• 한국가스학회지
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• 제27권2호
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• pp.57-64
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• 2023

가스계량기의 검침방식이 발전하면서 원격검침이 가능한 스마트 가스 계량기(누출점검용 계량기 및 다기능 안전 계량기)가 사용되고 있다. 이러한 계량기는 부가기능으로 수집하는 유량 및 압력 데이터를 활용하여 누출 판단을 하는 기능이 있다. 유량 데이터를 이용한 누출판단 기능은 실제 현장에서 유효한 사례가 있지만 압력 데이터 기반 누출 판단 기준은 누출로 인한 압력 값 변화뿐만 아니라 여러 요인(정압기 압력 크기, 인접 계량기 연계, 인접 주택 사용량, 계량기 위치 등)으로 압력 크기 변화(레벨)가 있는 문제점이 있다. 본 논문에서는 스마트 가스계량기에서 수집되는 압력데이터를 활용하여 누출여부를 판단 할 수 있는 기법으로 압력 데이터 전처리 방법과 누출 여부 관련 압력 값 범위 기준, 누출판단 기법 및 적용 사례 검증을 통해 개발하였다.

• 설비공학논문집
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• 제13권2호
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• pp.134-143
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• 2001

This paper presents the characteristics of flank and tip seal leakage in a scroll compressor for air-conditioners with R-22 under actual operating conditions. It is well known that the leakage has significant effect on the performance of the scroll compressor. Experiments were performed by using indirect method for measuring mass flow rate passing through flank and tip seal under actual operating conditions, In addition, an analytical model for tip seal leakage was developed to investigate tangential and radial leakage observed at grooves and contact points of tip seals. For low oil concentration, theoretical results were compared with experimental data to verify the analytical model. As a result, leakages through flank and tip seal parts were evaluated as afunction of pressure ratio, orbiting angle, discharge pressure, tip clearance, and leakage point. It was also found that the tip seal leakage was considerable even though the tip seal provided adequate sealing effect.

• Tribology and Lubricants
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• 제14권4호
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• pp.15-22
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• 1998

Recently, the importance of variable displacement piston pump is increasing in industrial world. Especially, most consumers require various range of pressures and flow rates. Pressure compensator is a system controlling flow rate in piston pump at low cost and, therefore, satisfies the need of consumers. However, the system has serious problems, such as response and leakage. The response and leakage are affected by clearance between actuator piston and cylinder, roughness of surface, and spool overlap. In this paper, these effects are investigated experimentally, and optimal clearance and chamfer is obtained. While diameter of cylinder is fixed and diameter of actuator piston is changed in this experiment, response and leakage are measured. Also parameters such as roughness and processing accuracy are changed for piston of fixed clearance. Experimental setup modelled into several parts of actuator piston, cylinder, spool, and swash plate. Input pressure is changed by function generator and proportional valve. The result of this experiment shows that leakage increases very much in proportion to the increase of clearance, and especially leakage occurs enormously when clearance is more than 0.002. The response is not good because as clearance increases leakage increases and as clearance decreases viscous damping effect increases. Accordingly, it is found out that optimal clearance range exists for tile response, within about 0.0012∼0.0014, at this time. Futhermore, the better roughness and geometrical accuracy of actuator piston are, the smaller are leakage and friction. The paper informs that response and leakage are influenced by and geometrical accuracy of actuator piston, roughness of surface, and the clearance between actuator piston and cylinder, and that optimal design of actuator piston in the pressure compensator is possible.

• 한국산학기술학회논문지
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• 제17권5호
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• pp.26-35
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• 2016

