• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• 제28권1호
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• pp.35-41
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• 2016

With the assumption that the performance of a catalyst is guaranteed and that the performance of an SCR reactor is influenced by the uniformity of fluid flow into the catalyst, this study carried out a numerical analysis of flow uniformity, which is an important design factor in SCR reactors. CFD was used to grasp flow uniformity and flow characteristics inside the SCR reactor. As for the flow uniformity, analysis was carried out on the velocity and direction of the fluid flowing into the front of the first SCR reactor. Numerical analysis was carried out in terms of the area ratios of the mixing evaporator to the catalyst for 500 PS SCR, 1 : 1.9, 1 : 3.1, 1 : 4.5, and 1 : 7.0. The results showed that the larger the area ratio, the smaller the flow uniformity. On the basis of these results, the flow uniformity of the modified SCR reactor is 77%. A guidevane was installed to improve flow uniformity, and attempts were made to grasp the flow uniformity based on the shape of the guide vane. The shape of the guide vane was cylindrical, and numerical analysis was carried out for cases with two cylinders and three cylinders. As a result of the numerical analysis, it was found that while there was no great difference between 82.7% with two cylinders and 81.7% with three cylinders, the effects of the installation of the guide vane on the improvement of flow uniformity were indisputable.

• Transactions of the Korean Society of Mechanical Engineers B
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• 제25권10호
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• pp.1281-1292
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• 2001

Experiments were done for the comparison of performance and flow characteristics between a two -stage axial flow fan and a counter-rotating axial flow fan. Each stage of the two -stage axial flow fan used fur the present study has an eight bladed rotor and thirteen slater blades. The front and the rear rotor of the counter - rotating axial flow fan have eight blades each and are driven by coaxial counter ro latins shafts through a gearbox located between the rear rotor and the electric motor. Both of the two axial fan configurations have identical rotor blades and the same operating condition fur the one -to-one comparison of the two. Performance curves of the two configurations were obtained and compared by varying the blade pitch angles and axial gaps between the blade rows. The fan characteristic curves were obtained following the Korean Standard Testing Methods for Turbo Fans and Blowers (KS B 6311). The fa n flow characteristics were measured using a five-hole probe by a non-nulling method. The velocity profiles between the hub and tip of the fans were measured and analyzed at the particular operating condition s of peak efficiency, minimum and maximum pressure coefficients. The peak efficiency of the counter-rotating axial fan was improved about 2% respectively, compared with the two stage axial fan. At the minimum pressure coefficient point of the two stage axial fan, the fan inlet flow patterns show that axial velocity highly decreased in the vicinity of the blade tip region. Also, the reverse flow took place at the blade tip.

• Transactions of the Korean Society of Automotive Engineers
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• 제24권6호
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• pp.677-683
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• 2016

In this study, the pressures due to air resistances on the models of 1, 2, 3 and 4 as the automotive bodies grafted on various spoilers are investigated through the flow analysis. Model 1 has the flat type and model 2 has the shape that a flat plane is projected. Model 3 is attached with the slanted plate and model 4 has the shape that two slanted plates are installed on both sides. At the flow streams on the models of 1, 2, 3 and 4, the flow velocities are shown to become highest above the roofs of automotive bodies. The maximum flow velocities are also shown at the beginning points at the roofs of car bodies on the side planes of automotive bodies. The maximum pressures of 102,500 to 102,553 Pa as air resistances are shown at the bumpers of the front car bodies. The flow velocities on the inlet and middle planes become nearly same at the models of 1, 2, 3 and 4. But these velocities on the inlet plane at model 2 projected with the spoiler of flat plate become lower than the models of 1, 3 and 4. The air streams throughout the models become uniform at all models. The flow stream is shown most uniformly at model 2 projected with the spoiler of flat plate. But the flow stream is shown most irregularly at model 3 projected with the spoiler of slanting plate. By using the result of this flow analysis, it is thought to reduce the power of car effectively in driving by changing the configuration of automotive spoiler.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.719-724
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• 2003

