• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2002년도 춘계공동학술발표회요약집
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• pp.129-129
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• 2002

• 대한기계학회논문집B
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• 제26권6호
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• pp.788-794
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• 2002

In liquid rocket engine, propellant feed rate is proportional to approximately square root of the pressure difference between injector head and combustion chamber. This ΔP depends on the engine design, but in general on the order of 50psi. However, during ignition period, especially for the pressurized feed system, combustion chamber pressure is almost atmospheric and large ΔP causes over flow of propellants which may lead to catastrophic accident due to hard start. Hard start may be prevented by applying cavitating venturi or/and two step ignition. In cavitating venturi, evaporated propellants near the venturi throat become chocked and flow rate depends on only upstream condition. In two step ignition propellants are supplied to the liquid engine in two different flow rate. First step, to avoid hard start, small amount of propellants are supplied to build up chamber pressure in safe zone, then full propellants to ensure design pressure. In this study, both cavitating venturi and two step ignition method were used for the hot test and hard start problem was completely solved.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제35회 추계학술대회논문집
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• pp.300-303
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• 2010

다양한 형상의 인젝터 내부 젤 추진제 유동을 수치적으로 연구하였다. 모사 젤 추진제의 유변학적물성치를 측정하고 plain-orifice, chamfered-orifice 및 venturi 형상 인젝터의 유동 특성을 분석하였다. Plain-orifice 및 chamfered-orifice 인젝터의 경우 하류방향으로 유동이 진행할수록 점도가 높아지는 특성이 나타났으며 Venturi 형상의 경우 인젝터 내부 유동에서 낮은 점도가 지속적으로 유지됨을 알 수 있었다. Reynolds 수가 증가할수록 이러한 경향이 뚜렷하게 나타나는 것이 확인되었다.

• Nuclear Engineering and Technology
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• 제53권6호
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• pp.1756-1768
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• 2021

The containment filtered venting system (CFVS) filters the atmosphere of the containment building and discharges a part of it to the outside environment to prevent containment overpressure during severe accidents. The Korean CFVS has a tank that filters fission products from the containment atmosphere by pool scrubbing, which is the primary decontamination process; however, prediction of its performance has been done based on researches conducted under mild conditions than those of severe accidents. Bubble behavior in a pool is a key parameter of pool scrubbing. Therefore, the bubble behavior in the pool was analyzed under various injection flow rates observed at the venturi nozzles used in the Korean CFVS using a wire-mesh sensor. Based on the experimental results, void fraction model was modified using the existing correlation, and a new bubble size prediction model was developed. The modified void fraction model agreed well with the obtained experimental data. However, the newly developed bubble size prediction model showed different results to those established in previous studies because the venturi nozzle diameter considered in this study was larger than those in previous studies. Therefore, this is the first model that reflects actual design of a venturi scrubbing nozzle.

• 한국가시화정보학회지
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• 제17권1호
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• pp.60-68
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• 2019

Flow visualizations have been carried out to analyze the characteristics of bubby flows exhausted from a venturi-type bubble generator with an air vent. For various design parameters and operating conditions of the bubble generator, the images of bubbly flows was recorded using a high-speed camera and a microscope. Then the amount and size distribution of bubble was evaluated by an image processing technique. The results show that for increasing the amount of bubble, it is more effective to reduce the venturi throat than to enlarge the air vent diameter. If the water flow rate increases, the bubble generation rate increases but reaches a status of saturation, whose condition depends on Reynolds number at a given air vent diameter. The bubble size increases as the diameter of venturi throat decreases and Reynolds number increases. However, the air vent diameter is not a significant factor on bubble size.

