• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.7
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• pp.608-615
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• 2012

In this study, we analyzed the system impedance of Unmanned Aerial Vehicle avionics bay and Environmental Control System(ECS), and estimated the proper air flow rate to be supplied avionics equipments. As the result of estimation, we evaluated the performance of ECS after analysing the flow balance rate and the air flow rate about each outlet port, and simultaneously decided the flow balance rate after evaluating the thermal substantiality by the thermal analysis of avionics bay. In order to verify the property of analysis result, we conducted the flow balance test using the actual avionics equipments and finally deduced the flow rate to be met system requirements of avionics equipments. Also, as the analysis results, we verified the satisfaction of system requirements at midium altitude condition and proved the performance characteristics of an Environmental Control System(ECS).

• 한국가시화정보학회:학술대회논문집
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• 2006.12a
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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.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.680-685
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• 2008

The ejector is a simple device which can transport a low-pressure secondary flow by using a high-pressure primary flow. In general, it consists of a primary driving nozzle, a mixing section, and a diffuser. The ejector system entrains the secondary flow through a shear action generated by the primary jet. Until now, a large number of researches have been made to design and evaluate the ejector systems, where it is assumed that the ejector system has an infinite secondary chamber which can supply mass infinitely. However, in almost all of the practical applications, the ejector system has a finite secondary chamber implying steady flow can be possible only after the flow inside ejector has reached an equilibrium state after the starting process. To the authors' best knowledge, there are no reports on the starting characteristics of the ejector systems and none of the works to date discloses the detailed flow process until the secondary chamber flow reaches an equilibrium state. The objective of the present study is to investigate the starting process of an ejector-diffuser system. The present study is also planned to identify the operating range of ejector-diffuser systems where the steady flow assumption can be applied without uncertainty. The results obtained show that the one and only condition in which an infinite mass entrainment is possible is the generation of a recirculation zone near the primary nozzle exit. The flow in the secondary chamber attains a state of dynamic equilibrium at this point.

• 한국전산유체공학회:학술대회논문집
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• 2004.10a
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• pp.151-154
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• 2004

The HANARO, a multi-purpose research reactor of 30 MWth open-tank-in-pool type, has been under normal operation since its initial criticality in February, 1995. Many experiments should be safely performed to activate the utilization of the HANARO. A flow simulated test facility has been developed for the verification of structural integrity of those experimental facilities prior to loading In the HANARO. This test facility is composed of three major parts; a half-core structure assembly, flow circulation system and support system. The half-core structure assembly is composed of plenum, grid plate, core channel with flow tubes, chimney and dummy pool. The flow channels are to be filled with flow orifices to simulate similar flow characteristics to the HANARO. This paper describes an analysis of the flow distribution of the cote channel and compares with the test results. As results, the analysis showed similar flow characteristics compared with those in the test results.

• Journal of Aerospace System Engineering
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• v.2 no.2
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• pp.20-27
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• 2008

The characteristics of compressible flow are different from those of incompressible flow from the mathematical and physical point of view. Therefore, the way to solve the flowfield is different between compressible flow and incompressible flow. In general, density-based numerical algorithm is mainly used for compressible flow solver development. On the other hand, incompressible flow solver prefers to use pressure-based numerical algorithm. In this research, a compressible Navier-Stokes flow solver is developed by means of extending from pressure-based incompressible numerical algorithm to handle both compressible and incompressible flows using the same flow solver. The present flow solver is tested at various speed ranges and compared with the solutions of density-based compressible flow solver. Numerical results show a good agreement between two flow solvers.

• International Journal of Aerospace System Engineering
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• v.2 no.1
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• pp.12-17
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• 2015

Aero-optical effects induced by the flow around the optical window degrade the performance of the IR seeker, especially for the hypersonic flow. For the thermochemical non-equilibrium flow, index of refraction model and optical transmission calculation method are developed to predict the aero-optical effects. The optical distortion is discussed for the typical optical widow shape and flow condition. The influence on aero-optical effects is analyzed.

