Dual Nozzle Research Articles

Average Degree of Coverage and Coverage Unevenness Coefficient as Parameters for Spraying Quality Assessment

The purpose of the research was to determine the influence of selected factors on the average degree of coverage and uniformity of liquid spray coverage using selected single and dual flat fan nozzles. The impact of nozzle type, spray pressure, driving speed, and spray angle on the average degree of coverage and coverage unevenness coefficient were studied. The research was conducted with special spray track machinery designed and constructed to control and change the boom height, spray angle, driving speed, and spray pressure. Based on the research results, it was found that the highest average coverage was obtained for single standard flat fan nozzles and dual anti-drift flat fan nozzles. At the same time, the highest values of unevenness were observed for these nozzles. Inverse relationships were obtained for air-induction nozzles. Maximization of coverage with simultaneous minimization of unevenness can be achieved by using a medium droplet size for single flat fan nozzles (volume median diameter (VMD) = 300 μm) and coarse droplet size for dual flat fan nozzles (VMD = 352 μm), with low driving speed (respectively 1.1 m∙s−1 and 1.6 m∙s−1) and angling of the nozzle by 20° in the opposite direction to the direction of travel.

A dual nozzle 3D printing system for super soft composite hydrogels

Due to their inability to sustain their own weight, 3D printing materials as soft as human tissues is challenging. Hereby we describe the development of an extrusion additive manufacturing (AM) machine able to 3D print super soft hydrogels with micro-scale precision. By designing and integrating new subsystems into a conventional extrusion-based 3D printer, we obtained hardware that encompasses a range of new capabilities. In particular, we integrated a heated dual nozzle extrusion system and a cooling platform in the new system. In addition, we altered the electronics and software of the 3D printer to ensure fully automatized procedures are delivered by the 3D printing device, and super-soft tissue mimicking parts are produced. With regards to the electronics, we added new devices to control the temperature of the extrusion system. As for the software, the firmware of the conventional 3D printer was changed and modified to allow for the flow rate control of the ink, thus eliminating overflows in sections of the printing path where the direction/speed changes sharply.

Electrothermal shape memory behavior and recovery force of four-dimensional printed continuous carbon fiber/polylactic acid composite

Four-dimensional (4D) printing technology provides new ideas for the preparation and structural design of multifunctional shape memory composites. Excellent electrothermal shape memory behavior and high shape recovery force are urgently demanded in practical applications. Herein, a continuous carbon fiber reinforced polylactic acid shape memory composite with high strength, high shape recovery force, low-voltage response and excellent electrothermal shape memory behavior was printed using a dual nozzle 3D printer. The effects of specimen thickness, carbon fiber content, and applied voltage on the electrothermal shape memory behavior and shape recovery force were investigated. The reinforcing effect of carbon fiber on 4D printed composite materials was characterized by dynamic mechanical analysis and 3-point bending test. Under electrical thermal stimulation, the shape recovery ratio of most specimens can reach 90%. The shape recovery force of different specimens was obtained by self-designed shape recovery force test system, and the maximum shape recovery force was about 7.38 N. The results show that the introduction of continuous carbon fiber not only significantly enhances the strength of 4D printed composite, but also improves the shape recovery force. The demonstrations of an electrothermal response shape memory deployable claw-device and load-bearing lifting device manifest the potential application in self-actuated intelligent structures.

Reacting Flow Simulations of a Dual Throat-Dual Fuel Thruster

Numerical simulation of the supersonic turbulent reacting flow field in a dual throat- dual fuel rocket thrust chamber is presented. Future single stage to orbit and high lift space transportation missions aspire a reliable, efficient, and cost-effective propulsion systems. The dual throat-dual fuel concept is a simple altitude compensating propulsion alternative with reusable possibilities. Turbulent reacting supersonic flow field emanating from independent thrust chambers needs to be resolved for a better understanding of the flow structures and design modifications for the performance improvement. The operation of a dual throat nozzle brings about a unique shock train in reacting supersonic flow. Two-dimensional axis-symmetric compressible reacting flow field has been solved using HLLC (Harten, Lax, van Leer, with Contact wave) scheme based finite volume Riemann solver with multi-step finite rate chemistry model for hydrocarbon/hydrogen-oxygen combustion. The computational procedure has been validated with experimental data for species distribution of a coaxial supersonic combustor. Chemical species distribution in the supersonic free shear layer is analyzed in detail to explore the nature of active reaction zones in the flow field.

