• International Journal of Automotive Technology
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• 제8권6호
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• pp.697-704
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• 2007

Recently, a variable valve timing system has been widely adopted in internal combustion engine in order to improve the fuel economy and torque at low engine speed. In addition, it is known that varying valve timing according to the various engine operations could reduce exhaust gas, especially NOx, because of residual gas by valve overlap. In this study, to improve the low exhaust gas and fuel economy at part load condition, the residual gas and back flow of exhaust gas due to valve overlap were calculated computationally. Moreover, the characteristics of engine performances and NOx formations were investigated with the experiment of combination of intake and exhaust valve timing condition. Under these various valve operating conditions, the effects of both the positive valve overlap and negative valve overlap(valve underlap) were examined simultaneously. Finally, the characteristics of cyclic THC emission were analyzed by using Fast Response FID(FR-FID) in the cylinder, intake port and exhaust port positions. Besides, the effect of the different gradients of the valve timing change on engine performance was investigated and an optimum control strategy was suggested.

• 한국자동차공학회논문집
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• 제6권1호
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• pp.80-89
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• 1998

The residual gas in an spark-ignition engine is one of important factors on emissions and performance such as combustion stability. With high residual gas fractions, flame speed and maximum combustion temperature are decreased and these are deeply related with combustion stability especially at idle and NOx emission at relatively high engine load. Therefore, there is a need to characterize the residual gas fraction as a function of the engine operating load. Therefore, there is a need to characterize the residual gas fraction as a function of the engine operating parameters. In the present study, the quantitative measurement technique of residual gas fraction was studied by using Fast Response Flame Ionization Detector(FRFID). The measuring technique and model for estimation of residual gas fraction were reported in this paper. By the assuming that the raw signal from FRFID saturates with the same slope for firing and misfiring cycle, in-cylinder hydrocarbon(HC) concentration can be estimated. Residual gas fraction can be obtained from the in-cylinder HC concentration measured at firing and motoring condition. The developed measurement and calibration procedure were applied to the limited engine operating and design condition such as intake manifold pressure and valve overlap. The results show relevant trends by comparing those from previous studies.

• 분석과학
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• 제25권6호
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• pp.375-381
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• 2012

본 연구에서는 테들러백에 포집한 가스 시료 중의 NMHCs 성분의 분석을 위한 저온농축장치 시스템을 개발하였다. 개발한 저온농축장치는 냉동고를 이용하여 $-67^{\circ}C$에서 시료를 농축한 후 $180^{\circ}C$의 고온으로 탈착하는 시스템을 제작하였고, 많은 양의 시료가 GC/FID로 주입되게 함으로써 대기 중에 nmol/mol 농도(ppb)의 미량으로 존재하는 가스의 정량을 가능하게 하였다. 저온농축장치의 신뢰성을 위해 수행한 실험에서 농축시간과 피이크 면적이 비례함을 확인하였고, 10% 이내의 재현성과 0.1 nmol/mol의 검출한계를 확인하였다. 본 실험 방법을 실제 시료에 적용하기 위하여 대전, 서산, 고흥의 대기시료와 토양시료에서 채취한 가스 중의 NMHCs를 분석하였다.

• 대한의용생체공학회:의공학회지
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• 제17권4호
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• pp.525-534
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• 1996

We have developed a fast steady state free precession interferometry (SSFPI) technique which is useful for the fMRl (functional Magnetic Resonance Imaging). As is known, SSFP sequence with a suitable adjustment of Vadient (readeut) allows us to measure precession angle 6 which in tw relates to the field inhomogeneity. Combining the two pulses (known as FID and Echo) in FADE (Fast Acquisition Double Echo) sequence, for example, one can obtain the interference term which is directly related to the precession angle It has been known that a fast high resolution magnetic field mapping is possible by use of the modified FADE sequence or SSFPI, and we have attempted to use the SSFPI technique for the susceptibility-induced fMRl. When the method is applied to the susceptibility effect based functional magnetic resonance imaging (fMRl), it was found that the direct susceptibility effect measurement was possible without perturbations such as the backgrounds and inflow effect. In this paper, simulation results and experimental results obtained with 2.0 Tesla MRI system are presented.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.3108-3113
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• 2008

This paper investigated the behaviors of combustion characteristics at part load condition with various intake charge motions induced by the port masking schemes in the CVVT (Continuously Variable valve Timing) engine. Time resolved in-cylinder and exhaust emissions were measured by the fast response HC and NOx analyzers to examine their formation mechanisms and behavior characteristics. As a result, in-cylinder HC decreased with the advanced intake valve timings but HC at the exhaust port increased due to the worse combustion stabilities. However HC reduction could be achieved by the application of the port maskings with a enhancement of the engine stability. NOx also decreased with early intake timings by internal EGR but increased with the charge motion controls which enhance the combustion behavior.

