Particles In Jet Research Articles

ТЕОРИЯ РАСПЫЛИВАНИЯ ЖИДКОСТИ ФОРСУНКАМИ

The main characteristics are considered and calculations of the main indicators of nozzle devices are given. Laboratory tests of nozzles of various configurations were carried out to determine the working width of the spot at different distances to the irrigated surface and the angle of the spray pattern, and dependencies were established to determine their effective mode of operation. As a result of testing nozzles with different spray patterns when determining the impact force of the jet, it was found that as the spray angle increases, the value of the impact force of the jet F decreases. This is due to the fact, that with an increase in the initial jet velocity, the torch length reaches a maximum, not only does the kinetic energy increase, but the sizes (diameters) of the sprayed medium drops, which leads to a decrease in droplet mass and an increase in the aerodynamic resistance of the torch jet particles. A bench for determining the impact force of a jet of various nozzles was developed and test results were obtained. During operation, due to the erosive wear of the jet holes of the nozzles, its diameter increases, as a result, the working atomization pressure drops, and the number and size of large particles increase. Therefore, periodically it is necessary to check the diameter of the nozzle holes and not to use nozzles, that have a hole diameter greater than the initial one by 10 or more percent. In the study of nozzles, the dependences of nozzles’ characteristics on the initial parameters of the outflow of the liquid jet to the dispersity and shape of the torch were established. The values of irrigation spot width are established depending on the angle of the torch and the distance from the nozzle to the irrigated surface. The magnitude of the impact force of the jet, which occurs at the point of contact of the fluid jet with the irrigated surface, is determined.

Measurement of jet radial profiles in Pb–Pb collisions at [formula omitted] TeV

The jet radial structure and particle transverse momentum (pT) composition within jets are presented in centrality-selected Pb–Pb collisions at sNN=2.76 TeV. Track-based jets, which are also called charged jets, were reconstructed with a resolution parameter of R=0.3 at midrapidity |ηch jet|<0.6 for transverse momenta pT,ch jet=30–120 GeV/c. Jet–hadron correlations in relative azimuth and pseudorapidity space (Δφ,Δη) are measured to study the distribution of the associated particles around the jet axis for different pT,assoc-ranges between 1 and 20 GeV/c. The data in Pb–Pb collisions are compared to reference distributions for pp collisions, obtained using embedded PYTHIA simulations. The number of high-pT associate particles (4<pT,assoc<20 GeV/c) in Pb–Pb collisions is found to be suppressed compared to the reference by 30 to 10%, depending on centrality. The radial particle distribution relative to the jet axis shows a moderate modification in Pb–Pb collisions with respect to PYTHIA. High-pT associate particles are slightly more collimated in Pb–Pb collisions compared to the reference, while low-pT associate particles tend to be broadened. The results, which are presented for the first time down to pT,ch jet=30 GeV/c in Pb–Pb collisions, are compatible with both previous jet–hadron-related measurements from the CMS Collaboration and jet shape measurements from the ALICE Collaboration at higher pT, and add further support for the established picture of in-medium parton energy loss.

Erosion resistance of engineering ceramics and comparative assessment through Wiederhorn and Evans equations

Resistance to erosion is one of the most desirable characteristics of materials that must undergo a tribological interaction, where engineering ceramics play an important role given their intrinsically enhanced mechanical properties. The fracture toughness and hardness of Al2O3 (alumina), ZrO2 (zirconia) and Si3N4 (silicon nitride) were compared with their erosion rate when subjected to solid particle jet wear from different incidence angles (30°, 60° and 90°) at room and elevated temperatures (25 °C and 850 °C), aiming to compare the results with the analytical Wiederhorn and Evans equations. Erosion rates are directly related to fracture toughness, but not with hardness. Scanning electron microscopy allowed to identify particular fracture mechanisms of each material at each temperature, especially for ZrO2 given its temperature-induced polymorphism confirmed by X-ray diffraction tests.

