@techreport{oai:jaxa.repo.nii.ac.jp:00002211,
 author = {Zimmer, Laurent and 立花, 繁 and Zimmer, Laurent and Tachibana, Shigeru},
 month = {Mar},
 note = {Simultaneous Particle Image Velocimetry/OH Planar Laser Induced Fluorescence (PIV/OH-PLIF) was used to measure the conditional unburned and burned velocities in turbulent premixed methane-air flames. The flames used were stabilized through a balance between the burning velocity and incoming flow, hence without a recirculation zone or stagnation plate. The turbulent intensity as well as the temperature at the inlet could be changed, so that turbulent scalar fluxes (mu double prime times c double prime averaged) were measured at a velocity ratio (u prime/S(sub L)) ranging from 1 to 5 and a heat release factor from 2 to 5. Turbulence characteristics were obtained using Particle Image Velocimetry technique under reacting conditions, for both turbulent velocity and integral length scale and the OH-PLIF signal provided the scalar information to distinguish between burned and unburned gases. The measurements of the scalar fluxes were evaluated using different processing techniques from PIV and the effects of the grid and processing methods are first discussed. In the present investigation, both counter gradient diffusion and gradient diffusion were measured. Preheated mixtures lead to gradient diffusion due to the lower thermal expansion. Non-preheated flames exhibited counter gradient diffusion behavior except for flames with the lowest equivalence ratio. Comparisons with classical transition criterion based on Bray and modified Bray numbers were not successful for the present data set. Therefore, to correctly predict the transition between gradient and counter-gradient diffusion, a modification to the criterion taking into account pressure gradients effects was proposed. This criterion was also successfully tested with previously published results for which the integral length scales were smaller so as to encompass a wider range of turbulence scales. Furthermore, three different fuels (methane, propane and hydrogen) were used to obtain the new transition, validating the approach over a wide range of situations., 資料番号: AA0063456000, レポート番号: JAXA-RR-06-020E},
 title = {Measurements of turbulent scalar fluxes for methane-air mixtures at different inlet temperatures},
 year = {2007}
}