• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.27 no.8
• /
• pp.1089-1096
• /
• 2003

An experiment was performed to investigate lift-off, blow-off and combustion characteristics of a lifted coaxial diffusion flame according to fuel jet and air velocity. A jet diffusion flame which is attached on the nozzle rim begins to be lifted with increase of air velocity, and finally becomes blow-off at higher air velocity. In experiment, blow-off limit increased with increase of fuel jet velocity, however lift-off occurred at lower air velocity. Flame structure and combustion characteristics were examined by schlieren photos, temperature distributions and emission concentration distributions. Flame temperature became higher at midstream and its RMS became larger at up and downstream with increase of air velocity. Local NO concentration decreased but $CO_2$concentration increased with increase of air velocity, which shows combustion reaction becomes close to be stoichiometric at higher air velocity in spite of lift-off.

• 한국연소학회:학술대회논문집
• /
• 2000.12a
• /
• pp.113-122
• /
• 2000

Dynamic structures of unsteady $CH_4$/Air jet diffusion flames with flame-vortex interaction were numerically investigated. A time-dependent, axisymmetric computational model was adopted for this calculation. Two step global reaction mechanism which considers 6 species, was used to calculate the reaction rates. The predicted results including gravitational effect show that the large outer vortices and the small inner vortex street can be well simulated without any additional disturbances in the downstream of nozzle tip. It was found that the temperature and species concentrations had various values for the same mixture fraction in flame-vortex interaction region. This unsteady jet flame configuration accompanying flame-vortex interaction is expected to give good implications for the structure of turbulent flames.

• 한국연소학회:학술대회논문집
• /
• 2002.06a
• /
• pp.68-75
• /
• 2002

The dynamic behaviors of the single vortex and flame-vortex interaction in a $CH_4/Air$ diffusion flame with addition of $CO_2$ were investigated numerically. The numerical method was based on a predictor-corrector for low Mach number flow. A two-step global reaction mechanism was adopted as a combustion model. Through comparison of results by effect of $CO_2$ added either on the fuel or oxidizer side, it was found that the growth of single vortex and entrainment of surrounding fluid by $CO_2$addition on the fuel side are larger than those by $CO_2$ addition on oxidizer side. Also, when $CO_2$ is added on fuel side, flame-vortex interaction becomes more significant than on air side.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.25 no.1
• /
• pp.29-35
• /
• 2001

Radiation-induced oscillatory instability in CH$_4$/Air diffusion flames is numerically investigated by adopting detailed chemistry. Counterflow diffusion flame is employed as a model flamelet and optically thin gas-phase radiation is assumed. Attention is focused on the extinction regime induced by radiative heat loss, which occurs at low strain rate. Once a steady flame structure is obtained for a prescribed value of initial strain rate, transient solution of the flame is calculated after a finite amount of strain-rate perturbation is imposed on the steady flame. Depending on the initial strain rate and the amount of perturbed strain rate, transient evolution of the flame exhibits various types of flame-evolution behaviors. Basically, the dynamic behaviors can be classified into two types, namely oscillatory decaying solution and diverging solution leading to extinction.

• 한국연소학회:학술대회논문집
• /
• 1998.10a
• /
• pp.47-57
• /
• 1998

Characteristics of evaporation, flame propagation at moment of ignition and steady state combustion, and flow characteristics of combustible mixture have been investigated by experiments and computational simulation for the evaporation pot type kerosene burner. The results show how to design the evaporation pot in order to minimize the sticking of residual tar, and also indicate that symmetrical flame propagation along the flame ring from the kernel of ignition is achieved by modication of the shape of ignition part. In the case of steady state combustion, the uniform distribustion of flame at each flame hole is accomplished by proper modification of the piping instruments. The improved design of the structure and parts of the kerosene burner make up enhancement of flame stability and considerable reduction of CO and bad smell emission at moment of ignition.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.20 no.3
• /
• pp.979-987
• /
• 1996

