• 농업과학연구
• /
• 제36권1호
• /
• pp.87-98
• /
• 2009

대전 3대 하천의 하나인 갑천의 유등천 합류전 지점의 하천유지유량 확보를 위해 상류 유역에 금곡지와 괴곡지를 각각 설치하는 경우 각각 장안지, 방동지의 기존 저수지를 포함하여 직렬, 병렬 연계 운영을 반영하여 목표 지점의 유량을 1966년부터 2007년까지 모의하여 효과를 분석한 결과 다음과 같다. 첫째, 방동지-금곡지 직렬 연계에 의해 금곡지로부터 용수공급능력을 분석한 결과 연평균하여 하천유지유량 공급량은 6.83백만 $m^3$, 용수공급량/유역면적은 403.4 mm, 단위유역 용수공급량/강우량 비율은 33.0 %, 용수공급량/유입량 비율은 96.4 %, 용수공급량/저수량 비율은 81.9 %, 유입량/저수량 비율은 112.3 %였다. 둘째, 장안지-금곡지 병렬 연계를 고려한 갑천지점의 유량을 분석한 결과 유황은 연평균하여 풍수량 $4.806m^3/s$, 평수량 $2.217m^3/s$, 저수량 $1.140m^3/s$, 갈수량 $0.887m^3/s$로 분석되었으며, 평균갈수량은 목표유량 $1.486m^3/s$보다 $0.599m^3/s$ 적게 나타났다. 셋째, 장안지-방동지 병렬 연계에 의해 괴곡지 유입량을 모의하였고, 괴곡지로부터 용수공급능력을 분석한 결과 연평균하여 하천유지유량 공급량은 49.60백만 $m^3$, 용수공급량/유역면적은 246.5 mm, 단위유역 용수공급량/강우량 비율은 19.4 %, 용수공급량/유입량 비율은 40.8 %, 용수공급량/저수량 비율은 412.1 %, 유입량/저수량 비율은 1,189.8 %였다. 넷째, 괴곡지 방류를 고려한 갑천 지점의 유량을 분석한 결과 유황은 연평균하여 풍수량 $4.501m^3/s$, 평수량 $2.277m^3/s$, 저수량 $1.743m^3/s$, 갈수량 $1.564m^3/s$로 분석되었으며, 평균갈수량은 목표유량 $1.486m^3/s$보다 $0.078m^3/s$ 높게 나타났다. 요약하면 괴곡지를 설치하는 것이 금곡지를 설치하는 것보다 갑천 지점의 하천유지유량을 확보하는데 효율성이 높은 것으로 분석되었다.

• Journal of Advanced Marine Engineering and Technology
• /
• 제24권3호
• /
• pp.79-87
• /
• 2000

This paper describes experimental investigations of helium-air exchange flow through openings with vertical partitions. Such exchange flows may occur following rupture accident of stand pipe in high temperature gas cooled reactor. Exchange flow rates are investigated experimentally by using partitioned opening and opening with extended partition to assess fluids interference of the exchange flow at the stand pipe rupture accident. A tests vessel with the two types of opening on top of test cylinder is used in the experiments. An estimation method of mass increment is developed and applied to measure the exchange flow rate. A technique of flow visualization by Mach-Zehnder interferometer is provided to recognize the exchange flows. Amplitude and progress of interference fringes of the flows are observed and used as a support in comparison with the exchange flow rates. Flow passages of upward flow of the helium and downward flow of the air for both two types of the opening are separated by inserted partition within the opening, but in the case of partitioned opening, unseparated flow is formed at the opening entrance and the two flows interface. The exchange flow rate for the partitioned opening is not greater than that of the opening with extended partition because of the fluids interference at the entrance of opening. Finally, the fluids interference at the opening entrance is found to be one of important factors on the helium-air exchange flow rate.

• 설비공학논문집
• /
• 제10권4호
• /
• pp.483-494
• /
• 1998

This study describes the characteristics on impeller discharge flow of a centrifugal compressor with vaneless diffuser. Distorted flow at impeller exit was investigated by measuring of unsteady velocity fluctuation using hot-wire anemometer. As a result, a wake region appears near shroud side and moves to suction side and also to hub side as flow rate decreases. Jet, wake, and their boundary region which can be defined in jet-wake flow model are clearly observed at a high flow rate for the flow coefficient of 0.64, however, as flow rate decreases to the flow coefficient of 0.19, the classification of their regions disappears. Turbulence intensity also increases as flow rate decreases. Measurement error from uncertainty analysis is estimated about 4% at the flow coefficient of 0.19

• Corrosion Science and Technology
• /
• 제14권6호
• /
• pp.273-279
• /
• 2015

Effects of passive film quality by chemical passivation and solution flow on the corrosion behavior of 304 stainless steel in HCl solution were investigated using a coloration indicator, and by corrosion weight loss, electrochemical polarization and element dissolution measurements. A high redness degree suggests a low passive-film integrity for 304 stainless steel following air exposure, while the minimum redness degree for the samples after chemical passivation suggests a high passive-film integrity. In the static condition, samples subjected to air exposure exhibited a high corrosion rate and preferential dissolution of Fe. Chemical passivation inhibited the corrosion rate due to the intrinsically high structural integrity of the passive film and high concentrations of Cr-rich oxides and hydroxide. Solution flow accelerated corrosion by promoting both the anodic dissolution reaction and the cathodic reaction. Solution flow also altered the preferential dissolution to fast uniform dissolution of metal elements.

