Larger Nozzle Diameter Research Articles

Experimental study on ignition and flame propagation of premixed ammonia ignited by Direct-Injected diesel in an optical rapid compression Machine

Ammonia (NH3) is considered as one of the most promising zero-carbon fuels for internal combustion engines. Based on diesel engine modification, The ammonia/diesel dual-fuel mode with port injection of ammonia and in-cylinder direct injection of diesel has been proven to be the most feasible strategy. In this paper, the effects of ignition and flame propagation of premixed ammonia ignited by direct-injected diesel were studied based on an optical rapid compression machine (RCM). The results show that the spray and distribution of diesel play the key role in the ignition and flame propagation of NH3/diesel dual fuels combustion. For total excess air ratio (λT) of 1.0, the ignition delay of NH3/diesel with high energy ratio of ammonia (ER of 95 %) was much shorter than ER of 66 % which was mainly due to the low injection pressure of diesel. Under the same injection pressure, with the large nozzle diameter of diesel injector of 0.28 mm, the ignition delay of NH3/diesel will be shortened significantly. When the ER is low, the combustion process presents the characteristics similar to the multi-point compression combustion. When the ER rises to 83 %, the combustion process is mainly dominated by NH3 premixed combustion, and diesel mainly plays the role of ignition. Reducing the background pressure and temperature to 4 MPa and 887 K, respectively, NH3 is not able to be ignited by diesel.

Effects of nozzle diameter on marine fuel injection and deflagration performance

The marine fuel injection and deflagration performance with different nozzle diameters in large compartments are researched in this work. The results show that marine fuel could quickly form a stable fuel spray field. Increasing nozzle diameter dramatically enhances the fuel spray concentration and aggravates the fuel spray deflagration degree, resulting in rapid increases in flame propagation speed, deflagration overpressure, and deflagration temperature. A larger nozzle diameter causes the deflagration flame to propagate further forward. With the increase of deflagration time, the flame propagation speed shows a trend of first rising and then decreasing, with fluctuations. When the nozzle diameter is small, the overpressure declines toward the back. In the case of large nozzles (≥0.8 mm), the overpressure distribution in the compartment fluctuates greatly, with a tendency to increase first and then decrease. Furthermore, deflagration peak overpressure ascends linearly with the logarithm of fuel spray concentration. The peak deflagration overpressure is 1.875 MPa with 1.0 mm nozzle diameter. The deflagration temperature is highest at the center of the deflagration. The research results can guide the assessment and prevention of fire and deflagration accidents on ships.

Study on Spray Characteristics and 0-D Model of Marine Injector with Large Orifice Diameter

ABSTRACT Low carbon, cleanliness and efficiency are the three key challenges facing the development of diesel engines. Biodiesel is a crucial step in the transition from fossil fuels to zero-carbon fuels. This study was carried out to investigate the effects of injection pressure and ambient pressure on the biodiesel spray characteristics of a marine large orifice diameter injector. Injection mass has a nonlinear relationship with short injection duration and a linear relationship with long injection duration. Increasing the injection pressure shortens the nonlinear stage and enhances the linear effect. When the injection pressure is increased from 35 MPa to 140 MPa, the injection delay is shortened by 10% (2.5 ms), and the diameter nozzle has almost unaffected on the injection delay. The Arai model was revised based on experimental data to improve its prediction effect on sprays with large nozzle diameters. The new model considers the effects of fuel density and ambient density on penetration before and after breakup, respectively. The penetration of the new model is still proportional to time of after start of injection (t) before the breakup and proportional to t0.6 after the breakup. Increasing the ambient pressure enhances the influence of injection conditions on dimensionless penetration. Compared with the Arai model, the new model reduces the sensitivity of the dimensionless penetration to the injection pressure. Research on biodiesel spray and spray models under large nozzle diameter conditions will be of great help to the application of low-carbon and clean fuels in marine diesel engines.

