• 한국작물학회지
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• 제38권6호
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• pp.554-559
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• 1993

냉수관개가 벼 생육특성, 수량 및 미질관련 형질에 미치는 영향을 검토하기 위하여 작물시험장 춘천출장소 냉수처리포장에서 실시한 시험 결과를 요약하면 다음과 같다. 1. 냉수구에서는 자연구에 비하여 출수가 10～19일 지연되었고 간장과 수장은 17～31% 단축되었다. 수수는 일정한 경향이 없으며 품종간에 반응이 상리하였다. 2. 냉수구에서 영화수는 이삭당 10～35개가 감소되었고 등숙률이 현저히 떨어졌으며, 정조수량은 오대벼 치악벼등이 높은 수량을 나타낸 반면에 백암벼 소백벼 진미벼등은 낮은 수량을 보였다. 고중은 공시품종 모두 냉수구에서 높았다. 3. 현미 완전미율은 냉수구와 자연구간에 일정한 차이가 없었고 오히려 품종간의 변이가 크게 나타났고, 청미율은 자연구에서 많은 경향이며 연색미는 냉수구에서 월등히 높았다. 4. 백미 투명도및 알칼리 붕괴도는 수구쪽에서 높은 경향이며, 아밀로스 함량은 자연구에서 높았다.

• 한국농공학회지
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• 제12권4호
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• pp.2078-2083
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• 1970

The purpose of this study is to give the data neccesary for improving the planning of drainage structures, specially inverted siphons, in irrigation channels. With the samples of 15 drainage inlets, one drainage flume, 16 drainage inverted siphons and 6 drainage culverts in the 3 lines of irrigation channel under Chong-Won Irrigation Association, author abtained the following results. 1. It is presumed that design drainage discharge should be determined with some additional reserves, on the basis of the maximum rainfall intensity in local area and the size of drainage area on the topographical map, avoiding the way of eye measure. 2. Location of drainage inlet should be kept away from the place where topography can make lots of wash load, but when unavoidably allowing the inflow into irrigation channel, wash load outlet with even the purpose of drainage, or drainage flume in stead of drainage inlet should be taken account of. 3. It is presumed that drainage flume may be the structure which can perform its function from a structural point of view as far as topography permits. 4. Drainage inverted siphon should be avoided at any place as much as possible; a) In case that location of the siphon would be permitted only at paddy field, drainage area hauing the amount of discharge which requires more than 90cm in diameter could only be allowed. b) In this case, crest elevation of the tank of both inlet and outlet, at least, should not be lower than the surface level of paddy field. c) As far as topography and stratum permit, ratio of depth of outlet tank to head drop should be decreased as much as possible so that discharging efficiency of wash load could increase. d) In case of avoiding the setting of the siphon, irrigation aqueduct, irrigation inverted siphon, or drainage flume should be recommended in accordance with topography. 5. Discharging capability of wash load by drainage culvert appeared to depend hardly upon the diameter of the culvert, but greatly upon the location, specially near village, for there stones and dirts dumped may considerably be piled up. So, a counter plan for that is required.

• 대한토목학회논문집
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• 제37권6호
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• pp.989-999
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• 2017

본 연구에서는 분기수로에서 발생되는 에너지손실을 계산하기 위한 손실계수의 경험식을 산정하기 위해 수리모형실험을 수행했다. 수리모형은 유입수로와 90도의 각도를 갖는 두 유출수로로 구성되어 있으며, 유입수로과 유출수로에서 압력수두와 속도수두를 측정하여 분기수로에서 발생되는 에너지손실을 분석했다. 각 측선에서 동수경사선의 변화를 비교한 결과, 수로의 분기점에서 동수경사선이 급격히 하강하여 에너지손실이 분기점에서 발생되었으며, 유량비의 증가에 따라 속도수두의 감소폭이 증가했다. 유량비와 Froude수가 증가함에 따라 유출량이 더 큰 수로에서 수두손실량이 지수적으로 증가하는 결과를 보였으며, 손실계수 또한 증가했다. 반면에, 유출량이 작은 수로에서는 유량비와 Froude수의 증가에 따라 손실계수가 감소하는 결과가 나타났다. 손실계수 계산결과를 이용하여 두 유출수로에서 손실계수 경험식을 제안하였으며, 경험식의 계산오차가 각각 3.91%, 5.19%로 나타났다. 그리고 두 경험식을 이용하여 계산한 총 손실계수를 실험결과와 비교하여 3.62%의 오차가 발생했다.

