가스터빈 기관의 탈설계점 해석

강동진,류제욱,정평석,Kang, D.J.,Ryu, J.W.,Jung, P.S. 대한기계학회 1993 대한기계학회논문집 Vol.17 No.7

A procedure for the prediction of the off-design performance of a gas turbine engine is proposed. The system performance at off-design speed is predicted by coupling the thermodynamic models of a compressor and a turbine. The off-design performance of a compressor is obtained using the stage-stackimg method, while the Ainlay-Mathieson method is used for a turbine. The procedure is applied to a single-shaft gas turbine and its predictability is found satisfactory. The results also show that the net work output increases with the increase of the turbine inlet temperature, while the thermal efficiency is marginal. The maximum thermal efficiency at design point is obtained between the highest pressure ratio and design pressure ratio.

동익과 정익의 블레이드 개수 비가 익렬의 비정상 공기역학적 특성에 미치는 영향에 대한 수치해석적 연구

강동진(D. J. Kang),전현주(H. J. Jeon) 한국전산유체공학회 2001 한국전산유체공학회지 Vol.6 No.3

Effects of rotor-stator blade count ratio on the unsteady aerodynamic characteristics of a cascade was studied by using a Navier-Stokes code. Present Navier-Stokes code is a parallel code and works on a multi-cpu machine. It is based on the SIMPLE algorithm and uses QUICK scheme for convection terms and second order back difference for all temporal derivatives. Computations were caITicd out for two cases: case 1 is for 3 stator cascade passages subjected to two upstream wakes while case 2 is for 2 stator cascade passages subjected to three upstream wakes. Numerical solutions show that rotor-stator blade count ratio plays a significant role in the unsteady aerodynamic characteristics of the stator cascade. Case 2 shows smaller unsteady fluctuation than case 1, even if they show the same time averaged value. The smaller fluctuation of case 2 is believed due to strong interaction between unsteady vortices. The unsteady lift variation of case 2 is shown to have many high frequency fluctuations as more unsteady vortices travel around the cascade. The unsteady turbulent kinetic energy due to the upstream wake is also shown to decay faster through the cascade passage than in the free stream.

Level Set 법을 이용한 삼차원 이상유동 해석에 관한 연구

강동진(D.J. Kang),이벨리나 이바노바 이바노바(Ivelina Ivanova Ivanova) 한국전산유체공학회 2008 한국전산유체공학회지 Vol.13 No.4

We developed a three dimensional Navier-Stokes code based on the level set method to simulate two phase flows with high density ratio. The Navier-Stokes equations with consideration of the surface tension effects are solved by using SIMPLE algorithm on a non-staggered grid. The present code is validated by simulating two test problems. First one is to simulate a rising bubble inside a cube. The thickness of the interface of the bubble is shown to affect the pressure distribution around the interface. As the thickness decreases, the pressure field around the interface becomes more oscillatory. As the bubble rises, a ring vortex is shown to form around the interface and the bubble eventually develops into an ellipsoidal shape. Merge of two bubbles inside a container is secondly tested to show the robustness of the present code for two phase flow simulation. Numerical results show stable and reliable behavior during the process of merging of two bubbles. The velocity and pressure fields around the interface of bubbles are shown oscillation free during the merging of two bubbles.

Reynolds 수와 Knudsen 수가 초소형 점성펌프에 미치는 영향

강동진(D.J. Kang),이벨리나 이바노바 이바노바(Ivelina Ivanova Ivanova) 한국전산유체공학회 2008 한국전산유체공학회지 Vol.13 No.2

Effects of the Reynolds and Knudsen numbers on a micro-viscous pump are studied by using a Navier-Stokes code based on a finite volume method. The micro viscous pump consists of a circular rotor and a two-dimensional channel. The channel walls are treated by using a slip velocity model. The Reynolds number is studied in the range of 0.1~50. The Knudsen number varies from 0.01 to 0.1. Numerical solutions show that the pump works efficiently when two counter rotating vortices formed on both sides of the rotor have the same size and intensity. As the Reynolds number increases, the size and intensity of the vortex on the inlet side of the pump decrease. It disappears when the Reynolds number is larger than about Re=20. The characteristics of the performance of the pump is shown to deteriorate, in terms of mean velocity and pressure rise, as the Reynolds number increases. The Knudsen number shows a different effect on the characteristics of the pump. As it increases, the mean velocity and pressure rise decrease but the characteristics of the vortex flow remains unchanged, unlike the effect of Reynolds number.

