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Article
Publication date: 17 June 2021

Yih-Lin Cheng and Tzu-Wei Tseng

Material-jetting (MJ) three-dimensional (3D) printing processes are competitive due to their printing resolution and printing speed. Driving waveform design of piezoelectric…

Abstract

Purpose

Material-jetting (MJ) three-dimensional (3D) printing processes are competitive due to their printing resolution and printing speed. Driving waveform design of piezoelectric printhead in MJ would affect droplet formation and performance, but there are very limited studies on it besides patents and know-hows by commercial manufacturers. Therefore, in this research, the waveform design process to efficiently attain suitable parameters for a multi-nozzle piezoelectric printhead was studied. Therefore, this research aims to study the waveform design process to efficiently attain suitable parameters for a multi-nozzle piezoelectric printhead.

Design/methodology/approach

Ricoh’s Gen4L printhead was adopted. A high-speed camera captured pictures of jetted droplets and droplet velocity was calculated. The waveforms included single-, double- and triple-pulse trapezoidal patterns. The effects of parameters were investigated and the suitable ones were determined based on the avoidance of satellite drops and preference of higher droplet velocity.

Findings

In a single-pulse waveform, an increase of fill time (Tf) decreased the droplet velocity. The maximum velocity happened at the same pulse width, the sum of fill time and hold time (Tf + Th). In double- and triple-pulse, a voltage difference (Vd) above zero in the holding stage was adopted except the last pulse to avoid satellite drops. Suitable parameters for the selected resin were obtained and the time-saving design process was established.

Research limitations/implications

Based on the effects of parameters and observed data trends, suggested procedures to determine suitable parameters were proposed with fewer experiments.

Practical implications

This study has verified the feasibility of suggested design procedures on another resin. The required number of trials was reduced significantly.

Originality/value

This research investigated the process of driving waveform design for the multi-nozzle piezoelectric printhead. The suggested procedures of finding suitable waveform parameters can reduce experimental trials and will be applicable to other MJ 3D printers when new materials are introduced.

Details

Rapid Prototyping Journal, vol. 27 no. 6
Type: Research Article
ISSN: 1355-2546

Keywords

Article
Publication date: 13 October 2021

Nithya Subramani, Sangeetha M., Vijayaraja Kengaiah and Sai Prakash

The purpose of this paper is to find the droplets impact on the airplane wing structure. Two kinds of characteristics of the droplet at different velocity and viscosity are…

Abstract

Purpose

The purpose of this paper is to find the droplets impact on the airplane wing structure. Two kinds of characteristics of the droplet at different velocity and viscosity are assumed. The droplet is assumed to be spherical cubic form and it is injected from the convergent divergent nozzle with a passive control.

Design/methodology/approach

This paper presents the results of a numerical simulation of droplet impact on the horizontal surface. The effects of impact parameters are studied. The splash effect of the droplet also visualized. The results are presented in form of stress, strain, displacement magnitude of the droplet.

Findings

Crosswire is used as passive control. The behavior of the droplet impact is observed based on the kinetic energy and the gravitational forces.

Originality/value

The results predict that smooth particle hydrodynamic designed droplet not only depend on the equation of state of the droplet but also the injection velocity from the nozzle. It also determined that droplet velocity is depending on the viscosity of the fluid.

Details

Aircraft Engineering and Aerospace Technology, vol. 94 no. 4
Type: Research Article
ISSN: 1748-8842

Keywords

Article
Publication date: 23 November 2020

Sheng Chen, Yuming Xing, Xin Liu and Liang Zhao

The purpose of this study is to investigate the effect of the injection angle α on the spray structures of an air-blast atomizer and help enhance the understanding of droplet-gas…

Abstract

Purpose

The purpose of this study is to investigate the effect of the injection angle α on the spray structures of an air-blast atomizer and help enhance the understanding of droplet-gas mixing process in such atomizers in the engineering domain.

Design/methodology/approach

The phenomena in the air-blast atomizer were numerically modelled using the computational fluid dynamics software Fluent 17.2. The Euler-Lagrange approach was applied to model the droplet tracking and droplet-gas interaction in studied cases. The standard k-ε model was used to simulate the turbulent flow. A model with a modified drag coefficient was used to consider the effects of the bending of the liquid column and its penetration in the primary breakup region. The Kelvin-Helmholtz, Rayleigh-Taylor model was applied to consider the secondary breakup of the droplets.

