Smaller Nozzle Diameter Research Articles

An alternative filament fabrication method as the basis for 3D-printing personalized implants from elastic ethylene vinyl acetate copolymer

In this work, a novel tool for small-scale filament production is presented. Unlike traditional methods such as hot melt extrusion (HME), the device (i) allows filament manufacturing from small material amounts as low as three grams, (ii) ensures high diameter stability almost independent of the viscoelastic behavior of the polymer melt, and (iii) enables processing of materials with rheological profiles specifically tailored toward fused filament fabrication (FFF). Hence, novel materials, previously difficult to process due to HME limitations, become easily accessible for FFF for the first time. Here, we showcase the production of highly flexible drug-free, and drug-loaded filaments based on ethylene-vinyl acetate polymers with a vinyl acetate content of 28 w% (EVA28) and unprecedented high melt flow rates of up to 400 g/10 min. Owing to their low viscosity, FFF with low print nozzle sizes of 250 μm was achieved for the first time for EVA28. These small nozzle diameters facilitate 3D-printing of high-resolution structures in small-dimensional dosage forms such as subcutaneous implantable drug delivery systems, which can later be used for personalization. Consequently, the material portfolio for FFF is tremendously broadened, allowing material and formulation optimization toward FFF, independent of a preliminary extrusion process.

Development of diesel combustion with low cooling loss and high dispersion spray using two-dimensional optical measurements

In this study, a novel, high-efficiency, and clean combustion concept utilizing low cooling loss and high dispersion spray is proposed. The research aims to validate the objectives of this concept through spatiotemporal analysis of phenomena when key variables such as combustion chamber shape, spray parameters, and swirl are modified. This new combustion approach focuses on achieving low heat loss by using smaller nozzle diameters, multi-hole nozzles, and reduced swirl compared to conventional combustion. The combustion chamber is designed with an increased cavity diameter and an expanded taper diameter to enhance upward spray dispersion, thereby reducing fuel spray penetration into the cavity and decreasing cooling loss. This configuration reduces the fuel spray penetration in cavity, achieving a reduction in cooling heat loss. Furthermore, to increase the volume in the lower part of the combustion chamber, a corner-bottom shape is employed. Additionally, by causing spray impingement through the corner bottom shape, the strategy aimed to prevent the return of the mail injections to the central part of the combustion chamber. These parameters were evaluated using two-dimensional optical measurements, which calculated thermal flux, temperature, velocity, and KL value distributions. The impact of cavity diameter on internal cooling loss is significant, and preventing flame stagnation from a smoke perspective is crucial. An increase in taper diameter reduces squish velocity, achieving heat losses reduction, while necessitating spray dispersion into the squish area. The influence of swirl ratio on heat losses is more pronounced in the squish and taper areas than inside the cavity, necessitating consideration of flame temperature reduction within the cavity when reducing swirl ratios. The implementation of double after injection influences low heat losses and avoids flame stagnation, enabling soot reduction. The corner bottom shape combustion chamber proved effective in reducing heat losses and particulate matter (PM) at medium and high loads.

Influence of Passive Pre-Chamber Nozzle Diameter on Jet Ignition in a Constant-Volume Optical Engine under Varying Load and Dilution Conditions

<div>Despite the growing prominence of electrified vehicles, internal combustion engines remain essential in future transportation. This study delves into passive pre-chamber jet ignition, a leading-edge combustion technology, offering a comprehensive visualization of its operation under varying load and dilution conditions in light-duty GDI engines. Our primary objectives are to gain fundamental insights into passive pre-chamber jet ignition and subsequent main combustion processes and evaluate their response to different load and dilution conditions. We conducted experimental investigations using a light-duty, optical, single-cylinder engine equipped with three passive pre-chamber designs featuring varying nozzle diameters. Optical diagnostic imaging and heat release analysis provided critical insights. Findings reveal that as load decreases, fuel availability and flow conditions deteriorate, leading to delayed and suboptimal jet characteristics impacting main chamber ignition and combustion. Notably, at high and medium loads without dilution, the 1.2 mm-PC (smallest nozzle diameter) excels, exhibiting superior jet ignition and main combustion. This is attributed to earlier jet ejection, improved penetration, and intensified jets, all enabled by the smaller nozzle diameter. Conversely, under low load conditions, the 1.6 mm-PC (largest nozzle diameter) performs better due to enhanced scavenging and reduced pre-chamber residuals, resulting in more balanced pre-chamber combustion and jet characteristics. Furthermore, nozzle diameter significantly influences cycle-to-cycle variations, with smaller diameters enhancing jet ignition but intensifying variability. The impact of external residuals (dilution) on jet ignition performance varies with nozzle diameter, with the 1.6 mm-PC displaying less degradation and demonstrating earlier jet ejection and CA50 timing under higher dilution conditions. In summary, this research underscores the importance of scavenging and residual levels in pre-chamber design, influencing dilution tolerance, and extending possibilities for high-efficiency engines. It contributes essential insights into the behavior of passive pre-chamber jet ignition systems, facilitating their optimization for future internal combustion engines.</div>

