Jet Process Research Articles

Effects of Process Parameters on the Microstructure and Mechanical Properties of Large PE Pipe via Polymer Melt Jetting Stacking

The conventional methods for producing large-diameter pipes, such as extrusion and winding fusion welding, suffer from various drawbacks including difficulties in forming, complex molds, and high costs. Moreover, the flexibility and production efficiency of traditional manufacturing processes are relatively low. To address these challenges, this study proposes a new manufacturing process for polymer melt jetting and stacking based on fused deposition modeling (FDM) and rolling forming principles. This innovative approach aims to overcome the limitations of conventional methods and improve the flexibility and production efficiency in large-diameter pipe manufacturing. In the polymer melt jetting and stacking process, a plastic melt with a specific temperature and pressure is extruded by an extruder. The melt is then injected through the nozzle embedded in the previous layer of the pipe blank. By utilizing the localized rolling action of the forming device and adjusting the diameter using a diameter adjustment device, the newly injected plastic melt bonds with the previous layer of the pipe blank. Finally, the continuous large-diameter plastic pipe is formed through cooling and solidification. Experimental investigations demonstrate that the polymer melt jetting and stacking process can produce pipes with diameters ranging from 780 mm to 850 mm and thicknesses of 20 mm to 25 mm. The radial tensile strength, impact strength, and microstructural orientation of the produced pipes exhibit superior performance compared to those in the axial direction. Additionally, process parameters such as rolling speed, cooling temperature, melt extrusion speed, and tractive velocity significantly influence the microstructure and mechanical properties of the pipes.

Characteristic diagnosis of supersonic gas jet target for laser wakefield acceleration with high spatial-temporal resolution Nomarski interference system

Gas targets hold distinctive significance and advantages in the field of laser-matter interaction. As a major type of gas targets, supersonic gas target is one of the most commonly used targets for laser wakefield acceleration (LWFA). The temporal-spatial resolution study of it could provide valuable data references for the LWFA experiment. In this work, a Nomarski interference system with high spatial-temporal resolution was set up to diagnose the jet process of supersonic gas jet target. The formation process of supersonic gas jet under different jet durations, different injection positions and different gas back pressures was studied. It is beneficial to determine the more optimized time and position of laser injection into target when conducting LWFA experiments. Therefore, the quality of the obtained electron beam and radiation source can be effectively improved.

Research Progress in Abrasive Water Jet Processing Technology.

Abrasive water jet machining technology is an unconventional special process technology; its jet stream has high energy, and its machining process is characterized by no thermal deformation, no pollution, high applicability, and high flexibility. It has been widely used for processing different types of materials in different fields. This review elaborates on the basic principles and characteristics of abrasive water jet processing, the mechanism of erosion, the simulation of the processing, the influence of process parameters in machining removal, and the optimization of improvements, as well as introduces the current application status, new technology, and future development direction of abrasive water jet technology. This review can provide an important information reference for researchers studying the machining processing of abrasive water jet technology.

Simulation analysis and evaluation of decontamination effect of different abrasive jet process parameters on radioactively contaminated metal

A new method of numerical simulating prediction and decontamination effect evaluation for abrasive jet decontamination to radioactively contaminated metal is proposed. Based on the Computational Fluid Dynamics and Discrete Element Model (CFD-DEM) coupled simulation model, the motion patterns and distribution of abrasives can be predicted, and the decontamination effect can be evaluated by image processing and recognition technology. The impact of three key parameters (impact distance, inlet pressure, abrasive mass flow rate) on the decontamination effect is revealed. Moreover, here are experiments of reliability verification to decontamination effect and numerical simulation methods that has been conducted. The results show that: 60Co and other homogeneous solid solution radioactive pollutants can be removed by abrasive jet, and the average removal rate of Co exceeds 80%. It is reliable for the proposed numerical simulation and evaluation method because of the well goodness of fit between predicted value and actual values: The predicted values and actual values of the abrasive distribution diameter are Ф57 and Ф55; the total coverage rate is 26.42% and 23.50%; the average impact velocity is 81.73 m/s and 78.00 m/s. Further analysis shows that the impact distance has a significant impact on the distribution of abrasive particles on the target surface, the coverage rate of the core area increases at first, and then decreases with the increase of the impact distance of the nozzle, which reach a maximum of 14.44% at 300 mm. It is recommended to set the impact distance around 300 mm, because at this time the core area coverage of the abrasive is the largest and the impact velocity is stable at the highest speed of 81.94 m/s. The impact of the nozzle inlet pressure on the decontamination effect mainly affects the impact kinetic energy of the abrasive and has little impact on the distribution. The greater the inlet pressure, the greater the impact kinetic energy, and the stronger the decontamination ability of the abrasive. But in return, the energy consumption is higher, too. For the decontamination of radioactively contaminated metals, it is recommended to set the inlet pressure of the nozzle at around 0.6 MPa. Because most of the Co elements can be removed under this pressure. Increasing the mass and flow of abrasives appropriately can enhance the decontamination effectiveness. The total mass of abrasives per unit decontamination area is suggested to be 50 g because the core area coverage rate of the abrasive is relatively large under this condition; and the nozzle wear extent is acceptable.

