• Fire Science and Engineering
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• v.23 no.3
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• pp.79-84
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• 2009

The smoke control system plays the most important role in securing evacuation environment when a fire occurs in road tunnels. Smoke control methods in road tunnels are classified into two categories which are longitudinal ventilation system and transverse ventilation system. In this study it is intended to review the characteristics of smoke behavior by performing numerical analysis for calculating the optimal smoke exhaust air volume when a fire occurs in tunnels in which transverse ventilation is applied, and for obtaining the basic data required for the design of smoke exhaust systems by deriving optimal smoke exhaust operational conditions for various conditions. As a result of this study, when the critical velocity in the tunnel is 1.75m/s and 2.5m/s, the optimal smoke exhaust air volume has to be more than $173m^3/s$, $236m^3/s$ for the distance of the smoke moving which can limit the distance to 250m. In addition, in case of uniform exhaust the generated smoke is effectively taken away if the two exhaust holes near the fire region are opened at the same time.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.4
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• pp.76-86
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• 2019

The cross-flow turbine is a key hydraulic power system that is widely due to low costs, high efficiency, and low maintenance. In particular, the cross-flow turbine considered as the most suitable turbine for low head situations as it is known to operate down to 5 m of water head. However, the conventional cross-flow turbine is unsuitable for ultra-low head situations with less than a 3 m water head. In this study, we propose an inverted-type cross-flow turbine to overcome the limitations of conventional cross-flow turbines under ultra-low head situations. First, we described the limitations of conventional turbines and suggested a new turbine for the ultra-low head circumstances. Second, we investigated the performance of the new turbine using CFD analysis. Results demonstrated the effects of the design parameters, such as number of blades and rotor diameter ratio, on the performance of the suggested turbine. As a result, we developed an inverted-type cross-flow turbine with up to 60% efficiency under low water head conditions.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.2
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• pp.107-119
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• 2021

The cross-flow turbine is one of the most famous and widely used hydraulic power systems for a long time. The cross-flow turbine is especially popular in many countries and remote regions where off-grided because of its many benefits such as low cost, high efficiency at low head, simple structure, and easy maintenance. However, most modern turbines, including the cross-flow turbine, are unsuitable for the ultra-low head situation, known as less than 3m water head or zero head with over 0.5m/s flow velocity. In this study, we demonstrated a 20kW class inverted-type cross-flow turbine's performance. First, we reevaluated our previous studies and introduced how to design the inverted-type cross-flow turbine. Secondly, we fabricated the 20kW class inverted-type cross-flow turbine for the performance test. And then, we designed a testbed and installed the turbine system in the demonstration facility. In the end, we compare the demonstration with its previous CFD results. The comparing result shows that both CFD and real model fitted on guide vane angle at 10 degrees. At the demonstration, we achieved 42% turbine efficiency at runner speed 125 RPM.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.935-938
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• 2007

In suction nozzle of a vacuum cleaner, where flow-induced noise is generated mainly by flow resistance, several ideas to reduce noise are investigated. To increase fan performance, blade number is optimized and a centrifugal fan is replaced by a cross-flow fan, In addition, gear ratio of fan to drum brush is changed. It is found that fan performance is increased by adopting these methods. Next, the blade height of the fan is decreased to reduce sound pressure level, which causes inevitably decrease in fan performance. Eventually, flow-induced noise is reduced by 6.3 dBA in its overall level with the fan performance maintained.

• Journal of Biosystems Engineering
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• v.23 no.5
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• pp.457-464
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• 1998

A drying speed control system using fuzzy logic was developed in order to minimize the damage of rice quality for a large capacity continuous dryer. The performance of the system was tested at two object moisture content of 17% and 25% on a wet basis. For object moisture content of 17% on a wet basis, the final output moisture contents from 20.46%, 20.96%, 18.98% on a wet basis were 17.99%, 17.6% and 17.23% on a wet basis, respectively. For object moisture content of 25% on a wet basis, the final output moisture contents from 28.85%, 26.95%, 28.11%, 27.8% on a wet basis were 25.24%, 24.9%, 25.23% and 25.09% on a wet basis, respectively.

