• Journal of Biosystems Engineering
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• v.24 no.4
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• pp.309-316
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• 1999

This study was conducted to develop a large-scale rice polisher with double polishing stages for producing clean rice with high quality in rice processing complexs. The performance of the developed rice polisher was evaluated and improved. The results obtained from this study were as followings : 1. A large-scale rice polisher with double polishing stages was developed, which consisted of two polishing chambers(polishing part I and II), two spraying parts, a feeding part, power of 37kW, control panel, etc. Especially, the purpose of polishing part Iwere to uniformly mix white rice sprayed with water and to remove bran particles from the rice. the roller surface of the polishing part I was coated with chromium. 2. The capacity of the developed rice polisher was 4t/h. The broken rice rate of the polisher was less than 0.2%, compared with about 1% of others. 3. The whiteness increment of the developed polisher was 2.6~3.0% compared with about 2.3~2.5% of others. 4. The energy consumption of the developed polisher was 0.5kWh/100kg. 5. The developed polisher was improved with the angle change of screen slot of the polishing chamber I. The broken rice rate was reduced from about 0.5% to about 0.2% as the max. internal pressure of the polishing chamber II decreased by 0.4kg/$\textrm{cm}^2$ due to the increase of resistance in the polishing chamber I. The whiteness of the polisher showed more than 38~39. 6. The developed rice polisher showed high performance, compared with other domestic and foreign polishers.

• 한국전산유체공학회:학술대회논문집
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• 2009.04a
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• pp.335-340
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• 2009

Operating medium or large scale industrial boilers in partial load condition, the burner should undergo the off-design points resulting in poor exhaust gas characteristics. To obtain the stable turn down performance, two or more burners can be used for the industrial boiler. In case multiple burners are adopted, the heat transfer can be enhanced by arranging the burners properly. In the present study, numerical simulations have been conducted for the combustion chamber of a 2 t/h class industrial boiler in order to clarify the heat transfer characteristics at the combustion chamber.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.1
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• pp.88-93
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• 2000

In this study, the mixing process of two-phase flow generated by two jets with height difference is analyzed. The primary jet is jetted on the condition of the state mixed pulverized solid particles with air. The height difference between the main jet and the secondary jet is changed into three kinds(0, 32.5, 47.5mm). The velocity vector field, concentration field and turbulent properties of solid particles are measured by using 3-Dimensional Particles Dynamics Analyzer. As the height difference of two jets through the two nozzles increases, the solid particle recirculation zone and the dense zone in the combustion chamber become large. The solid particle concentration at the center of the combustion chamber gets dense because the particle velocity remains slow due to the existence of the solid particle recirculation zone. The particle concentration in the combustion chamber can also be influenced by the hight difference of two jets.

• Journal of Chest Surgery
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• v.18 no.1
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• pp.13-18
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• 1985

Cortriatriatum is rare congenital heart disease characterized by the presence of a fibromuscular diaphragm that subdivides the left atrium into a proximal or "accessory" and a distal or "true" left atrial chamber. A 15 year old girl with cortriatriatum underwent surgical correction at the department of Thoracic and Cardiovascular Surgery, Soonchunhyang College in November, 1984. This case was preoperatively diagnosed as a single atrium with functional tricuspid regurgitation But on operation, we found that there were transverse septum in the left atrium through large ASD, low chamber receives the pulmonary veins, and the upper chamber gives rise to the left atrial appendage and leads to the mitral valve. And the anomalous membrane has no fenestrations. We excised completely the anomalous septum, reconstructed atrial septal defect with dacron patch and performed the tricuspid annuloplasty with DeVega method. Postoperative course was uneventful during follow up, during follow up.

