• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.532-537
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• 2003

Gas flow through orifice is encountered in many diverse fields of engineering applications. In order to investigate the critical gas flow through an orifice system, a computational analysis is performed using axisymmetric, compressible, Navier-Stokes equations which are numerically solved by a fully implicit finite volume method. In the present study, the discharge coefficients of two different types of orifices which are a straight-bore orifice and a sharp-edged orifice, are predicted to obtain the critical flow conditions. The present CFD data are compared with the previous experimental results. The present computational results show that the critical mass flow rate through orifice is well predicted and it is a strong function of Reynolds number. The discharge coefficient increases with the orifice diameter.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1998년도 춘계학술발표회논문집(1)
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• pp.425-430
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• 1998

SMART 관류형증기발생기의 유동 불안정성을 분석할 수 있는 시간영역-비선형 해석모델을 개발하였다. 해석모델은 일차계통 모델을 포함하고 있으며 이차측 튜브 양단에 일정압력 경계조건을 이용하고 내부에서는 평형 균질 이상유동 모델을 도입하였다. 기존의 정상 상태 및 임계조건에 대한 실험 결과와 개발된 해석모델 모델을 이용한 계산 결과를 비교한 뒤 임계점 이후 나타나는 진동의 특성을 분석하였다. 개발된 해석모델은 SMART 관류형증기발생기에서 발생할 수 있는 유동 진동의 특성과 영향을 파악하고 유동 불안정성을 막기 위한 입구 오리피스 설계의 목적에 활용할 수 있을 것이다.

• 대한기계학회논문집B
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• 제23권10호
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• pp.1240-1247
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• 1999

Particle motion through a disk type critical orifice placed in a 3.0cm diameter chamber has been studied numerically. In the simulation, the velocity field is solved using Pantankar's SIMPLER algorithm for the compressible flow and convergence of the computation is confirmed if the mass source at each control volume is smaller than $10^{-7}$. The particle motion in the flow field is solved in Lagrangian method. The particle trajectories showed that the particles injected away from the center line are expanded rapidly. At lower pressures, this expansion phenomena are more dominant. At lower pressures, the clear difference in particle and air speed is showed all the way down to the exit plan. It was found that particles with Stokes number of ca.2.5 tend to focus close to the center line very well except the particles travelling near the wall. However, particles with Stokes number greater than ca.2.5 show a tendency to cross the center line.

• 설비공학논문집
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• 제17권12호
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• pp.1106-1112
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• 2005

An experimental investigation was performed to develop an empirical correlation of R-410A flowing through short tube orifices working near the critical region. Tests were executed by varying upstream pressure from 2,619 kPa to 4,551 kPa, and upstream subcooling from 2.8 and $11.1^{\circ}C$. The experimental data were represented as a function of major operating parameters and short tube diameter. As compared to mass flow trends at normal upstream pressures, flow dependency on upstream subcooling became more significant at high upstream pressures due to a higher density change. Based on the database obtained from this study and literature, an empirical correlation was developed from a power law form of dimensionless parameters generated by the Buckingham Pi theorem. The correlation yielded good agreement with the data. Approximately $92\%$ of the data were correlated within a relative deviation of $5\%$.

• 한국분무공학회지
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• 제28권2호
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• pp.89-96
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• 2023

This study presents a numerical simulation investigating hydrodynamic characteristics of high-temperature hydrocarbon aviation fuel injected through a plain orifice injector. The analysis encompassed the temperature range up to the critical point, and the obtained results were compared with prior experimental observations. The analysis unveiled that the injector's exit pressure remains equivalent to the ambient pressure when the fuel injection temperature is below the boiling point. However, when the fuel temperature surpasses the boiling point, the exit pressure of the injector transitions to the saturated vapor pressure corresponding to the fuel injection temperature. Consequently, the exit pressure of the injector increases in tandem with the rapid increase of the saturation vapor pressure due to escalating fuel temperatures. This rise in the exit pressure necessitates a proportional increase in fuel injection pressure to ensure a fixed fuel mass flow rate. Furthermore, the investigation revealed that the discharge coefficient obtained by applying the exit pressure instead of the ambient pressure did exhibit no decrease, but rather was maintained at a nearly constant value, comparable to its level below the boiling point.