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Supersonic Cavity Based Combustion with Kerosene/Hydrogen Fuel

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Journal of Thermal Science 2015年第2期24卷 164-172页

作者： Rajarshi Das Jeong Soo kim heuy dong kim Department of Mechanical Engineering Andong National University School of Mechanical Engineering Pukyong National University

A comparative study with kerosene and hydrogen fuel in a model scramjet combustor has been carried out nu- merically. The effect of fuel-air equivalence ratio on the flow field properties in a cavity based mixing mechanism at a freestream Math number of 2.08 has been probed. The investigation has been carried out in a two dimension- al numerical model where a cavity of length to depth ratio of 2 is mounted on one of the walls of the flow channel The flow field shock structure is observed to change with the change in fuel-air equivalence ratio. Total pressure loss is observed to depend both on fuel air equivalence ratio and the fuel type. The spread of fuel in the test sec- tion shows marked variation with the equivalence ratio. Performance of injector location on the fuel-air mixing is also probed during the course of the investigation.

关键词： Scramjet fuel-air mixing kerosene hydrogen equivalence ratio

Study on the Wiping Gas Jet in Continuous Galvanizing Line

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Journal of Thermal Science 2011年第3期20卷 242-247页

作者： Yong-Hun Kweon heuy-dong kim POSCO Technical Research Laboratories 699 Gumho-dong GwangyangJeonnam 545-090 Korea School of Mechanical Engineering Andong National UniversityAndong 760-749 Korea

In the continuous hot-dip galvanizing process, the gas-jet wiping is used to control the coating thickness of moving steel strip. The high speed gas-jet discharged from the nozzle slot impinges on the strip, and at this moment, wipes the liquid coating layer dragged by a moving strip. The coating thickness is generally influenced on the flow characteristics of wiping gas-jet such as the impinging pressure distribution, pressure gradient and shear stress distribution on the surface of strip. The flow characteristics of wiping gas-jet mentioned above depends upon considerably both the process operating conditions such as the nozzle pressure, nozzle-to-strip distance and line speed, and the geometry of gas-jet wiping apparatus such as the height of nozzle slot. In the present study, the effect of the geometry of nozzle on the coating thickness is investigated with the help of a computational fluid dynamics method. The height of nozzle slot is varied in the range of 0.6mm to 1.7mm. A finite volume method (FVM) is employed to solve two-dimensional, steady, compressible Navier-Stokes equations. Based upon the results obtained, the effect of the height of nozzle slot in the gas-jet wiping process is discussed in detail. The computational results show that for a given standoff distance between the nozzle to the strip, the effective height of nozzle slot exists in achieving thinner coating thickness.

关键词： Gas-Jet Wiping Hot-Dip Galvanizing Impact Pressure Coating Thickness

The Effect of Diffuser Angle on the Discharge Coefficient of a Miniature Critical Nozzle

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Journal of Thermal Science 2010年第3期19卷 222-227页

作者： Jae Hyung kim heuy dong kim Toshiaki Setoguchi School of Mechanical Engineering Andong National UniversityAndong760-749Korea Department of Mechanical Engineering Saga University1HonjoSagaJapan

Many researches on critical nozzles have been performed to accurately measure the mass flow rate of gas flow,and to standardize the performance as a flow ***,much interest is being paid on the measurement of very small mass flow rate in industry fields such as MEMS ***,the design and performance data of the critical nozzles obtained so far have been applied mainly to the critical nozzles with comparatively large diameters,and the works available on miniature critical nozzles are *** the present study,a computational fluid dynamics method has been applied to investigate the influence of the diffuser angle on discharge coefficient of the miniature critical *** computations,the throat diameter of critical nozzle is varied from 0.2 mm to 5.0 mm and the diffuser angle is changed from 2 deg to 8 *** computational results are validated with some experimental data *** results show that the present computational results predict appropriately the discharge coefficient of the gas flows through miniature critical *** is known that the discharge coefficient is considerably influenced by the diffuser angle,as the throat diameter of nozzle becomes small below a certain *** implies that the miniature critical nozzles should be carefully designed.