The present experimental study deals with noise reduction and improvements in cooling performance in a plasma display panel(PDP) television (TV). To reduce the noise, the effects of installation parameters are studied. The experimental parameters under investigation are the distance between the fan and the rear case of a PDP TV, position of the strut on the fan, and the fan RPM. The variance of RPM is the most significant facto., and a 250 RPM decrease from 910 RPM causes about 4㏈(A) reduction in the system noise. To increase performance, flow characteristics are investigated by using a visualization technique and measuring the volume flow rate. The visualized results show that a radial direction flow due to large system resistance is significant, and an axial velocity oscillation is observed from the measurement of the volume flow rate. To prevent both a radial direction flow and an axial velocity oscillation, sponges are inserted in the space between f3n and the rear case. Inserted sponges improve the volume flow rate of cooling fans up to 32% since they convert a radial direction flow to an axial direction flow. Also an axial velocity oscillation with large amplitude and low RPM disappears. Increasing volume flow rate causes the PDP TV to improve its cooling performance. Additionally the same volume flow rate can be obtained with a decreased fan speed due to the inserted sponge. Noise reductions of 4.2 ㏈(A) at the rear and 1.1 ㏈(A) at the front of the TV are obtained by the decreased RPM. An increase of 10% of the volume flow rate is also achieved by inserting sponges.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제21권1호
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• pp.387-392
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• 2020

This paper proposes a flow-rate control system for industrial valves. Industrial valves are used in piping systems to control the flow rate and pressure. In general, valves used in pipelines are classified into globe valves, butterfly valves, and ball valves according to the shape. Motor, hydraulic, and pneumatic systems are used for operating valves. The flow meter should measure the flow rate when configuring the flow-rate control system. On the other hand, because the flow rate of the valve can be expressed by flow coefficient, a control scheme is proposed using the pressure deviation, which measures at the front and rear of the valve. The transfer function for the valve, according to the control input, was estimated using the signal compression method. Based on the induced transfer function, the disturbance observer was designed to improve the command following the performance of the valve stem. The performance of the proposed control method is compared with the flow-rate control result using the flow meter used.

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2006년도 추계학술대회 논문집
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• pp.17-20
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• 2006

Passenger safety is fundamental factor in automobile. Among much equipment for passenger safety, the air bag system is the most fundamental and effective device. Beside of the front air bag system which installed on most of all automobiles, a curtain-type air bag is increasingly adapted in deluxe cars fur protecting passengers from the danger of side clash. Curtain type airbag system consists of inflator housing, fill hose, curtain airbag. Inflator housing is a main part of the curtain-type air bag system for supplying high-pressure gases to deploy the air bag-curtain. Fill hose is a passageway to carry the gases from inflator housing to each part of curtain airbag. Therefore, it is very important to design the vent holes of fill hose for good performance of airbag deployment. But, the flow information from vent holes of fill hose is very limited. In this study, we measured instantaneous velocity fields of a high-speed flow ejecting from the vent holes of fill hose using a dynamic PIV system. From the velocity Held data measured at a high frame-rate, we evaluated the variation of the mass flow rate with time. From the instantaneous velocity fields of flow ejecting from the vent holes in the initial stage, we can see a flow pattern of wavy motion and fluctuation. The flow ejecting from the vent holes was found to have very high velocity fluctuations and the maximum velocity was about 480m/s at 4-vent hole region. From the mass flow rate with time, the accumulated flow of 4-vent hole has occupied about 70% of total flow rate.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• 제47권2호
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• pp.90-97
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• 2019

Sparkjet actuator, also known as plasma synthetic jet actuator (PSJA), is an active flow control device that has possibility of controling supersonic flow. This actuator utilizes arc plasma to deposit energy onto the gas inside the cavity to raise temperature and pressure. A change in the state of the fluid inside the cavity generates pressure waves and momentum jet, and they are exhausted through out the orifice exit and disturb external flow field. Since the cavity flow is affected by arc plasma, which is an equilibrium plasma and have generated equilibrium flow, the equilibrium state of air should be considered in order to analyze the flow of sparkjet actuator. In this study, numerical program for equilibrium flow was developed for the use of sparkjet actuator analysis. The developed program was validated by comparing the time - accurate jet front positions with the reference result. Then, impulse characteristics of the actuator in the atmospheric quiescent air were explained.

