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Showing papers on "Nozzle published in 2022"


Journal ArticleDOI
TL;DR: A review of the fluid dynamics of inkjet printing can be found in this paper , where the main challenges for present and future research are discussed both on the printhead side and on the receiving substrate side.
Abstract: Inkjet printing is the most widespread technological application of microfluidics. It is characterized by its high drop productivity, small volumes, and extreme reproducibility. This review gives a synopsis of the fluid dynamics of inkjet printing and discusses the main challenges for present and future research. These lie both on the printhead side—namely, the detailed flow inside the printhead, entrained bubbles, the meniscus dynamics, wetting phenomena at the nozzle plate, and jet formation—and on the receiving substrate side—namely, droplet impact, merging, wetting of the substrate, droplet evaporation, and drying. In most cases the droplets are multicomponent, displaying rich physicochemical hydrodynamic phenomena. The challenges on the printhead side and on the receiving substrate side are interwoven, as optimizing the process and the materials with respect to either side alone is not enough: As the same ink (or other jetted liquid) is used and as droplet frequency and size matter on both sides, the process must be optimized as a whole.

108 citations


Journal ArticleDOI
TL;DR: A fluid-structure coupling numerical model of an oil-jet lubricated cylindrical roller bearing (CRB) in a high-power gearbox is developed, in which the volume of fluid (VOF) method and slip mesh model are used as discussed by the authors .

43 citations


Journal ArticleDOI
TL;DR: In this paper , the counter-rotating shock wave and wave direction control of a hollow rotating detonation combustor with Laval nozzle were studied using the in-house solver BYRFoam.
Abstract: The counter-rotating shock wave and wave direction control of the hollow rotating detonation combustor with Laval nozzle are studied. The in-house solver BYRFoam, developed on the OpenFOAM platform, is used. The phenomenon and spatial distribution of the counter-rotating shock wave in the combustor are revealed. The result suggests that the closer the location is to the outer wall, the stronger the counter-rotating shock wave is. A method of controlling the wave direction is proposed. It's shown that the intensity of the counter-rotating shock wave is controlled by reducing the total pressure of inlet, and then the direction of the detonation wave is controlled. The process of detonation wave reversing is divided into four steps, namely, counter-rotating shock waves evolve into detonation waves, several detonation waves are extinguished, detonation waves form again, and detonation waves propagate stably. The mechanism of wave direction control is investigated. The result shows that the fluctuation of the total pressure of inlet stimulates the positive feedback interaction between the counter-rotating shock wave and the fresh gas, which causes initial detonation waves to be extinguished and the intensity of counter-rotating shock waves to become stronger and stronger, and eventually counter-rotating shock waves evolve into reverse detonation waves.

36 citations


Journal ArticleDOI
TL;DR: In this paper , the mass load ratio has a significant impact on droplet transport characteristics of gas-liquid two-phase jets, and the equilibrium position of droplet breakup and coalescence is calculated and found to be quite close to the nozzle exit.

34 citations


Journal ArticleDOI
TL;DR: In this paper , a large-eddy simulation was performed on a fully three-dimensional compressible flow via an open-source platform, OpenFOAM, and the fundamental physics of the interaction of the swirling flame, either constructively or destructively, to the acoustic pressure perturbations by examining the local Rayleigh criterion/index.
Abstract: Reducing the footprint of greenhouse gases and nitrogen oxides (NOx) emissions from combustion systems means that they have been operating under lean or ultra-lean fuel–air premixed conditions. Under such conditions, self-excited large-amplitude pulsating thermoacoustic instabilities may occur, characterized by deafening combustion noises and even “violent” structural vibrations, which is, therefore, highly undesirable in practice. By conducting chemical reaction-thermodynamics-acoustics-swirling flow coupling investigations, we have numerically explored the generation and mitigation mechanisms of self-excited pulsating oscillations in a methane-fueled swirling combustor in the presence and absence of an outlet nozzle. Hence, a large-eddy simulation was performed on a fully three-dimensional compressible flow via an open-source platform, OpenFOAM. Furthermore, a thorough assessment was made to understand the fundamental physics of the interaction of the swirling flame, either constructively or destructively, to the acoustic pressure perturbations by examining the local Rayleigh criterion/index. A further explanation was made on implementing the outlet nozzle that can mitigate such periodic pulsating combustion via attenuating the fuel fraction fluctuations, vortices processing, and changing temperature field. It was also found that the dominant pulsating mode is switched from the 1/4 standing-wave wavelength mode to the 3/4 wavelength mode. Finally, more physical insights were obtained by conducting a proper orthogonal decomposition analysis on the energy distribution between the thermoacoustic modes.