Material synthesis, characterization, and machining performance of stir cast beryllium copper alloy composites

Copper alloys have important industrial roles due to their excellent properties. Beryllium copper is one of the copper-based alloys with the highest strength and excellent metal working and machining properties. Beryllium copper alloy composite is fabricated by the stir casting method. Its characteristics are studied with scanning electron microscopy and energy dispersive analysis of X-rays. The material properties of the stir cast beryllium copper alloy composites are evaluated. Hardness can be increased by the addition of silicon carbide particles. Abrasive water jet machining is an effective unconventional machining process, in which high pressure water jet and abrasive particles are used to remove material. Response parameters such as material removal rate and circularity of holes are considered. Response parameters of abrasive water jet machining are compared to electrical discharge machining. The most influential factor for the responses is determined by analysis of variance. Optimization of machining parameters is performed with the Taguchi method.

Aerodynamic focusing of an abrasive air jet and its effect on machining resolution

To decrease the size of the eroded footprint resulting from abrasive air jet machining, the aerodynamic focusing of an abrasive particle jet was investigated. Using a slot nozzle abrasive jet, the best focusing employed a pair of bounding air jets tilted 60° to the abrasive jet, at an impingement height of approximately 10% of the standoff distance from the workpiece. An optimum bounding jet pressure existed to achieve the maximum focusing, resulting in a machined channel width reduction of up to 16% with a corresponding depth increase of 84% compared to no bounding jets. A novel apparatus was constructed to generate an annular bounding jet impinging a central abrasive jet formed from a round nozzle. However, aerodynamic focusing, in this case, could not be achieved due to the large stagnation zone that formed near the annular jet impingement. Computational fluid dynamics simulations were used to understand the mechanics of particle focusing.

A new method for studying the ablation/erosion properties of silicone rubber composites based on multi-phase flow

To evaluate the ablation/erosion resistance of the silicone rubber composites, a new method based on multi-phase flow produced by oxygen–kerosene ablation test device was put forward and a new kind of particle was applied in the test. The phase transition characteristics of B2O3 particles and Al2O3 particles in high-temperature flame jet were investigated and compared. On this basis, the ablation tests of silicone rubber composites under the erosion of particles were carried out. The results show that erosion of particles is an important factor in ablation. Compared with Al2O3 particle, B2O3 particle melts, evaporates and forms the liquid coating in the oxygen–kerosene flame jet, which can be used to simulate condensed phase particle in rocket engine. After the multi-phase flow ablation test ablation condition with B2O3 particles, the ablation rates are relatively small and reasonably, and a small ablation pit is formed on the surface of the silicone rubber composites. In the profile of ablated materials, a multi-layer structure with char layer, pyrolysis layer and matrix is formed. In the process of particle impact, the melting layer on the surface of B2O3 alleviates the impact force, thereby reducing the erosion of particles. The feasibility and scientificity of the new method based on multi-phase with B2O3 particles used for ablation resistance of silicone rubber composites investigation is validated.

Numerical study on shock–dusty gas cylinder interaction

The interaction of a planar shock wave with a dusty-gas cylinder is numerically studied by a compressible multi-component solver with an adaptive mesh refinement technique. The influence of non-equilibrium effect caused by the particle relaxation, which is closely related to the particle radius and shock strength, on the evolution of particle cylinder is emphasized. For a very small particle radius, the particle cloud behaves like an equilibrium gas cylinder with the same physical properties as those of the gas–particle mixture. Specifically, the transmitted shock converges continually within the cylinder and then focuses at a region near the downstream interface, producing a local high-pressure zone followed by a particle jet. Also, noticeable secondary instabilities emerge along the cylinder edge and the evident particle roll-up causes relatively large width and height of the shocked cylinder. As the particle radius increases, the flow features approach those of a frozen flow of pure air, e.g., the transmitted shock propagates more quickly with a weaker strength and a smaller curvature, resulting in an increasingly weakened shock focusing and particle jet. Also, particles would escape from the vortex core formed at late stages due to the larger inertia, inducing a greater particle dispersion. It is found that a large particle radius as well as a strong incident shock can facilitate such particle escape. The theory of Luo et al. (J. Fluid Mech., 2007) combined with the Samtaney–Zabusky (SZ) circulation model (J. Fluid Mech., 1994) can reasonably explain the high dependence of particle escape on the particle radius and shock strength.

Determination of retained tritium from ILW dust particles in JET

Abstract Quantitative tritium inventory in dust particles from campaigns in the JET tokamak with the carbon wall (2007-2009) and the ITER-like wall (ILW 2011-2012) were determined by the liquid scintillation counter and the full combustion method. A feature of this full combustion method is that dust particles were covered by a tin (Sn) which reached 2100 K during combustion under oxygen flow. The specific tritium inventory for samples from JET with carbon and with metal walls was measured and found to be similar. However, the total tritium inventory in dust particles from the ILW experiment was significantly smaller in comparison to the carbon wall due to the lower amount of dust particles generated in the presence of metal walls.

