• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 2011.06a
• /
• pp.399-401
• /
• 2011

반잠수식 시추선의 주선체(lower hull)를 세 가지 타입으로 설계하여 주선체에 대한 유체정역학적 계산, 조종성능 및 내항성능 계산 그리고 이론계산을 수행하여 wave distribution과 height도 각각 비교 분석하였다. 주선체의 Convention type, Bulbous bow type, 그리고 Ice breaking type 중 Ice breaking type 선형의 성능이 가장 우수하였다. 다음으로는 반잠수식 시추선의 모든 조건(작업, 이동, 생존)에서 주기둥(column) 또는 주선체(Lower)가 손상되어 부력을 상실했을 시 전복 되지 않도록 고안된 예비부력 기능과 기름 유출 사고시 기름을 회수 할 수 있는 기능을 갖춘 유회수 겸용 예비부력 탱크를 개발하였다.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.28 no.2
• /
• pp.73-80
• /
• 2016

To reduce the mechanical energy loss and to get the high energy efficiency, an apparatus of wave power generation inducing a consistent one way rotating motion from the wave reciprocation motions was developed and the hydraulic experiments for the real electric power production were conducted and the results were discussed. In the experiments for the shape of the buoyant tank, the efficiency of the fixed 9 cm diameter type enduring the wave plate weight was 14.6% and this was the best result for all shapes. But although the free sliding type was expected to represent a high efficiency, the experiments did not show a good result as 8.5% efficiency. Therefore, the shape of buoyant tank was decided as the fixed 9 cm diameter type in the next all tests. In the experiments for the various incident waves, when the water depth was 90 cm, the average efficiencies were measured as 3.9% in the 2nd gear, 4.9% in the 3rd gear, 4.9% in the 4th gear, 12.0% in the 5th gear, 10.0% in the 6th gear, 3.1% in the 7th gear, and 3.0% in the 8th gear. Also, when the water depth was 80 cm, the average efficiency was shown as 15.0% with 5th gear condition. Therefore the high average efficiency as 13.5% was given with 80~90 cm water depth and the 5th gear in the model.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.20 no.1
• /
• pp.76-81
• /
• 2016

At negative-g condition, a float-type valve can open the passage of fuel in order to it flows continuously through a pressurized fuel tank system. Since specialized test conditions and high-cost supports are required, it is truly difficult to test the valve in a real high-speed test. Therefore, this paper contains performance analysis of a float-type fuel supply valve through flight tests conducting roll and negative-g maneuvers.

• Proceedings of the Korean Society for Agricultural Machinery Conference
• /
• 2017.04a
• /
• pp.148-148
• /
• 2017

방역 차량의 약액탱크, 차량의 연료, 워셔액 등의 탱크 내부에는 잔존량을 측정하기 위해 기둥과 floating box로 이루어진 부력식 수위레벨센서가 사용되고 있으나 액체레벨에 따라 float이 상하로 움직이는 측정원리상 차량 주행 중 정확성이 매우 떨어진다(Park et al. 2016). 방역차량이 주행 중 분사할 때, 슬로싱 현상과 방역소독기의 노즐과 펌프에서 발생하는 진동으로 인해 기존의 부력식 센서를 이용한 약제 살포량 측정방법은 정확성이 매우 떨어지는 경향이 있다. 본 연구의 목적은 방역차량이 주행하면서 분사할 때, 수위레벨 센서를 이용한 약제살포량 측정의 정확성을 개선하는 것으로 디지털 칼만필터, Low pass filter와 댐퍼를 제작하여 이용했다. 본 연구에서는 압력식 레벨센서를 이용해 약액탱크의 높이당 단면적과 수위를 측정하여 약제살포량을 계산했다. Python 2.7을 이용해 디지털 칼만필터와 Low pass filter(LPF)를 구현하였으며 3D프린터를 이용해 댐퍼를 제작했다. 실내에서 슬로싱 현상을 인공적으로 만들어 필터와 댐퍼의 수위 측정 정확성 개선효과를 확인 후 실제 방역차량에 부착하여 비포장도로에서 주행하면서 분사할 때 필터와 댐퍼의 효과를 확인하였다. 댐퍼의 공극률(p)을 바꿔가며 수위 측정 정확성 개선효과를 확인하였다. 실내, 현장 실험 결과, 칼만필터가 LPF보다 개선효과가 더 크지만 데이터 50개 처리에 1.71초의 시간지연이 발생했다. 댐퍼는 수위센서를 고정시키고 유체의 운동을 방해하여 이상치와 큰 오차제거에 효과적이었다. 칼만필터와 댐퍼를 동시에 이용할 경우, 수위 측정정확성 $R^2$는 0.9985, 0.9981로 ${\pm}4.3cm$의 범위내에서 수위를 측정할 수 있었다. 필터의 시간지연과 수위 측정정확성을 고려하여 데이터 기록간격을 3초로 설정하면 ${\pm}3cm$이내에서 약탱크 내 수위를 측정할 수 있었다. 공극률(p)가 0.294, 0.291, 0.17에서 측정정확성 $R^2$는 각각 0.9897, 0.9858, 0.9872 로 p가 0.294에서 개선효과가 가장 좋았으나 개선효과의 차이는 크지 않았다.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.9 no.3
• /
• pp.25-37
• /
• 2005

For pump-fed rocket propulsion system, the temperature of LOX to be supplied to turbopump inlet should be satisfied with pump inlet temperature requirement during all operating stages, as excessive temperatures can result in cavitation due to reduction in NPSH, thus either damaging the pump or adversely affecting pump performance rise. So exact estimation of LOX temperature rise is absolutely needed for developing reliable propulsion system. This paper presents systematic analysis scheme for estimating inner process of cryogenic propellant tank which is needed for LOX temperature rise. And this paper presents LOX temperature rise and thermal stratification for all rocket operating stages including cooling, filling, waiting, pre-pressurization and firing, with the application of buoyancy driven boundary layer theory.