Findings

The basic spatial distribution and spray structures of the droplets corresponding to the angled liquid jet (α = 60°) were similar to those reported in liquid jets injected transversely into a gaseous crossflow studies. The injection angle α did not considerably influence the averaged Sauter to mean diameter (SMD) of the cross-sections. However, the spray structures pertaining to α = 30°, α = 60° and α = 90° were considerably different. In the case of the atomizer with multiple injections, a “collision region” was observed at α = 60° and characterized by a higher ci and larger averaged SMD in the central parts of the cross-sections.

Originality/value

The injection angle α is a key design parameter for air-blast atomizers. The findings of this study can help enhance the understanding of the droplet-gas mixing process in air-blast atomizers. Engineers who design air-blast atomizers and face new challenges in the process can refer to the presented findings to obtain the desired atomization performance. The code has been validated and can be used in the engineering design process of the gas-liquid jet atomizer.

Details

Engineering Computations, vol. 38 no. 5
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 19 December 2018

Reza Hadjiaghaie Vafaie, Hossein Dehganpour and Abolfazl Moradpour

Digital microfluidic devices have been demonstrated to have great potential for a wide range of applications. These devices need expensive photolithography process and clean room…

Abstract

Purpose

Digital microfluidic devices have been demonstrated to have great potential for a wide range of applications. These devices need expensive photolithography process and clean room facilities, while printed circuit board (PCB) technology provides high configurability and at low cost. This study aims to investigate the mechanism of electrowetting-on-a-dielectric (EWOD) on PCB by solving the multiphysics interaction between fluid droplet and electric field. The performance of system will be improved by inducing an efficient electric field inside the droplet.

Design/methodology/approach

To induce an electric field inside the droplet on a PCB and change the initial contact angle, the mechanism of EWOD is studied based on energy minimization method and a set of simulations are carried out by considering multiphysics interaction between the fluid droplet and external electric field. The performance of EWOD on a PCB system is investigated using different electrode structures.

Findings

Surface tension plays an efficient role in smaller sizes and can be used to move and control a fluid droplet on a surface by changing the interfacial surface tension. EWOD on a PCB system is studied. and it revealed that any change in electric field affects the droplet contact angle and as a result droplet deformation and movement. The electrode pattern is an important parameter which could change the electric potential distribution inside the droplet. Array of electrodes with square, zigzag interdigitated and crescent shapes are studied to enhance the EWOD force on a PCB substrate. Based on the results, the radial shape of the crescent electrodes keeps almost the same actuated contact line, applies uniform force on the droplet periphery and prevents the droplet from large deformation. A droplet velocity of 0.6 mm/s is achieved by exciting the crescent electrodes at 315 V. Furthermore, the behavior of system is characterized for process parameters such as actuation voltage, dielectric constant of insulator layer, fluidic material properties and the resultant velocity and contact angle. The study of contact angle distribution and droplet motion revealed that it is helpful to generate EWOD mechanism on a PCB which does not need more complicated fabrication processes.

Originality/value

The ability to handle and manipulate the droplets is very important for chemistry on-chip analysis such as immunoassay chips. Furthermore, a PCB-based electrowetting-on-dielectric device is of high interest because it does not need cleanroom facilities and avoids additional high-cost fabrication processes. In the present research, the EWOD mechanism is studied on a PCB by using different electrode patterns.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 38 no. 1
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 3 September 2019

Xin Wang, Bo Xu and Z. Chen

This paper aims to investigate spontaneous movement of single droplet on chemically heterogeneous surfaces induced by the net surface tension, using the improved three-dimensional…

Abstract

Purpose

This paper aims to investigate spontaneous movement of single droplet on chemically heterogeneous surfaces induced by the net surface tension, using the improved three-dimensional (3D) lattice Boltzmann (LB) method.

Design/methodology/approach

D3Q19 Shan-Chen LB model is improved in this paper. Segmented particle distribution functions coupled with the P-R equation of state are introduced to maintain the higher accuracy and greater stability. In addition, exact difference method (EDM) is adopted to implement force term to predict the droplet deformation and dynamics.

Findings

The numerical results demonstrate that spontaneous movement of single droplet (=1.8 µm) along wedge-shaped tracks is driven by net surface tension. Advancing angle decreases instantaneously with time, while receding angle changes slightly first and then decreases rapidly. Wetting length is affected by vertex angle and wetting difference, whereas the final value is only dependent on the stronger wettability. Although the velocity of single droplet on wedge-shaped tracks can be increased by the larger vertex angle, it has a negative influence on the displacement. For the same wetting difference, vertex angle equal to 30º is an optimization strategy in this model. If the simulation length is extended enough, then the smaller vertex angle is beneficial for the droplet movement. In addition, a larger wetting difference is beneficial to spontaneous movement, which can speed up the droplet movement.