Shotcrete 3D Printing ‐ Interaction of nozzle geometry, homogeneity and hardened concrete properties

AbstractShotcrete 3D Printing (SC3DP) applies concrete layer by layer using a wet‐spray process. The resulting hardened concrete properties of the applied SC3DP layers (e.g. height, width or mechanical strength) are largely dependent on the selected material and process parameters. In this context, the nozzle geometry is an important influencing parameter. During printing, the velocity of the shotcrete jet is significantly influenced by the nozzle outlet diameter. Therefore, in the present study, the effect of the nozzle outlet diameter (15 ‐ 30 mm) is investigated with regard to the resulting layer homogeneity, i.e. local density and aggregate distribution in the cross‐section, and hardened concrete properties, i.e. flexural strength. By analysing the manufactured specimens, an uneven distribution of the aggregate is observed horizontally across the cross‐section of the layers. An accumulation of aggregate is present in the core of the layer resulting in a cement paste‐rich region in the edge areas. This leads to increased local densities in the core of the specimen. The application of the concrete with small nozzle outlet diameters results in the highest local densities and the highest flexural strength.

Simulating droplet distribution characteristics for sprinkler irrigation with a modified ballistic model

The ballistic model, with its high computational efficiency and small test workload, is an effective method to simulate the distribution of spray droplets. It can be employed to solve the problems of oversimplifying the droplet crushing process and motion shape and ignoring the droplet energy characteristics in the equivalent droplet indicator in the existing model assumptions. Based on the law of the motion of sprinkler irrigation water flow, the model assumption of continuous motion and segmental fragmentation of the jet is proposed in the current study. Ellipsoidal droplet shape parameters were introduced to construct the equations of the motion of sprinkler irrigation water flow in the jet and droplet stages, respectively. The critical conditions for large droplet separation and correction drag coefficient for small droplets are defined and solved, and the calculation formulas based on the energy-weighted equivalent droplet indicators were derived. The accuracy of the model was verified using 50PYC, ZY-2, and HY50 nozzles, and the modified model was compared with Fukui’s and Li’s models. The effects of working pressure, nozzle diameter, nozzle elevation angle, and installation height on the droplet landing distance, velocity, and angle at the end of the spray range were investigated. The results showed that: (1) The mean absolute error (MAE) and root-mean-square error (RMSE) of droplet landing distance, velocity, and angle under different working conditions simulated by the modified model were smaller than those obtained using Fukui’s and Li’s models, showing better simulation accuracy. Considering the simulated values of droplet landing distance, velocity, and angle of the 50 PYC nozzle (nozzle diameter of 22 mm and working pressure of 0.35 MPa) as an example, the accuracy of the modified model was improved by 72.86 % and 53.45 % (landing distance), 35.86 % and 70.57 % (landing velocity), 42.10 % and 67.66 % (landing angle) compared with the Fukui’s and the Li’s models, respectively. (2) Fukui’s and Li’s models demonstrate higher accuracy in simulating the droplet landing distance of the ZY-2 nozzle with a smaller nozzle diameter (7 mm) than in simulating the HY50 and 50PYC nozzles; (3) The changes in nozzle operating pressure, nozzle diameter, and nozzle elevation angle exert the greatest effect on the droplet landing distance, landing velocity, and landing angle, respectively. This study provides a novel idea for using the ballistic model to simulate the spray droplet distribution.