Numerical simulation of jet boiling characteristics of high-pressure water injected into high-temperature liquid lead–bismuth in a confined space

The steam generator heat transfer tube rupture (SGTR) accident is potentially devastating and is one of the most serious design basis accidents for lead–bismuth cooled fast reactor (LFR). It is important to study the mechanism of water jet injecting into liquid lead–bismuth eutectic (LBE) for the safety analysis of SGTR accidents. In this paper, based on the volume of fluid (VOF) model, the large eddy simulation (LES) turbulence model and the Lee phase transition model, a three-dimensional numerical model is developed to investigate the typical characteristics of a high-pressure sub-cooled water jet injecting into high-temperature LBE in a confined space. The study focuses on examining the impact of water temperature, inlet pressure, and nozzle diameter on jet development and its surroundings, including the cover gas layer and LBE phase. The results indicate that the central region of the jet is primarily subject to flash boiling, particularly at the nozzle position, whereas the jet interface undergoes heat-transfer boiling. The residual liquid phase migrates upward along the interface and gradually boils. Based on the phase distribution characteristics, a typical jet can be categorized into four zones: the water-steam transition zone, the multiphase flow zone, the end water phase zone, and the steam block zone. Under the conditions analyzed in this paper (water temperature 140–260 °C, injection pressure 2–10 MPa, nozzle diameter 2–10 mm, LBE temperature 400 °C), the jet volume expands approximately exponentially, correlating positively with the three factors studied. It is also found that at high injection pressures and large nozzle diameters, the steam at the top of the jet is prone to destabilization and fragmentation, with steam volume and pressure oscillations being the dominant factors. Steam migration triggers pressure oscillations in the LBE region, and the intensity of these oscillations is closely linked to the migration rate. Under the conditions studied, the maximum pressure oscillation reached 5.5 times the initial pressure. The expansion of the jet steam drives the pressurization of the cover gas layer, which correlates positively with all three factors studied. The nozzle diameter has the greatest effect, increasing the maximum pressure by 168 % from the initial pressure.

Fatigue response of multiscale extrusion-based additively manufactured acrylonitrile butadiene styrene-graphene nanoplatelets composites

This study investigates the effect of varying concentrations of graphene nanoplatelets (GNPs) on the mechanical and fatigue characteristics of acrylonitrile butadiene styrene (ABS)/GNPs nanocomposites, both in filament form and as 3D-printed parts with different raster orientations. Quasi-static and cyclic loading tests were performed on specimens containing 0.1 wt%, 0.5 wt%, 1.0 wt%, and 2.0 wt% GNPs. The results indicated that the addition of 0.1 wt% GNPs to the ABS polymer matrix increased the ultimate tensile strength (UTS) of the filament by 18 %. Addition of 1.0 wt% and 2.0 wt% GNPs to the matrix improved the Young's modulus of the filament by up to about 35 % but did not enhance the UTS. The filament containing 0.5 wt% GNPs demonstrated the highest fatigue life, even higher than that of the standard samples fabricated through injection molding technique. This was due to its high static strength, Young's modulus, and ductility. However, when the ABS/GNPs nanocomposites were 3D-printed, the addition of GNPs had no major impact on their fatigue life, especially in the higher load levels. Inadequate adhesion and reduced interlayer bonding strength resulted in a detrimental impact on fatigue life of 3D-printed objects. The extrudate-swell phenomenon seems to significantly affect this reduction in fatigue life. To address this, larger nozzle diameter (0.6 mm) was used in fabricating 3D-printed samples. Results indicated that samples with less distortion and smaller extrudate-swell had higher fatigue life. It highlights the importance of considering GNP concentration and printing parameters for optimal fatigue properties in ABS/GNPs composites.

INVESTIGATION OF RP-3 SPRAY CHARACTERISTICS BASED ON SENSITIVITY ANALYSIS AND ACTIVE SUBSPACE CONSTRUCTION

To explore the in-cylinder fuel injection and the subsequent spray dynamics of aviation fuel RP-3, the RP-3 spray macroscopic characteristics of single-hole injectors with different nozzle diameter under varied ambient pressures and injection pressures are investigated via diffuser back-illumination imaging (DBI) experimental method. The critical factors of the variability in spray characteristics response are pointed out by setting up a one-dimensional active subspace in this study, to perform synergistic effects via multivariable sensitivity analysis. It is revealed that compared with diesel, RP-3 spray edge shows more vortex structures, which is more susceptible to gas entrainment, especially for injector with larger nozzle diameter. Increasing injection pressure and ambient pressure will lead reduced vortex structures instead. Moreover, on the whole, RP-3 produces shorter spray penetration distances, larger spray cone angle, lower spray irregularity, and smaller spray areas than diesel under same conditions. Based on multivariable sensitivity analysis, it is indicated that accordant with diesel fuel, injection pressure (P<sub>in</sub>) and ambient pressure (P<sub>b</sub>) are the controlling parameters for RP-3 spray penetration distance, and P<sub>b</sub> is dominant on RP-3 spray cone angle. However, caused by cavitation intensity, RP-3 spray cone angle is more sensitive to nozzle diameter (φ) and cavitation number (Ca). Moreover, P<sub>b</sub> dominates over the sensitivity of spray irregularity and spray area is mainly controlled by P<sub>in</sub> .