Originality/value

The proposed numerical model of droplet dynamics on chemically heterogeneous surfaces provides fundamental insights for the enhancement of drop-wise condensation heat transfer.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 30 no. 2
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 30 October 2018

Yanqing Li, Daming Li, Shean Bie, Zhichao Wang, Hongqiang Zhang, Xingchen Tang and Zhu Zhen

A new coupled model is developed to simulate the interaction between fluid droplet collisions on discrete particles (DPs) by using mathematic function.

Abstract

Purpose

A new coupled model is developed to simulate the interaction between fluid droplet collisions on discrete particles (DPs) by using mathematic function.

Design/methodology/approach

In this model, the smoothed particle hydrodynamics (SPH) is used based on the kernel function and the time step which takes into consideration to the fluid domain in accordance with the discrete element method (DEM) with resistance function. The interaction between fluid and DPs consists of three parts, which are repulsive force, viscous shear force and attractive force caused by the capillary action. The numerical simulation of droplet collision on DPs presents the whole process of droplet motion. Otherwise, an experimental data were conducted to record the realistic process for verification.

Findings

The comparison result indicated that the numerical simulation is capable of capturing the entire process for droplet collision on DPs.

Research limitations/implications

However, based on the difference of experimental environment, type of the DP and setups, the maximum spreading dimeters of could not fit the experimental data exactly.

Originality/value

In sum, the coupled SPH-DEM method simulation shows that the coupled model of SPH-DEM developed an entire effectiveness process for fluid–solid interaction problem.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 28 no. 11
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 11 July 2018

Xin Liu, Yuming Xing and Liang Zhao

The purpose of this study is to investigate structure parameters that influence the mixing process of droplets-gas in underwater depth-adjustable launcher cooling chamber and help…

Abstract

Purpose

The purpose of this study is to investigate structure parameters that influence the mixing process of droplets-gas in underwater depth-adjustable launcher cooling chamber and help engineers who design the launcher to distinguish the most important factor that impacts mixing performance in the cooling chamber.

Design/methodology/approach

Euler–Lagrangian droplet tracking method was used to simulate droplets-gas mixing process in the cooling chamber. The SST k-w model was adopted to simulate turbulence. Droplet breakup was described by KHRT hybrid model using modified contains which are more fit to the supersonic main flow condition.

Findings

The results show the counter-rotating vortex pairs which caused by injected liquid accelerate the mixing process. High-pressure supersonic freestream makes the liquid jet break into more small droplets due to the high momentum of the main stream. Axial injection angle has the greatest influence on Sauter mean diameter (SMD). Penetration height, SMD and total pressure loss slightly change in different tangential injection conditions. However, mixedness decreases with reduction of tangential injection angle due to a more limited space for spray developing. Enlarging orifice diameter raises penetration and mixedness greatly, while SMD and total pressure loss increase slightly.

Originality/value

The findings of this study confirm the key structure parameter to improve mixing performance in the cooling chamber. Engineers who design the underwater depth-adjustable launcher can refer the findings in this study to make control of launching power more accurate.

Details

Engineering Computations, vol. 35 no. 5
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 15 June 2015

Wenchao Zhou, Drew Loney, Andrei G. Fedorov, F. Levent Degertekin and David W. Rosen

– The aim of this paper is to advance the understanding of the droplet deposition process to better predict and control the manufacturing results for ink-jet deposition.

Abstract

Purpose

The aim of this paper is to advance the understanding of the droplet deposition process to better predict and control the manufacturing results for ink-jet deposition.

Design/methodology/approach

As material interface has both geometric and physical significance to manufacturing, the approach the authors take is to study the interface evolution during the material joining process in ink-jet deposition using a novel shape metric and a previously developed powerful simulation tool. This tool is an experimentally validated numerical solver based on the combination of the lattice Boltzmann method and the phase-field model that enabled efficient simulation of multiple-droplet interactions in three dimensions.

Findings

The underlying physics of two-droplet interaction is carefully examined, which provides deep insights into the effects of the printing conditions on the interface evolution of multiple-droplet interaction. By studying line printing, it is found that increasing impact velocity or decreasing fluid viscosity can reduce manufacturing time. For array printing, the authors have found the issue of air bubble entrapment that can lead to voids in the manufactured parts.