Numerical Study of Fluidic Thrust Vector Control Using Dual Throat Nozzle

Compared to a variety of mechanical vectoring nozzles, fluidic vectoring nozzles possess more research value nowadays. The dual throat nozzle is gradually developing into an outstanding technology to handle supersonic and hypersonic aircraft deflections. Three-dimensional, steady, compressible, and viscous flows in rectangular dual throat nozzles are numerically investigated by resolving Reynolds-averaged Navier-Stokes equations and shear stress transport k-omega turbulence model. Computational fluid dynamics results are verified against the existing experimental data, where a good consistency is gained. The impacts of nozzle pressure ratio, injection-to-mainstream momentum flux ratio, and setup angle of the slot injector on the systemic performance are examined. Useful conclusions are summarized for engineering designers. Firstly, pitching angles decline along with an increasing nozzle pressure ratio, while systemic thrust ratio and thrust efficiency increase. Secondly, thrust vector angles enlarge with an increase of the injection-to-mainstream momentum flux ratio, whereas both systemic thrust ratio and thrust efficiency decay. Finally, the setup angle of the slot injector impacts the systemic performance remarkably. Although the pitching angle for the setup angle of 120° is highest, comprehensive characteristics in terms of systemic thrust efficiency and systemic thrust ratio for the setup angle of 150° are more excellent.

Beyond the Single-Nozzle: Coaxial Electrospinning Enables Innovative Nanofiber Chemistries, Geometries, and Applications.

With an ever increasing scientific, technological, and industrial interest in high surface area, porous nanofiber mats, electrospinning has emerged as a popular method to produce fibrous assemblies for use across biomedical, energy, and environmental applications. However, not all precursor solutions nor complex geometries can be easily fabricated using the traditional single-nozzle apparatus. Therefore, coaxial electrospinning, a modified version of electrospinning that features a concentrically aligned dual nozzle, has been developed. This review will first describe the mechanism of electrospinning two precursor solutions simultaneously and the operational parameters that need to be optimized to fabricate continuous fibers. Modifications that can be made to the coaxial electrospinning process, which enable the fabrication of uniform fibers with improved properties, as well as the fabrication of fibers that are hollow, functionalized, and from "nonspinnable precursors" will be discussed as a means of promoting the advantages of using a coaxial setup. Examples of how coaxially electrospun nanofibers are employed in diverse applications will be provided throughout this review. We conclude with a timely discussion about the current limitations and challenges of coaxial electrospinning.

Investigation on Dual Nozzle Fused Deposition Modelling using Industrial Robot

ABSTRACT Fused Deposition Modelling (FDM) process builds the 3D objects by extruding the material in layer-by-layer fashion from bottom-to-top. In a conventional FDM machine, due to limited degrees of freedom, change in extruder orientation is not possible. Industrial robots with 6 degrees of freedom are capable to move and orient the end effector in 3D space with high resolution and repeatability. The limitation of the conventional FDM machine can overcome by using an industrial robot with a dual nozzle extruder as an end effector. In this work, an attempt is made to print objects with an industrial robot with dual nozzle extruder attached to it. The results showed that the orientation of the extruder can be changed easily so that a strong bonding between the layers is possible while going for dual nozzle extrusion. By extruding the same material with both nozzles, the printing time is less than the conventional FDM process. The methodology adopted for printing the objects using ABB Robotstudio® simulation software and printing a component with ABB IRB1600 industrial robot is presented in this article.

3D bioprinting of a biomimetic meniscal scaffold for application in tissue engineering

Appropriate biomimetic scaffolds created via 3D bioprinting are promising methods for treating damaged menisci. However, given the unique anatomical structure and complex stress environment of the meniscus, many studies have adopted various techniques to take full advantage of different materials, such as the printing combined with infusion, or electrospining, to chase the biomimetic meniscus, which makes the process complicated to some extent. Some researchers have tried to tackle the challenges only by 3D biopringting, while its alternative materials and models have been constrained. In this study, based on a multilayer biomimetic strategy, we optimized the preparation of meniscus-derived bioink, gelatin methacrylate (GelMA)/meniscal extracellular matrix (MECM), to take printability and cytocompatibility into account together. Subsequently, a customized 3D bioprinting system featuring a dual nozzle + multitemperature printing was used to integrate the advantages of polycaprolactone (PCL) and meniscal fibrocartilage chondrocytes (MFCs)-laden GelMA/MECM bioink to complete the biomimetic meniscal scaffold, which had the best biomimetic features in terms of morphology and components. Furthermore, cell viability, mechanics, biodegradation and tissue formation in vivo were performed to ensure that the scaffold had sufficient feasibility and functionality, thereby providing a reliable basis for its application in tissue engineering.