Detailed mixing measurements from single-hole converging ECN injectors using Rayleigh scattering

Time resolved liquid and vapor fields of dodecane and oxymethylene ethers are measured from Spray A-3 and Spray D using high speed Rayleigh scattering and diffuse back illumination at the Engine Combustion Network (ECN) Spray A condition of 900 K and 22.8 kg/m3. Global quantities including mixture fraction, vapor and liquid penetration, as well as spreading angle are measured. The mixture fraction fields and vapor penetration profiles are well predicted by the 1-D Musculus-Kattke model. The mixture fraction field and vapor penetration from Spray A-3 are similar to those measured from Spray A in previous works. Spray D exhibits higher mixture fraction fields and vapor penetration due to its larger nozzle diameter. The quasi-steady mixture fraction fields from these injectors scale well when distance from the injector is normalized by the nozzle diameter. The turbulent dissipation structures were also analyzed based on the orientation, thickness, and magnitude of the mixing layers. The orientation and thickness are similar to other measurements in atmospheric gas jets, while the magnitude is lower. The thickness and magnitude are subject to uncertainties due to limitations in the imaging resolution of the system but still provide an order of magnitude as a useful reference for comparison against computational fluid dynamic simulations.

Specific power or droplet shear stress: Which is the primary cause of soil erosion under low-pressure sprinklers?

Specific power and droplet shear stress are generally considered to be the most critical indicators of soil erosion in sprinkler irrigation, but there is controversy about which indicator has a greater impact. This creates uncertainty in the optimization design of low-pressure sprinkler irrigation systems. In this study, a commonly used low-pressure sprinkler, i.e., Nelson D3000, was used to carry out in soil box experiments, to study the effects of specific power and average droplet shear stress at the end of a spray jet on soil erosion during sprinkler irrigation under three nozzle diameters (3.97, 5.95, and 7.94 mm), two operating pressures (103 and 138 kPa), and two soil textures (loamy sand and silty loam). Overall, the larger specific power or average droplet shear stress resulted in higher initial and steady runoff rates and a shorter time until runoff occurs and stabilizes. Enlarging the specific power or average droplet shear stress could significantly increase the initial infiltration rate, sediment yield, and surface soil bulk density, but the infiltration depth prior to runoff and surface soil porosity decreased. Furthermore, the specific power was observed to have greater correlations than average droplet shear stress with the surface runoff rate, initial infiltration rate, and increase in the soil bulk density and decrease in the soil porosity after irrigation. However, it was weakly related to the infiltration depth prior to runoff and sediment yield, indicating that the specific power could more accurately reflect the soil erosion with respect to the shear stress. To minimize the risk of soil erosion, a small operating pressure (103 kPa) is recommended in the design of center pivot irrigation systems, especially for the overhang of the system with large nozzle diameters. This research can provide the technical support for soil erosion prevention under low-pressure sprinkler irrigation.

Study on hydrogen dynamic leakage and flame propagation at normal-temperature and high-pressure

Experiments of two nozzle diameters at three ignition positions under three initial pressure conditions were carried out. The dynamic leakage characteristics and the stagnation parameters of flame propagation under normal temperature and high pressure conditions were studied. Based on van der Waal's equation, a model for predicting stagnation parameters, jet velocity and flow rate of hydrogen leakage was proposed. Compared with the experimental results, it was found that the maximum error occurred when the initial pressure was 200 bar. Theoretical leakage time was 1.66 s, experiment leakage time was 1.84 s, the error was 9.8%. Background-Oriented Schlieren image technology was used to record the flame development and propagation process after ignition. For the same nozzle diameter and ignition location, the higher pressure caused the flame to propagate faster upstream and downstream. For the same initial pressure and ignition position, a flame with a large nozzle diameter propagated faster upstream and downstream. For the same initial pressure and nozzle diameter, the farther the ignition point was, the greater the slope of flame attenuation when propagating upstream. Due to the attenuation of hydrogen concentration and jet velocity, the flame propagation velocity to the downstream decreased linearly with the increase of distance from the ignition location.

