Abstract
Fluid flow characteristics and particle motion behavior of an impinging stream reactor with dynamic inlet flow (both inlet velocity patterns exhibit step variation) are investigated and discussed with the computational fluid dynamics–discrete element method (CFD–DEM). The effect of T (variation period of the dynamic inlet flow) and ∆u (inlet velocity difference) on the motion characteristics of single and multiple particles, as well as the mean particle residence time, are studied and discussed. The research results indicate that, compared with the traditional impinging stream reactor (both inlet velocities are equal and constant) with equal mean inlet velocity (um) within one period, the impinging surface is instantaneously moving and the flow regime is varied with time in the impinging stream reactor with dynamic inlet flow. The impinging stream reactor with dynamic inlet flow provides higher cost performance over the traditional impinging stream reactor, under equal um, in terms of single-particle residence time. Moreover, three new particle motion modes exist in multi-particle motions of the impinging stream reactor with dynamic inlet flow; particles are accelerated by the original or reverse fluid and perform oscillatory motion at least once after an interparticle collision. Whether it is a single particle or multi-particles, the mean particle residence time reaches a maximum value when T/2 is approximately equal to the first particle acceleration time, since the maximum axial kinetic energy increases in every oscillatory motion compared with traditional impinging stream, and the number of oscillatory motions is increasing. The mean residence time of a particle in the impinging stream reactor with a dynamic inlet flow increases with increasing ∆u, since the dynamic inlet conditions and increasing ∆u can continuously supply more energy to particles and thus cause more particles to enter one of the three new modes of particle motion.
Highlights
The impinging stream technique was first proposed by the Soviet scientist Elperin in 1961, and investigated and discussed by many scholars and scientists [1,2,3,4]
Liu et al [20] carried out many simulations to investigate and measure the gas flow characteristics and particle motion behavior in the impinging stream reactor
We studied an impinging stream reactor with dynamic inlet flow, where both inlet velocity patterns exhibit step velocity variations with a half-period phase difference
Summary
The impinging stream technique was first proposed by the Soviet scientist Elperin in 1961, and investigated and discussed by many scholars and scientists [1,2,3,4]. Wang et al [19] performed many simulation studies to investigate and measure the mixing performance and fluid motion behavior of multiple and multi-set three-dimensional confined turbulent round opposing jets They found that flow and mixing characteristics have a close relationship with the impinging stream configuration. Li and Yao [22] experimentally studied the flow regime of the axisymmetric and planar impinging stream reactor by means of a smoke-wire technique. Zhang [23] and Liu performed many experimental studies on the flow characteristics in free impinging jet reactors by particle image velocimetry They analyzed the effect of inlet parameters and the ratio of the jet distance to the jet diameter on the liquid flow behavior, turbulent kinetic energy distribution, and mixing efficiency of the impinging jet reactor
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