• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.5
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• pp.46-53
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• 2001

To optimize the intake flow condition in the heavy-duty LPG SI engine, five different swirl ratios of intake port were investigated experimentally by oil spot method, LDV and single cylinder engine test. The flow characteristics near the piston surface were observed by oil spot method and magnitudes of swirl flow were measured quantatively by LDV method in the steady flow rig. The engine performances of various swirl flow were also tested with the heavy-duty LPG SI single cylinder engine. In the results, high swirl ratio, above $R_s$=2.3, was not suitable to develope a stable flame kernel and to produce high engine performance. Especially it was more serious under lean burn conditions, since turbulence intensity was smaller than bulk flow though those are increased together. These results were also confirmed by LDV measurement and oil spot method. On the contrary, low swirl ratio($R_s$=1.3) is not good to propagate a flame since the turbulence intensity and bulk flow are vanished during compression stroke and low swirl ratio has too weak initial energy for stable combustion. Therefore, the of optimized swirl ratio f3r the heavy-duty LPG engine in this work was found around $R_s$=2.0.

• Journal of computational fluids engineering
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• v.17 no.4
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• pp.1-8
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• 2012

During a reactor normal operation, two parallel 50% capacity cooling pumps circulate primary coolant to remove the fission reaction heat of the reactor through heat exchangers cold by a cooling tower. When one pump is failure, the other pump shall continuously circulate the coolant to remove the residual heat generated by the fuels loaded in the reactor after reactor shutdown. It is necessary to estimate how much flow rate will be supplied to remove the residual heat. We carried out a flow network analysis for the parallel primary pumps based on the piping network of the primary cooling system in HANARO. As result, it is estimated that the flow rate of one pump increased about 1.33 times the rated flow of one pump and was maintained within the limit of the cavitation critical flow.

• Journal of Navigation and Port Research
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• v.32 no.9
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• pp.717-722
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• 2008

We have proposed and demonstrated an gas-flow sensor using optical fiber bragg grating(FEG). The flow sensor has no electronics and no mechanical parts in its sensing part and the structure is th11s simple and immune to electromagnetic interference(EMI). The FEG sensor was consisted qf the sensing element and a coil heater. The metal coil was used to supply the current to the FEG. While some currents supply to the coil, the refractive index of the FEG under the coil is changed and thus the wavelength shift of fiber optic sensor was induced In this work, the wavelength shift according to flow-rate was experimentally studied and was used to evaluate the gas flow-rate in a gas tube. As a result, it was possible to measure the flow-rate in a linear range from 5 to $20{\ell}/min$ with a resolution of approximately $1{\ell}/min$ at the applied currents of 100 mA and 120 mA. The measured sensitivities were $15.3\;pm/\ell/min$ for 100 mA and $20.2\;pm/\ell/min$ for 120 mA.

• Journal of the Korean Society of Visualization
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• v.14 no.2
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• pp.12-17
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• 2016

In this work, we investigate the flow velocity controllability of a diffuser-type multiple hydrofoil duct by experimental and numerical flow visualization approaches. The flow velocity controllability is analyzed by changing the angle of the hydrofoil near the outlet, which is the diffuser, while the incoming flow velocity is 0.6 m/s in the experiment. When the diffuser angle is changed from 0 to 7.5 degree, the maximum velocity inside the duct is varied from 1.35 m/s to 1.52 m/s. Also, it is shown from the numerical analysis that the maximum velocity is varied from 1.09 m/s to 1.17 m/s in the same condition. Thus, the aspect of the acceleration in the duct due to the increase of the diffuser angle is similar between the both approaches. Therefore, the multiple hydrofoil duct can be used to control the flow speed inside the duct for continuously extracting power close to a rated capacity.

• Journal of Korean Library and Information Science Society
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• v.41 no.4
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• pp.51-72
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• 2010

Csikszentmihalyi has given the term 'flow' to describe intense engagement or complete absorption in a task and behaviors. Activities as diverse as rock climbing, art, dance, motorcycling, and work has been reported as producing flow, but the most common optimal experience noted in the research is reading. This paper examines the disposition of reading flow of elementary and second students in Korea, and analyzed on the affecting factors in reading flow. Questionary for this study made of 36 items, including reading text, reading purpose, reading method etc. This study participated by 40 elementary & secondary schools, surveying 1,836 students. In order to verify the disposition and factors of reading flow used Chi-square, crosstabulation, factors by SPSS18.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.4
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• pp.1472-1480
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• 1996