• Journal of the Korean Society of Combustion
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• v.17 no.2
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• pp.1-8
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• 2012

Laminar flame speeds of Methane at elevated temperatures and pressures were investigated using constant volume spherical chamber. Pressure trace during combustion was measured in each test and this was used in calculating laminar flame speed of Methane. To have large amount of data, experimental apparatus was fabricated with fully automatically controlled feature. A calculating code which calculates laminar flame speeds at various temperatures and pressures with one experimental result was used to calculate laminar flame speeds. The experimental and calculating methods were verified using the calculated laminar flame speed result with PREMIX code.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.7
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• pp.54-65
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• 1999

In this study, the flow field, spray structure, and combustion process were investigated in a direct injection diesel engine having an offset bowl in a combustion chamber. The KIVA-3V code was used in this study. In order to obtain accurate results, a droplet atomization model, wall impingement model, and ignition delay concept were added to KIVA-3V code. The results showed that the offset bowl engine had a large vortex flow. The direction of this flow counteracted to the direction of fuel injection in one side of combustion chamber. It decreased local turbulent kinetic energy and eventually nonuniform combustion was resulted in an offset bowl engine. In comparison with a center bowl engine case, the peak cylinder pressure was decreased about 6%. Finally , the effect of swirl on combustion was investigated in an offset bowl engine . As the became stronger, the nouniform characteristics in combustion were increased.

• Journal of computational fluids engineering
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• v.14 no.2
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• pp.77-83
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• 2009

Operating medium or large scale industrial boilers in partial load condition, the burner should undergo the off-design points resulting in poor exhaust gas characteristics. To obtain the stable turn down performance, two or more burners can be used for the industrial boiler. In case multiple burners are adopted, the heat transfer can be enhanced by arranging the burners properly. In the present study, numerical simulations have been conducted for the combustion chamber of a 2 t/h class industrial boiler in order to clarify the heat transfer characteristics at the combustion chamber.

• Journal of Mechanical Science and Technology
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• v.20 no.6
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• pp.896-904
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• 2006

In a liquid rocket engine, the role of gas-liquid scheme injector as an acoustic resonator or absorber is studied experimentally for combustion stability by adopting linear acoustic test. The acoustic-pressure signals or responses from the chamber are monitored by acoustic amplitude. Acoustic behavior in a rocket combustor with a single injector is investigated and the acoustic-damping effect of the injector is evaluated for cold condition by the quantitative parameter of damping factor as a function of injector length. From the experimental data, it is found that the injector can play a significant role in acoustic damping when it is tuned finely. The optimum tuning-length of the injector to maximize the damping capacity is near half of a full wavelength of the first longitudinal overtone mode traveling in the injector with the acoustic frequency intended for damping in the chamber. When the injector has large diameter, the phenomenon of the mode split is observed near the optimum injector length and thereby, the acoustic-damping effect of the tuned injectors can be degraded.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.10a
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• pp.815-824
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• 2013

Pneumatic exciters can be good replacements of electrodynamic, piezoelectric and hydraulic exciters owing to simple structure and large exciting force. One problem to be solved is a slow response caused by compressibility of air. Desirable frequency response characteristics of exciter are constant magnitude and zero degree phase, because users want no time delay between input signal and output force. For this reason, frequency range of pneumatic exciters is limited about 0~1 Hz. Therefore, expansion of frequency range is an important issue when designing the pneumatic exciter. In this paper, the pneumatic exciter which has same structure with active pneumatic isolator is dealt with. The dynamic characteristics are presented, and its limitation of expanding frequency range is shown based on analytical studies. Then the pneumatic exciter with dual-chamber is suggested to overcome this problem. Based on simulation study, a design method is presented.

• Geomechanics and Engineering
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• v.21 no.3
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• pp.237-245
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• 2020

The process of evaporation from free water surface was simulated in a large scale environmental chamber under various controlled atmospheric conditions and also was modelled by a new mass transfer model. Six evaporation tests were conducted with increasing wind speed and air temperature in the environmental chamber, and hence the effect of atmosphere parameters on the evaporation process and the corresponding response of water were investigated. Furthermore, based on the experiment results, seven general types of mass transfer models were evaluated firstly, and then a new model consisted of wind speed function and air relative humidity function was proposed and validated. The results show that the free water evaporation is mainly affected by the atmospheric parameters and the evaporation rate increases with the increasing air temperature and wind speed. Both the air and soil temperatures are affected by the energy transformation during water evaporation. The new model can satisfactorily describe the evaporation process from free water surface under different atmospheric conditions.