본 연구는 가스추진 174K급 LNG 운반선의 가스 압축기실에서 발생하는 가스누출 모사를 통해 가스탐지기의 최적 위치를 분석하였으며, 새로 개정된 IGC 코드에 명시된 안전규정을 만족하는 합리적인 방법도 함께 제안하였다. 가스압축기실에서의 LNG 가스누출 수치해석을 위해, 실제 ME-GI 엔진이 장착된 174K급 LNG 운반선의 압축기실 형상과 장비, 배관의 배치와 같은 치수로 3D 설계되었다. 가스누설에 대한 시나리오는 305 bar의 높은 압력과 1 bar의 낮은 압력을 적용하여 진행하였다. 고압용 핀홀의 크기는 4.5, 5.0, 5.6 mm이고 저압용은 100, 140 mm이다. 해석 결과, 5.6 mm 핀홀(고압)과 100, 140 mm 핀홀(저압) 상태의 누출에 대한 환기평가에서 가연성 가스농도는 심각한 위험이 없음을 확인하였다. 그러나 개정된 IGC 코드에 따라 설치된 압축기실의 가스 감지 센서의 실제 위치는 다른 지점으로 이동해야 하고, 측정 지점이 현 규정에서 요구하는 것보다 더 추가되어야 함을 확인하였다.
본 연구는 가스추진 174K급 LNG 운반선의 가스 압축기실에서 발생하는 가스누출 모사를 통해 가스탐지기의 최적 위치를 분석하였으며, 새로 개정된 IGC 코드에 명시된 안전규정을 만족하는 합리적인 방법도 함께 제안하였다. 가스압축기실에서의 LNG 가스누출 수치해석을 위해, 실제 ME-GI 엔진이 장착된 174K급 LNG 운반선의 압축기실 형상과 장비, 배관의 배치와 같은 치수로 3D 설계되었다. 가스누설에 대한 시나리오는 305 bar의 높은 압력과 1 bar의 낮은 압력을 적용하여 진행하였다. 고압용 핀홀의 크기는 4.5, 5.0, 5.6 mm이고 저압용은 100, 140 mm이다. 해석 결과, 5.6 mm 핀홀(고압)과 100, 140 mm 핀홀(저압) 상태의 누출에 대한 환기평가에서 가연성 가스농도는 심각한 위험이 없음을 확인하였다. 그러나 개정된 IGC 코드에 따라 설치된 압축기실의 가스 감지 센서의 실제 위치는 다른 지점으로 이동해야 하고, 측정 지점이 현 규정에서 요구하는 것보다 더 추가되어야 함을 확인하였다.
This study analyzes the optimal location of gas detectors through the gas dispersion in a cargo compressor room of a 174K LNG carrier equipped with high-pressure cargo handling equipment; in addition, we propose a reasonable method for determining the safety regulations specified in the new Internat...
This study analyzes the optimal location of gas detectors through the gas dispersion in a cargo compressor room of a 174K LNG carrier equipped with high-pressure cargo handling equipment; in addition, we propose a reasonable method for determining the safety regulations specified in the new International Code of the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk (IGC). To conduct an LNG gas dispersion simulation in the cargo compressor room-equipped with an ME-GI engine-of a 174 K LNG carrier, the geometry of the room as well as the equipment and piping, are designed using the same 3D size at a 1-to-1 scale. Scenarios for a gas leak were examined under high pressure of 305 bar and low pressure of 1 bar. The pinhole sizes for high pressure are 4.5, 5.0, and 5.6mm, and for low pressure are 100 and 140 mm. The results demonstrate that the cargo compressor room will not pose a serious risk with respect to the flammable gas concentration as verified by a ventilation assessment for a 5.6 mm pinhole for a high-pressure leak under gas rupture conditions, and a low-pressure leak of 100 and 140 mm with different pinhole sizes. However, it was confirmed that the actual location of the gas detection sensors in a cargo compressor room, according to the new IGC code, should be moved to other points, and an analysis of the virtual monitor points through a computational fluid dynamics (CFD) simulation.
This study analyzes the optimal location of gas detectors through the gas dispersion in a cargo compressor room of a 174K LNG carrier equipped with high-pressure cargo handling equipment; in addition, we propose a reasonable method for determining the safety regulations specified in the new International Code of the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk (IGC). To conduct an LNG gas dispersion simulation in the cargo compressor room-equipped with an ME-GI engine-of a 174 K LNG carrier, the geometry of the room as well as the equipment and piping, are designed using the same 3D size at a 1-to-1 scale. Scenarios for a gas leak were examined under high pressure of 305 bar and low pressure of 1 bar. The pinhole sizes for high pressure are 4.5, 5.0, and 5.6mm, and for low pressure are 100 and 140 mm. The results demonstrate that the cargo compressor room will not pose a serious risk with respect to the flammable gas concentration as verified by a ventilation assessment for a 5.6 mm pinhole for a high-pressure leak under gas rupture conditions, and a low-pressure leak of 100 and 140 mm with different pinhole sizes. However, it was confirmed that the actual location of the gas detection sensors in a cargo compressor room, according to the new IGC code, should be moved to other points, and an analysis of the virtual monitor points through a computational fluid dynamics (CFD) simulation.
