• Journal of computational fluids engineering
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• v.15 no.1
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• pp.56-63
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• 2010

Since emission regulations for vehicles have become more stringent, SCR technology has drawn a strong attention in order to reduce NOx emissions. Optimal design of a reductant injection nozzle and a multi-hole plate located between the cone and catalyst is critical in that the uniform distribution of reductant is necessary to maximize the NOx conversion efficiency and minimize the slip of reductant in SCR. In this work, an LPG fuel(C3H8 in vapor state) was used as a reductant for LPG vehicles. A Realizable k-$\varepsilon$ model is used for turbulence, and SCR body is defined as porous media with inertia and viscous resistances measured in this work. Effect of the number of nozzle holes on the flow mixing index was analyzed, which revealed that a four hole nozzle shows the best performance in terms of uniformity of flow. An installment of a multi-hole plate at the entrance of catalyst was evaluated with flow mixing index, uniformity of flow, and pressure drop. A multi-hole plate with gradual hole diameter change in three steps showed the best uniformity of flow within the conditions suggested in this work.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.2 s.233
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• pp.263-270
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• 2005

An experimental study was performed to investigate the effects of partially premixing, varying the equivalence ratios from $0.79{\sim}{\infty}$, on NOx emissions and chemiluminescence of excited $OH^{\ast},\;CH^{ast}\;C_2^{\ast}$ radicals in laminar partially premixed flames. the signal from the electronically excited state of $OH^{\ast},\;CH^{ast}\;C_2^{\ast}$ was detected through a band pass filter with a photo multiplier tube, which are processed to the intensity ratio ($C_2^{\ast}/CH^{\ast},\;C_2^{\ast}/OH^{\ast},\;and\;CH^{\ast}/OH^{\ast}$) to reveal the correlation with local equivalence ratio. And measurements of NOx emission were made to investigate the relationship between visible flame appearance, chemiluminescence, and EINOX. The results demonstrated that (1) the flames at ${\phi}<1.59$ exhibited classical double flame structure, at ${\phi}>4.76$, the flames exhibited diffusion flame structure, and the intermediate flames at $1.59<{\phi}<4.76$ was a merged flame, (2) the $OH^{\ast}$ peak was located inside the $CH^{\ast}\;and\;C_2^{\ast}$ radical for all measured conditions and the emission intensity ratio of $C_2^{\ast}/CH^{\ast}\;and\;C_2^{\ast}/OH^{\ast}$ were identified as good marker for local equivalence ratio over a range of ${\phi}=0.79{\sim}1.2\;and\;CH^{\ast}/OH^{\ast}\;is\;0.79<{\phi}<1.9$. However, it was difficult to predict the equivalence ratio in partially premixed flames using this system for ${\phi}>2.38$, (3) the minimum NOX emission index (EINOx) is obtained for a equivalence ratio of 3.19 in the intermediate flames.

• Journal of the Korean Institute of Gas
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• v.24 no.4
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• pp.39-47
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• 2020

Flue gas recirculation(FGR) is an effective combustion technique for reducing nitrogen oxides(NOx) and is applied in various fields of low-pollution combustion. Continuing the previous study, a numerical analysis was conducted to identify changes of flame characteristics and NOx formation mechanism with applying FGR technique in CH₄/air premixed counterflow flames. NOx emitted was divided into four main reaction paths(thermal NO, prompt NO, N₂H and N₂O), showing relatively the production rate of NO with the recirculation ratio. As a result, thermal NO contributed greatly to the overall NO whereas the effect of N₂H was minimal. In addition, emission index of NO was compared as the recirculation ratio increased by modifying the UC San Diego mechanism to examine the contribution of thermal NO.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.4
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• pp.249-256
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• 2017

Premixed combustion has many advantages, including low CO and NOx emissions and a small combustor volume. These characteristics allow a compact design and wide application to condensing boilers with high thermal efficiencies. This study focused on the combustion characteristics in a premixed combustion burner using metal fiber and a throttle body. The results showed that a blue flame was found to be very stable at a heating load of 6,250-25,000 kcal/h when implementing the proper metal fiber, baffle plate, and throttle body. The NOx emission was less than 11 ppm under an equivalence ratio of 0.724-0.795, and the CO emission was less than 50 ppm under the same equivalence ratio. The thermal efficiency, which is a very important index when condensing a gas boiler, was observed to be above 96.3％ under an equivalence ratio of 0.750.

