アルミナ微粒子噴射による表面形状変化

The uniformity of cooling affects the organizational properties and product quality of the L-beam. Problems such as bending deformation of the L-beam and excessive residual stresses inside the finished product are mainly caused by uneven cooling. The jet angle is an important cooling parameter in the cooling process of L-beam. In this study, the flow field and cooling law during jet cooling of hot-rolled L-beams were investigated by means of numerical simulation using the jet angle as a variable. The jet angle is −45°∼30° on the lower surface of the short edge of the L-beam due to space limitation, and the jet angle is −45°∼45° on the rest of the parts, and the other process parameters are kept unchanged. The velocity distribution, pressure, water flow, and temperature distribution on the cooling surface and the average heat transfer coefficient were analyzed. The results show that the jet angle has a significant effect on the cooling of each part of the L-beam. With the increase of the jet angle, the asymmetry of water velocity, pressure distribution, water flow distribution, and temperature distribution on the surface of the cooling surface increased significantly. The distribution of heat flux corresponds well to the distribution of temperature. As the jet angle increases the surface average heat transfer coefficient gradually decreases, and the maximum average heat transfer coefficient appears in the vertical jet. Gravity will also have a certain effect on the cooling of the L-beam.

To clarify the effects of jet angle on the radiated sound from the flute, the radiated sound and jet fluctuations were experimentally investigated. An artificial blowing device with an artificial oral cavity was used to change the jet angle and the geometric edge offset (the relative height of edge from the jet oscillation center) independently. The actual jet offset was estimated based on the velocity profile measured by a hot-wire anemometer. Although the geometric edge offset was set to zero, the actual edge offset increased with the jet angle since the jet deflects toward inside the resonator. The radiated sound pressure of the first mode remained almost at the same level, while the sound of the second mode radiated more intensely with the increase of the jet angle in the range of 15 degrees from the measured angle for a human player. With the increase of the jet angle beyond this range, the sound of the third mode radiated less intensely. These results indicate that jet deflects toward inside the resonator influenced by the acoustic resonance and that the variation of the jet angle affects the actual jet offset, which affects the harmonic structure.

Introduction Bicuspid aortic valve (BAV) is the most common congenital valve defect. It consists in the fusion of two aortic valve leaflets, and it is associated with a high prevalence of proximal aorta dilation. Dilation is highly prevalent (around 30%) in BAV patient relatives with a tricuspid valve (TAV) identified by echocardiography. However, the presence of partial aortic valve leaflet fusion (also called mini-raphe or forme fruste BAV, see figure 1A) is easily missed by echocardiography. A recent study reported that 44% of patients from a small cohort of BAV patient relatives with aortic dilation followed by CT showed mini-raphe. Purpose We aimed to use 4D flow CMR to assess if the presence of mini-raphe is associated with aortic flow alterations, which may be concurs in the etiology of aortic dilation in BAV patient relatives. Methods Twenty BAV patients first-degree relatives with partial fusion (<50%) of aortic valve leaflets and proximal aorta dilation were identified by CT or cine CMR and prospectively included. One-hundred twenty-five BAV and 95 patients with TAV from our prospective dataset of 4D flow CMR were included for comparison. Propensity score matching was used throughout the study to correct the comparisons between mini-raphe and BAV and mini-raphe and TAV patients for differences in age, maximum aortic diameter, sex, height, weight, proximal aortic pulse wave velocity and, only for BAV, fusion pattern. The hemodynamic parameters previously related to aortic dilation were computed. They were jet angle, normalized flow displacement and systolic flow reversal ratio (SFRR, identifying through-plane vortexes) were computed and compared in the ascending aorta and in the aortic arch. Results The presence of mini-raphe was statistically-significantly associated with increase in jet angle (Figure 1B), flow displacement (Figure 1C) and vortexes (Figure 1D) in most of the ascending aorta and aortic arch when mini-raphe patients were compared with TAV patients. The severity of flow asymmetry found in mini-raphe patients was lower than the one characteristic of BAV patients, but vortexes were even higher in a small region at the distal ascending aorta. Figure 1 Conclusion Partial fusion of the aortic valve leaflets is related to increase in proximal aorta flow eccentricity and vorticity. These flow abnormalities are not as marked as those associated with BAV. Data regarding prevalence of mini-raphe as evaluated with CT or cine CMR are needed, especially in familiar of BAV patients. Acknowledgement/Funding European FP7/People 267128; Spanish Ministry of Economy and Competitiveness RTC-2016-5152-1 and Instituto de Salud Carlos III PI14/0106

Influence of moving plate velocity on conjugate heat transfer due to the impingement of an inclined slot jet

