Gas-flow measurements in a jet flame using cross-correlation of high-speed particle-images

Abstract

Time changes of a two-dimensional distribution of velocities in a nitrogen jet and a methane jet flame are measured by cross-correlation particle-image-velocimetry (PIV). From the measured results in a jet and a jetting flame, it is shown that the velocity gradient at shear layer in the reacting zone is increased due to the local acceleration by buoyancy, resulting in higher turbulence intensities compared with those in a non-reacting jet. Also, from the change of the distribution of velocity vectors with time, it is observed that the turbulence eddies are carried downstream along the gas motion with a little transformation. The time scale of turbulence at every location in the flow is obtained from the autocorrelation function of the velocity fluctuations. Furthermore, this can afford to estimate the turbulence length-scale. It is shown that the characteristic length-scales of a flaming jet are about 1.5 times greater than those of a non-flaming jet.