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Here, we investigated the characteristics of the environmental multimedia distribution of microcystins (MCs) introduced from freshwater discharge through the estuary dam of the Geum River. In addition, the applicability of a passive sampling device (polar organic chemical integrative sampler, POCIS) for monitoring MCs was evaluated. Surface water, suspended solids (SS), sediments, and oysters were collected from the inner and outer estuary dam. Seven MC variants were analyzed using HPLC-MS/MS. POCIS was deployed at three sites over one week, and MCs were monitored for four weeks from August to September 2019. Before POCIS was deployed in the field, compounds-specific sampling rates of MCs were determined as functions of water temperature (10, 20, and 30 °C), flow rate (0, 0.38, and 0.76 m s−1), and salinity (0, 15, and 30 psu) in the laboratory. The sampling rates of MCs in POCIS increased significantly with increasing water temperature and flow rate, whereas salinity did not significantly affect the sampling rates between freshwater and saltwater. The MCs in the Geum River Estuary mainly existed as particulate forms (mean: 78%), with relatively low proportions of dissolved forms (mean: 22%), indicating that MCs were mainly contained in cyanobacterial cells. There was no significant correlation among the concentrations of MCs in water, SS, sediments, and oysters. Time-weighted average concentrations of MCs from POCIS were not significantly correlated with the concentrations of MCs in water and oysters. The metabolites of MCs, including MC-LR-GSH, MC-LR-Cys, MC-RR-GSH, and MC-RR-Cys, were detected in oysters (no metabolites were detected in POCIS). Overall, POCIS can be useful for monitoring dissolved MCs in the aquatic ecosystem, particularly in calculating time-weighted average concentrations, but it seems to have limitations in evaluating the contamination status of total MCs, mainly in particulate form.

This study presents a preliminary thermodynamic research on the development of a new boiler (called a WSWHR boiler), which aims to recover waste heat from an exhaust-gas stream by spraying additional water onto the incoming air stream. In this boiler, the water condensed at the main boiler and the waste-heat-recovery system is reserved in one tank and then recirculated by spraying onto the incoming air during heat recovering process. This new boiler shows no limitation in operation because all the water condensed at the main boiler and the waste-heat exchanger is sprayed onto the incoming-air stream and reacting zone in the combustion chamber. The WSWHR boiler is expected to have an efficiency as high as 92–98% when the boiler outlet temperature is controlled near 50–70 °C. The maximum difference in efficiency occurs near 60 °C in T G - Bo , and its values are about 8% and 6% greater than those of the basic and WHR boilers, respectively. Furthermore, as more water is added onto the incoming air, the NOx emission predicted by simple Chemkin model decreases significantly.

The effects of flow structure and flame dynamics on combustion instabilities in a lean premixed swirl combustor were numerically investigated using Large eddy simulation (LES) by varying the inlet geometry of combustor. The dynamic k sgs -equation and G-equation flamelet models were respectively employed as the LES subgrid models of turbulence and combustion. The divergent half angle (α) in the combustor inlet was varied systematically from 30° to 90° to quantify the effect of inlet geometry on the combustion instabilities. This variation caused considerable deformation in recirculation zones in terms of their size and location, leading to significant changes in flame dynamics. Analysis of unsteady pressure distributions in the combustor showed that the largest damping caused by combustion instabilities takes place at α = 45°, and the amplitude of acoustic pressure oscillation is largest at α = 30°. Examination of local Rayleigh parameters indicated that controlling flame-vortex interactions by modifying inlet geometry can change the local characteristics of combustion instabilities in terms of their amplification and suppression, and thus serve as a useful approach to reduce the instabilities in a lean premixed swirl combustor. These phenomena were studied in detail through unsteady analysis associated with flow and flame dynamics.