• Journal of Power System Engineering
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• v.16 no.3
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• pp.29-36
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• 2012

The computational flow analysis using LES technique was introduced to investigate the flow field improvement of an indoor RAC chassis consisting of a rear-guider, a stabilizer and a cross-flow fan. This unsteady three-dimensional numerical analysis was carried out by the commercial SC/Tetra software. The edge blocks were adopted in this study as a tool for the flow field improvement of an indoor RAC. In view of the results so far achieved, the edge blocks cause the center of an eccentric vortex to be stable along all length of a cross-flow fan, and then, the static pressure and the velocity vector show a stable distributions. In consequence, because the edge blocks eliminate a reverse flow near the edges, an exhausting flow becomes to be stable and uniform.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.407-408
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• 2006

Passenger safety is one of the most important considerations in the purchase of an automobile. A curtain-type air bag is increasingly adapted in deluxe cars for protecting passengers from the danger of side clash. Inflator housing is a main part of the curtain-type air bag system for supplying high-pressure gases to pump up the air bag-curtain. Although the inflator housing is fundamental in designing a curtain-type air bag system, flow information on the inflator housing is very limited. In this study, we measured instantaneous velocity fields of a high-speed flow ejecting from the inflator housing using a dynamic PIV system. From the velocity field 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 airbag inflator housing in the initial stage, we can see a flow pattern of broken shock wave front and its downward propagation. The flow ejecting from the inflator housing was found to have large velocity fluctuations and the maximum velocity was about 700m/s. The velocity of high-speed flow was decreased rapidly and the duration of high-speed flow over 400m/s was maintained only to 30ms. After 100ms, there was no perceptible flow.

• Journal of ILASS-Korea
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• v.5 no.1
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• pp.49-57
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• 2000

This study presents the flow visualization results, velocity and turbulence intensity measurements made within an air filter cover and entry region of a mass air flow sensor (MAFS) which is used in an induction system of 3.8L engine. Flow structure in two air filter cover assemblies were examined. The first was a clear plastic replica of the production cover while the second was a modified clear plastic cover with a geometry configured to reduce fluctuations. High speed flow visualization and laser doppler velocimetry (LDV) systems were used to reveal and analyze the flow field characteristics encountered in the sensor design process under steady flow conditions. A 40-watt copper vapor laser was used as a light source. Its beam is focused down to a sheet of light approximately 1.5mm thick. The light scattered off the particles was recorded by a 16mm high speed rotating prism camera at 5000 frames per second. A comparison of the flow patterns and LDV measurements in the original and modified air filter covers is presented to illustrate the controlling effect of the cover design on the turbulence structure formation near the bypass and on the sensor output signal. In both axial and radial planes of the main passage it was found that the turbulence flow pattern is remarkably influenced by the air filter cover and main passage configuration.

• Clean Technology
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• v.25 no.2
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• pp.153-160
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• 2019

As air pollution becomes more serious due to the increased number of diesel vessel operations, ship regulations on harmful emissions strengthen. Therefore, the development of a diesel exhaust after-treatment system for ships is required, and the higher the flow uniformity of the exhaust treatment system, the higher the treatment efficiency. With the computer software ANSYS Fluent, pressure drop and flow uniformity were used in this study to simulate flow rate with and without a baffle in both a Diesel Oxidation Catalyst (DOC) and Diesel Particulate Filter (DPF) system. The system pressure drop was found to be 38 to 40 mbar in the existing system condition, and the flow uniformity was approximately 84 to 92% at the inlet and outlet of the DOC. When the baffle was installed inside the system, the pressure increased and the flow uniformity was lowered due to an increase in flow rate. When the exhaust gas flow was reduced by 50% from $7,548kg\;h^{-1}$ to $3,772kg\;h^{-1}$, the flow uniformity at the inlet and outlet of the DOC increased by approximately 1 to 3% due to the low flow rate. In the case of DPF, the flow uniformity of exhaust gas was 98 to 99% because the uneven flow proceeded after uniformly flowing from the DOC.