Experimental Investigation And Numerical Simulation Of Flow Characteristics In Asymmetric Confined Impinging Jets Reactor

Confined impinging jets reactors (CIJRs) is widely used in absorption, drying, mixing and nanoparticles precipitation because of the advantage of CIJRs the good performance of mixing. However, the flow characteristics of CIJRs don’t be sufficiently studied and there have been few investigations on asymmetric CIJRs. In this study, flow characteristics, mainly including mean velocity, root mean square (RMS) and turbulence kinetic energy (TKE) were investigated by Particle image velocimetry (PIV) and large eddy simulation (LES) at different inlet flow rates ranging from Re=17600-45300 in an asymmetric impinging jet (3-4 mm). The instantaneous stagnation point in each experimental and LES result picture is analyzed, indicating that the position of instantaneous stagnation point is in accordance with normal distribution. Three component mean velocities (U, V, and W) and RMS velocities (rmsU, rmsV, and rmsW) are presented and compared between PIV and LES results. TKE distributions were obtained from two velocity components using isotropic approximation. Based on the LES model and the experimental data, it can be concluded that the distance between horizontal axis of jets and top wall of the mixing chamber H and different velocity ratio had a very complicated effect on the flow field and stagnation point. The increase of H within a certain range could increase TKE and enhance the mixing efficiency in the impinging zone, which was beneficial for the mixing. Under conditions that the fluid fully developed and the velocity ratio of the fluid kept constant, the size of Re had little influence on the average velocity distribution, fluctuating velocity distribution and TKE distribution. The factor of velocity ratio had a significant effect on the stagnation position. The mean velocity distribution at different impinging velocity ratio was presented, indicating the position of the stagnation point in asymmetric CIJRs is closely related to the jet velocity ratio. Changes in the speed of 10% affected changes in stagnation point offset of 35% and the offset rule was nearly consistent in different sizes of entrance, thus it was necessary to accurately ensure the position of impinging. The accuracy of LES model was verified by comparing with PIV experimental results in all cases, presenting that the LES method can be used to simulate the complex flow characteristics. Both the experimental data and LES results could be applied to further understand the mixing performance in the asymmetric CIJRs and made optimization of the reactor.