• Journal of Drive and Control
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• v.16 no.1
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• pp.1-6
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• 2019

The use of micro bubbles in industrial fields has been increasing in the recent years., particularly micro-bubble sterilization and water purification effects. Various methods have been developed for the generation of micro-bubbles. Depending on the method of generating bubbles, the micro-bubbles can be roughly classified into saturation molding, cavitation and rotation flow types. The objective of this study was to use ventilated tube type as a method of generating micro-bubbles in order to purify large amount of water quality such as lakes and reservoirs. This method shows a difference in efficiency in which micro-bubbles are generated depending on the contact ratio of gas to liquid. The study also investigated the optimal gas liquid contact ratio by applying various orifice methods and investigated the optimum condition of micro-bubble generation by gas Based on this, a technology to develop a micro-bubble generator with a venturi type nozzle shape that has a high water purification effect was developed.

• Journal of Hydrogen and New Energy
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• v.34 no.1
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• pp.77-82
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• 2023

The fuel cell in fuel cell electric vehicle utilizes oxygen in the atmosphere, which requires the use of an air cleaner system to minimize the intake of harmful pollutants. To estimate the performance of the air cleaner system, the pressure drop between the filter inlet and outlet is used under the rated air flow condition. In this study, the effect of sensor error in this air cleaner testing is experimentally carried out. It is found that the errors of the temperature sensor does not significantly affect the estimation of pressure drop. However, in the case of the pressure sensor, 5% sensor error results in the error of pressure drop estimation by 3%. Therefore, it is recommended that the measurement accuracy of the pressure sensor mounted in test system should be maintained at less than 5%.

• Journal of ILASS-Korea
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• v.29 no.3
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• pp.140-146
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• 2024

This study investigates the application of effervescent nozzles to liquid rockets using a laboratory-scale twin fluids spray test system. Typically, rocket engines using a single liquid propellant control thrust by adjusting the mass flow rate, which is influenced by the spray differential pressure between the fluid pressure at the injector front and atmospheric pressure. As the differential pressure decreases, uneven atomization and combustion instability can occur. To address this issue, this research explores an effervescent nozzle that mixes gaseous and liquid propellants to maintain injection pressure. Experiments were conducted on eight different nozzle types with varying orifice and aerator sizes. The experimental results demonstrated internal pressure variations and differences in spray characteristics based on nozzle design, which were analyzed and discussed. if these injection characteristics are applied in the future, it is expected that they could also be utilized in eco-friendly alternative fuels such as Sustainable Aviation Fuel (SAF).

• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.2
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• pp.269-278
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• 2004

In this study, hydraulic and hydrologic safety of an existing dam with morning glory spillway was evaluated and the problems were derived in order to control extreme floods efficiently. For design flood(520cms and EL. 170.3m), the spillway was turned out to have no problem for discharge and negative pressure in vertical transition. However, the critical point for discharge starts with EL. 170.7m which transits weir flow condition to orifice flow condition and there may be negative pressure in weir crest. While maximum water level can not be greater than EL. 170.5m including freeboard according to the dam design criteria, the maximum water level based on reservoir routing was turned out to be EL. 172.46m, and fundamental measures should be requested and planned.

• Journal of Korean Neurosurgical Society
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• v.29 no.8
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• pp.1019-1023
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• 2000

Objective : Endoscopic third ventriculostomy is gaining popularity as a minimally invasive surgical option for certain types of hydrocephalus as an alternative to shunting. The authors have tried to fenestrate down to the subdural space passing through the prepontine cistern to lessen or avoid the chance of redoing due to healing. Materials and Method : A 48-year-old male patient with several years of intractable headache was presented. Magnetic Resonance Image(MRI) of the brain revealed marked ventricular dilatation with stenotic cerebral aqueduct. A 2.3mm flexible steerable endoscope($Neuroview^{(R)}$) was introduced via precoronal route and accessed to the third ventricular floor. Using 3-French Fogarty balloon catheter, thin third ventricular floor and the arachnoid membrane of the prepontine cistern were fenestrated, so called "double fenestration". To confirm the fenestration, subdural compa-rtment of the left abducens nerve was identified during the procedure. Forceful pulsating flow through the orifice convinced the patency of the opening. Results : The patient was discharged on the third postoperative day without any postoperative complications. The postoperative follow-up MRI of the brain, at second and sixth months, clearly demonstrated the flow void through the third ventricular floor. Conclusions : Endoscopic third ventriculostomy was successfully performed on an adult hydrocephalus patient with aqueduct stenosis. The third ventricular floor and arachnoid membrane of the prepontine cistern were fenestrated to achieve double fenestration to minimize the chance for failure. The details of this procedure and results are described.

• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.4
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• pp.8-14
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• 2015

This study has been done as a preliminary work in the process of confirming the modeling and calculation results on the dynamic characteristics of closed-type swirl injector which were performed by Ismailov et al. in Purdue university. Closed-type swirl injectors with replaceable swirl chamber parts were designed and manufactured. The steady state spray characteristics of closed-type swirl injector with varying swirl chamber length and diameter were verified. Mass flow rate was measured with a mass flow meter installed in front of the injector, and liquid film thickness was measured by Lefebvre's method with electrodes installed at the orifice of the injector. Variation of spray cone angle and break-up length were investigated from the spray images captured under different manifold pressure conditions.