Allergic dermatitis (AD) clinically presents with skin erythematous plaques, eruption, and elevated serum IgE, and T helper cell type 2 and 1 (Th2 and Th1) cytokine levels. 6-Shogaol [1-(4-hydroxy-methoxyphenyl)-4-decen-one], a pungent compound isolated from ginger, has shown anti-inflammatory effects, but its inhibitory effects on AD are unknown. The aim of this study was to examine whether 6-shogaol inhibits AD-like skin lesions and their underlying mechanism in vivo and in vitro. An AD-like response was induced by tumor necrosis factor-α (TNF-α)+IFN-γ in human keratinocytes or by 2,4-dinitrochlorobenzene (DNCB) in mice. In vivo, 6-shogaol inhibited the development of DNCB-induced AD-like skin lesions and scratching behavior, and showed significant reduction in Th2/1-mediated inflammatory cytokines, IgE, TNF-α, IFN-γ, thymus and activation-regulated chemokine, IL-1, 4, 12, and 13, cyclooxygenase-2, and nitric oxide synthase levels. In vitro, 6-shogaol inhibited reactive oxygen species (ROS) and mitogen-activated protein kinases (MAPKs) signaling, and increased the levels of total glutathione, heme oxygenase-1, and quinone 1 via nuclear factor erythroid 2 related factor 2 (Nrf2) activation. 6-Shogaol can alleviate AD-like skin lesions by inhibiting immune mediators via regulating the ROS/MAPKs/Nrf2 signaling pathway, and may be an effective alternative therapy for AD.

In this study confirmed the reduction effect of pollutant by applying Fi-EGR and FPI-EGR to hybrid combustion system realizing premixed flame and non-premxied flame at once. The results showed that NOx emission index decreased significantly in case of adopting EGR. Additionally, the hybrid combustion system with EGR resulted in a better performance compared to usual non-premixed combustion system such that it can reduce NO x emission at equivalent EGR ratios. Especially, in the case of 25% of FI-EGR ratio at hybrid combustion system that the ratio of non-premixed and premixed is 50 : 50, NOx emission index reduction rate was about 59% compared to NO x emission of non-premixed combustion system without EGR and in the case of 15% of FPI-EGR ratio at hybrid combustion system that the ratio of non-premixed and premixed is 70 : 30, NO x emission index reduction rate was about 48% compared to NO x emission of hybrid combustion system without EGR. Key words : Hybrid combustion, Exhaust gas recirculation (EGR), NO

The authors recently proposed a heat recovery boiler with water spray (HR-B/WS), where water was sprayed onto the inlet airstream and/or reaction zone. We also introduced a chain-block structure analysis method to determine thermal efficiency and provide information regarding capacity design specifications for each system component (see Part Ⅰ of the paper). Although we showed that HR-B/WSs produced excellent thermal efficiency and NOX emission, principal parameter effects on system performances and optimized operating conditions were not sufficiently well determined to allow effective system control and design. Therefore, the present study performed parametric analyses for each parameter’s performance to derive design specifications for the HR-B/WS system components. This information is essential to design laboratory and pilot scale research systems to confirm industrial boiler (under development) performances.

The effects of the number of heat exchanger modules on thermal characteristics were experimentally studied in a premixed combustion system with a cross-flow staggered-tube heat exchanger. The various heat exchanger modules, from 4 to 8, combined with a premixed burner were tested to investigate the performance of the heat exchanger through the surface area of the heat exchanger at various equivalence ratios. Additionally, the performance of the heat exchanger was analyzed by applying entropy generation theory to the heat exchanger system. As a result, although the heat transfer rate increases with the increase of the equivalence ratio, the NOx and CO concentrations also increase due to the increasing flame temperature. In addition, the entropy generation increases with an increase of the equivalence ratio. Furthermore, the heat transfer rate and the effectiveness are increased with the increase of the number of the heat exchanger modules. Also, the effectiveness is sharply increased when the number of the heat exchanger modules is increased from 4 to 5. Consequently, the optimal operating conditions regarding pollutant emission, effectiveness and entropy generation in this experimental range are 0.85 for the equivalence ratio and 8 for the number of heat exchanger modules.

