• Title/Summary/Keyword: Computational Structure Dynamics

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Internal Flow Analysis of Urea-SCR System for Passenger Cars Considering Actual Driving Conditions (운전 조건을 고려한 승용차용 요소첨가 선택적 촉매환원장치의 내부 유동 해석에 관한 연구)

  • Moon, Seong Joon;Jo, Nak Won;Oh, Se Doo;Lee, Ho Kil;Park, Kyoung Woo
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.40 no.3
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    • pp.127-138
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    • 2016
  • Diesel vehicles should be equipped with urea-selective catalytic reduction(SCR) system as a high-performance catalyst, in order to reduce harmful nitrogen oxide emissions. In this study, a three-dimensional Eulerian-Lagrangian CFD analysis was used to numerically predict the multiphase flow characteristics of the urea-SCR system, coupled with the chemical reactions of the system's transport phenomena. Then, the numerical spray structure was modified by comparing the results with the measured values from spray visualization, such as the injection velocity, penentration length, spray radius, and sauter mean diameter. In addition, the analysis results were verified by comparison with the removal efficiency of the nitrogen oxide emissions during engine and chassis tests, resulting in accuracy of the relative error of less than 5%. Finally, a verified CFD analysis was used to calculate the interanl flow of the urea-SCR system, thereby analyzing the characteristics of pressure drop and velocity increase, and predicting the uniformity index and overdistribution positions of ammonia.

Numerical Analysis of Heat Transfer Characteristics of Ribbed Channels with Different Film Cooling Hole Position (필름 냉각을 위한 리브드 채널의 홀 위치에 따른 열전달 특성 수치 해석)

  • Park, Jee Min;Moon, Joo Hyun;Lee, Hyung Ju;Lee, Seong Hyuk
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.19 no.9
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    • pp.69-76
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    • 2018
  • The present study analyzed the effect of film hole position of 45 degree ribbed cooling channel on film cooling performance of gas turbine blades. We also investigated the influence of the ribs under the fixed blowing ratio. Three-dimensional numerical model was constructed and extensive simulation was conducted using the commercial code (Fluent ver. 17.0) under steady-state condition. Base on the simulation results, We investigated the cooling effectiveness, flow velocity, streamline, and pressure coefficient. Moreover, We analyzed the effect of cooling hole position on ejection of the secondary flow caused by the rib structure. From the results, It was found that internal flow of the cooling channel forms a vortex pair in the counterclockwise from the top side, and clockwise from the bottom side. For the channels with ribs, the vortex flow generated by the ribs caused a higher pressure difference near the hole outlet, resulting in at least 12% higher cooling effectiveness than the channel without ribs. Additionally, when the hole is located on the left side of the ribbed channel (Rib-Left), it can be found that the secondary flow generated by the ribs hits against wall surface near the hole to form a flow in the direction of the hole inclination angle. Therefore, It is considered that the region where the cooling gas discharged to the blade surface stays in the main flow boundary layer is wider than the other cases. In this case, The largest pressure coefficient difference was observed near the outlet of the hole, and as a result, the discharge of the cooling gas was accelerated and the cooling efficiency was slightly increased.

A Numerical Analysis on the Determination of Shock Loss Coefficient at Flared Intersection of Network-type Double-deck Road Tunnel (네트워크형 복층 도로터널 확폭구간에서의 충격손실 계수 결정을 위한 수치해석 연구)

  • Park, Yo Han;Lee, Seung Jun;Kim, Jin
    • Tunnel and Underground Space
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    • v.28 no.1
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    • pp.111-124
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    • 2018
  • The purpose of this study is to analyze ventilation design factor for network-type double-deck road tunnel that have been developed actively around the world. A numerical analysis was carried out through computational fluid dynamics (CFD) to derive shock loss coefficient that occurs due to the change in cross sectional area at both merging section and diverging section. The model used for the numerical analysis is real-scale model and the reliability of the result is secured by comparing with the coefficient of the previous studies. As a result of this study, shock loss coefficient was calculated depending on the change in cross-sectional area ratio and was higher than the result of previous studies in case of both merging section and diverging section. It is considered that the characteristics of the geometrical structure of network-type double-deck road tunnel have a great impact on shock loss coefficient. Therefore, the result of this study is expected to be helpful for more accurate ventilation design of network-type double-deck road tunnel.

