• Journal of the Korea Organic Resources Recycling Association
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• v.25 no.2
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• pp.27-31
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• 2017

This study was performed to estimate bubble dissolution rate by change of hydraulic pressure according to increase of water depth. Experimental results showed that airflow rate was decreased by increase of hydraulic pressure. Because the force which acts on outlet of nozzle was increased by increase of hydraulic pressure. Mass-transfer coefficient decreased with decreasing airflow rate and increasing effective volume due to increase of hydraulic pressure as water depth increased. On the contrary, as the water depth increased, the bubble dissolution rate was increased because longer residence time of microbubble which was generated by ejector type microbubble generator. However it was thought that if water depth for capacity of ejector type microbubble generator is excessively increasing, bubble dissolution rate would be reduced due to low airflow rate and mass-transfer coefficient. Therefore, it is importance to consider the water depth when operating ejector type microbubble generator.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.9
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• pp.495-504
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• 2017

An amphibious scrubbing/suction dredging machine with cylindrical rotating brush, housing, and turbidity barrier was newly-developed to remove both sediments with about 10 cm thickness and periphyton attached on various structures in urban water-circulating systems through the scrubbing, suction, and dredging processes. Based on the field application and long-term monitoring, the increase in both suspended solids (SS) and turbidity of water during the scrubbing, suction, and dredging processes was negligible (p>0.05). In some cases, the turbidity of water initially increased, however, the turbidity was stabilized within 20 minutes from the start of dredging processes. The concentration changes in TN and TP of water were not statistically different (p>0.05) before and after the scrubbing, suction, and dredging processes, indicating that benthic nutrients released from sediments were not significantly diffused, and were not supposed to cause significant water pollution. Also, water treatment facilities along with an amphibious scrubbing/suction dredging machine could be more effective since the removal of contaminant loadings through the scrubbing, suction, and dredging processes was much greater than that through simple coagulation/precipitation processes. Finally, GPS-based realtime tracking and operation program have been developed and applied in various urban water-circulating systems, and development of driver cooperative autonomous driving system is in progress to eliminate the need for manual driving of an amphibious scrubbing/suction dredging machine.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.6
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• pp.833-839
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• 2010

Over the past years, many research works have been carried out to investigate the factors which govern the performance of diesel engine. The air pollutant emission from the diesel engine is still a significant environmental concern in many countries. In the present study, new system of smoke reduction of diesel engine is proposed. This new system is using vacuum equipment for capture smoke. To confirm new system experiments were performed at engine dynamometer. As a result of this experiment, the smoke reduction of this system was identified.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.2
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• pp.31-37
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• 2017

This paper investigates the effect of the rotational motion of a driving fluid generated by a rotational motion device at the inlet of a driving nozzle for a gas-liquid ejector, which is the main device used for ozonated ship ballast water treatment. An experimental apparatus was constructed to study the pressure and suction flow rate of each port of the ejector according to the back pressure. Experimental data were acquired for the ejector without rotational motion. Based on the data, a finite element model was then developed. The rotational motion of the driving fluid could improve the suction efficiency of the ejector based on the CFD model. Based on the CFD results, structure optimization was performed for the internal shape of the rotation induction device to increase the suction flow rate of the ejector, which was performed using the kriging technique and a metamodel. The optimized rotation induction device improved the ejector efficiency by about 3% compared to an ejector without rotational motion of the driving fluid.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.92-92
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• 2017

밭작물 중 마늘 재배를 위한 노동력 투입시간은 2016년 기준 10a 당 126.9시간 이었고, 파종정식의 기계화율은 2015년 기준 15.1%로 조사된다. 이는 마늘 재배에 있어서 파종정식의 기계화가 노동력 절감을 위해 필요하다는 것을 보여준다. 현재의 우리나라 마늘 파종기는 점파식으로 개발, 판매되고 있는데 집개 방식 또는 버킷 방식은 파종 속도를 올리면 파종율이 떨어지기 때문에 파종 속도를 향상시키는데 한계가 있있다. 본 연구에서는 이를 보완하기 위하여 콩, 옥수수 등의 종자에 사용되는 진공식 파종 기술을 마늘에 적용하였다. 마늘의 경우 형상이 비대칭형에다가 종구별 크기, 모양, 무게가 조금씩 다르기 때문에 이론적으로 흡입구를 설계하는 어려움이 있다. 따라서 진공흡입구의 지름과 재질을 파라메터로 하여 변화를 주고 실험을 통하여 배종률 결과의 차이를 확인하였다. 그 결과 경도 $10{\pm}2$의 실리콘 재질에 지름 14mm이상에서 90%이상의 높은 배종률을 보여주었다.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05b
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• pp.277-283
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• 1996