28 citations


Journal ArticleDOI
TL;DR: In this article, a spray cooled rack system with a server and simulated heaters, operating with near-ambient temperature coolant of approximately 30°C, was developed for data center cooling application.

27 citations


Journal ArticleDOI
TL;DR: In this article , the authors proposed Taguchi-Grey relation analysis (TGRA) to obtain optimal process factors for deriving better material removal rate and surface finish with lesser taper angle in the machining process.
Abstract: In this present study, an effort is needed to build a decision-making process based on multiple criteria in laser beam drilling process for enhancing machining process measures of Nickel Inconel 718 alloy. The present study proposed Taguchi-Grey Relation Analysis (TGRA) to obtain optimal process factors for deriving better material removal rate and surface finish with lesser taper angle in the machining process. It is an essential to enhance the laser cutting mechanism for obtaining better surface quality measures. Power [laser] (2 KW), the distance of nozzle (0.7 mm), focal-length (+2 mm) and the gas-pressure (3 bar) were selected as optimal factors with accuracy of 4.2%. Gas pressure has the dominant role on the performance measures in LBM owing to its significance of concentrated energy. The surface topography could be obtained with negligible micro cracks on machined specimen under the proposed optimal process factors.

26 citations


Journal ArticleDOI
TL;DR: In this article , a pure food-grade polyvinyl chloride (PVC) with potential biomedical applications is processed and 3D printed using different printing parameters, including velocity, raster angle, nozzle diameter, and layer thickness, and their mechanical properties are investigated in compression, bending, and tension modes.
Abstract: Unmodified polyvinyl chloride (PVC) has low thermal stability and high hardness. Therefore, using plasticizers as well as thermal stabilizers is inevitable, while it causes serious environmental and health issues. In this work, for the first time, pure food-grade PVC with potential biomedical applications is processed and 3D printed. Samples are successfully 3D printed using different printing parameters, including velocity, raster angle, nozzle diameter, and layer thickness, and their mechanical properties are investigated in compression, bending, and tension modes. Scanning electron microscopy is also used to evaluate the bonding and microstructure of the printed layers. Among the mentioned printing parameters, raster angle and printing velocity influence the mechanical properties significantly, whereas the layer thickness and nozzle diameter has a little effect. Images from scanning electron microscopy also reveal that printing velocity greatly affects the final part's quality regarding defective voids and rasters’ bonding. The maximum tensile strength of 88.55 MPa is achieved, which implies the superiority of 3D-printed PVC mechanical properties compared to other commercial filaments. This study opens an avenue to additively manufacture PVC that is the second most-consumed polymer with cost-effective and high-strength features.

26 citations


Journal ArticleDOI
TL;DR: In this paper , a numerical investigation on a rotating detonation combustor with three supersonic guide vane configurations is conducted and compared to a baseline case without any nozzle guide vanes.

25 citations


Journal ArticleDOI
TL;DR: In this paper , a spray cooled rack system with a server and simulated heaters, operating with near-ambient temperature coolant of approximately 30 °C, was developed for data center cooling application.

24 citations


Journal ArticleDOI
TL;DR: Wang et al. as discussed by the authors investigated the influence of nozzle directions and scrapers on properties of 3D printing concrete and found that the vertical extrusion force would reduce buildability, whereas increase the mechanical properties.