Response surface methodology-based multi-nozzle optimization for electrospray cooling

The performance of electronic systems has decreased due to an increase in heat flux density. New methods such as electrospray cooling are promising to ensure that these systems operate under desired conditions. In electrospray cooling, the working flow rate is limited because the small nozzle diameter is preferred to improve the electric field strength and heat transfer performance. However, it is known that increasing the fluid flow rate is a good method to improve heat transfer. For this reason, multi-nozzles should be used to remove more heat from the surface with electrospray cooling. For the first time in the literature, multi-nozzles were optimized for electrospray cooling with the optimization method in the study conducted for this purpose. Nozzle optimization studies were carried out for ethanol–water mixture used as a fluid for the first time in the literature, nozzle diameter, distance between nozzles, and nozzles number. In the experimental study, it was determined that the fluid composition ratio was effective on electrospray cooling and the effects of nozzle geometry parameters (nozzle diameter, distance between nozzles, nozzle number) were limited. As a result of the optimization process based on the response surface methodology, the highest heat transfer coefficient was obtained for the 5 mm nozzle-center distance where 3 pieces of 26G nozzles.

Optical experiment study on Ammonia/Methanol mixture combustion performance induced by methanol jet ignition in a constant volume combustion bomb

Ammonia as an alternative fuel has shown great potential in reducing carbon dioxide emissions. However, the issues of high ignition temperature and unstable combustion of ammonia limit its extensive application. As an ignition energy enhanced method, the ignition chamber (pre-chamber) seems to be an effective solution to improve the combustion performance and extend the ammonia lean flammability limit. In this study, the methanol was provided as relatively high activity fuel to improve the mixture activity in the ignition chamber and main chamber. The mixture activity control method was introduced to accelerate ammonia premixed combustion. The visualization experiment compounded with shadow method was applied to investigate. Results showed that the methanol fueled ignition chamber as jet ignition model reduced the combustion duration by almost half compared to spark ignition method. The methanol jet flame propagation formatted multiple zones of ignition and combustion in the main chamber. The ammonia combustion speed shifted from being determined by laminar flame propagation speed to being determined by jet velocity. The methanol jet velocity is related to the methanol energy substitution ratio and nozzle diameter of the ignition chamber. A 2 % methanol energy substitution ratio is optimized for the lean condition of Φ = 0.8 compared to 1 % methanol energy substitution ratio achieve for the condition Φ = 1.0 in the main chamber. When 50 % methanol (energy) was added in the main chamber, the activity thermo-atmosphere improvement induced the combustion duration to decrease by 43.8 % and 51.9 % at equivalent ratios of 1.0 and 0.8, respectively, compared to pure ammonia. The small nozzle diameter of ignition chamber can improve the jet velocity, however it caused the methanol combustion flame quenching leading to unstable combustion phenomenon. A 3 mm nozzle diameter achieved a short combustion duration compared to 4.5 mm and 6 mm nozzle diameter.

Three-dimensional numerical simulation of the interaction between high-pressure sub-cooled water jet impacting high-temperature liquid lead-bismuth metal

The rupture accident of the steam generator heat transfer tube of the lead-bismuth cooled fast reactor causes a high-pressure sub-cooled water jet impacting high-temperature liquid lead-bismuth, and the interaction mechanism between water and liquid lead-bismuth needs to be studied clearly. In this paper, based on the volume of fluid method, the LES turbulence model and the Lee phase transition model, a three-dimensional numerical model is developed to study the multiphase flow and heat transfer mechanism of water and lead-bismuth interaction. The effects of sub-cooled water temperature, inlet pressure, and nozzle diameter on the distribution of phase state, pressure, temperature, and generated steam volume are studied in detail. The results indicate that the water jet can be divided into the jet water zone, the water-steam mixed zone, and the multiphase flow zone, respectively. Among them, the appearance of water-steam mixed zone depends on the internal boiling of the jet, and this zone tends to appear under the condition of low inlet pressure, small nozzle diameter and high sub-cooled water temperature. For multiphase flow zone, the temperature increases with sub-cooled water temperature, decreases with nozzle diameter and is almost not influenced by inlet pressure; The pressure increases with sub-cooled water temperature, inlet pressure and nozzle diameter. When nozzle diameter is large enough, however, it no longer has any effect on the temperature and pressure distribution within the jet. The volume of steam generated by water boiling is positively correlated with all three factors. Overall, the steam migrates upward through the outer side of the jet, absorbing heat and expanding during the migration process, and forming a high-temperature area at the top of the jet.

