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공정시스템,이동현상,화학공정안전 : LNG 밀도계를 이용한 저장 탱크 내 LNG 발열량 실시간 측정방법에 관한 연구
하영철 ( Young Cheol Ha ),이성민 ( Seong Min Lee ) 한국화학공학회 2011 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.49 No.1
가스호환성에 문제가 있는 저열량의 LNG가 도입되기 시작한 것은 2005년 동절기부터이다. 이러한 LNG의 도입량은 매년 증가하고 있으며 향후에는 극저열량(발열량 ≤ 9,500 kcal/Nm3)의 CBM(Coal Bed Methane), Shale LNG도 대량 도입될 예정에 있다. 따라서 호환 가능한 발열량의 가스를 인수기지에서 송출하기 위해서는 저장 탱크별 LNG 발열량을 실시간으로 모니터링할 수 있는 방법이 필요하게 되었다. 본 연구에서는 이러한 방법의 일환으로 저장 탱크 내설치된 밀도계를 이용하여 LNG 발열량을 실시간으로 측정할 수 있는 방법을 개발하고자 하였다. 이를 위해 액상 LNG 와 발열량 간의 정밀·정확한 상관식을 도출하고 이 방법의 불확도를 계산하였으며 또 인수기지 내 발열량 측정 시스템을 시험 구축하였다. 본 방법의 유효성을 확인하기 위해 현장 LNG 분석데이터와 비교하였으며 그 결과 0.17~0.47% 정도의 편차를 확인하였다. The low caloric LNG, which didn`t meet the gas interchangeability of Korea, has been imported from 2005 winter season. Amount of this LNG imports has been increased from year to year. In the near future, very low caloric LNG (calorific value ≤ 9,500 kcal/Nm3) such as CBM, Shale LNG will be imported large amounts. For this reason, we need a method for monitoring live calorific values(CV) of LNG in each storage tank to supply gasified LNG with interchangeable CV at LNG receiving terminal. This study was conducted to develope the method for measuring the live CVs of LNG in each storage tank using LNG densitometer. For this purpose, the accurate correlation between CV and density of LNG was derived and the uncertainty of this method was evaluated and also the measuring system for CVs was constructed at LNG receiving terminal. To verify this method, the results of measurement using this method were compared with the field data of LNG analysis and the results showed that the deviations were 0.17~0.47%.
고층건축물의 비틀림방향 변동풍력의 특성에 관한 실험적 연구
하영철(Ha Young-Cheol),김동우(Kim Dong-Woo),길용식(Kil Yong-Sik) 한국유체기계학회 2006 유체기계 연구개발 발표회 논문집 Vol.- No.-
This study aims at verifying characteristics of torsional fluctuating moment coefficient and power spectral density, which is needed to estimate torsional response of tall buildings. In order to estimate characteristics, the wind tunnel tests have been conducted on 52 types aero-elastic model of the rectangular prisms with various aspects ratios, side ratios and surface roughness in turbulent boundary layer flows. In this paper, characteristics of torsional fluctuating wind force are briefly discussed and then these results were mainly analyzed as a function of the aspects ratios and side ratios of buildings.
하영철(Young-Cheol Ha) 대한기계학회 2014 大韓機械學會論文集B Vol.38 No.7
본 연구에서는 천연가스 유량 측정에 사용되는 임계유동함수(CFF)를 AGA8-dc 상태방정식으로 계산할 때 CFF 계산값의 불확도를 평가하였다. CFF 계산에 사용되는 엔탈피, 엔트로피, 음속 식은 불확도 분석이 가능하도록 무차원 헬름홀츠 자유에너지(Helmholtz free energy, HFE)와 이의 편도함수로 표현하였고, HFE의 불확도를 추정하였다. 압축인자의 불확도에 의해 유발되는 종속 변수의 불확도를 반영하기 위해 AGA8-dc 압축인자 식을 해당 불확도만큼 편차가 생기는 형태로 변형하였고, 각 불확도 요인별로 불확도 기여도 평가 모델을 만들었으며, 이를 CFF 계산 프로그램에 적용하였다. 그 결과 CFF의 불확도는 압력 10, 50, 100 bar 에서 각각 0.025, 0.055, 0.112 % 정도로 평가 되었고 압력에 비례하여 증가하는 것을 확인하였다. 또한 본 결과를 기존 CFF 국제비교시험결과(1999년)에 적용한 결과 각 기관별 CFF 값의 차이를 적절히 설명하는 것도 알 수 있었다. In this study, the uncertainties in the critical flow functions (CFFs) calculated by the AGA8-dc equation of state were estimated. To this end, the formulas for enthalpy, entropy, and speed of sound, which are used in calculating the CFF, were expressed in the form of dimensionless Helmholtz free energy and its derivatives, and the uncertainty in Helmholtz free energy was inferred. To consider the variations in the compressibility-dependent variables induced by the variation (i.e., uncertainty) in compressibility, the form of the AGA8-dc equation was modified to have a deviation equal to the uncertainty under each flow condition. For each independent uncertainty component of the CFF, a model for uncertainty contribution was developed. All these changes were applied to GASSOLVER, which is KOGAS"s thermodynamic database. As a result, the uncertainties in the CFF were estimated to be 0.025, 0.055, and 0.112 % at 10, 50, and 100 bar, respectively, and are seen to increase with the increase in pressure. Furthermore, these results could explain the deviations in the CFFs across the different labs in which the CFF international comparison test was conducted under the ISO management in 1999.