수소는 공해가 없는 청정에너지 자원으로, 이를 활용하기 위한 많은 연구가 진행되고 점차 생산 및 소비량이 늘어날 것으로 전망된다. 그러나 수소의 열화학적 특성 상 매우 높은 가연성을 가지며, 특히 밀폐공간에서 수소 가스가 누출되는 경우에 위험성이 높다. 본 연구에서는 전산유체역학 해석기법을 적용하여 밀폐된 공간 내부의 수소가스 누출 현상에 대한 수치해석 연구를 수행하였고, 실험결과와 비교하였다. 또한, 검증된 해석기법을 적용하여 누출공의 크기에 따른 가스 확산 거동에 대하여 해석하고 다양한 기법을 통해 분석하였다. 누출 시간 경과에 따른 공간 내의 가연영역을 누출공 크기 별로 확인하고, 가연영역의 체적분율을 통하여 누출공의 크기가 증가할수록 공간 내부의 가연영역은 급속히 성장함을 확인하였다. 또한 수소 가스의 누출량과 가연영역이 천장까지 성장하는 최소 소요시간 사이의 관계를 도출하였다. 특정 모니터링 지점에서 가스 몰분율 분석을 통해 가스는 형상 규모의 영향을 받지 않고 등방적 특성으로 퍼져나감을 확인하였으며, 특정 지점에서의 가스 농도는 누출구로부터 발생하는 주 유동의 효과와 밀폐공간에서의 가스 누적 효과를 모두 고려해야 함을 알 수 있었다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.773-777
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• 2005

This article is about using information technology to apply with water loss inspection system in District Metering Area (DMA). Inspector can check Flow rate and Minimum Night Flow; NMF via Smart Phone or PDA include sending SMS Alert in case the Pressure, Flow rate and NMF is over the range of controlling. This will be used as equipment to implement water loss in international proactive and can keep on water loss reduction more efficiency. The system consists of Data Logger which collects data of Flow rate from DMA Master Meter. PC is Wap Server which dial via modem in order to get data through FTP Protocal that will convert text file to Microsoft Access Database. Wappage will use xhtml language to show database on Wapbrowser and can show the result on Smart Phone or PDA by graph and table for system analysis.

• Journal of Chest Surgery
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• 제13권4호
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• pp.321-337
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• 1980

The increasing use of cardioplegic solution for the reduction of ischemic tissue injury requires that all cardiplegic solution be carefully assessed for any protective or damaging properties. This study describes functional, enzymatic and structural assessment of the efficiency of three cardioplegic solutions (Young & GIK, Bretschneider, and $K^{+}$ Albumin solution) in a Modified Isolated Rat Heart Model of cardiopulmonary bypass and ischemic arrest. Isolated rat heart were subjected to a 2-minute period of coronary infusion with a cold cardioplegic or a noncardioplegic solution immediately before and also at the midpoint of a 60-minute period of hypothermic ($10{\pm}1$. C) ischemic cardiac arrest. The results of this study were as follow: 1. Spontaneous heart beat after ischemic arrest occured 16 seconds later after Langendorff reperfusion in the Young & GIK group (n=6), and 40 second later in the Bretschneider group (n=6) and 6 minute later in the $K^{+}$ Albumin group (n=6), and 16 minute later in the control group (non-cardioplegia). A good recovery state of spontaneous heart beat was shown in the Young & GIK and Bretschneider groups. 2. The percentage of recorveries of heart function at 30 minute after postischemic working heart perfusion were : heart rate $91.6{\pm}3.1$% (P<0.01)m oeaj airtuc oressyre $83{\pm}3$% (P<0.01), coronary flow $70{\pm}8$% (P<0.05) and aortic flow flow rate $39{\pm}9.3$% (P<0.05) in the Young & GIK group. This percentage of recoveries of the Young & GIK group was significantly greater than the control group. In the Bretschneider group, the percentage of recoveries were : heart rate $87.8{\pm}7.5$%(P<0.05), peak aortic pressure $71{\pm}2.3$% (P<0.05) and aortic flow rate $33.2{\pm}6.6$%(P<0.05). hte percentage of recoveries were significantly greater than in the control group. In the $K^{+}$ Albumin group, recoveries of heart function were poor. 3. Total CPK leakage was $131.2{\pm}12.75$IU/30 min/gm. dry weight in the control group, $50.65{\pm}12.75$IU in the Young & GIK gruop, $69.40{\pm}32.21$Iu in Bretschneider group, and $103.65{\pm}15.47$IU in the $K^{+}$ Albumin group during the 30 minute postischemic Langendorff reperfusion. Total CPK leakage was significantly less (P<0.001) in the Young & GIK group, than in the control group. 4. Direct correlatin between percentage recovery of aortic flow rate and total amount of CPK leakage from Myocardium was noticed.(Correlation Coefficient r = 0.76, P<0.001). 5. Mild perivascular edema was the only finding of light microscopic study of myocardium after 60 minute ischemic arrest with cold cardioplegic solutions and hypothermla.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2011년 춘계학술대회논문집
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• pp.477-482
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• 2011