초소형 점성펌프 성능의 수치해석적 연구

강동진(D. J. Kang) 한국전산유체공학회 2006 한국전산유체공학회 학술대회논문집 Vol.2006 No.10

초소형 점성 펌프의 Naveir-Stokes 해석

강동진(D.J. Kang) 한국전산유체공학회 2006 한국전산유체공학회지 Vol.11 No.4

Navier-Stokes simulation of the flow in a micro viscous pump is carried out. The micro viscous pump consists of a rotating circular rotor placed in a two dimensional channel. All simulation is carried out by using a finite volume approach, at the Reynolds number of 0.5, to study the performance of the micro viscous pump. Length of channel of the pump is varied to simulate the effects of the pumping load Numerical solutions show that the net flow of the pump is realized by two counter rotating vortices formed on both sides of the rotor. The volume flow rate of the pump is decreased as length of the channel is increased, while the static pressure difference across the rotor is increased The static pressure difference across the rotor is observed to be inversely proportional to the volume flow rate as inertia effects are negligibly small. The efficiency of the pump is found to reach a maximum when two counter rotating vortices on both sides of the rotor becomes to merge forming an outer enveloping vortex.

U-자형 곡관내의 유동특성에 대한 수치해석적 연구

고동훈(D.H. Koh),강동진(D.J. Kang),송동주(D.J. Song) 한국전산유체공학회 2009 한국전산유체공학회 학술대회논문집 Vol.2009 No.4

A numerical study of the flow characteristics inside a U-type circular tube is carried out in this paper. The numerical simulations carried out by using a Navier-Stokes code which is commercially available. Before detailed numerical simulations, validation of present numerical approach is made by comparing numerical solutions with experimental data. Numerical simulations are performed to study the effect of curvature on the flow characteristics inside a U-type tube. Numerical solutions show that a significant effect on the secondary flow structure in the cross section of the tube, especially in the curved section is shown when the curvature ratio, ratio of curvature to tube diameter, is smaller than about 3.5. As the curvature ratio decreases below 3.5, a counter rotating vortex is found below the primary vortex in the cross section of the tube. Another dramatic change of the flow structure is the formation of streamwise separation zone when the curvature ratio is decreased below 1.25.

U-자형 곡관내의 유동특성에 대한 수치해석적 연구

고동훈(D.H. Koh),강동진(D.J. Kang),송동주(D.J. Song) 한국전산유체공학회 2009 한국전산유체공학회지 Vol.14 No.3

A numerical study of the flow characteristics inside a U-type circular tube is carried out in this paper. The numerical simulations carried out by using a Navier-Stokes code which is commercially available. Before detailed numerical simulations, validation of present numerical approach is made by comparing numerical solutions with experimental data. Numerical simulations are performed to study the effect of curvature on the flow characteristics inside a U-type tube. Numerical solutions show that a significant effect on the secondary flow structure in the cross section of the tube, especially in the curved section is shown when the curvature ratio, ratio of curvature to tube diameter, is smaller than about 3.5, As the curvature ratio decreases below 3.5, a counter rotating vortex is found below the primary vortex in the cross section of the tube. Another dramatic change of the .flow structure is the formation of streamwise separation zone when the curvature ratio is decreased below 1.25.

스파이럴 채널을 가진 초소형 점성 펌프의 Navier-Stokes 해석

서주형(J. H. Seo),강동진(D. J. Kang) 한국전산유체공학회 2011 한국전산유체공학회지 Vol.16 No.1

The Navier-Stokes equations are solved to study the flow characteristics of a micro viscous pump. The viscous micropump is consisted of a stationary disk with a spiral shaped channel and a rotating disk. A simple geometrical model for the tip clearance is proposed and validated by comparing computed flow rate with corresponding experimental data. Present numerical solutions show satisfactory agreement with the corresponding experimental data. The tip clearance effect is found to become significant as the rotational speed increases. As the pressure load increases, a reversed flow region is seen to form near the stationary disk. The height of the channel is shown to be optimized in terms of the flow rate for a given rotational speed and pressure load. The optimal height of the channel becomes small as the rotational speed decreases or the pressure load increases. The flow rate of the pump is found to be in proportion to the width of channel.

한국어 명령어의 해석을 위한 사전의 구성

김정해(J.H.Kim),김권양(K.Y.Kim),최재혁(J.H.Choi),강동진(D.J Kang),이상조(S J.Lee) 한국정보과학회 1991 한국정보과학회 학술발표논문집 Vol.18 No.1

본 논문에서는 한국어 UNIX 명령어를 해석하는데 필요한 사전을 구성하였다 이 사전을 구성하기 위해 명령어의 유형을 수집, 분류하고 어휘를 추출하였으며, 각 어휘에 관한 형태소 정보, 구문 정보, 의미제약 정보, 의미 구조를 정립하였다. 또한 이들 정보들의 표현 방법은 자질 구조를 기반으로 하였으며, 사전에 수록된 정보의 유용성을 단일화 기반 문법인 한국어 구 구조 문법을 써서 해석기를 구현하여 검증하였다.