Jet Process Research Articles

The Generation Methods and Applications of Cavitating Jet by Using Bubble Collapse Energy

Cavitation is a dynamic process characterized by the formation, growth, and collapse of vapor or gas vacuoles in liquids or at the liquid–solid interface, initiated by a local pressure drop. This phenomenon releases concentrated energy through microjet impacts and shock waves, leading to a violent exchange of energy with the surrounding environment. While cavitation is often perceived as detrimental, certain aspects can be harnessed for practical applications. Relevant studies have shown that cavitating jets provide high operating efficiencies, reduce energy consumption per unit, and have the potential for waste treatment. This paper presents three types of cavitating jets: central body cavitation, oscillatory cavitation, and shear cavitation. Additionally, the formation process of a cavitating jet and the effects of various factors on jet performance are discussed. Following an in-depth examination of the cavitation phenomena, subsequent chapters explore the applications of cavitating jets in material surface enhancement, cleaning, and energy exploration. Furthermore, recommendations for future research on cavitating jets are provided. This paper provides a comprehensive literature review on cavitating jets.

Research on jet ignition phases and control parameters in an active pre-chamber optical engine under ultra-lean combustion conditions

The active pre-chamber (APC) jet ignition system is one of the primary technologies for achieving ultra-lean combustion and high thermal efficiency in engines. The impact of the jet process within the engine, as well as its control parameters, on emission pollutants (particularly soot particles) remains unclear. This study focuses on examining the effects of various low-flow injection control strategies on engine combustion and emissions by using optical experiments and numerical simulations. It also explores the impact of different ignition advance angles (ignition timings) based on a short pre-chamber mixing interval to observe ignition combustion, flame propagation, and emission characteristics under ultra-lean conditions (λ = 2.0). The main conclusions are as follows. Appropriately increasing the injection mass can enhance engine load. However, further increases in injection mass significantly raise particulate emissions, resulting in an increase in particle number by up to more than 37-fold, especially for small particles in the 5–––10 nm size range. The chemical reaction between the luminous jet flame and the bright incandescent wake jet flame, as captured by high-speed photography, effectively characterizes the various stages of jet ignition. To reduce particulate matter emissions, it is crucial to avoid the foreseeable wake jet flame caused by the enrichment of the jet mixture in the pre-chamber. The low-flow injection timing should neither be too early nor close to the ignition spark timing. The early injection causes fuel to accumulate at the top of the pre-chamber, hindering the jet flame’s propagation into the main combustion chamber. Late low-flow injection leads to fuel enrichment, resulting in uneven mixing and poor atomization and diffusion due to short mixing times. Ignition after a short mixing time interval tends to increase knocking, resulting in intense combustion and an advanced phase, which slightly reduces load and combustion stability. Regarding the heat release ratio, the total heat release from the two combustion stages in the pre-chamber should ideally account for about 5–6 % of the heat release in the main chamber.

A new optimization strategy, the influence of hollow electrode chamfers on the development of helium atmospheric pressure plasma jets

This work suggests applying chamfering treatment to the plasma generator of the empty electrode structure. Enhancing the electrodes’ physical structure can significantly improve plasma characteristics without requiring intricate control systems. Experiments have shown that changes in the electrode’s shape can lead to changes in the formation of the atmospheric pressure plasma jet. Specifically, our observations indicate that an increase in the chamfer radius leads to an increase in the ignition voltage and a greater density of reactive species inside the jet. We developed a multi-channel equivalent circuit model to describe the discharge process of a plasma jet. Then, using the mixed layer theory, we investigated the effect of the chamfer radius on the plasma jet. Our findings suggest that chamfering increases the effective discharge area, resulting in more discharge channels in the model. This leads to a higher density of reactive species. Additionally, chamfering improves the mixing of helium and air, increasing the concentration of N2 and O2. This consumes some of the avalanche electrons and raises the ignition voltages, ultimately enhancing the chemical reactivity of the plasma jet. This work provides new ideas for the optimization strategy of atmospheric pressure plasma radiation devices.

Enhanced Oxygen Evolution Reaction Performance of NiMoO4/Carbon Paper Electrocatalysts in Anion Exchange Membrane Water Electrolysis by Atmospheric-Pressure Plasma Jet Treatment.

