• Journal of Biosystems Engineering
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• v.31 no.3 s.116
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• pp.153-160
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• 2006

This study was performed to evaluate some geometrical characteristics of disc type swirl nozzles and to develop nozzles having improved spraying performance for knapsack sprayers. Considered geometrical characteristics of the nozzles were disc thickness, orifice diameter, swirl chamber diameter and shape of the swirl chamber (nozzle chamber). 3 types of nozzle cores were compared. Main results of this study were as follows. 1. Spraying angle (A) was increased with decreasing disc thickness (x), and with increasing orifice diameter (y) or spraying pressure (z). The equation was as a follow. $$A=3.95\frac{1}{x}+73.50\sqrt{y}+18.97\sqrt{z}-60.16$$ 2. Spraying flow rate (F) was increased with decreasing disc thickness (x), and with increasing orifice diameter (y) or spraying pressure (z). The equation was as a follow. $$F=-89.95x+611.09y+620.49\sqrt{z}-868.20$$ 3. Mean spraying droplet size (V) was decreased with decreasing disc thickness (x), with increasing orifice diameter (y) in low spraying pressure, with decreasing orifice diameter (y) in high spraying pressure, and with increasing spraying pressure (z). $$V=148.77x^4-746.85x^3+1311.76x^2-917.31x$$ 4. The spray pattern was compared using CV values. The CV value of the nozzle core type 1 was 26.7% in spraying pressure $3\;kgf/cm^2$, the CV value of the core type 2 was 23.6% in spraying pressure $2\;kgf/cm^2$, the CV value of the core type 3 was 20.6% in spraying pressure $1\;kgf/cm^2$. 5. Minimum spraying pressure was improved from $1.5\;kgf/cm^2\;to\;1.0\;kgf/cm^2$ by changes of nozzle core shape.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.2349-2351
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• 2003

This paper reports a novel microfluidic system, by which microfluidic delivery, transport and control can be digitally realized in femtoliter scale. Microelectronic grade $N_2$ from a pressurized canister was passed through HPLC tubing into a micro injector. The micro injector was driven and controlled digitally by the control system that can apply various control parameters such as pulse frequencies. A front-end of micro nozzle was inserted the dyed oil to collect droplets injected. The diameter of a droplet was measured by a microscope and a CCD camera, and then its volume can be calculated on the assumption that the droplet is spherical. The micro nozzles were simply pulled in glass capillary tubes by the micro puller self-made, and the geometry parameters of the micro nozzles can be adjusted easily. Experiments have successfully been carried out, and the results demonstrated that the proposed digital micro injector possesses three significant advantages : precise ultra-small liquid volume in femtoliter scale, digital microfluidic control and micro devices fabricated by simple glass process, not based on IC process.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.3
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• pp.187-197
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• 1998

To investigate the spray behavior and atomization characteristics using an air-assist injector, spray visualization and PDPA measurements were carried out under the various assisted air pressures and the fixed fuel pressure. The air assist pintle type injector employed in this study is consisted of the air assist adaptor and an injector housing using the gasoline fuel and air as the working fluids. As results, increasing pressure of assisted air, the growth of spray tip penetration is gradually reduced at the end of spray and spray angle is steadily increased at the main spray region except from the early spray. For the air assist pressure of 25㎪ in a spray downstream, it is doncluded that droplet size distribution shows the peak of 10${\mu}{\textrm}{m}$ and most of the droplet sizes are less than 50${\mu}{\textrm}{m}$. Also, the air-assist injector extremely improves fuel atomization in order to produce much finer droplets, it shows that approximately, in this case, 50% decreade of SMD than without air assit.

• Journal of the Korean Society for Precision Engineering
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• v.32 no.4
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• pp.369-375
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• 2015

This paper presents ejection of high viscosity fluids with magnetostrictive inkjet printhead(Magjet), which is not common with any other printhead. The MagJet uses a magnetostrictive material, Terfenol-D rod with 10-mm in diameter and 50-mm in length, as an actuation mechanism. It has been known that high viscosity is often an obstacle in ejecting small and mono-disperse droplets. We calculated required pressure with fluidic inertia (Bernoulli equation) and viscous loss (Hagen Poiseuille equation). The required pressure for ejecting a droplet is 1300kPa. The generated force and displacement with Terfenol-D rod are estimated to be 480N (2600kPa) and $28{\mu}m$, respectively. It was enough that Magjet eject high viscosity fluid (Max 1000cP). The experiments are performed to eject the high viscosity fluid with Magjet. The ejection of high viscosity fluids is successful with the aid of Terfenol-D's high performance.

