• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.27 no.5
• /
• pp.596-603
• /
• 2003

Present study has been conducted to see the relative effects of adding N: to fuel-side and air-side on flame structure, soot formation and NOx emissions. Experiments were carried out to ascertain to what degree chemical kinetics and/or molecular transport effects can explain the differences in soot formation and NOx emission by studying laminar diffusion flames. Direct photograph was taken to see the flame structure. CARS techniques was used to get the flame temperature profiles. And spatial distribution of soot could be obtained by PLII method. CHEMKIN code was also used to estimate the global residence time to predict NOx emissions at each condition. Results from these studies indicate that fuel-side dilution is more effective than air-side dilution in view of NOx emissions. However, air-side dilution shows greater effectiveness over fuel-side dilution in soot formation. And turbulent mixing and heat transfer problems were thought to be considered in practical applications.

• Proceedings of the Korea Air Pollution Research Association Conference
• /
• 2002.04a
• /
• pp.249-250
• /
• 2002

입자상 물질은 호흡에 의해 폐 깊숙이 침착되어 인체에 피해를 줄 수 있다 같은 질량의 거대 및 미세 입자가 있을 경우, 입자의 크기가 작아짐에 따라 비표면적이 급속히 커지기 때문에 입자가 유해 중금속 성분을 함유하고 있을 경우 그 중금속의 농축 정도가 크다. 지하철 역사는 사람들이 가장 많이 생활하는 지하 공간중의 하나이며, 유동인구가 많아 입자상 물질의 발생이 심한 지역으로 외기에 비해 희석, 화산 공간이 크지 않기 때문에 역사 내 유해 환경 오염 물질의 영향과 관리 대책에 대한 연구가 진행되고 있다. (중략)

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.28 no.1
• /
• pp.1-8
• /
• 2004

An study has been performed with axisymmetric coflow diffusion flames to investigate the influence of air-side fuel side dilution and initial preheated temperature on the soot formation in methan/air flames. Soot quantities are determined by using PLII(Planar Laser Induced Incandescence), such a $C_2$H$_2$ major species(CH$_4$, $O_2$, $N_2$) and temperature are simulated by chemkin code. The numerical analysis was performed with transport properties and detailed reaction mechanisms m axisymmetric coflow diffusion flames. The study of how flame temperature and $N_2$ dilution of air and fuel side influence the soot concentrations is focused. Soot concentrations results on PLII show that preheated temperature contributes to an increase in the soot volume fraction, and soot formation Is more productive to air side dilution than to fuel side dilution. $C_2$H$_2$ concentrations have a similar tendency to soot concentrations.

• Korean Chemical Engineering Research
• /
• v.51 no.5
• /
• pp.622-627
• /
• 2013

Colloidal silica is used in various industrial products such as chemical mechanical polishing slurry for planarization of silicon and sapphire wafer, organic-inorganic hybrid coatings, binder of investment casting, etc. An accurate determination of particle size and dispersion stability of silica sol is demanded because it has a strong influence on surface of wafer, film of coatings or bulks having mechanical, chemical and optical properties. The study herein is discussed on the effect of measurement results of average particle size, sol viscosity and electrophoretic mobility of particle according to the volume fraction of eight types of silica sol with different size and surface properties of silica particles which are presented by the manufacturer. The measured particle size and the mobility of these sol were changed by volume fraction or particle size due to highly active surface of silica particle and change of concentration of counter ion by dilution of silica sol. While in case the measured sizes of small particles less than 60 nm are increased with increasing volume fraction, the measured sizes of larger particles than 60 nm are slightly decreased. The mobility of small particle such as 12 nm are decreased with increase of viscosity. However, the mobility of 100 nm particles under 0.048 volume fraction are increased with increasing volume fraction and then decreased over higher volume fraction.

• 한국신재생에너지학회:학술대회논문집
• /
• 2007.06a
• /
• pp.775-778
• /
• 2007

The present study numerically investigate the detailed structure of the syngas diffusion flames. In order to realistically represent the turbulence-chemistry interaction, the transient flamelet model has been applied to simulate the combustion processes and $NO_X$ formation in the syngas turbulent nonpremixed flames. The single mixture fraction formulation is extended to account for the effects of the secondary inlet mixture. Computations are the wide range of syngas compositions and oxidizer dilutions. Based on numerical results, the detailed discussion has been made for the effects of syngas composition and oxidizer dilution on the structure of the syngas-air and syngas-oxygen turbulent nonpremixed flames.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.15 no.3
• /
• pp.166-173
• /
• 2007

A numerical study was conducted to have the effect of $CO_2$ addition to fuel on the chemical reaction mechanism with the change of the initial concentration of $CO_2$ and the axial velocity gradient. From this study, it was found that there were two serious effects of $CO_2$ addition on a non-premixed flame ; a diluent effect by the reactive species reduction and chemical effect of the breakdown of $CO_2$ by the third-body collision and thermal dissociation. Especially, the chemical effect was serious at the lower velocity gradient of the axial flow. It was certain that the mole fraction profile of $CO_2$ was deflected and CO was increased with the initial concentration of $CO_2$. It was also ascertained that the breakdown of $CO_2$ would cause the increasing of CO mole fraction at the reaction region. It was also found that the addition of $CO_2$ did not alter the basic skeleton of $H_2-O_2$ reaction mechanism, but contributed to the formation and destruction of hydrocarbon products such as HCO. The conversion of CO was also suppressed and $CO_2$ played a role of a dilution in the reaction zone at the higher axial velocity gradient.