NiMoO4 was grown on carbon paper (CP) by a hydrothermal method. A rapid and high-temperature atmospheric-pressure plasma jet (APPJ) process was used to generate more oxygen-deficient NiMoO4 on the CP surface to serve as an electrode material for the oxygen evolution reaction (OER). After 60 s of APPJ treatment, the overpotential of the electrode at 100 mA/cm2 decreased to 790 mV and that at 10 mA/cm2 decreased to 368 mV. Additionally, the charge transfer resistance decreased from 2.8 to 1.2 Ω, indicating that APPJ treatment effectively reduced the electrode overpotential and impedance. The effect of NiMoO4/CP/APPJ-60 s on the anion exchange membrane water electrolysis (AEMWE) system was also tested. At a system temperature of 70 °C and current density of 100 mA/cm2, the energy efficiency reached 95.1%, and the specific energy consumption decreased from 4.02 to 3.83 kWh/m3. These results demonstrate that the APPJ-treated NiMoO4/CP electrode can effectively enhance the OER performance in water electrolysis and improve the energy efficiency of the AEMWE system. This approach shows promise in replacing precious metal electrodes, thereby potentially reducing the cost and providing an environmentally friendly alternative.

Prediction and Analysis of Borosilicate Glass Surface Deformation Induced by Flame Jet

To address the issues of low processing efficiency, poor forming accuracy, and internal damage in glass material processing, this study proposes the use of flame jet forming. However, the mechanism of flame jet processing requires further elucidation. This research investigates the relationship between the indentation morphology on the glass surface and the inlet velocity of the flame jet. A theoretical model was established through mathematical analysis to reflect this relationship. The model’s accuracy was validated using numerical simulation methods. By comparing experimental data with theoretical model results, surface tension was incorporated, and the model was iteratively optimized using MATLAB R2024a. The final optimized model demonstrated an absolute error range of 0.009 to 0.069 mm. This study confirms the feasibility of flame jet processing and enriches the understanding of its mechanism, providing a novel, efficient, and precise method for processing glass materials.

Numerical simulation of boiling dynamics in liquid Lead-Bismuth injected with multi-rupture high-pressure water jets

Once a steam generator tube rupture (SGTR) accident occurs in a lead-based fast reactor, it can trigger a domino effect of heat transfer tube ruptures, leading to a loss-of-flow accident involving multiple ruptures. This paper employs numerical methods to investigate the jet boiling phenomenon associated with the injection of sub-cooled water into high-temperature lead‑bismuth eutectic (LBE) through multiple nozzles. It explores how nozzle spacing, number, and diameter impact jet characteristics. Additionally, it analyzes flow characteristics and heat transfer mechanisms from the perspective of jet interaction. The study identifies critical areas within the multi-nozzle jet, specifically the three-phase mixing region, LBE entrainment region, water core region, and steam plume region. In scenarios where nozzle spacing is narrow or nozzle diameters differ significantly, the jet's base may undergo fragmentation. The jet process is categorized into two stages: the transition stage and the stable stage. During the stable stage, the mass flow rate of sub-cooled water remains relatively constant, with nozzle spacing exerting minimal influence on it. When considering the cross-sectional area of a single nozzle, an increase in nozzle diameter elevates the normalized mass flow rate, whereas the number and diameter of nozzles have little effect on it. Jet penetration depth is inversely related to nozzle spacing. As the number and diameter of nozzles increase, penetration depth initially rises and then decreases. Nozzle spacing has a minor influence on the jet's steam volume, while the number and diameter of nozzles are positively correlated with steam volume. Conversely, the number and diameter of nozzles negatively correlate with normalized steam volume.

Non-global logarithms up to four loops at finite-Nc for V/H+jet processes at hadron colliders

We extend our previous work [1] on calculating non-global logarithms in e+e− annihilation to Higgs/vector boson production in association with a single hard jet at hadron colliders. We analytically compute non-global coefficients in the jet mass distribution up to four loops using the anti-kt jet algorithm. Our calculations are performed in the eikonal approximation, assuming strong energy ordering for the emitted gluons, thus capturing only the leading logarithms of the distribution. We compare our analytical results with the all-orders large-Nc numerical solution. In general, the gross features of the non-global logarithm distribution observed in the e+e− case remain valid for the V/H+jet processes.

Synthesis of TiO2-brookite nanorods and TiO2-Au composites for decomposition of organic dyes in water

This study employed a plasma-liquid interaction technique at room temperature to modify TiO2 nanocrystals in the brookite phase and coat their surface with gold nanoparticles (AuNPs). The technique was further utilized to reduce Au3+ ions to Au0, eliminating the need for chemical agents and reducing reaction time. The resulting TiO2-Au photocatalysts were then tested under visible light to evaluate their ability to degrade the dyes rhodamine 101 (RB101) in water. The findings indicated that the most effective degradation of RB101 molecules occurred at low dye concentrations (10 ppm) and low photocatalyst loadings with a ratio of 4. In comparing two different preparation methods, the TiO2-Au sample created using a micro-plasma process with a direct current (DC) source exhibited higher photocatalytic activity (87 % after 4 hours) compared to the sample created using a plasma jet process with an alternating current (AC) source. This research holds significance for the advancement of photocatalytic materials with potential environmental applications.

