Combined experimental and numerical analysis of cavitating flow characteristics in an axial flow waterjet pump

The collapsing phenomenon of cavitation bubbles generates extremely high local pressures and temperatures that can be utilized for the chemical oxidation process. This process is carried out in cavitation reactors. A Venturi tube is one of the most common forms of hydrodynamic cavitation reactors, which is suitable for industrial scale applications. In this work, the hydraulic performance and efficiency in chemical reaction of a new form of hydrodynamic cavitation reactors, which is called “tandem Venturi,” were studied and compared with the conventional type of the single Venturi. The tandem Venturi is used for enhancement of the chemical reaction of hydrodynamic cavitating flow. The reaction enhancement is useful especially for the reaction of aqueous solutions not containing volatile organic compounds (VOCs). The operating pressure, inlet pressure, flow rate, and consequently the cavitation number were controlled and systematically varied for both single and tandem Venturis. Moreover, a specified amount of H2O2 was injected into the flow as required. The effects of operating pressure and the cavitation number on cavitating flow characteristics for single and tandem Venturis were experimentally observed and the results were compared. In addition, the performance of the tandem-Venturi reactor for degradation of non-VOC contaminants (2-chlorophenol) was studied. Its performance was compared with the performance of a conventional Venturi reactor. Two different categories were conducted for the experiments. In the first category, the effect of the net cavitating flow on degradation of non-VOC for the single and tandem Venturis was compared. In the second category, the effect of H2O2 injection into the cavitating flow on degradation of non-VOC (“cavitation-oxidation” process) was studied. The performance of the single and tandem Venturis for the cavitation-oxidation process was compared. Further investigation was performed to assess the advantage of utilizing the tandem Venturi from the viewpoint of efficiency of the oxidation process. The results of the energy efficiency were compared with the corresponding efficiency of the single Venturi. Finally, the relationship between the main parameters of cavitation reaction flow with the chemical performance was discussed.

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Dynamics of a Supported Cylinder in Axial Flow

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.99-100.1059 ◽

2011 ◽

Vol 99-100 ◽

pp. 1059-1062

Author(s):

Ji Duo Jin ◽

Ning Li ◽

Zhao Hong Qin

Keyword(s):

Nonlinear Dynamics ◽

Numerical Analysis ◽

Numerical Simulations ◽

Nonlinear Model ◽

Dynamical Behavior ◽

Axial Flow ◽

Viscous Force ◽

Friction Drag ◽

Flutter Instability ◽

Nonlinear Force

The nonlinear dynamics are studied for a supported cylinder subjected to axial flow. A nonlinear model is presented for dynamics of the cylinder supported at both ends. The nonlinear terms considered here are the quadratic viscous force and the structural nonlinear force induced by the lateral motions of the cylinder. Using two-mode discretized equation, numerical simulations are carried out for the dynamical behavior of the cylinder to explain the flutter instability found in the experiment. The results of numerical analysis show that at certain value of flow velocity the system loses stability by divergence, and the new equilibrium (the buckled configuration) becomes unstable at higher flow leading to post-divergence flutter. The effect of the friction drag coefficients on the behavior of the system is investigated.

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Numerical analysis on the flow characteristics of oil-injected screw air compressor

2014 ISFMFE - 6th International Symposium on Fluid Machinery and Fluid Engineering ◽

10.1049/cp.2014.1172 ◽

2014 ◽

Author(s):

Sun-Seok Byeon ◽

Youn-Jea Kim ◽

Jae-Young Lee

Keyword(s):

Numerical Analysis ◽

Flow Characteristics ◽

Air Compressor

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Tip Leakage Flow Characteristics Downstream of an Axial Flow Fan

Volume 1: Turbomachinery ◽

10.1115/96-gt-508 ◽

1996 ◽

Cited By ~ 3

Author(s):

P. Puddu

Keyword(s):

Vortex Flow ◽

Three Dimensional ◽

Flow Characteristics ◽

Axial Flow ◽

Tip Leakage Flow ◽

Single Wire ◽

Vortex System ◽

Tip Leakage ◽

Stress Components ◽

Computer Controlled

The three-dimensional viscous flow characteristics and the complex vortex system downstream of the rotor of an industrial exial fan have been determined by an experimental investigation using hot-wire anemometer. Single-wire slanted and straight type probes have been rotated about the probe axis using a computer controlled stepper motor. Measurements have been taken at four planes behind the blade trailing edge. The results show the characteristics of the relative flow as velocity components, secondary flow and kinetic energy defect. Turbulence intensity and Reynolds stress components in the leakage vortex area are also presented. The evolution of the leakage vortex flow during the decay process has also been evaluated in terms of dimension, position and intensity.