• Journal of Microbiology and Biotechnology
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• 제25권5호
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• pp.704-708
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• 2015

For the analysis of multiple-reaction intermediates for long-chain dicarboxylic acid biotransformation, simple and reproducible methods of extraction and derivatization were developed on the basis of gas chromatography with flame ionization detector (GC-FID) instead of mass spectrometry. In the derivatization step, change of the ratio of pyridine to MSTFA from 1:3 to 9:1 resulted in higher peak intensity (p = 0.021) and reproducibility (0.6%CV) when analyzing 32 g/l ricinoleic acid (RA). Extraction of RA and ω-hydroxyundec-9-enoic acid with water containing 100 mM Tween 80 showed 90.4-99.9% relative extraction efficiency and 2-7%CV compared with those with hydrophobic ethyl acetate. In conclusion, reduction of the pyridine content and change of the extraction solvent to water with Tween 80 provided compatible derivatization and extraction methods to GC-FID-based analysis of longchain carboxylic acids.

• Journal of Mechanical Science and Technology
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• 제19권12호
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• pp.2197-2204
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• 2005

The combination of Gas chromatography (GC) for separation and Flame Ionization Detection (FID) for detection and identification of the components of a mixture of compounds is a fast and strongly proved method of analytic chemistry. The objective of this research was to design a combined High-speed miniature screening Gas chromatograph along with a Flame Ionization Detector for quick, quantitative and qualitative analysis of gas components. This combined GC-FID system is suitable to detect the volatile and semi-volatile hydrocarbons present in a gas mixture. The construction made it less expensive, easy to use and movable. The complete gas path was developed. On/off valves, temperature and flow sensors and their interface electronics were used for controlling purpose. A Microcontroller was programmed to measure the temperature and gas flow using the sensors and to control and regulate them using the electronics and valves. A pocket PC with its touch screen served as a user interface for the system. Software was developed for the pocket PC, which makes the communication possible with the Microcontroller. The system parameters can be indicated in the Pocket PC as simple text and also the analysis result can be displayed.

• 한국자동차공학회논문집
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• 제6권2호
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• pp.212-219
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• 1998

Unburned hydrocarbon is a key contributor to both the fuel economy and emissions of automotive engine. Cyclic variation of HC emission is of importance, especially during throttle transients. The real time measurement of hydrocarbon is particularly important to obtain a better understanding of the mechanisms for combustion and emissions, especially during cold start and throttle transient condition. This paper reports the cycle resolved measurement technique of unburned hydrocarbons to quantify rapid changes of in-cylinder concentration in the vicinity of spark plug by using the Fast Response Flame Ionization Detector(FRFID). While this instrument actually measures fuel concentration, its results can be indicative of the AFR behaviour. In order to understand the rapid change of hydrocarbons with cylinder pressure, it is necessary to study the response time delay of the system, including the time associated with gas transportation to FID. And signal from FRFID is correlated with cylinder pressure data to relate changes in mixture preparation to the classic analysis, such as indicated mean effective(IMEF) and ignition delay, etc.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2910-2915
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• 2008

This paper was investigated the behaviors of the engine and combustion phenomena for various LPG compositions in the semi-return type system, which is not recircurated to LPG tank through furl rail, applied LPi engine during a cold idle condition and including a cold start of the engine. Cyclic HC and NOx emissions were measured at exhaust port to examine their formation mechanical and reduction mechanical with fast response gas analyzers. Various ignition timing is experimented to study the characteristics of combustion phenomena, HC/NOx emissions during fast idle. Also, this study was investigated start delay time, cylinder pressure, HC/NOx emissions, Mass Fraction Burned, starting time to evaluate performance of transient cold startability. Compared to the return type system, the semi-return type system have advantages in point of production cost and equivalent performance of engine starting time and pressure settling time.

• 분석과학
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• 제31권1호
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• pp.23-30
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• 2018

어린이 제품 중 22 종의 알러지 유발 방향성 물질들을 기체 크로마토그래피 불꽃 이온화 검출기(GC-FID)와 기체 크로마토그래피 질량 분석기(GC-MSD)를 사용하여 분석하였다. 분석물질들은 자동속슬렛 추출장치를 사용하여 추출하였으며, 고속 냉동 원심분리기에서 10분동안 원심분리 후 상징액을 2 mL vial 옮겨 Split mode로 주입하여 분석하였다. 확립된 조건에서 검정곡선은 0.996 이상의 상관계수를 갖는 직선성을 보였으며, 감도의 경우는 6.7~1,859,839로서 물질별로 기기특성 및 검출기에 따라 상당히 넓은 범위의 감도를 나타내었다. 기기검출한계는 $0.0032{\sim}0.0335{\mu}g/mL$로서 최대 약 $0.1{\mu}g/mL$이하의 기기검출한계를 나타내었고, 방법검출한계는 $0.0033{\sim}0.1161{\mu}g/mL$의 범위를 나타내었다. 또한 정량한계는 $0.0100{\sim}0.5422{\mu}g/mL$의 범위를 보였고, 정밀도는 0.21~4.89 %, 정확도는 89~111%의 범위를 나타내었다. 본 연구에서 개발한 분석법으로 시판품에 실제 적용하였다.