• Journal of computational fluids engineering
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• v.21 no.1
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• pp.50-57
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• 2016

In various industries related with construction and military machinery, a large amount of power is normally required because such machinery operations, such as digging or breaking, take place under difficult working conditions in a rough environment. Thus, a hydraulic system needs to be applied as the major power transfer system. To produce and supply hydraulic power depending on the various load conditions, a hydraulic piston pump is utilized as a typical power source for a hydraulic system. In the present study, numerical simulations were conducted using the commercial program, Ansys CFX 14.5. To lubricate the moving parts as the pump starts to operate, a small amount of oil leaks out through the clearance between the orifice in the piston-shoe and the recess at the swash-plate. Taking this into consideration, a cylindrically shaped computational domain was modeled to maintain the same equivalent leakage area. To validate the numerical method applied herein, the numerical results of the flow rate at the discharge port were compared with the experimental data, and a good agreement between them was shown. Using the verified method, the effects of the discharge pressure and the angle of the swash-plate were also evaluated under several load conditions. The results of the present study can be useful information for a hydraulic piston pump used in many different manufacturing industries.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.6 s.261
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• pp.547-557
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• 2007

This study was conducted to investigate the flow and combustion characteristic of the experimental burner which was manufactured for the reflection of the oven and broil burner features. As slot shape, spacing between slots, and slot arrangement of the exit area which emits the mixing gas are different in case of oven burners and broil turners, the purpose of this study is to know the affection of the flame interaction and combustion characteristic according to the change of shape factors such as slot shape, slot arrangement, and slot-to-slot spacing. With no relation of the slot shape, as the spacing between slots became narrow, the occurrence of a lift-flame was delayed. So the combustion was possible in the leaner region, but the appearance of yellow-tip became a little fast. Slit slot port had the broadest operating range among the other slot shapes. Specially, from the side of lift-flame, as the jet that spreads downstream in the longitudinal slot was nearly circular just a few slot lengths away from the orifice, slot-to-slot spacing of the Slit port was closer than the other ports. These results could be expected through the computer numerical method and had a good agreement. As the spacing between slots increased, in case of Slit and Mix port, NOx emission rate was constant or decreased, but the NOx emission of Hole port was increased. CO emission rate of Slit and Hole port was increased as the slot-to-slot spacing was broadened.

• Journal of Veterinary Clinics
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• v.32 no.1
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• pp.101-104
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• 2015

A 4-years-old, intact male Golden retriever dog was presented with abdominal distension and dyspnea. Physical examination revealed arrhythmia and cardiac murmur. Generalized cardiomegaly, pleural effusion and ascites were shown on thoracic and abdominal radiographs. Two-dimensional echocardiography revealed abnormal mitral and tricuspid valve motion, mitral and tricuspid regurgitation, left ventricular eccentric hypertrophy and left atrial dilation. Color-flow Doppler imaging revealed turbulent flow extending into the left ventricle during diastole from the mitral valve orifice, and into the left atrium during systole. Spectral Doppler recordings revealed highly increased early diastolic mitral valve inflow and prolonged pressure half-time of mitral inflow. Based on the echocardiographic examination, the diagnosis was made as the mitral valve dysplasia concurrent with mitral valve stenosis and tricuspid valve dysplasia.

• Journal of Mechanical Science and Technology
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• v.17 no.5
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• pp.766-775
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• 2003

The intermittent spray characteristics of a multi-hole diesel nozzle with a 2-spring nozzle holder were investigated experimentally. Without changing the total orifice exit area, the hole number of the multi-hole nozzle varied from 3 (d$\_$n/=0.42 mm) to 5 (d$\_$n/=0.32 mm). The time-resolved droplet diameters of the spray including the SMD (Saute. mean diameter) and the AMD (arithmetic mean diameter), injected intormittently from the multi-hole nozzles into still ambient ai., were measured by using a 2-D PDPA (phase Doppler particle analyze.). The 5-hole nozzle spray shows the smaller spray cone angle, the decreased SMD distributions and the small difference between the SMD and the AMD, compared with that of the 3-hole nozzle spray. From the SMD distributions with the radial distance, the spray structure can be classified into the three regions : (a) the inner region showing the high SMD distribution , (b) the mixing flow region where the shea. flow structure would be constructed : and (c) the outer region formed through the disintegration processes of the spray inner region and composed of fine droplets. Through the SMD distributions along the spray centerline, it reveals that the SMD decreases rapidly after showing the maximum value in the vicinity of the nozzle tip. The SMD remains the constant value near the Z/d$\_$n/=166 and 156.3 for the 3-hole and 5-hole nozzles, which illustrate that the disintegration processes of the 5-hole nozzle spray proceed more rapidly than that of the 3-hole nozzle spray.