Jet Process Research Articles

Sintering of Si3N4–SiC–MoSi2 composites additively manufactured by Multi Material Jetting

AbstractThe aim of this work was to investigate the sintering behavior of Si3N4–SiC–MoSi2 composites manufactured by the Multi Material Jetting (MMJ) process. Therefore, electrically conductive and insulating Si3N4–SiC–MoSi2 composites were printed using MMJ. Samples were sintered in a gas‐pressure furnace at 6 and 31 atm, respectively. The density, microstructure, and crystalline phase composition were investigated, and the results discussed regarding the phase stability of the Si3N4–SiC–MoSi2 composites. The results show that the nitrogen pressure must be set carefully to avoid the formation of Mo5Si3 or Mo4.8Si3C0.6 on the one hand and to prevent the decomposition of the phases into a Si‐containing melt on the other.

Concurrent process and feedrate scheduling with convoluted basis functions and its application to fluid jet polishing

Non-traditional laser and fluid jet processes exhibit time-dependent material removal characteristics. The feedrate profile must be planned carefully along the toolpath for accurate surface profile generation while ensuring that the kinematic limits of machine tools are not violated. Conventional methods iteratively solve a deconvolution/convolution problem on the dwell-time density (reciprocal of the feedrate profile) that is computationally heavy, may leave significant residual processing errors, and even generate infeasible feed profiles with the manufacturing equipment. This paper proposes a novel approach that fully addresses the shortcomings above. Dwell-time density is first expressed as a continuous B-spline profile. The associated dwell basis functions (DBF) are convolved with the process influence function (PIF) to generate new process basis functions (PBF). This approach conveniently allows the posing of the problem as a concurrent linear least-squares problem on the control points shared by the DBFs and PBFs while ensuring the numerical stability of the solution and smoothness of the feed profile. To mitigate excessive acceleration peaks and any ringing effect around the edges of the toolpath, this paper also presents methodologies for stabilizing the scheduled feedrate profile by introducing knot vector adjustments (adaptive knot dropping) and linear edge constraints. The effectiveness of the proposed method is demonstrated and validated through simulation case studies and experimentally in fluid jet processing of precision optics. Results indicate that the proposed technique overcomes the limitations of conventional strategies and allows high-frequency surface components beyond the first zero-power frequency of the process footprint to be tracked while still generating a smooth feed profile within the acceleration limits of a machine tool. This ability stems from the localization characteristics associated with the basis functions. By improving the accuracy of high-frequency components, the proposed method exhibits the potential to fabricate topographies with sharper edges, which has been a challenge for conventional techniques.

Numerical simulation of spray atomization in crossflow using an empirical primary atomization model

The hybrid Eulerian-Lagrangian approach is used to simulate the atomization process of spray jet in subsonic crossflow. A coupled Volume of Fluid (VOF) - Lagrangian Particle Tracking (LPT) solver is implemented in the open-source platform OpenFOAM to solve the governing equations for the continuous and discrete phase respectively. An empirical model for primary atomization is proposed, in which the aerodynamic effect is taken into account, along with the turbulence effect. Thus, it is suitable for the flow at a low liquid-gas density ratio, i.e., less than 500. The performance of the presented model is evaluated and verified by comparisons of the simulated results with the experimental data. The flow characteristics of flow fields and distribution of droplet diameters are analyzed in detail. It is revealed that the vortex structures have a direct impact on the distribution of the droplets. The effects of the empirical constants in the atomization model are also examined. Finally, it is shown that the model performs better for the flow at a higher Weber number, in which the aerodynamic effect is more significant.