• International Journal of Automotive Technology
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• v.1 no.2
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• pp.95-100
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• 2000

The droplet and the turbulent characteristics of a counterflowing internal mixing pneumatic nozzle mainly focused. The measurements were made using a Phase Doppler Particle Analyzer under the different air pressures. The nozzle with tangential-drilled holes at an angle of 30 to the central axis has been designed. The spatial distributions of velocities, fluctuating velocities, droplet diameters and SMD were quantitatively and qualitatively fluctuating velocities were substantially higher than the radial and the tangential ones. This implies that the disintegration process is enhanced with the higher air pressure. The larger droplets were detected near the spray centerline at the upstream while the smaller ones were generated at the downstream. This was attributed to the lower rates of spherical particles which were not subject to instantaneous breakup. However, substantial increases in SMD from the central part tower spray periphery were predictable in downstream regions.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.8
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• pp.69-76
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• 2003

For stable combustion and safety of a structure of the propulsion system, a cooling system to the liquid rocket engine should be incorporated. In this study, Eulerian-Lagrangian scheme for two phase combustion, nongray radiation and soot formation effect, and film-wall interaction have been introduced to study the effect of film cooling. After briefly introducing the governing equation, combustion characteristics with change of wall temperature has been investigated by varying such parameters as fuel mass fraction for film cooling, diameter of the fuel droplet, overall mixture fraction of oxygen to fuel. Also, radiative heat flux is compared with the conductive one at the combustor wall.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.2
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• pp.87-92
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• 2008

The breakup processes and spray plume characteristics of liquid jets injected in subsonic air cross-flows were experimentally studied. The behaviors of column, penetration, breakup of plain liquid jet and droplet sizes, velocities have been studied in non-swirling cross-flow of air. Nozzle has a 1.0 mm diameter and Lid ratio=5. Experimental results indicate that the breakup point is delayed by increasing air momentum, the penetration decreases by increasing Weber number and the split angle is increased by increasing air velocity or decreasing injection velocity. SMD increases according as increasing height or decreases in accordance with increasing air velocity. This phenomenon is related to the momentum exchange between column waves and cross-flow stream. Droplet vector velocities were varied from 11.5 to 33 m/s. A higher-velocity region can be identified in down edge region at Z/d=40, 70 and 100. Lower-velocity region were observed on bottom position of the spray plume.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.4
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• pp.484-495
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• 2003

This study investigates the flow characteristics of fuel droplets between twin spray for the 4-hole injector used a 4-valve gasoline engine. The injectors for this study were the three types of 4-hole gasoline injector in which orifice diameter was 0.24mm. The spray behavior of twin spray was investigated by means of visualization employed stroboscope. A PDPA system was employed to simultaneously measure the size and velocity of fuel droplets. The 3 dimensional mean velocities. droplet size distributions, SMD and joint probability density function of velocity and droplet size are analyzed at the center of the spray and the center region of twin spray. As a result, the configurations of injector exit such as orifice interval and length of outlet, are very important factors that affect the flow characteristics of fuel droplets at the center region of twin spray.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.12
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• pp.1635-1646
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• 1997

The nozzle length to diameter ratio of real diesel nozzles is about 2-8 which is not long enough for a fully developed and stabilized flow. The characteristics of the flow such as turbulence at the nozzle exit which affect the development of the spray can be enhanced by impinging the flow inside nozzle. The flow details inside the impinging nozzles have been investigated both experimentally and numerically. The mean velocities, the fluctuating velocities, and discharge coefficients in the impinging inlet nozzles, round inlet nozzle, and sharp inlet nozzle were obtained at various Reynolds number. The developing feature of the external spray were photographed by still camera and the droplet sizes and velocities were also measured by laser Doppler technique. The spray angle was greater and the droplet sizes near the spray axis were smaller with the impinging flow inside nozzle.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.12
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• pp.1591-1599
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• 2004

A series of experiments were conducted to study the effectiveness of the extinction of a liquid pool fire with two different water atomizing nozzles. Fire source is a small-scale circular stainless steel pan of 120mm in diameter with the fuels of hexane and ethanol. K-type thermocouples were used to measure the flame and fuel temperature along the pool centerline and under fuel surface. A digital camera was used to visualize the process of the fire suppression. The experimental results show that water mist droplet size is l15∼180${\mu}{\textrm}{m}$ with nozzle A and 130∼190${\mu}{\textrm}{m}$ with nozzle B. The extinguishing time of pool fire was reduced with the increase of pressure. When water droplets are small, they do not reach the flame base since they may be deflected or evaporated by the fire plume. However, influence of flow rate is more important than droplet size on fire extinction. Among the fire extinction mechanisms, drop of flame temperature is superior to suffocation of $O_2$ concentration.