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Experimental and Numerical Analysis of Mixing Process of Two Component Gases in a Vertical Fluid Layer in a VHTR

Journal of Nuclear Engineering and Radiation Science ◽

10.1115/1.4041690 ◽

2019 ◽

Vol 5 (2) ◽

Author(s):

Tetsuaki Takeda

Keyword(s):

High Temperature ◽

Natural Convection ◽

Numerical Analysis ◽

Pressure Vessel ◽

Storage Tank ◽

Molecular Diffusion ◽

Flow Characteristics ◽

Mixing Process ◽

Two Component ◽

Air Ingress

When a depressurization accident of a very-high-temperature reactor (VHTR) occurs, air is expected to enter into the reactor pressure vessel from the breach and oxidize in-core graphite structures. Therefore, in order to predict or analyze the air ingress phenomena during a depressurization accident, it is important to develop a method for the prevention of air ingress during an accident. In particular, it is also important to examine the influence of localized natural convection and molecular diffusion on the mixing process from a safety viewpoint. Experiment and numerical analysis using a three-dimensional (3D) computational fluid dynamics code have been carried out to obtain the mixing process of two-component gases and the flow characteristics of localized natural convection. The numerical model consists of a storage tank and a reverse U-shaped vertical rectangular passage. One sidewall of the high-temperature side vertical passage is heated, and the other sidewall is cooled. The low-temperature vertical passage is cooled by ambient air. The storage tank is filled with heavy gas and the reverse U-shaped vertical passage is filled with a light gas. The result obtained from the 3D numerical analysis was in agreement with the experimental result quantitatively. The two component gases were mixed via molecular diffusion and natural convection. After some time elapsed, natural circulation occurred through the reverse U-shaped vertical passage. These flow characteristics are the same as those of phenomena generated in the passage between a permanent reflector and a pressure vessel wall of the VHTR.

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The Effect of the Thickness and Angle of the Inlet and Outlet Guide Vane on the Performance of Axial-Flow Pump

Volume 1A, Symposia: Turbomachinery Flow Simulation and Optimization; Applications in CFD; Bio-Inspired and Bio-Medical Fluid Mechanics; CFD Verification and Validation; Development and Applications of Immersed Boundary Methods; DNS, LES and Hybrid RANS/LES Methods; Fluid Machinery; Fluid-Structure Interaction and Flow-Induced Noise in Industrial Applications; Flow Applications in Aerospace; Active Fluid Dynamics and Flow Control — Theory, Experiments and Implementation ◽

10.1115/fedsm2016-7939 ◽

2016 ◽

Author(s):

Sang-Won Kim ◽

Youn-Jea Kim

Keyword(s):

Numerical Analysis ◽

Numerical Study ◽

Guide Vane ◽

Axial Flow ◽

Inlet Guide Vane ◽

Guide Vanes ◽

Pump Performance ◽

Blade Thickness ◽

Axial Flow Pump ◽

Flow Pump

An axial-flow pump has a relatively high discharge flow rate and specific speed at a relatively low head and it consists of an inlet guide vane, impeller, and outlet guide vane. The interaction of the flow through the inlet guide vane, impeller, and outlet guide vane of the axial-flow pump has a significant effect on its performance. Of those components, the guide vanes especially can improve the head and efficiency of the pump by transforming the kinetic energy of the rotating flow, which has a tangential velocity component, into pressure energy. Accordingly, the geometric configurations of the guide vanes such as blade thickness and angle are crucial design factors for determining the performance of the axial-flow pump. As the reliability of Computational Fluid Dynamics (CFD) has been elevated together with the advance in computer technology, numerical analysis using CFD has recently become an alternative to empirical experiment due to its high reliability to measure the flow field. Thus, in this study, 1,200mm axial-flow pump having an inlet guide vane and impeller with 4 blades and an outlet guide vane with 6 blades was numerically investigated. Numerical study was conducted using the commercial CFD code, ANSYS CFX ver. 16.1, in order to elucidate the effect of the thickness and angle of the guide vanes on the performance of 1,200mm axial-flow pump. The stage condition, which averages the fluxes between interfaces and is accordingly appropriate for the evaluation of pump performance, was adopted as the interface condition between the guide vanes and the impeller. The rotational periodicity condition was used in order to enable a simplified geometry to be used since the guide vanes feature multiple identical regions. The shear stress transport (SST) k-ω model, predicting the turbulence within the flow in good agreement, was also employed in the CFD calculation. With regard to the numerical simulation results, the characteristics of the pressure distribution were discussed in detail. The pump performance, which will determine how well an axial-flow pump will work in terms of its efficiency and head, was also discussed in detail, leading to the conclusion on the optimal blade thickness and angle for the improvement of the performance. In addition, the total pressure loss coefficient was considered in order to investigate the loss within the flow paths depending on the thickness and angle variations. The results presented in this study may give guidelines to the numerical analysis of the axial-flow pump and the investigation of the performance for further optimal design of the axial-flow pump.

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