Study on water jet stability and processing morphology of groove cutting using water jet guided laser

In order to reveal the formation process of straight grooves using water jet guided laser (WJGL) technology and analyze the reasons for the formation of straight groove morphology, the stability of water jet in the straight groove were studied and the internal morphology of the straight groove obtained by WJGL processing was characterized. Firstly, the stability of water jet moving in straight grooves with different depths (0.5–50 mm), lengths (1–20 mm), widths (0–200 μm), inlet velocity (100–300 m/s), bottom shapes (flat, inclined), and types (through grooves, blind grooves) were studied through numerical simulation. Subsequently, the influence of water jet stability on the removal of material from the groove bottom was analyzed based on the guiding effect of water jet on laser. Then, different types of straight grooves (long blind groove, long through groove, short blind groove, short through groove) were processed using WJGL technology with different cutting cycles (2–10 times), and the internal morphology of the grooves was characterized through industrial computed tomography (CT). Finally, the reasons for the formation of the morphology inside the groove were analyzed based on simulation and experimental results. The results indicate that the fracture of the water jet in the blind groove includes when the water jet moves to the side wall, when the water jet reaches a stable length, and when the liquid is discharged from the narrow groove. The phenomenon of “inclined propagation” occurs when WJGL passes through the intersection of the flat and inclined bottom surfaces of the groove. The phenomenon of “inclined enhancement” occurs when WJGL is used to process the inclined bottom surface of the groove. This article reveals for the first time the flow morphology of micro water jet in straight grooves, and analyzes the reasons for the formation of groove morphology, which has guiding significance for the process optimization and practical application of WJGL technology in straight groove processing.

Numerical Simulation Study of Energy Separation in Jet Shear Layer

In order to investigate the rational utilization of energy in the fluid jet process, a free dual jet of parallel air is used as a research object. Simulation of turbulence was carried out based on the realizable k-epsilon equations with pressure-velocity coupling, PISO method, discrete method with second-order windward format, and first-order implicit transient solution. The energy separation phenomenon within the jet shear layer and its influencing factors were investigated under dual-jet Reynolds number differences of 12,800, 19,200, 25,600, 32,000, 41,500, and 51,100, respectively. The simulation is in transient format and the jet inlet velocity is given by udf. Calculations show that the pressure perturbation in the air shear layer, which gives rise to the pressure work exchange between the jet and the surroundings, is the main reason for the coexistence of high- and low-temperature regions formed within the jet shear layer, and the larger the Reynolds number, the stronger the energy separation effect. The center streamline path of a parallel air free dual jet can be fitted by a circular arc, whose radius of curvature increases with the Reynolds number, and the curvilinear development path of the dual jet can offset the energy separation effect to some extent. This paper confirms the existence of energy separation in the shear layer of a parallel air free double jet, reveals the mechanism of energy separation in the fluid domain, and explores the flow characteristics of two parallel jets.

Numerical simulation of water jet load induced by spherical bubble collapse under underwater explosion

In this study, a numerical method combining the HLLC solver and FV-WENO scheme is proposed to accurately simulate the behavior of multiphase compressible fluids and investigate the formation process of water jets. The HLLC solver approximates the conservation equations of the fluid by using numerical fluxes from the approximate Riemann problem, while the FV-WENO scheme improves the accuracy of the numerical solution by employing the weighted essentially non-oscillatory (WENO) reconstruction method. The combination of these methods allows for a more accurate simulation of the behavior of multiphase compressible fluids, leading to an accurate depiction of the formation process of water jets. By simulating the interaction between underwater shock waves from explosions and single or multiple spherical bubbles, we study the generation, development, and collapse of water jets during the bubble collapse process. By revealing the characteristics of the load during the formation of water jets and the interaction mechanisms between bubbles, our study provides support for further research on water jet phenomena. The formation process of water jets is of great significance for understanding the propagation of underwater shock waves and structural damage. Through this study, we delve into the mechanism of water jet formation, providing a new perspective on the propagation of underwater shock waves and structural damage. Our research results demonstrate that the application of the HLLC solver and FVWENO scheme in water jet simulation effectively improves the accuracy and precision of the numerical solution.