关键词： Compressible Flow Critical Nozzle Compressible Flow Discharge Coefficient Diffuser Configuration Reynolds Number

Numerical Simulation of Flow Characteristics in Micro Shock Tubes

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Journal of Thermal Science 2015年第3期24卷 246-253页

作者： Guang Zhang Toshiaki Setoguchi heuy dong kim Department of Mechanical Engineering Andong National University Department of Mechanical Engineering Saga University

Recently micro shock tubes have been widely used in many engineering and industrial fields, but the characteristics of unsteady flow are not well known to date in micro shock tubes. Compared to conventional shock tubes with macro scales, flows related to shock waves in micro shock tubes are highly complicated. Stronger viscous and dissipative interactions make shock wave dynamic behaviors significantly different from theoretical predictions. In the present study, a CFD work was applied to the unsteady compressible Navier-Stokes equations which were solved using a fully implicit finite volume scheme. The diaphragm pressure ratio and shock tube diameter were varied to investigate their effects on micro shock tube flows. Different wall boundary conditions were also performed to observe shock wave and contact surface propagation with no slip and slip walls. Detailed flow characteristics at the foot of shock wave and contact surface propagation were known from the present numerical simulations.

关键词： Micro shock tube Shock wave propagation Slip wall Unsteady flow CFD

Computational Study of Performance Characteristics for Truncated Conical Aerospike Nozzles

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Journal of Thermal Science 2017年第6期26卷 483-489页

作者： Prasanth P Nair Abhilash Suryan heuy dong kim Department of Mechanical Engineering College of Engineering Trivandrum Department of Mechanical Engineering Andong National University

Aerospike nozzles are advanced rocket nozzles that can maintain its aerodynamic efficiency over a wide range of altitudes. It belongs to class of altitude compensating nozzles. A vehicle with an aerospike nozzle uses less fuel at low altitudes due to its altitude adaptability, where most missions have the greatest need for thrust. Aerospike nozzles are better suited to Single Stage to Orbit （SSTO） missions compared to conventional nozzles. In the cur- rent study, the flow through 20% and 40% aerospike nozzle is analyzed in detail using computational fluid dy- namics technique. Steady state analysis with implicit formulation is carried out. Reynolds averaged Navier-Stokes equations are solved with the Spalart-AUmaras turbulence model. The results are compared with experimental results from previous work. The transition from open wake to closed wake happens in lower Nozzle Pressure Ratio for 20% as compared to 40% aerospike nozzle.

关键词： aerospike nozzle plug nozzle advanced rocket nozzles thrust coefficient base pressure.

Study of Spiral Flow Generated through an Annular Slit

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Journal of Thermal Science 2005年第2期14卷 97-102页

作者： Tae Hun kim Shigeru MATSUO Toshiaki SETOGUCHI heuy-dong kim Graduate school of Science and Technology Saga University 1Honjo-machiSaga shiSaga 840-8502JapanDepartment of Mechanical Engineering Saga University1Honjo-machiSaga shiSaga 840-8502JapanDepartment of Mechanical Engineering Saga University1Honjo-machiSaga shiSaga 840-8502JapanSchool of Mechanical Engineering College of Natural ScienceAndong National University388Song Cheon DongAndongKyung PookKorea

The effect of pressurized air inlets in the reservoir upstream of the annular slit on characteristics of the axial and tangential velocity components is investigated numerically, and the mechanism of occurrence of spiral nozzle flow is clarified. In simulations, Unified Platform for Aerospace Computational Simulation (UPACS) is used. The governing equations under consideration are the unsteady compressible Navier - Stokes. A second-order finite volume scheme with MUSCL (Roe scheme) is used to discretize the spatial derivatives, and a second order-central difference scheme for the viscous terms, and a MFGS (Matrix Free Gauss Seidel) is employed for time integration. Spalart-Allmaras model was used as a turbulence model. The results obtained are compared with velocity distributions in the experiment measured by the two-component fiber optic laser Doppler velocimeter system. The existence of discrete pressurized air inlets that leads to the occurrence of asymmetrical characteristics is a very important factor for the formation of spiral flow.