This study was investigated the estimation of VOCs (Volatile Organic Compounds) emission from a gas station tank. To improve the atmosphere environmental quality near the gas station, the installation of vapor recovery system has been expanded recently. Therefore, it was necessary to calculate VOCs emissions from the gas station tank with vapor recovery systems for evaluation of their performance. The VOCs emissions are difficult to measure directly because of various sources and irregularly emission by pressure rise. In this study, VOCs emissions were estimated by simple calculation based on the equation of state for measured pressure, temperature and volume of a gasoline tank at a gas station. The result confirmed that the present national emission factor did not have significant discrepancy with the calculated value.

In this study, the characteristics of NOx emissions for CH4/air non-premixed flames using EGR (exhaust gas recirculation) methods were investigated using the AI-EGR (air-induced-EGR) and FI-EGR (fuel-induced-EGR) methods. For the fundamental experiment, coaxial non-premixed flames were verified using the non-premixed mode in a changeable EGR hybrid combustion system. For the numerical simulation, the 2-D commercial FLUENT program was used to verify the distributions of the flame temperature and mole fraction of the NO emissions. Additionally, the swirling non-premixed flames were tested to investigate a practical combustion system. Based on experimental results, the reduction rates of EI NO X for the FI-EGR method and the AI-EGR were approximately 29% and 28% for an EGR ratio of 20% and 25%, respectively, which represented the maximum range needed to generate a stable flame. Based on numerical results, the FI-EGR method was determined to be more effective than the AI-EGR method in reducing NOx emission because the high temperature region and the OH distribution region of the FI-EGR method were narrower. According to the results from the swirling flames, the reduction rates of EI NO X for the FI-EGR method and the AI-EGR were approximately 49% and 45% for an EGR ratio of 15% and 25%, respectively.

In this study, the CH4/air lean-rich combustion system with exhaust gas recirculation (EGR) was investigated to explore the potential for lowering pollutant emissions. To achieve this purpose, experiments of lean-rich combustion system with EGR were conducted to measure the changes in the characteristics of the pollutant emission and flame shape with various equivalence ratios and EGR rates. Here, this study was applied to the fuel distribution ratio of 3:1 for the formation of the lean and rich flames. Additionally, the results were compared with CH4/air lean premixed combustion system. The results show that flame shape of lean-rich combustion system was determined by lean and rich equivalence ratios (ΦL and ΦR) and stratified flame was formed with increasing ΦR. According to the pollutant emission characteristics based on experimental results, the NOx and CO emission index (EINOx and EICO) decreased with increasing EGR rate. Especially, in the range needed to form a stable flame, the reduction rates of EINOx and EICO were approximately 47% and 48% for an EGR rate of 25%, global equivalence ratio of 0.85 and ΦL of 0.80 compared with lean premixed combustion system (Φ = 0.78).

This study presents fundamental research on the development of a new boiler that is expected to have a higher efficiency and lower emissions than existing boilers. The thermodynamic efficiency of exhaust gas recirculation-condensed water recirculation-waste heat recovery condensing boilers (EGR-CWR-WHR CB) was calculated using thermodynamic analysis and was compared with other boilers. The results show the possibility of obtaining a high efficiency when the temperature of the exhaust gas is controlled within 50–60 °C because water in the exhaust gas is condensed within this temperature range. In addition, the enthalpy emitted by the exhaust gas for the new boiler is smaller because the amount of condensed water is increased by the high dew-point temperature and the low exhaust gas temperature. Thus, the new boiler can obtain a higher efficiency than can older boilers. The efficiency of the EGR-CWR-WHR CB proposed in this study is 93.91%, which is 7.04% higher than that of existing CB that is currently used frequently.

The experiment was conducted to measure temperature and pressure around operating portable butane gas ranges with oversized cookwares. In this experiment, portable butane gas range with different safety equipment and two kinds of oversized cookware, each of which is made of aluminum alloy and rock, was used. As a result, temperature of the bottom of the butane and the pressure of butane barrel tend to aligned with each other. Through this result, it is reasonable that a safety criteria can be decided based on the temperature of the bottom of butane. Especially, portable butane gas ranges are safely conducted under the condition of the temperature is under 50 degree and pressure is under 500 kPa, respectively, at the bottom of the butane barrel.