Schlieren and mie-scattering visualization of an evaporating spray under marine diesel engine conditions

Due to the critical influence on combustion, extensive research has been carried out to deepen the understanding of diesel spray evolution. However, for the greater share of land-based diesel engines, most of the studies have focused on the injectors with small nozzle diameter and rare studies can be found on marine diesel engines, which has a larger mass flow rate and longer injection duration with large nozzle diameter. In this study, the influence of injection pressure, ambient temperature, ambient density and nozzle diameter on spray morphology for medium speed marine diesel engine injectors (with nozzle diameter up to 0.53 mm) were investigated under various non-reacting but evaporative conditions. The experiments were performed via a highly enhanced constant volume chamber (highest temperature of 900 K and highest pressure of 8 MPa) with an optical window diameter of 205 mm. Liquid and vapor penetration of sprays were recorded by Mie-scattering and schlieren optical configurations respectively. Results show that the vapor penetration velocity is mainly affected by injection pressure. Ambient temperature has the most significant effect on liquid penetration length, but less effect can be found on the vapor penetration velocity. Given the obvious deviation from heavy duty engine sprays, the empirical correlations for liquid penetration length and vapor spray evolution are updated to fit the spray characteristics of medium speed marine diesel engine injectors, which is helpful to understand the spray behavior for large nozzle diameter injector under marine diesel engine conditions.

Influence of nozzle structure on the combustion performance of a graphitic hydrogen-chlorine synthesis combustor

The growing semiconductor sector is driving up demand for high-purity gas-phase HCl. Large combustion zones and low HCl concentrations are problems for HCl manufacturing systems. Based on the realizable k-ε model, the eddy breakup combustion model, and the participating media radiation model, the computational fluid dynamics simulation was used as the primary means in this study. The influence of four structural factors, nozzle jet hole diameter, jet angle, and opening angle—another is nozzle mounting height, on the combustion effect of the synthesis combustor was investigated. The extent of the high-temperature zone in the synthesis combustor and the purity of the hydrogen chlorine at the outlet were used as the main evaluation criteria. The results of numerical simulations demonstrate that the better the gas mixing and combustion in the combustor, the lower the nozzle mounting height should be. Small nozzle diameters and large nozzle jet angle increase gas flow velocity in the recirculation zone close to the inner wall of the combustor. Additionally, the recirculation zone will appear in the combustor as a result of the nozzle's presence. The area of the high-temperature zone within the combustor decreases as internal gas velocity increases. On the other hand, the recirculation gas flow is not significantly impacted by the angle at the condition that the jet holes open. The results of the investigation provide a reference for the design of the miniaturization of the combustor in the non-premixed combustion synthesis of gases process.

Modeling of argon–steam thermal plasma flow for abatement of fluorinated compounds

This study presents a numerical model of the hybrid-stabilized argon–steam thermal DC plasma torch of a new design for generating an argon–steam plasma suitable for efficient abatement of persistent perfluorinated compounds. The model includes the discharge region and the plasma jet flowing to the surrounding steam atmosphere contained in a plasma-chemical chamber. Compared to previous studies, the torch had a smaller nozzle diameter (5.3 mm) and a reduced input power (20–40 kW) and arc current (120–220 A). The outlet region for the plasma jet extends to 20 cm downstream of the exit nozzle. Fluid dynamic and thermal characteristics together with diffusion of argon, hydrogen and oxygen species, and distribution of plasma species in the discharge and the plasma jet are obtained for currents from 120 to 220 A. The results of the calculations show that the plasma jet exhibits high spatiotemporal fluctuations in the shear layer between the plasma jet and colder steam atmosphere. The most abundant species in the plasma jet are hydrogen and oxygen atoms near the jet center, and molecules of H2, O2 and OH in colder surrounding regions. Satisfactory agreement is obtained with measurements of the radial temperature and electron number density profiles near the jet center close to the nozzle exit.