Calcium Bright Knots and the Formation of Chromospheric Anemone Jets on the Sun

Space-based observations show that the solar atmosphere from the solar chromosphere to the solar corona is filled with small-scale jets and is linked with small-scale explosions. These jets may be produced by mechanisms similar to those of large-scale flares and such jets may be related to the heating of the corona and chromosphere as well as the acceleration of solar wind. The chromospheric anemone jets on the Sun remain puzzling because their footpoints (or bright knots) have not been well resolved and the formation process of such enigmatic small-scale jets remains unclear. We propose a new model for chromospheric jets using the 3D magnetohydrodynamic simulations, which show that the continuous, upward rising of small-scale twisted magnetic flux ropes in a magnetized solar chromosphere drives small-scale magnetic reconnection and the launching of several small-scale jets during the evolution of the chromospheric anemone jets. Our new, self-consistent, 3D computer modeling of small-scale, but ever-changing flux rope emergence in the magnetized solar atmosphere is fully consistent with observations and provides a universal mechanism for nanoflare and jet formation.

Review of atomization characteristics of liquid jets in crossflow

The atomization process of liquid fuels is vital in scramjet engines. The level of atomization directly impacts the subsequent evaporation, mixing, and combustion processes. Therefore, understanding the atomization mechanism of liquid jets in crossflow is necessary to promote the mixing process of scramjet engines and improve the combustion efficiency. This article overviews the atomization process of liquid jets in transverse airflow based on the breakup mechanism, atomization characteristics, and factors affecting atomization. The deformation and fragmentation of droplets are influenced primarily by the Weber number and have little correlation with the Reynolds number. There are similarities in the properties between the primary fragmentation of liquid jets and the breakup of liquid droplets in crossflow. The primary breakup of liquid jets in crossflow is characterized primarily by continuous jet column breakup. The Rayleigh–Taylor instability causes columnar breakup, while the Kelvin–Helmholtz instability causes surface breakup in the jet. The size distribution of droplets follows C-, I-, or S-shaped distributions, while the velocity distribution of droplets follows an inverse C-shape. Finally, the shortcomings of current research are pointed out, namely, the lack of research on the jet breakup mechanism in crossflow under actual scramjet engine configurations and inflow conditions. In the future, it can be combined with artificial intelligence to reveal the jet breakup mechanism under actual working conditions and establish a wide range of theoretical prediction models.

Research on ionization characteristics of atmospheric pressure pulse-modulated microwave He/air plasma jet

The atmospheric pressure pulsed microwave He plasma jet has the advantages of high electron density and abundant active particles, but its shrinking on the discharge electrode morphology limits its application range. In order to modulate a He plasma jet with a longer plume and study its ionization development characteristics, we constructed a dual-channel pulsed microwave coaxial discharge device. He and air were, respectively, injected into the inner and outer gas channels of the resonator to generate a double-layer atmospheric pressure microwave plasma jet with a longer plume. It is observed that the bifurcation of the stratified plasma jet will occur by changing the gas flow. The ionization development of plasma jet was observed by using enhanced charge-coupled device and microwave Rayleigh scattering apparatus measured the space-time evolution of plasma and observed the three times ionization enhancement process of plasma jet development. The spectral lines of the active products associated with Penning ionization were observed by using a fiber optic spectrometer. A fluid model was constructed to simulate and analyze that under the condition of sufficient He flow rate (He flow rate is above 0.6 slm), there will be sufficient and stable He mole fraction (64%) at the stratification of the plasma jet. The experimental and simulation results show that the jet profile of the microwave He plasma is related to the inlet structure of the discharger and He flow rate. Stratified intake structure can produce stratified He plasma jet, and the unique appearance of bifurcation of jet can be produced by changing the flow rate of He. In the bifurcation process of the plasma jet, the product of Penning ionization inhibits the development of the main branch of the plasma jet, and the secondary electron avalanche of the local electric field promotes the formation of the branch of the plasma jet and is accompanied by the enhancement of the second ionization. The ionization mechanism of microwave He plasma is the resonance excitation of local enhanced electric field, the advance of ionizing waves, and the interaction between the spatially distributed active particles.