하영철(Young-cheol Ha),허재영(Jae-young Her) 한국유체기계학회 2004 유체기계 연구개발 발표회 논문집 Vol.- No.-
We have investigated the feasibility of using differential pressure(pressure drop) of gas turbine meter to diagnose turbine performance degradation caused by mechanical wearing damage and/or dirt buildup or erosion. If the differential pressure between the upstream piping and the throat of a turine meter can be correlated to meter flow rate over the operating range of the meter, then a relatively simple differential pressure measurement in the filed might be used to detect meter performance changes. To test this method, we have conducted two experimental simulation on Straightener Integrated Type(SIT) turbine meter. One is for dirt buildup on turbine blade, the other is for eccentricity of the blade. Results show that this method provide a reliable measure of performace degradation and is useful maintenance indicator.
천연가스 조성 변화에 따른 CNG 엔진 성능 및 배기가스 특성
하영철(Young Cheol Ha),이성민(Seong Min Lee),김봉규(Bong Gyu Kim),이창준(Chang Jun Lee) 대한기계학회 2011 大韓機械學會論文集B Vol.35 No.7
현재 상용되고 있는 CNG(Compressed Natural Gas) 엔진에서 천연가스 조성만 변경했을 때 엔진성능 변화를 실험적으로 규명하였다. 실험에 사용된 엔진은 6606 ㏄, 희박 연소, 공기 과급기가 장착된 타입이며, 점화 시기는 발열량 10454 kcal/N㎥의 가스에 최적화하여 고정시켰다. 실험결과 LNG 발열량이 10454 ㎉/N㎥에서 9811 ㎉/N㎥과 9523 ㎉/N㎥으로 낮아질 때 출력의 경우 평균 3.2, 3.4 %(공연비 미 제어시 3.4, 4.7 %) 각각 낮아지고 열효율은 평균 1.1, 1.5 % 포인트(공연비 미 제어시 1.5, 2.1 % 포인트) 낮아지는 것으로 관찰되었다. 배가스의 경우, 발열량 저하에 따라 이산화탄소, 일산화탄소, 질소산화물의 배출 농도는 모두 감소하는 것으로 나타났으나 THC(Total Hydrocarbon)의 경우에는 일정한 경향이 보이지 않았고 변화량은 크지 않았다. The performance and emission characteristics of a CNG (compressed natural gas) engine were experimentally investigated under different natural gas compositions. The engine specifications were as follows: 6606 ㏄, turbo, lean-burn-type; its ignition timing was fixed for the fuel gas with a HHV (higher heating value) of 10454 ㎉/N㎥. The experimental results showed that when the HHV of the fuel gas was changed from 10454 ㎉/N㎥ to 9811 ㎉/N㎥ and 9523 ㎉/N㎥, the average power reductions were 3.2 % and 3.4 % (1.5 % and 2.1 %, respectively, with A/F control switched off), respectively, and the average thermal-efficiency reductions were 1.1 % and 1.5 % (1.5 % and 2.1%, respectively, with A/F control switched off), respectively. The emissions of CO₂, CO, and NOx decreased as the HHV of the fuel gas was lowered. On the other hand, the emissions of THC (total hydrocarbon) were not consistent, and the extent of change in their emissions was small.
발열량, 웨버지수, 불활성가스 농도로 표현한 가스호환성 판정 도표
하영철(Young-cheol Ha),이승준(Seung-jun Lee),이강진(Kang-Jin Lee) 한국연소학회 2015 KOSCOSYMPOSIUM논문집 Vol.2015 No.5
The existing natural gas interchangeability diagrams, which were expressed in Wobbe index and relative density, etc., do not provide nearly any other information other than the interchangeability. In order to overcome these disadvantages, in this study, the gas interchangeability diagram was expressed in calorific value, Wobbe index and inert gas concentration. The results show that this diagram provides a lot of other information in addition to the interchangeability.