Underwater laser cutting of thick stainless steel blocks using single and dual nozzles

Laser cutting was performed using a 6-kW fiber laser with two different nozzle configurations to extend the permissible cutting thickness of steel blocks in a water environment. The first nozzle configuration involved a single minimum length nozzle (MLN) operating at an upstream gas gauge pressure of 15 bar; the second configuration consisted of a truncated aerospike nozzle coupled with an MLN. These configurations were designed to form a core air-filled cavity with the submerged jet to have denser and more lengthened characteristics for extending the possible transmission distance of the high-power laser beam, which is vulnerable to water absorption. Before underwater cutting, we performed a Schlieren visualization measurement of the gas jet’s flow behavior as it was discharged from the single and dual nozzles in the ambient air, after which, the stainless steel blocks were laser-cut underwater using both nozzle configurations. The thickness of the selected steel blocks varied from 60 to 80 mm according to the capabilities of the nozzles used to form the air cavity.

Fuel placement and atomization inside a gas-turbine fuel injector at realistic operating conditions

The atomization process and fuel placement inside a gas turbine fuel injector are investigated at realistic operating conditions to understand the role of individual flow processes and hardware components. A high pressure, high temperature spray test facility is developed that can simulate a wide range of aero-engine operating conditions. The fuel injector is a swirl cup - dual orifice nozzle combination which is used in the rich dome combustors of various aero-engines. The internal flow field is captured using time-resolved laser induced fluorescence imaging and phase Doppler interferometry measurements. A stage-wise characterization is adopted to track the spray formation as the flow evolves through the swirl cup. The fuel placement at the cup exit is mainly decided by pilot nozzle spray characteristics and the relative momentum exchange between the gas and liquid phases. At the swirl cup exit, two class of droplets are formed: (1) droplets originated directly from the pilot nozzle, which are convected downstream by the primary air swirl, (2) droplets originated from the rim, which are atomized by the shear layer. The relative percentage of these two droplet classes depends on the pilot nozzle operation at low and high power conditions. The effect of primary spray and wall-filming are minimal towards improving the atomization. In both low and high power operating cases, the counter-rotating shear layer interactions are identified as the major mechanism that is improving the atomization process in swirl cup.

Fabrication of a pediatric torso phantom with multiple tissues represented using a dual nozzle thermoplastic 3D printer.

PurposeTo demonstrate an on‐demand and nearly automatic method for fabricating tissue‐equivalent physical anthropomorphic phantoms for imaging and dosimetry applications using a dual nozzle thermoplastic three‐dimensional (3D) printer and two types of plastic.MethodsTwo 3D printing plastics were investigated: (a) Normal polylactic acid (PLA) as a soft tissue simulant and (b) Iron PLA (PLA‐Fe), a composite of PLA and iron powder, as a bone simulant. The plastics and geometry of a 1‐yr‐old computational phantom were combined with a dual extrusion 3D printer to fabricate an anthropomorphic imaging phantom. The volumetric fill density of the 3D‐printed parts was varied to approximate tissues of different radiographic density using a calibration curve relating the printer infill density setting to measured CT number. As a demonstration of our method we printed a 10 cm axial cross‐section of the computational phantom’s torso at full scale. We imaged the phantom on a CT scanner and compared HU values to those of a 1‐yr‐old patient and a commercial 5‐yr‐old physical phantom.ResultsThe phantom was printed in six parts over the course of a week. The printed phantom included 30 separate anatomical regions including soft tissue remainder, lungs (left and right), heart, esophagus, rib cage (left and right ribs 1 to 10), clavicles (left and right), scapulae (left and right), thoracic vertebrae (one solid object defining thoracic vertebrae T1 to T9). CT scanning of the phantom showed five distinct radiographic regions (heart, lung, soft tissue remainder, bone, and air cavity) despite using only two types of plastic. The 3D‐printed phantom demonstrated excellent similarity to commercially available phantoms, although key limitations in the printer and printing materials leave opportunity for improvement.ConclusionPatient‐specific anthropomorphic phantoms can be 3D printed and assembled in sections for imaging and dosimetry applications. Such phantoms will be useful for dose verification purposes when commercial phantoms are unavailable for purchase in the specific anatomies of interest.