Flow Characteristics of Liquid Jet in Transverse Shear Crossflow

The numerical simulation method was used to investigate the deflection and deformation process of a circular lubricating oil jet in transverse shear airflow. The numerical model was compared and validated against the experimental data. The physical parameters of Mobil jet Oil II were utilized in this simulation with the nozzle diameter ranging from 0.5 to 2.5 mm, the maximum liquid/gas momentum ratios varying from 10.35 to 165.50, and the injection angle ranging from 0 to 30° in the opposite airflow direction. The results show that an increase in the nozzle diameter decreases the degree of jet deflection. The higher airflow velocity causes more fluctuations in the oil-jet trajectory, while the higher oil-injection velocity reduces fluctuations in the trajectory. The parabolic curve equations were used to derive the trajectory equations for the jet column’s pre-disintegration under both vertical incidence and a small angle of reverse airflow. The nozzle diameter and maximum oil/air momentum ratio were used to obtain a formula for the trajectory curve of the lubricating oil. Additionally, a formula for fitting the trajectory curve of oil injected in the opposite airflow direction regarding the injection angle was developed.

Factorization of non-global LHC observables and resummation of super-leading logarithms

We present a systematic formalism based on a factorization theorem in soft-collinear effective theory to describe non-global observables at hadron colliders, such as gap-between-jets cross sections. The cross sections are factorized into convolutions of hard functions, capturing the dependence on the partonic center-of-mass energy ŝ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\sqrt{\\hat{s}} $$\\end{document}, and low-energy matrix elements, which are sensitive to the low scale Q0 ≪ ŝ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\sqrt{\\hat{s}} $$\\end{document} characteristic of the veto imposed on energetic emissions into the gap between the jets. The scale evolution of both objects is governed by a renormalization-group equation, which we derive at one-loop order. By solving the evolution equation for the hard functions for arbitrary 2 → M jet processes in the leading logarithmic approximation, we accomplish for the first time the all-order resummation of the so-called “super-leading logarithms” discovered in 2006, thereby solving an old problem of quantum field theory. We study the numerical size of the corresponding effects for different partonic scattering processes and explain why they are sizable for pp → 2 jets processes, but suppressed in H/Z and H/Z + jet production. The super-leading logarithms are given by an alternating series, whose individual terms can be much larger than the resummed result, even in very high orders of the loop expansion. Resummation is therefore essential to control these effects. We find that the asymptotic fall-off of the resummed series is much weaker than for standard Sudakov form factors.

Comparative Evaluation of Working Accuracy in the Atomic Diffusion Additive Manufacturing (ADAM) Process and the Binder Jetting (BJ) Process by Analysing Key Characteristics

Comparative Evaluation of Working Accuracy in the Atomic Diffusion Additive Manufacturing (ADAM) Process and the Binder Jetting (BJ) Process by Analysing Key Characteristics

High energy processes in common envelope jets supernovae

AbstractWe study high energy processes that occur during the merger of a neutron star (NS) or a black hole (BH) with the core of a red supergaint (RSG). The merger powers a luminous event termed common envelope jets supernova (CEJSN), that might account for lightcurves of peculiar transients. In the CEJSN scenario the NS/BH accretes mass from its surroundings through an accretion disk as it spirals-in inside the RSG’s envelope and core. The compact object launches part of this mass as narrow jets that interact with their environment by depositing their kinetic energy in the envelope and core gas. These jets can serve as production sites of high energy neutrinos and r-process elements.

