• Journal of Power System Engineering
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• v.13 no.4
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• pp.31-37
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• 2009

The purpose of this numerical study was to investigate performance characteristics for cooling tower axial fans with sweep. Performance data for the fans with various sweep angles were obtained in terms of the setting angle at a constant flow rate. Viscous flow calculations were carried out to obtain Performance data of the total pressure rise and hydraulic efficiency. A solution of the Ffowcs Williams-Hawkings equations was used to calculate the sound pressure level at three times fan diameter away from the fan. The calculated performance data well represented performance characteristics of the cooling tower axial fan. The total pressure rise and hydraulic efficiency at the same setting angle decreased with sweep angle. Sound pressure level slightly decreased for the fan with a sweep angle of 10 degree. No significant effect of the sweep geometry was found on the sound pressure level.

• Journal of computational fluids engineering
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• v.8 no.1
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• pp.1-7
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• 2003

The present study has conducted the analysis of flows in a blower with double suction. The air handling system is for supplying air flows into a plant. The present system has a couple of impellers in axial direction for enhanced flow rate. Main interest lies on the improvements of static pressure rise and total efficiency of the system. The present treatment of the reform is to secure a spatial distance between the fan and the casing of the system and change the shape of the cut-off part. The resultant performance after the reform shows increased pressure-rise and efficiency of the system

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.10 no.1
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• pp.50-57
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• 1999

A study to get the data of normal stop consonants production as preliminary study for cleft palate patients was performed. Normal Korean native 21 speakers were pronounced $VCV(V=/a/,C=/P/,/{P^1}/,/P^h/,/t/,/{t^1}/,/{t^h}/,/k/,/{k^1}/,/{k^h}/)$ syllables with natural speech rate and intensity. With intrapharyngeal pressure waveforms by pressure sensor in oropharyngeal cavity, amplitude and time duration of intrapharyngeal pressure were analyzed, and with acoustic waveforms and spectrograms, closure duration and VOT were analyzed. As results, the highest amplitude of intrapharyngeal pressure showed in alveolars and heavily aspirated consonants. Velars and unaspirated consonants were higher than bilabials and slightly aspirated ones each, in intrapharyngeal pressure. Bilabilas, alveolars and velars showed similar rise time of intrapharyngeal pressure build-up, but in decay time and total duration time, bilabials were slightly shorter than alveolars and velars, with no statistic significance. In the aspects of tensity, unaspirated consonants showed the longest rise time, heavily aspirated, the second, and slightly aspirated consonants, the shortest, which were also seen in decay time and total duration time. In closure duration, slightly aspirated consonants had the shortest closure duration, and the heavily aspirated ones, the second, and unaspirated consonants showed the longest. In VOT, heavily aspirated consonants showed the longest, slightly aspirated ones, the second and unaspirated ones showed the shortest.

• 유체기계공업학회:학술대회논문집
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• 2000.12a
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• pp.226-235
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• 2000

Two representative finite volume methods, i.e., the time marching method and the pressure correction method, were applied to 8 centrifugal compressor impeller flows, with low to very high level of pressure ratio, among which 7 impellers' experimental performance is given in the open literature. The present study is focused on the prediction differences from both methods, developed by the authors, in the pressure correction method's point of view. In all cases, the time marching method gives a satifactory solution, but the pressure correction method does not. Up to about $18\%$ less level of total-to-total pressure ratio is predicted by the pressure correction method as the level of the impeller pressure ratio increases up to about 10. The drop of total pressure ratio is caused by the underestimation of static pressure rise which seems to be attributed to inappropriate linearization and discretization of the pressure/density coupling terms in the pressure correction equation.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.3
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• pp.582-589
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• 1988

A rapid expansion of moist air or steam in a supersonic nozzle gives rise to condensation, and the total pressure of the flow is decreased due to this irreversibility of condensation phenomenon. In the present paper, the loss in total pressure during the condensation process has been studied, by numerical analysis and pressure measurement, in the case of moist air expanding in a supersonic nozzle. The effects of the degree of supersaturation at the stagnation condition and expansion rate of the nozzle on the total pressure loss have been studied. The length of the region where the total pressure decreases during the condensation process is longer than that of the nonequilibrium condensation region, and of difference between the length of these two increases with the increase of the degree of supersaturation at the stagnation condition. Furthermore, the larger the expansion rate of the nozzle and the higher the temperature and the degree of supersaturation at the reservoir are, the larger the total pressure loss of the flow becomes. And, it is turned out that the total pressure loss be about 2 to 8 percent in the present study.