• International Journal of Automotive Technology
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• v.4 no.2
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• pp.95-100
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• 2003

Automobile industry has been developed rapidly as a key manufacturing industry in Korea. Meanwhile, air pollution is getting worse noticeably than ever. In the diesel emission, PM (Particulate Matter) and NOx (Nitrogen Oxides) have been exhausted with a great amount and the corresponding emission regulations are getting stringent. In order to develop low emission engines, it is necessary to research on better qualified fuels. Sulfur contained in fuel is transformed to sulfur compound by DOC (Diesel Oxidation Catalyst) and then it causes to the increase of sulfate-laden PM on the surface of catalyst. In this research, ULSD (Ultra Low Sulfur Diesel) is used as a fuel and some experimental results are investigated. ULSD can reduce not only PM but also gas materials because cetane value, flash point, distillation 90%, pour point and viscosity are improved in the process of desulfurization. However, excessively reduced sulfur may cause to decease lubricity of fuel and engine performance in fuel injection system. Therefore, it requires only modest adjusted amount of sulfur can improve engine performance and DOC, as well as decrease of emission.

• 한국연소학회:학술대회논문집
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• 2012.04a
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• pp.259-261
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• 2012

The effect of fuel composition and coaxial air on the nitrogen oxide emission index was studied in a non-premixed turbulent jet flame. Validity of experimental setup and methodology is checked. The NOx emission trend is similar with previous works in hydrogen flame, but it's not well in $H_2/CO$ flame. Normalized EINOx scaling with modified $S_G$ applying near-field concept was conducted. Experimental data don't collapse single correlation curve, but partially same trend is observed in all cases.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2198-2203
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• 2008

Hydrogen which can be produced through reforming process of hydrocarbon fuel is supplied into anode side of fuel cell system. In the fuel cell, only 70% of hydrogen is consumed through electrochemical reaction and 30% hydrogen passed by as anode off gas. When electrical output of fuel cell is within range of 1.0 to 3.0kW, burner for the reformer uses only anode off gas. And it uses mixture gas of anode off gas and LNG within range of 3.5 to 5.0kW in electrical output. CHEMKIN 4.1 program's Premixed code was used for calculating the properties of each gas. Results show that burning velocity and adiabatic flame temperature are 34.4cm/s, 1681.7K at equivalence ratio 0.8 within range of 1.0kW to 3.0kW and for cases of 3.5kW, 5.0kW, of electrical output, burning velocity and adiabatic flame temperature represent 30.5, 29.8cm/s and 1722.8, 1750K respectively. CO shows the lowest emission index at equivalence ratio 0.8 and NOx reveals the highest emission index at equivalence ratio 1.

• Journal of the Korean Society of Combustion
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• v.21 no.3
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• pp.7-15
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• 2016

The fuel in conventional liquid fuel combustor is atomized by spray method for high efficiency and low emissions. To improve the overall fuel efficiency and lower pollutant emissions in liquid fuel combustion systems, the effective spatial and temporal separation of droplet evaporation from normal spray process is needed. In this paper, the recuperation of high temperature burnt gas for fuel evaporation was proposed to develop a cylindrical premixed combustor. The recuperation process using U shaped tube is effective to evaporate the liquid fuel. The results show that the flame mode is changed into red radiation flame, blue flame and lift off flame with decreasing equivalence ratio as gas fuel combustion mode. In particular, the blue flame is found to be very stable at heating load 9.2 kW and equivalence ratio 0.731. NOx was measured blow 105 ppm ($O_2$ zero base) from equivalence ratio 0.705 to 0.835. CO which is a very important emission index in liquid fuel combustor was observed below 5 ppm ($O_2$ zero base) under the same equivalence region.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.4
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• pp.500-507
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• 2010

Regard to the global warming, the shipping industries are progressed the dedicated endeavor to reduce greenhouse gas. As the study results of 2009 GHG study team, the $CO_2$ emission of shipping industries exceeded slightly 1.0 billion ton during one year(2007) and it is 3.3% of total $CO_2$ amount exhausted from all industries. This paper are introduced the energy efficiency design index / operation indicator monitoring system(EDiMS) which matched with EVAMOS software released by the dynamics laboratory of Mokpo maritime university. EDiMS can continuously be monitored amounts of $CO_2$, NOx, SOx, and PM emitted from ship and it can be applied as the useful tool of the inventory work of air pollution and the ship energy management plan for the mitigation or reduction of ship emission.

• Proceedings of the KIEE Conference
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• 2001.11c
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• pp.420-423
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• 2001

In this paper, the Multi-FNNs(Fuzzy-Neural Networks) architecture is identified and optimized using HCM(Hard C-Means) clustering method and genetic algorithms. The proposed Multi-FNNs architecture uses simplified inference and linear inference as fuzzy inference method and error back propagation algorithm as learning rules. Here, HCM clustering method, which is carried out for the process data preprocessing of system modeling, is utilized to determine the structure of Multi-FNNs according to the divisions of input-output space using I/O process data. Also, the parameters of Multi-FNNs model such as apexes of membership function, learning rates and momentum coefficients are adjusted using genetic algorithms. An aggregate performance index with a weighting factor is used to achieve a sound balance between approximation and generalization abilities of the model. To evaluate the performance of the proposed model we use the time series data for gas furnace and the NOx emission process data of gas turbine power plant.