Effects of particle size, binder wettability, and sintering atmosphere on the microstructural and mechanical properties of binder jetted 18Ni300 alloy

A fully dense 18Ni300 mold steel was firstly prepared by the binder jetting (BJ) process. We developed a water-based binder characterized by its low viscosity, which significantly enhanced the penetration of binder into the fine powder layer. This process resulted in a deep, narrow cross-section due to reduced flow resistance, leading to strong inter-layer bonding and high surface quality of the green part. The densification behavior of 18Ni300 BJ green parts with different particle sizes was meticulously analyzed. A remarkable tensile property of YS = 783 MPa, UTS = 1012 MPa and EL = 8.8% were obtained in sintered 18Ni300 alloy with fine powder under 1460 °C and 50 mTorr vacuum. Building on thermodynamic theory, we introduced a novel criterion to assess the oxidation reactions in 18Ni300 parts fabricated by the BJ method during sintering under different atmospheric conditions.

The effect of non-perpendicular incidence angles on discharge characteristics in an argon atmospheric plasma jet impinging on metal, water and glass substrates

The spatial–temporal discharge behavior of an AC argon plasma jet tilted at non-perpendicular incidence angles (60°, 45°, and 30°) interacting with an ungrounded metal, water, and glass plate placed on the jet propagation track was studied by the fast-imaging technique. The conductivity of surface and incidence angles plays an essential role in the discharge current and dynamic process of the plasma jet. The nearly consistent time delay between subsequent breakdowns occurred four times for metal and two times for glass treatments. The mean luminous intensity of the plasma in one discharge cycle at the discharge area between ground electrode and target surface region for the water and glass case decreased by 39.5% and 20.5% when the incidence angle decreased from 60° to 30°, respectively. In particular, the incidence angle and gas flow rate notably impacted the spatial extension behavior created on the glass surface but had no significant difference in discharge characteristic of plasma jet with metal case. In addition, two equivalent circuit models were developed based on the simulation of the micro-discharges and the geometry of the “plasma jet–substrate” system, respectively. These results will obtain further insight into the underlying mechanisms of plasma-target interaction and facilitate the designing of appropriate jet for environmental and biomedical applications.

Analysis of the unsteady flow characteristics of underwater supersonic gaseous jets

To examine the unsteady flow characteristics of underwater supersonic gaseous jets under different jet expansion conditions, a sophisticated numerical model is created. This model accurately predicts the intricate multiphase flow by considering the compressibility of the jet gas and energy exchange, which is then rigorously validated against experimental data. The development process of underwater supersonic gaseous jets displays notably unsteady features in terms of jet morphology, flow structure, and various flow field parameters when compared to atmospheric conditions. The unsteady phenomena, such as necking, breaking, bulging, and back-attack, are observed alongside significant pressure pulsations. These unsteady phenomena occur at a considerable distance from the nozzle exit under under-expanded conditions, while pressure pulsations do not impact the internal gas flow within the nozzle. However, under full-expanded and over-expanded conditions, unsteady phenomena near the nozzle exit lead to oscillatory pressure, causing shock waves to propagate inside the nozzle. This results in a notable increase in internal pressure pulsation and mass flow rate within the nozzle, ultimately affecting engine performance significantly.

Extreme Drop Durability of Sintered Silver Traces Printed With Extrusion and Aerosol Jet Processes

Abstract Sintered silver is a popular material for printing conductive traces in printed hybrid electronics (PHE). However, due to the novel materials and printing techniques in PHEs, reliability still needs to be adequately characterized for all types of life-cycle application conditions. This paper focuses on characterizing the reliability of printed silver traces fabricated with extrusion printing and aerosol jet printing (AJP) processes, under severe shock conditions up to 40,000 g peak acceleration, resulting in very high strain magnitudes and strain rates. This study utilizes test specimens of cantilever form factor to study the reliability of three-dimensional printed traces and substrates. Traces printed using both techniques were found to withstand repetitive drops at up to 40,000 g peak acceleration. However, extrusion-printed silver traces were found to be more reliable than their AJP counterparts, because of the extruded traces' superior adhesion to the FR4 substrate and lack of sintering shrinkage cracks. Strain gauges revealed strains in excess of 10,000 με during a 40,000 g shock event. A calibrated finite element (FE) model revealed that the strains at the trace location exceeded 15,000 με during a 40,000 g shock event.