An innovative combustion technology for a down-fired boiler with swirl burners: Gas/solid flow characteristics with various burner injection angles

Abstract: The eccentric-swirl-secondary-air combustion technology (ESSACT) is an innovative technology to comprehensively solve high NOx emission and unburned carbon content in fly ash of the down-fired boiler with swirl burners. In this study, a breakthrough idea (i.e. decreasing burner injection angle (θb)) is proposed to further greatly improve coal burnout of the improved boiler. Using a laser particle dynamic analyzer, the distributions of average and fluctuation velocities of gas/solid (GS) flows, distribution and decay of particle volume flux and jet trajectory of burner primary air in a 1:10 scale model of full-scale furnace at different θb of 0°, 8°, 15° and 25° are acquired. The effects of θb on GS flow characteristics (i.e. downward depth of GS flows, recirculation zones below arches and air flow fullness in the lower furnace) in the furnace are intensively studied. As the θb decreases, the maximum vertical velocity of GS flows increases in the whole lower furnace, and the vertical fluctuation velocity of GS flows and the turbulent intensity and diffusion also increase. With decreasing θb, maximum recirculation velocity and dimension of recirculation zone below arches both increase continuously, which is conducive to improving ignition and burnout of pulverized coal. Especially, the maximum recirculation velocity with θb decreasing from 25° to 15° and the dimension of recirculation zone below arches with θb decreasing from 15° to 8° increase more obviously. With decreasing θb, the ejection effects of vent air and staged air on GS flows from arches are more effective. In the region below staged air, the maximum particle volume flux for the θb of 0° and 8° is more than twice that for the θb of 15° and 25°. As a result, the downward depth of GS flows and air flow fullness in the lower furnace both increase with decreasing θb. To improve coal burnout of the down-fired boiler applying ESSACT, the θb is recommended to be set below 8°.

Shaped charge penetration into high- and ultrahigh-strength Steel–Fiber reactive powder concrete targets

Abstract Experiments on shaped charge penetration into high and ultrahigh strength steel-fiber reactive powder concrete (RPC) targets were performed in this paper. Results show that the variation of penetration depth and crater diameter with concrete strength is different from that of shaped charge penetration into normal strength concrete (NSC). The crater diameter of RPC is smaller than that of NSC penetrated by the shaped charge. The jet particles are strongly disturbed and hardly reach the crater bottom because they pass through the narrow channel formed by jet penetration into the RPC. The effects of radial drift velocity and gap effects of jet particles for a shaped charge penetration into RPC target are discussed. Moreover, a theoretical model is presented to describe the penetration of shaped charge into RPC target. As the concrete strength increases, the penetration resistance increases and the entrance crater diameter decreases. Given the drift velocity and narrow crater channel, the low-velocity jet particles can hardly reach the crater bottom to increase the penetration depth. Moreover, the narrow channel has a stronger interference to the jet particles with increasing concrete strength; hence, the gap effects must be considered. The drift velocity and gap effects, which are the same as penetration resistance, also have significant effects during the process of shaped charge penetration into ultrahigh-strength concrete. The crater profiles are calculated through a theoretical model, and the results are in good agreement with the experiments.

Optical investigations on particles evolution and flame properties during pulverized coal combustion in O2/N2 and O2/CO2 conditions

