Recurrence Quantity Analysis of the Instantaneous Pressure Fluctuation Signals in the Novel Tank with Multi-Horizontal Submerged Jets

Jet mixers have numerous advantages over impellers, which makes them suitable for industrial applications, such as extraction1, chemical reaction2, absorption and desorption3, mixing4, reaction injection molding5, side-dump combustion6–7, etc. There have been many studies on jet mixing in the past 70 years. Commonly encountered jet mixing tanks use a single jet with constant mean flow. Fossett and Prosser8 determined the performance of free jets for mixing fluids in large circular tanks with scale models. Lehrer9 defined the entrainment ratio in the fully developed jet, and found that the jet mixing time was inversely proportional to the entrainment ratio. Unsteady jets have been found to be more energy-efficient than steady jets10. Riffat et al.11 investigated the refrigerant flow patterns and pressure distribution through the ejector unit using the CFD method. Ranade12 investigated the flow patterns and mixing performances in jet mixing tanks using the standard κ-ε model. Simulations of mixing performance in various vessel configurations have been conducted as shown in the References of Jayanti13, Zughbi and Rakib14. Patwardhan and Thatte15 investigated the effects of jet velocity, nozzle clearance, liquid depth, and tank size on mixing time with the help of CFD modeling. Some efforts on computational fluid dynamics and experimental studies of mixing in fluid-jet-agitated tanks have been made16–21. The circulating jet tank (CJT) is novel jet mixing equipment based on multi-horizontal submerged nozzles. The CJT has been used successfully in industrialized production processes of polyvinyl chloride (PVC) in Liaoning Huajin Chemical Industry Group Co., Ltd. for over 10 years, and has provided better economic benefits22. The steady flow in the CJT has been investigated based on numerical simulations by Yu et al.23 It was proved that the internal fluid flow of the jet tank was a strong shear turbulent jet. However, due to the complexity of the hydrodynamics, the design and scaling of this chemical reactor are still not straightforward with an inadequate understanding of fluid properties. The effects of global circulation, trailing vortices, and small-scale turbulence on macromixing and micromixing is not so clear. Some different types of motion coexist in the CJT: mean flow or global circulation, periodic fluctuations or vortices induced by the jet impinging the wall and the baffles, and the turbulent fluctuations that finally dissipate the kinetic energy24. There are many other techniques that could be used to determine the hydrodynamic properties of CJT, such as Phase Doppler Particle Anemometer (PDPA), Particle Image Velocimetry (PIV), and Pressure Fluctuation Signals (PFS). In recent years, a number of methods have been devised to analyze the dynamical characteristics of the time series25–29. The jet flow in the CJT was proved to be a nonlinear system based on PFS experimental investigation22,30,31. The nonlinear systems are able to generRecurrence Quantity Analysis of the Instantaneous Pressure Fluctuation Signals in the Novel Tank with Multi-Horizontal Submerged Jets