• 한국항해항만학회지
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• 제37권6호
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• pp.637-645
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• 2013

마산만은 반폐쇄성 해역으로, 느린 유속과 육상오염물질의 하천부하 등으로 인해 심각한 수질문제를 가지고 있으며, 동시에 폭풍해일에 취약한 입지적 특성을 나타내고 있다. 이 중 폭풍해일 저감대책으로 제시된 재해방지시설을 운용함과 동시에 이를 마산만 내측 수질개선에 활용하는 방안을 모색하였다. 즉, 재해방지시설을 가동하여 마산만 내측과 외측의 수위조건이 다를 때 발생하는 수두차를 이용하여 만 내 외의 해수를 교환하였다. 재해방지시설의 위치를 기존 만 입구부, 마창대교 인근, 그리고 돝섬 인근으로 가정하였으며, 선박운항 횟수와 연간조위를 분석하여 통항빈도가 가장 낮은 새벽시간(01~05) 및 수두차가 가장 큰 대조기에 운용된다고 가정하였다. 또한, 재해방지시설과 함께 약 10km 길이의 유출 입 관로를 통한 내 외해수의 해수교환 촉진을 위한 추가 실험안을 구성하였다. 수치모의 결과, 현재상태의 경우 마산만 전체 해수교환율은 38.62%을 나타냈으며, 모든 실험안에서 마산만 내 모든 구역에서 꾸준한 증가 추세를 보이고 있다. 이에 반해, 마산만 입구부와 비교한 마산만 내측의 해수교환율은 매우 낮게 나타나 반폐쇄성 내만해역의 특성을 잘 재현하는 것으로 판단된다. 재해방지시설과 관로를 이용한 실험안을 분석한 결과, 현재상태와 비교하여 재해방지시설을 운용한 경우 해수교환율이 높고, 그 운용빈도가 많아질수록 더 많은 순환이 이루어지는 것으로 나타났다. 또한, 재해방지시설에 의해 발생된 수두차를 이용하여 관로를 통해 해수를 유입 혹은 유출한 경우 마산만 가장 내측의 수질이 개선되는 것으로 나타났다. 재해방지시설의 위치는 마창대교 남측과 비교하여 마산만 입구와 돝섬에 위치한 경우 해수교환 효과가 더 좋게 나타났다. 한편 마산만 전체영역에 대한 해수교환율은 만 입구에 재해방지시설이 위치한 경우가 돝섬에 위치한 경우보다 높지만, 마산만 내측을 포함한 해수교환율은 반대로 돝섬에 위치한 경우가 더 높게 나타났다.

• International Journal of Fluid Machinery and Systems
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• 제9권2호
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• pp.107-118
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• 2016

This paper focuses on the single stage and multistage performance characteristics of centrifugal mixed flow submersible borewell pump. This study reveals that the performance of single stage pump is higher than that of multistage pumps. The head, input power and efficiency of single stage pump are higher than the per stage head, per stage input power and efficiency of multistage pumps. This study is divided into three parts. In the first part, five prototype pumps were made in single stage and multistage construction and the performance tests were conducted. In the second part, numerical validation has been done for different turbulence models and grid sizes. k-Omega SST model has been selected for the performance simulation and was validated with the performance of the test pump with static pressure tappings. In the third part, single and three stage pump performance were simulated numerically and compared with experimental results. The detailed analysis of pressure and velocity distributions reveals the difference in performance of single and three stage pump, due to non-uniform flow and difference in averaged flow velocities at the subsequent impeller inlets except the 1st stage impeller inlet.

• 한국자동차공학회논문집
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• 제24권2호
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• pp.232-241
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• 2016

The turbocharger, to decrease the harmful exhaust gas(CO, HC and etc.) and $CO_2$ emission as well as the increase of the engine output, would be an useful method for engine downsizing. Therefore the thermal endurance of turbine blade, the lubrication of turbine shaft and the engine knock according to the supercharge of the inlet air, had been studied. And there had been much progress in these research tasks to be achieved a breakthrough. But a study on the built-in WGV of a gasoline engine for a passenger car which may effect on the engine performance, is few. In this paper, the effect of the embedded WGV on the engine performance was performed through the endurance test, which was conducted more than 300 hrs using the 4 stroke, 1998 cc, water-cooled engine. To sum up the major results, there were an abrasion in the area of the WGV head edge and the thermal deformation on the WGV head face, These phenomena led to reducing the boost pressure which caused the reduction in the volumetric efficiency of the engine. It resulted in decreasing the engine power gradually during the life cycle of the embedded WGV.

