Numerical Simulation of the Odor Spreading in a Factory

Lijo Vincent,Eun-Hwa Song(송은화),Hyun-Kyu Nam(남현규),Choon-Sik Shin(신춘식),Heuy-Dong Kim(김희동) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.11

Liquid crystal displays (LCD's) are continuously coated with some chemicals in the clean room of a factory. Spreading of these chemicals is causing serious problems both in controlling clean room quality as well as to the workers inside the factory. It is required to alleviate or properly control the offensive odor which is mainly composed of propylene glycol mono ethyl acetate, novolak resin and photo active compound. The control strategy employed is to bleed the offensive odor gas out the clean room. A full scale 3D CFD model was created with anisotropic porous media, chemical species transport with no volumetric reaction, and thermal diffusion with propane gas (tracer gas) to simulate the odor spreading. A segregated implicit solver with standard k-ε model is employed. The detailed CFD analysis made it possible to develop an effective method of ventilating the coater room and optimizing their capacities.

Study on the compressible viscous flows through a straight pipe

Vincent Lijo,김희동,Toshiaki Setoguchi,Shigeru Matsuo 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.2

When sonic nozzles of significantly smaller diameter are used as standard flow meters, the critical backpressure ratio is affected by the boundary layer at the nozzle throat. It is known that, as the flow pathway is complicated in actual valves, the critical pressure ratio differs from the ideal value. However, the effect of the boundary layer thickness on choking criteria is still controversial. Choking phenomenon in a sonic nozzle fitted with a straight circular pipe of variable length is investigated numerically and the results are compared with experimental and theoretical ones. The results show that the actual critical pressure ratio is less than the ideal value and it decreases with increase in pipe length. The effect of boundary layer thickness on main flow Mach number is also made clear in this work. In addition,sonic conductance and pressure loss in actual viscous flows computed are compared with the ISO 6358 standard.

Numerical Simulation of Compressible Gas Flows in a Micro-nozzle Using Direct Simulation Monte Carlo Method

Vincent Lijo,Heuy-Dong Kim 한국추진공학회 2013 한국추진공학회 학술대회논문집 Vol.2013 No.12

In order to obtain insight into the physics of micro-nozzle flows, numerical simulations of rarefied flows in a convergent-divergent micro-nozzle is investigated by using the Direct Simulation Monte Carlo (DSMC) method. This method can be applied to a wide range of rarefied flows within regimes that neither Navier-Stokes nor collisionless Boltzmann equations are appropriate. In the present work, the molecular collision kinetics is modeled by the variable hard sphere model and energy exchange between kinetic and internal modes is controlled by the phenomenological Larsen- Borgnakke statistical model. Simulations are performed by considering a non-reacting gas model consisting of two chemical species, N2 and O2 for various back pressures and results are presented for the computed flow field quantities. Comparisons are made with the available experimental data, and the factors which affect the solutions are discussed. This study revealed that in micro-nozzles surface effects play the main role on the flow structure. Separate calculations are also performed for the “macro-nozzle” flows and detailed comparisons between typical rarefied and continuum behaviors are made.

진공 이젝터-디퓨져 시스템내의 비정상 유동 과정에 관한 연구

Lijo Vincent,김희동(Heuydong Kim),T.Setoguchi 한국추진공학회 2009 한국추진공학회 학술대회논문집 Vol.2009 No.5

The objective of the present study is to analyze the transient flow through theejector system with the help of a computational fluid dynamics (CFD) method. An attempt is made to investigate the interesting and conflicting phenomenon of the infinite entrainment into the primary stream without an infinite mass supply from the secondary chamber. The results obtained show that the one and only condition in which an infinite mass entrainment can be possible in such types of ejectors is the generation of a re-circulation zone near the primary nozzle exit. The flow in the secondary chamber attains a state of dynamic equilibrium of pressures at the onset of the recirculation zone. A steady flow in the ejector system is valid only after this point.

