Papers by Keyword: Spray

Abstract: In the fabrication of fuel cell electrodes, applying catalyst ink onto a substrate is crucial. The performance of the proton exchange membrane fuel cell (PEMFC) is subsequently impacted by how the catalyst is applied onto substrate as well as in terms of its resulting morphology. In this study, a direct catalyst ink spraying approach was done in order to investigate transfer efficiency and surface morphology for different concentrations of ink. The concentration of catalyst ink used in the spraying process are 0.5, 1.0, 1.5, 2.0 and 2.5 mg/ml with fixed loading of 1.0 mg/cm². The transfer efficiency of the catalyst inks was calculated neglecting human error during spraying. The coating thickness and distribution of the resulting catalysts were analysed via Field Emission – Scanning Electron Microscope (FESEM).

Abstract: The purpose of this study was to achieve a low-porosity HVOF (High velocity Oxygen Fuel) spray cover and to determine the effect of spray parameters on the porosity of the coating. The spray parameters studied include: Powder feed rate (A); Spray distance (B); Oxygen/Propane ratio to porosity of WC-12Co coating on 16Mn steel. Taguchi method and ANOVA (Analysis of variance) technique were used to optimize and analyze the effect of spray parameters. The results showed that the optimum spray parameters with A = 26 g/min, B = 0.2m, C = 5 for porosity smallest. Factor A has the greatest influence on porosity, followed by B and C. The experimental result is then compared to optimal results and the error is only 4.2 %. Hence, one can say that the optimal results are reliable and Taguchi method - ANOVA technique proved to be an effective solution to the optimization problem. Parameters for a WC-12Co coating with improved porosity on 16Mn steel substrate have been identified.

Abstract: Nowadays, thermal spray coatings are used to enhance mechanical properties of the material. One of the technologies used to produce thermal spray coating is HVOF spray technology. This is the most advanced and modern technology which has been widely used in the industry due to its flexibility and ability to create coatings with better adhesion in comparison with other thermal spray methods. This article presents some empirical findings from applying the 67Ni18Cr5Si4B alloy powder coating onto C 45 steel shaft by HVOF spray technology. It also analyzes the influence of some technological parameters on the adhesion of the coating. As a result, the parameters of HVOF spray technology are obtained suitable for recovering worn axis-sized workpieces.

Abstract: In this study, Zinc oxide (ZnO) undoped and Lanthanum doped (ZnO: La) thin films were deposited on 400°C heated glass using spray pyrolysis technique with moving nozzle. The components (Zn (CH₃COO)2, 2H₂O) and (LaCl₃, 7H₂O) were used as sources to produce ZnO thin film and doped Lanthanum, respectively. Effects of dopant on the optical and structural properties of undoped and 0, 2 and 4 wt. % Lanthanum doped ZnO thin films were studied. Optical transmittance spectra of the films showed high transparency of about 98% in visible region. The optical gap for ZnO and 0, 2 and 4 wt. % La doped ZnO thin films were found to be in 3.25-3.28 [eV] range. The X-ray diffraction showed that the thin films have hexagonal wurtzite structure with a strong (002) as preferred orientation, whereas the crystalline size was ranged in 15.89-33.45 nm. The ZnO thin films are promising to be used a light emitting diodes, gas sensor and UV detectors applications.

Abstract: Polymer membranes with fixed pore size or narrow pore size distribution can be used for special separation. However, polymer membranes prepared by conventional method usually have wide pore size distribution and the pore size is hard to control. Here we prepared a porous polymer membrane with uniform pore size via spraying a blend of polystyrene (PS) and polyethylene oxide (PEO) on a filtration paper. Dissolving the water-soluble component (PEO) forms the pore and varying the ratios of PEO in the blend controls the pore size. The pore size and size distribution are also affected by processing parameters, such as the flow rate of solution and carrier gas, and gap length. The morphologies of the membrane are observed using scanning electron microscopy (SEM). The novel polymer membrane with controllable and uniform pore size will be used for the separation of solutes with predictable sizes.

