Dimensionless performance and characteristic numbers of reverse flow diverters during reverse flow mode

2012 ◽  
Vol 8 (3) ◽  
pp. 396-404 ◽  
Author(s):  
Cong Xu ◽  
Hui Yu ◽  
Xiangda Meng
Keyword(s):  
Reverse Flow ◽  
Flow Mode ◽  
Characteristic Numbers ◽  
Flow Diverters

Power Fluidics—Amplifying Properties of Specially Designed Junctions

1977 ◽  
Vol 10 (4) ◽  
pp. 147-154 ◽  
Author(s):  
J. R. Tippetts
Keyword(s):  
Equivalent Circuit ◽  
Reverse Flow ◽  
Signal Power ◽  
Impedance Matrix ◽  
Power Gain ◽  
Large Signal ◽  
Circle Diagram ◽  
Flow Diverters

Specially designed 3-terminal elements called flow-junctions (FJs) and ‘reverse flow diverters' (RFDs) are shown to have useful amplifying properties which are often unrecognised. These are described by relating the devices to ideal network elements using an indefinite circle diagram. The FJ is useful between two transformer-like states and at the mid-point of this range its utility is described by its impedance matrix. A circuit using an RFD is shown to give a large-signal power gain which compares favourably with an equivalent circuit using a vortex device.

Numerical Simulation of Flow Instability in Vortex Diodes

2017 ◽  
Author(s):  
Junrong Wang ◽  
Qi Xiao ◽  
Hanbing Ke ◽  
Xu Hu ◽  
Shaodan Li ◽  
...  
Keyword(s):  
Pressure Fluctuation ◽  
Flow Resistance ◽  
Flow Instability ◽  
Reverse Flow ◽  
Experimental Studies ◽  
Low Flow ◽  
Flow Mode ◽  
Geometrical Parameters ◽  
Typical Structure ◽  
Transient Simulations

A vortex diode is used as a highly reliable check-valve in nuclear applications, where it mainly benefits from the intrinsic properties of no moving parts and no leakage. Its basic principle is similar to the diode in an electric circuit. The typical structure of a vortex diode consists of a chamber with axial and tangential ports. When the fluid is injected through the axial port, a simple radial flow in the chamber leads to a relatively low flow resistance. On the other hand, in the reverse flow mode, a strongly swirling vortex can be set up in the chamber, resulting in a very high flow resistance. Several experimental studies found vortex-induced vibration of a vortex diode in the reverse flow mode, where it indicated that the flow was unstable in the vortex diode. This phenomenon may affect the reliability of the vortex diode. However, the mechanism has not been investigated systematically and profoundly. In this paper, 3-D simulations are carried out to help understand the related flow characteristics in the vortex diode. Standard k-ε model was selected for forward flow, while Reynolds stress model was selected for reverse flow. We have found that the results from transient simulations are in good agreement with experimental data. The transient simulations also capture the periodic pressure fluctuation in the vortex diode. Vortex diodes with different structures and geometrical parameters are simulated at different Reynolds number conditions. It is found that the characteristics of the pressure fluctuation are determined by the structure parameters and working conditions of the vortex diode. The flow instability is mainly caused by the asymmetry of the vortex diode. The work presented in this paper will be useful to give better understanding of flows in vortex diodes and to provide some guidance for optimizing the vortex diode.

scholarly journals Modelling foam improved oil recovery: towards a formulation of pressure-driven growth with flow reversal

2020 ◽  
Vol 476 (2244) ◽  
pp. 20200573
Author(s):  
M. Eneotu ◽  
P. Grassia
Keyword(s):  
Pressure Drop ◽  
Oil Recovery ◽  
Reverse Flow ◽  
Flow Direction ◽  
Flow Reversal ◽  
Flow Mode ◽  
Fractional Flow ◽  
Improved Oil Recovery ◽  
Forward Flow ◽  
Pressure Driven

The pressure-driven growth model that describes the two-dimensional (2-D) propagation of a foam through an oil reservoir is considered as a model for surfactant-alternating-gas improved oil recovery. The model assumes a region of low mobility, finely textured foam at the foam front where injected gas meets liquid. The net pressure driving the foam is assumed to reduce suddenly at a specific time. Parts of the foam front, deep down near the bottom of the front, must then backtrack, reversing their flow direction. Equations for one-dimensional fractional flow, underlying 2-D pressure-driven growth, are solved via the method of characteristics. In a diagram of position versus time, the backtracking front has a complex double fan structure, with two distinct characteristic fans interacting. One of these characteristic fans is a reflection of a fan already present in forward flow mode. The second fan however only appears upon flow reversal. Both fans contribute to the flow’s Darcy pressure drop, the balance of the pressure drop shifting over time from the first fan to the second. The implications for 2-D pressure-driven growth are that the foam front has even lower mobility in reverse flow mode than it had in the original forward flow case.

Aerobic sludge granulation in a Reverse Flow Baffled Reactor (RFBR) operated in continuous-flow mode for wastewater treatment

2015 ◽  
Vol 149 ◽  
pp. 437-444 ◽  
Author(s):  
Jun Li ◽  
Ang Cai ◽  
Libin Ding ◽  
Balasubramanian Sellamuthu ◽  
Jonathan Perreault
Keyword(s):  
Wastewater Treatment ◽  
Continuous Flow ◽  
Reverse Flow ◽  
Flow Mode ◽  
Sludge Granulation ◽  
Aerobic Sludge

scholarly journals Effects of a Hydraulic Series Connection and Flow Direction on Electricity Generation in a Stack Connected with Different Volume MFCs

2021 ◽  
Vol 11 (3) ◽  
pp. 1019
Author(s):  
Jaecheul Yu
Keyword(s):  
Phase Ii ◽  
Microbial Fuel Cells ◽  
Reverse Flow ◽  
Flow Direction ◽  
Pearson Correlation ◽  
Oxygen Demand ◽  
Principal Component ◽  
Phase Iii ◽  
Flow Mode ◽  
Forward Flow

Three microbial fuel cells (MFCs) with different volumes (S-, M-, and L-MFCs) were operated at individual flow (phase I) and serially connected flow modes (phase II for forward flow and phase III for reverse flow) at the same flow rate. The three MFCs showed different voltages and power generation according to the hydraulic and electric connection modes. The M- and L-MFCs showed a similar voltage at hydraulic series-forward flow mode (phase II). The principal component analysis (PCA) and Pearson correlation showed that voltage generation and power density were affected by volume, hydraulic retention time (HRT), chemical oxygen demand (COD) loading rate, removed COD, and internal resistances. When they were connected electrically in series and parallel, the stack showed relatively lower voltage loss (28–30%) compared to the voltage losses of the other stacks (43–94%). These results suggest an easy way to connect MFCs with different volumes can be a new option to avoid voltage reversal and minimize energy loss.

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