• Journal of the Korean housing association
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• v.16 no.4
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• pp.73-80
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• 2005

A high-rise residential building experienced stack effect problems during the winter such as difficulties in opening residential entrance doors and whistling noise from elevator doors generated by airflow. Field measurements were carried out on the building and the problems were verified by the analysis of the measurement results from three points of view: the total stack pressure difference, pressure distribution on each floor, and the location of the neutral pressure level. Based on the analysis of the three key parameters, possible solutions were proposed, such as zoning vertical shafts, lessening the airflow from the entrance doors on basement floors and lobby floor by installing vestibules, improving the airtightness of exterior walls, and installing separation doors where the problems occur. Simulations of proposed solutions were conducted and the effects of reducing the pressure difference were evaluated. Stack effect problems in a high-rise residential building were verified through field measurements and could be mitigated by the solutions which were drawn from the analysis of the field measurements and the simulation results.

• Transactions of the Korean hydrogen and new energy society
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• v.21 no.2
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• pp.129-135
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• 2010

Homogeneous charge compression ignition (HCCI) engines have the potential to provide both diesel-like efficiency and very low emissions of nitrogen oxide (NOx) and particulate matter(PM). However, several technical issues still must be resolved before HCCI can see application. Among these, steep pressure-rise rate which leads to narrow operating range of HCCI engine continues to be a major issue. This work investigates the combination of two methods to mitigate the excessive pressure-rise rates at high power output, namely fuel stratification and Cooled exhaust-gas recirculation (Cooled EGR), after identifying the each effects to pressure-rise rate. When applying the fuel stratification to simulation, total fuelling width of 0.15 at BDC is set as a equivalent ratio difference based on the previous research. In order to simulate the effects of cooled EGR, $CO_2$ mole fraction in pre-mixture is changed ranging from 0 to 30%. DME which has a characteristic of two-stage ignition is used as a fuel.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.10
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• pp.735-741
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• 2007

An axial F.R.P. fan model for cooling tower is developed. The fan is designed using the equations for one dimensional inviscid flow through the fan blade. Fan shape is swept forward with a parabolic function. Calculations of the three dimensional turbulent flow around the fan are carried out to investigate performance of the fan. Data of the total pressure rise and hydraulic efficiency can be obtained for the various setting angles. Calculated values of the total pressure rise and hydraulic efficiency at the design point are less than those of the design specification. The prototype of the F.R.P. fan is made by laminating of the fiberglass and epoxy resins on the mold of fan shape.

• Journal of the korean Society of Automotive Engineers
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• v.3 no.3
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• pp.39-48
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• 1981

The combustion phenomena of the stratified charged model combustion chamber under the initial conditions of the room temperature and the atmospheric pressure were investigated by using pressure record and high speed Schliern motion picture in comparison with that of the uniformly charged case. The results show that the total burning time is strongly dependent on the turbulent spouting flame jet speed which promotes the combustion process inside the chamber, and the pressure rise-up of stratified charged combustion is rather faster and higher than that of uniformly charged combustion, which can be resulted in the energy saving.

• International Journal of High-Rise Buildings
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• v.4 no.4
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• pp.271-281
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• 2015

This paper introduces detailed three-dimensional numerical analyses on a bored pile foundation for a high-rise building. A static load test was performed on a test pile and a numerical model of a single pile, which was calibrated by comparing it with the test result. The detailed numerical analysis was then conducted on the entire high-rise building foundation. Further study focused on soil pressures under the base slab of a piled raft foundation. Total seven cases with different pile numbers and raft-soil contact conditions were investigated. The design criteria of a foundation, especially settlement requirement were satisfied even for the cases with fewer piles under considerable soil pressure beneath the base slab. The bending moment for the structural design of the base slab was reduced by incorporating soil pressures beneath the base slab along with bored piles. Through the comparative studies, it was found that a more efficient design can be achieved by considering the soil pressure beneath the slab.