• Journal of the Korean Society of Safety
• /
• v.25 no.2
• /
• pp.12-17
• /
• 2010

Numerical simulations were performed for the prediction of the flame structure during the interaction between hydrogen and hydrocarbon flames. A counterflow flow geometry was introduced to establish the interacting two flames. Methane was used as a representative hydrocarbon fuel in this study. A well-known numerical code for the counterflow flame, OPPDIF, was used for the simulations. The detailed chemistry was adopted to predict the flame structure reasonably. The interaction of two one-dimensional premixed flames established in counterflow burner was investigated with the global strain rate and velocity ratio. It was found that the maximum temperature located near the methane flame surface while the heat release rate of methane was lower than hydrogen flame. The flame thickness become narrow with increasing the velocity ratio while the global strain rate was fixed. The local strain rate and heat release rate at the methane flame surface were correlated with the global strain rate, while those at the hydrogen flame were not correlated with the global strain rate. However, the maximum temperature of the interacting flames was correlated with the global strain rate.

• 한국연소학회:학술대회논문집
• /
• 2014.11a
• /
• pp.147-148
• /
• 2014

This article describes an investigation of flame stability characteristics with various compositions of synthetic natural gas (SNG) in dual swirl combustor. The objective of this study is to investigate the flame stabilization, flame structure, fuel compatibility using chemiluminescence measurement in SNG with varying fuel compositions. As experimental conditions, hydrogen content was adjusted from 0 to 11%. Experimental results show that the addition of hydrogen has a major effect on flame behavior due to the higher burning rates associated with hydrogen consequently, The higher reaction activity of hydrogen has extended lean blow-off limit. Especially, DI flame limit has improved more 12.1%.

• Proceedings of the KSME Conference
• /
• 2004.04a
• /
• pp.1310-1315
• /
• 2004

The present study deals with the unique characteristics of hydrogen jet diffusion flames, such as split flames and reignition phenomenon. The split flames are composed of a small flamelet on the nozzle rim and a lifted main flame at downstream. When mass flow rates of fuel reach a critical point, a small-sized flamelet is found to remain in the vicinity of the nozzle exit and the flame reignition subsequent to blowout of main flame occurs repeatedly. In this study, the non-luminous hydrogen jet diffusion flames are visualized by using schlieren technique in order to analyze the combustion characteristics of hydrogen jet diffusion flames with focus on the flame reignition phenomenon.

• Journal of computational fluids engineering
• /
• v.9 no.1
• /
• pp.25-33
• /
• 2004

Flame onset and propagation within hydrogen premixed gas mixture are numerically investigated in an rectangular enclosure. A detailed chemistry for hydrogen reaction is applied to anticipate the thermochemical behavior of intermediate species appropriately. To facilitate computation, 10 species and 16 elementary reaction steps for hydrogen combustion are taken into account. On the basis of 30％ of hydrogen concentration in hydrogen-air mixture, the effects of position and quantity of ignition sources on the flame evolution are analyzed. From the simulation results, the methods to decrease the potential hazard caused by the flame propagation are suggested.

• Proceedings of the KSME Conference
• /
• 2003.11a
• /
• pp.350-355
• /
• 2003

Flame onset and propagation within hydrogen premixed gas mixture are numerically investigated in an rectangular enclosure. A detailed chemistry for hydrogen reaction is applied to anticipate the thermochemical behavior of intermediate species appropriately. To facilitate computation, 10 species and 16 elementary reaction steps for hydrogen combustion are taken into account. On the basis of 30 % of hydrogen concentration in hydrogen-air mixture, the effects of position and quantity of ignition sources on the flame evolution are analyzed. From the simulation results, the means that can lessen the possible hazard caused by flame propagation are suggested.

• Transactions of the Korean hydrogen and new energy society
• /
• v.19 no.4
• /
• pp.276-282
• /
• 2008

The effects of hydrogen enrichment to methane have been investigated with swirl-stabilized premixed hydrogen-enriched methane flame in a laboratory-scale pre-mixed combustor. The hydrogen-enriched methane fuel and air were mixed in a pre-mixer and introduced to the combustor through different degrees of swirl vanes. The flame characteristics were examined for different amount of hydrogen addition to the methane fuel and different swirl strengths. The hydrogen addition effects and swirl intensity on the combustion characteristics of pre-mixed methane flames were examined using micro-thermocouple, particle image velocity meter (PIV) and chemiluminescence techniques to provide information about flow field. The results show that the flame area increases at upstream of reaction zone because of increase in ignition energy from recirculation flow for increase in swirl intensity. The flame area is also increased at the downstream zone by recirculation flow because of increase in swirl intensity which results in higher centrifugal force. The higher combustibility of hydrogen makes reaction faster, raises the temperature of reaction zone and expands the reaction zone, consequently recirculation flow to reaction zone is reduced. The temperature of reaction zone increases with hydrogen addition even though the adiabatic flame temperature of the mixture gas decreases with increase in the amount of hydrogen addition in this experiment condition because the higher combustibility of hydrogen reduces the cooler recirculation flow to the reaction zone.

