Numerical Study of Cavitating Flow in Two-Phase LNG Expander

2016 ◽  
Author(s):  
Peng Song ◽  
Jinju Sun ◽  
Kaiqiang Li ◽  
Ke Wang ◽  
Changjiang Huo
Keyword(s):  
Design Optimization ◽  
Numerical Study ◽  
Temperature Drop ◽  
Flow Analysis ◽  
Flow Characteristics ◽  
Cavitating Flow ◽  
Cavitation Model ◽  
Two Phase ◽  
Hydraulic Turbines ◽  
Liquefaction Process

LNG expander is developed and used as a replacement of a J-T valve in liquefaction process of natural gas to reduce significantly the energy consumption in the LNG plant. Similar to conventional hydraulic turbines, the unexpected cavitation also occurs in the LNG expander. In the present study, cavitating flow in two-phase LNG expander is investigated. With the justified Rayleigh-Plesset cavitation model, cavitating flow characteristics is investigated for the LNG expander in the entire stage environment including an annular bend, nozzle ring, and radial inflow impeller. On the basis of cavitating flow analysis, a coaxial rotating exducer is developed and fitted downstream to the impeller, so as to reduce the cavitation in impeller and subsequently prevent impeller damage. The following are demonstrated: (1) without exducer, significant cavitating flow is encountered at the impeller trailing edge and also in half streamline-wise region, and they are resulted from the viscous dissipation and flow separation; (3) with exducer, the impeller cavitation has diminished entirely but it has occurred in the successive exducer; (3) a use of exducer enhances the energy conversion capability of the rotors, but reduces the overall temperature drop and efficiency of the expander; (4) the design optimization of exducer is required to suppress the exducer cavitation, which also needs to be incorporated with the impeller design to achieve a better match between rotor/stator, so as to maximize the design optimization benefits.

Numerical study of cavitating flow over hydrofoil in the presence of air

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Włodzimierz Wróblewski ◽  
Krzysztof Bochon ◽  
Mirosław Majkut ◽  
Krzysztof Rusin ◽  
Emad Hasani Malekshah
Keyword(s):  
Numerical Study ◽  
Cavitating Flow ◽  
Cavitation Model ◽  
Two Phase ◽  
Content Type ◽  
Flow Simulations ◽  
Cavity Structure ◽  
Dynamic Forces ◽  
High Dynamic ◽  
The Impact

Purpose The presence of air in the water flow over the hydrofoil is investigated. The examined hydrofoil is ClarkY 11.7% with an angle of attack of 8 deg. The flow simulations are performed with the assumption of different models. The Singhal cavitation model and the models which resolve the non-condensable gas including 2phases and 3phases are implemented in the numerical model. The calculations are performed with the uRANS model with assumption of the constant temperature of the mixture. The two-phase flow is simulated with a mixture model. The dynamics and structures of cavities are compared with literature data and experimental results. Design/methodology/approach The cavitation regime can be observed in some working conditions of turbomachines. The phase transition, which appears on the blades, is the source of high dynamic forces, noise and also can lead to the intensive erosion of the blade surfaces. The need to control this process and to prevent or reduce the undesirable effects can be fulfilled by the application of non-condensable gases to the liquid. Findings The results show that the Singhal cavitation model predicts the cavity structure and related characteristics differently with 2phases and 3phases models at low cavitation number where the cavitating flow is highly dynamic. On the other hand, the impact of dissolved air on the cloud structure and dynamic characteristic of cavitating flow is gently observable. Originality/value The originality of this paper is the evaluation of different numerical cavitation models for the prediction of dynamic characteristics of cavitating flow in the presence of air.

Numerical Prediction of Critical Cavitation Performance in Hydraulic Turbines

2003 ◽  
Author(s):  
Sadao Kurosawa ◽  
Kiyoshi Matsumoto
Keyword(s):  
Flow Model ◽  
Flow Analysis ◽  
Prediction Method ◽  
Hydraulic Turbine ◽  
Francis Turbine ◽  
Two Phase ◽  
Cavitation Performance ◽  
Hydraulic Turbines ◽  
Critical Cavitation ◽  
Good Agreement

In this paper, numerical method for predicting critical cavitation performance in a hydraulic turbine is presented. The prediction method is based on unsteady cavitation flow analysis to use bubble two-phase flow model. The prediction of the critical cavitation performance was carried out for the aixal hydraulic turbine and the francis turbine as a typical examples. Results compared to the experiment showed a good agreement for the volume of cavity and the performance drop off and it was recognized that this method could be used as an engineering tool of a hydraulic turbine development.

scholarly journals Numerical Model for Cavitational Flow in Hydraulic Poppet Valves

2012 ◽  
Vol 2012 ◽  
pp. 1-10 ◽  
Author(s):  
Sandor I. Bernad ◽  
Romeo Susan-Resiga
Keyword(s):  
Liquid Flow ◽  
Bubble Dynamics ◽  
Flow Analysis ◽  
Cavitating Flow ◽  
Absolute Pressure ◽  
Two Phase ◽  
Current Effort ◽  
Flow Models ◽  
Density Distributions ◽  
Phase Liquid

The paper presents a numerical simulation and analysis of the flow inside a poppet valve. First, the single-phase (liquid) flow is investigated, and an original model is introduced for quantitatively describing the vortex flow. Since an atmospheric outlet pressure produces large negative absolute pressure regions, a two-phase (cavitating) flow analysis is also performed. Both pressure and density distributions inside the cavity are presented, and a comparison with the liquid flow results is performed. It is found that if one defines the cavity radius such that up to this radius the pressure is no larger than the vaporization pressure, then both liquid and cavitating flow models predict the cavity extent. The current effort is based on the application of the recently developed full cavitation model that utilizes the modified Rayleigh-Plesset equations for bubble dynamics.