• 대한기계학회논문집A
• /
• 제28권12호
• /
• pp.1923-1930
• /
• 2004

This paper presents digital microflow controllers(DMFC), where a fluidic digital-to-analog converter(DAC) is used to achieve high-linearity, fine-level flow control for applications to precision biomedical dosing systems. The fluidic DAC, composed of binary-weighted flow resistance, controls the flow-rate based on the ratio of the flow resistance to achieve high-precision flow-rate control. The binary-weighted flow resistance has been specified by a serial or a parallel connection of an identical flow resistor to improve the linearity of the flow-rate control, thereby making the flow-resistance ratio insensitive to the size uncertainty in flow resistors due to micromachining errors. We have designed and fabricated three different types of 4-digit DMFC: Prototype S and P are composed of the serial and the parallel combinations of an identical flow resistor, while Prototype V is based on the width-varied flow resistors. In the experimental study, we perform a static test for DMFC at the forward and backward flow conditions as well as a dynamic tests at pulsating flow conditions. The fabricated DMFC shows the nonlinearity of 5.0% and the flow-rate levels of 16(2$^{N}$) for the digital control of 4(N) valves. Among the 4-digit DMFC fabricated with micromachining errors, Prototypes S and P show 27.2% and 27.6% of the flow-rate deviation measured from Prototype V, respectively; thus verifying that Prototypes S and P are less sensitive to the micromachining error than Prototype V.V.

• 한국생산제조학회지
• /
• 제8권2호
• /
• pp.35-43
• /
• 1999

The paper describes an approach for measuring delivery flow ripple generated by oil hydraulic axial piston pumps. In order to reduce pressure ripple which cause to undesirable noise. vibration and fatigue in hydraulic systems it is indispensible measure a delivery flow ripple from pumps. Since the flow ripple measurement of flow pumps is independent of the dynamic characteristics of the connected hydraulic circuit the measurement of flow ripple is most suitable for pump fluid-borne noise rating. The measurement of flow ripple with high frequencies from axial piston pumps is made by applying the remote instantaneous flow rate measurement method which is based on the dynamic characteristics between pressure and flow rate in hydraulic pipeline. The measured flow ripple waveforms are influenced by the configuration of V-shaped triangular relief groove in the valve plate. It can be seen that the appropriate relief groove in valve plate reduces the pressure and flow ripple amplitude and frequency spectrum for high harmonics.

• 한국가스학회지
• /
• 제26권4호
• /
• pp.1-8
• /
• 2022

디젤엔진의 대체 연료로 연구되고 있는 청정연료인 DME는 디젤엔진의 중요한 문제 중 하나인 배기가스를 줄일 수 있으며, 세탄가와 산소함유량이 매우 높다. DME는 LPG와 유사한 특성을 가진 연료로 LPG 유통 인프라를 사용할 수 있다. 본 연구에서는 플런저식 고압펌프의 성능평가를 위해 토출된 질량유량에 대한 기초 데이터베이스 구축을 목표로 하였으며, 커먼레일 압력과 모터 회전속도를 변화시켜 플런저식 고압펌프의 질량유량을 분석하였다. 실험 조건은 커먼레일 압력을 300 bar, 400 bar, 500 bar 로 변경하였고, 모터 회전 속도를 300 rpm에서 1000 rpm 으로 증가시켰다. 실험 결과 두 경우 모두 질량유량이 증가하였다.

• 한국기계가공학회지
• /
• 제17권3호
• /
• pp.34-38
• /
• 2018

Recently, the turbo charger has become an important part because it yields little displacement and high power while downsizing the engine's fuel ratio for environmental purposes. In this study, flow analysis was conducted to form the basis of data regarding the best efficiency. The axial displacement was changed from none to 25 mm by controlling the configuration of the turbo charger and the flow analyses were compared with each other. The maximum rate of the outlet of model 1 was 46.36 m/s and the maximum pressure of model 4 was 0.761946 Pa. The maximum flow rate of model 4 was 0.000187650 kg/s. This study's result should aid in the effective design of a turbo charger with high performance.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2002년도 학술대회지
• /
• pp.623-626
• /
• 2002

The object of present study is to find the flow characteristics of centrifugal turbomachinery according to the volute shape change. The experiments were carried out for two model; volute-A designed by free vortex conditions and volute-B designed for use in high mass flow rate conditions using the volute-A test results, Flow measurements were taken in shrouded impeller with 12 backward type blades by using a five-hole pilot-tube and carried out in 4 flow rate, $Q/Q_d\;=0,43,\;1.0,\;1.27,\;1,47$, respectively, For volute-B, we found that pressure distribution was more uniform at high flow rate and from $Q/Q_d\;:\;0,43\;to\;Q/Q_d\;:\;1,20$, losses decreased and efficiency increased compare with volute-A.

• 한국기계가공학회지
• /
• 제20권6호
• /
• pp.82-91
• /
• 2021

We compared the heat transfer characteristics of the parallel and the counterflow flow in the concentric double tube of the Al₂O₃/water nanofluids using numerical methods. The high- and low-temperature fluids flow through the inner circular tube and the annular tube, respectively. The heat transfer characteristics according to the flow direction were compared by changing the volume flow rate and the volume concentration of the nanoparticles. The results showed that the heat transfer rate and overall heat transfer coefficient improved compared to those of basic fluid with increasing the volume and flow rate of nanoparticles. When the inflow rate was small, the heat transfer performance of the counterflow was about 22% better than the parallel flow. As the inflow rate was increased, the parallel flow and the counterflow had similar heat transfer rates. In addition, the effectiveness of the counterflow increased from 10% to 22% rather than the parallel flow. However, we verified that the increment in the friction factor of the counterflow is not large compared to the increment in the heat transfer rate.