Experimental Investigation of a Cylindrical Air-Breathing Continuous Rotating Detonation Engine with Different Nozzle Throat Diameters

A continuous detonation engine with various exhaust nozzles, analogous to typical scramjet cavity combustors with variable rear-wall heights, was adopted to perform a succession of cylindrical air-breathing continuous rotating detonation experiments fueled by a non-premixed ethylene/air mixture. The results show that the detonation combustion was observed to self-sustain in the combustor through simultaneous high-speed imaging covering the combustor and isolator. A long test, lasting more than three seconds, was performed in this unique configuration, indicating that the cylindrical isolator–combustor engine exhibits potential for practical applications. Three distinct combustion modes were revealed with varied equivalent ratios (hybrid mode, sawtooth wave mode, and deflagration mode). The diameter of the nozzle throat was critical in the formation of rotating detonation waves. When the nozzle throat diameter was larger than the specific value, the detonation wave could not form and self-sustain. The upstream boundary of the shock train was supposed to be close to the isolator entrance in conditions of a high equivalence ratio and small nozzle throat diameter. In addition, it was verified that periodic high-frequency pressure oscillation could cause substantial impacts on the incoming flow as compared with the steady deflagration with the same combustor pressure.

Rapid fiber alignment quantification in direct write printing of short fiber reinforced composites

Short fiber reinforced polymer composites fabricated by direct ink writing (DW) have design flexibility, low cost, and tailored property advantages over traditional composite materials. Controlling fiber alignment in these composite systems can be used to design unique materials with direction-dependent properties, especially when coupled to topology optimization for light weighting and high strength. . This study focuses on controlling fiber alignment in short carbon fiber composites with two printing parameters common in DW systems: nozzle diameter and velocity ratio. To do so, a novel rapid fiber alignment analysis (RFAA) was developed to quickly collect large amounts of fiber alignment data. Compared to the conventional fiber alignment quantification technique, X-Ray CT, RFAA is a rapid, accurate, and low-cost alternative. It was determined that fiber alignment can be enhanced by printing with smaller nozzle diameters and higher velocity ratios. Longitudinal bending stiffness and bending strength improved as the fiber alignment increased. Composites printed with low fiber alignment exhibited isotropic mechanical properties. However, aligning the fibers in the composite resulted in direction-dependent properties with significantly enhanced modulus and strength in the alignment direction.

Experimental study on the scale-up of a multi-ring inclined nozzle spout-fluid bed by electrical capacitance tomography

Abstract Scale-up studies of fluidized beds are important for numerous fields. Fluidization in a multi-ring inclined nozzle spout-fluid bed (MRIN spout-fluid bed) is one of the most critical factors that affect the coating efficiency and uniformity of tri-structural isotropic (TRISO) nuclear particles in the fluidized bed chemical vapor deposition (FB-CVD) process. In this work, the flow pattern similarity principle was proposed to scale up a specially designed spout-fluid bed, which was aimed at maintaining the gas-solid contact efficiency, and was validated by electrical capacitance tomography (ECT) measurements. First, the traditional ECT method was developed for the specially designed MRIN spout-fluid bed according to the filling method. Then, the reconstruction algorithms were updated using the alternating direction multiplier method (ADMM) by introducing optimization constraints. The fluidization laws were investigated for different superficial gas velocities and distributor structures. We found that the gas distributor structure affected the merge point of the jets, which played an essential role in fluidization pattern changes. The statistically-based coefficient of variation (Cv) was proposed to distinguish the different flow patterns. Multi-ring spouting was then selected as a typical flow pattern for good fluidization and mixing, where the Cv ranged from 0.25 to 0.65. Then, the optimal design principles for the enlarged spout-fluid bed gas distributor were obtained. We determined that a smaller nozzle diameter (0.71d 0), larger nozzle spacing (1.12x 0), and slightly inclined angle (1.50θ 0) could improve fluidization, and that nozzle spacing was the most important factor. This study may be beneficial for the industrial design of the FB-CVD process and for the fabrication of high-density nuclear fuel particles. Additionally, it could be presented to a more general audience for scaling-up fluidized beds with a complex distributor, which would be beneficial for the fluidization research community.

