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The paper analyzed flow characteristics in vortex diode with double tangential tube by numerical simulation. Compared to traditional vortex diode with one tangential tube, the structure of double tangential tube can reduce the forward resistance and improve overall performance. The symmetrical design adopted in vortex diode with double tangential tube; the internal flow field in chamber showed symmetrical distribution in the reverse flow, which can improve the flow stability and accelerate the convergence speed in simulation.

As a new maintenance-free device, vortex diode pump device begins to be used in nuclear industry for spent fuel transportation, and is extended to the chemical and pharmaceutical industries. The basic working principle of vortex diode is that its working fluid through the pros and cons vortex diode has different drag coefficients, which is similar to the role of “diode” in the circuit. The structure of Vortex diode includes three parts: tangential tube, axial tube and chamber. In the case of forward flow, the working fluid flows into the chamber from the axial tube, and outflows from the tangential tube. Its internal flow field is relatively simple. In the case of reverse flow, the working fluid flows into the chamber from tangential tube and outflows from the axial tube. The internal field is rendered as complex three-dimensional turbulent flow field, in which a strong vortex is formed near the center of chamber. The most important parameter to measure its overall performance is impedance ratio which is defined as the ratio of reverse resistance coefficient to the forward resistance coefficient.

Many scholars have done a lot of work in studying the structure of vortex diode. Tapered and divergent structure was used in the axial tube. Taper angle of tangential tube was changed and the chamber in configuration was designed. All above is in order to improve its overall performance or one-way performance. In addition, some calculation models were considered in reverse flow. Malhotra A used standard k-ε model to calculate swirl problem, which had a degree of error [

This paper analyzed flow characteristics in vortex diode with double tangential tube by numerical simulation. Vortex diode with double tangential tube shows better performance in the forward flow and overall performance, compared with traditional vortex diode. What’s more, the convergence performance is improved, which can reduce computing time.

The traditional vortex diode structure is shown in

where ∆P is the difference between input pressure and output pressure and ρ is the density of working fluid. u is the velocity of working fluid. Eu_{F} is the forward flow resistance coefficient and Eu_{R} is the reverse flow resistance coefficient.

The vortex diode structure of double tangential tube is shown in

In Forward flow, for it is in isotropic turbulence state, so the calculation model uses the standard k-epsilon model. In reverse flow, the fluid inside the chamber presents vortex motion, which shows the performance of anisotropy and instability. For the swirl problem, standard k-ε model, realizable k-ε model, RNG k-ε model, Reynolds stress model and large eddy simulation model can all be considered. Although realizable k-ε model and RNG k-ε model are more reliable than standard k-ε model, they are still not ideal. Reynolds stress model directly models individual items, which is better than the two models above in simulation results. Large eddy simulation has the best performance, but it is time-consuming during computation. Given simulation accuracy and economy, Reynolds stress model is appropriate to be used to calculate in reverse flow.

The import condition of forward and reverse flow are set as speed of working

fluid. Outlet pressure is set as the constant 0, while a given hydraulic diameter and turbulence intensity are taken as import turbulent conditions. In reverse

flow simulation, import Reynolds stress values meet

riod of swirl at the outlet, the outlet pressure produces reflux phenomenon, so the outlet boundary condition is set as outlet-vent and reflux is eliminated by increasing the resistance loss coefficient at the outlet. Equations are solved in Fluent, and the reference pressure (Pressure-Based) algorithm is adopted. In addition, optimization polyhedron tetrahedral mesh grid technology is applied, and PRESTO is used to discrete items of pressure as well. The SIMPLE algorithm is applied to format, pressure and velocity coupling, and second order upwind scheme is applied to Momentum and turbulence kinetic energy dissipation rate too [^{−}^{5}.

The pressure and speed contours of the vortex diode with double tangential tube are shown in

Due to the stability of the internal flow field, the convergence speed has improved significantly in reverse flow.

different structures in the same computer.

At the same Reynolds number, impedance ratio of the vortex diode with double tangential tube is significantly higher than ordinary vortex diode. With one more exit tube set than ordinary vortex diode, forward flow resistance decreases significantly, and the reverse flow resistance reduces at the same time. Thus, the comprehensive performance is improved. Due to the symmetry of the structure, the internal flow field of reverse flow exhibits symmetrically, which improves the flow stability and speeds up the computing rate significantly as well. Multi-tube vortex diode structure can provide reference for improving the performance of vortex diode.

Sincere thanks to the members of OJMSi for their professional performance and high quality work.

Zhang, L.J., Dai, Y.L., Li, Y.L., Wang, Q., Jin, X.Y., Ma, L. and Huang, W.T. (2017) Simulation Analysis of Flow Characteristics in the Vortex Diode with Double Tangential Tube. Open Journal of Modelling and Simulation, 5, 174-181. https://doi.org/10.4236/ojmsi.2017.53013