We examined the characteristics of NO x emission for CH4/air non-premixed flames using the exhaust gas recirculation(EGR) methods, which are the air-induced EGR(AI-EGR) and fuel-induced EGR(FI-EGR) methods. Our experimental results show that the NO x emission index(EI nox ) decreased with increasing EGR ratio. In the range needed to form a stable flame, the reduction rate of EInox for the FI-EGR method was approximately 29% when the EGR ratio was 20%, and the reduction rate for the AI-EGR method was approximately 28% with 25% of the EGR ratio. According to the flame structure based on numerical results, high temperature regions for the FI-EGR method were narrower and lower than those for the AI-EGR method at the same EGR ratio. Furthermore, based on the experimental results for swirl flames, the reduction rate of EI nox for the FI-EGR method was approximately 49% with 15% of the EGR ratio, while the maximum reduction rate for AI-EGR method was approximately 45% with 25% of the EGR ratio. Consequently, we verified that the FI-EGR method was more effective than the AI-EGR method in reducing NO x emission for non-premixed flames with EGR. We expect that the results of this study will provide fundamental information relating to hybrid combustion systems, which can be used in the design of combustion systems in the future.

The boiler of a premixed combustion system with EGR (exhaust gas recirculation) is investigated to explore the potential for increasing thermal efficiency and lowering pollutant emissions. To achieve this purpose, a thermodynamic analysis is performed to predict the effect of EGR on the thermodynamic efficiency for various equivalence ratios. Experiments of a preheated air condensing boiler with EGR were conducted to measure the changes in the thermal efficiency and the characteristics of the pollutant emission. Finally, a 1-D premixed code was calculated to understand the effect of the EGR method on the NO reduction mechanism. The results of the thermodynamic analysis show that the thermodynamic efficiency is not changed because the temperature and the amount of the exhaust gas are unchanged, even though the EGR method is implemented in the system. However, when the EGR method is used with an equivalence ratio near 1.00, it is experimentally verified that the thermal efficiency increases and the NO x concentration decreases. Based on the results from numerical calculations, it is shown that the NO production rates of N + O 2 ↔ NO + O and N + OH ↔ NO + H are remarkably changed due to the decrease in the flame temperature and the NO mole fraction is decreased.

The antioxidant and anti-inflammatory effects of active ingredients in cosmetics are very important. The effects are closely related to the prevention of skin aging. Among medicinal plants, Bletilla striata Reichenbach fil. has well-known pharmacological activity. Extracted samples were prepared using sequential fractionation of ethyl acetate, butanol, and water. The antioxidant effect of the fractions was confirmed by DPPH and ABTS+ radical scavenging. Among the various fractions of B. striata Reichenbach fil., ethyl acetate was associated with a reduction in nitric oxide production, which was induced by LPS (lipopolysaccharide) treatment in a dose-dependent manner. In addition, the production of iNOS (inducible nitric oxide synthase) and COX-2 (cyclooxygenase-2), which are upstream regulators of nitric oxide production, was also inhibited. Thus, the ethyl acetate fraction of B. striata Reichenbach fil. appears to be a potential active ingredient for use in cosmetics.

In order to estimate the combustion characteristics and the gas interchangeability for natural gas with various compositions per each production area, equivalent gas are using to replace natural gas. It is known that an equivalent gas has the same the heating value, the compression factor, the relative density, CO emission and the burning velocity as the original natural gas. However, it is not reported that the flame shape and thermal efficiency and NOx emission by real gas appliance. In this study, equivalent gas was examined the validation to replace natural gas. The CO emission the burning velocity and the flame temperature were reconfirmed, and the flame shape, the NOx emission and the thermal efficiency were numerically and experimentally investigated. As results, there was not a large difference between natural gas and equivalent gas. This result demonstrated that there was no problem using equivalent gas to replace natural gas.

This study investigated the characteristics of heat transfer and pressure drop for cross-flow heat exchanger of premixed combustion system. The premixed burner was in front of a heat exchanger, and the number of heat exchanger modules was changed to investigate the characteristics of NOx and CO emissions with various equivalence ratios. In addition, the effectiveness, entropy generation and pressure drop were calculated by various number of heat exchanger modules and the performance of heat exchanger was analyzed by the exergy loss.

