• 한국연소학회:학술대회논문집
• /
• 2000.12a
• /
• pp.202-211
• /
• 2000

Characteristics of the fuel injection and entrainment of the primary air of gas burner have been investigated. Primary air flow rates that entrained by gas streams play major role to control the performance of the partially premixed combustion. Pressure distributions of mixing tube assembly are studied as major parameter for increasing the primary air flow rates. Buoyancy-effect burner is proposed as one alternative to improve the pressure distribution. Buoyancy effect caused by metal ring placed around the flame holes reduces pressure of the entrance of the mixing tube and that, entrained air flow rates are increased.

• 한국전산유체공학회:학술대회논문집
• /
• 2008.03b
• /
• pp.369-372
• /
• 2008

An experimental study is carried out to study two-phase vertically upward hydraulic transport of solid particles by water in a vertical and inclined (0${\sim}$60 degree) concentric annulus with rotation of the inner cylinder. Rheology of particulate suspensions in shear-thinning fluids is of importance in many applications such as particle removal from surfaces, transport of proppants in fractured reservoir and cleaning of drilling holes, and so on. Annular fluid velocities varied from 0.2 m/s to 1.5 m/s for the actual drilling operational condition. Macroscopic behavior of solid particles, averaged flow rate, and particle rising velocity are observed. Main parameters considered in this study were radius ratio, inner-pipe rotary speed, fluid flow regime, and particle injection rate. For both water and CMC solutions, the higher the concentration of the solid particles is, the larger the pressure gradients become

• Journal of the Korean Geosynthetics Society
• /
• v.15 no.3
• /
• pp.57-66
• /
• 2016

In this study, to prevent possible collapse caused by hydraulic or mechanical instability, liquid nitrogen injection method is developed and implemented at the tip of drilling auger of steel pipe propulsion tunneling. In this study, 1/5-scale model auger and sand chamber were manufactured. The prototype diameter of steel pile (or casing) is assumed about 1,000 mm. For the frictional sandy soils and plastic weathered soils, liquid nitrogen injection methods were tested varying water contents of the soils. For the induced hydraulic instability, the ground near the drilling auger was frozen within approximately 5 minutes preventing mechanical collapse and water infiltration. Securing stability of steel pile propulsion tunneling using liquid nitrogen was much more effective for which the water content of the soil somewhat exceeds the optimum water content.

• Journal of Korean Society of Water and Wastewater
• /
• v.33 no.5
• /
• pp.353-366
• /
• 2019

This research proposes an optimal flushing operation technique in an effort to prevent secondary water pollutions and accidents in aged pipes, and to improve the cleaning effect of unidirectional flushing. Water flow directions were analyzed using EPANET 2.0, while flushing and air scouring experiments in forward and reverse directions were performed in the field. In 42 experiments, average residual chlorine concentration and turbidity were improved after cleaning compared to before cleaning. It was found that even when the same cleaning method was used, further improvement of cleaning effect was possible by applying air injection and reverse direction cleaning techniques. By means of one-way ANOVA(Analysis of variance), it was also possible to statistically verify the need of actively utilizing air injection and reverse direction cleaning. Based on correlation between turbidity and TSS, the total amount of suspended solids removal was estimated for 874 flushing operations and 194 air scouring operations. The result showed that air scouring used more discharge water than flushing by an average of $4.9m^3$ yet with larger amounts of suspended solids removal by an average of 145.9 g. The result of analysis on turbidity values from 887 flushing operations showed low cleaning effect of unidirectional flushing for the pipes with diameters over 300 mm. In addition, the turbidity values measured during cleaning showed an increasing tendency as pipe age increased. The methodology and results of this research are expected to contribute to the efficient maintenance and improvement of water quality in water distribution networks. Follow-up research involving the measurement of water quality at regular time intervals during cleaning would allow a more accurate comparison of discharge water quality characteristics and cleaning effects between different cleaning methods. To this end, it is considered necessary to develop a standardized manual that can be used in the field and to provide relevant trainings.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.34 no.11
• /
• pp.999-1004
• /
• 2010

Recently, many technologies have been developed in order to satisfy stringent emission regulations. However, in the case of diesel engines, the stringent emission regulations with respect to NOx and PM have not yet been satisfied. A dramatic reduction in the NOx and PM emissions could be achieved by using after-treatment systems such as lean NOx trap (LNT) and urea-SCR systems. However, the high temperature in the exhaust pipe affects the spray behavior of the secondary injector, which is used for supplying the Urea-SCR. Because of this high temperature, it is difficult to achieve uniform distribution of the reducing agent in the manifold. In this paper, the characteristics of a urea-SCR injector used for injecting in the exhaust pipe are presented. The purpose of this study was to investigate the spray characteristics of the injector, such as the spray angle, injection quantity, and SMD. In addition, laser diagnostics and high-speed-camera images were used to analyze the injector spray characteristics and to present a distribution of reduction in the transparent manifold.