Design guidelines for metal binder jetting

In addition to the general advantages of additive manufacturing technologies, such as the resource-efficient production of highly complex components, the metal binder jetting (MBJ) process enables a more cost-effective manufacturing of metal additive components. However, the design freedoms gained by additive manufacturing, and MBJ in particular, are also accompanied by new design restrictions for component design. While a large number of design guidelines are already available for the established additive manufacturing processes, the metal binder jetting process imposes additional requirements on component design, which are currently only inadequately covered in the literature. Therefore, this paper presents the development and derivation of first design rules for the metal binder jetting process using martensitic stainless steel (17–4 PH). In this way, the paper also provides a methodology for deriving guidelines regardless of the material. In total, 13 guidelines have emerged from this, which in part both confirm existing guidelines, but also extend them.

A 3D simulation model of thermal runaway in Li-ion batteries coupled particles ejection and jet flow

A coupled simulation model of the 18650 lithium-ion batteries (LIB) thermal runaway (TR) is presented in this study, which includes TR decomposition reaction, gas generation and combustion processes, solid particles ejection and particles heat transfer process. The model considers a combination of solid heat conduction, gas convection, flame and particles radiation, which is validated to accurately capture the temperature evolution and two typical jet processes during TR. Model validation conducts with experimental measurements for the temperature of the battery surface. The simulation results show that the “ignition” time of the flammable gas mixture is delayed and the rate of flame temperature increase is slowed down when the effect of solid particles is considered. The radiation heat transfer rate and convection heat transfer rate on the adjacent battery surfaces are 80.3W and 12.76W, and are approximately 4.29 times and 1.76 times larger than the results calculated by the model without solid particles, respectively. The difference between these two can be further magnified in confined space. The model developed in this study combines the effect of the solid particles’ radiation into the TR simulation innovatively. It can provide a more accurate calculation method for the prediction of TR propagation.

Role of Altitude in Influencing the Spray Combustion Characteristics of a Heavy-Duty Diesel Engine in a Constant Volume Combustion Chamber. Part I: Free Diesel Jet

Heavy-duty diesel engines operating in plateau regions experience deteriorated combustion. However, the lack of up-to-date information on the spray-combustion process limits the fundamental understanding of the role of altitude. In this work, the in-cylinder thermodynamic conditions of a real diesel engine operating under different altitudes were reproduced in a constant-volume combustion chamber (CVCC). The liquid spray, ignition, and combustion processes were visualized in detail using different optical diagnostics. Apart from predictable results, some interesting new findings were obtained to improve the understanding of free spray-combustion processes with different altitudes. The spatial distributions of ignition kernels provided direct evidence of higher peak pressure rise rates for high-altitude diesel engines. The percent of stoichiometric air was calculated to confirm that the net effect of altitude was an increase in the amount of air-entrained upstream of the lifted flame; therefore, the soot levels deduced from flame images were inconsistent with those from real engines, revealing that accelerating the soot oxidation process could effectively reduce engine soot emissions in plateau regions. Finally, a novel schematic diagram of the spray flame structure was proposed to phenomenologically describe the role of altitude in influencing the spray-combustion process of a free jet.

Study on water jet penetration behavior in molten LBE during SGTR accident with simulant experiments

During Steam Generator Tube Rupture (SGTR) accidents of Lead-bismuth cooled Fast Reactor (LFR), the coolant water in the secondary loop will directly contact with the high temperature molten lead–bismuth eutectic (LBE) in the primary loop around the rupture point resulting in the strong interaction, which may lead to vapor explosion, and eventually damage the structural components of the reactors and cause the possible leakage of radioactive material. In order to further investigate the penetration behavior of water jets in molten LBE, an experimental platform for visualizing the two-phase flow of liquid jets is designed and built, and a series of simulant experiments are conducted by injecting water or ethanol jets into fluorinert FC-40 under different experimental conditions. By analyzing the penetration process of ethanol jet in FC-40, the flow pattern evolution and penetration law of ethanol jet under boiling and non-boiling conditions are obtained. The boiling effect is considered to be the key factor affecting the penetration depth of jet in the range of current experimental conditions. By comparing the injection behaviors of ethanol and water, the consistent flow pattern shows that the injection behavior can be described with the same relation. The results of dimensional analysis method for jet penetration process show that the Froude number theory can reasonably predict the maximum dimensionless penetration depth under different jet conditions.