Numerical research on rock cutting by abrasive jet under confining pressure based on SPH-FEM method

On the basis of experimental verification, the methods of smooth particle hydrodynamics (SPH) and finite element methods (FEM) were used to study the process of abrasive jets cutting rock under confining pressure conditions. The results show that the failure of rock was mainly due to compressive and shear stresses, while the propagation of cracks was dominated by tensile stress. Under confining pressure, the cracks in rocks were mainly horizontal. The damage depth significantly decreased with increasing confining pressure, while the damage width first decreased and then increased. The critical distance between two slits without penetration is four times the diameter of the abrasive jet. When the cutting direction of the abrasive jet was perpendicular to the maximum stress, the relief range of the confining pressure formed was larger. The results have certain guiding values for revealing the mechanism of abrasive jet impact rock breaking and engineering applications.

Pressure‐assisted binder jetting for additive manufacturing of mock energetic composites

AbstractAdditive manufacturing (AM) has emerged as a promising approach to achieve energetic materials (EMs) with intricate geometries and controlled microstructures, which are crucial for safety and performance optimization. However, current AM methods still face limitations such as limited densities and inadequate solids loading. To overcome these limitations, we have developed a pressure‐assisted binder jet (PBJ) process that has the potential to allow for the fabrication of intricate EMs while preserving their desired properties. This study aims to investigate the effects of printing parameters on the microstructures and properties of EMs, including density, solids loading, mechanical properties, and heterogeneity. Our results demonstrate that the PBJ process achieves exceptional properties in EMs, including densities up to 83.4 % and solids loading up to 95.4 %, surpassing those achieved by existing AM processes. Furthermore, the mechanical properties of the fabricated EMs are comparable to those achieved using conventional fabrication techniques, including a compressive strength of 3.32 MPa, a Young's modulus of 16.68 MPa, a Poisson's ratio of 0.45, a shear modulus of 5.73 MPa, and a bulk modulus of 21.01 GPa. Various test cases were printed to showcase the ability of the PBJ process to create EMs with complex structures and exceptional properties. Micro‐computed tomography was employed to analyze the influence of printing parameters on the internal composition and microstructures of the printed specimens.

A comprehensive study of diverse techniques for enhanced physicochemical and structural properties of bio-calcium from hybrid catfish bone

This research examined the impact of various comparative preparation methods on enhanced physicochemical, and structural properties of bio-calcium (BC) from hybrid catfish bone. Raw hybrid catfish bones (RB) were used to make bio-calcium in four steps. High-pressure water jet processing produced washed bone (WB), soaking the bone in an alkaline solution to remove proteins (PR), immersing it in ethanol to remove lipids (LR), then bleaching, and grinding it to make bio-calcium powder. The BC had greater lightness values (L*) (p < 0.05), and contained significant calcium, and phosphorus. The SDS-PAGE showed three significant protein bands with molecular weights of 250, 133, and 116 kDa. The crystalline structure of hydroxyapatite in BC was confirmed using X-ray diffraction (XRD), and Fourier transform infrared (FT-IR) spectroscopy. The percentage of crystallinity of BC had a notable rise, increasing from the RB to BC of 36.25%–45.32%. The BC powder exhibited a consistent distribution of particle sizes, ranging from 2 to 10 μm. Additionally, the analysis of elemental profiles, and mappings using scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS) revealed that BC exhibits a significant concentration of calcium, and phosphorus. BC showed superior %bioavailability of calcium (18.94%) in an in vitro simulated gastrointestinal system (GIMs) compared to RB (10.58%), and calcium carbonate (11.19%). Hence, the BC production process proved to be a viable method for acquiring premium-grade BC, which holds potential for further development as a calcium dietary supplement.

