• 한국자동차공학회논문집
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• 제17권5호
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• pp.39-45
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• 2009

An experimental research with 2.0 liter 4-cylinder turbocharged diesel engine was carried out to investigate the combustion and emission characteristics for various alternative fuels. The conventional diesel fuel, neat GTL, blends of 80% of GTL and 20% of biodiesel derived from waste cooking oil are utilized without any modification of engine hardware and ECU data. For GTL and blends of GTL/biodiesel fuel, the ignition delay decreased at the same operating conditions, and overall combustion duration increased slightly. Also, the peak cylinder pressure increased for blends of GTL/biodiesel compared to diesel and GTL fuel. THC and CO emissions with blends of GTL/biodiesel compared to other fuels decreased for the low and middle load conditions. But NOx emission increased due to oxygen content in biodiesel. The number concentrations of PM are higher for blends of GTL/biodiesel than other test fuels in the nucleation mode, while it had an opposite tendency in the accumulation mode, which implies more reduction of PM for blends of GTL/biodiesel on the base of mass concentration.

• 환경위생공학
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• 제5권2호
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• pp.63-80
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• 1990

A sensitive and simple analytical system for the simultaneous determination of residual oxytetracycline, tetracycline, and doxycycline in honey was described, and that the analytical method for determination of residual propionic acid in honey was established. Experimental subjects were purchased four kinds of honey, native kind honey, acaccia honey, mixed floral honey, chestnut honey in Kyung Sang Nam Do. Several microbiological methods are available to determine tetracycline antibiotecs(TCs) in foods but their precision apears to be variable and the specificity is questionable. These methods are considered to be not suitable for analysis of tetracycline antibiotics in honey because honey itself has bacteriostatic action. For determination of tetracycline antibiotics in honey, therefore the High Performance Liquid Chromatography(HPLC) method was applied, and the propionic acid were determined by Gas Chromatography(5.C). Ethylacetate, as an extract solvent, was found to be suitable for seperation of TCs in honey, but methanol and acetone were not. The recoverly rate of Oxytetracycline(OTC), Tetracycline(TC), Doxycycline(DC) from honey spiked at a level of 10 $\mu $g/g were 97%, 89%, and 91%, respectively. The cailbration curve in TCs was linear expression from 2$\mu $g/ml to 10$\mu $g/ml. As the results of analysis, the residual tetracycline antibiotics were not detected in the 100 samples of honey. The recovery rate of propionic acid from honey spiked at level of 10$\mu $g/g was 98.3% , and the calibra lion curves were linear expression from 21$\mu $g/ml to 101$\mu $g/ml. As the results of analysis, the residual propionic acid was not detected in the 100 samples of honey. Retention time(min) of OTC, DC, and TC were 3.35, 4.61, and 5.30 minutes at the conditions of table 2, respectively, and retention time(min) of propionic acid was 3.50 minutes at the conditions of table 3. The residual TCs and propionic acid were not detected in the 100 samples of honey, but there is a possibility that antibiotics or propionic acid will be to remain in honey if they are used during product period in order to prevent putrefaction of honey-bee.

• 한국환경과학회지
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• 제7권6호
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• pp.867-873
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• 1998

Laboratory study was conducted to provide basic data for operating anaerobic sequencing batch reactor(ASBR) process for treatment of nightsoil. The experiments were concerned with digestion characteristics, settleabiltity and dewaterability of digested sludge in ASBR system. Completely-mixed dally-fed control reactor without solid-liquid separation step was also operated to evaluate the baseline performance since the nature of nightsoil was changed with time. In all case, gas production from the ASBR shows 1.3 to 1.44 times higher than that from control, in spite of almost similar trend in organics removal. During thickening period, remarkable decrease in surface settling velocity was observed at the ASBRs compared with the control. In case of the ASBR run, flotation of mixed digested sludge was not occurred. Also, ultimate thickened volume of ASBRs increased 1.2~1.5 times compared with control. Dewaterability of digested sludge without conditioning decreased when the completely-mixed daily-fed reactor for ASBR run was converted to the ASBR. However, improvement of dewaterability of digested sludge from the ASBRs was observed as a result of addition of FeCl$_3$ to digested sludge for conditioning.

