Numerical Research on Multi-Particle Movements and Nozzle Wear Involved in Abrasive Waterjet Machining

Multi-particle velocities and trajectories in abrasive waterjet machining are of great value to understand the particle erosion mechanism involved in the cutting process. In this paper, the whole-stage simulation model is established from the high-pressure water and abrasive particles entering the nozzle to the mixed abrasive jet impacting the workpiece based on the SPH-DEM-FEM method. Comparing the simulation results with the experimental results under different process parameters, the capability of the proposed model is systematically validated. The model is applied to study the mixing and accelerating process of abrasive particles, and the results show that a speed difference is existed between the water and abrasive particles after being ejected from the nozzle. In addition, the nozzle wear pattern is also analyzed carefully. It is discovered that the most serious wear happened at the junction of the mixing chamber and the focusing tube. And the focusing tube wear is uneven and spreads downward.

Wear analysis of abrasive waterjet nozzle using suprathreshold stochastic resonance technique

The performance of an abrasive water jet machining (AWJM) process is mainly dependent on the jet diameter, which is prone to change with time due to the nozzle wear. The present study is aimed to monitor the nozzle wear during operation using vibrational spectrum. Experiments are conducted with four focusing nozzles of different diameters under same parameters considering water and water-abrasive mixture as the jet. The obtained vibration spectrum through an accelerometer and data acquisition system are analyzed by Suprathreshold Stochastic Resonance (SSR) technique using MATLAB. The results obtained shows that SSR technique is easy to implement and gives a better performance in monitoring and analyzing the wear severity.

Investigating Plasma-Nozzle Wear Based on Processing Time and Current Ampere

Plasma cutting machine widely uses in electrical conductivity industrial according to an accuracy dimension and minimum time consuming. A cutting surface and kerf are keys process parameter to establish process quality by controlling diameter of nozzle and size of electrode. Since kerf shape is crated base on nozzle diameter, while electrode is served plasma arc. This paper presents an investigating nozzle wear based on current ampere and processing time. The controlled variables are a plasma-cutting machine, Hypertherm powermax 45 xp, Bindee control CNC machine and cutting path as whorl specimen of low carbon steel. The current Ampere was handled at 35, 40, 45 A. The processing time was controlled at 1, 2, 3, 4, 5 minutes. The diameters of nozzle were measured using digital microscope. The experiments conducted based on ANOVA to establish the relationship of those parameters. The nozzle wear depended upon the current Ampere and processing time in which a regression equation was presented as a result.

GAS-PUFF TARGET FOR LASER-PRODUCING PLASMA SXR SOURCE

Mass density spatial distributions of selected gas-puff targets have been determined by radiography, using quasi-monochromatic radiation at a wavelength of 13 nm. Results of spatial distributions of mass densities at various initial reservoir pressures for Nitrogen, Argon and Krypton targets are presented. Changes in the mass density spatial distribution due to a nozzle wear are reported.

Experimental investigation into simulated aging effects of common-rail injector nozzles: Influences on injection rate, spray characteristics, and engine performance

Emission performance of combustion engines has gained outstanding importance with both legislators and customers over the past years. Injector aging, such as nozzle wear or coking, results in the deterioration of injection and emission parameters. In this study, the influences of aging effects on injection rate, fuel spray as well as engine performance and emissions were assessed. Nozzles, which had previously been operated in a vehicle engine and were likely to have suffered from aging, showed no aging-induced characteristics during injection rate and spray measurements and were not investigated further. Therefore, nozzles with different nozzle hole diameters were utilized to simulate the different aging effects. Injection rate measurements demonstrated, that for smaller energizing times, a nozzle with smaller nozzle holes can deliver a higher injected mass than a nozzle with bigger nozzle holes. The adaptation of energizing time or injection pressure demonstrated the potential to compensate the change in engine load due to smaller or bigger nozzle holes. For bigger nozzle holes, the adaptation of injection pressure in order to restore the target load returned lower NOx emissions, whereas the adaptation of the energizing time always yielded lower soot emissions compared to the reference nozzle. For small nozzle holes, the optimization of the start of energizing reduced specific NOx emissions without increasing specific soot emissions. The comparison of measured injection rate and fuel spray characteristics to the ones reported in literature confirms the possibility of simulating nozzle wear by increased nozzle holes and coking by smaller nozzle holes. The results of this study are of vital interest to the research of aging effects and add useful knowledge about compensation methods for nozzle aging.

Nozzle Wear and Pressure Rise in Heating Volume of Self-blast Type Ultra-high Pressure Nitrogen Arc

This paper reports on experiments with ultra-high pressure nitrogen arcs in a self-blast type switch design. The effect of filling pressure on nozzle mass loss and pressure-rise in the heating volume were investigated. An arc current peak of 130 A at 190 Hz and a fixed inter-electrode gap of 50 mm were used throughout the experiment. The arc burns inside a polytetrafluoroethylene nozzle with a gas outflow vent in the middle. Nitrogen filling pressure of 1 bar, 20 bar, and 40 bar was tested, which also covers the supercritical region. Moreover, to study the effect of vent size on blow pressure near current zero, three different vent dimensions were investigated. <span> By increasing the filling pressure, the energy deposited in the arc increases as a result of increased arcing voltage</span>. It was observed that the pressure-rise in the heating volume is linked to the filling pressure, while the vent size plays a crucial role in the blow pressure near current zero. The nozzle mass loss per unit energy deposited in the arc is found to be independent of the filling pressure.