Experimental evaluation and numerical simulation of performance of the bypass dual throat nozzle

Bypass dual throat nozzle (BDTN) is a modern concept of fluidic thrust vector control. This method able to solve the problem of thrust loss without need the secondary mass flow from other part of engine. Internal nozzle performance and thrust vector angles have been measured in the BDTN experimentally and numerically. A new simple approach is proposed to detect the thrust deflection angle. Numerical simulation of 3-D turbulent air flow is carried out by using the RNG k-e turbulence model. The obtained results of thrust coefficient, discharge coefficient and thrust deflection angle have been validated by comparing with measured experimental data. The results show that for nozzle pressure ratio of 1–4 the tested nozzle able to deflect the thrust vector of 26.5°-19°. By increasing NPR from 2 up to 4, the thrust coefficient values will change in the range of 0.85-0.93. Also the effect of different positions of the bypass channel on the BDTN performance parameters has been investigated numerically. The predicted results show that the BDTN configuration with bypass duct on the first nozzle throat has the highest value of thrust deflection angle over the range of NPRs.

Pengaruh Densitas Isi terhadap Ketelitian Dimensi pada Produk Mesin 3D Printing

Additive manufacturing is a very important technology in industrial manufacturing 4.0 era. It is because this technology can change an object from a virtual form into a physical model quickly and easily. One of additive manufacturing type is the FDM rapid prototyping machine. A machine has modified from a single nozzle to a dual nozzle so the printing process can be faster and can be used for different color filaments. This study compared 3D models made in the CAD software and the result of test specimens that have been printed using MakerGear M2 3D machine by measuring using a measurement tool profile projector. The host software of the machine was set up at 20%, 40%, 60%, 80% and 100% infill density. The results of analysis on test specimens show the best accuracy at 20% infill density.

Experimental and 3-D Numerical Heat Transfer Analyses of Dual Spray Water Nozzle Impingement on a Flat Plate

Spray impingement cooling is the major method currently used to cool steel after the hot-rolling process. In this study, dual nozzles are used to investigate the cooling character of the flat plate using for the spray impingement cooling process. Based on an experimental temperature measurement, a three-dimensional numerical model is set up to calculate the transient heat transfer coefficient of the cooling plate by solving the inverse heat conduction problem with the conjugate gradient method. Both the experimental and numerical results indicated that an interference region appeared between the two jet spray impingement regions. The interference pitch varied with the flow rates, the height from the plane to the jet outlet, and the distance between the two jets. As water spread over the plate, the heat dissipation region gradually stretched from the impingement region to the interference and flow regions. A peak in the heat flux curve was observed when the water arrived at the wet front of the flow. Meanwhile, the peak in the heat flux decreased as the distance from the impingement region increased. A maximum local heat transfer coefficient 23,000 W/(m2K) was observed in this experiment. The global average heat transfer coefficient increased with increases in the water flow rate, but it decreased with increases in the pitch.

Numerical Simulation of the Behavior of Hydrogen Source in a Novel Welding Process to Reduce Diffusible Hydrogen

This study aims to reduce the diffusible hydrogen content in deposited metal during gas metal arc welding (GMAW) and flux-cored arc welding (FCAW) which induces cold cracking. To achieve this, a novel welding torch with a dual gas nozzle has been developed. This special welding torch decreases the hydrogen source gas evaporated from a welding wire by the suction from the inner gas nozzle. In order to improve the suction efficiency of this evaporated gas, precise control of the suction gas flow is indispensable. In this paper, a simplified numerical simulation model of this process has been described. This model can take account of the evaporation of the hydrogen source gas from the wire while simulating the behavior of the shielding gas and the arc. Using this model, the effect of suction nozzle structure and torch operating conditions on suction gas flow pattern and suction efficiency was also investigated to understand the process mechanism. Furthermore, the diffusible hydrogen content in deposited metal was measured by chromatography as a validation step. Results show that some of the shielding gas introduced from a shielding nozzle was drawn inward and also branched into an upward flow that was sucked into the suction nozzle and a downward flow to a base metal. This branching height was defined as the suction limit height, which decisively governed the suction efficiency. As a result, in order to reduce the diffusible hydrogen, it was suggested that the suction limit height should be controlled towards below the wire position, where the evaporation rate of the hydrogen source gas peaks through optimization of the suction nozzle design and the torch operating conditions.

Design and Preliminary Analysis of the Variable Axisymmetric Divergent Bypass Dual Throat Nozzle