• 해양환경안전학회지
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• 제14권4호
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• pp.339-345
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• 2008

기름과 가스 수송 라인 및 선박 내에 설비된 유체 기계들에 관련된 파이프 내에 층상류 흐름이 존재할 수 있다. 이 때문에 수평 혹은 작은 경사 파이프 내에 발생할 수 있는 층상류 흐름을 예측하기 위한 많은 이론과 상관식이 제시되었다. 기존 연구들은 각 상의 물성, 점성, 밀도 및 파이프의 기하학적 형상 등이 층상류 흐름에 주는 효과에 관한 것이 대부분이고, 중력의 크기 및 파이프의 큰 경사 기울기에 관한 연구성과는 매우 드문 실정이다. 따라서 본 연구에는 중력크기 및 파이프 경사도 변화가 층상류 발생 조건에 미치는 영향에 대해 이론적 연구가 수행되었다. 또한 본 해석을 통하여 0.17g 및 0.33g 조건에서는 비록 수직상향 흐름일지라도 매우 낮은 액체상의 유량조건에서는 층상류 흐름이 존재할 수 있음을 알 수 있었다.

• 한국자동차공학회논문집
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• 제11권1호
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• pp.42-48
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• 2003

LPG has been a broad concern of pro-environmental alternative fuel for vehicles. Recently, the new Liquid Phase LPG Injection(LPLI) system extends the limit of power of LPG engine and gives a chance to substitute LPG engine for diesel engine of heavy duty vehicles that are the main resources of air pollution in urban area. Large bore size of heavy duty LPG engine derives a serious knock problem. To find an optimal MBT conditions, it is necessary to know how the flame develops in the combustion chamber and find where the knock positions are. In this study. the ion-probe head gasket was used to estimate the knock position. Inverse operation of the ion-probe signal provides the flame developing characteristics. The further the position is from the spark plug, the later the flame arrives and the more times knock occurs. The main factor that effects knock position is inferred a flor situation of mixed gas in the combustion chamber.

• 한국음향학회지
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• 제15권6호
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• pp.52-58
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• 1996

음파와 진동에너지를 활용하는 음파기술의 응용 연구분야로 음향공진 및 맥진동 현상을 이용하여 기액상에서 산소절달효율을 극대화 할 수 있는 폐수처리용 음향공진 산기관의 개념을 제안하였으며 원리와 성능시험을 수행하였다. 또한 저압용 헬름흘쯔 공진기, 실린더형 및 고리형 반사공진기 그리고 복합 공진시스템의 설계개념과 원리를 구현하였다. 물질전달 과정을 촉진하는 음향공진 에너지는 산소전달효율을 높여주며, 노즐에서 분출하는 공기 제트의 불평형에 의해 발생하는 주기적인 맥진동 현상은 미세한 공기방울을 만들어 내는데, 이 두가지 원리가 가장 잘 적용되는 고리형 반사공진기(AJR)의 성능이 가장 우수한 것으로 평가되었으며 기존의 산기관 보다도 $20{\sim}30%$ 정도 높은 효율을 실험으로 확인하였다.

• Journal of Nutrition and Health
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• 제6권3호
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• pp.17-20
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• 1973

Quantitative analysis was achieved by gas-liquid chromatographic method (GLC) with a single column system of OV-17 for 16 of free amino acids in Korean green tea and the contents of mineral in it was determined by atomic absorption flame emission. The results are summarized as follows: 1) Korean green tea contained Mn 1% or over out of the total ash content and $0.05{\sim}0.20%$ in the water extraction, as the major mineral. 2) Ba, Cr, Ni, Pb and V were analyzed also by small quantities relatively and Co, Tin and Ywere not detected in the water extraction. 3) GLC indicated the presence of 16 components in free ammo acids. 4) The quantities of free amino acids in Korean green tea were determined $2.96{\sim}6.61%$ Alanine, $1.01{\sim}l.89mg%$ Glycine, $2.07{\sim}7.81mg%$ Valine, $1.27{\sim}8.76mg%$ Leucine and Isoleucine, $94.31{\sim}316.27mg%$ Threonine, $9.10{\sim}39.91mg%$ Serine, $2.18{\sim}36.76mg%$ Hydroxyproline, $2.72{\sim}5.90mg%$ Proline, $39.64{\sim}70.02mg%$ Aspartic Acid, $25.93{\sim}101.28mg%$ Glutamic Acid and Lysine, $8.32{\sim}18.30mg%$ Phenylalanine and Tyrosine in trace amount. 5) The total free amino acid contents in Korean green tea ranged from 207.24mg% to 516.06mg% and Moo-Deoung tea contained outstandingly high, 516 mg% or over.