• KSCE Journal of Civil and Environmental Engineering Research
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• 제33권5호
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• pp.1999-2007
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• 2013

The key characteristics of two-lane-and-two-way traffic flow are platoon and overtaking caused by low-speed vehicle such as truck. In order to develop two-way traffic flow model comprised of CF(car-following) and overtaking model, it is essential to develop a car-following model which is suitable to two-way traffic flow. Short distance between vehicles is caused when a high-speed vehicle tailgates and overtakes foregoing low-speed vehicle on two-way road system. And a vehicle following low-speed vehicle decides to overtake the front low-speed vehicle using suitable space within the headway distribution of opposite traffic flow. For this reason, a two-way CF model should describes not only running within short gap but also headway distribution. Additionally considering domestic two-way-road size, there is a on-going need for large-network simulation, but there are few studies for two-way CF model. In this paper, a two-way CA model is developed, which explains two-way CF behavior more realistic and can be applied for large road network. The experimental results show that the developed model mimics stop-and-go phenomenon, one of features of congested traffic flow, and efficiently generates the distribution of headway. When the CF model is integrated with overtaking model, it is, therefore, expected that two-way traffic flow can be explained more realistically than before.

• 한국해양학회지
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• 제29권3호
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• pp.296-303
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• 1994

Rotating right cylinder of rigid sloping boundaries(top-bottom) is filled with two-layered fluid. External fluid which has the same density as the lower-layer is pumped through the rim boundary at the bottom, and this induces uniform vertical velocity in the interior that produces the Sverdrup type motion such as southward flowing western boundary current with northward interior horizontal motion. The rigid sloping upper boundary meets with lower layer to simulate so called "polar front", and the upper-layer motion influenced by the lower-layer flow has been observed. Barotropic motion in the western part of the basin while baroclinic motion in the eastern half is always present. In particular, both southward flowing eastern boundary flow and western boundary flow meets near the western wall and it induces northward western boundary flow to separate from the boundary With increased ${\beta}$-effect on the upper0layer the width of western boundary decreases and the separated western boundary flow moves into the interior to form an eddy-like motion. Baroclinic Rosebay wave clearly observed in the easter boundary slowly propagates to the west but it seems to be decayed before travelling to the western boundary. A local topograpic effect imposed on the lower-layer causes very sensitive response of upper layer boundary flows. In the east standing0wave0like features are observed in the west whereas the width of the boundary increases without any evidence of the separation of the western boundary flow.This may be due to the gact that even the lower-lauer barotropic motion feels the topography its influence does not propagate into the upper-layer. With large ${\beta}$-effect on the upper-layer,relatively large scale waves whose wavelengths are greater than the internal radius deformation exist in the interior.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제15권6호
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• pp.3950-3960
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• 2014

In this study, the drag forces on a submerged square cylinder were analyzed using a three dimensional hydrodynamic model. The numerical results were compared with the experimental results to check the reliability of the numerical simulations, and the characteristics of the drag forces with the relative depths were analyzed by analyzing the pressure acting on the cylinder surface, which are normally difficult to measure experimentally. The numerical results showed that the drag forces acting on a submerged square cylinder originate mainly from the pressure forces, and component of the shear forces decreased with increasing relative depth. The pressure coefficient distributions showed that in the case of a low relative depth, a relatively high pressure was formed in the front of a cylinder, and a relatively low pressure was formed in the rear, which gives a high drag coefficient. In a high relative depth, the pressure in the front decreased and pressure in the rear increased, which is a similar phenomenon to that normally observed in two dimensional square cylinder flow. The effect of the static pressure was analyzed and the surface elevation difference between the front and rear zone of a cylinder has a limited effect on the drag forces. Finally, the numerical results showed that the drag forces acting on a submerged square are dominated by the dynamic pressure formed by three dimensional flow and the distribution of local surface elevation.