• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.22 no.2
• /
• pp.193-204
• /
• 1998

Numerical analysis was performed with multicomponent transport properties and detailed reaction mechanisms for axisymmetric 2-D CH$_{4}$ jet diffusion flame. Calculations were carried out twice with the $C_{2}$-Thermal Mechanism including $C_{2}$ and thermal NO reactions and the $C_{2}$-Full Mechanism including prompt NO reactions in addition to the above $C_{2}$-Thermal NO mechanism. The results show that the flame structures such as flame temperature, major and minor species concentration are indifferent to respective mechanisms. The production path of Thermal NO is dominant comparing with that of Prompt NO in total NO production of pure CH$_{4}$ jet diffusion flame. This is because thermal NO mechanism mainly contributes to positive formation of NO in the whole flame region, but Prompt NO mechanism contributes to negative formation in the fuel rich region. In addition, 0$_{2}$ penetration near the nozzle outlet affects the flame structures, especially N0$_{2}$ formation characteristics.

• 한국연소학회:학술대회논문집
• /
• 1998.10a
• /
• pp.155-164
• /
• 1998

Numerical analysis was performed with multicomponent transport properties and detailed reaction mechanisms for axisymetric 2-D CH4 jet diffusion, partial premixed, premixed flame. Calculations were carried out twice with C2-Full Mechanism including prompt NO reaction in addition to the above C2-Thermal NO Mechanism. The role of thermal NO mechanism and prompt NO mechanism on each flame's NO production is investigated by using the numerical result. The NOx production of each flame were evaluated Quantitatively in terms of the NOx emission index

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.19 no.2
• /
• pp.559-567
• /
• 1995

The combustion process within a porous inert medium (PIM) burner is numerical studied. A detailed chemical reaction scheme including thermal and prompt NO$_{x}$ reactions is used to predict the formation and destruction of pollutants such as NO$_{x}$ and CO. The reaction paths for NO$_{x}$ formation are divided to quantify the amount of NO$_{x}$ formed through thermal NO$_{x}$ reaction or through prompt NO$_{x}$ reaction. Emission index is calculated to compare the actual mass of NO$_{x}$ or CO produced through the combustion of unit mass of fuel. It is found NO formation in PIM burner is confined in flame zone and formation is suppressed due to heat loss at down-stream of the flame. Higher production of NO through prompt NO reaction path is observed due to the higher concentration of fuel derivative species and its higher diffusion at flame front. For all equivalence ratios, CO emission within PIM burner is lower than that from the one-dimensional freely-propagating flame. PIM burner flame has better NO$_{x}$ emission index from .psi. = 0.75 to .psi. = 1.1. to .psi. = 1.1.

• Restorative Dentistry and Endodontics
• /
• v.29 no.5
• /
• pp.423-429
• /
• 2004

The purpose of this study was to evaluate the effect of multiple application of all-in-one dentin adhesive system on microtensile bond strength using confocal laser scanning microscope and microtensile bond strength test. Flat occlusal dentin surfaces were prepared using low-speed diamond saw. In group I, Scotchbond Multipurpose (SM) was applied by manufacturer's recommendation. In group II, after Adper Prompt L-Pop was applied for 15s and light cured for 10s. the second coat was re-applied and light-cured. In group III, after light-curing the second layer. the third coat was re-applied and light-cured. Specimens bonded with a resin-composite were sectioned into resin-dentin stick for measuring the adhesive layer thickness by confocal laser scanning microscope and evaluating micro-tensile bond strength. The adhesive layers of three-step dentin adhesive system. 3 coats of Adper Prompt L-Pop had significantly thicker than SM. 2 coats of Adper Prompt L-Pop (p < 0.05). However. there was no significant differences in bond strengths between SM and 3 coats of Adper Prompt L-Pop (p > 0.05). And SM. 3 coats of Adper Prompt L-Pop had significantly higher than 2 coats of Adper Prompt L-Pop in bond strengths (p < 0.05).

• Journal of the Korean Society of Combustion
• /
• v.11 no.2
• /
• pp.22-27
• /
• 2006

This experimental study has been mainly motivated to obtain generally applicable design correlation for the front mixing premix combustor. The design concept of the front mixing premix combustor is to minimize thermal $NO_x$ and prompt $NO_x$ formation by maintaining low peak flame temperature, and nearly uniform flame temperature through rapid mixing process near the ignition point. The present experimental results clearly indicate that the front mixing premix combustor yields the $NO_x$ level lower than 43 ppm $NO_x$ emissions and the nearly uniform temperature distribution.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.31 no.4
• /
• pp.384-391
• /
• 2007