• Journal of agricultural medicine and community health
• /
• v.18 no.2
• /
• pp.131-140
• /
• 1993

This study was conducted to examine the levels of mercury in tissue of Carassius carassius collected at five areas(Andong, Sangju, Waekwan, Gangjung and Gaejin) in Nakdong river from February to March, 1993. The contents of total and organic mercury were determined by methods of Gold amalgam and Selective atomic absorption with mercury analyzer(Model SP-3A). The total mercury contents in muscle were $0.148{\pm}0.0646$ ppm by the Gold amalgam, and $0.113{\pm}0.0345$ ppm by the Selective atomic absorption, but in all parts of Carassius carassius were $0.342{\pm}0.4235$ ppm and $0.240{\pm}0.2974$ ppm respectively. These two methods were extremely high correlated(r=0.9812, p<0.001). The mean value of total and organic mercury by the two methods was high in the order of bone>fin>muscle, respectively, and the proportion of organic mercury to the total was 69.0%. Mean value of total and organic mercury in the muscle was the highest at Wakeman located in middle basin of Nakdong river, and in the bone and fin was the highest at Andong dam located in upper basin. According to sizes and parts of fish, the concentration of mercury was the highest in the muscle of 15-19 cm group, the highest in the bone of 10-14 cm group and in the fin of 20-24 cm group.

• Korean Journal of Materials Research
• /
• v.8 no.6
• /
• pp.513-519
• /
• 1998

Zr-Si binary alloys containing 0.01 to O.lwt.%Si were prepared to investigate the effect of Si on the corrosion behavior of Zr. Corrosion test was performed in pure water at 36$0^{\circ}C$ under a pressure of 2660psi for 100days. The alloys containing 0.01 wt. % and 0.05wt. %Si had the black and uniform oxide film and didn't show the transition of corrosion rate. However. the alloys containing O.lwt.%Si had white oxide film and showed the trasition of corrosion rate at 70 days corrosion test. The weight gain increased with the increasing Si content from 0.01 to 0.1 wt.%. The variation of Si contents had no effect on changing the oxide structure but had significant effect on the electrical resistivity of oxide. The electrical resistivity decreased with increasing Si content. The fraction of precipitates in the Zr-Si binary alloys. identified as tetragonal $Zr_{3}$Si increased with increasing Si content. The increase of the volume fraction of precipitates is thought to be responsible for the increase of weight gain due to short circuit effect of precipitate.

• Journal of the Korean Ceramic Society
• /
• v.41 no.3
• /
• pp.235-242
• /
• 2004

Si, NH$_4$Cl, NaN$_3$, NaCl, $N_2$ were used as raw materials for preparation of $\alpha$-Si$_3$N$_4$ powder. NH$_4$Cl and NaN$_3$ were used as additives, and NaCl was used as a diluent. Initial $N_2$ gas pressure in the SHS reactor was 60 atm. In preparation of $\alpha$-Si$_3$N$_4$, the reactivity and the properties of the products were examined with the various kinds of additives and the content of diluent. At first, the optimum reaction system for the preparation of $\alpha$-Si$_3$N$_4$ is examined and then the optimum composition was examined in the optimum reaction system. The optimum reaction system was Si-$N_2$-additive(NH$_4$Cl+NaN$_3$)-diluent(NaCl) and the optimum composition was 38 wt%Si+50 wt%(NH$_4$Cl+NaN$_3$)+12 wt%NaCl. The maximum fraction of $\alpha$-phase of Si$_3$N$_4$ produced in this condition was 96.5 wt% and the shape of the $\alpha$-Si$_3$N$_4$ produced in this condition was an irregular fiber with a length of 10 ${\mu}{\textrm}{m}$ and a diameter of 1 ${\mu}{\textrm}{m}$.

• KSBB Journal
• /
• v.10 no.3
• /
• pp.241-248
• /
• 1995

For the treatment of poorly biodegradable polyvinyl alcohol(PVA) in dye-processing wastewater, immobilized microbial beads were prepared by uslng agar-acrylamide method. PVA removal efficiency for the synthetic wastewater was 85% at the PVA volume loading rate of $3.1g/\ell$.day. In case of real desizing wastewater, PVA removal efficiency was 81.3% at the PVA volume loading rate of $3.25g/\ell$.day. In observation of cross section of immobilized bead passed 5 months with diameter of 2.4mm, the growth of cell was limited by the resistance of substrate and oxygen transfer for the inners region of more than 48% of bead radius from the surface. It was estimated that 70% of total removed PVA was degraded by the immobilized cells in the continuous immobilized reactor. Substrate utilization rate in the suspended reactor was decreased with increasing dilution rates above 0.083 hr-1, but that in the immobilized reactor was increased with increasing dilution rates up to 0.125hr-1. The substrate removal efficiency of immobilized reactor was much superior to that of suspended reactor with increasing dilution rates. Saturation constant of substrate utilization rate equation, Ks was $6.6 g PVA/\ell$, and maximum specific substrate utilization. k was 0.175g PVA/g cell.hr