• International Journal of Advanced Culture Technology
• /
• 제10권3호
• /
• pp.295-306
• /
• 2022

The NOx removal performance of the SCR process depends on various factors such as catalytic factors (catalyst composition, shape, space velocity, etc.), temperature and flow rate distribution of the exhaust gas. Among them, the uniformity of the flow flowing into the catalyst bed plays the most important role. In this study, the flow characteristics in the SCR reactor in the design stage were simulated using a three-dimensional numerical analysis technique to confirm the uniformity of the airflow. Due to the limitation of the installation space, the shape of the inlet duct was compared with the two types of inlet duct shape because there were many curved sections of the inlet duct and the duct size margin was not large. The effect of inlet duct shape, guide vane or mixer installation, and venturi shape change on SCR reactor internal flow, airflow uniformity, and space utilization rate of ammonia concentration were studied. It was found that the uniformity of the airflow reaching the catalyst layer was greatly improved when an inlet duct with a shape that could suppress drift was applied and guide vanes were installed in the curved part of the inlet duct to properly distribute the process gas. In addition, the space utilization rate was greatly improved when the duct at the rear of the nozzle was applied as a venturi type rather than a mixer for uniform distribution of ammonia gas.

• 한국항공우주학회지
• /
• 제37권5호
• /
• pp.433-441
• /
• 2009

대부분의 자연현상은 다학제 특성을 갖고 표현된다. 유체-구조 연계(FSI) 문제의 경우 기존에 검증된 전산유체 해석 프로그램 및 구조해석 프로그램을 그대로 사용할 수 있다는 장점 때문에 약결합 방식이 일반적으로 이용된다. 그러나 약결합을 이용하여 해석을 수행하기 위해서는 서로 다른 특성을 갖는 격자시스템으로 발생되는 자료의 교환을 위해서 보간 및 사상이 필수적이다. 본 연구에서는 전역지지 및 국부지지 방사기저함수(RBF)를 이용한 보간 및 가상일의 원리를 적용한 사상의 성능을 단순 3차원 형상에 적용하여 검토하였다. 국부지지 RBF에 공간분할 트리의 일종으로 빠른 공간 탐색을 가능하게 해주는 kd-tree를 사용하는 경우 효과적으로 거대 구조물의 FSI에도 보간 및 사상이 적용 가능함을 여객기 형상의 항공기 모형을 이용하여 제시하였다.

• International Journal of Fluid Machinery and Systems
• /
• 제7권1호
• /
• pp.1-6
• /
• 2014

The propellant acquisition vane (PAV) is a key part of a vane type surface tension propellant management device (PMD), which can manage the propellant effectively. In the present paper, the fluid transportation behaviors for five PAVs with different sections were investigated by using microgravity drop tower test. Further, numerical simulation for the propellant flow in a PMD under microgravity condition was also carried out based on VOF model, and showed the similar flow pattern for PAVs to the experiment. It is noted that the section geometry of PAVs is one of the main factors affecting the fluid transportation behavior of PMD. PAVs with bottom length ratio of 5/6 and 1/2 have larger propellant transportation velocity. Based on the experiments, there were two stages during the process of propellant transportation under microgravity environment: liquid relocation and steady transportation stage. It is also recognized that there is a linear correlation between liquid transportation velocity and relative time's square root. Those results can not only provide a guideline for optimization of new vane type PMDs, but also are helpful for fluid control applications in space environment.

• Coupled systems mechanics
• /
• 제8권3호
• /
• pp.199-218
• /
• 2019

This paper studies the forced vibration of the hydro-elastic system consisting of the anisotropic (orthotropic) plate, compressible viscous fluid and rigid wall within the scope of the exact equations and relations of elastodynamics for anisotropic bodies for describing of the plate motion, and with utilizing the linearized exact Navier-Stokes equations for describing of the fluid flow. For solution of the corresponding boundary value problem it is employed time-harmonic presentation of the sought values with respect to time and the Fourier transform with respect to the space coordinate on the coordinate axis directed along the plate length. Numerical results on the pressure acting on the interface plane between the plate and fluid are presented and discussed. The main aim in this discussion is focused on the study of the influence of the plate material anisotropy on the frequency response of the mentioned pressure. In particular, it is established that under fixed values of the shear modulus of the plate material a decrease in the values of the modulus of elasticity of the plate material in the direction of plate length causes to increase of the absolute values of the interface pressure. The numerical results are presented not only for the viscous fluid case but also for the inviscid fluid case.

• Structural Engineering and Mechanics
• /
• 제85권2호
• /
• pp.247-263
• /
• 2023

The paper deals with the study of the mechanical time-harmonic forced vibration of the hydro-piezoelectric system consisting of the piezoelectric plate and compressible viscous fluid with finite depth. The exact equations of motion of the theory of linear electro-elasticity for piezoelectric materials are employed for describing the plate motion, however, the fluid flow is described by employing the linearized Navier-Stokes equations for a compressible (barotropic) viscous fluid. The plane-strain state in the plate and the plane flow of the fluid are considered and the corresponding mathematical problems are solved by employing the Fourier transform with respect to the space coordinate which is on the coordinate axis directed along the platelying direction. The expressions of the corresponding Fourier transform are determined analytically, however, the inverse transforms are found numerically. Numerical results on the interface pressure and the electrical potential are obtained for various PZT materials and these results are discussed. According to these results, in particular, it is established that the electromechanical coupling effect can significantly decrease the interface pressure.