Impingement and breakup characteristics of free opposed impinging jets with unequal nozzle diameter

The free opposed impinging jets with unequal nozzle diameter is developed to improve mixing efficiency at unequal flowrates for liquid–liquid reactions. The liquid sheet breakup characteristics and droplet behavior are investigated using particle image velocimetry. Water, 40w% glycerol-water (40G), and 50% glycerol-water (50G) under different jet velocities and nozzle diameters are studied for comparison, the correlation equations are obtained and the errors are analyzed. When the jet velocity increases, the liquid sheet breakup mode exhibited a closed-rim mode, open-rim mode, rimless mode, wave or ligament mode, and fully developed mode for water and 40G under a nozzle diameter of 1.5–2 mm, and the first four modes were observed with the high viscosity liquid (50G) or under a large nozzle diameter (2–3 mm). As the jet velocity increases, the dimensionless breakup length increases sharply at the closed-rim and open-rim modes, and then decreases at the rimless mode. The sheet thickness, Sauter mean diameter, average droplet diameter, and droplet velocity decrease, and the droplet size becomes more uniform with increasing jet velocity. However, the opposite variation trend is observed with increasing viscosity and nozzle diameter, and the effect is more significant at u < 4.25 m/s. The droplet average diameter increases at u = 2.12 m/s and 3.18 m/s and decreases at u ≥ 4.25 m/s downwards along y-axis due to the coalescence and secondary breakup of droplets. The droplet velocity becomes lower as droplets move downwards along y-axis from −40 mm to −50 mm due to the dissipation of momentum. The results reveal that the increase of viscosity and nozzle diameter has a negative effect on liquid sheet and droplet behavior at low jet velocities. The rimless mode is the key mode affecting the transition of the sheet breakup mechanism, and after this mode, the negative effects of viscosity and nozzle diameter weaken due to the high momentum, which promotes the breakup of the liquid sheet and droplets. It will provide theoretical support for the mixing mechanism with unequal flowrates, and is helpful to expand the application of free opposed impinging jets.

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.

Investigation on diesel spray flame evolution and its conceptual model for large nozzle and high-density of ambient gas

To reveal the theory behind the ignition phenomenon of large nozzle diameter spray and better organize the combustion of two-stroke marine diesel engine, in this article, the numerical simulation has been made by CONVERGE to study the developing process of large nozzle spray and flame in constant volume combustion chamber. Spray and flame characteristics for different nozzle diameters 0.5 mm, 0.625 mm and 0.875 mm are compared to investigate the effect of nozzle diameter on spray and flame characteristics. Then the ambient pressure is increased and a swirl is added to discuss the spray and flame characteristics under high-density of ambient gas and swirl. It was shown that for large nozzle led spray heads, there would be several stripping processes of the spray head periphery under air-dragging work. The first stripped fuel remains on the periphery of the spray upstream, evaporating and igniting. The flame propagates through the stripped fuel evaporation path from the ignition position to the spray tip. Flame propagation stops after nearly reaching the spray tip due to the lack of the combustible mixture but the presence of unevaporated liquid fuel, which was caused by the large nozzle diameter slowing down the spray tip evaporation. The liquid fuel at the spray tip then evaporates and mixes with the air. Then flame begins to propagate through the vapor fuel path, enveloping the entire spray. Increasing ambient pressure accelerates spray break-up and evaporation. The flame can directly envelop the spray through the combustible mixture in the spray tip. Adding swirl pushes the separated swirl-facing side-periphery fuel to the spray tip. Ignition occurs in the spray tip and mid-part of spray leeside then flame propagates in the direction of each other direction.

Biocompatibility of 3D-Printed PLA, PEEK and PETG: Adhesion of Bone Marrow and Peritoneal Lavage Cells.