The overpressure and temperature characteristics of hydrogen-air mixtures during a vented explosion in a large L/D ratio duct: Effect of burst pressure

Explosion venting is an effective way to reduce the hazards of gases and dust fuel explosion in a confined space. Since there is little attention paid to the thermal radiant damage produced by the vented flame, the surface temperature distribution for hydrogen-air mixtures with different burst pressures (Pv) is investigated in a large L/D ratio duct. The high-speed shadowgraph imaging system, pressure testing system and infrared thermal imager are used to record the explosion venting process. The Pv and the thickness (δ) of the polyester vent cover are in the direct ratio, while the vent failure time shows a nonlinear relationship with the δ. Five internal overpressure peaks (P1, P2, P3, PRef, Pneg) are distinguished. With the addition of Pv, P1 increases gradually, while P2 disappears in some higher Pv. The external flow field is obtained and discussed in detail. The cases of lower Pv with the unburned gas escaping from the vessel can sustain a high flame speed, whereas other cases only involve a flame jetting process with a relatively low speed. The high-temperature (>500 ℃) duration shows an ‘M’ shape with the Pv. Besides, the safety distances to prevent humans from suffering thermal radiant damage have been determined.

Experimental and numerical analysis of the liquid metal mixing phenomenon in complex jets of Gen-IV nuclear system

Nuclear energy is essential in addressing the problem of climate change and energy crisis. Liquid metal mixing phenomenon at the core outlet of liquid metal fast reactors is an important issue in Gen-IV nuclear systems. In this paper, the experimental and numerical analysis of the liquid metal mixing process in complex jets were carried out based on the structure of fuel assembly heads in sodium-cooled fast reactors. The liquid metal mixing characteristics were obtained in the experiment. And a high fidelity LES model was developed and validated experimentally. The impact of different head structures on the mixing process was analyzed and an index of liquid metal temperature mixing degree was newly proposed and compared with previous formulas. Result shows that, the temperature mixing region can be divided into five zones along the flow direction. Compared to other three structures, the three-sided outlet head with offset hedge has the lowest fluctuations of velocity and temperature in the upstream of the mixing flow. Also, the three-sided outlet head with offset hedge has the best temperature mixing ability, and the index is two times larger than that of the prototype. The three-sided outlet head with offset hedge proved to be the optimal structure.

Modeling of the curing kinetics of acrylate photopolymers for additive manufacturing

AbstractNext‐generation additive manufacturing (AM) processes such as multiphoton lithography and the fusion jetting (FJ) process demonstrate increasing demands toward temperature stability and a thoroughly understood curing behavior of acrylate photopolymers. This investigation targets the utilization of different kinetic models based on experimentally determined calorimetric results of different acrylate systems. The goal is to determine a holistic model that successfully describes the simultaneous dependency of the curing behavior on the temperature and the UV intensity. Two consecutive modeling strategies are investigated: a single measurement analysis followed by a clustered measurement analysis. In both cases, models based on the Kamal–Sourour method provide superior coefficients of determination above 0.99. First conclusions were drawn toward selected kinetic parameters, such as the temperature independence of the respective reaction orders. The model was then successfully utilized for first predictions of the curing behavior, demonstrating plausible progressions of the degree of cure for not experimentally determined UV intensities.

Measurements of the Cross-Section for the \({{\rm t}{\bar{\rm t}}}\) Heavy-Flavor Production at the LHC

At the LHC, the process of a Higgs boson decaying into bottom or charm quarks produced in association with a pair of top quarks, tt¯H, allows for an empirical exploration of the heavy-flavor quark Yukawa couplings to the Higgs boson. Accordingly, the cross-sections for the tt¯ + heavy-flavor production without the appearance of the Higgs boson have been measured at the LHC in various phase spaces using data samples collected in pp collisions at s = 7, 8 and 13 TeV with the ATLAS and CMS experiments. Flavor ratios of cross-sections of tt¯ + heavy-flavors to tt¯ + additional jets processes are also measured. In this paper, the measured cross-sections and ratios are reviewed and the prospects with more data are presented.