• Journal of computational fluids engineering
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• v.8 no.4
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• pp.50-57
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• 2003

Cross-flow fans are widely used in various applications, due to their large capacity of mass flow and size compactness. The flow field of the cross-flow fan is, however, complex and has many design parameters. Thus, the general design guide has not been sufficiently established yet and the design strategies of cross-flow fans have been mostly based on experiments. In the present study, the performance and their two-dimensional flow characteristics are numerically analyzed by using the STAR-CD(commercial computational fluid dynamics code). The simulation is done by varying the several design parameters such as the impeller blade shapes and the gap between the stabilizer and impeller. The computational results are compared with the experimental data at the fan outlet region. Finally, some helpful guides for the optimum design of cross-flow fans are proposed.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.163.1-163.1
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• 2011

세계는 지금 지구 온난화 및 화석연료의 고갈로 인해 대체 에너지 자원의 확보문제가 급속히 대두되고 있다. 이에 조류발전은 오염이 발생하지 않는 친환경 에너지원으로서, 날씨나 계절에 상관없이 항상 발전할 수 있는 신뢰성 있는 에너지이며, 높은 밀도를 가지는 작동유체가 수차에 미치는 영향 또한 크므로 지속적으로 예측이 가능한 장점을 가지고 있다. 이러한 조류에너지는 실 해역에 적용하기 위해서는 전격유효 전력이 생산 가능한 지리적 요인에 대한 고찰과 더불어 조류발전 터빈의 개념설계가 고려되어야 한다. 본 연구는 다양한 설치 공간을 형성할 수 있으며, 장, 단점이 보완될 수 있는 조류발전 터빈의 개념설계 연구 단계로서, 내부 유동 특성을 고려하여 입구를 설계하였으며, 일정한 속도로 유입되는 유량을 노즐의 장착을 통해 에너지 밀도를 높일 수 있게 된다. 이러한 개념형상 설계로 추가 작동이나, 장치의 사용 없이 양방향 발전이 가능해 진다.

• Journal of the Korea Institute of Military Science and Technology
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• v.7 no.3 s.18
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• pp.38-46
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• 2004

This paper deals with the development of simulation model for the horizontal launch at submarines in the preliminary design phase. The simulation model is composed of submarine motion model, cross flow force model in the bow of submarine, and weapon motion model In launch through torpedo tubes. Using submarine and weapon characteristics and simulation condition, it can simulate the exit velocity of weapon through torpedo tubes and reaction forces. It should be helpful for the analysis of the safe launch and design requirements in the preliminary design phase of a submarine or a weapon launched through torpedo tubes.

• 한국전산유체공학회:학술대회논문집
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• 2002.05a
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• pp.79-87
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• 2002

The present work analyzed the effect of mixing vane shape on the flow structure and heat transfer downstream of mixing vane in a subchannel of fuel assembly, by obtaining velocity and pressure fields, turbulent intensity, flow-mixing factors, heat transfer coefficient and friction factor using three-dimensional RANS analysis. NJl5, NJ25, NJ35, NJ45, which were designed by the authors, were tested to evaluate the performances in enhancing the heat transfer. Standard $\kappa-\epsilon$ model is used as a turbulence closure model, and, periodic and symmetry conditions are set as boundary conditions. The flow blockage ratio is kept constant, but the twist angle of mixing vane is changed. The results with three turbulence models( $\kappa-\epsilon$, $\kappa-\omega$, RSM) were compared with experimental data.

• 한국전산유체공학회:학술대회논문집
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• 2003.08a
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• pp.176-181
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• 2003

The cross-flow fans are widely used in various applications, due to their large capacity of mass flow and the size compactness. The flow fields of the cross-flow fan is, however, complex and it has many design parameters. Thus the general design guide has not sufficiently established yet, and the design strategies of cross-flow fans have been based on experiments. In the present study, the cross-flow fan performance and its two-dimensional flow characteristics are numerically analyzed by using the STAR-CD. The simulation is done by varying the several design parameters such as impeller blade shapes, the gap between the stabilizer and impeller. The computational results are compared with the experimental data at the fan outlet region. Finally some helpful guides for the optimum design of the cross-flow fan are proposed.