Samples in the form of cylindrical plates, additively manufactured using the fused deposition modelling (or filament freeform fabrication, FDM/FFF) technology from polylactide (PLA), polyethylene terephthalate glycol (PETG) and polyetheretherketone (PEEK), were studied in series of in-vitro experiments on the adhesion of rat bone-marrow cells and rat peritoneal cells. Methods of estimation of the absolute number of cells and polymer samples’ mass change were used for the evaluation of cells adhesion, followed by the evaluation of cell-culture supernatants. The results of experiments for both types of cells demonstrated a statistically significant change in the absolute number of cells (variation from 44 to 119%) and the weight of the polymer samples (variation from 0.61 to 2.18%), depending on roughness of sample surface, controlled by a nozzle diameter of a 3D printer as well as printing layer height. It was found that more cells adhere to PLA samples with a larger nozzle diameter and layer height. For PETG samples, the results did not show a clear relationship between cell adhesion and printing parameters. For PEEK samples, on the contrary, adhesion to samples printed with a lower nozzle diameter (higher resolution) is better than to samples printed with a larger nozzle diameter (lower resolution). The difference in results for various polymers can be explained by their chemical structure.

Parametric calibration study of fused filament fabrication printing with large nozzle diameter

The trend toward the scalability of fused filament fabrication requires strategies to reduce printing time. One way consists in using calibrated nozzles with larger diameters. However, the reduction in manufacturing time is accompanied by reduced printing resolution and changes in the control of the material’s viscous behavior. In this work, the parametric calibration was performed on a 1 mm diameter nozzle printing cubic models in polylactic acid. The procedure was divided into three steps: (i) identification of printing defects; (ii) systematic parametric study (based on Taguchi method); and (iii) interactive parametric refinement. The calibration of the 1 mm nozzle involved the analysis of six fused filament fabrication variables: layer thickness, extrusion temperature, extrusion multiplier, infill speed, perimeters speed, and first layer speed. Their effects were analyzed considering esthetic quality, dimensional and shape conformity, mass, and compression modulus variation of the parts. Despite the high degree of customization of fused filament fabrication printers, the results show that switching to a larger nozzle is not “plug-and-play”. The user needs to know the correlations between the printability of the material and the effects of the variables involved in slicing, especially extrusion multiplier and layer thickness. Both variables act directly on the main problem of printing with a 1 mm nozzle, controlling the extrusion volume with the best accommodation of the material between and within layers. The main contribution of the study highlights that large diameter nozzles can induce poorly distributed accumulations of excess material, which decreases the quality of surfaces, deforms parts, destabilizes dimensions, and disorganizes the mesostructure (reducing rigidity) of the models. Finally, the parameter refinement process defined a base configuration for future studies to improve 3D printing with 1 mm nozzles.

Numerical modeling and design decisions for aerostatic bearings with relatively large nozzle sizes in Magic-Angle Spinning (MAS) systems

Numerical stability analysis for aerostatic bearings was performed to obtain optimized design parameters for small submillimeter to millimeter range diameter cylindrical rotors. Such rotors are used in nuclear magnetic resonance (NMR) application to rotate sample around an axis inclined by magic angle (54.74o) relative to the magnetic field direction at rotational frequencies of about 100 kHz (magic-angle spinning, MAS). The governing Reynolds equation for the fluid film between rotor and bearing was modified for small size aerostatic bearings with relatively large nozzle diameters. The modified Reynolds equation was solved using a finite-volume method to obtain pressure and film thickness around the rotor. This led to the solution of the maximum stable inertial force as a function of rotational frequency and design parameters. The comparison with aerostatic bearings with infinitesimal nozzle sizes was obtained for supported rotor weight and critical vibrational frequency of the rotor. The stable inertial force was found to correspond to a specific nozzle diameter and a specific rotor–bearing clearance. Numerical investigation also shows an enhancement of stable inertial force with decreasing nozzle number or increasing molecular mass of the impinging gas for a specific range of nozzle parameters. Experimental observations further confirmed the role of nozzle diameter, nozzle number and molecular weight of the gas in enhancing the rotor spinning frequency. Further, design decisions were made based on such analysis and were tested for varying rotor size and bearing properties. Using design optimization based on numerical simulation, the maximum frequency of rotation for a home-built 0.4mm MAS rotor could be enhanced from 25 kHz up to 110 kHz, still below the extrapolation from large rotors.