This research was conducted to experimentally compare the emission characteristics and thermal efficiency of porous-media types of burners and to determine which types to use with a condensing boiler to be developed later. Three types of porous-media burners; metal fiber (MF), ceramic (CM) and stainless steel fin (SF) were used with a commercial heat exchanger and tested for various equivalence ratios and burner capacities. The MF burner had the lowest CO emissions of the three burner types, and the SF burner had the highest CO emissions. However, The MF burner had the highest NO x emission and thermal efficiency, and the SF burner had the lowest NO x emissions and thermal efficiency. In other words, the smaller the burner porosity was (porosity: SF x and CO emissions with respect to the Korean industrial standard and European norms, the most appropriate burner type for the condensing boiler is the MF burner. The optimal operating equivalence ratio was 0.80 for the range of experimental factors considered in this research.

In this study, an investigation into the gas interchangeability and combustion characteristics of various gas compositions for domestic appliances was performed. In order to suggest the appropriateness of gas interchangeability using the specific gravity (SG) and the Wobbe index (WI) values, combustion characteristics included incomplete combustion and flame lifting were measured and observed for the upper and lower limits using the gas-oven as a domestic partial-premixed type appliance and the condensing boiler as a domestic premixed type appliance. The flame was stable, and the CO and NOx concentrations increased when the WI and SG values increased. Specifically, the behavior of the flame lifting changed between WI values of 52.0 MJ/Nm3 and 53.0 MJ/Nm3. The CO and NOx concentrations of the reference gas were approximately 173 ppm and 74 ppm for the gas-oven and 175 ppm and 35 ppm for the boiler, respectively. Consequently, a WI value of 53.0 MJ/Nm3 can be considered the flame lifting limit as the lower limit for gas interchangeability. For the upper limit of gas interchangeability, the CO and NOx concentrations varied significantly with the type of burner.

In this research, a boiler in a premixed combustion system used to achieve exhaust gas recirculation was investigated as a way to achieve high thermal efficiencies and low pollutant emissions. The effects of various exhaust gas recirculation (EGR) ratios, equivalence ratios and boiler capacities on thermal efficiency, NOx and CO emissions and the flame behavior on the burner surface were examined both experimentally and numerically. The results of the experiments showed that when EGR was used, the NOx and CO concentrations decreased and the thermal efficiency increased. In the case of a 15% EGR ratio at an equivalence ratio of 0.90, NOx concentrations were found to be smaller than for the current operating condition of the boiler, and the thermal efficiency was approximately 4.7% higher. However, unlike NOx concentrations, although the EGR ratio was increased to 20% at an equivalence ratio of 0.90, the CO concentration was higher than in the current operating condition of the boiler. From the viewpoint of burner safety, the red glow on the burner surface was noticeably reduced when EGR was used. These results confirmed that the EGR method is advantageous from the standpoint of reducing emission concentrations and ensuring burner safety.

The purpose of this study is investigated on the combustion and the thermal characteristics of porous media burners which are many using for a condensing boiler recently. In addition, results of this study will be used the fundamental information to decide the burner type which will be applied to the future development of EGR(Exhaust gas recirculation) condensing boiler. Two flat type of burners made of a the metal fiber(MF) and the ceramic(CM) were selected and examined, experimentally. As experimental results, the emitted CO concentration of CM was higher than that of MF. However, the NO concentration of MF was higher than that of CM. The efficiencies of both burners were increased as increasing the burner capacity. While the efficiency of MF was higher than that of CM, regardless of the burner capacity. In the experimental range, MF is appropriated for the burner material and 0.8 of equivalence ratio is an optimal operation condition, regarding of the proportional control, the thermal efficiency and emitted NO and CO concentration based on the regulations of KS B standard and EN 677 standard.