Numerical simulation of trans-/near-/supercritical injection characteristics based on real fluid properties

In this paper, the trans-/near-/supercritical jet models were established using a combination of large eddy numerical simulations and real fluid equations of state (EOS) in order to systematically investigate the heat and mass transfer mixing process of the jet at supercritical pressure. The effects of EOS, injection temperature (Tinj), ambient pressure (Pamb), and the pseudo-boiling phenomena on the density field, temperature increase rate, spray penetration, spray area, spreading angle, and mixing layer thickness of the spray were investigated. The results reveal that the initial shape of the spray is connected to its thermodynamic and transport characteristics. The correctness of fuel characteristic parameters impacts the development of the jet. For trans-/near-critical sprays, the temperature rise rate, spreading angle, spray area, and mixing layer thickness are enhanced, indicating the mixing efficiency is improved by increasing the Pamb and Tinj. However, raising the Pamb has a detrimental impact if both the Tinj and the Pamb exceed the critical parameters. This is owing to the link between Tinj and pseudo-boiling temperature, which results in a trade-off between Pamb and the objects discussed above for supercritical sprays. This research is essential to comprehend the heat and mass transfer mixing process of the supercritical jet.

Study on the process of abrasive water jet cutting for zirconia ceramic tubes

Study on the process of abrasive water jet cutting for zirconia ceramic tubes

Atomization of liquid pulsed jet in subsonic crossflow

Pulsed jet is an effective solution to improve fuel jet penetration depth and consequently increase the mixing efficiency of gas–liquid in conventional combustion chambers. This has the benefits of reducing pollutant emissions and diminishing the instability of fuel combustion. However, the atomization process of pulsed jets with small amplitude has still not been properly investigated. This paper studies such a process through Large Eddy Simulation and a Coupled Level Set and Volume of Fluid method. We investigate the atomization process in a liquid pulsed jet with a subsonic crossflow and the impact of the Strouhal number on atomization morphology and the behavior of the pulsed jet in general. Results show that, with a constant mass flow rate, the role of Rayleigh–Taylor instability is replaced by the periodic fluctuation of the jet velocity, which ends up dominating the primary process of atomization of the liquid transverse pulsed jet. This also improves atomization, in general, and the fragmentation of the jet. We also show that the Strouhal number significantly impacts the penetration depth of the jet, with high values increasing penetration by up to 12%.

Physics-Informed Bayesian learning of electrohydrodynamic polymer jet printing dynamics

Calibration of highly dynamic multi-physics manufacturing processes such as electrohydrodynamics-based additive manufacturing (AM) technologies (E-jet printing) is still performed by labor-intensive trial-and-error practices. Such practices have hindered the broad adoption of these technologies, demanding a new paradigm of self-calibrating E-jet printing machines. Here we develop an end-to-end physics-informed Bayesian learning framework (GPJet) which can learn the jet process dynamics with minimum experimental cost. GPJet consists of three modules: the machine vision module, the physics-based modeling module, and the machine learning (ML) module. GPJet was tested on a virtual E-jet printing machine with in-process jet monitoring capabilities. Our results show that the Machine Vision module can extract high-fidelity jet features in real-time from video data using an automated parallelized computer vision workflow. The Machine Vision module, combined with the Physics-based modeling module, can also act as closed-loop sensory feedback to the Machine Learning module of high- and low-fidelity data. This work extends the application of intelligent AM machines to more complex working conditions while reducing cost and increasing computational efficiency.

Numerical study on the mixing and combustion characteristics of a liquid kerosene jet in a scramjet combustor

We numerically investigate the mixing and combustion process of a kerosene jet injected into a scramjet combustor with dual-cavity at different global fuel equivalence ratios using a compressible two-phase flow large-eddy simulation based on the Eulerian–Lagrangian approach. The results indicate that the calculated wall pressure distribution is basically consistent with the experimental result. The high-temperature zone and intermediate product CO distribution zone shown by the numerical simulation agree with the flame position observed by the experiment. When the global equivalent ratio is 0.149, the combustion is in the weak combustion mode. The flame only exists in the downstream cavity, which is mostly the premixed flame. The combustion efficiency is low, and the corresponding total pressure loss is small. When the global equivalent ratio is 0.187, the combustion is in the intense combustion mode, and the flame has a strong instability characteristic. The numerical simulation reproduces the flame flashback phenomenon that the flame backpropagation from the downstream region of cavity C1 to the upstream region of the liquid jet. During the flame flashback process, the flame gradually changes from premixed flame dominated to premixed flame and diffusion flame jointly dominated. In the weak combustion mode, the interaction between flame and droplet is weak, and droplet evaporation is less affected by combustion. While in the intense combustion mode, droplets evaporate more violently, the spray penetration depth increases, and some liquid droplets are transported upstream of the jet by the wall reflux zone.

