• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.385-388
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• 2002

The researches of a two-phase atomizers have been carried out in the field of automotive and aerospace industries in order to improve the atomization performance of the liquid droplets ejecting from these nozzles. The smaller droplets have the advantages of the reduction of environmental pollution matter and effective use of energy through the improvement of heat and mass transfer efficiency. Thus, to propose the basic information of two-phase flow, an internal mixing atomizer was designed, its shape factor was 0.6 and the liquid feeding hole was positioned at the center of the mixing tube which was used to mix the air and liquid. The experimental work was performed in the field after the nozzle exit orifice. The measurement of the liquid droplets was made by PDPA system. This system can measure the velocity and size of the droplets simultaneously. The number of the droplets used in this calculation was set to 10,000. The flow patterns were regulated by ALR (Air to Liquid mass Ratio). ALR was varied from 0.1024 to 0.3238 depending on the mass flow rate of the air. The analysis of sampling data was mainly focused on the spray characteristics such as flow characteristics distributions, half-width of spray, RMS, and turbulent kinetic energy with ALR.

• 상하수도학회지
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• 제27권2호
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• pp.261-272
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• 2013

Algae boom (Red tide) in south coastal area of Korea has been appeared several times during a decade. If algae boom appears in the desalination plant, media filter and UF filter are clogged quickly, and the plant should be shutdown. In general, Algae can be removed from water by flotation better than by sedimentation, because of the low density of algal cell. The purpose of this study conducts the CFD simulation of DAF flotation basin to apply the design of the dissolved air flotation with ball filter in the Test Bed for SWRO desalination plant. In this study, Eulerian-Eulerian multiphase model was applied to simulate the behavior of air bubbles and seawater. Density difference model and gravity were used. But de-sludge process and mass transfer between air bubbles and seawater were ignored. Main parameter is hydraulic loading rate which is varied from 20 m/hr to 27.5 m/hr. Geometry of flotation basin were changed to improve the DAF performance. According to the result of this study, the increase of hydraulic loading rate causes that the flow in the separation basin is widely affected and the concentration of air is increased. The flow pattern in the contact zone of flotation basin is greatly affected by the location of nozzle header. When the nozzle header was installed not the bottom of the contact zone but the above, the opportunity of contact between influent and recycle flow was increased.

• 대한기계학회논문집A
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• 제21권6호
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• pp.961-970
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• 1997

A numerical method is presented to predict and analyze the shape of a growing billet produced from the "spray forming process" which is a fairly new near-net shape manufacturing process. It is important to understand the mechanism of billet growing because one can obtain a billet with the desired final shape without secondary operations by accurate control of the billet shape, and it can also serve as a base for heat transfer and deformation analysis. The shape of a growing billet is determined by the flow rate of the alloy melt, the mode of nozzle scanning which is due to cam profile, the initial positio of the spray nozzle, scanning angle, and the withdrawal speed of the substrate. In the present study, a theoretical model is first established to predict the shape of the billet and next the effects of the most dominent processing conditions, such as withdrawal speed of the substrate and the cam profile, on the shape of the growing billet are studied. Process conditions are obtained to produce a billet with uniform diameter and flat top surface, and an ASP30 high speed steel billet is manufactured using the same process conditions established from the simulation.imulation.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2023년도 봄 학술논문 발표대회
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• pp.91-92
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• 2023

With the development of technology, interest in the implementation of free-form buildings is increasing, and research on producing free-form panels is being conducted accordingly. Since free-form buildings are curved and consist of geometric shapes, there are many problems with the production technology of free-form panels that implement them. Due to the inability to reuse molds, the cost of disposal of construction waste and waste of manpower for assembly increase the construction period and construction cost. To improve these limitations, a 3D printed concrete nozzle for FCP production was developed. However, this technology is not quantitatively extruded according to the shape of the panel, and there is a problem that residues are generated. Therefore, an free-form panel extrusion experiment was conducted to analyze the limitations of existing nozzles and to analyze the requirements for the development of new concrete extrusion nozzles. Existing nozzles were unable to be quantitatively extruded, resulting in errors. Due to the weak pressure of the screw and the inability to adjust the internal pressure, detailed extrusion speed control was impossible, and residue generation in the opening and closing device seemed to be the cause. Therefore, a pump capable of quantitative concrete pressure transfer and a pressure control device for easy extrusion of concrete are required. In addition, it is judged that it is necessary to develop an opening and closing device and an extrusion device that do not generate residues. The results of this study are expected to provide information for FCP production and production and to be a basic study of technologies necessary for the production of free-form building panels.

