Jeongseog Oh

Characteristics of Non-premixed Synthetic Natural Gas-Air Flame with Variation in Fuel Compositions

The combustion characteristics with variations in synthetic natural gas (SNG) compositions were studied in a lab-scale combustor. The objective of the current study is to investigate the flame stabilization, flame structure, and spectrometry in a non-premixed SNG flame with varying fuel compositions. For the analysis of light emission in SNG flames, we used a spectrometer. As experimental conditions, the fuel jet velocity at the nozzle exit was varied from 5 to 40 m/s and the coaxial air velocity was varies from 0 to 0.43 m/s. The experiments showed that the flame stability increased with the hydrogen component in SNG.

Study of Hydrogen Turbulent Non-premixed Flame Stabilization in Coaxial Air Flow

It was experimentally studied that the stabilization mechanism of turbulent, lifted jet flames in a non-premixed condition to reveal the newly found liftoff height behavior of hydrogen jet. The objectives are to report the phenomenon of a liftoff height decreasing as increasing fuel velocity, to analyse the flame structure and behavior of the lifted jet, and to explain the mechanisms of flame stability in hydrogen turbulent non-premixed jet flames. The hydrogen jet velocity was changed from 100 to 300m/s and a coaxial air velocity was fixed at 16m/s with a coflow air less than 0.1m/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. As a result, it was found that the stabilization of lifted hydrogen diffusion flames is correlated with a turbulent intensity and Karlovitz number.

Characteristics of NOx Emission in a Swirl Flow in Nonpremixed Turbulent Hydrogen Jet with Coaxial Air

The effect of swirl flow on NOx in a nonpremixed turbulent hydrogen jet with coaxial air was studied. The swirl vane angle was varied from 30° to 90°. The fuel jet air velocity and coaxial air velocity were varied in an attached flame region as uF=85~160m/s and uA=7~14m/s. The objective of the current study was to analyze the characteristics of nitrous oxide emission in a swirl flow and to propose a new parameter for EINOx scaling. The experimental results show that EINOx decreases with the swirl vane angle and increased with flame length. Further, EINOx scaling factors can be determined by considering the effective diameter (dF,eff) in a far field concept. The EINOx increased in proportion to the flame residence time (~τR

Flame Structure of a Liftoff Non-Premixed Turbulent Hydrogen Jet with Coaxial Air

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.

The Effect of N2Dilution on the Flame Stabilization in a Non-Premixed Turbulent H2Jet with Coaxial Air

The study of nitrogen dilution effect on the flame stability was experimentally investigated in a nonpremixed turbulent lifted hydrogen jet with coaxial air. Hydrogen gas was used as a fuel and coaxial air was used to make flame liftoff. Each of hydrogen and air were injected through axisymetric inner and outer nozzles (dF=3.65 mm and dA=14.1 mm). And both fuel jet and coaxial air velocity were fixed as uF=200 m/s and uA=16 m/s, while the mole fraction of nitrogen diluents gas was varied from 0.0 to 0.2 with 0.1 step. For the analysis of flame structure and the flame stabilization mechanism, the simultaneous measurement of PIV/OH PLIF laser diagnostics had been performed. The stabilization point was selected in the most upstream region of the flame base and defined as the point where the turbulent flame propagation velocity was equal to the axial component of local flow velocity. We found that the turbulent flame propagation velocity increased with the decrease of nitrogen mole fraction. We concluded that the turbulent flame propagation velocity was expressed as a function of turbulent intensity and axial strain rate, even though nitrogen diluents mole fraction was changed.