No abstract

The impinging stream reactor currently under study, especially in processes of fluid mixing, is employed in a variety of applications that include pharmaceuticals, petroleum, and provisions. The distributions of three‐dimensional velocity fluctuation in the dual nozzle opposed impinging stream mixer were measured experimentally using laser Doppler velocimetry (LDV). The results showed that stagnation points were in proximity of the line of z = 0 under experimental conditions, but the exact positions of these stagnation points shifted with different nozzle diameters, nozzle spacing, and inlet flow rates. The distributions of RMS velocity and turbulent kinetic energy were similar in the same operating condition, but turbulence intensity changed obviously on the z axis ranging from −10 mm to 30 mm, in which region turbulence was intense and the large turbulence intensity was advantageous to mixing. The RMS velocity was influenced obviously by changing distance between nozzles, the turbulence intensity was affected greatly by the nozzle diameters, and the region of high turbulent kinetic energy which was beneficial to mixing was enlarged by increasing inlet flow rates.

The velocity eld in an opposed jet mixer was studied by using Phase Doppler Anemometry (PDA). In this study, the effect of operating conditions such as nozzle separations and inner nozzle diameters was investigated to study the changes in characteristic chaotic parameters (correlation dimension, Kolmogorov entropy, and largest Lyapunov exponent). The velocity eld possessed chaotic characteristics, in which the value of the correlation dimension ranged from 2.34 to 7.52. The characteristic chaotic parameters increased and then decreased as the nozzle distance increased. This re ected the micro-mixing e ciency of the mixer. The e ciency of the mixer improved as the values of the chaotic characteristic parameters increased. Thus, the optimal conditions of microcosmic mixture were obtained. Therefore, a suitable nozzle distance, or decreasing nozzle diameter, is advantageous for the improvement of a mixer's micro-mixing e ciency.