Hydrogen-blending effects in flame structure and NO emission behavior are numerically studied with detailed chemistry in methane-air counterflow diffusion flames. The composition of fuel is systematically changed from pure methane to the blending fuel of methane-hydrogen through $H_2$ molar addition up to 30%. Flame structure, which can be described representatively as a fuel consumption layer and a $H_2$-CO consumption layer, is shown to be changed considerably in hydrogen-blending methane flames, compared to pure methane flames. The differences are displayed through maximum flame temperature, the overlap of fuel and oxygen, and the behaviors of the production rates of major species. Hydrogen-blending into hydrocarbon fuel can be a promising technology to reduce both the CO and $CO_2$ emissions supposing that NOx emission should be reduced through some technologies in industrial burners. These drastic changes of flame structure affect NO emission behavior considerably. The changes of thermal NO and prompt NO are also provided according to hydrogen-blending. Importantly contributing reaction steps to prompt NO are addressed in pure methane and hydrogen-blending methane flames.

• Proceedings of the KSME Conference
• /
• 2001.06d
• /
• pp.967-972
• /
• 2001

The emission of $NO_{x}$ during coal combustion is a major reason of environment impact. $NO_{x}$ is an acid rain precursor and participates in the generation of smog through ozone production. $NO_{x}$ can be divided into thermal $NO_{x}$, fuel $NO_{x}$ and prompt $NO_{x}$. Thermal $NO_{x}$ is formed in a highly temperature condition dependent. Fuel $NO_{x}$ is dependent on the local combustion characteristics and initial concentration of nitrogen bound compound, while prompt $NO_{x}$ is formed in a significant quantity in some combustion environments, such as low temperature and short residence times. This paper presents numerical simulation of the flow and combustion characteristics in the furnace of a tangential firing boiler of 500MW with burners installed at the every comer of the furnace. The purpose of this paper is to investigate the reduction of $NO_{x}$ emission in a 500MW pulverized coal tangential firing boiler with different OFA's and burner angles. Calculations with different air flow rates of over fired air(OFA) and burner angles are performed.

• 한국연소학회:학술대회논문집
• /
• 2000.12a
• /
• pp.67-76
• /
• 2000

Experimental and numerical investigation on NOx emission characteristics with equivalence ratios, fuel flow rates and nozzle diameters were studied in CH4 Jet flames. Emission indices of NOx were measured by chemiluminescent method with carbon converter. Numerical analyses were carried out with GRl-2.11 mechanism that includes C2-chemistry and all of NO reaction mechanisims. The roles of thermal NO and prompt NO mechanism on each flame's NOx emission index were investigated. The results of this study show that the numerical results represent well the trends of ElNOx experimentally observed. The numerical analyses clarified the trends of EINOx with equivalence ratios, fuel flow rates and nozzle diameters.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.31 no.1 s.256
• /
• pp.99-108
• /
• 2007

In this study, the NOx formation characteristics of one-dimensional $CH_4$/Air premixed flame using detailed-kinetic chemistry are examined numerically. The combustor length and the amount of heat loss are varied to investigate the effect of residence time and heat loss on the NOx formation in a post-flame region. In the flame region, NO is mainly produced by the Prompt NO mechanism including $N_2$O-intermediate NO mechanism over all equivalence ratios. However, thermal NO mechanism is more important than Prompt NO mechanism in the post-flame region. In the case of adiabatic condition, the increase of combustor length causes the remarkable increase of NO emission at the exit due to the increase of residence time. On the other hand, NO reaches the equilibrium state in the vicinity of flame region, considering radiation and conduction heat losses. Furthermore the NO, in the case of $\phi$=1.2, is gradually reduced in the downstream region as the heat loss is increased. From these results, it can be concluded that the controls of residence time and heat loss in a combustor should be recognized as an important NOx reduction technology.

• 한국연소학회:학술대회논문집
• /
• 2000.05a
• /
• pp.35-44
• /
• 2000

It was numerically studied that NOx emission characteristics of confined $CH_{4}$ jet flames with the variation of the diameter of inner fuel nozzle, the flow rate of $CH_{4}$ and equivalence ratio. Parabolic type equations were adopted in the calculation and GRI-2.1I mechanism was used for the chemical reaction. NOx emission index (EINOx) was introduced to evaluate NOx emission quantitatively in parametrically varied flames and the contribution of Thermal and Prompt NO mechanism was discussed. The results showed that Total EINOx varied sensitively with the variation of the flow rate of$CH_{4}$ but it was not sensitive to the variation of the diameter of inner fuel nozzle. Thermal EINOx showed the similar tendency to total EINOx and Prompt EINOx showed insensitivity to the variation of the diameter of inner fuel nozzle and the flow rate of $CH_{4}$.