Numerical study on heat transfer and pressure performance of different suspension nozzles

The drying process of the lithium battery pole pieces makes extensive use of the suspension nozzle. It is of great significance to study the heat transfer and pressure steady-state characteristics of the suspension nozzle and to select the appropriate nozzle structure for the production of pole pieces. Based on the SSTk-ω\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext{SST }}k - \\omega$$\\end{document} turbulence model, this article numerically simulates the impact jet process of suspension nozzles with slits, injection holes, and effusion holes. There is a qualitative and quantitative analysis of the distribution of their velocity field, temperature field, local Nusselt number, average Nusselt number, local pressure coefficient, and average pressure coefficient, and the comprehensive performance index of the nozzle is proposed. The results show that when the weight factor of heat transfer performance α is less than 21.61% and the weight factor of pressure performance β is more than 78.39%, the comprehensive performance of the traditional suspension nozzle with double slits is the best. As the α is increasing, the β is decreasing. The comprehensive performance of the suspension nozzle with effusion holes is the best. The turbulent intermittence, interaction between neighbouring jets, and edge effects affect the heat transfer and pressure uniformity of the suspension nozzle.

Impact of rupture disk morphology on self-ignition during pressurized hydrogen release: A numerical simulation study

In the study of self-ignition during pressurized hydrogen release, the morphology of the rupture disk alters the flow and mixing processes of the gas jet, as well as the development of shock waves, thereby affecting the occurrence of self-ignition. This study employs the LES method based on the RNG-SGS model, EDC model, and NUIMech1.1 H2 combustion mechanism to investigate the flow mixing, shock wave development, and self-ignition phenomena under three different the rupture disk morphologies. The research findings indicate that as the growth trend of the rupture disk rupture ratio increases, the propagation speed of shock waves within the tube and the compression speed of the air and hydrogen-air mixing region accelerate, resulting in an earlier occurrence of self-ignition. A more complex rupture morphology leads to higher mixing rates between hydrogen and air and increased complexity of shock waves. Self-ignition initially occurs in the fuel-lean region of the boundary layer, followed by ignition at the center of the tube. The characteristic number of rupture disk is proposed to describe its impact on the self-ignition time. The competitive relationship between the two elementary reaction pathways of oxygen influences the development of the flame.

Soy proteins modified using cavitation jet technology

Soy proteins are seen as a promising alternative food source for meat with environmentally friendly properties. The problem is that the functional properties of soy proteins do not meet the needs of the food industry, and some existing modification technologies have adverse effects. Recently, cavitation jet technology (CJT) has been studied because it generates high heat, high pressure, strong shear and strong shock waves. This review summarizes the history and mechanism of cavitation jets. The energy generated during the cavitation jet process can open molecular structures, and the shock waves and microjets generated can pulverize the materials by erosion. The impact of the CJT on the morphology, structure, and functionality of soy proteins is discussed. The impact of combining CJT with other techniques on the production of soy proteins was also reviewed. The modification of proteins using two or more methods with complementary strengths, avoiding the disadvantages of certain techniques, makes the modification of proteins more effective. One of the most prominent effects is the combined treatment of cavitation jets with physical techniques. Finally, the review provides a comprehensive analysis of the application of modified soy proteins in the food industry and highlights promising avenues for future research.

Movement characteristics of coal powders at bottom of coalbed methane well under jet flow

AbstractThe removal and discharge of coal powders from coalbed methane wellbore is the key to maintaining continuous production. For this reason, based on the submerged jet theory, the force and migration starting conditions of coal powder particles deposited at the bottom of the coalbed methane well are analyzed by analyzing the cohesiveness of coal powders, and a model for the starting and migration of coal powders at the bottom of the well under submerged jet conditions is established; Considering the adhesion between coal dust, the adhesion coefficient is used to characterize the adhesion between particles, a mechanical model of coal dust particles deposited at the bottom of the well is established, and the corresponding calculation formula for the outlet flow rate of the coal dust cleaning nozzle is derived. The fluid mechanics parameters of the bottom of the well coal dust cleaning under different conditions are obtained, and the numerical simulation method is used to simulate the whole process of jet flushing of the bottom of the well coal dust deposited, and the effect of the bottom of the well jet flushing of coal dust deposits is analyzed, providing a theoretical basis for the bottom of the well coal dust flushing process.

Mechanical and Fatigue Properties of Ti-6Al-4V Alloy Fabricated Using Binder Jetting Process and Subjected to Hot Isostatic Pressing.