Experimental investigations of aviation kerosene spray in different ambient conditions with various nozzle diameters and injection pressures

The purpose of this study is to explore the spray characteristics of aviation kerosene (RP-3) under sub/trans/supercritical conditions and provide a reference for engine test research under advanced combustion mode. The experiment is carried out in a constant volume chamber. To understand the influence of nozzle diameter and injection pressure on spray characteristics of RP-3 under different critical conditions, 270 groups of spray images are collected under three nozzle diameters (100, 300, 450 μm), five injection pressures (60, 80, 100, 120, 140 MPa), and nine critical conditions. The macroscopic parameters are calculated and new empirical correlations are generated to investigate the axial and radial development of spray. The results show that kerosene spray has different spray characteristics under sub/trans/supercritical conditions. The effect of nozzle diameter on kerosene spray is stronger than that of diesel spray. The spray with a small nozzle diameter is easily affected by gas entrainment. The injection pressure has an insignificant effect on spray macroscopic characteristics, but high injection pressure is conducive to increasing the vapor phase ratio and promoting oil-gas mixing, especially under supercritical conditions. The new correlations have good agreement with kerosene experimental results.

Examination of SWMC applying method by spray coating method for PEFC

A popularization of Polymer Electrolyte Fuel Cell (PEFC) is necessary to realize ahydorgensociety. However, the manufacturing cost is still expensive, and it is required to reduce the manufacturing cost for further spread. In our laboratory, we have been developing 3D catalyst layers using ink-jet printers (IJP) and self-water management catalyst layers (SWMC) by adding carbon grains in order to reduce the amount of platinum catalysts used while maintaining the power generation performance. The IJP method can form a catalyst layer with a three-dimensional structure, but its disadvantage is that it cannot coat our proposed SWMC, due to the long coating time and small nozzle diameter. Therefore, in this study, we investigated the possibility of producing SWMC by the spray coating method in order to shorten the coating time and enable the application of carbon additives. As a result, Although it was confirmed that the spray coating method was able to disperse and apply the added carbon grains, the polarization resistance was worse than that of the IJP method. The polarization resistance of the catalyst layer with spherical graphite was hardly different with that of the standard catalyst layer, consequently it was confirmed its effectivness. On the other hand, graphite rubbish increased polarization resistance drastically by damaging the polymer membrane during the spray application process, inducing cross leakage.

Plume Stability During Direct Contact Condensation of Steam in a Crossflow of Subcooled Water, at High Mass Flux and With a Small Nozzle Diameter

Abstract The stability of a steam plume during direct-contact condensation into a crossflow of subcooled water is investigated for mass fluxes that are higher (>600 kg/m2s) and a nozzle diameter (2.4 mm) that is smaller than typically seen in the literature. The transition from a stable steam plume to an unstable plume associated with the formation and collapse of steam bubbles is characterized by high-speed imaging and high-frequency pressure measurements. Four regimes are observed: stable, condensation oscillation, transition, and unstable. A regime map and spectral signatures of the different flow regimes are provided. Results are compared with correlations from the literature, which are typically derived for lower mass fluxes, larger nozzles, and injection into stagnant pools of water.

Effect of nozzle diameter on mechanical and geometric performance of 3D printed carbon fibre-reinforced composites manufactured by fused filament fabrication