Journal ArticleDOI
TL;DR: In this paper , the authors aimed to solve the problem of excessive dust concentration during the tunneling process of continuous mining by using an X-type 2.0-mm nozzle, and the optimal layout was eight nozzles on the upper side of the cutting arm of a continuous miner.

Journal ArticleDOI
TL;DR: In this article , a numerical model and simulation method to describe the condensation of saturated steam discharging into the sub-cooled water in the pipe through the nozzle was established, within the frame of the Euler-Euler two-fluid model, the heat and mass transfer in the phase change of steam is calculated by the thermal phase change model.

Journal ArticleDOI
TL;DR: In this article , a two-way coupling Eulerian-Lagrangian approach is developed to assess the cavitation erosion risk in an axisymmetric nozzle, where the macroscopic cavitation structures are simulated using the large eddy simulation along with the volume of fluid method.
Abstract: In the present study, a two-way coupling Eulerian-Lagrangian approach is developed to assess the cavitation erosion risk in an axisymmetric nozzle. The macroscopic cavitation structures are simulated using the large eddy simulation along with the volume of fluid method. The compressible Rayleigh-Plesset equation and the bubble motion equation are introduced to resolve the microscopic bubble dynamics. The calculated results agree favorably with the experimental data and can capture more flow details, which is associated with the potential erosion risk. Based on the bubble information in multi-scale cavitating flow, a new asymmetric bubble collapse model is proposed to calculate the impact pressure, which is then used to quantitatively assess the cavitation erosion risk in the nozzle. The results show that, compared with the traditional Euler method, the location and value of the potential maximum cavitation erosion risk predicted by this new method are closer to the experimental measurement. The advantages of the newly proposed method are further elaborated systematically. The study found that the high environmental pressure triggered by the collapse of shedding clouds can cause the near-wall bubbles to shrink and even collapse, releasing impulsive pressure, which directly damages the material surface. This phenomenon is considered to be closer to the actual cavitation erosion process. Finally, analyzing the relationship between multi-scale cavitation structures and erosion risk reveals that the high risk of cavitation erosion is mainly due to the oscillation and collapse of near-wall bubbles which are generated near the attached cavity closure line or surrounding the shedding clouds.


Journal ArticleDOI
TL;DR: In this article , the authors conduct a numerical investigation on high-frequency (∼1 kHz) pulsating electrohydrodynamic jet at low electric Bond numbers ( Boe = 0.15-0.7), and demonstrate the influences of electric voltage, nozzle-to-substrate distance (H), and liquid surface tension coefficient (λ) on the dynamic behaviors and durations of the three jetting stages.
Abstract: Electrohydrodynamic jet printing is a highly promising technology for the fabrication of three-dimensional micro/nanoscopic structures, but the advancement of this technology is hindered by the insufficient understanding of many aspects of its mechanisms. Here we conduct a numerical investigation on high-frequency (∼1 kHz) pulsating electrohydrodynamic jet at low electric Bond numbers ( Boe = 0.15–0.7). By analyzing the entire jetting process using the voltage distribution, electric charge density, and flow field obtained from the numerical results, we overcome the limitations of experimental approach and demonstrate the influences of electric voltage ( Φ), nozzle-to-substrate distance ( H), and liquid surface tension coefficient ( γ) on the dynamic behaviors and durations of the three jetting stages: (1) cone formation, (2) jetting, and (3) meniscus oscillation. Furthermore, as a measure of the relative significance of the electric force to the surface tension force, the impacts of Boe on the jetting process are also examined. Results show that some critical aspects of the pulsating jetting process are closely related to Boe: (1) the transitional values of Boe between the four observed jetting regimes on the variations of Φ, H, and γ apply to all three parameters; (2) the nondimensionalized Taylor cone length scales with Boe according to a power law; (3) the jetting processes that have similar Boe collapse onto a universal profile. These new findings of pulsating electrohydrodynamic jet provide a useful supplement to the currently inadequate comprehension of the complicated electrohydrodynamic jet printing process.