The effect of the distance between the burner and the heat exchanger on the heat transfer characteristics and NO x and CO emission characteristics in a compact combustion system was studied. The premixed burner was installed in front of a heat exchanger, and the distance between the burner and the heat exchanger was varied from 30 mm to 50 mm to experimentally investigate the effect of distance for the counter flow and the parallel flow conditions. Distances in the type A, type B and type C heat exchangers were 30 mm, 40 mm and 50 mm, respectively. The results showed that NO x concentration increased at the same equivalence ratio for both flow conditions as the distance between the burner and the heat exchanger increased. On the other hand, CO emission increased for both flow conditions due to the quenching effect as the distance between the burner and the heat exchanger decreased. In the experimental range, the optimal equivalence ratio of heat exchanger type A was 0.75 to minimize pollutant emission. At this condition, the NO x and CO emissions were 32.3 ppm and 85.6 ppm, respectively, and the effectiveness was 0.797.

In this study, the heat transfer characteristics and NOx and CO emissions of a heat exchanger were investigated using a premixed burner. The experiments involved changing the distance between the burner and heat exchanger to 30, 40, and 50 mm with various equivalence ratios. The results showed that the NOx and CO emissions increased as the equivalence ratio was increased because the flame temperature increased, regardless of the distance between the burner and heat exchanger. In particular, the CO emission increased significantly as the distance between the burner and heat exchanger was decreased. The optimal equivalence ratio for the A-type heat exchanger (distance between the burner and heat exchanger: 30 cm) was 0.7 in the experimental range. In this case, the CO and NOx emissions were 94.5 ppm and 11.2 ppm, respectively, and the efficiency was 84.1%.

The objective of this study was to develop a new method for estimating gas interchangeability for 13A gas appliances. The three basic principles for the development of this method are as follows: 1) to derive the secondary interchangeability factor that represents the effect of gas composition, in addition to the major interchangeability factor, i.e., Wobbe index; 2) to test every type of and each maker's domestic gas appliances that are widely used in our country, particularly including premixed gas appliances; and 3) to develop a simple estimation method. On the basis of these principles, thirty representative gas appliances were tested, and as a result, a simple two-dimensional interchangeability diagram consisting of Wobbe index and relative density was developed. Unlike conventional methods for estimating interchangeability, this method can be applied to premixed gas appliances, which have a narrow stable flame range, and the interchangeability range of this method then becomes narrower than that of the conventional methods.

In this research, design factors for a heat exchanger and boiler were investigated using a simplified model of a heat exchanger and pilot condensing boiler, respectively. Specifications of each heat exchanger component (e.g., upper heat exchanger (UHE) and lower heat exchanger (LHE); coil heat exchanger (CHE); baffles) were investigated using a model apparatus, and the comprehensive performance of the pilot gas boiler was examined experimentally. The heating efficiency of the boiler developed was about 90% when using the optimal designed heat exchangers. Compared to a conventional Bunsen-type boiler, the heating efficiency was improved about 10%. Additionally, NO x and CO emissions were about 30 ppm and 160 ppm, respectively, based on a 0% O 2 basis at an equivalence ratio of 0.70, which is an appropriate operating condition. However, the pollutant emission of the boiler developed is satisfactory considering the emission performance of a condensing boiler, even though CO emission must be reduced.

This study experimentally examined a cylindrical multi-hole premixed burner for its potential use for a condensing gas boiler, which produces less NOx emissions and performs better. In this study, the hole diameters and the arrangement of a multi-hole burner were investigated using a flat burner model. The combustion characteristics for the flame stability as well as the NOx and CO emissions were examined using a cylindrical burner. For an optimal operating condition, the equivalence ratio for the cylindrical burner was between 0.70 and 0.75. For this condition, the turn-down ratio was 3:1 or higher, which was suitable for appropriate control of the boiler operation. The NOx and CO emissions were less than 40 ppm and less than 30 ppm, respectively, for a 0% O2 basis. The LPG and LNG were able to be used in this type of burner because there was no phenomenal difference in the stable combustion region between them.

