Experimental study of flow regimes in three‐dimensional confined impinging jets reactor

Abstract

Dynamic behaviors in a three‐dimensional confined impinging jets reactor (CIJR) were experimentally studied by a flow visualization technique at 100 ≤ Re ≤ 2000 and 2 ≤ D/d ≤ 12 (where D is the reactor diameter and d is the nozzle diameter). The effects of inlet Reynolds numbers (Re) and geometry configurations of the CIJR on the flow regimes have been investigated by a particle image velocimetry and a high‐speed camera. Results show that with the increasing Re, a segregated flow regime, a radial deflective oscillation, an axial oscillation and a vortex shedding regime emerge in turns in CIJR. A map of parameter space formed by the inlet Reynolds number (Re) and the normalized reactor diameter (D/d) has been presented. The effects of jet instability and confined boundary of the chamber on the flow regimes and their transition are also investigated and discussed. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3033–3045, 2014

Experimental study of oscillation behaviors in confined impinging jets reactor under excitation

“…At Re = 150, the deflective oscillation nearly keeps invariable and is not affected by the excitation of k < 20%. It should be noted that the induced deflective oscillation at Re ≤ 100 is distinct to the self‐sustained deflective oscillation at Re = 150, as the former is mainly induced by the axial oscillation which is caused by the excitation of the pulsed inflow, but the latter is mainly determined by the interaction of the impingement plane and the confined wall of chamber . Results in this study prove that the axial oscillation is caused by the inflow fluctuation in the opposed jets in CIJR while the deflective oscillation is a kind of self‐sustained oscillation …”

“…The recorded digital images were analyzed by the NIH image freeware to obtain the oscillation frequencies or oscillation amplitudes of the dynamic behavior of the impingement plane in CIJR. The detailed method of the image processing can be found in our previous papers …”

“…The flow and mixing in CIJR have been intensively investigated in last three decades by means of flow visualization techniques, experimental measurements, numerical simulations, and theoretical analyses . Many researchers have observed the transition from a segregated steady flow to a dynamic chaotic flow regime in CIJR at Re > 100, which is characterized by the formation of a pancake‐like structure and the flow oscillates with a complex mode .…”

“…With increasing Reynolds numbers above the critical one, the flow in CIJR begins to show a more chaotic behavior . In our recently published paper, the flow regimes in CIJR were experimentally investigated at 100 ≤ Re ≤ 2000 and 2 ≤ D / d ≤ 12 (where D is the reactor diameter and d is the nozzle diameter). It has been indentified that with increasing Re , a segregated flow regime, a self‐sustained deflective oscillation and a combination regime of vortex shedding and axial instability emerge in turns.…”

Experimental study of mixing enhancement of viscous liquids in confined impinging jets reactor at low jet Reynolds numbers

“…The results in the literature have indicated that for Re≤100 a segregated steady flow regime occurs and at higher Reynolds numbers the flow is observed to transform to a dynamic chaotic flow regime in CIJR (Tucker and Suh, 1980;Mahajan and Kirwan, 1996;Johnson and Wood, 2000;Santos et al, 2005Santos et al, , 2008Santos et al, , 2009Li et al, 2014). Up to now the flow regime in CIJR has been intensively investigated, but the internal relationship between the oscillation behaviors and mixing performance has not been clearly revealed yet.…”