• 태양에너지
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• 제13권1호
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• pp.22-30
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• 1993

본 연구(硏究)는 축대칭공기분류계(軸對稱空氣噴流界)에서 흐름방향(方向)에 수직(垂直)이 되도록 설치(設置)한 평판전열면상(平板傳熱面上)에서의 열전달(熱傳達)을 증진(增進)시키기 위해 공기분류(空氣噴流)에 선회(旋回)를 주었을때, 유동(流動)의 특성(特性) 및 전열면(傳熱面)에서의 전열증진효과(傳熱增進效果)와 이에 따른 난류강도(亂流强度)와 관계(關係), 그리고 선회(旋回)를 주었을때와 주지 않았을때와의 열전달율(熱傳達率)의 비교(比較)와 최적선회조건(最適旋回條件) 및 이에 대한 전열특성(傳熱特性)을 구명(究明)하기 위한 실험적(實驗的) 연구(硏究)이다. 본 실험(實驗)에서는 부가적(附加的)인 동력(動力)을 사용(使用)하지 않고 간편(簡便)하게 열전달(熱傳達)을 증진(增進)시키기 위한 방편(方便)의 하나로, 노즐출구(出口)에 Twisted Tape이 설치(設置)된 Pipe를 부착(附着)하여 공기분류(空氣噴流)에 선회(旋回)를 주었으며, Twisted Tape의 비틀림 각도(角度)에 따른 선회도(旋回逃)를 S=0., 0.056, 0.111, 0.167, 0.222로 하였다. 유속(流速)은 14, 20, 26, 32, 38, 44m/s의 조건(條件)으로, 전열면간거리(傳熱面間距離)(H/D)는 1에서 14까지 하였고, 열전달증진(熱傳達增進)을 일으키는 유동구조(流動構造)를 해석(解析)하기 위해 열선유속계(熱線流速計)를 사용(使用)하여 선회도(旋回度)에 따라 각점(各點)에서의 유속(流速) 및 난류강도(亂流强度)를 측정(測定)하였으며, 전열면(傳熱面)의 온도(溫度)를 측정(測定)하여 Nu를 구(求)하고 선회(旋回)를 주었을때와 주지 않았을때의 열전달증진효과(熱傳達增進效果)를 비교(比較)하였다. 또한 선회도(旋回度)에 따른 열전달(熱傳達)이 최대(最大)가 되는 최적거리(最適距離)를 제시(提示)하였으며 난류강도(亂流强度)와 열전달(熱傳達)과의 관계(關係)를 구명(究明)하였다.

• 한국전산구조공학회논문집
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• 제24권6호
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• pp.699-705
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• 2011

고기동 유도탄은 짧은 시간에 큰 추력을 필요로 하는 발사체이다. 유도탄의 비행에 필요한 추력을 얻기 위하여 고체 연료를 폭발적으로 연소시키면 고온, 고압의 연소 가스가 발생되고, 이 연소 가스를 초음속 노즐을 통하여 팽창시킴으로서 큰 추력을 얻게 된다. 로켓 모터의 작동 시간은 수초 미만에 지나지 않으나 큰 추력을 내기 위해 고온 고압의 연소 가스가 이용됨으로 평창 과정 중 시스템 부품의 파손 혹은 노즐목 부근에서 삭마현상이 발생되기도 한다. 즉, 탄의 정확한 제어를 위해서는 연소 가스와 벽면과의 열전달에 따른 열응력과 유동장 내의 압력의 변화에 따른 구조체 응력이 동시에 고려된 정확한 응력해석이 선행되어야만 한다. 본 논문에서는 예비 설계된 추력 발생장치에 고온 고압의 연소 가스가 유동할 때 모터의 작동시간에 따른 구조체의 안전성을 응력과 재료의 용융온도의 측면으로부터 구명하였다.