Numerical Simulation of Cavitating Flow Over 2D Hydrofoil Using OpenFOAM Adapted for Debian Operating System With LXDE Based in Kernel GNU/Linux

2014 ◽  
Author(s):  
Victor Hugo Hidalgo Diaz ◽  
XianWu Luo ◽  
RenFang Huang ◽  
Edgar Cando
Keyword(s):  
Operating System ◽  
Open Source ◽  
Open Source Software ◽  
Flow Analysis ◽  
Flow Characteristics ◽  
Cavitating Flow ◽  
Cavitating Flows ◽  
Ansys Fluent ◽  
Flow Features ◽  
Free Open Source

Though commercial CFD codes are widely used in flow analysis, but there are free/open source programs which have been applying for computational fluid dynamics. An open source software makes it possible to customize the solver according to the flow features. In the present paper, cavitating flows over 2D NACA66 hydrofoil were simulated based on open source software, where SALOME is used for mesh generation, OpenFOAM for flow solution under Debian GNU/Linux operating system. The results show the simulated cavitating flow characteristics such as cavity revolution, vortex shedding, cavitation induced pressure vibrations, etc. are validated by experiments and results obtained from proprietary software as Ansys Fluent. Thus, the proposed numerical methods based on open source platform are suitable for flow simulations, even for depicting the complicated physics of cavitation.

scholarly journals Numerical Study on the Influence of Step Casing on Cavitating Flows and Instabilities in Inducers with Equal and Varying Pitches

Processes ◽  
2020 ◽  
Vol 8 (9) ◽  
pp. 1103
Author(s):  
Lu Yu ◽  
Haochen Zhang ◽  
Hui Chen ◽  
Zhigang Zuo ◽  
Shuhong Liu
Keyword(s):  
Flow Field ◽  
Optimization Design ◽  
Numerical Study ◽  
Flow Characteristics ◽  
Cavitating Flow ◽  
Engineering Practice ◽  
Pressure Distributions ◽  
Significant Difference ◽  
Liquid Rocket ◽  
Safety And Stability

It is known that cavitating flow characteristics and instabilities in inducers can greatly impact the safety and stability of a liquid rocket. In this paper, step casing optimization design (Model OE and Model AE) was carried out for two three-bladed inducers with an equal (Model O) and a varying pitch (Model A), respectively. The unsteady cavitation flow field and accompanied instabilities were studied via numerical simulations. Reductions of the cavity size and fluctuation were observed in cases with a step casing. A significant difference in cavity structures was seen as well. Referring to the pressure distributions on the blades and details of the flow field, the mechanism of cavitation suppression was revealed. This work provides a feasible and convenient method in engineering practice for optimizing the characteristic of the cavitating flow field and instabilities for the inducer.

Cavitating Flow of Liquid Nitrogen in Horizontal Rectangular Nozzle

2003 ◽  
Author(s):  
Jun Ishimoto ◽  
Masahiro Onishi ◽  
Takashi Tokumasu ◽  
Kenjiro Kamijo
Keyword(s):  
Liquid Nitrogen ◽  
High Performance ◽  
Fluid Model ◽  
Flow Characteristics ◽  
Cavitating Flow ◽  
Two Phase ◽  
Cloud Cavitation ◽  
Rectangular Nozzle ◽  
Thermodynamic Effect ◽  
Two Fluid Model

The fundamental characteristics of the two-dimensional cavitating flow of liquid nitrogen through a horizontal rectangular nozzle are numerically and experimentally investigated to realize the further development and high performance of new multiphase cryogenic fluid applications. First, the governing equations of the cavitating flow of liquid nitrogen based on the unsteady thermal nonequilibrium two-fluid model are presented, and several flow characteristics are numerically calculated, taken into account the thermodynamic effect of cryogenic conditions. Next, the flow visualization measurement on unsteady cavitating flow of liquid nitrogen through a rectangular nozzle installed in a horizontal duct is carried out to clarify the basic cryogenic two-phase flow structure and fundamental characteristics of the transient growth process of cryogenic cloud cavitation.

Numerical Study of the Three-Dimensional Structure of a Bubble Plume

2000 ◽  
Vol 122 (4) ◽  
pp. 754-760 ◽  
Author(s):  
Y. Murai ◽  
Y. Matsumoto
Keyword(s):  
Numerical Study ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Lagrangian Model ◽  
Dimensional Structure ◽  
Bubble Motion ◽  
Bubble Plume ◽  
Two Phase ◽  
Simulated Flow ◽  
Good Agreement

The whole behavior and the micro scale flow characteristics of a three-dimensional bubble plume are investigated numerically. The bubble plume drives liquid convection in a tank due to strong local two-phase interaction so that the Eulerian-Lagrangian model is formulated with emphasis on the translational motions of the bubble. In this model, each bubble motion is tracked in a bubbly mixture which is treated as a continuum. The three-dimensional numerical results reveal several particular structures, such as swaying and swirling structures of the bubble plume. These simulated flow structures show qualitatively good agreement with the experimental observations. Furthermore, the detailed behavior in the bubble plume is clarified by various analysis to discuss the dominant factors causing such the strong three-dimensionality. [S0098-2202(00)00904-4]

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