Toshiaki Yano

Microscopic Spray Characteristics in the Effervescent Atomizer with Two Aerator Tubes

An experimental study is performed on atomization characteristics and stable operating conditions for the injection of high viscous waste vegetable oil using an effervescent atomizer with 2 aerator tubes. Consideration is given to the effects of ALR and liquid viscosity on the velocity and mean diameter of the injected droplet. It is found that (i) as ALR increases, the axial velocity of the droplet is increased, while half-velocity width and SMD are decreased regardless of the change in liquid viscosities, (ii) the rate of fine drop distribution occupied in the total spray field is increased with an increase in ALR, and (iii) the effect of viscosity on the atomization characteristics is minor. Consequently, it is expected that the effervescent atomizer will exhibit an excellent atomization performance at the high ALR condition, regardless of liquid viscosities.

Satellite analysis and mesoscale behaviour of volcanic plumes and gas from Miyakejima, Japan

Miyakejima plumes of ash-rich and vapour-rich clouds were detected well by the NOAA/AVHRR data, and the height of eruption cloud on 29 August 2000 was estimated reasonably using the brightness temperature at 11 µm of NOAA/AVHRR and the upper air data taking into account the effect of ash emissivity. We found two different mechanisms which bring the high concentration SO2 to the mainland of Japan: convective daytime mixing brings gas down to the surface, after advection from Miyakejima in the upper air by winds associated with high pressure system; and the volcanic gas descends to the island surface in strong winds associated with stationary fronts and low pressure systems.

Temporal behaviour of Asian dust aerosols observed in 2001 using meteorological satellite data

The advection and dispersion of Asian dust events from China and Mongolia to the Pacific Ocean around Japan in the spring of 2001 were investigated using meteorological satellite data, NOAA/AVHRR and GMS-5/VISSR. Aerosol Vapour Index (AVI) images, taking the brightness temperature difference between 11 and 12 _m, are very effective in monitoring the Asian dust phenomenon in the east Asian region, because of their capacity for night-time detection. Time-series GMS AVI images, at three hourly intervals, are useful in making clear the dynamic behaviour of Asian dust. The satellite images are well reproduced by the online dust tracer model, CFORS, coupled with a regional-scale meteorological model.

Theoretical and experimental study on suspended circular disk motion in centrifugal casting device

Functionally Graded Materials are high performance composite materials, in which physical and/or chemical properties of these material structures are graded in the several directions. Centrifugal solid-particle method is one of the effective fabrication methods by use of centrifugal casting devices. The casting mold that includes reinforcement particle and molten metal are centrifuged and particles move in the mixture due to density differences of these materials. However, there is no information on the particle motions. The aim of the present study is to disclose on suspension particle motion in the axially rotating drum. The particle velocity of the circular disk is measured by PTV (Particle Tracking Velocimetry) method and is theoretically predicted by BBO (Basset-Boussinesq-Ossen) equation. It is found that (1) each particle motion is affected by the rotating speed, (2) the measured velocity is compared with theoretical result, and (3) when the particle moves in the Stokes’ regime, its velocity is linearly increased with the distance from the center of the drum and this trend is intensified with an increase in the rotating speed.Copyright

Atomization Characteristics of Effervescent Atomizer With Two-Aerator Tube

An experimental study was conducted to investigate the atomization characteristics of spray from the effervescent atomizer, which has two-aerator tube. The atomization characteristics were examined through the influence of ALR (Air-to-Liquid Ratio) and the changes of atomizer geometry (nozzle orifice diameter, diffusion angle, mixing chamber volume). PDPA (Phase Doppler Particle Analyzer) was used to evaluate the SMD (Sauter Mean Diameter) and droplet velocity. During the experiments, the mass flow rate of liquid was kept constant at 2.8g/s and the mass flow rate of atomizing air was changed from 0.2 to 0.6g/s. Experimental results showed that SMD is not a linear function of ALR. While SMD is very sensitive to the changes of ALR, the changes of atomizer geometry have little effect on droplet mean diameter. As the effervescent atomizer with two-aerator tube is insensitive to the changes of atomizer geometry, it is expected that the effervescent atomizer with two-aerator tube is capable of requirements of many applications, without the drawbacks of atomization characteristics.Copyright