23 vol % 분석되었다. Abstract: To determine the test gases for gas appliances of new gas group, the interrelation between gas interchangeability, including thermal efficiency, of 13A gas appliances and present 13A test gases was experimentally investigated. The test results show that the Wobbe indices in the case of incomplete combustion and the flame lifting limit gas for the new gas group are respectively 2% higher than the upper limit and 1% lower than the lower limit of the Wobbe index range. The most suitable composition of R gas is 96 mol% of methane and 4 mol% of propane; LNG could be also used as R gas. Further, analysis results showed that the hydrogen concentration of flash back limit gas could be lowered from 30 vol% to 23 vol%.

The effects of CO-tubes insertion on NO x (nitrogen oxides) and CO emissions from a compact heat exchanger were numerically simulated using a quasi one-dimensional premixed flame model, and the results were compared to experiments with a laboratory-scale heat exchanger and a commercial compact condensing boiler with a heat exchanger installed. The “CO-tubes” means that pre-cooling tubes were inserted between the burner and the main heat exchanger to reduce CO concentration. In the numerical results, the outlet concentration of NO increased as the distance between the burner and the CO-tubes was increased up to 3 cm. However, NO concentration was little affected by the CO-tubes when the distance was greater than 3 cm. Additionally, the concentration of CO reached a minimum at the distance of 3 cm. CO concentration increased when the distance from the burner to the CO-tubes was increased or decreased between 2 cm and 3 cm. These simulated results showed good agreement with the experimental results using a laboratory-scale heat exchanger. However, the maximum and minimum distances for NO and CO concentrations were different. When the CO-tubes were subsequently applied in a working commercial boiler, CO concentration was dramatically reduced by the CO-tubes and NO concentration was also slightly decreased.

The estimation method of the interchangeability in a partial premixed appliance about various compositions of natural gases using equivalent gases, experimentally. The results of the experiment in which equivalent gases were used compared with those obtained in experiments in which natural gases were used; Images of flames, lift-off limits, CO emissions, and incomplete combustion indices in KS standard for the domestic gas range were considered. From the comparison, it was observed that the length and color of the flame of the equivalent gases were almost the same as those of imported natural gases. Further, in the case of gases with Wobbe indices greater than 51 MJ/m

Biological activities such as anti-oxidative and anti-microbial of the Seungmakalgeuntang, a traditional prescription, were evaluated. The electron donating ability of water, ethanol, supercritical fluid and 1,3-butylene glycol extract of Seungmakalgeuntang showed more than 50% at a 100 ppm concentration. At a 1000 ppm concentration, the superoxide dismutase-like activities of ethanol and supercritical fluid extract of Seungmakalgeuntang showed less than 50%. xanthine oxidase inhibition effect of the supercritical fluid extract showed more than 70% at a 1,000 ppm concentration, which was higher than vitamin C. From the measurement on lipid oxidation, the Fe2+ chelating abilities of the supercritical fluid extract of Seungmakalgeuntang was more than 60% at a 100 ppm concentration. Also the Cu2+ chelating abilities of supercritical fluid extract Seungmkalgeuntangwas showed more than 60% at a 500 ppm concentration. Clear zones formed by sample against the human skinresident microflora such as Staphylococcus epidermidis, Staphylococcus aureus and Propionibacterium acne of ethanol and supercritical fluid extract of Seungmakalgeuntang showed the highest among all the extracts tested using a 4mg/disc. The minimum inhibitory concentration (MIC) against both S. epidermidis and S. aureus showed 2,500 ppm in the extract of the supercritical fluid.

We carried out numerical simulations to understand how CO2 dilution in either fuel or oxidizer stream changes the flame-vortex interactions in terms of hydrodynamic effects in CH4–air nonpremixed jet flames. The simulation used a time-dependent, axisymmetric computational model and a low Mach number approximation. Reaction rates were calculated from a two-step global reaction mechanism that considered six species. Studies were conducted with fixed initial velocities for three different cases of CO2 introduction: (1) without dilution, (2) dilution in a fuel stream, and (3) dilution in an oxidizer stream. A single vortex was generated by an axisymmetric jet driven of cold fuel, after a flame development was reached to quasi steady-state condition. The simulation shows that CO2 dilution in a fuel stream leads to a slightly increased vortex radius and more entrainment of surrounding fluids compared to the other dilution methods tested. Thus, dilution of CO2 in a fuel stream enhances the mixing inside a single vortex and increases the stretching of the flame surface. The vorticity transport equation budgets were examined to reveal the mechanisms of vortex formation in the presence of CO2. In the stage of vortex formation, vortex production due to baroclinic torque and vortex destruction due to volumetric expansion were found to be greater in the case of CO2 dilution in a fuel stream than in the other dilution cases. However, after vortex formation, there terms showed the opposite tendencies.

