• 한국추진공학회지
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• 제25권6호
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• pp.45-52
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• 2021

본 연구에서는 액체 추진제 소형로켓엔진의 개발을 위한 선행연구로 연료과농 조건의 기체메탄-기체산소 연소시험 결과를 제시한다. 다양한 당량비에 대한 연소특성을 비교하기 위해 산소 공급 유량을 12 g/s로 설정하고 메탄 공급 유량을 변화시켰다. 시험 결과, 연소시험 중 형성되는 정상상태 특성속도가 후반에서 급작스럽게 증가하는 현상이 관측되었으며, 그 변화량은 당량비에 비례하여 커지는 경향을 확인할 수 있었다. 이를 바탕으로 특성속도의 변이특성에 종속하는 당량비 구간을 총 3가지 연소 범주로 구분하였다.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2004년도 제29회 KOSCI SYMPOSIUM 논문집
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• pp.41-45
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• 2004

A dust injection system was developed for the lime calcining rotary kiln for the coke dust from the coke dry quenching(CDQ) facility to be used as a fuel. The CDQ dust was injected with the gaseous fuel through the hole in the burner. In order to prevent the spot heating large particles should be removed from dust and dust should be injected as fast as possible so that particle combustion lasts as long as possible without precipitation. This is especially necessary when dust is burned together with gaseous fuel because the gaseous fuel can not go so far and in addition dust combustion aggravates hot spot heating. In this research a rotation drum screen was used to remove particles with diameter larger than 4mm and dust injection speed was 40m/sec. And the burner was adjusted not to use swirl that hinders flame go far away. With these measures scale generation iside the kiln could be reduced to be negligible and in addition NOx emission could be reduced from 150ppm to 20ppm. The fuel reduction was about 85Mcal/T-lime.

• 천문학회보
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• 제40권1호
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• pp.48.4-49
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• 2015

Stellar spiral arms and magnetic fields in disk galaxies are important in the formation of gaseous structures such as spurs/feathers and wiggles as well as in angular momentum transport between stars and gas. We present our recent results of global magnetohydrodynamic simulations to study nonlinear responses of self-gravitating and magnetized gas to an imposed stellar spiral potential. We vary the arm strength, the arm pattern speed, and magnetic field strength to explore various galactic situations. Magnetic fields not only reduce the peak density of galactic spiral shocks but also make angular momentum transport more efficient via magnetic pressure and tension forces. The extent and shapes of gaseous arms as well as the radial mass drift rate depend rather sensitively on the magnetic field strength. The wiggle instability apparent in unmagnetized models is suppressed with increasing magnetic field strength, while magnetic fields promote the development of magneto-Jeans instability of the arms and magnetic islands in between arms. We quantify the angular momentum transport by spiral shocks, focusing on the effects of magnetic fields. We also present physical interpretations of our numerical results and discuss astronomical implications of our findings.

• 한국대기환경학회지
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• 제29권5호
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• pp.634-641
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• 2013

Condensing species behaviour downstream of a combustor was discussed with particle size distribution in this study. The effects of operating conditions in a biomass combustion facility, i.e. concentration of condensing species, temperature gradient, residence time and injection of adsorbents, on particle size distribution were investigated. Pyroligneous liquid which was completely vaporized at the temperature higher than $350^{\circ}C$ was used as a representative of condensing gaseous species. We found that particle size downstream of a combustor increased with increasing heating temperature (i.e. concentration of condensing species) and residence time. However, temperature gradient was not an important factor to control the particle size. The addition of $SiO_2$ precursor as an adsorbent could effectively prevent the particle formation by adsorbing condensing gaseous species on $SiO_2$ particles, and increased the particle size up to 300 nm, resulting in increasing particle removal efficiency in a conventional air pollution control device.

• Bulletin of the Korean Chemical Society
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• 제29권8호
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• pp.1525-1532
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• 2008

An instrument was developed for the simultaneous determination of gas- and aerosol-phase nitrous acid (HONO). Gaseous HONO (HONO(g)) was sampled by a diffusion scrubber and particulate nitrite ($NO_2\;^-$(p)) was collected by a particle growth chamber. The collected samples were analyzed in time-sharing manner, based on the peroxynitrite-induced luminol chemiluminescence. The automated system was found to be sensitive with 13 pptv of detection limit, fast with 4 min. of sampling frequency, and simple and affordable to construct and operate. The system was optimized by adjusting the experimental parameters. The system was applied to the field measurement of gas- and particle-phase HONO during the springtime of 2004 in Gwangju, South Korea. HONO(g) concentrations varied diurnally from 200 pptv around 3 P.M. to 800 pptv at 5 A.M. The variation of $NO_2\;^-$(p) was not significant with the maximum of 240 pptv at 11 P.M. and the minimum of 170 pptv at 4 P.M., not displaying distinct characteristics.