Binder jetting 3D printing is an additive manufacturing technique based on the creation of a part through the selective bonding of powder with an adhesive, followed by a sintering process at high temperature to densify the material and produce parts with acceptable properties. Due to the high initial porosity in the material after sintering, which is typically around 5%, post-sintering treatments are often required to increase the material density and enhance the mechanical and fatigue properties of the final component. This paper focuses on the study of the benefits of hot isostatic pressing (HIP) after sintering on the mechanical and fatigue properties of a binder jetting Ti-6Al-4V alloy. Two different HIP processes were considered in this study: one at 920 °C/100 MPa for 4 h, and a second at a higher pressure but lower temperature (HIP-HPLT) at 850 °C/200 MPa for 2 h. The effects of the HIP on the densification, microstructure, mechanical behavior, and fatigue properties were investigated. The results show that the HIP-HPLT process produced a significant increase in the mechanical and fatigue properties of the material compared with the as-sintered parts and even with the conventional HIP process. However, the fatigue and fracture micromechanisms suggest that the oxygen content, which resulted from the decomposition of the binder during the sintering process, played a critical role in the final mechanical properties. Oxygen could reduce the ductility and fatigue life, which deviated from the behavior observed in other additive manufacturing techniques, such as powder bed fusion (PBF).

Experimental research of bubble pulsation and jet under a double plate with circular hole

The pulsation and jet of underwater explosion bubble heavily affected by the boundary conditions. To explore the pulsation behavior and jet load of underwater explosion bubble near a damaged double structure, some double plates with circular hole were designed. The electric spark-generated bubble was employed to act as the underwater explosion bubble, and the experiment research on bubble pulsation and jet below the double plate with circular hole was carried out. The bubble pulsation and jet process were recorded by a high-speed camera, and the bubble jet load was measured by a wall pressure sensor. The results show that with the growth of the standoff distance, the bubble jet changes from the type I “gas-liquid two-phase jet” to the type II “gas-liquid two-phase jet”, and finally into the water jet. The load of the type I “gas-liquid two-phase jet” are characterized with high peak pressure with short duration in the initial pressure stage, and low pressure with long duration in the standing pressure stage. Whereas the type II “gas-liquid two-phase jet” feature high peak pressure with short duration in the initial pressure stage without standing pressure stage.

Numerical simulation on the pressure, turbulence, and λ2$$ {\lambda}_2 $$ vortex characteristics within the annular symmetric jet process under different vacuum degrees

AbstractThe jet impingement flash technology represents a paramount research subject in the domain of heat and mass transfer. To augment its commercial potential, the conjunction of annular multi‐aperture jet impingement with negative pressure flash evaporation is introduced in this study. The employment of an annular nozzle array is integral to the enhancement of the heat and mass transfer efficiency between the phases. The Realizable k‐ε model is used in this study. The negative pressure flash vaporization model was also developed by introducing a mass source term and an energy source term based on the Mixture model. The flow characteristics are characterized using numerical simulation. Additionally, the λ2 vortex identification criterion is investigated the vortex structure. The simulation results exhibit good agreement with experimental findings, demonstrating that a higher initial vacuum leads to a stronger flashing effect and a more chaotic movement of the flow group within the flow field. Thus, this study provides a reference method for the structural design and optimization of annular symmetric jet impingement negative pressure deammonia chemical equipment for engineering applications.

Experimental investigation of the structure effects on the energy recovery and jet impinging process in a fast cooling Joule-Thomson cryocooler

Compared to other Joule-Thomson (J-T) refrigeration systems, open-cycle miniature J-T cryocoolers offer exceptional rapid cooling capabilities, making them ideal for applications such as infrared guidance in missiles. The energy recovery in the heat exchanger enables the refrigerant reach saturation temperature quickly and improve the jet liquefaction rate. The heat transfer intensity of the impinging jet determines the cooling rate of the target. Hence, heat recovery and the impact jet process are the primary factors behind this rapid cooling, with distinct roles that require separate consideration. The structural differences will directly affect the energy recovery and jet impact process. To investigate these affects, an experimental system for rapid cooling J-T cryocoolers was established and three distinct cryocoolers with substantial structural variations were designed. The important structures, including jet height, orifice diameter, enhanced heat transfer treatment of the cold plate, heat exchanger height, and heat exchanger cone angle, were closely studied. In the range of our experiments, it was found that larger heat exchanger cone angle leading better energy recovery performance, while the length of the heat exchanger is limited by the type of refrigerant. Longer heat exchanger actually introduce too much thermal mass for the refrigerant with better energy recovery performance. In the aspect of jet impingement, enhanced heat transfer treatment and larger jet height will improve the jet heat transfer intensity.