• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2977-2983
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• 2008

The combustion characteristics of a partially premixed flame in a dump combustor were studied to determine the effects of hydrogen enrichment in propane. Bluff-body was used for flame stabilization. Fuel mixtures containing a hydrogen mole fraction ranging from 0.1 to 0.5 were burnt at ambient pressure within a quartz chamber. Tests were carried out keeping the total reactant flow rate by adjusting the fuel and air flow rates. The fluctuations of pressure were measured by piezoelectric pressure sensor. The instantaneous flame structure and OH chemiluminescence images were described by High-speed Intensified Charged Coupled Device (HICCD) camera and Intensified Charged Coupled Device (ICCD) camera. The present results show that hydrogen enrichment in fuel changed the location of primary reaction zone from inner recirculation zone to turbulent shear layer and pressure signal. The reason is that chemical aspects take precedence over flow aspects in the hydrogen-enriched flame.

• Journal of dental hygiene science
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• v.10 no.2
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• pp.101-107
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• 2010

The purpose of this study was to analysis know the important oral environmental factors which affect halitosis components of the adult in order to provide basic data for halitosis prevention and establish a device to eliminate halitosis efficiently. The 97 adults who visited at the Dental Clinic in Metropolis (M=68, F=30) participated in this study that performed from March in 2009 to in 2010. The obtained results through items as caries status, periodontal status, salivary flow, the viscosity, pH, Snyder test, plaque deposit, tongue plaque and halitosis check were as followings. The average shame of halitosis components appeared at hydrogen sulfide 36.71 ppb methyl mercaptan 31.46ppb dimethyl sulfide 54.33 ppb and Ammonia 22.60 ppm. The normality and the detection comparative result dimethyl sulfide above reverse appeared highly at 46.9%, ammonia appeared highly at 52%. According to the Hydrogen sulfide level was a high relationship among age, CPI, tongue coat status, DMFT index which were statistically significant (p<0.05). According to the quantity of hydrogen sulfide level there was relationship where tongue coat status Saliva flow rate considers statistically(p<0.05). The quantity of methyl mercaptan level there was relationship where Dimethyl sulfide level, tongue coat status, Saliva flow rate considers statistically(p<0.05). The quantity of Dimethyl sulfide level there was relationship where Hydrogen sulfide level, ammonia level, tongue coat status, Saliva pH and Saliva flow rate considers statistically(p<0.05). Ammonia level there was relationship where Methyl mercaptan level, CPI, and Saliva flow rate considers statistically(p<0.05).

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.10
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• pp.1393-1400
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• 2003

Ignition of hydrogen and oxygen in the "third limit" is theoretically investigated in the stagnation point flow with activation energy asymptotics. With the steady-state approximations of H, OH, O and HO$_2$, a two-step reduced kinetic mechanism is derived for the regime lower than the crossover temperature T$_{c}$ at which the rates of production and consumption of all radicals are equal. Appropriate scaling of Damkohler number successfully provides the explicit relationship between pressure, temperature and strain rate at ignition. It is shown that, compared with those for the counterflow, ignition temperatures for the stagnation point flow are considerably increased with increasing the system pressure. This is because ignition in the "third limit" is characterized by the production of reduction of $H_2O$$_2$, which is reduced by wall effect. Strain rate substantially affects ignition temperature because key reaction rates of $H_2O$$_2$ are comparably with its transport rate, while the mixture temperature and the hydrogen composition do not significantly affect ignition temperature.e.

• Transactions of the Korean hydrogen and new energy society
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• v.10 no.1
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• pp.9-17
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• 1999

The hydriding and dehydriding kinetics were studied for a Mg-25wt.%Ni mixture which has the most excellent hydrogen-storage characteristics among many mechanically-alloyed mixtures. The hydriding and dehydriding rates were measured and the rate-controlling steps were determined by comparing the hydriding and dehydriding rates with the theoretical rate equations. The rate-controlling step in the hydriding reaction is the Knudsen flow and the ordinary gaseous diffusion of hydrogen molecules through interparticle channels, cracks, etc. in the various ranges of weight percentage of absorbed hydrogen $H_a$ below $H_a$=4.0. In the $H_a$ range 4.0 < $H_a{\leq}4.25$, the diffusion of hydrogen atoms through the growing hydride layer is considered the rate-controlling step. The rate-controlling step in the dehydriding reaction is the Knudsen flow and the ordinary gaseous diffusion of hydrogen molecules for all the ranges of weight percentage of desorbed hydrogen $H_d$.