• 한국대기환경학회지
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• 제10권1호
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• pp.24-31
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• 1994

Hourly variation of gaseous nitrous acid( HNO$_2$) concentration in Seoul air was monitored from Jan. 11 to SeP. 12, Nitrous acid concentration was determined by DS/IC over nine months of observation, HNO$_2$ range from 0.04 ppb to 5.5 ppb. Gor-tex tube as gaseous HNO$_2$generator in this study is thought to be more convenient and reproducible device than previous generator. As a result of NaOH instead of Na$_2$ CO$_3$/NaHCO$_3$ solution as the IC eluent, we could obtain more stable baseline. The concentration of the NaOH eluent was 15 mM . The limit of detection(3$\sigma$) of the liquid- Phase and gas phase nitrous acid of this method are 1.1ng/$m\ell$ , 0.04 n $\ell$ / $\ell$, respectively. The precisions evaluated by 10 replicate analysis of standard solution and standard gas generated are $\pm$1.59, $\pm$2. 89% RSD, respectively. Due to the lack of standard material for air, direct assessment of the accuracy was not possible. This study was applied to the analysis of Seoul ambient air and their results are reported herein.

• 한국대기환경학회지
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• 제14권4호
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• pp.281-292
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• 1998

Ambient concentrations of gaseous, particulate phase ionic species, and VOCs (volatile organic compounds) were measured at two monitoring sites in the City of Ulsan during August 1997: one in industrial area and the other in downtown area. At each site, a three- stage filter pack sampler was used to collect fine particles and gaseous species, and air for VOC analysis was collected in stainless steel canisters. Concentrations of the ionic species at both sites were similar to each other. The VOC concentrations at the industrial site were approximately twice higher than those at the downtown site. This might be mainly due to the release of VOCs from the petrochemical industries. Daily variations of VOC concentrations at the industrial site were higher than that at the downtown site. This might be explained by the fact that emissions from industries were more irregular than those in downtown. The VOC concentrations in downtown were affected by both the local emissions and the emission from the petrochemical industries. The concentrations of selected hazardous organic components (HAPs) at the industrial site were similar to those of Yocheon industrial area but slightly higher than other cites and industrial areas, while those at the downtown site were comparable to those in other urban areas.

• 한국대기환경학회지
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• 제26권2호
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• pp.202-218
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• 2010

It is well known that the atmospheric inorganic aerosol has the hysteresis phenomena depending on the history of relative humidity. However, the current computational researches have assumed that the physical/chemical state of atmospheric aerosol is only determined by a branch of hysteresis, efflorescence or deliquescence. In this work, we applied the MATLAB-based UHAEROm thermodynamics module to simulate the dynamic interaction between gaseous species $NH_3$ and $HNO_3$, and the two mono-disperse particulate populations in the course of efflorescence and deliquescence, respectively. We conducted the 10 case studies considering the particulate phase with the atmospherically prevailing chemical composition and found that the final states of the particles are determined through the qualitatively five different trajectories by the dynamic interaction between gaseous and two different kinds of particulates. As a result, we show that the coexistence of meta-stable and stable particles drives the different physical/chemical destination comparing with the ones generated from the solitary efflorescence or deliquescence branch.

• 한국대기환경학회지
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• 제24권6호
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• pp.641-648
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• 2008

A plate-type dielectric barrier discharge (DBD) reactor was designed and tested for removal of gaseous toluene. The DBD reactor consisted of 9 parallel plate electrodes, four of which were grounded. An AC voltage of rectangular waveform ($5{\sim}8.5kV$, $60{\sim}1,000Hz$), was applied to the other five electrodes. The gaseous toluene passed through the DBD reactor and its concentration was measured by a real-time gas analyzer. The carbon monoxide (CO) and carbon dioxide ($CO_2$) which were produced by decomposition of toluene in the DBD reactor, were sampled and analyzed by a micro gas chromatography. The maximum toluene removal efficiency was 51.4%.

• Environmental Analysis Health and Toxicology
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• 제22권2호통권57호
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• pp.177-184
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• 2007

Gaseous organochlorine pesticides (OCPs : heptachlor epoxide, p, p'-DDE, ${\gamma}-HCH,\;{\alpha}-chlordane,\;{\gamma}-chlordane$ and trans-nonachlor) concentration was measured using PUF high volume sampler from June, 2000 to June, 2002 in the semi-rural atmosphere. The OCPs concentration in atmosphere, which is estimated by the slope (m) of Clausius-Clapeyron equation and phase-transition energy $({\Delta}H)$, was influenced by revolatilization from environmental matrix (soil, water and tree leaves) and a long range transportation of air mass. But the former affected OCPs concentration more than the latter. The degradation rate constants (k) of OCPs calculated using multiple regression analysis and revised standard temperature method were in good agreement each other. The value of k of ${\gamma}-HCH$ was very low as -0.0007, but the range of k of other components were $-0.00l8{\sim}-0.0038$. The half-life $({\tau})$ which was calculated by k of ${\gamma}-HCH$ was 2.6 years-the longest one, but that of heptachlor epoxide was in 0.5 year-the shortest one. $({\tau})\;of\;{\alpha}-chlordane,\;{\gamma}-chlordane$ and trans-nonachlor in technical chlordane was 1.0, 1.1 and 0.7 year respectively.