The combustion characteristics of a cyclone jet hybrid combustor using a combination of swirling premixed and jet diffusion flames were experimentally investigated to achieve high flame stability and low pollutant emissions. Two kinds of combustion modes were examined: the diffusion combustion (DC) mode, which consists of swirling air flow and jet diffusion flame, and the hybrid combustion (HC) mode, which consists of swirling premixed and jet diffusion flames. In the HC mode, the effects of fuel nozzle geometry on fuel–air mixing were investigated in terms of flame stability and pollutant emissions. The results showed that the HC mode can significantly reduce soot, CO, and NOx emissions in a stable flame region compared to the DC mode. However, CO emission in the HC mode increases drastically when overall equivalence ratios drop below 0.75. By modifying the fuel nozzle for the jet diffusion flame, it was found that increases in fuel–air mixing using the improved nozzle provide a stable flame region approximately twice as wide as that of the fuel nozzle using a single hole. In addition, a multi-hole fuel nozzle shows a NOx reduction of 55% compared to that of the DC mode.

One-dimensional modeling of CH4/air premixed flame was conducted to validate the heat loss model and investigate NOx formation characteristics in the postflame region. The predicted temperature and NO concentration were compared to experimental data and previous heat loss model results using a constant gradient of temperature (100 K/cm). The following conclusions were drawn. In the heat loss model using steady-state heat transfer equation, the numerical results using the effective heat loss coefficient (heff) of 1.0 W/m 2 K were in very good agreement with the experiments in terms of temperature and NO concentration. On the other hand, the calculated values using the constant gradient of temperature (100 K/cm) were lower than that in the experiments. Although the effects of heat loss suppress NO production near the flame region, a significant difference in NO concentration was not found compared to that under adiabatic conditions. In the postflame region, however, there were considerable differences in NO emission index as well as the contribution of NO formation mechanisms. In particular, in the range of 0.8

To clarify the effect of chemical structure of Dimethyl ether(DME) on NOx formation in nonpremixed counterflow flame, DME flame was investigated numerically to compare the flame structures and NOx emissions with C2H6 and Mixed-fuel. Numerically, the governing equations were solved using the Oppdif code coupled with CHEMKIN package, and DME flames were calculated by Kaiser’s mechanism, while the C2H6 flames and Mixed-fuel flames were calculated by the C3 mechanism. These mechanisms were combined with the modified Miller-Bowman mechanism for the analysis of NOx. Numerical results of nonpremixed counterflow flames show that the EINO of DME nonpremixed flame is low as much as 50 % of the C2H6 nonpremixed flame. The cause of EINO reduction is attributed mainly to the characteristics of partial premixed flame due to the existence of oxygen atom in DME and partly to the O-C bond in DME, instead of C-C bond in hydrocarbon fuels.

The NOx emission characteristics of dimethyl ether (DME) in laminar co-axial jet and counterflow non-premixed flames were investigated using experimental and numerical approaches, respectively. The flame structure and NOx emissions of DME were compared to those of C2H6, which has equivalent methyl structures but lacks an oxygen atom. Experimental results showed that, in the co-axial jet case, the combustion of DME had the characteristics of a partial premixed flame. Additionally, it had a shorter flame and lower NOx emissions compared to the C2H6 flame. It is thus concluded that the major cause of low NOx emissions from DME co-axial jet flames may be the short flame length because of the lower stoichiometric air/fuel ratio. The activation of reburning NO chemistry because of the characteristics of the partially premixed flame may also play a role. The computational results of the DME counterflow non-premixed flame revealed that the EINO decreased by approximately 50% relative to that of the C2H6 flame. Al...