The phenomena of drag reduction using small quantities of a linear macromolecules has attracted the attention of experimental investigations. It is well known that drag reduction in single phase liquid flow is affected by polymer materials, molecular weight, polymer concentration, pipe diameter and flow velocity. But the research on drag reduction in two phase flow has not intensively investigated. Drag reduction can be applied to phase change system such as chemical reactor, pool and boiling flow, and to flow with cavitation which occurs pump impellers. The purpose of the present work is to evaluate the drag reduction by measuring pressure drop, mean liquid velocity, and turbulent intensity and determine the effects of polymer additives on drag reduction in horizontal two phase flow. Experimental results show higher drag reduction using co-polymer comparing with using polyacrylamide. Mean liquid velocities increase as adding more polymer, and turbulent intensities decrease as the distance for the wall in inversed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.346-352
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• 2002

This paper is the experimental study to estimate the influence of various design parameters on the performance of mufflers with perforated tubes and through-flow partitions. Muffler types considered in the present work include through-flow chamber, through-flow chamber with partition, and cross-flow chamber. The influences of the design parameters on the performance of the mufflers can be outlined as follows. In the case of the through-f]ow type mufflers, increasing the tube thickness and the hole diameter of the perforated tubes does not change the maximum value of the transmission loss but decrease the cutoff frequency. In the case of the through-flow with partitions type mufflers, it is shown that combining a fe w short chambers and long chambers can modify the frequency locations of the resonance frequencies to optimize the performance of the mufflers. For the case of the cross-flow type mufflers, it is shown that the transmission loss of the mufflers is mainly affected by the lower porosity when the porosities are different in both sides of the plug. Overall, it is shown that performance of the through-flow type with partition type mufflers is excellent in the lower frequency region, where the cross-flow type mufflers have better performance in the higher frequency region.

• Magazine of the Korean Society of Agricultural Engineers
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• v.43 no.4
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• pp.113-119
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• 2001

Ammonia emissions during composting of hog manure mixed with sawdust were studied in four runs comprising a total of 22 pilot-scale reactor vessels. These four runs extended previous work and both verified and extended the previous conclusions. The pilot-scale vessels were 205 L insulated stainless steel drums that were aerated either continuously (high/low thermostatically controlled fans) or intermittently (5 min high fan 55 min off). Temperature ammonia emissions air flow rates carbon dioxide production and oxygen utilization moisture and dry matter reduction initial and final chemical compositions were measured. Ammonia emissions from the intermittently aerated vessels were only about 50% as great as those from the continuously aerated ones but this was found to be a result more related to total air flow than to aeration technique. All of the data for total result more related to total air flow were fitted with a linear regression line y=0.139x+29.835 where y is ammonia expressed as g of N and x is air flow in kg with $R^2$=0.6808. this general trend indicates that about 50% reduction in ammonia emissions can be achieved with 75% reduction in air flow. For the aeration techniques used the minimum oxygen level in te exhaust gas from the vessels was 5% and this is probably a resonable lower limit constraining air flow reduction. However within this constraint lower air flow now appears to be a technique that can reduce odorous ammonia emissions.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.62-68
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• 2004

A comprehensive numerical analysis has been carried out for both non-reacting and reacting flows in a scramjet engine combustor with and without a cavity. The theoretical formulation treats the complete conservation equations of chemically reacting flows with finite-rate chemistry of hydrogen-air. Turbulence closure is achieved by means of a k-$\omega$ two-equation model. The governing equations are discretized using a MUSCL-type TVD scheme, and temporally integrated by a second-order accurate implicit scheme. Transverse injection of hydrogen is considered over a broad range of injection pressure. The corresponding equivalence ratio of the overall fuel/air mixture ranges from 0.167 to 0.50. The work features detailed resolution of the flow and flame dynamics in the combustor, which was not typically available in most of the previous studies. In particular, the oscillatory flow characteristics are captured at a scale sufficient to identify the .underlying physical mechanisms. Much of the flow unsteadiness is related not only to the cavity, but also to the intrinsic unsteadiness in the flow-field. The interactions between the unsteady flow and flame evolution may cause a large excursion of flow oscillation. The roles of the cavity, injection pressure, and heat release in determining the flow dynamics are examined systematically.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.1
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• pp.217-224
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• 2003

The frost and mist in the windshield disturb the sight of driver and passengers especially in winter. This possibly leads to safety problems. In order to export automobiles to the countries of North America, the safety regulation requires the frost of selected area should be completely melted in 30 minutes. The defrost pattern and time for melting of frost are fully dependent on the flow and temperature field near the windshield. Furthermore, the flow and temperature field near the windshield are dependent on the air discharged from defrost nozzle. The present work has been done for understanding the flow features of the discharged air and internal flow within the nozzle duct. The three dimensional Navier-Stokes code was used for performing the generic A/C duct flow analysis. The present results were nearly coincided with experimental data. To perform the parametric study of the effectiveness of the number of guide vanes, the discharge angle and the location of nozzle were changed. The ratio of volume flow rate through defrost nozzle and side exit were compared to investigate the influence of parameters on the effectiveness of defrost nozzle. The velocity profiles and flow patterns of the defrost nozzle duct were also analyzed.