Characterization and optimization of abrasive water jet machining parameters of aluminium/silicon carbide composites

Due to the complexity of high temperature and cutting tool wear, most machined components are still facing problems in terms of harder functional fillers that reinforce aluminium matrix composites. Conversely, abrasive water jet machining (AWJM) incredibly useful for the cutting of anisotropic and non-homogeneous metal matrix composites. In this research article, silicon carbide (SiC) particulates were utilized as reinforcement in the AA6026 matrix material (AA6026/SiC) and machined using AWJM under different process parameters namely SiC loading, traverse speed and stand-off distance. Two different compositions of SiC (4, and 8 wt%) were considered to fabricate AA6026 composites using the stir casting. In addition, outputs have been examined, e.g., surface roughness, material removal rate, and kerf angle. An optical microscope, scanning electron microscope, Brinell hardness tester and universal testing machine have been used to characterize the matrix material AA6026 and its composites. Microstructural analysis revealed that the inclusion of SiC particulates in AA6026 affects the very fine grain size of the composite. Furthermore, the 8 wt% composite exhibits the evolution of the Al-Si eutectic phase during solidification. Processing of these composites was performed using the L27 orthogonal geometry, successfully improving the parameters of the abrasive water jet process. The output response shows that reducing the SiC load improves the surface roughness under the key parameters of traverse speed and stand-off distance. However, increasing the SiC loading increases the material removal rate and kerf angle under the key parameters, namely traverse speed, and stand-off distance.

A Study on Powder Deposition Characteristics of Binder Jetting Process According to Design of Scraper with Multi-steps

A Study on Powder Deposition Characteristics of Binder Jetting Process According to Design of Scraper with Multi-steps

Modeling investigation on transient behaviors of gaseous ammonia jet flow with direct injection

This study investigates the characteristics of gaseous ammonia jets under an injection pressure of 0.8 MPa and an ambient pressure of 0.1 MPa, using LES and RANS simulation approaches to inform applications of ammonia in internal combustion engines. A three-dimensional constant volume chamber model was established, and the Dynamic Structure model was applied in LES modeling with AMR techniques. The near-nozzle transient structures were successfully captured. Furthermore, a direct comparison between LES and RANS simulation was made, and main jet characteristics were investigated. LES outperforms RANS in predicting the instantaneous structures of ammonia jets and provides a more distinct visualization of oblique shock waves and diamond-like shock cells. RANS excels at displaying averaged features with a smoother distribution curve that represents self-similar characteristics. Additionally, the transient characteristics of ammonia and hydrogen jets were compared. The vortex formation and mixing process in ammonia jets occur at a much slower rate compared to hydrogen jets. Meanwhile, transient vortex ring behaviors were analyzed in detail, including their development tendencies regarding initial, secondary, and broken vortex formation. It is revealed that petal-like swirling movements are strongly correlated with the air–fuel mixing process.

Optimization of the Morphology of the Removal Function for Rotating Abrasive Water Jet Polishing.

Abrasive water jet polishing has significant advantages in the manufacturing of complex optical components (such as high-slope optical component cavities) that require high-precision manufacturing. This is due to its processing process, in which the polishing tool does not make direct contact with the surface of the workpiece, and instead maintains a considerable distance. However, the removal functions of most existing abrasive water-jet polishing technologies do not possess strict symmetry, which significantly impacts the ability to correct surface figure errors. Therefore, this study implements rotating abrasive water-jet polishing based on traditional abrasive water jet processing to optimize the removal function, which turns it into a Gaussian form; thus, obtaining a type of removal function more suitable for CCOS polishing. This paper derives an empirical formula between the distance s' from the peak removal point of the removal function to the stagnation point and the nozzle tilt angle α, based on geometric relationships and experimental results, analyzes the relationship between material removal efficiency, nozzle tilt angle, and standoff distance. Finally, this paper verifies through experiments the validity of this empirical formula under different process parameters. Therefore, this study obtains the process conditions that allow rotating abrasive water-jet polishing technology to achieve a stable Gaussian form removal function, and the appropriate process parameters to be selected in conjunction with polishing efficiency; thereby, effectively improving the removal function's corrective ability and manufacturing efficiency. It provides theoretical support for the processing capability and process parameter selection of abrasive water-jet polishing technology, solves the problem of limited shaping capability of existing abrasive water jet tools, and significantly improves the manufacturing capability of high-end optical components.