Numerical Study on Characteristics of Gas Leakage in an Underground Combined Cycle Power Plant (지하 복합발전 플랜트 내부의 가스 누출 특성에 대한 수치해석 연구)

  • Bang, Joo Won;Sung, Kun Hyuk;Ryou, Hong Sun;Lee, Seong Hyuk
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.17 no.5
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    • pp.594-600
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    • 2016
  • The present study numerically investigated the gas leakage characteristics in a simplified underground combined cycle power plant. The effect of obstacles near a crack location on the gas concentration in the confined space was analyzed by using the lower flammable limit (LFL) of methane gas. When the jet flow was close to the vertical walls, the longitudinal leakage distance increased by about 60% (when an obstacles was present) compared to the case without any obstacle, because these obstacles prevented transverse flows. In addition, when an air filter was installed near to the trajectory of the gas flow, the longitudinal leakage distance was similar to the distance between the crack and obstacle, whereas the transverse leakage distance increased up to 8 times compared to the case without any obstacle. As the jet flow impacts on the obstacle and changes its direction, the gas flows recirculate. Therefore, it is necessary to consider the effect of the structure and facility locations on the trajectory of the jet flow to propose an accident prevention system in confined spaces.

Numerical Analysis of Grout Flow and Injection Pressure Affected by Joint Roughness and Aperture (절리 거칠기와 간극 변화에 따른 그라우트 유동과 주입압에 관한 수치해석적 연구)

  • Jeon, Ki-Hwan;Ryu, Dong-Woo;Kim, Hyung-Mok;Park, Eui-Seob;Song, Jae-Jun
    • Tunnel and Underground Space
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    • v.20 no.2
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    • pp.82-91
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    • 2010
  • Grouting technology is one of the ground improvement methods used in water controlling and reinforcement of rock mass in underground structure construction. It is necessarily required to find out the characteristics of grout flow through discontinuities in a rock mass for an adequate grout design and performance assessment. Laminar flow is not always applicable in simulating a grout flow in a rock mass, since the rock joints usually have apertures at a micro-scale and the flow through these joints is affected by the joint roughness and the velocity profile of the flow changes partially near the roughness. Thus, the influence of joint roughness and aperture on the grout flow in rough rock joint was numerically investigated in this study. The commercial computational fluid dynamics code, FLUENT, was applied for this purpose. The computed results by embedded Herschel-Bulkley model and VOF (volume of fluid) model, which are applicable to simulate grout flow in a narrow rock joint that is filled with air and water, were well compared with that of analytical results and previously published laboratory test for the verification. The injection pressure required to keep constant injection rate of grout was calculated in a variety of Joint Roughness Coefficient (JRC) and aperture conditions, and the effect of joint roughness and aperture on grout flow were quantified.

A Study on Numerical Calculations of Hybrid Air Pollution Control System Coupled with SDR and Bag Filter (반건식 반응기와 백필터를 결합한 하이브리드 대기오염제어 시스템의 수치해석적 연구(I))

  • Kwon, Young-Hyun;Kim, Jin-Uk;Jung, Yu-Jin;Kim, Min-Choul;Lee, Jae-Jeong;Lee, Gang-Woo;Shon, Byung-Hyun
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.11 no.11
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    • pp.4656-4663
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    • 2010
  • In this study, the 3D computational fluid dynamics (CFD) was performed in relation to the internal fluid characteristics, flow distribution, air mean ages, and residence time for the development of the most optimal model in the complex post-disposal device. As it is expected that a channeling (drift) would be made by the semi-dry reactor due to the large difference in the flow distribution by the compartment in the bag filter, a structural improvement should be urgently made for more uniformed flow distribution in the bag filter. In addition, it showed the possibility that the velocity field and distribution characteristics of the residence time could be improved through a modification to inlet structure of the spray dryer reactor. The complex post-disposal device, modified and supplemented with this analysis, integrated the semi-dry reactor and the bag filter in a single body, so it follows that the improvement can make the device compact, the installation area, the operation fee, and management more convenient.

Effect of Process Gas and Burner Gas Temperature on Reaction and Thermal Deformation Characteristics in a Steam Reformer (증기 개질기의 반응 및 열변형 특성에 미치는 공정가스와 버너가스 온도의 영향)

  • Han, Jun Hee;Kim, Ji Yoon;Lee, Jung Hee;Lee, Seong Hyuk
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.17 no.9
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    • pp.126-132
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    • 2016
  • This study numerically investigates the characteristics of chemical reactions and thermal deformation in a steam reformer. These phenomena are significantly affected by the high-temperature burner gas and the process gas conditions. Because the high temperature of the burner gas ranges from 800 to 1000 K, the reformer tubes undergo substantial thermal deformation, eventually resulting in structural failure. Thus, it is necessary to understand the characteristics of the reaction and thermal deformation under the operating conditions to evaluate the reformer tubes for sustainable, stable operation. Extensive numerical simulations were carried out using commercial CFD code (ANSYS FLUENT/MECHANICA Ver. 13.0) while considering three-dimensional turbulent flows and combined heat transfer including conduction, convection, and radiation. Structural analysis considering conjugated heat transfer between solid tubes and fluid flows was conducted using the Fluid-Solid Interaction (FSI) method. The results show that when the injection temperature of the process gas and burner gas decreased, the hydrogen production rate decreased significantly, and thermal deformation decreased by at least 15 to 20%.