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문제 정의
Thus, it is positively necessary to identify the optimum number of gas detection sensors and their locations to prevent or mitigate a gas accident. In this paper, we present a reasonable method for identifying the risk of an explosion and to determine the optimal location of gas detecting devices. To examine the above-stated points, an LNG gas dispersion simulation for a high/low-pressure leakage in the cargo compressor rooms of 174K ME-GI LNG carriers was carried out according to the volume flow rate of the leak and the new IGC code.
제안 방법
Scenarios for a gas leak were examined for high pressure at 305 bar and for low pressure at 1 bar. High-pressure gas leak scenarios were examined for 4.5, 5.0, and 5.6 mm pinhole sizes (case 1~3), and low-pressure leak scenarios were examined for 100 and 140 mm pinhole sizes (case 4 and 5). Transient gas simulations were adopted to obtain the values of various time steps.
In this research, the LNG gas leak scenarios consisted of a high-pressure leak and a low-pressure leak. Fig.
LNG gas dispersion simulations were carried out in a cargo compressor room in accordance with the pinhole sizes, and the boundary condition was set to two (2) "pressure in" natural vents, seventeen (17) "pressure out" mechanical ventilators, and a "mass-flow-inlet" at the leakage points.
One(1) of the gas detection sensors which is the nearest point 30 % LFL (Lower Flammable Limit) of the total four(4) sets was alarmed after the gas leak and then leaked gas was continuously discharged during 10 s and then stopped. Mechanical ventilators were continuously operated before and after the leak, and the methane gas behavior and ventilation capabilities were monitored in this study.
6 mm, and the transient flow calculation was carried out until 503s. The low-pressure leakage scenario was composed of two (2) cases, with pinhole diameters of 100 and 140 mm, and a transient flow calculation was carried out until 4,200s.
This research analyzes the optimal gas detecting system through the gas leak and dispersion of both a high-pressure leak and a low-pressure leak according to the varying scenarios that can occur. The ventilation capability in the room and the gas detection sensor locations were verified through a comparison between a real gas detection sensor and the virtual monitor points.
Through this study, we identified the ventilation capability with relatively cold and heavy LNG gas from low pressure partially under the deck and compared it with hot and light LNG gas at high pressure. The quantitative data obtained through the numerical simulation will help our understanding of the risk factors based on the flow characteristics of not only an ME-GI LNG ship but also similar ships.
To conduct the LNG gas dispersion simulation in a cargo compressor room, a 174K LNG vessel built by DSME in Korea was selected to have the same 3D size, not only for the equipment but also for the compressor room geometry, and the initial conditions and leak scenario were defined according to the pinhole sizes.
In this paper, we present a reasonable method for identifying the risk of an explosion and to determine the optimal location of gas detecting devices. To examine the above-stated points, an LNG gas dispersion simulation for a high/low-pressure leakage in the cargo compressor rooms of 174K ME-GI LNG carriers was carried out according to the volume flow rate of the leak and the new IGC code. The ventilation capability and the locations of gas detection sensor were verified through comparison between actual gas detection sensor and virtual monitor points.
Bafjord (2011) has examined the most suitable location for gas detection in offshore installations for oil and gas production and evaluated the effects on the functionality and reliability of the gas detection system. Using FLACS, he studied the physical factors that affect the optimum behavior of the exhaust gas with wind speed, wind direction, source of leakage, leakage direction, rate of leakage, gas composition and geometry. Because rapid detection of escape gases is one of the key requirements associated with the gas detection system, the detection time is an important factor in the reliability of the system.
대상 데이터
2. Real gas detection sensor and virtual monitor points in cargo compressor room of 174K LNG vessel.
To realize the gas dispersion simulation, the actual physical properties of LNG gas were applied, as defined in Table 1. The LNG consumed in the model ship was provided by the Korea Gas Corporation (KOGAS). LNG can be obtained from different sources and may have different compositions, implying that the heat value is a variable.
The LNG gas leak and dispersion were analyzed at high and low pressures ccording to the pinhole size for a cargo compressor room of a 174K ME-GI LNG vessel. Scenarios for a gas leak were examined for high pressure at 305 bar and for low pressure at 1 bar.
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