Abstract Turbofan engines with afterburners usually have variable nozzle throat area, and the nozzle throat area may increase by 50–100% during afterburning. An axisymmetric divergent bypass dual throat nozzle (ADBDTN) can offer high thrust vectoring efficiency without requiring additional secondary flow in the pitch and yaw directions. In this study, a variable ADBDTN configuration with flow adaptive capability, wide nozzle throat area adjustment range, and excellent overall performance was designed and investigated numerically. The nozzle throat and exit area can be controlled mechanically, while thrust vectoring is achieved via fluidic methods. Both the original variable geometry schemes and their corresponding improved schemes, namely, “slider-rocker mechanism & rotation” (SRM-R) and “slider-rocker mechanism & slide” (SRM-S) schemes, along with their improved schemes, were proposed and investigated. Results indicated that compared to the original variable geometry schemes, the nozzle configurations with improved variable geometry schemes not only achieve 50% increase in the nozzle throat area but also acquire flow adaptive capability and excellent overall performance by appropriately adjusting the nozzle exit area. At a nozzle pressure ratio (NPR) of 4.47, the highest thrust coefficient reaches 0.940; the largest pitch thrust-vector angle is 19.52 deg; and the discharge coefficients are 0.968 and 0.970 under the nonafterburning and afterburning states, respectively. In addition, compared to the improved SRM-R scheme, the nozzle configuration with improved SRM-S scheme possesses better overall performance.

Design of a debinding process for polymetallic material green parts fabricated via metal paste injection 3D printing with dual nozzles.

Debinding is one of the most critical processes in metal paste injection 3D printing technology (MPI). In order to design the optimal debinding parameters, the debinding temperature, debinding time and heating rate were discussed from the perspective of dynamics. The results showed that there was a peak in liquid phase mass transfer during debinding, exhibiting the characteristics of migration with debinding temperatures. For gas phase mass transfer, when the temperature was 300 °C, the thermal debinding diffusion coefficient was the largest (9.7 × 10−5 cm2 s−1) and the corresponding debinding time was 3.5 h. By analyzing the activation energy of the debinding reaction, when the heating rate was 10 °C min−1, the activation energy required for the thermal debinding reaction was the smallest. Combined with the sintering process, the interwoven structural parts of the copper and cupronickel components were finally obtained. The average hardness of the polymetallic parts was 78.8 HV, and the density was 8.1 g cm−3.

Effect of carbon fibre on reinforcement of thermoplastics using FDM and RSM

Continuous fibre-reinforced composites have significant industrial importance and usage. However, they are limited by design considerations and high-cost manufacturing operations. This article presents a way forward to utilize Fused Deposition Modelling – a 3D printing technique – to manufacture continuous carbon fibre-reinforced thermoplastics. Several parameters including number of reinforced layers, material impact and interlayer gap have been investigated and optimized using response surface method. Successful incorporation of modified novel nozzle design in a dual nozzle setup resulted in the realization of controlled manufacturing of continuously reinforced composites leading to reinforced yet smooth surface finished samples. Several samples were made, and mechanical testing, parameter optimization, strength calculations and fracture analysis were carried out. For polylactic acid (PLA), tensile strength of 112 MPa and flexural strength of 164 MPA were achieved – an almost 3 times increase from pure PLA printing. The approach presented in this article can forward continuous fibre-reinforced composites for industrial usage with its controlled fibre layup and programmable thread orientation features.

The influence of dual stream jet nozzle internal parts on the three-dimensional flow structure in a supersonic jet

The work is devoted to the experimental study of a high-speed jet exhausting from a model dual stream jet nozzle, performed using non-contact (shadow visualization) and probe (total-pressure pneumatic receiver) methods for measuring gasdynamic quantities. Azimuthal non-uniformity of the pressure distribution, whose value in the external duct is much higher than that in the internal duct, is revealed. The cause for the formation of the spatial flow structure is related to the supporting pylons inside the nozzle contour and to the occurrence of a transonic flow regime in the external duct.

Experimental and numerical investigation of an axisymmetric divergent dual throat nozzle

The dual throat nozzle achieves higher thrust vectoring efficiencies and lesser thrust loss than other fluidic thrust-vectoring nozzles. Separation always occurs at the bottom of the cavity with complex three-dimensional characteristics for the dual throat nozzle. In this paper, by comparing the flow structure, nozzle surface static pressure distributions and skin friction lines, which are obtained by numerical simulations and wind tunnel experiments, an axisymmetric divergent dual throat nozzle is investigated in detail. The main results show the following findings. (1) The experimental schlieren photographs confirm again that the divergent nozzle configuration has the starting problem from an intuitive perspective. Meanwhile, the flow structure and nozzle surface static pressure distributions obtained by numerical simulations are consistent with the experimental results, except for the low nozzle pressure ratios. (2) The circumferential pressure difference is negligible upstream of the separation line but obvious downstream of the separation line. The skin friction lines and nozzle surface static pressure distributions of different circumferential angles obtained by experiments both prove that the actual flow in the axisymmetric divergent dual throat nozzle indeed possesses three-dimensional characteristics. Therefore, it is necessary to utilize the full three-dimensional computational domain to study the complex three-dimensional characteristics of the flow for the axisymmetric divergent dual throat nozzle thoroughly.