supercharging pulsed water jet (SSPWJ) generation method is proposed, which is based on the theory of the pulsed water jet and the principle of hydraulic boosting. The proposed method changes the flow direction of the fluid medium through the valve core to make the piston reciprocate in the cylinder and relies on the effective area difference between the front and rear chambers in the stroke stage of the piston to realize the organic combination of “pulse” and “supercharging” of the jet, thus forming an SSPWJ. On the basis of the formation principle of the SSPWJ, a SSPWJ testing platform was constructed, and tests were performed on the jet pressure acquisition, morphology capture, and granite erosion. Both the jet pressure and the jet morphology exhibited periodic changes, and a higher pulse pressure was obtained at lower inlet pressure. The error of the pressure ratio calculated according to the experimental results was <3% relative to the theoretical design value, confirming the feasibility of the method. The pulse pressure and pulse frequency are controllable; that is, as the inlet flow rate increases in the stroke stage of the piston, the pulse pressure and pulse frequency increase, and the pulse duration decreases. As the inlet flow rate increases in the backward-stroke stage of the piston, the pulse frequency increases, and the pulse pressure and pulse duration remain unchanged. Under the combined action of the water-hammer pressure, high-speed lateral flow, and high-frequency dynamic load of the SSPWJ, local flaky exfoliation was observed when the granite surface was eroded. The results of this study lay the foundation for enriching the theory of pulsed jet generation and expanding its application range.

An experimental measurement research on impact load of high speed water jet acting on a rigid target by a Hopkinson pressure bar

A high speed water jet generation device based on explosion in a cylindrical cavity is introduced, which can eject a well-characterized water jet with a velocity around 100 m/s. The evolution characteristics and impact phenomenon of water jet act on a rigid target are observed by a high speed camera and the impact load is measured by a Hopkinson pressure bar. The top shape of water jet develops from a convex spherical surface to a flat plane as the stand-off increases under the influence of air resistance. When the top of water jet contacts the target plate, a transient high-pressure zone appears at the liquid-solid interface. A horizontal annular splashing jet generates and the velocity of splashing jet is much higher than that of incident jet as the result of high-pressure zone. The impact load is measured by the Hopkinson pressure bar, including transient “water hummer” pressure and subsequent hydrodynamic load. The “water hummer” pressure of water jet with a flat top is twice that with a convex spherical top, while the subsequent hydrodynamic pressure is equivalent at a comparable transient impact velocity. The measurement results by a Hopkinson pressure bar are in good agreement with the theory formulas in terms of both “water hummer” pressure and hydrodynamic pressure. It is certified that the Hopkinson pressure bar has a credible measuring capacity for both transient and steady-state pressure. By controlling cavity depth, charge amount and stand-off distance, the different top shape and velocity of water jet can be obtained.

Study of methods for controlling direction and velocity of liquid jets formed during subcooled boiling

The mechanism of submerged jets generation during subcooled surface and volumetric water boiling is studied experimentally and numerically. The boiling take place near the tip of the optical fiber through which the laser radiation is supplied. It is shown that the interaction of a collapsing bubble with the end face of the optical fiber leads to the symmetry breaking of the bubble, following by the water jet generation. The jet velocity depends on the collapse rate as well as on the ratio of the maximum bubble radius reached during the inflation stage to the fiber radius and, therefore, on the laser radiation intensity. Other problem parameters affecting characteristics of the generated jets are the temperature of the surrounding liquid and the fiber radius. Experiments with two perpendicular optical fibers demonstrate vector summation of the velocities of the jets generated by each individual fiber. Presented results might contribute to the development of new operating medical technologies for laser surgical treatment of a wide range of common diseases.

Technical-economic evaluation of abrasive recycling in the suspension fine jet process chain

Abrasive waterjet generation methods such as the conventional injection jet method and the suspension jet method have a strong influence on properties and costs of the machined products, particularly ones made of difficult-to-machine materials, e.g., ceramics. Since recycling may reduce the needed amount of materials significantly, the same holds true for recycling processes and technologies within the process chains of abrasive waterjet methods. In this paper, a methodology for integrated technical-economic evaluation of processes is presented and applied to the process technology of abrasive recycling in the suspension fine jet process chain aiming to show the technology’s technical as well as economic potential. Research and development regarding such processes and technologies may contribute to gain competitive advantages for companies as they can differentiate from competitors by offering or processing materials with distinctive properties and/or lower prices causing customer’s benefit. Consequently, it is also of great importance for companies applying waterjet cutting methods to know whether and which recycling technologies are promising from both a technical and an economic point of view. Experiments show that a significant share of the input material (abrasive particles) can be reused after recycling. The monetary appraisal reveals that technical potential results in considerably lower costs compared to the suspension jet method without recycling.

