• 한국연소학회지
• /
• 제14권1호
• /
• pp.9-18
• /
• 2009

The NOx emission characteristics of DME in counterflow nonpremixed flames were investigated numerically, and brief experiments were carried out to compare the flame shapes and NOx emissions with those of $C_{3}H_{8}$ and $C_{2}H_{6}$. The DME flames were calculated using Kaiser's mechanism, while the $C_{2}H_{6}$ flames were calculated using the $C_3$ mechanism. These mechanisms were combined with the modified Miller-Bowman mechanism for the analysis of NOx. Experimental results show that DME flame has the characteristics of partial premixed flame and the flame length becomes very shorter compared with general hydrocarbon fuels and then, the NOx emission of DME is low as much as 60 % of $C_{3}H_{8}$. In the calculated results of counterflow nonpremixed flames, the $EI_{NO}$ of DME nonpremixed flame is low as much as 50 % of the $C_{2}H_{6}$ nonpremixed flame. The cause of $EI_{NO}$ reduction is attributed mainly to the characteristics of partial premixed flame due to the existence of O atom in DME and partly to the O-C bond in DME, instead of C-C bond in hydrocarbon fuels.

• 한국연소학회지
• /
• 제6권2호
• /
• pp.43-49
• /
• 2001

Instantaneous, three-dimensional scalar dissipation rates of the reaction progress variable are measured in turbulent premixed Bunsen flames of lean hydrocarbon/air mixtures with the two-sheet, two-dimensional Rayleigh scattering technique. The flames investigated are located in the turbulent flame-front regime on a newly proposed combustion diagram for premixed flames. The conditionally-averaged mean scalar dissipation rates, $N_{\zeta}$ are found to be lower than the calculated laminar values, indicating a locally broadened flame front. In agreement with previous measurements, the maximum of $N_{\zeta}$, decreases strongly with increasing Karlovitz numbers. The conditional probability density functions are close to a log-normal distribution for scalar dissipation rates conditioned at the progress variable value where the scalar dissipation is maximum in unstretched laminar flame calculations. The time scale for the Favre-averaged mean scalar dissipation rate decreases in general across the turbulent flame brush from the unburnt to burnt side.

• 한국추진공학회지
• /
• 제20권1호
• /
• pp.43-49
• /
• 2016

초음파 진동자에 의해 미립화된 탄화수소계 액체연료를 분사하는 버너(burner)의 연소특성을 고찰하기 위한 실험이 수행되었다. DSLR 카메라를 이용하여 미립화된 액체연료의 화염형상을 획득하였고, 이미지 후처리를 통해 그 구조를 면밀히 분석하였다. 또한 열전대를 이용하여 연소장의 온도도 측정하였다. 그 결과, 버너 내부에 주입되는 수송가스의 질량유량과, 초음파 진동자의 진폭에 비례하여 화염의 크기가 커졌다. 또한, 버너 작동조건의 변이에 따른 연소장의 온도분포를 측정, 제시한다.

• 대한기계학회논문집B
• /
• 제31권11호
• /
• pp.926-935
• /
• 2007

The NOx emission characteristics of DME in laminar coaxial jet and counterflow nonpremixed flames were investigated using experimental and numerical approaches, respectively. The flame structure and NOx emission of DME were compared with those of $C_2H_6$ and $C_3H_8$. The DME flame was calculated using the Kaiser's mechanism, while the $C_2H_6$ and $C_3H_8$ flames were calculated using the $C_3$ mechanism. These mechanisms were combined with the modified Miller-Bowman mechanism for the analysis of NOx. Experimental results show in coaxial jet flame that DME flame has the characteristics of partial premixed flame and the flame length decreases up to 1/3 than that of $C_3H_8$ in the same condition of fuel mass flowrate. Then, the NOx emission of DME decreases to 40% approximately, comparing with that of $C_3H_8$. In the calculated results of counterflow nonpremixed flame, DME flame shows the $EI_{NO}$ decreases up to 50% approximately than those of$ C_2H_6$ and $C_3H_8$ flames when the equivalent fuels are consumed per unit mass and time. Although the overall NOx reaction path of DME is similar with other hydrocarbon fuels, it can be identified that DME flame has a distinct NO reduction mechanism due to the reburning NO chemistry in fuel rich region. From these results, we can conclude that the different NOx emission characteristics of DME flame with other hydrocarbon fuels are attributed to not the temperature increase and the activation of NO reactions due to O atom in DME fuel but the rapid processes of pyrolysis/oxidation.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2003년도 춘계학술대회
• /
• pp.1378-1383
• /
• 2003