• 한국기계가공학회지
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• 제17권2호
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• pp.8-14
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• 2018

In the present work, a numerical study is carried out to observe the characteristics of the flow and particle behaviors in a supersonic double Venturi abrasive blasting nozzle. Schlieren flow visualization and Pitot pressure at the nozzle downstream are also carried out, and those measurement results are compared to the numerical ones for code validation. Open and closed secondary holes on the double Venturi nozzle surface are tested for various nozzle pressures, and the results are compared with the ones observed for other similar supersonic Laval nozzles.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1997년도 추계 학술대회논문집
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• pp.143-148
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• 1997

Differential pressure Venturi cone flowmeter is an advanced flowmeter which has many advantages such as wide range of measurement, high accuracy, excellent flow turndown ratio, low headless, and short installation pipe length requirement, etc. Like other differential pressure flowmeter, Venturi cone flowmeter uses the law of energy conservation, but its shape and position make it perform better than others. The cone acts as its own flow conditioner and mixer, fully conditioning and mixing the flow prior to measurement. For the analysis, we use Reynolds-averaged Navier-Stokes equations and $k-{\omega}$ turbulence model. The equations are fully trans-formed in the computational coordinates, the pressure-velocity coupling is made through SIMPLER algorithm, and the equations are discretized using analytic solutions of the linearized equations(Finite Analytic Method). At the end of the paper, using the result of analysis, We propose a new shape of cone with the hope of drag reduction and high performance.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2007년도 춘계 학술대회논문집
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• pp.130-133
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• 2007

A two-phase method in CFD has been developed and is applied to model the cavitation flow. The governing equation system is two-phase Navier-Stokes equation, comprised of the mixture mass, momentum and liquid-phase mass equation. It employs an implicite, dual time, preconditioned algorithm using finite difference scheme in curvilineal coordinates and Chien ${\kappa}-{\varepsilon}$ turbulence equation. The experimental cavitating flows around ogive-cylinder and venturi type objects are employed to test the solver. To prove the capabilities of the solver, several three-dimentional examples are presented.

• 터널과지하공간
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• 제24권6호
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• pp.464-472
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• 2014

환기제어 시설을 설치하지 않고 모든 공간을 개방한 형태의 대단면 주방식 채굴 작업장에 설치하는 국부선풍기의 운전에 따른 기류유동형태는 재순환을 포함하고 있어 복잡하고 정량화가 어렵고 환기효율 또한 매우 낮은 편이다. 본 논문에서는 국부선풍기의 운전에 따라 하류편의 기류 운동에너지 증가 및 정압강하 현상인 벤츄리(venturi) 효과로 인접갱도로부터 기류가 유입되어 기류 유동방향으로 환기량이 증가하는 현상을 선풍기 종류 및 설치방법 별로 CFD분석하였다. 분석대상 선풍기는 축류선풍기 1종류 및 프로펠러 선풍기 2종류이며 축류선풍기 중심점 설치 위치를 1.0, 1.5, 2.0m로 변경함에 따른 벤츄리 효과의 차이를 분석하였다. 연구결과는 공기질 개선을 통한 작업환경 관리를 위한 국부 환기의 경제성 및 효율성을 제고하는데 기여할 것으로 기대된다.

• 대한기계학회논문집B
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• 제24권2호
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• pp.270-279
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• 2000

Recently, according to increase in the requirement of electric power, a thermoelectric power plant equipped with pulverized coal combustion system is highly valued, because coal has abundant deposits and a low price compared with others. For efficient use of coal fuel, most of plant makers are studying to improve combustion performance and flame stability, and reduce pollutants emission. One of these studies is how to control the profile of particle injection and velocity dependant on coal nozzle configuration. Basically, nozzle which has mixed flow of gas and particle is required to have the balanced coal concentration at exit, but it is very difficult to obtain that by itself without help of other device. In this study, coal distribution and pressure drop in gas-solid flow are calculated by numerical method in nozzle with various shapes of venturi diffuser as a means to get even coal particle distribution. The tentative correlations of pressure drop and exit coal distribution are deduced as function of the height, length and reducing angle of venturi from the calculated results. When coal hurner nozzle is designed, these equations are very useful to optimize the shape of venturi which minimize uneven particle distribution and pressure drop within coal nozzle.