The evolution of soot and coal/char as well as the flame properties, during pulverized coal combustion in O2/N2 and O2/CO2 conditions, were experimentally studied using optical diagnostics. The jet flames of pulverized coal particles were produced by using an entrained-flow reactor with optical access, and the oxygen concentrations of the gas carrying pulverized coal particles were varied between 0 and 100%. A combination of laser-induced incandescence (LII), laser-induced fluorescence (LIF), elastic laser scattering (ELS), and radiative emission detection methods was employed to characterize the spatial distributions of soot, polycyclic aromatic hydrocarbons (PAHs), coal/char, and the flame temperature. The measured results revealed that ELS signal intensity declined accompanied with the appearance of LIF and LII signals. An evolution pattern of PAHs and soot was investigated to be similar to those found in gaseous hydrocarbon diffusion flames. An abrupt expansion of the pulverized coal particle jet was observed from ELS measurement at the position where coal particle jet was ignited, which was likely attributed to the more intensive dispersion of small particles caused by a rapid elevation of the flame temperature. As the oxygen concentration increased, the ignition distance of pulverized coal particle jet became shorter and the flame temperature increased. The PAHs and soot-loaded regions were shrunk and the sooting region shifted to upstream position of the flame. Nonetheless, replacing N2 with CO2 tended to increase the ignition distance but lower the flame temperature. The peak LII signal, corresponding to the maximum soot volume fraction, increased to a maximum and then decreased with oxygen concentration and the intensity for the O2/N2 case was far larger than for the O2/CO2 case. However, the LIF signal intensities exhibited an apparent decrease with increasing oxygen concentration, and they were nearly consistent when N2 was replaced with CO2, which may imply that the effect of suppressing radical formation on PAHs evolution in CO2 atmosphere was negligible.

Glass Surface Decoration by Sandblasting Technique: A Case Study

The properties of glass; mechanical robustness, dielectric properties and transparency make it very useful for micro-machining decoration particularly in architectural designs and beautification. In this paper, sandblasting, ONE OF the commonest glass designing techniques was used to etch the name and logo of “THE FEDERAL UNIVERSITY OF TECHNOLOGY, AKURE” on a piece of glass of dimension 600mm×400mm×4mm. The method made use of a particle jet directed towards the glass for material removal by mechanical erosion via the impingement of high velocity abrasive particles. The result gave rise to a well finished glass material, useful for office design and walk way design within the University. Keywords : Sandblasting, etching, glass micro-machining, abrasive blasting, fabrication, glass, design. DOI : 10.7176/ADS/72-03 Publication date : April 30 th 2019

Velocity and Temperature of In-Flight Particles and Its Significance in Determining the Microstructure and Mechanical Properties of TBCs

The correlation between particle in-flight parameter, defect content and mechanical property of yttria-stabilized zirconia coating was systematically studied in the present work. The melting state of in-flight particle during spraying was simulated using computational fluid dynamics. The results suggested that, with the increase of velocity and temperature of in-flight particles in the plasma jet, the particles changed from partially melted state to fully melted one. As a result, the total defect content of as-sprayed coating gradually decreased, while elastic modulus and microhardness increased correspondingly. However, the fracture toughness of as-sprayed coating reached a maximum value when the total defect content reached approximately 9.1%.

Modification of Jet Structure in High-Multiplicity pp Collisions due to Multiple-Parton Interactions and Observing a Multiplicity-Independent Characteristic Jet Size

We study the multiplicity dependence of jet structures in pp collisions using Monte Carlo event generators. We give predictions for multiplicity-differential jet structures and present evidence for a nontrivial jet shape dependence on charged hadron event multiplicity that can be used as a sensitive tool to experimentally differentiate between equally well-preforming simulation tunes. We also propose a way to validate the presence and extent of effects such as multiple-parton interactions (MPI) or color reconnection (CR), based on the detection of nontrivial jet shape modification in high-multiplicity events at high pT. Using multiplicity-dependent jet structure observables in various pT windows might also help understanding the interplay between jet particles and the underlying event (UE). We introduce a multiplicity-independent characteristic jet size measure and use a simplistic model to aid its physical interpretation.

Washing Technology with Ice Particles Jet Generated by the Phase Change in a Converging-Diverging Nozzle

Washing Technology with Ice Particles Jet Generated by the Phase Change in a Converging-Diverging Nozzle

Combustion characteristics of solid propellants under high-temperature dense-particle erosion conditions

High-concentration alumina particle jet can erode the surface of the solid propellant inside a solid rocket motor under some special conditions such as flight acceleration. Because of lack of effective testing methods, knowledge of the combustion characteristics of solid propellants under dense-particle erosion conditions is very limited. In this study, the combustion characteristics of hydroxyl‑terminated polybutadiene and nitrate ester plasticized polyether propellants were investigated using real-time X-ray radiography technology and an overload simulation erosion motor. The high-temperature dense-particle jet can cause erosive burning of the solid propellants. No clear threshold velocity is found for the particle erosive burning, and the erosive burning rate increases with the particle velocity. The erosion of the dense-particle jet includes the heat flux increment effect and mechanical damage effect, and the particle erosive burning is mainly caused by the heat flux increment effect of the particles. Numerical simulation results show that the particles can impact the propellant surface at a very low speed and cause heat flux increments; this explains the lack of a clear threshold velocity for the particle erosive burning of solid propellants.