Journal ArticleDOI
TL;DR: In this paper , a coal face with a large mining height of 6.5 m was taken as the research object, and factors investigated included spray pressure (P), nozzle retraction distance (L), and nozzle quantity (N).

Journal ArticleDOI
TL;DR: In this paper , a fluid-solid-acoustic multi-physics coupling DPM-LES model is proposed, and numerical simulation results under the multi-field coupling are compared and verified by experiments.

Journal ArticleDOI
TL;DR: In this article , cholesteric hydroxypropyl cellulose (HPC) is combined with in situ photo-crosslinking to produce filaments with an internal helicoidal nanoarchitecture, enabling the direct ink writing of solid, volumetric objects with structural color.
Abstract: Additive manufacturing is becoming increasingly important as a flexible technique for a wide range of products, with applications in the transportation, health, and food sectors. However, to develop additional functionality it is important to simultaneously control structuring across multiple length scales. In 3D printing, this can be achieved by employing inks with intrinsic hierarchical order. Liquid crystalline systems represent such a class of self‐organizing materials; however, to date they are only used to create filaments with nematic alignment along the extrusion direction. In this study, cholesteric hydroxypropyl cellulose (HPC) is combined with in situ photo‐crosslinking to produce filaments with an internal helicoidal nanoarchitecture, enabling the direct ink writing of solid, volumetric objects with structural color. The iridescent color can be tuned across the visible spectrum by exploiting either the lyotropic or thermotropic behavior of HPC during the crosslinking step, allowing objects with different colors to be printed from the same feedstock. Furthermore, by examining the microstructure after extrusion, the role of shear within the nozzle is revealed and a mechanism proposed based on rheological measurements simulating the nozzle extrusion. Finally, by using only a sustainable biopolymer and water, a pathway toward environmentally friendly 3D printing is revealed.

Journal ArticleDOI
01 Feb 2022-Fuel
TL;DR: In this article , a negative pressure jet dust-removal water curtain based on the NPP principle was developed to address coal mine air pollution problem, and the air suction volume of the dust hood was as high as 13.74 m3/min and the proportion of the spray field with a cross-section concentration at the water curtain was more than 104 mg/m3.

Journal ArticleDOI
26 Apr 2022-Polymers
TL;DR: In this paper , the rheological behavior of several 3D-printable, commercially available poly(lactic acid)-based filaments was accurately characterized, from the melt flowability through the printing nozzle, to the interlayer adhesion in the post-deposition stage, evaluating the ability of the considered materials to fulfill the criteria for successful 3D printing using FDM technology.
Abstract: Fused deposition modeling (FDM) is one of the most commonly used commercial technologies of materials extrusion-based additive manufacturing (AM), used for obtaining 3D-printed parts using thermoplastic polymers. Notwithstanding the great variety of applications for FDM-printed objects, the choice of materials suitable for processing using AM technology is still limited, likely due to the lack of rapid screening procedures allowing for an efficient selection of processable polymer-based formulations. In this work, the rheological behavior of several 3D-printable, commercially available poly(lactic acid)-based filaments was accurately characterized. In particular, each step of a typical FDM process was addressed, from the melt flowability through the printing nozzle, to the interlayer adhesion in the post-deposition stage, evaluating the ability of the considered materials to fulfill the criteria for successful 3D printing using FDM technology. Furthermore, the rheological features of the investigated materials were related to their composition and microstructure. Although an exhaustive and accurate evaluation of the 3D printability of thermoplastics must also consider their thermal behavior, the methodology proposed in this work aimed to offer a useful tool for designing thermoplastic-based formulations that are able to ensure an appropriate rheological performance in obtaining 3D-printed parts with the desired geometry and final properties.