Differential pulse polarography at a dropping carbon fluid electrode

Differential pulse polarography was performed with a dropping carbon fluid electrode (DCFE). For the periodic renewal of DCFE, a new type of drop knocker was devised. Unlike those which knock on a capillary for a dropping mercury electrode (DME), this device is based on water jet generation. The water jet given from a nozzle placed nearby a capillary for DCFE was able to blow off the carbon drop periodically. The influence of convection on current signals was only significant within 1 s after the removal of the carbon drop. The comparison of the results of differential pulse and DC polarography showed that differential pulse polarography was superior to DC polarography in terms of the limit of detection.

On the application of gas detonation-driven water jet for material surface treatment process

The recent advances in pulsed waterjet technology create new opportunities for developing green manufacturing process. New methods of generating pulsed water jets in a simple, controlled fashion are sought after to improve the efficiency of current techniques. This paper examines an unconventional concept for producing high-speed liquid jets, created by detonation phenomenon. The technique relies on harnessing the pressure gain from a detonative combustion to drive a piston that in turn propels a liquid jet at high speed. The proof-of-concept, together with recent pulsed detonation engine development, holds promising potential for detonation-driven pulsed water jet generation applied to manufacturing process.

Numerical simulation and experimental research on water jet forming of copper foil

In order to solve the problems of die and tooling manufacturing and assembling for the foil forming, especially for the foil micro forming, high-pressure water jet forming (HPWJF), a new die-less forming process for foil parts is proposed. In the forming process, liquid medium such as water and oil is utilized as a flexible tool to deform the ultrathin foil. In this paper, the computational fluid dynamics (CFD) software Fluent was used to simulate the water jet generation in the water jet nozzle and high-speed water impacting on a rigid surface. And then, the effects of jetting distance on the jetting pressure were obtained. To measure the precise mechanical parameters of copper foils, a digital speckle test method was used to detect the tensile process. Local bulging experiment was conducted for the copper foil with a thickness of 50 μm. When the inlet pressure is 8.5 MPa, the suitable jetting distance is 40 mm for the 50-μm-thick copper foil. In such conditions, the bulging height of the copper foil is 1.20 mm in the experiment. The fluid–solid coupled method by using Fluent and Abaqus was applied to simulate the deformation of the copper foil. The errors between the simulated results and the experimental values are lower than 10 %. Furthermore, both the experiment and simulation for micro stretching of 30-μm-thick copper foil were performed. The cylinder die with a diameter of 3 mm and a height of 1.5 mm is used to form the copper foil. Results show that the copper foil cracks when the jetting distance is 24 mm, and the inlet pressure is 12 MPa. With the increase of the inlet pressure, the drawing depth of the copper foil gradually increases, and the bottom of the cylinder part thins gradually, and the wrinkling of the flange of the cylinder part becomes more and more severe.

Analysis on oscillating actuator frequency influence of the fluid flow characterization for 2D contractile water jet thruster

Contractile body is an alternative mechanism instead of rotating blade propeller to generate water jet for locomotion. The oscillating motion of the actuator at different frequencies varies the pressure and volume of the pressure chamber in time to draw in and jet out the water at a certain mass flow rate. The aim of this research was to analyze the influence of the actuating frequency of the fluid flow in the pressure chamber of the thruster during this inflation-deflation process. A 70mm × 70mm × 18mm (L × W × T) 2D water jet thruster was fabricated for this purpose. The contractile function was driven using two lateral pneumatic actuators where the fluid flow analysis was focused on the X-Y plane vector. Observation was carried out using a video camera and Matlab image measurement technique to determine the volume of the flowing mass. The result demonstrated that the greater actuating frequency decreases the fluid flow rate and the Reynolds number. This observation shows that the higher frequency would give a higher mass flow rate during water jet generation.

Comminution of material particles by water jets — Influence of the inner shape of the mixing chamber

Material comminution is one of the typical processes present during the injection abrasive water jet generation inside the mixing chamber and the focussing tube of the abrasive water jet cutting head. The determination of an extent of changes in the size of particles induced in the cutting head is the main objective of this contribution. Knowledge of the particle size at the exit from the cutting head is necessary for studying of the subsequent processes, e.g. the impingement of water jet with industrial mineral particles on a solid-state target or collision of such water jet with liquid barrier or opposite flowing jet of the same type.