• 전기학회논문지
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• 제63권8호
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• pp.1134-1139
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• 2014

Recently the need for renewable energy development is expanding due to the global climate change, the environmental issues and the limited fossil energy resources. Dependence of energy on overseas is high in Korea. To resolve the environmental problems and to improve the energy independence rate, the development of renewable energy is more required. The small hydro power, one of the renewable energy resources, has been developing and operating from a long time ago. If we are new developing a small hydro power with the use existing dams and reservoirs, we will design the length of inlet pipe and the diameter suitable for it. However, in case of using the existing water supply pipe which had been designed suitable for water service, the designer has to review and check that the pipe is suitable for operating a generator. In this paper, the design of small hydro power using the existing long pipe of water supply, we suggest the optimum way to reduce the water hammer in pipe which causes the unsteady flow during the load-shutdown of generator, the generator operation plan for the stable supply of water and the design factor of determining the generator capacity through the analysis between discharge and head-loss.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2009년도 제33회 추계학술대회논문집
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• pp.78-81
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• 2009

연료펌프에 대한 수력성능시험을 상온의 물을 매질로 하여 실시하였다. 시험된 연료펌프는 개방형 가스발생기 방식의 75톤급 액체로켓엔진에 적용할 목적으로 개발 중에 있다. 시험 결과, 연료펌프는 설계요구조건을 만족하였으며, 설계 유량에서의 양정과 효율은 수치해석에서 추정된 값보다 높았다. 또한 후방 베어링의 출구 압력이 예상보다 높았는데 이는 바이패스 배관의 입구가 좁기 때문이었다. 그리고 바이패스 곡관부의 차압 측정으로 누설 유량을 유추할 수 있었다.

• 한국유체기계학회 논문집
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• 제8권1호
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• pp.23-29
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• 2005

Steady and unsteady cavitation characteristics of turbopump inducer were investigated in this paper. To investigate the effect of blade angle on the inducer performance, three inducers with inlet tip blade angle of $7.8^{\circ},\;7.0^{\circ},\;6.1^{\circ}$, respectively, were tested. For $7.8^{\circ},\;7.0^{\circ}$ inducers in the non-cavitating condition, head decreased linearly with flow rate, but head-flow rate curve had a dip at the flow coefficient ${\psi}=0.065$ for $6.1^{\circ}$ inducer. Attached cavitation and cavitation surge were found in the $7.8^{\circ},\;7.0^{\circ}$ inducers in the cavitation tests. During the attached cavitation one cell rotated at the same rotational speed as that of the inducer. The cavitation surge did not rotate and the oscillating frequency was $7{\sim}20\;Hz$. From the curve of the critical cavitation number versus flow rate, it was found that the steady cavitation performance of $6.1^{\circ}$ inducer was much lower than that of $7.8^{\circ},\;7.0^{\circ}$ inducers.

• 신재생에너지
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• 제10권4호
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• pp.9-15
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• 2014

In this study pressure and shaft torque pulsation were measured with variation of head and flow during the model test for a 15 MW Francis Turbine. Pressure pulsations were measured at the inlet of the spiral casing and 4 points in the cone of the diffuser and shaft torque pulsation at the upper position of the turbine. The maximum amplitude of pressure pulsation appeared 2.03% of the maximum rated head with the frequency of 25% of the rated revolution and at the guide vane opening of $10^{\circ}$. Shaft torque pulsation appeared 0.01% of the rated shaft torque, fairly low value. Air was admitted through the cone and pressure pulsation gradually decreased with increase of air flow and kept nearly constant after 5% of the rated flow. A new Francis turbine of which specific speed is 115 m-kW had been designed to rehabilitate the old one and the model test was performed at EPFL. The commercial code, STAR-$CCM^+$ was used for numerical simulation of flow.