Synthesis of carbon nanofibers on a metal substrate by an ethylene fueled inverse diffusion flame was illustrated. Stainless steel plates were used for the catalytic metal substrate. The effects of radial distance and residence time of the substrate were investigated. The role of hydrocarbon composition in the fuel was also viewed. Nanofibers with a diameter range of 30-70 nm were found on the substrate. The carbon nanofibers were formed and grown in the region from 4 to 5.5 mm from the central axis of a flame outside of the visible flame front in the radial direction. The minimum residence time required for the formation of carbon nanofibers were about 20 seconds, and over 60 seconds were required for the full-scale growth. The characteristic time of the formation of carbon nanofibers was much shorter than that of the substrate temperature growth. In this study, the variation in hydrocarbon composition had no significant effect on the formation and growth of the carbon nanofibers.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2007년도 춘계학술대회B
• /
• pp.3317-3322
• /
• 2007

THC(Total Hydrocarbon) emissions during cold start and warm-up phase constitute the majority of THC emissions during the FTP-75 mode. As the basic approach to improve the emission performance of Gasoline engine during transient phase, the effect of spark timing retard from MBT on THC emission characteristics is studied by engine test using a Fast response Flame Ionization Detector(FFID). A cyclic analysis of the combustion process shows that high THC emissions are produced first few cycles during the transient phase. This paper presents the results of engine performance and emission of Gasoline engine with various spark timing. consequently, This paper was focused on the combustion phenomena with various spark timing during transient phase which was analyzed by Fast response Flame Ionization Detector (FFID) equipment to measure the cyclic THC emission characteristics.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
• /
• pp.628-631
• /
• 2017

정상초음파가 인가된 탄화수소계 연료별/공기 혼합물의 당량비에 따른 연소특성 비교를 실험적 연구 결과로 제시한다. 전파화염의 이미지는 고속카메라를 이용하여 획득하였으며, 이미지 후처리를 통해 연료별 연소특성을 면밀히 관찰하였다. 정상초음파를 인가하면 탄화수소계 연료/공기 예혼합기의 이론당량비조건에서 연소반응을 촉진시킨다는 점을 확인하였다.

• 한국추진공학회지
• /
• 제22권6호
• /
• pp.1-10
• /
• 2018

초음파 진동자에 의해 미립화된 탄화수소계 액체연료를 분사하는 버너에서 생성되는 화염의 거동을 고찰하기 위한 실험이 수행되었다. 고속카메라와 열화상 카메라를 이용하여 slit-jet 버너에서 생성된 화염과 연소장 이미지를 획득하였으며, 후처리 과정을 통해 화염과 연소장의 구조변이를 면밀히 분석하였다. 그 결과, 수송기체 유량이 증가하면 연소반응이 촉진되어 연소반응영역이 신장되고, 반응온도가 증가하였다. 또한, 시간 변화에 따른 가시화염과 IR 연소장의 거동변화 비교를 통해 화염의 진동원인을 고찰하였으며, 화염면적의 FFT분석을 통해 생성화염의 진동주파수도 확인하였다.

• 한국연소학회:학술대회논문집
• /
• 한국연소학회 2014년도 제49회 KOSCO SYMPOSIUM 초록집
• /
• pp.207-210
• /
• 2014

The potential of combustion treatment of low concentration VOC on a turbulent partially premixed flame has been studied experimentally. The significant decrease in hydrocarbon concentration from the low concentration VOC was observed with a turbulent partially premixed flame. The VOC/inert gas mixture whose fuel concentration is beyond the flammability limit could be treated in this method.

• 오토저널
• /
• 제13권3호
• /
• pp.25-31
• /
• 1991

The formation process of hydrocarbon emissions was investigated in SI engine. The time- resolved concentrations of hydrocarbon emissions were measured using a high gas sampling valve and a gas chromatography. The gas was sampled at exhaust port, or the position of spark plug, or the wall of combustion chamber. The experiments were conducted using the Alpha engine of Hyundai Motor Company. The fuel used was methanol or propane. It was found that the effect of the quenching layer of combustion chamber wall on hydrocarbon emissions was not significant. The increasing rate of hydrocarbon concentration at combustion chamber wall near crevice and oil layer after flame was reached was much higher than that at the position of spark plug. The hydrocarbon concentrations at exhaust port had two peak values just after opening exhaust valve and just before closing it.