• 한국항공우주학회지
• /
• 제38권6호
• /
• pp.547-556
• /
• 2010

항공기의 안전성 확보 및 투하되는 탄의 정확도 증대를 위한 새로운 개념의 활공비행체 개발이 많은 기업에서 진행 중에 있다. 항공기의 장착 공간 및 활공거리 증대를 고려하여 세장비가 큰 전개되는 날개를 채택하는 것이 일반적이다. 큰 세장비의 날개 구조물은 상대적으로 낮은 강성에 의하여 과도한 탄성변형 뿐 아니라 플러터 발생의 가능성이 높아지게 된다. 본 연구는 큰 세장비 날개에 대하여 유체-공력 연계기법을 이용, 구조변형에 의한 공력특성의 변화 및 플러터 발생가능성에 대하여 검토하였다. 공기력 계산을 위하여 FLUENT 코드가 구조 동특성 해석을 위하여 ABAQUS 상용코드가 사용되었으며, 국부지지 방사기저함수로 구성된 Code-bridge를 이용한 입력 자료의 보간 및 사상을 수행하였다. 해석 결과 고려된 활공 조건에서 구조 변형에 의한 공력 특성의 변화가 발생하는 것이 관측되었으며, 이에 의한 진동도 계속적으로 발생되는 것으로 표현되었다.

• 한국컴퓨터정보학회논문지
• /
• 제15권4호
• /
• pp.99-106
• /
• 2010

본 논문에서는 MFC(Mass Flow Controller) 유닛으로부터 전송된 유체의 압력을 모니터하고 흐름 제어 기능을 수행하는 유체 유동 모니터링 시스템을 제안한다. 이 시스템은 MFC 유닛과 채널 디바이스, 모니터 및 관리 소프트웨어로 구성된다. MFC 유닛은 유체 압력 값을 측정하여 채널 디바이스로 전송하고, 채널 디바이스는 MFC 유닛과 모니터 및 관리 소프트웨어간의 입출력 인터페이스를 제공하는 기능을 한다. 모니터 및 관리 소프트웨어는 각 채널의 MFC 유닛에서 실시간으로 측정한 유체 압력 값을 모니터링하여 분석하고 제어한다. 이 소프트웨어는 20개의 채널과 0.1의 모니터링 주기로 구성하여 1초당 200개 즉, 1시간당 72만개의 데이터를 처리한다. 이때 입력 데이터 수의 증가에 따라 저장 공간도 비례하여 증가한다. 이러한 데이터 수의 증가와 저장 공간의 증가는 데이터 조회 성능을 저하시키기 때문에 데이터를 효율적으로 관리할 수 있는 변경값 감지 기법과 변경 범위 감지 기법으로 구현한다.

• 한국항공우주학회지
• /
• 제36권6호
• /
• pp.532-540
• /
• 2008

최근 구조변형을 고려한 항공기의 공력특성을 계산하는데 필요한 CFD와 CSD 기법이 연계된 FSI 시스템에 관한 관심이 증대하고 있다. 본 연구에서는 유체유발 구조 변형을 고려한 수렴된 구조형상에 대한 공력특성 예측을 위해 유체-구조 연계 시스템인 FSI(Fluid- Structure Interaction)를 구축하였다. 각 모듈의 연계, 특히 CSD와 CFD의 결합 및 변형된 형상에 대한 공력격자 재생성을 위해 VSI(Volume Spline Interpolation)와 격자 변형 코드를 개발하였으며, 공력과 구조의 해석 모듈로 상용 프로그램인 FLUENT와 NASTRAN을 사용하였다. 구축된 시스템을 DLR-F4 날개에 적용하여 정적 유체-구조 연구를 수행하였으며, 그 결과 마하수 0.75에서 변형된 형상에 대한 양력 및 항력 계수는 약 20.26%, 18.5% 감소하는 것으로 나타났다.

• 한국환경보건학회지
• /
• 제28권5호
• /
• pp.13-21
• /
• 2002

This study analyzed the characteristic of basic river structure, a flood level, the tree planting recommendation and syn thetic design, in order to establish a basic plan for preparing a natural practical area of environmental ecosystem at Bukchun and its surroundings. It was also investigated based on the opinion of citizens, geographical condition and the equipment/utilization examination of Bukchun which were included ecological circumstances, and thus provided a composite item for managing the natural river. This study also considered the development of the river in terms of culture, environment and ecology concept. The results were summarized as followed. Bukchun showed that the speed of a funning fluid is very fast on a period of flood. but very slow in a period of water shortage about 0.02 m/s. To prevent the speed change of a running fluid by a steep slope in a riverbed, there established Dongchun sluice gates under a bridge, including three sluice gates under a bridge, but there occurred extremely a riverbed erosion and corrosion section. The result of comparison between real flood degree and prediction flood data, there should perform a countermeasure the riverbed structure regulation of this area. Also, it was needed an exhaustive flood management in summer. According to the Bukchun and Hyungsangang riverbed investigation, there were needed preparation for natural/practical area and ecology Park development in the future. This study was investigated tree Planting/flower/blossom around the Bukchun and its surroundings. It was recommended willow, Italian poplar, bamboos and cherry blossoms in the Hyungsangang and Bukchun. There exist together historical space, environment space iud have enough possibility both natural learning space and civil rest space. And, it is possible to compose ecology natural learning and experimental area.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 2003년도 하계종합학술대회 논문집 V
• /
• pp.2713-2716
• /
• 2003

This paper presents a dynamic manipulability analysis method of the limb moving in viscous fluid. The key idea of the presented method is that the boundary of joint velocity can be converted to the velocity-dependant dynamic manipulability polytope through the coriolis, centrifugal and drag terms in dynamic equation. The velocity-dependant dynamic manipulability polytope is added to the inertial and restoring force manipulability polytope to get overall manipulability polytope of the limb moving in the fluid Each of the torque and velocity bounds arc considered in the infinite norm sense in joint space, and the drag force of a limb moving in fluid viscous is modeled as a quadratic form An analysis example with proposed analysis scheme is presented to validate the method.