Abstract: Microscopic observation and testing were carried out on the structure & texture, bonding form and performances of different plasma-sprayed ceramic coatings on the wear surface of Cr12MoV dies by KYKY-2800B SEM. The result indicates that the bonding between the coating and the die matrix surface is mainly of mechanical form, the bonding strength of coating is higher than that of the matrix material, the coating has a low structural porosity and the hardness and friction performance of the die surface are somewhat improved. Compared with the original dies, not only their dimensional accuracy and quality standard are no lower but also their performance such as wear resistance and corrosion resistance are better, fully satisfying the requirements of die repair & remanufacture.

Abstract: Atomization quality of liquids has a great importance on the performance of combustion engines. In this study the internal flow phenome of pressure swirl atomizer is investigated by using numerical method. The design of swirl atomizer is performed based on the requested atomizer characteristics which are sauter mean diamer (SMD), spray cone angle and break up length. Prediction and understanding of liquid film dynamics in the atomizer inside are the fundamental ways to explore atomizer performance. The purpose of this study is to estimate the air core size and film thickness in pressure swirl atomizer by setting single phase numeric computations. This article concludes that the CFD validated swirl atomizer design can be achieved with the lower computational cost using stream function methodology.

Abstract: A great difficulty in spray analysis is the intrinsic subjectivity in the manual measurements of macroscopic spray characteristics. Within its contexts this work has the main objective to demonstrate a systematic methodology for the spray analysis adopted for acquiring the data results based on numerical criterion dealing with the numerical matrices that represent the spray images. The results shown in this work refers to EXXSOL D60 injection, a tested fluid used to simulate ethanol spray characteristics. The characteristics analyzed were spray penetration, spray pattern at various moments after start of injection and the total volume of the cone spray also as a function of time. The methodology applied uses the numerical matrices of images in different stages of injections. A computational routine written in Matlab environment deals with the numerical matrices of the spray images to localize the spray boundaries based on a numerical criterion. All the subsequent analysis is then performed with the boundaries location data in hand. The results show higher growth of penetration in the beginning of injections, higher displacements of the bottom part of the spray also in the beginning of injections and a linear growth of spray volume injected. The importance of all the results acquired in this work demonstrated that the proposed methodology is suitable for spray analysis.

Abstract: This study presents a methodology to validate CFD simulations of the spray fuel injection using an experimental bench and optical measurement tools along with the Shadowgraph Technique. The parameter used for validating the experiments is the penetration rate, under situations of 6 bar and 100 bar injection pressures. The results show a penetration rate difference lower than 3% between the numerical model and the physical test. The visual plots, considering the shape and angles of the spray, also matched. Once validated, the numerical model could be applied to dynamic models of internal combustion engines and used to elaborate injection strategies for future projects.

Abstract: Coal is currently the most widely used and most abundant fossil fuel in the world. It is primarily used for generating electricity at power plants. However, due to problems of pollution and energy consumption, importance has been placed on the development of clean coal technology. Coal-water slurry (CWS), consisting of fine coal and water mixture, is a liquid fuel used to replace heavy fuel oil for boilers and entrained flow gasifiers. Since CWS is a liquid with high viscosity and regular atomizing burners are designed for the use of fossil fuels with low viscosity, it is necessary to design high efficiency atomizing burners specific for CWS. As viscosity is a key factor for atomization characteristics, we used silicon oils of different viscosity as the testing liquids, to study the effect of different atomization parameters on the atomization characteristics. Our results show that, when the gas to liquid ratio (GLR) is high, the existing particle velocity at the central axis is lower than low GLR condition; likewise, the velocity at radial positions is higher of the high-viscosity case. The velocity also increases as the radial distance further increases away from the axis. And decrease as the GLR increases. On the other hand, the distribution of the velocities does not change after the radial distance reaches a certain limit. This limit decreases as the axial length increases. Increasing viscosity increases the inertial force of the liquid fluid, so the momentum of the atomization gas needs to be increased for it to generate enough shear stress on the fluid and to enhance the atomization characteristics.