Characterization of the topology of proton-proton collisions

In the LHC’s high-energy proton-proton collision experiments, a great amount of particles are produced after the interaction processes. To better understand the production mechanisms of such particles, it is convenient to study and characterize their topology. To do so, we shall study two-particle correlation functions. These functions are calculated with data generated by the PYTHIA event simulator, and in several different intervals of correlated particle’s transverse momentum. In this way, we may observe a particle jet structure, observed in the experiments and previewed by perturbative QCD, and how such structure is affected by different hadronization models.

The Influence of Particle Flux Density and Particle Size Distribution in Surface Morphology of Cold Spray Coatings

In this article the coupling between the Cold Gas Dynamic Spray (CS) particle flight instance just before impact and resulting surface morphology after impact of a cluster of particles are investigated with a view to understanding the complex CS process for possible optimisation for the CS fabrication process in nano thin films. This study identifies two main variables for the analysis namely particle flux density and particle size distribution and examine their influence in the structural properties of the coatings, in particular, the deposition efficiency of the cluster of particles and its applications in functional properties of the coatings. This process determines the deposition parameters that characterize the surface roughness. Given r as a radial distance from the axis of a nozzle, and R as the maximum radial distance reached by the particles, the results indicate that increasing the flux density of a cluster beyond a certain limit (yet to be identified) creates a deformation behaviour closely related to that of a single particle, however this process lowers the deposition efficiency as r approaches R; where R is the radius of the nozzle particle flux distribution radius at impact surface and r is measured from the centre axis, (where r = 0), of the impinging particle jet to towards the peripheral (where r = R). A similar characteristic on the morphology of the surfaces is observed when particles have a varying particle size: the smaller particles (and indeed any other particle sizes) that hit the target substrate at the peripheral at an angular velocity and possibly with reduced velocity from the average particle flux jet velocity, eject outward due to the oblique impact imposed by the traverse velocity component. These findings have potential applications in fabrication of functional surfaces for various applications and provide us with control variables necessary for modifying the surfaces.

Experimental Study on Erosion⁻Corrosion of TP140 Casing Steel and 13Cr Tubing Steel in Gas⁻Solid and Liquid⁻Solid Jet Flows Containing 2 wt % NaCl.

To study the erosion–corrosion characteristics of TP140 casing steel and 13Cr tubing steel in oil fields, we performed gas–solid and liquid–solid jet flow experiments to control particle addition, jet angle, and flow velocity and measure erosion and corrosion components. Meanwhile, we used a standard three-electrode system to study the changes in electrochemical parameters on a metal surface in a two-phase flow containing 2 wt % NaCl. Results showed that erosion is mainly dominated by the flow velocities and impact angles of particles, and corrosion rate is mainly affected by liquid flow rate. The erosion rates of the two materials increase with flow velocity, and the critical angle of maximum erosion rate exists. Meanwhile, flow velocity growth increases the current density on the TP140 surface while reducing the corrosion potential of 13Cr, but the effect of the angle on the two parameters is relatively small. The uniform corrosion of TP140 increases the erosion rate in the range of 10–20%, and the pitting of 13Cr increases the erosion rate in the range of 30–90%, indicating that the interaction between the erosion and corrosion of stainless steel is obvious.

Exploring jet profiles in Pb-Pb collisions at 5.02 TeV with the ALICE detector

In this contribution, we present measurements of inclusive jet production with the ALICE detector in Pb-Pb collisions at sNN=5.02TeV. Production cross sections of charged particle jets and fully reconstructed jets are measured with jet resolution parameters R = 0.2 and 0.3. To quantify the medium induced parton energy loss, jet nuclear modification factors (RAA) are measured by utilizing POWHEG+Pythia8 predictions as reference cross section in pp collisions. We also calculate the ratio of jet production cross sections for jets reconstructed with different cone radii to explore the jet radial profile in Pb-Pb collisions. The ratios of jet cross sections are compared to a pp reference predicted by POWHEG+Pythia8 and in-medium energy loss model prediction by the JEWEL Monte Carlo event generator.