• Journal of Energy Engineering
• /
• v.23 no.4
• /
• pp.95-105
• /
• 2014

The CUPID code has been developed for a transient, three-dimensional, two-phase flow analysis at a component scale. It has been validated against a wide range of two-phase flow experiments. Especially, to assess its applicability to single- and two-phase flow analyses in the Calandria vessel of a CANDU nuclear reactor, it was validated using the experimental data of the 1/4-scaled facility of a Calandria vessel at the STERN laboratory. In this study, a preliminary thermal-hydraulic analysis of the CANDU reactor moderator tank using the CUPID code is carried out, which is based on the results of the previous studies. The complicated internal structure of the Calandria vessel and the inlet nozzle was modeled in a simplified manner by using a porous media approach. One of the most important factors in the analysis was found to be the modeling of the tank inlet nozzle. A calculation with a simple inlet nozzle modeling resulted in thermal stratification by buoyance, leading to a boiling from the top of the Calandria tank. This is not realistic at all and may occur due to the lack of inlet flow momentum. To improve this, a new nozzle modeling was used, which can preserve both mass flow and momentum flow at the inlet nozzle. This resulted in a realistic temperature distribution in the tank. In conclusion, it was shown that the CUPID code is applicable to thermal-hydraulic analysis of the CANDU reactor moderator tank using the cost-effective porous media approach and that the inlet nozzle modeling is very important for the flow analysis in the tank.

• Journal of Korea Water Resources Association
• /
• v.32 no.1
• /
• pp.83-94
• /
• 1999

In continental margins, turbid underflows which are not confined to a given channel, are free to spread laterally as well as longitudinally. Lateral spreading can reduce substantially the run out distance of flows along continental shelves and slopes. Laboratory experiments with a large tank, employing saline density currents as surrogates for fine-grained turbidity flow, coupled with dimensional analysis, have been used to develop a simple expression for lateral spreading rates of two-dimensional flows on sloping beds. characteristic length and time are determined by the flow discharge and buoyancy flux at the inlet. By knowing the initial width of the flow, the spreading law can be used to estimate the maximum width of the current at different times as well as the longitudinal spreading rate. Predictions for flows compare favorably against observations.

• Journal of Ocean Engineering and Technology
• /
• v.22 no.4
• /
• pp.78-83
• /
• 2008

In recent years, small boats used for marine leisure have been steadily increasing because of the increase in national income and the desire for marine leisure. But the repair of such small boats in dry dock has pointed out many faults in small FRP-shipbuilding in terms if workspace and manpower. Lifting a boat from the water to land is done with a crane or by hand using a sling around the bottom of the boat. But dry dock work is limited by the scale of the boat, which corresponds to the crane capacity, with carelessness making it possible to capsize a boat and endanger life. The purpose of this study was the development of a marine docking system that would improve economical efficiency and safety, for which we carried out concept design, model tests, structural analysis, etc.

• Applied Chemistry for Engineering
• /
• v.17 no.4
• /
• pp.361-368
• /
• 2006

The purpose of this study is to invent the preparation technique of the foam-floater used as a level gauge of liquefied petroleum gas (LPG) tank under high pressure, which has not only closed pores but also has under 5 wt% changingrate in case of depositing 72 h in room-temperature LPG. In pressure-resistance and deposition experiment, the prepared foam-floaters with different sulfur (325 Mesh and 400 Mesh) and foaming agent (dinitrosopentamethylenetetramin; DPT and azodicarbonamide; AC) had a marginal difference in its weight changing-rate. However, the prepared floater with sulfur 400 Mesh and the foaming agent AC had smaller pores and higher closed pore-rate. Under $50kg_f/cm^3$ hydraulic pressure, the floater with medium thermal (MT) carbon showed a lower weight changing-rate than semi reinforcing furnace (SRF) carbon. Providing a post-treatment to the prepared floater, the hardness and the pressure-resistance of the inner pore-wall of floater were increased. Prepared floaters having a specific gravity below 0.30 were distorted and broken, and other floaters with a specific gravity above 0.35 were not useful as a floater because of the low buoyancy. Therefore, it was considered that the floaters with a specific gravity between 0.3~0.35 are the most useful as a floater under $50kg_f/cm^3$ pressure-resistance.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• v.1
• /
• pp.419-424
• /
• 2006

In recent years, the repairing work of the small boats in dock have pointed out a defects of the many FRP shipbuiling because of a term of works and working-space and man-power. In the paper, By carried out the model tests and structure analysis of the floating dock were mainly drawing on the concept design of the floating dock systems that the above defects were solved.