Journal ArticleDOI
01 Feb 2022
TL;DR: In this article , the magnetic polarities of microparticles in the resulting structure can be controlled via a permanent magnet structure which is designed and added into the printing system to effectively deliver the magnetic composites ink with a high viscosity, a rotating needle is utilized to induce the microscale Weissenberg effect and help ejecting the polymer solution.
Abstract: Soft magnetic composites have been orderly deposited using an advanced four-dimensional electrohydrodynamic printing process to build deformable actuators that have favorable attributes in fast response, untethered control, and harmless human-machine interactions under low-strength magnetic fields. To effectively deliver the magnetic composites ink with a high viscosity, a rotating needle is utilized to induce the microscale Weissenberg effect (MWE) and help ejecting the polymer solution. The magnetic polarities of microparticles in the resulting structure can be controlled via a permanent magnet structure which is designed and added into the printing system. The main process parameters have been investigated for obtaining optimal options of the motor rotational speed (2000 rpm), electrostatic field strength (2.0 kV), and the ratio (0.732) of the needle diameter to nozzle diameter. Prototype actuators with different magnetization orientations and profiles have been designed and tested, including magnetically powered electrical switches and bionic soft robots to emulate the operations of inchworms and dragonflies. As such, this printing process offers a facile and effective path to fabricate soft magnetic composites toward potential applications.

Journal ArticleDOI
01 Apr 2022-Fuel
TL;DR: In this article , the effect of pre-chamber volume and nozzle opening area on the PCC concept was examined by employing five different prechambers with fixed throat diameter, and it was found that an increased pre- chamber volume promoted earlier ignition in the main chamber, and the throat area was a critical limiting factor in determining the engine performance.

Journal ArticleDOI
TL;DR: In this article , a reliable finite element model (FEM) was developed to predict the functional behavior of the horseshoe sandwich structures in compression analysis and the experimental and simulation results showed that among process parameters, wall thickness, layer height, and nozzle temperature are the most significant parameters to increase the compressive load and, consequently, the energy absorption rate.
Abstract: Abstract Additive manufacturing has provided a unique opportunity to fabricate highly complex structures as well as sandwich structures with various out-of-plane cores. The application of intelligent materials, such as shape memory polymers, gives an additional dimension to the three-dimensional (3D) printing process, known as four-dimensional (4D) printing, so that the deformed structures can return to their initial shape by the influence of an external stimulus like temperature. In this study, 4D printing of smart sandwich structures with the potential of energy absorption is investigated. The samples were fabricated considering various process parameters (i.e. layer height, nozzle temperature, printing velocity, and wall thickness) and tested mechanically. The experimental work reveals that the deformed sandwiches can fully recover their initial form by applying simple heating. Besides, a reliable finite element model (FEM) was developed to predict the functional behavior of the horseshoe sandwich structures in compression analysis. The experimental and simulation results show that among process parameters, wall thickness, layer height, and nozzle temperature are the most significant parameters to increase the compressive load and, consequently, the energy absorption rate. The concept, results, and modeling provided in this study are expected to be used in the design and fabrication of 4D printed sandwich structures for energy absorption applications.

Journal ArticleDOI
TL;DR: In this paper, a numerical study on the effect of the content of impurities in steam on the non-equilibrium condensation phenomenon was carried out in a supersonic nozzle.

Journal ArticleDOI
TL;DR: In this paper , a numerical study on the effect of the content of impurities in steam on the non-equilibrium condensation phenomenon was carried out in a supersonic nozzle.

Journal ArticleDOI
TL;DR: In this article , the Lagrangian-based Particle Finite Element Method (PFEM) and Bingham constitutive model were used to obtain a deeper understanding of flow processes and forces developing in the vicinity of the extrusion nozzle.


Journal ArticleDOI
TL;DR: In this article , a step-by-step laboratory procedure was used to identify the optimal configuration of a tower-shaped trailed sprayer intended for application in vertical shoot trellised vineyards.