• 한국분무공학회지
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• 제21권2호
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• pp.95-103
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• 2016

The effect of pilot injection quantity on the combustion and emissions characteristics of a compression ignition engine with a biodiesel-compressed natural gas (CNG) dual fuel combustion (DFC) system is studied in this work. Biodiesel is used as a pilot injection fuel to ignite the main fuel, CNG of DFC. The pilot injection quantity is controlled to investigate the characteristics of combustion and exhaust emissions in a single cylinder diesel engine. The injection pressure and injection timing of pilot fuel are maintained at approximately 120 MPa and BTDC 17 crank angle, respectively. Results show that the indicated mean effective pressure (IMEP) of biodiesel-CNG DFC mode is similar to that of diesel-CNG DFC mode at all load conditions. Combustion stability of biodiesel-CNG DFC mode decreased with increase of engine load, but no notable trend of cycle-to-cycle variations with increase of pilot injection quantity is discovered. The combustion of biodiesel-CNG begins at a retarded crank angle compared to that of diesel-CNG at low load, but it is advanced at high loads. Smoke and NOx of biodiesel-CNG are simultaneously increased with the increase of pilot fuel quantity. Compared to the diesel-CNG DFC, however, smoke and NOx emissions are slightly reduced over all operating conditions. Biodiesel-CNG DFC yields higher $CO_2$ emissions compared to diesel-CNG DFC over all engine conditions. CO and HC emissions for biodiesel-CNG DFC is decreased with the increase of pilot injection quantity.

• 한국추진공학회지
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• 제3권3호
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• pp.31-39
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• 1999

OFO, FOF 삼중 충돌형 및 FOOF 이중 분리 충돌형 분무연소장의 3차원 수치해석을 통한 연소성능 예측 및 성능설계 방법에 대하여 고찰하였다. 예조건화 압축성 유동 지배방정식과 저 레이놀즈수 $\kappa$-$\varepsilon$ 2 방정식 난류모델을 바탕으로 LU-SGS 기법을 사용하여 시간적분 하였으며 분무과정은 DSF 방법을 사용하여 모사하였다. n-heptane 액적과 공기를 연료와 산화제로 하는 액체 추진기관 내에서의 분무 연소장을 계산하였으며 연소에서의 난류의 영향은 eddy 소산모델을 사용하여 모사하였다. 분무연소장의 특성과 연소성능이 비교되었으며, 계산 결과 FOF 삼중 충돌형 분사기의 성능이 가장 우수한 반면, OFO 삼중 충돌형 분사기의 성능이 가장 저조한 것으로 나타났다. 연소효율에 중대한 영향을 미치는 파라미터로는 운동량비에 따른 초기 분무 액적의 평균직경과 혼합효율임을 확인하였다. 연소효율은 초기 분무 액적의 평균직경과 반비례, 혼합효율에 비례하여 증가되며, 산화제/연료 혼합비도 비례하여 상승하나, 일정 운동량비 이상에서는 감소되는 것으로 나타났다. 각 분사기 형태에서 운동량비에 따른 연소효율의 변화는 혼합효율의 변화와 동일한 경향을 보이며 그 크기는 분무 액적의 평균직경에 밀접한 관계가 있음을 알 수 있었다.

• Journal of Mechanical Science and Technology
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• 제20권5호
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• pp.710-716
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• 2006

Micro-PIV system with a high speed CCD camera is used to measure the flow field near the advancing meniscus of a water slug in microchannels. Image shifting technique combined with meniscus detecting technique is proposed to measure the relative velocity of the liquid near the meniscus in a moving reference frame. The proposed method is applied to an advancing front of a slug in microchannels with rectangular cross section. In the case of hydrophilic channel, strong flow from the center to the side wall along the meniscus occurs, while in the case of the hydrophobic channel, the fluid flows in the opposite direction. Further, the velocity near the side wall is higher than the center region velocity, exhibiting the characteristics of a strong shear-driven flow. This phenomenon is explained to be due to the existence of small gaps between the slug and the channel wall at each capillary corner so that the gas flows through the gaps inducing high shear on the slug surface. Simulation of the shape of a static droplet inside a cubic cell obtained by using the Surface Evolver program is supportive of the existence of the gap at the rectangular capillary corners. The flow fields in the circular capillary, in which no such gap exists, are also measured. The results show that a similar flow pattern to that of the hydrophilic rectangular capillary (i.e., center-to-wall flow) is always exhibited regardless of the wettability of the channel wall, which is also indicative of the validity of the above-mentioned assertion.