关键词： spiral nozzle flow Coanda effect convergent nozzle annular slit simulation.

Theoretical and Computational Analyses of LNG Evaporator

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Journal of Thermal Science 2017年第2期26卷 132-137页

作者： Palani Kumar Chidambaram Yang Myung Jo heuy dong kim FMTRC Daejoo Machinery Co Ltd Department Mechanical Engineering Andong National University

Theoretical and numerical analysis on the fluid flow and heat transfer inside a LNG evaporator is conducted in this work. Methane is used instead of LNG as the operating fluid. This is because; methane constitutes over 80% of natural gas. The analytical calculations are performed using simple mass and energy balance equations. The analytical calculations are made to assess the pressure and temperature variations in the steam tube. Multiphase numerical simulations are performed by solving the governing equations(basic flow equations of continuity, momentum and energy equations) in a portion of the evaporator domain consisting of a single steam pipe. The flow equations are solved along with equations of species transport. Multiphase modeling is incorporated using VOF method. Liquid methane is the primary phase. It vaporizes into the secondary phase gaseous methane. Steam is another secondary phase which flows through the heating coils. Turbulence is modeled by a two equation turbulence model. Both the theoretical and numerical predictions are seen to match well with each other. Further parametric studies are planned based on the current research.

关键词： LNG Evaporator Analytical Calculation Numerical Simulation

Numerical Study of Shock Tube Flows with Homogeneous and Heterogeneous Condensations in Rarefaction Wave

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Journal of Thermal Science 2010年第4期19卷 326-331页

作者： Junji Nagao Shigeru Matsuo Toshiaki Setoguchi heuy dong kim Graduate School of Science & Engineering Saga University1 Honjo-machiSaga-shiSaga840-8502Japan Department of Advanced Technology Fusion Saga University1 Honjo-machiSaga-shiSaga 840-8502Japan Institute of Ocean Energy Saga University1 Honjo-machiSaga-shiSaga 840-8502Japan. School of Mechanical Engineering Andong National University388Songcheon-dongAndong 760-749Korea

Shock tubes are devices in which the state of a gas is changed suddenly from one uniform state to another by the passage of shock and expansion *** the theory of ideal shock tube flow,it is customarily assumed that the unsteady expansion and shock waves generated by diaphragm rupture are a perfectly centered plane ***, such waves are generally not centered,or may not even by plane in *** the present research,the time-dependent behavior of homogeneous and heterogeneous condensation of moist air in the shock tube is investigated by using a computational fluid dynamics ***,the numerical and experimental studies were carried out in order to investigate the effect of the diaphragm rupture process on the flow characteristics of expansion and shock waves generated near the diaphragm.

关键词： shock tube homogeneous condensation heterogeneous condensation diaphragm rupture

Supersonic Cavity Flows over Concave and Convex Walls

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Journal of Thermal Science 2016年第2期25卷 145-152页

作者： A Ran Ye Rajarshi Das Toshiaki Setoguchi heuy dong kim Department of Mechanical Engineering Andong National University Institute of Ocean Engineering Saga University

Supersonic cavity flows are characterized by compression and expansion waves, shear layer, and oscillations inside the cavity. For decades, investigations into cavity flows have been conducted, mostly with flows at zero pressure gradient entering the cavity in straight walls. Since cavity flows on curved walls exert centrifugal force, the features of these flows are likely to differ from those of straight wall flows. The aim of the present work is to study the flow physics of a cavity that is cut out on a curved wall. Steady and unsteady numerical simulations were carried out for supersonic flow through curved channels over the cavity with L/H = 1. A straight channel flow was also analyzed which serves as the base model. The velocity gradient along the width of the channel was observed to increase with increasing the channel curvature for both concave and convex channels. The pressure on the cavity floor increases with the increase in channel curvature for concave channels and decreases for convex channels. Moreover, unsteady flow characteristics are more dependent on channel curvature under supersonic free stream conditions.

关键词： Cavity flow Supersonic Flow Compressible Flow Unsteady flow Pressure Oscillation