With inner and outer filter parts having the advantage of a more compact structure and a larger area of a single filter cartridge, a three-dimensional numerical simulation model of annular filter cartridge was constructed, and the pulsed-jet performance of annular filter cartridge with array nozzle was investigated. The spatial and temporal distribution of injection pressure in filter core was analyzed; the injection flow field, the induced ratio, and the eddy current under different number (N) of nozzles were compared. The effects of jet angle (α) and jet distance (H) on the pulsed-jet intensity and pulsed-jet uniformity were examined. The results showed that the appropriate number of outlet openings for array nozzles is 4, which corresponds to the induced ratio of 310.4%. With the increase in jet angle, the pulsed-jet intensity first increases and then decreases (the optimal jet angle is α=0°), and the pulsed-jet uniformity first decreases and then increases. With the increase of the jet distance, the pulsed-jet intensity increases first and then decreases (the optimal jet distance is H=250 mm); and the pulsed-jet uniformity was improved. Compared with N=2, the array nozzle can improve the pulsed-jet intensity by 15.5% and the pulsed-jet uniformity by 4.8 times (reducing the coefficient of variation from 0.52 to 0.09) under the optimal parameters (N=4, α=0°, H=250 mm). The research provides a reference for optimizing the performance of the dust collector with annular filter cartridges in space-constrained working environments.

Study of conjugate heat transfer from the impingement of an inclined free slot jet onto the moving hot surface

Modern aero-engine and gas-turbine development imposes ever-higher demands on combustor performance. Among various combustor designs, the trapped-vortex combustor (TVC) excels in flame stability and pollutant reduction, yet suffers from insufficient heat and mass transfer between the main flow and the cavity. To address this issue, a cavity-jet combined combustor is developed by introducing a cavity structure into the jet-stabilized combustor (JSC). The aim is to preserve vortex stabilization while significantly enhancing mass and energy transfer within the combustor. Building on previous work, this paper further investigates the effects of air jet angle on the combustion flow and NO emission characteristics of a combustor with a cavity through numerical analysis. The results show that in the constricted combustor configuration, as the jet angle increases, the high-temperature zone area in the combustor decreases, while the temperature magnitude and combustion efficiency increase. The minimum NO emission occurs at a jet angle of 30°.

The fabrication process named as pulse squeeze exhaust casting was developed. In comparison with the squeeze exhaust casting the process was characterized by controlling the press applied the molten metal in the manner of pulse, so that the air in the preform was fully exhausted. By this process the 6061 aluminum alloy composites containing Al2O3 particles of 0.15μm diameter have been successfully fabricated. The tensile strengths of samples with 30 vol% Al2O3 particles were 500MPa in the as-cast and 637MPa in the extruded conditions, and the elongation of extruded one were 8% at room temperature and 32% at 200°C, respectively.

Platelet mixer is a type of high-efficient equipment which can mix fluids through platelet micro-channels by cross-bedded injection. It overcomes disadvantages that the fluid is centralized around the inlet and it improves the diffusion. In this work, the platelet mixer is used for pre-mixer in a rocket engine, and the diffusion of oxygen and air in pre-mixer is analyzed. The high speed jet leads to a strong shear force near the inlet which produces counter-rotating stream-wise vortices around the jet. The angle between the direction of jet and radial direction influences both the stream-wise vortices and diffusion. The vortices intensity increases as the angle increase from 0o to 20o.

The article examines the plasma sprayed 80Ni-20Al coatings on aluminum-magnesium (Mg ≈ 2.6‒3.6 %) alloy substrate, which before plasma spraying was cleaned using blasting with Al2O3 particles. The wear resistance and corrosion tests of sprayed coating and aluminum-magnesium alloy were performed. The volume loss, average central part of the cross-sectional area of wear track, wear rapidity, wear rate, wear resistance and corrosion current of coating and Al-Mg substrate were evaluated. The wear resistance and corrosion of nickel-aluminum coating and aluminum-magnesium substrate were compared at the work. Furthermore the wear tracks analysis of sprayed coating and substrate surface was carried out. Straipsnyje nagrinėjamos plazminiu būdu purkštos 80Ni-20Al dangos ant aliuminio-magnio (Mg ≈ 2,6‒3,6 %) lydinio substrato, kuris prieš padengiant buvo nuvalytas srautinant Al2O3 dalelėmis. Buvo atlikti purkštos dangos, aliuminio-magnio lydinio dilimo ir korozijos tyrimai. Nustatyti dangos ir Al-Mg substrato tūrio nuostoliai, vidutinis išdilusio takelio centrinės dalies skerspjūvio plotas, dilimo sparta, dilimo greitis, atsparumas dilimui ir korozijos srovė. Darbe buvo palygintas nikelio-aliuminio dangos ir aliuminio-magnio substrato atsparumas dilimui ir korozijai. Taip pat buvo atlikta užpurkštos dangos ir substrato dilimo takelių paviršiaus analizė.