진공 이젝터 시스템의 유동 컨트롤

Vincent Lijo,김희동(Heuydong Kim) 한국추진공학회 2010 한국추진공학회 학술대회논문집 Vol.2010 No.5

Supersonic ejectors are simple mechanical components, which generally perform mixing and/or recompression of two fluid streams. Ejectors have found many applications in engineering. In aerospace engineering, they are used for altitude testing of a propulsion system by reducing the pressure of a test chamber. It is composed of three major sections: a vacuum test chamber, a propulsive nozzle, and a supersonic exhaust diffuser. This paper aims at the improvement of ejector-diffuser performance by focusing attention on reducing exhaust back flow into the test chamber, since alteration of the backflow or recirculation pattern appears as one of the potential means of significantly improving low supersonic ejector-diffuser performance. The simplest backflow-reduction device was an orifice plate at the duct inlet, which would pass the jet and entrained fluid but impede the movement of fluid upstream along the wall. Results clearly showed that the performance of ejector-diffuser system was improved for certain a range of system pressure ratios, whereas the orifice plate was detrimental to the ejector performance for higher pressure ratios. It is also found that there is no change in the performance of diffuser with orifice at its inlet, in terms of its pressure recovery. Hence an appropriately sized orifice system should produce considerable improvement in the ejector-diffuser performance in the intended range of pressure ratios.

충격파 발생기를 적용한 짧은 초음속 이젝터에 관한 연구

Vincent Lijo,김희동(Heuy Dong Kim) 한국추진공학회 2010 한국추진공학회 학술대회논문집 Vol.2010 No.11

Supersonic ejectors are simple mechanical components, which generally perform mixing and recompression of two fluid streams. Ejectors have found many applications in engineering. In aerospace engineering, they are used for high altitude testing (HAT) of a propulsion system by reducing the pressure of a test chamber. It is composed of three major sections: a vacuum test chamber, a propulsive nozzle, and a supersonic exhaust diffuser (SED). This paper aims at the improvement in HAT facility by focusing attention on the vertical firing rocket test stand with shock generators. Shock generators are mounted inside the SED for improving the pressure recovery. The results clearly showed that the performance of the ejector-diffuser system was improved with the addition of shock generators. The improvement comes in the form of reduction of the starting pressure ratio and the vertical height of test stand. It is also shown that shock generators are useful in reducing the total pressure loss in the SED.

고속 제트 플럼에서의 기저압력 특성

Vincent Lijo,김희동(Heuy Dong Kim) 한국추진공학회 2011 한국추진공학회 학술대회논문집 Vol.2011 No.5

초음속 이젝터 디퓨져 시스템에서의 충격파 발생기 응용

Vincent Lijo,김희동(Heuy Dong Kim) 한국추진공학회 2011 한국추진공학회 학술대회논문집 Vol.2011 No.5

Supersonic ejectors are simple mechanical components, which generally perform mixing and recompression of two fluid streams. Ejectors have found many applications in engineering. In aerospace engineering, they are used for high altitude testing (HAT) of a propulsion system by reducing the pressure of a test chamber. It is composed of three major sections: a vacuum test chamber, a propulsive nozzle, and a supersonic exhaust diffuser (SED). This paper aims at the improvement in HAT facility by focusing attention on the vertical firing rocket test stand with shock generators. Shock generators are mounted inside the SED for improving the pressure recovery. The results clearly showed that the performance of the ejector-diffuser system was improved with the addition of shock generators. The improvement comes in the form of reduction of the starting pressure ratio and the vertical height of test stand. It is also shown that shock generators are useful in reducing the total pressure loss in the SED.

Study on Base Pressure Characteristics in Supersonic Flows

Vincent Lijo,Jong Soon Nam(남종순),Heuy Dong Kim(김희동) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.10

Numerical investigation of transient side-loads in the start-up process of a rocket nozzle

Vincent Lijo,김희동,Toshiaki Setoguchi,Shigeru Matsuo 대한기계학회 2010 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.24 No.2

A numerical investigation of transient side-loads in axisymmetric over-expanded thrust optimized contour nozzles is presented. These nozzles experience side-loads during start-up and shut-down operations because of flow separation at the nozzle walls. Two types of flow separations, FSS and RSS shock structures, also occur. A two-dimension numerical simulation was carried out over axisymmetric TOC nozzles to validate the present results and investigate oscillatory flow characteristics for start-up processes. Reynolds Averaged Navier-Stokes equations are numerically solved using a fully implicit finite volume scheme. Governing equations are solved via the coupled implicit scheme. The Reynolds Stress turbulence model is selected for this work. It was found that the present computed pressure at the nozzle walls closely matched the experimental data. The phenomenon of hysteresis was also observed between these two shock structures. The transition from an FSS to RSS pattern during the start-up process showed maximum nozzle wall pressure and fluctuations in shear stress values. Oscillatory pressure was observed on the nozzle walls with high pressure ratio. The present results show that the magnitude of nozzle wall pressure variation is high for the phenomenon of oscillation.