Wei Hsiang Lai

Manufacturing parts optimization in the three‐dimensional printing process by the Taguchi method

Abstract The functional requirements of three‐dimensional printing systems are speed, accuracy and the strength of the green‐part. However, these functional indices are significantly affected by the properties of the adopted materials and the manufacturing process parameters of the rapid prototyping machine. The four most important process parameters were systematically investigated in this study. Using the ANOVA analysis techniques of the Taguchi method and adjusting the shrinkage setup values, we determined the optimal parameter setup values for NCKU‐1 powder and reduced the dimensional accuracy error to ±0.08 mm, ±0.07 mm and ±0.06 mm in the X‐, Y‐and Z‐direction, respectively. The results also show that these optimized parameters can shorten building time by 9.57% and increase flexural stress by 31.27%. Finally, the quality properties were also examined separately for ZP 100 and NCKU‐1 powder. It is concluded that building time decreased by 16.5%, binder consumption was reduced by 35.4% and flexural stress increased 172.88% if the powder was changed from ZP 100 to NCKU‐1.

The new expression of the effectiveness of powder classification

Abstract In this paper, the authors try to propose a new index—‘the classification size ratio (CSR)’ —which is defined as CSR = (Dv(10) of the coarse part)/(Dv(90) of the fine part). The CSR can be used to judge effectiveness of separation between coarse and fine powder. If CSR ≥ 1, it represents the classification to be considerably good in separating into two groups of powder; however, if CSR

Atomization and Mixing Characteristics of an Unlike-Doublet Impinging-Jet

The spray characteristics of an unlike-doublet impinging-jet is investigated in this work. The working fluids are purified civil water and 95% alcohol-water solution. Impingement angle is 60°. The injector is made of stainless steel and with orifice diameter of 0.5mm. Results show that spray patterns of the unlike-doublet impinging-jet are quite different to that of likedoublet. That is caused by difference in physical properties of the two impinging jets. Mean drop size, measured by using a light diffraction particle sizer, has a peak value along the axis through the impingement point. And an asymptotic value of 50 μιη in drop size is approached when jet velocity is elevated high enough, that is, the same as the like-doublet impinging-jet. The variation of deviation angle with jets momentum ratio is quite a match with the theoretical derivation. Results of mixture ratio show that jets will penetrate through each other at the impingement point.

SIMULATION OF PIEZOELECTRIC JELLYFISH POWER GENERATOR

The energy problem is getting increasingly serious. As such, unused energy recovery technology is crucial for environmental protection, which has been investigated extensively. Several methods have been developed to utilize scavenged energy from the environment, such as waste heat, solar energy, wind energy, and tides energy to convert into useful power. There is a new idea of piezoelectric jellyfish generator which combines the utilization of sea wave and vibration energy. When sea wave passes through the jellyfish, the wave causes the tentacles to vibrate. The tentacles is made of piezoelectric polymer which can convert the strain energy into electrical energy. This paper discusses about the piezoelectric jellyfishs tentacles being disturbed by wave in the sea. We employed the commercial CFD software CFD-ACE+ 2006 to simulate this phenomenon. The parameters including its tentacle length (L) and wave propagating function (Y) are studied which affect the piezoelectric jellyfish capacity to generate power.

Energy Form of Cone-Jets in Electrohydrodynamic Atomization

Abstract Electrohydrodynamic atomization (EHDA) differs from conventional atomization methods by introducing the Coulomb force, which allows enhanced droplet-size minimizing and mono-dispersion. In this paper we report on such cone-jets experimentation from the energy point of view. Ethanol-liquid solutions of wide-range concentrations are used. The results demonstrate at least three submodes in energy ratio of kinetic energy to surface energy increments.

The simulation of the piezoelectric print head

This paper investigates the flow dynamic behaviors with respect to different contact angle and frequency of the piezoelectric print head. Its geometric model is divided into three zones for easy description, i.e., channel zone, nozzle zone and ejection observing zone. The length, width and orifice diameter of the micro-channel are 2,000 µm, 400 µm and 30 µm, respectively. The moving wall is located on the top wall of the channel zone in order to obtain proper condition for single drop generation; we applied the numerical simulation by commercial CFD software – CFD-ACE+ 2004. The most important purpose of this study is to find out the optimal frequency to eject droplets periodically and control the volume of droplet ejection which may provide reference for experimental work later on. The results show that by fixing the frequency 20KHz, the nozzle contact angle is from 20 degree to 80 degree, the one droplet interval time value is less than 0.1% and the droplet size value is less than 1%. According to this result, we find that the effect of contact angle is not very important. Also for the frequency value from 50KHz to 100KHz, the first shot time is almost the same.

