Flow Field of Turbulent Premixed Combustion in a Cyclone-Jet Combustor

Abstract

The flow field in highly turbulent premixed combustion has been examined, using a cyclone-jet combustor. The shear-strain rate is obtained by PIV system. Results show that, in combustion field, mean axial velocity does not decay along center axis and RMS fluctuation velocity is much lower, compared with those in cold flow. The reaction zone detected by an ion probe well corresponds to region of large shear-strain rate. In combustion, turbulence is small around reaction zone to have the undiminished jet velocity, which leads to an increase in length of potential core, although the flame generated turbulence is observed through flow expansion.

Numerical Study of Isothermal Flow and Mixing Characteristics in a Cyclone-Jet Hybrid Combustor

“…From the comparisons of the predicted mean and rms axial velocities with previous measurements in a cyclone-jet premixed combustor, 14 it was confirmed that the numerical model used in the present study provided good results and thus was able to be utilized to investigate the flow structure and mixing characteristics in the cyclone-jet hybrid combustor.…”

“…Validation of the CFD Model. The selected numerical model was first validated by comparing the measured velocity profiles of cold flow in a cyclone-jet premixed combustor conducted by Yamamoto et al 14 The combustor consisted of a combustion chamber with a main jet nozzle and four cyclone nozzles. The inner diameters of the main jet nozzle and cyclone nozzles were 12.7 and 2.4 mm, respectively.…”

“…Radial profiles of mean and rms axial velocities were measured using a particle image velocimetry (PIV) technique. A detailed description of the experimental setup and procedure is available in the report by Yammamoto et al 14 The comparisons of the calculated and measured data at four axial locations are shown in Figure 3. An unstructured hexahedral grid of about 1 million cells was used to obtain grid-independence results for the cyclone-jet combustor.…”

“…In addition, considering that similar behaviors of the recirculation zone were observed between the isothermal and the reacting flows, the understanding of flow structure and mixing characteristics for the isothermal turbulent flow will provide useful information on the optimized combustor geometry and operating conditions. The numerical model used was first validated by comparing the predicted velocity profiles in a cyclone-jet premixed combustor with published experimental data by Yamamoto et al Then, detailed flow structure and fuel−air mixing characteristics were compared between the diffusion mode and the hybrid mode. The effects of the axial jet nozzle geometry on flow structure and fuel−air mixing were also discussed under an identical condition of a previous experimental study …”

“…Figure 3. Numerical validation for the premixed cyclone-jet combustor in terms of mean axial and rms axial velocity in cold flow with published experimental results 14. …”