• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.455-458
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• 2006

This study has numerically modelled the combustion processes of the turbulent swirling premixed lifted flames in the low-swirl burner (LSB). In these turbulent swirling premixed flames, the four tangentially- injected air jets induce the turbulent swirling flow which plays the crucial role to stabilize the turbulent lifted flame. In the present approach, the turbulence-chemistry interaction is represented by the level-set based flame let model. Two-dimensional and three-dimensional computations are made for the various swirl numbers and nozzle length. In terms of the centerline velocity profiles and flame liftoff heights, numerical results are compared with experimental data The three-dimensional approach yields the much better conformity with agreements with measurements without any analytic assumptions on the inlet swirl profiles, compared to the two-dimensional approach. Numerical clearly results indicate that the present level-set based flamelet approach has realistically simulated the structure and stabilization mechanism of the turbulent swirling stoichiometric and lean-premixed lifted flames in the low-swirl burner.

• Journal of the Korean Society of Combustion
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• v.12 no.3
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• pp.8-15
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• 2007

This study has numerically modelled the combustion processes of the turbulent swirling premixed lifted flames in the low-swirl burner (LSB). In these turbulent swirling premixed flames, the four tangentially-injected air jets induce the turbulent swirling flow which plays the crucial role to stabilize the turbulent lifted flame. In the present approach, the turbulence-chemistry interaction is represented by the level-set based flamelet model.. Two-dimensional and three-dimensional computations are made for the various swirl numbers and nozzle length. In terms of the centerline velocity profiles and flame liftoff heights, numerical results are compared with experimental data The three-dimensional approach yields the much better conformity with agreements with measurements without any analytic assumptions on the inlet swirl profiles, compared to the two-dimensional approach. Numerical clearly results indicate that the present level-set based flamelet approach has realistically simulated the. structure and stabilization mechanism of the turbulent swirling stoichiometric and lean-premixed lifted flames in the low-swirl burner.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.4
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• pp.352-356
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• 2008

In this study of lifted hydrogen jet with coaxial air, we have experimentally studied the characteristics of stabilization point in turbulent diffusion flames. The objectives are to present the phenomenon of a liftoff height decreasing as increasing fuel velocity and to analyse the flame structure and behavior including liftoff mechanisms. The fuel jet exit velocity was changed from 100 up to 300 m/s and a coaxial air velocity was fixed at 16 m/s with a coflow air less than 0.1 m/s. For the simultaneous measurement of velocity field and reaction zone, PIV and OH PLIF technique was used with two Nd:Yag lasers and CCD cameras. It has been suggested that the stabilization of lifted hydrogen diffusion flames was correlated with a turbulent intensity, $S_t{\sim}u^{\prime}$, and jet Reynolds number, $S_t{\sim}Re^{0.017}_{jet}$.

• Journal of the Korean Society of Combustion
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• v.22 no.3
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• pp.17-22
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• 2017

An experimental study has been conducted to elucidate the effect of AC electric field on behaviors of laminar lifted flame in nitrogen-diluted methane coflow-jets. Our concerns are focued on the regime to show a decrease in liftoff height, $H_L$ with increasing nozzle exit velocity, $U_O$ (hereafter, $decreasing-H_L$). The $H_L$ with $U_O$ near flame extinction were measured by varying the applied AC voltage, $V_{AC}$ and frequency, $f_{AC}$ in a single electrode configuration. The behavior of $H_L$ with a functional dependency of $V_{AC}$ and $f_{AC}$ was categorized into two regime : (I) $H_L$ decreased for nozzle diameter, D = 1.0 mm, and (II) $H_L$ increased in the increase of $f_{AC}$ for a fixed $V_{AC}$ in a D = 4.0, 8.4 mm. The lifted flames in $decreasing-H_L$ region was unstable in high voltage regimes while the $H_L$ showed a decreasing tendency with $U_O$ except them. Such behaviors in $H_L$ were also characterized by functional dependencies of related physical parameters such as $V_{AC}$, $f_{AC}$, $U_O$, fuel mole fraction ($X_{F.O}$) and D.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.349-352
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• 2008

This study has numerically modeled the combustion processes of the turbulent swirling premixed lifted syngas flames in the low-swirl burner (LSB). In these turbulent swirling premixed flames, the four tangentially-injected air jets induce the turbulent swirling flow which plays the crucial role of stabilizing the turbulent lifted flames. In the present approach, the turbulence-chemistry interaction is represented by the level-set based flamelet model. Numerical results indicate clearly that the present level-set based flamelet approach has realistically simulated the structure and stabilization mechanism of the turbulent swirling premixed lifted flames in the low-swirl burner. Computations are made for the wide range of the syngas chemical composition and the dilution level at two pressure conditions (1.0, 5.0 bar). Numerical results indicate that the lifted height in the LSB is increased by decreasing the H2 percentage and increasing the dilution level at the given equivalence ratio. It is also found that the flashback is occurred for the hydrogen composition higher than 80% at the equivalence ratio, 0.8. However, at the syngas composition range in the IGCC system, the stable lean-premixed lifted flames are formed at the low-swirl burner.