원자력 발전소의 일차계통 부분충수운전시 잔열제거 계통 입구에서 자유수면 와동으로 인해 계통에 공기가 흡입될 수 있으며 이로 인해 계통이 상실되거나 계기에 오차가 유발되어 많은 안전상의 문제를 야기할 수 있다. 이러한 문제들을 해결할 수 있도록 흡입구의 구조를 개선하기 위해 다양한 구조에 대해 실험을 수행한 결과 깔때기 모양과 우회유로를 설치한 경우. 그리고 기존 T자형에 와동 방지판을 부착하는 것이 매우 효과적임이 밝혀졌다. 하지만 깔때기 모양이나 우회유로의 경우는 배관구조의 변경이 필요하여 따라서 기존 발전소나 신설 발전소에 적용시 문제점이 많으므로 필요시 붙이고 불필요하면 제거가능한 탈착식인 다공 와동 방지판을 최종적으로 선정하였다. 이 경우에 대하여 1/4 축소 실험장치로 실험한 결과 운전유량 영역에서 와동의 발생으로 인한 공기흡입과 펌프의 정지를 획기적으로 줄여주는 것으로 밝혀졌다.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.3 no.1
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• pp.42-46
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• 1974

• The Journal of Engineering Geology
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• v.25 no.3
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• pp.377-385
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• 2015

We constructed a model test apparatus to evaluate the dependence of the saturation velocity (V_s) in soils on rainfall intensity (I_R). The apparatus comprises a soil box, a rainfall simulator, and measuring sensors. The model grounds (60 cm × 50 cm × 15 cm) were formed by Joomunjin standard sand with a relative density of 75%. The rainfall simulator can control the rainfall intensity to reenact the actual rainfall in a soil box. Time Domain Reflectometer (TDR) sensors and tensiometers were installed in the soils to measure changes in the volumetric water content and matric suction due to rainfall infiltration. During the tests, the soil saturation was determined by raising the groundwater table, which was formed at the bottom of the soil box. [Please check that the correct meaning has been maintained.] The wetting front did not form at the ground surface during rainfall because the soil particles were uniform and the coefficient of permeability was relatively high. Our results show that the suction stress of the soils decreased with increasing volumetric water content, and this effect was most pronounced for volumetric water contents of 20%-30%. Based on a regression analysis of the relationship between rainfall intensity and the average saturation velocity, we suggest the following equation for estimating the saturation velocity in soils: V_savg (cm/sec) = 0.068I_R (mm/hr).

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.9
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• pp.1021-1026
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• 2014

In this paper, among various systems applying hot-gas bypass control, outdoor temperature, outlet temperature of water cooler, superheating and subcooling degree, which are the factors affecting the performance of the system bypassing hot-gas to evaporator inlet were analyzed. The main results were summarized as following. Frist of all, performance of refrigeration system bypassing hot-gas to evaporator inlet was affected by outdoor temperature, outlet temperature of water cooler, superheating and sub cooling degree. Thus, providing basic planning date of refrigeration system obtained through optimization of variables is expectable. Thus, providing the basic design data of refrigeration system can be offered by performing the optimization of these variables. Also, the feasibility of this refrigeration system proposed in this paper was obtained by analyzing operating characteristics of the system bypassing hot-gas to evaporator inlet.

• Journal of the Korean Society of Propulsion Engineers
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• v.26 no.1
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• pp.77-87
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• 2022

In order to perform the scramejt engine intake ground test using the Scramjet Engine Test Facility(SETF) of the Korea Aerospace Research Institute. we introduced the test availability check procedure that is generally conducted. The design process of the newly manufactured Mach 5 nozzle for the scramjet intake test was summarized, a device for checking the core flow distribution of the nozzle was explained, and the core flow test analysis results were written. Through a series of test results, it was confirmed that the intake was located in the new Mach 5 nozzle core.