PurposeFused filament fabrication (FFF) is one of the most popular additive manufacturing (AM) technologies due to its ability to build thermoplastic parts with complex geometries at low cost. The FFF technique has been mainly used for rapid prototyping owing to the poor mechanical and geometrical properties of pure thermoplastic parts. However, both the development of new fibre-reinforced filaments with improved mechanical properties, and more accurate composite 3D printers have broadened the scope of FFF applications to functional components. FFF is a complex process with a large number of parameters influencing product quality and mechanical properties, and the effects of the combined parameters are usually difficult to evaluate. An array of parameter combinations has been analysed for improving the mechanical performance of thermoplastic parts such as layer thickness, build orientation, raster angle, raster width, air gap, infill density and pattern, fibre volume fraction, fibre layer location, fibre orientation and feed rate. This study aims to assess the effects of nozzle diameter on the mechanical performance and the geometric properties of 3D printed short carbon fibre-reinforced composites processed by the FFF technique.Design methodology approachTensile and three-point bending tests were performed to characterise the mechanical response of the 3D printed composite samples. The dimensional accuracy, the flatness error and surface roughness of the printed specimens were also evaluated. Moreover, manufacturing costs, which are related to printing time, were evaluated. Finally, scanning electron microscopy images of the printed samples were analysed to estimate the porosity as a function of the nozzle diameter and to justify the effect of nozzle diameter on dimensional accuracy and surface roughness.FindingsThe effect of nozzle diameter on the mechanical and geometric quality of 3D printed composite samples was significant. In addition, large nozzle diameters tended to increase mechanical performance and enhance surface roughness, with a reduction in manufacturing costs. In contrast, 3D printed composite samples with small nozzle diameter exhibited higher geometric accuracy. However, the effect of nozzle diameter on the flatness error and surface roughness was of slight significance. Finally, some print guidelines are included.Originality valueThe effect of nozzle diameter, which is directly related to product quality and manufacturing costs, has not been extensively studied. The presented study provides more information regarding the dependence of the mechanical, microstructural and geometric properties of short carbon fibre-reinforced nylon composite components on nozzle diameter.

3D Printing of Supramolecular Polymer Hydrogels with Hierarchical Structure.

Liquid crystalline hydrogels are an attractive class of soft materials to direct charge transport, mechanical actuation, and cell migration. When such systems contain supramolecular polymers, it is possible in principle to easily shear align nanoscale structures and create bulk anisotropic properties. However, reproducibly fabricating and patterning aligned supramolecular domains in 3D hydrogels remains a challenge using conventional fabrication techniques. Here, a method is reported for 3D printing of ionically crosslinked liquid crystalline hydrogels from aqueous supramolecular polymer inks. Using a combination of experimental techniques and molecular dynamics simulations, it is found that pH and salt concentration govern intermolecular interactions among the self-assembled structures where lower charge densities on the supramolecular polymers and higher charge screening from the electrolyte result in higher viscosity inks. Enhanced hierarchical interactions among assemblies in high viscosity inks increase the printability and ultimately lead to greater nanoscale alignment in extruded macroscopic filaments when using small nozzle diameters and fast print speeds. The use of this approach is demonstrated to create materials with anisotropic ionic and electronic charge transport as well as scaffolds that trigger the macroscopic alignment of cells due to the synergy of supramolecular self-assembly and additive manufacturing.

Breakup characteristics of high speed liquid jets from a single-hole injector

In this study, spray characteristics from a single-hole gasoline direct injection injector with nozzle diameters of 0.14 mm and 0.2 mm were investigated. High-speed macroscopic and microscopic imaging techniques were applied to record the overall spray structure and the initial fuel spray behavior. The injection pressure ranged from 50 bar to 350 bar, and the ambient pressure was kept constant at 1 bar. Several semi-empirical models for predicting spray penetration at non-evaporating conditions were investigated, including models by Dent, Hiroyasu and Arai, and Naber and Siebers. Results showed that the Naber and Siebers equation demonstrated the best match with the experimental data. Both the initial and global spray penetration were well predicted. The spray penetration can be divided into two regions based on the relationship between spray penetration and injection time, namely the regions before and after breakup, and the transitional point was defined as the breakup point. Higher fuel pressures resulted in shorter breakup time and length for the injector with the smaller nozzle diameter, and the injector with larger nozzle diameter produced shorter breakup time and longer breakup length. A linear relationship was identified between the initial spray penetration and injection time at all fuel pressures, which indicates the initial spray tip velocity can be treated as constant at each fuel pressure. The ratio between the slope of experimental initial spray penetration and average flow velocity (based on static flow rate measurements) was around 0.9 at all fuel pressures for the injector with 0.14 mm nozzle diameter. Consequently, the average flow velocity obtained based on the static flow rate at each fuel pressure can be used to accurately predict the initial jet velocity.