The thermal image analysis and fuel conversion characteristics on porous media-catalyst hybrid reactor in dry auto-thermal reforming

The subject was to design a fuel converter of CO2, focusing on parameters on thermal image observation of porous media-catalyst interface during excess enthalpy reforming process. The methodology was using auto-thermal reforming technique to provide the heat of oxidation reaction. The heat provided the needed high temperature during CO2 reduction processing. H2-rich syngas was produced by the assistance of surface reaction of catalyst. The experiments were performed by using visualization technique for thermal image observation during reforming process. The results could be applied to the understand the temperature distribution. This study covers two parts, including thermal image observation, and reactant conversion characteristics under various reforming parameters. The experimental results show that the hybrid reformer can achieve excess enthalpy condition under the tested parameters. Additionally, the optimal CH4 conversion efficiency can reach 93.28 %. CO2 conversion efficiency is reaching between 0.35 and 8.65 %. The thermal image observation technique to determine catalyst local high temperature of reforming process is important in academic and practical application. Moreover, it provided information for basic research during reforming process

Initial Temperature Effect on Detonation Initiation of JP-8-Oxygen Mixtures

The experiment has been classified two parts. One is design and set-up of spray system, the flash-boiling mechanism was used to heat the fuel. The viscosity and surface tension will be reduced for obtaining the smaller droplet diameters. The test result shows that the droplets with a size below 10 μm can be obtained when the fuel pressure increased to 6MPa and the fuel temperature was 373 K. Comparing with non-heated fuel, the fuel pressure was reduced 2 MPa to reach the same threshold. The other is the experiment of detonation initiation at different initial temperatures. The database software of NIST SUPERTRAPP was used to calculate the vapor content in different surrounding temperature and pressure conditions. When the heating temperature was 373 K, the condensed fuel could be observed in the tube’s bottom. The fuel vapor content is not enough to induce the reaction and leads the detonation initiation failing. At other temperatures, the detonation wave was successful generated, and the properties were similar to one,s by igniting the gaseous propane.

Experimental study on transmission of an overdriven detonation wave across a mixture

Two sets of experiments were performed to achieve a strong overdriven state in a weaker mixture by propagating an overdriven detonation wave via a deflagration-to-detonation transition (DDT) process. First, preliminary experiments with a propane/oxygen mixture were used to evaluate the attenuation of the overdriven detonation wave in the DDT process. Next, experiments were performed wherein a propane/oxygen mixture was separated from a propane/air mixture by a thin diaphragm to observe the transmission of an overdriven detonation wave. A simple wave intersection model showed that the rarefaction effect must be included to ensure that the post-transmission wave properties are not overestimated. The experimental results showed that the strength of the incident overdriven detonation plays an important role in the wave transmission process. After the wave transmission process, the propagation of the detonation directly correlates with detonability limits.

TURBULENCE MODULATION MEASUREMENTS IN A CHARGED MONODISPERSED DROPLET STREAM

As reported in the study of Chang et al. (2003), the modulation of the carrier-phase turbulence, that is, the effect of the presence of dispersed phase on the turbulence structure, is heavily dependent on the term of . Nevertheless, very little experimental data on can be found in the literature. In this study, a monodispersed droplet stream, instead of polydispersed spray, is generated using a monosized atomizer. However, the occurrence of breakup or coalescence due to droplet collisions in the stream downgrades the uniformity of droplet size in the downstream. To avoid this, the electrohydrodynamic (EHD) technique is used. Monodispersed droplets can be made toward a rigid body after charging the electrons. When charged droplets move closer, the coulomb force will keep the droplets distant from one another and avoid the occurrence of droplet breakup or coalescence. Measurements of droplets’ velocity and size in a turbulent stream are made using a particle dynamic analyzer (PDA). Quantities of and k can be computed using the measured velocities of both carrier and dispersed phases.