Superhydrophobic ZnAl double hydroxide nanostructures and ZnO films on Al and glass substrates

The fabrication of high quality and low cost microlenses on a glass substrate using a simple, rapid, and precise direct microplotting technique is shown in this paper. The fabrication method is based on the use of a microplotter system, which is significantly different from the existing inkjet, roll-to-roll printing, and reactive ion etching technology and could work with higher viscosity materials. By optimizing the parameters of voltage, dispense time, and concentration of the polymer solution, high quality microlenses with a diameter of 20μm could be obtained. The geometrical and optical characteristics of the microlenses are analyzed by measurement of the surface profile and the imaging properties in the near-field and far-field zones as well as the diffraction pattern. We think that the fabricated microlenses could be attractive for enhancing the light extraction efficiency of light emitting diodes.

The dependence of Si3N4 etch rates and the etch selectivity of SiO2 to Si3N4 on ion-incident angles was studied for different bias voltages in a high-density C4F8 plasma. A Faraday cage and specially designed substrate holders were used to accurately control the angles of incident ions on the substrate surface. The normalized etch yield (NEY), defined as the etch yield obtained at a given ion-incident angle normalized to that obtained on a horizontal surface, was unaffected by the bias voltage in Si3N4 etching, but it increased with the bias voltage in SiO2 etching in the range of −100to−300V. The NEY changed showing a maximum with an increase in the ion-incident angle in the etching of both substrates. In the Si3N4 etching, a maximum NEY of 1.7 was obtained at 70° in the above bias voltage range. However, an increase in the NEY at high ion-incident angles was smaller for SiO2 than for Si3N4 and, consequently, the etch selectivity of SiO2 to Si3N4 decreased with an increase in the ion-incident angle. The etch selectivity decreased to a smaller extent at high bias voltage because the NEY of SiO2 had increased. The characteristic changes in the NEY for different substrates could be correlated with the thickness of a steady-state fluorocarbon (CFx) film formed on the substrates.

Vertically-oriented zinc oxide (ZnO) nanowires were synthesized on glass and silicon substrates by Pulsed Laser Deposition and without the use of a catalyst. An intermediate c-axis oriented nanotextured ZnO seed layer in the form of nanowall network with honey comb structure allows the growth of high quality, self-forming, and vertically-oriented nanowires at relatively low temperature (<400 °C) and under argon atmosphere at high pressure (>5 Torr). Many parameters were shown to affect the growth of the ZnO nanowires such as gas pressure, substrate–target distance, and laser energy. Growth of a c-axis-crystalline array of nanowires growing vertically from the energetically favorable sites on the seed layer is observed. Nucleation occurs due to the matching lattice structure and the polar nature of the ZnO seed layer. Morphological, structural, and optical properties were investigated. X-ray diffraction (XRD) revealed highly c-axis aligned nanowires along the (002) crystal plane. Room temperature photoluminescence (PL) measurements showed a strong and narrow bandwidth of Ultraviolet (UV) emission, which shifts to lower wavelength with the increase of pressure.

Fine polishing techniques, such as the chemical mechanical polishing treatment, are one of the most important technique to glass substrate manufacturing. Mechanical interaction in the form of friction occurs between the abrasive and the substrate surface during polishing, which may cause formation of latent flaws on the glass substrate surface. Fine polishing-induced latent flaws may become obvious during a subsequent cleaning process if glass surfaces are corroded away by chemical interaction with the cleaning liquid. Latent flaws thus reduce product yield. In general, non-destructive inspection techniques, such as the light-scattering methods, used to detect foreign matters on the glass substrate surface. However, it is difficult to detect latent flaws by these methods because the flaws remain closed. Authors propose a novel inspection technique for fine polishing-induced latent flaws by combining the light scattering method with stress effects, referred to as the stress-induced light scattering method (SILSM). SILSM is able to distinguish between latent flaws and particles on the surface. In this method, samples are deformed by an actuator and stress effects are induced around the tips of latent flaws. Due to the photoelastic effect, the refractive index of the material around the tip of a latent flaw is changed. This changed refractive index is in turn detected by a cooled charge-coupled device camera as variations in light scattering intensity. In this report, surface latent flaws are detected non-destructively by applying SILSM to glass substrates, and the utility of SILSM evaluated as a novel inspection technique.