A theoretical study for the laminar round jet diffusion flame impinging on the wall was carried out to predict the characteristics and structure of impinging jet flame and heat transfer to the wall. Finite chemistry via Arrhenius equation was adopted as the combustion model. All the transport properties were considered as the variable depending on the temperature and composition. For the parametric study, the distance from nozzle to perpendicular wall and Reynolds number at nozzle exit were chosen as the major parameters. As the results of the present study, the characteristics of flow field and the distributions of temperature, density and each chemical species were obtained. The heat transfer rate from flame to the wall and the effective heating area were calculated to investigate the influence of the major parameters on the heat transfer characteristics.

• Journal of the Korean Society of Industry Convergence
• /
• v.4 no.2
• /
• pp.185-191
• /
• 2001

Diphenylpropylamidophosphate(DPPAP) was synthesized as flame retardant for Expanded Polystyrene(EPS). Structure of DPPAP was investigated by the m, NMR, DSC. We make FR panels with EPS beads which treated with DPPAP and expanded by expand machines. FR panels were used in this study after formation by form machines and then cutting by cutting machines. The following conclusions were obtained: 1. The new synthetic agent was developed without the use of solvent such as pyridine or tertiary amine in the synthesis of DPPAP which served as flame retardant for EPS. 2. The flame retandancy effect of EPS treated with DPPAP was found excellent in LOI tests. 3. The properties of FR EPS panels treated with DPPAP did not difference.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.18 no.4
• /
• pp.33-42
• /
• 2014

Flame behaviors and interaction between pilot and main flames in a dual swirl combustor were investigated experimentally and numerically. Under the condition of fixed swirl angle of $45^{\circ}$ for main flame, the swirl angle of pilot flame, total heat release rate and equivalence ratio of main flame were used as major parameters. As a result, detailed flame stability diagram of dual swirl combustor was identified in terms of 5 flame modes with the changes in total heat release rate and equivalence ratio of main flame. It was found that the swirl angle of pilot flame plays the most important role in the changes in flame location and overall flow structure inside the combustor, and thus leads to the significant change in the interaction between pilot and main flame.

• Applied Chemistry for Engineering
• /
• v.17 no.2
• /
• pp.144-149
• /
• 2006

Non-halogen flame retardants have been the focus of extensive research because of environmental problems. Hexakisp-henoxycyclotriphosphazene was synthesized in order to use as the flame retardant of ABS resin. And using bisphenol A, the polymers containing a cyclotriphosphazene structure were synthesized in order to also use as the flame retardant of ABS resin. All of the synthesized polymers themselves had the excellent flame retardancy. And as their molecular weight and crosslinking density were increased, the thermal stability was increased. But when the synthesized compounds were used as the flame retardant for ABS resin, the lower molecular weight compound in these compounds showed the better flame retardancy and the better physical properties of ABS resin.

• 한국연소학회:학술대회논문집
• /
• 2002.06a
• /
• pp.52-60
• /
• 2002

A two-dimensional direct numerical simulation is performed to investigate the flame structure of $CH_4/N_2-Air$ counterflow nonpremixed flame interacting with a single vortex. The detailed transport properties and a modified 16-step augmented reduced mechanism based on Miller and Bowman's detailed reaction mechanism are adopted in this calculation. To quantify the strain on flame induced by a vortex, a scalar dissipation rate (SDR) is introduced. Results show that the fuel and air-side vortex cause an unsteady extinction. In this case, the flame interacting with a vortex is extinguished at much larger SDR than steady flame. It is also found that air-side vortex extinguishes a flame more rapidly than fuel-side vortex. The unsteady effect induced by flame-vortex interaction does not lead to a transient OH overshoot of the maximum steady concentration observed in experiment, while $HO_2$ radical increases more than the maximum steady concentration with increasing SDR. In addition, it is seen that NO and $NO_2$ are not sensitive to the unsteady variation of SDR.