In the present study, the diffusion process of hydrogen leaking from a FCV (Fuel Cell Vehicle) in an underground parking lot was analyzed by numerical simulations in order to assess the risk of a leakage accident. The temporal and spatial changes of the hydrogen concentration as well as the flammable region in the parking lot were predicted numerically. The effects of the leakage flow rate and an additional ventilation fan were investigated to evaluate the ventilation performance in the parking lot to relieve the accumulation of the leaked hydrogen gas. The present numerical analysis can provide useful information such as the distribution of the leaked hydrogen concentration for safety of various hydrogen applications.

• Nuclear Engineering and Technology
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• 제48권5호
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• pp.1280-1290
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• 2016

This paper presents an advanced estimation method for obtaining the probability density functions of a damage parameter for valve leakage detection in a reciprocating pump. The estimation method is based on a comparison of model data which are simulated by using a mathematical model, and experimental data which are measured on the inside and outside of the reciprocating pump in operation. The mathematical model, which is simplified and extended on the basis of previous models, describes not only the normal state of the pump, but also its abnormal state caused by valve leakage. The pressure in the cylinder is expressed as a function of the crankshaft angle, and an additional volume flow rate due to the valve leakage is quantified by a damage parameter in the mathematical model. The change in the cylinder pressure profiles due to the suction valve leakage is noticeable in the compression and expansion modes of the pump. The damage parameter value over 300 cycles is calculated in two ways, considering advance or delay in the opening and closing angles of the discharge valves. The probability density functions of the damage parameter are compared for diagnosis and prognosis on the basis of the probabilistic features of valve leakage.

• International Journal of Fluid Machinery and Systems
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• 제2권1호
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• pp.72-79
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• 2009

The effect of symmetric and asymmetric micro regenerative pump impellers on their pressure performance was studied. The shut off head of the pump with the symmetric impeller was about 2.5 times as that with the asymmetric impeller. The computation of the internal flow was performed to clarify the cause of the increase of the head. It was found that the contribution of the angular momentum supply was larger than that of shear stress for the head development in both cases. The larger head and momentum supply in the case of the symmetric impeller were caused by larger recirculated flow rate and larger angular momentum difference between the inlet and outlet to the impeller. The larger recirculated flow rate was caused by smaller pressure gradient in the direction of recirculated flow. The decrease of the circumferential velocity in the casing was attributed to the smaller local flow rate in the casing.

• 한국가스학회지
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• 제21권5호
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• pp.16-26
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• 2017

화학플랜트 산업단지 내의 플랜지, 밸브 등의 이음새 및 저장탱크의 균열 등에서 발생되는 원료, 중간재, 제품가스의 누출 유무와 누출량을 확인하는 것은 안전 관점이나 경제적 관점에서 매우 중요하다. 광학가스이미지 기술은 누출 유무를 확인하는데 사용되고 있으나 누출량을 표시하지 않는다. 일부기기는 검출 가능한 가스에 대한 색상 구분과 농도에 따른 색상의 진함으로 나타내고 있다. 따라서 OGI영상에서 유출량의 정량화에 대한 연구가 필요하다. 본 실험적 연구는 광학가스이미지로 부터 유출량의 정량표시에 관한 것이다. 2 차원의 OGI영상으로 3 차원에 분포되어 있는 누출가스 양을 추정하기 위하여 몬테카를로 확률기법을 적용하였다. 산출면적 기준은 가로(2.54 cm), 세로(2.54 cm)의 2 차원의 OGI영상 점의 수에 대해 3 차원의 가스 분포 유출량과의 상관관계계수를 구하니 그 평균값이 0.980이었다. OGI영상의 이러한 데이터 표를 이용하여 역으로 유출량을 추정한 결과 유량계 측정값과 일치도가 높음을 확인했다.