• Journal of the Korean Ceramic Society
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• v.52 no.5
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• pp.325-330
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• 2015

Performance of solid oxide fuel cells (SOFCs), in comparison with that under hydrogen fuel, were investigated under direct internal reforming conditions. Anode supported cells were fabricated with an Ni+YSZ anode, YSZ electrolyte, and LSM+YSZ cathode for the present work. Measurements of I-V curves and impedance were conducted with S/C (steam to carbon) ratio of ~ 2 at $800^{\circ}C$. The outlet gas was analyzed using gas chromatography under open circuit condition; the methane conversion rate was calculated and found to be ~ 90% in the case of low flow rate of methane and steam. Power density values were comparable for both cases (hydrogen fuel and internal steam reforming of methane), and in the latter case the cell performance was improved, with a decrease in the flow rate of methane with steam, because of the higher conversion rate. The present work indicates that the short-term performance of SOFCs with conventional Ni+YSZ anodes, in comparison with that under hydrogen fuel, is acceptable under internal reforming condition with the optimized fuel flow rate and S/C ratio.

• Clean Technology
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• v.28 no.3
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• pp.238-248
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• 2022

The world is striving to transition to a carbon-neutral society. It is expected that using hydrogen instead of hydrocarbon fuel will contribute to this carbon neutrality. However, there is a need for combustion technology that controls the increased NOx emissions caused by hydrogen co-firing. Flameless combustion is one of the alternative technologies that resolves this problem. In this study, a numerical analysis was performed using the 1D opposed-flow diffusion flame model of Chemkin to analyze the characteristics of flameless combustion and the chemical reaction of methane-hydrogen fuel according to its hydrogen content and flue gas recirculation rate. In methane combustion, as the recirculation rate (K_v) increased, the temperature and heat release rate decreased due to an increase in inert gases. Also, increasing K_v from 2 to 3 achieved flameless combustion in which there was no endothermic region of heat release and the region of maximum heat release rate merged into one. In H₂ 100% at K_v 3, flameless combustion was achieved in terms of heat release, but it was difficult to determine whether flameless combustion was achieved in terms of flame structure. However, since the NOx formation of hydrogen flameless combustion was predicted to be similar to that of methane flameless combustion, complex considerations of flame structure, heat release, and NOx formation are needed to define hydrogen flameless combustion.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.111-114
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• 2009

A catalyst ignitor of small thrust engine using hydrogen peroxide and kerosene was designed and fabricated, which confirmed mass flow rate for design pressure through the water cold-flow test in this study. In order to investigate ignition performance, it was changed that mixture ratio for kerosene mass flow rate in a position which heat of hydrogen peroxide decomposition comes to a steady state. And we confirmed stable ignition property in a wide range of mixture ratio.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.227-230
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• 2006

The method of mass flow rate measurement using a critical nozzle is well established in the flow satisfying ideal gas law. However, in the case of measuring high-pressure gas flow, the current method shows invalid discharge coefficient because the flow does not follow ideal gas law. Therefore an appropriate equation of state considering real gas effects should be applied into the method. The present computational study has been performed to give an understanding of the physics of a critical nozzle flow for high-pressure hydrogen gas and find a way for the exact mass flow prediction. The two-dimensional, axisymmetric, compressible Navier-Stokes equations are computed using a fully implicit finite volume method. The real gas effects are considered in the calculation of discharge coefficient as well as in the computation. The computational results are compared with the previous experimental data and predict well the measured mass flow rates. It has been found that the discharge coefficient for high-pressure hydrogen gas can be corrected properly adopting the real gas effects.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.37-40
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• 2009

This study was performed to design of $H_2O_2$/Kerosene catalyst ignition injector and cold flow test to measure the mass flow rate and spray angle. Mass flow rate and spray angle were measured by designed injector through cold flow test. Result of test kerosene mass flow rate was measured 12.88 g/s and 40 deg of spray angle at pressure drop 3 bar as same as design point. And hydrogen peroxide was measured 94.39 g/s at pressure drop 1 bar smaller than design point.

• Korean Journal of Materials Research
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• v.23 no.5
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• pp.260-265
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• 2013

Silicon nanoparticle is a promising material for electronic devices, photovoltaics, and biological applications. Here, we synthesize silicon nanoparticles via $CO_2$ laser pyrolysis and study the hydrogen flow effects on the characteristics of silicon nanoparticles using high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and UV-Vis-NIR spectrophotometry. In $CO_2$ laser pyrolysis, used to synthesize the silicon nanoparticles, the wavelength of the $CO_2$ laser matches the absorption cross section of silane. Silane absorbs the $CO_2$ laser energy at a wavelength of $10.6{\mu}m$. Therefore, the laser excites silane, dissociating it to Si radical. Finally, nucleation and growth of the Si radicals generates various silicon nanoparticle. In addition, researchers can introduce hydrogen gas into silane to control the characteristics of silicon nanoparticles. Changing the hydrogen flow rate affects the nanoparticle size and crystallinity of silicon nanoparticles. Specifically, a high hydrogen flow rate produces small silicon nanoparticles and induces low crystallinity. We attribute these characteristics to the low density of the Si precursor, high hydrogen passivation probability on the surface of the silicon nanoparticles, and low reaction temperature during the synthesis.