• Journal of Energy Engineering
• /
• v.18 no.2
• /
• pp.87-92
• /
• 2009

An experimental investigation is conducted to study a 2-phase vertically upward hydraulic transport of solid particles by water and non-Newtonian fluids in a slim hole concentric annulus with rotation of the inner cylinder. Rheology of particulate suspensions in viscoelastic fluids is of importance in many applications such as particle removal from surfaces, transport of proppants in fractured reservoir and cleaning of drilling holes, etc. In this study, a clear acrylic pipe was used in order to observe the movement of solid particles. Annular velocities varied from 0.3 m/s to 2.0 m/s. The mud systems included fresh water and CMC solutions. Main parameters considered in the study were inner-pipe rotation speed, fluid flow regime and particle injection rate. A particle rising velocity and pressure drop in annulus have been measured for fully developed flows of water and of aqueous solutions. For both water and 0.2% CMC solutions, the higher the concentration of the solid particles is, the larger the pressure gradients become.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.16 no.4
• /
• pp.417-430
• /
• 2014

A new rock excavation method using an abrasive waterjet system is under development for efficiently creating tunnels and underground spaces in urban areas. In addition, an appropriate abrasive flow rate and abrasive flow quality are important for the new rock excavation (cutting) method using an abrasive waterjet system. This study evaluated the factors influencing the abrasive flow rate and abrasive flow quality, specifically the abrasive pipe height, length, tortuosity and inner diameter, through experimental tests. Based on the experimental test results, this study suggested optimal conditions for the abrasive flow rate and abrasive flow quality. The experimental results can be effectively utilized as baseline data for rock excavation methods using an abrasive waterjet system in various construction locations such as tunnels near urban surroundings, utility tunnels, and shafts.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.14 no.1
• /
• pp.63-68
• /
• 2013

The steam power plant is becoming more important to supply a stable power lately. Desuperheater of the steam power plant facility plays a role in maintaining the proper superheat to avoid damage turbine power due to the superheated steam produced in the boiler. In this study, when the steam flows $530^{\circ}C$, 36.7 kg/s, 1.36 MPa in the 460mm pipe, variable orifice nozzle developed in Korea was carried out the performance analysis in coolant injection conditions of $150^{\circ}C$, 4.28 MPa. Findings, steam pipe coolant temperature was maintained at $446^{\circ}C$ and sprayed droplet size was verified by $50{\mu}m$ or less.

• Journal of the Korean Institute of Gas
• /
• v.26 no.5
• /
• pp.35-40
• /
• 2022

PCVD (Plasma Chemical Vapor Deposition), a solar cell manufacturing facility, is a facility that deposits plasma generated in a chamber (NH₃, SIH₄, O₂ on a wafer. In the PCVD facility, gas movement and injection is performed in the gas cabinet, and there are many leak points inside because MFC, regulator, valve, pipe, etc. are intricately connected. In order to prevent explosion in case of leakage of NH₃ with an upper explosive limit (UEL) of 33.6% and a lower explosive limit (LEL) of 15%, the dilution capacity must be capable of allowing the concentration of NH₃ to be out of the explosive range. This study was analyzed using the CFD analysis technique, which can confirm the dilution ability in 3D and numerical values when NH₃ gas leaks from the existing PCVD gas cabinet. As a result, it was concluded that it corresponds to medium dilution and that testicular ventilation is possible through facility improvement.

• 제어로봇시스템학회:학술대회논문집
• /
• 2004.08a
• /
• pp.1516-1519
• /
• 2004

A tele-operated robot should be used to maintain and inspect nuclear power plants to reduce the radiation exposure to the human operators. During an overhaul of the nuclear power plants in Korea, a ROV(Remotely Operated Vehicle) may enter a cold-leg connected to the reactor to examine the state of the thermal sleeve and it's position in the safety injection nozzle. To measure the positions of the thermal sleeve or scratches from the video images captured during the examination, the camera parameters should be identified. However, the focal length of the CCD camera could be increased to a close up of the target and the aspect ratio and the center of the image could also be varied with capturing devices. So, it is desired to self-calibrated the intrinsic parameters of the camera and capturing device with the video images captured during the examination. In the video image of the safety injection nozzle, two or more circular grooves around the nozzle are shown as ellipse contours. In this paper, we propose a camera self-calibration method using a single image containing two circular grooves which are the greatest circles of the cylindrical nozzle whose radius and distance are known.