Development of Air Flow Simulator in Agricultural Facility based on Virtual Reality (가상현실 기반 농업시설 공기유동 시뮬레이터의 개발)

  • Noh, Jae Seung;Kim, Yu Yong;Yoo, Young Ji;Kwon, Jin Kyung;Lee, In Bok;Kim, Rack Woo;Kim, Jun Gyu
    • Journal of Bio-Environment Control
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    • v.28 no.1
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    • pp.16-27
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    • 2019
  • Using virtual reality technology, users can learn and experience many interactions in virtual space like the actual physical space. This study was conducted to develop air flow simulator that allows farmers and consultants to consult air flow through VR devices by creating a greenhouse or pigpen model. It can help educate farmers about the importance of ventilation effects for agricultural facilities. We proposed CFD visualization system by building a virtual reality environment and constructing database of CFD and structure of agricultural facilities. After consultants can set up situations according to environmental conditions, the users experience the visualized air flow of agricultural facility according to the ventilation effects. Also it can provide a quantified environmental distribution in the agricultural facility. Currently, the CFD data in agricultural facilities are established during winter and summer. In order to experience various environmental conditions in the developed system, The experts need to run CFD data under various environmental conditions and register them in the system requirements.

A Study on the Element Technologies in Flame Arrester of End Line (선박의 엔드라인 폭연방지기의 요소기술에 관한 연구)

  • Pham, Minh-Ngoc;Choi, Min-Seon;Kim, Bu-Gi
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.25 no.4
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    • pp.468-475
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    • 2019
  • An end-line flame arrester allows free venting in combination with flame protection for vertical vent applications. End-line flame arresters are employed in various fields, especially in shipping. In flame arresters, springs are essential parts because the spring load and the spring's elasticity determine the hood opening moment. In addition, the spring has to work under a high-temperature condition because of the burning gas flame. Therefore, it is necessary to analyze the mechanical load and elasticity of the spring when the flame starts to appear. Based on simulations of the working process of a specific end-line flame arrester, a thermal and structural analysis of the spring is performed. A three-dimensional model of a burned spring is built using computational fluid dynamics (CFD) simulation. Results of the CFD analysis are input into a finite element method simulation to analyze the spring structure. The research team focused on three cases of spring loads: 43, 93, and 56 kg, correspondingly, at 150 mm of spring deflection. Consequently, the spring load was reduced by 10 kg after 5 min under a $1,000^{\circ}C$ heat condition. The simulation results can be used to predict and estimate the spring's load and elasticity at the burning time variation. Moreover, the obtained outcome can provide the industry with references to optimize the design of the spring as well as that of the flame arrester.

A Study on the Application of a Drone-Based 3D Model for Wind Environment Prediction

  • Jang, Yeong Jae;Jo, Hyeon Jeong;Oh, Jae Hong;Lee, Chang No
    • Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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    • v.39 no.2
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    • pp.93-101
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    • 2021
  • Recently, with the urban redevelopment and the spread of the planned cities, there is increasing interest in the wind environment, which is related not only to design of buildings and landscaping but also to the comfortability of pedestrians. Numerical analysis for wind environment prediction is underway in many fields, such as dense areas of high-rise building or composition of the apartment complexes, a precisive 3D building model is essentially required in this process. Many studies conducted for wind environment analysis have typically used the method of creating a 3D model by utilizing the building layer included in the GIS (Geographic Information System) data. These data can easily and quickly observe the flow of atmosphere in a wide urban environment, but cannot be suitable for observing precisive flow of atmosphere, and in particular, the effect of a complicated structure of a single building on the flow of atmosphere cannot be calculated. Recently, drone photogrammetry has shown the advantage of being able to automatically perform building modeling based on a large number of images. In this study, we applied photogrammetry technology using a drone to evaluate the flow of atmosphere around two buildings located close to each other. Two 3D models were made into an automatic modeling technique and manual modeling technique. Auto-modeling technique is using an automatically generates a point cloud through photogrammetry and generating models through interpolation, and manual-modeling technique is a manually operated technique that individually generates 3D models based on point clouds. And then the flow of atmosphere for the two models was compared and analyzed. As a result, the wind environment of the two models showed a clear difference, and the model created by auto-modeling showed faster flow of atmosphere than the model created by manual modeling. Also in the case of the 3D mesh generated by auto-modeling showed the limitation of not proceeding an accurate analysis because the precise 3D shape was not reproduced in the closed area such as the porch of the building or the bridge between buildings.