Hilbert‐Huang Transform Analysis of the Concentration Field of a Two‐Layer Impinging Stream Mixer

Hilbert‐Huang Transform Analysis of the Concentration Field of a Two‐Layer Impinging Stream Mixer

Experimental Study on the Operating Parameters of a Pulse-Jet Filter Bag Cleaning System

In this study, the effects of various parameters of the filter bag cleaning system, such as the blow tube size (20A, 40A, 50A), the nozzle diameter (5, 10, 15, 20, 25, 30 mm), the initial tank pressure (0.3, 0.4, 0.5, 0.6, 0.7 MPa), and the pulse duration (50, 100, 150, 200, 250, 300 ms), were evaluated with a view of peak pressure and pressure impulse. This study shows that the peak pressure and pressure impulse are not always in a proportional relationship, since pressure impulse aggregates static pressure and pressure over elapsed time together. For the system investigated, it is found that increasing the blow tube size and pulse duration induce a larger pressure impulse with little change in peak pressure, while higher initial tank pressure enhances both peak pressure and pressure impulse. On the other hand, a larger nozzle diameter was found to increase peak pressure rather than pressure impulse throughout the bag. The experimental results suggest that a higher initial tank pressure is a convenient way to elevate the overall dust-cleaning performance of pulse-jet systems, while other parameters (blow tube size, nozzle diameter, initial tank pressure) can be adopted according to the desired effect for given environment.

Comparison between the cooling performances of micro-jet impingement systems using liquid metal and water as coolants for high power electronics

Liquid metals are attractive coolants for MEMS with a high heat flux. However, most existing studies on liquid metals were focused on micro- and mini-channel heat sinks. In the present work, we applied liquid metals into three micro-jet impingement systems, i.e., jet impingement surface cooling (JISC), jet impingement body cooling (JIBC) and hybrid body cooling (HBC) systems. Analytic and numerical models were established, based on which the thermal resistances of these systems using water and liquid gallium (Ga) as coolants were compared and analyzed. The results indicated that the systems using liquid Ga always achieved a smaller thermal resistance compared to water, showing a maximum decrease of 29.8% in thermal resistance and a largest drop of 12.6 K in chip temperature. The minimum thermal resistance using liquid metals reaches as low as 0.033 K/W. In addition, JIBC system always had the smallest thermal resistance when water was used. However, in the case of liquid Ga, HBC system performs best at small flow rates. The influences of geometry parameters on the system cooling performance were analyzed. It was shown that an optimal nozzle spacing of 4.7 mm existed. Moreover, the thermal resistances of the three systems increased with an increasing nozzle diameter, and the thermal resistance of JIBC system would exceed that of HBC system at an enough large nozzle diameter (e.g., ∼0.28 mm for Ga). Regardless of the coolant used, the thermal resistances of JIBC system kept nearly constant with the variation of side gap height. For HBC system, the thermal resistance increased obviously with an increasing side gap height when water was used as coolant, while barely changed for liquid Ga. The findings in this study provide a guidance for the design and operation of micro-jet impingement systems employing liquid metals as coolant.

Determination of optimum production parameters for 3D printers based on nozzle diameter

PurposeThe purpose of this paper is to determine the optimum nozzle diameter for parts production with polylactic acid using a three-dimensional printer. The additive manufacturing method used was fused filament fabrication.Design/methodology/approachDesigners and researchers have focused on the effects of these parameters on part strength. Additionally, production time is one of the disadvantages of this manufacturing method that researchers are trying to overcome. The production parameters that stand out at this point are nozzle diameter and layer thickness.FindingsAs a result of the study, it was determined that the increased nozzle diameter led to increased part strength. At the same time, layer thickness had the most significant effect on surface quality. The increased nozzle diameter and part density led to decreased production time. It was concluded that larger nozzle diameter and lower layer thickness should be used for parts with superior properties.Research limitations/implicationsThe experimental printing parameters used in the study were nozzle diameter (0.2, 0.4, 0.6, 0.8, 1.0 and 1.2 mm), layer thickness (0.1, 0.2 and 0.3 mm) and printing orientation (0°, 45° and 90°). The effects of printing parameters on part strength, dimensional accuracy, surface quality and part density were analyzed experimentally.Originality/valueThe effects of several printing parameters have been examined in the literature. However, the effect of different nozzle diameters has been ignored. There are limited experimental studies that examine the effect of nozzle diameter on mechanical properties, surface roughness, dimensional quality and production time. In this regard, the results obtained from various nozzle diameters used in this study will significantly contribute to the literature.

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.