Multi-scalar mixing in turbulent coaxial jets

Although natural and industrial flows often transport and mix multiple scalars, relatively few studies of turbulent multi-scalar mixing have been undertaken. In the present work, a novel three-wire thermal-anemometry-based probe – capable of simultaneously measuring velocity, helium concentration and temperature – is used to investigate the evolution of multiple scalars ($\phi _1$,$\phi _2$,$\phi _3$) and velocity in turbulent coaxial jets. The jets consist of (i) a centre jet containing a mixture of helium and air ($\phi _1$), (ii) an annular jet containing pure (unheated) air ($\phi _2$) and (iii) a coflow of (pure) heated air ($\phi _3$). Axial measurements are made at three different momentum flux ratios ($M=0.77, 2.1, 4.2$). Increasing$M$was observed to result in complex, competing effects. Larger momentum flux ratios cause the potential core of the centre jet to decrease in size, greater scalar fluctuations and more rapid correlation of$\phi _1$and$\phi _2$. However, at the same time, certain statistics, including those describing the velocity field, evolve more slowly. Moreover, the flow near the beginning of the fully merged region appears to be less mixed at higher values of$M$. The present work finally demonstrates that differences can be observed in the evolution and mixing of coaxial jets between those in which$M<1$and those in which$M>1$, thereby presenting an opportunity by which the mixing process in coaxial jets may be controlled.

Mechanical properties and microstructural characteristics of 316L stainless steel fabricated by laser powder bed fusion and binder jetting

In this work, the tensile test coupons and lattice structure of 316L stainless steel (SS) samples were manufactured by two powder bed-based additive manufacturing (AM) techniques-laser powder bed fusion (LPBF) and binder jetting (BJ) processes. The microstructure and mechanical properties of these components were investigated through a scanning electron microscope, hardness measurement, tensile tests, and compression tests. The results showed that the grain size of the LPBF sample was smaller than that of the BJ sample. This difference led to the microhardness of LPBF and BJ samples being 239.16 ± 4.90 HV and 208.71 ± 4.15 HV, respectively. The relative density of LPBF samples was 99.20 ± 0.30% and the BJ samples was 96.54 ± 0.54%. The LPBF samples had better mechanical properties, with tensile strength and compressive yield strength of 669.92 ± 18.68 MPa and 75.65 ± 5.77 MPa, respectively, while the tensile strength and compressive yield strength of the BJ samples were 437.55 ± 10.11 MPa and 78.65 ± 3.57 MPa, respectively. The experimental data showed good consistency with the simulation results (error within 10%) in both the compression modulus and yield strength for the lattice structures. These findings look promising for the future design of lattice structures with high mechanical properties using LPBF and BJ techniques.

Prediction and mechanism of surface evolution in high-pressure slurry jet micro-machining of channels

Recent advances in abrasive water jet (AWJ) processes have enabled controlled-depth micro milling for a variety of applications, such as micro fluidic chip manufacturing. However, AWJ micro milling can be difficult to control and its successful application requires judicious selection of the process parameters. Since the mechanics of the process have not been fully understood, prediction of the machined topography arising from a set of process parameters is difficult. The present work combines computational fluid dynamics, Lagrangian particle tracking, and a deformed geometry surface evolution technique into a comprehensive model that predicts the evolving shape of micro-channels milled on 6061-T6 aluminum plates using high-pressure abrasive slurry jet machining (HASJM). Requiring calibration using only a single channel centerline depth, the model could predict the machined profiles of micro-channels milled using multiple nozzle passes with less than a 2% error. The model was also used to investigate the underlying physics of the machining process. This allowed experimental observations to be explained in terms of the changes that occur, due to the evolving eroded shape, in stagnation zone size, particle ricochet behavior, secondary slurry flow, and local particle impact angles and velocities. Overall, the work shows that such models can not only very accurately predict evolving machined topography, but also be very useful tools to understand abrasive jet machining mechanisms which occur on time scales which are too brief to be directly observed experimentally.