Transport phenomenon of two-dimensional circular particle moving in axially rotating drum filled with viscous fluid

Several processing techniques have been proposed for the fabrication of functionally graded materials (FGMs), whose composition and microstructure, i.e., the chemical and physical properties vary in the specific direction. The mechanical property of FGMs is affected by dispersed particle size, volume fraction of the particle, and particle orientation. In order to clarify its property, it is important to disclose the particle motion during the fabrication process. In this study, two-dimensional circular particle motion during fabrication of Functionally Graded Materials is studied using the cold model centrifugal casting. Consideration is given to the tiinewise variation of the radial circulardisk motion in the axially rotating cold water drum. The velocity measurement is carried out by means of the Particle Tracking Velocimetry (PTV) method and the measured value is compared with that estimated by the theoretical prediction. It is found that (i) as the disk moves toward the rotating wall, its motion is perpendicular to the wall, and (ii) the measured velocity is in good agreement with compared with the theoretical one.

Flame Blowoff Limit Phenomenon of Turbulent Jet Diffusion Flames With Annular Counterflow

The present study deals with the transport phenomena of turbulent jet diffusion flames with air-suction flow and the possibility of extending the flame blow-off limits through the shear stress augmentation using the annular counterflow technique. The experimental apparatus employed here comprises a fuel nozzle placed at the center of a concentric annulus with an outer cylinder adopted to encompass the nozzle. Fuel jet is allowed to eject upwards and turbulent jet diffusion flames are formed by igniting the jet and by increasing the volume flow rates of fuel. It is found that (1) the augmentation of turbulent shear effect exerted on the shear layer formed between the jet flames and the opposed flow of air causes an extension of flame blowoff limits, (2) by using the annular counterflow technique, the flame lift-off height is suppressed than the normal diffusion flame, and (3) its height is correlated using the effective air-suction momentum flux proposed here.Copyright

Visualization of Timewise Luminosity Fluctuation of Jet Diffusion Flames

Free jet diffusion flame photographs were taken by high-speed video camera. Propane was used as fuel. Flame images are digitized into 24-bit full color images by using commercial software. The digital color image is decomposed into 8-bit images of the Red, Green and Blue components and moreover each component is converted into decimal ASCII data by means of our program. In this study, the Red component luminosity fluctuation is investigated for five different fuel exit velocities. The ASCII data of 3000 frames are stored into Microsoft Excel and the time-averaged value and fluctuation intensity of luminosity are calculated by our program based on the Visual Basic Applications Edition (VBA) in Excel. These results are recomposed into 8-bit BMP images and visualized as the density slicing pseudo color images.

Thermal transport phenomenon of unsteady marangoni flow in a square cavity under reduced gravity

A numerical study is performed on unsteady natural convection heat transfer and fluid flow in a cavity under reduced gravity. Consideration is given to the influence of Marangoni convection on the thermal and velocity fields in a twodimensional square cell. Here, it consists of two opposing vertical side walls held at constant but different temperature with the horizontal lower wall insulated and the upper face treated as non-deformable adiabatic free surface. The governing equations are discretized by means of a finite-difference technique and numerically solved. The fluid temperature gradient in the cavity in the absence of Marangoni force under the reduced gravity is substantially decreased near the hot and cold vertical walls and the dominant heat transfer mechanism switches from convection into conduction, as time progresses. On the contrary, the corresponding flow pattern and isotherms are similar to that under normal gravity condition, resulting in a slight deterioration of the heat transfer performance, if Marangoni force drives the flow in the cavity. Therefore the unsteady natural convection in the system considered is affected

Formaldehyde and acetaldehyde in exhaust gases emitted from an ethanol fueled S. I. engine. Clarification of the formation conditions with a reactor experiment.

一定温度に保持した反応管を用いて,排気ガスの反応実験を行った。アセトアルデヒドおよびホルムアルデヒドはガス温度が750～850 K, 滞留時間が50ms前後において顕著な濃度増加を示す。未燃エタノールの参加に伴い,アセトアルデヒドがホムルアルデヒドよりわずかに速く生成され,HCがそれらに続く。アセトアルデヒドの濃度増加は空燃当量比の影響をほとんど受けないが,ホルムアルデヒドは希薄になるにしたがい増加する。