• 대한기계학회논문집B
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• 제23권6호
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• pp.734-743
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• 1999

The local Nusselt numbers have been measured for a round turbulent jet impinging on the concave surface with and without rib. Liquid crystal/transient method was used to determine the Nusselt number distributions along the surface. The temperature on the surface was measured using liquid crystal and a digital color image processing system. The experiments were made for the jet Reynolds number (Re) 23,000, the dimensionless nozzle-to-surface distance (L/d) from 4 to 10, the dimensionless surface curvature (d/D) 0.056, and the rib type (height ($d_1$) 0.2 cm, pitch (p) from 1.2 to 3.2 cm). It was founded that only when $L/d{\geq}6$, the average Nusselt numbers on the concave surface with rib are higher than those without rib, mainly due to an increase in the turbulent intensity caused by the effect of rib attached to the wall surface. It was realized that the rib attached to the concave surface may no longer enhance the heat transfer rate or even lowers it depending on the rib type and flow conditions. In addition, the results by the steady-state method using the gold-film Intrex were in good agreement with those by the transient shroud method.

• 한국항공우주학회지
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• 제35권11호
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• pp.1013-1021
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• 2007

스마트무인기 연료공급시스템에 사용되는 연료이송 제트펌프의 1차원 유동해석을 통한 설계가 이루어졌으며 성능 검증 및 설계 개선점을 찾고자 상용코드를 이용하여 전산해석이 수행되었다. 해석적 연구 결과로부터 제트펌프는 스마트무인기 연료공급시스템에서 요구하는 유량비 2.23을 만족하는 설계가 이루어졌음이 확인되었다. 구동노즐에 작용하는 압력은 낮게 예측된 손실계수로 인하여 전산해석의 경우가 1차원 유동해석을 통한 설계값보다 더 높은 값을 나타냈다. 결과적으로 제트펌프 구성 요소의 정확한 크기 결정을 위해서는 각 주요부에서의 손실계수에 대한 정확한 데이터가 필요하며, 데이터는 측정위치 및 측정대상의 기하학적 형상 정보와 함께 제공되어져야 한다.

• Advances in aircraft and spacecraft science
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• 제7권6호
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• pp.537-551
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• 2020

Investigation of leading edge impingement cooling for first stage rotor blades in an aero-engine turbine, its effect on rotor temperature and trailing edge wake loss have been undertaken in this study. The rotor is modeled with the nozzle for attaining a more accurate simulation. The rotor blade is hollowed in order for the coolant to move inside. Also, plenum with the 15 jet nozzles are placed in it. The plenum is fed by compressed fresh air at the rotor hub. Engine operational and real condition is exerted as boundary condition. Rotor is inspected in two states: in existence of cooling technique and non-cooling state. Three-dimensional compressible and steady solutions of RANS equations with SST K-ω turbulent model has been performed for this numerical simulation. The results show that leading edge is one of the most critical regions because of stagnation formation in those areas. Another high temperature region is rotor blade tip for existence of tip leakage in this area and jet impingement cooling can effectively cover these regions. The rotation impact of the jet velocity from hub to tip caused a tendency in coolant streamlines to move toward the rotor blade tip. In addition, by discharging used coolant air from the trailing edge and ejecting it to the turbines main flow by means of the slot in trailing edge, which could reduce the trailing edge wake loss and a total decrease in the blade cooling loss penalty.

• 한국수정란이식학회지
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• 제27권1호
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• pp.37-43
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• 2012

This study evaluated a method of sorting X and Y chromosomes based on size using the forward angle light scatter related refractive index (FSC) of a flow cytometer. Hanwoo bulls sperm were separated to X and Y chromosomes by the parameters of FSC or Hoechst 33342 intensity. As a result, using monitor program linked flow cytometry during sorting processing, the purities were $97{\pm}0.57$ or $96{\pm}0.67%$ for the X-fraction and $96{\pm}0.33$ or $97{\pm}1.33%$ for the Y-fraction in the two sperm sorting methods. There were no differences in the X and Y ratios (X and Y %) between the sperm sorting methods based on FSC or DNA content. The proportions of female and male embryos used for in vitro fertilization and development were $66.03{\pm}3.31$ or $69.37{\pm}1.41%$, and $70.56{\pm}2.42$ or $56.11{\pm}3.09%$ when sperm were processed using the sex sorting method by FSC or Hoechst 33342. In conclusion, further study is needed to determine the optimum procedure and improve the nozzle to enhancing sorting accuracy or efficiency. Also, the findings of this study do not negate the possibility that the difference method of sperm sorting cannot use a UV laser beam.