• Journal of the Korean Society of Combustion
• /
• v.9 no.4
• /
• pp.28-34
• /
• 2004

Numerical simulations of freely propagating flames burning $H_2/HCl/Air$ Air mixtures were performed at atmospheric pressure in order to understand the effect of hydrogen chloride on flame structures. The chemical and physical effects of hydrogen chloride on flame structures were observed. A chemical kinetic mechanism was developed, which involved 26 gas-phase species and 198 forward elementary reactions. Under several equivalence ratios the flame speeds were calculated and compared with those obtained from the experiments, the results of which were in good agreement. As hydrogen chloride as additive was added into $H_2/Air$ flame, the flame speed, radical concentration and NO production rate were decreased. The chemical effect of hydrogen chloride caused the reduction of radical concentration, and then the decrease of the net rate of NO production. It was found that the influence in the reduction of $EI_{NO}$ with the addition of hydrogen chloride was attributed more due to the chemical effect than the physical effect.

• Nuclear Engineering and Technology
• /
• v.54 no.1
• /
• pp.130-137
• /
• 2022

In the geological repository of radioactive nuclear waste, anaerobic corrosion can generate hydrogen, and may conservatively lead to the production of hydrogen-air layer. The accumulated hydrogen may cause a hazardous flame propagation resulting from any potential ignition sources. This study numerically investigates the processes of ignition and flame propagation in the layered mixture. Simple geometry was chosen to represent the geological repository, and reactive flow simulations were performed with different ignition power, energy, and locations. The simulation results revealed the effects of power and energy of ignition source, which were also analyzed theoretically. The mechanism of layered flame propagation was suggested, which includes three stages: propagation into the hydrogen area, downward propagation due to the product gas, and horizontal propagation along the top wall. To investigate the effect of the ignition source location, simulations with eight different positions were performed, and the boundary of hazardous ignition area was identified. The simulation results were also explained through scaling analysis. This study evaluates the potential risk of the accumulated hydrogen in geological repository, and illustrates the layered flame propagation in related ignition scenarios.

• 한국연소학회:학술대회논문집
• /
• 2000.12a
• /
• pp.47-58
• /
• 2000

The relationship among the flame radiation, NOx emissions, residence time, and global strain rate are examined for turbulent non-premixed jet flames with wide variations in coaxial air conditions. Measurements of NOx emission, flame geometry and flame radiation were made to explain the NOx emission scaling based on global parameters such as flame residence time, global strain rate, and radiant fraction. The overall 1/2-power scaling is observed in coaxial air flames, irrespective of coaxial air conditions, but the degree of deviation from the l/2-slope curve in each case differs from one another. From the comparison between the results of pure hydrogen flames and those of helium diluted hydrogen flames, it is observed that flame radiation plays a significant role in pure hydrogen flames with coaxial air and the deviation from 1/2-power scaling may be explained in two reasons: the difference in the flame radiation and the difference in jet similarity in coaxial air flames. From the radiation measurements, more detailed explanations on these deviations were suggested.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.33 no.9
• /
• pp.699-708
• /
• 2009

To understand hydrogen jet liftoff height, the stabilization mechanism of turbulent lifted jet flames under non-premixed conditions was studied. The objectives were to determine flame stability mechanisms, to analyze coexistence of two different flame structure, and to characterize the lifted jet at the flame stabilization point. Hydrogen flow velocity varied from 100 to 300 m/s. Coaxial air velocity was changed from 12 to 20 m/s. Simultaneous velocity field and reaction zone measurements used, PIV/OH PLIF techniques with Nd:YAG lasers and CCD/ICCD cameras. Liftoff height decreased with the increase of fuel velocity. The flame stabilized in a lower velocity region next to the faster fuel jet due to the mixing effects of the coaxial air flow. The flame stabilization was related to turbulent intensity and strain rate assuming that combustion occurs where local flow velocity and turbulent flame propagation velocity are balanced. At the flame base, two different flame structures were found that was the partial premixed flames and premixed flame.