Research limitations/implications

The array of droplets impinges simultaneously, in contrast to most ink-jet printers. Sequential impingement of lines of droplet needs to be studied. Also, impingement on non-planar surfaces has not been investigated yet, but is important for additive manufacturing. Finally, it is recognized that the droplet hardening mechanisms need to be incorporated in the simulation tool to predict and control the final shape and size of the arbitrary features and manufacturing time for ink-jet deposition.

Practical implications

The research findings in this paper imply opportunities for optimization of printing conditions and print head design. Furthermore, if precise droplet control can be achieved, it may be possible to eliminate the need for leveling roller in the current commercial printers to save machine and manufacturing cost.

Originality/value

This work represents one of the first attempts for a systematic study of the interface dynamics of multiple-droplet interaction in ink-jet deposition enabled by the novel shape metric proposed in the paper and a previously developed numerical solver. The findings in this paper advanced the understanding of the droplet deposition process. The physics-based approach of analyzing the simulation results of the interface dynamics provides deep insights into how to predict and control the manufacturing relevant outcomes, and optimization of the deposition parameters is made possible under the same framework.

Details

Rapid Prototyping Journal, vol. 21 no. 4
Type: Research Article
ISSN: 1355-2546

Keywords

Article
Publication date: 16 November 2012

Gerard Cummins and Marc P.Y. Desmulliez

The purpose of this paper is to present an exhaustive review of research studies and activities in the inkjet printing of conductive materials.

8871

Abstract

Purpose

The purpose of this paper is to present an exhaustive review of research studies and activities in the inkjet printing of conductive materials.

Design/methodology/approach

This paper gives a detailed literature survey of research carried out in inkjet printing of conductive materials.

Findings

This article explains the inkjet printing process and the various types of conductive inks. It then examines the various factors that affect the quality of inkjet printed interconnects such as printing parameters, materials and substrate treatments. Methods of characterising both the inkjet printing process and the electrical properties of printed conductive materials are also presented. Finally relevant applications of this technology are described.

Originality/value

Inkjet printing is currently one of the cheapest direct write techniques for manufacturing. The use of this technique in electronic manufacturing, where interconnects and other conductive features are required is an area of increasing relevance to the fields of electronics manufacturing, packaging and assembly. This review paper would therefore be of great value and interest to this community.

Article
Publication date: 21 December 2022

Qianqian Cao, Lujuan Li, Hao You and Hao Liu

The contact behaviors of droplets on confined surfaces influence significantly their dynamics and morphological transition induced by the electric field. This paper aims to delve…

Abstract

Purpose

The contact behaviors of droplets on confined surfaces influence significantly their dynamics and morphological transition induced by the electric field. This paper aims to delve into the electric stress, electric field distribution, flow field and evolution of droplet neck to understand the underlying mechanisms.

Design/methodology/approach

Electrohydrodynamics of droplets in confined environment is numerically analyzed based on finite volume method (FVM) combining with volume-of-fluid (VOF) method for two-phase interface capturing. Numerical solutions are obtained through solving electrohydrodynamics model coupling fluid dynamics with electrostatics.

Findings

It was found that the droplet neck with high interfacial curvature undergoes different transition depending on the contact angle. At large domain height, the droplets on the surfaces with the contact angle of θ < 90° tend to break up into smaller droplets adhered on top and bottom surfaces. The detachment of droplets is identified when the contact angle is much greater than 90°. Notably, the droplets at θ = 90° exhibit asymmetrical shape evolution, but for other cases there is symmetrical shape of droplets during transition process. With decreasing the domain height, no obvious deformation through driving the contraction of the droplet neck is observed.

Originality/value

It remains unclear how the electric field parallel to the surfaces affects the shape transition and electrohydrodynamics of confined droplets when changing the contact angle. In this paper, the authors study the electrohydrodynamics of droplets in confined space when the electric field is exerted parallel to contact surfaces. In particular, the authors consider the effect of the surface wettability on the droplet deformation. The problem is solved through FVM combining with the VOF method to implement the capturing of two-phase interfaces. The results indicate that the electrohydrodynamic behaviors of droplets are sensitive to the contact properties of droplets on the surfaces, which has not been reported in previous works.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 33 no. 5
Type: Research Article
ISSN: 0961-5539

Keywords

1 – 10 of 662