scholarly journals Validation of a thermal non-equilibrium Eulerian-Eulerian multiphase model of a 620 MWe pulverized fuel power boiler

2021 ◽  
Vol 347 ◽  
pp. 00004
Author(s):  
Brad Rawlins ◽  
Ryno Laubscher ◽  
Pieter Rousseau
Keyword(s):  
Heat Fluxes ◽  
Multiphase Model ◽  
Eulerian Model ◽  
Combustion Dynamics ◽  
Pulverized Fuel ◽  
Fuel Particles ◽  
Flexible Operation ◽  
Power Boiler ◽  
Modelling Approach ◽  
Non Equilibrium

The use of a thermal non-equilibrium Eulerian-Eulerian model for the simulation of a 620 MWe power boiler is proposed for capturing the combustion and radiative heat transfer found in the pulverized fuel systems. The models eliminates the use of a Lagrangian reference frame in tracking solid fuel particles thereby reducing the computational expense and time. The model solves the scalar transport for the particle mass, energy and radiation interactions between the pseudo-particle and continuous phases. The goal is to apply the modelling approach to generate a simulation database for different load cases and firing conditions which in turn will be used to study flexible operation. The model is validated against both numerical and applicable site data measurements. It is shown that the model is able to adequately resolve the furnace and superheater wall heat fluxes. Additionally the resolution of the flow field, combustion dynamics and wall fluxes are demonstrated for both an 80% and 60% operational loads. Moreover, it is shown that the Eulerian-Eulerian model results in approximately a 30% computational resource reduction when compared to traditional modelling approaches.

scholarly journals ASHEE-1.0: a compressible, equilibrium–Eulerian model for volcanic ash plumes

2016 ◽  
Vol 9 (2) ◽  
pp. 697-730 ◽  
Author(s):  
M. Cerminara ◽  
T. Esposti Ongaro ◽  
L. C. Berselli
Keyword(s):  
Numerical Simulation ◽  
Large Scale ◽  
Volume Fraction ◽  
Radial Profile ◽  
Air Entrainment ◽  
Compressible Turbulence ◽  
Eulerian Model ◽  
Volcanic Plumes ◽  
Large Eddy ◽  
Non Equilibrium

Abstract. A new fluid-dynamic model is developed to numerically simulate the non-equilibrium dynamics of polydisperse gas–particle mixtures forming volcanic plumes. Starting from the three-dimensional N-phase Eulerian transport equations for a mixture of gases and solid dispersed particles, we adopt an asymptotic expansion strategy to derive a compressible version of the first-order non-equilibrium model, valid for low-concentration regimes (particle volume fraction less than 10−3) and particle Stokes number (St – i.e., the ratio between relaxation time and flow characteristic time) not exceeding about 0.2. The new model, which is called ASHEE (ASH Equilibrium Eulerian), is significantly faster than the N-phase Eulerian model while retaining the capability to describe gas–particle non-equilibrium effects. Direct Numerical Simulation accurately reproduces the dynamics of isotropic, compressible turbulence in subsonic regimes. For gas–particle mixtures, it describes the main features of density fluctuations and the preferential concentration and clustering of particles by turbulence, thus verifying the model reliability and suitability for the numerical simulation of high-Reynolds number and high-temperature regimes in the presence of a dispersed phase. On the other hand, Large-Eddy Numerical Simulations of forced plumes are able to reproduce the averaged and instantaneous flow properties. In particular, the self-similar Gaussian radial profile and the development of large-scale coherent structures are reproduced, including the rate of turbulent mixing and entrainment of atmospheric air. Application to the Large-Eddy Simulation of the injection of the eruptive mixture in a stratified atmosphere describes some of the important features of turbulent volcanic plumes, including air entrainment, buoyancy reversal and maximum plume height. For very fine particles (St → 0, when non-equilibrium effects are negligible) the model reduces to the so-called dusty-gas model. However, coarse particles partially decouple from the gas phase within eddies (thus modifying the turbulent structure) and preferentially concentrate at the eddy periphery, eventually being lost from the plume margins due to the concurrent effect of gravity. By these mechanisms, gas–particle non-equilibrium processes are able to influence the large-scale behavior of volcanic plumes.

An Upwind Eulerian-Eulerian Model for Non-Equilibrium Condensation in Steam Turbines

2013 ◽  
Author(s):  
Xiaofeng Zhu ◽  
Xin Yuan ◽  
Zhirong Lin ◽  
Naoki Shibukawa ◽  
Tomohiko Tsukuda ◽  
...  
Keyword(s):  
Current Model ◽  
Finite Volume Scheme ◽  
Steam Turbines ◽  
Turbine Cascade ◽  
Wet Steam ◽  
Turbine Stage ◽  
Eulerian Model ◽  
Two Phase ◽  
Eigen Value ◽  
Non Equilibrium

The present paper proposes an Eulerian-Eulerian two-phase model for non-equilibrium condensing flow in steam turbines. This model is especially suitable for upwind finite volume scheme. An approximate Roe type flux using real water/vapor property is constructed to calculate the upwind wet-steam flux. This flux fully couples the wetness fraction with other conservative variables in the Jacobian Matrix whose eigen-vector and eigen-value are analitically derived. A novel treatment of real wet-steam property is developed by constructing a 3-DOFs TTSE table according to IAPWS97 formulas. The table is actually a cubic and uses the mixture’s density, the mixture’s internal energy and wetness as independent variables. Besides homogeneous condensation, heterogeneous condensing is also integrated into the model, which facilitates simulating the effect of salt impurities. The above methods are validated through two nozzle and one turbine cascade calculations and finally applied to a model LP steam turbine stage. Results show that the current model is very robust and is able to correctly capture the non-equilibrium condensation phenomena.

Temperature profiles and heat fluxes observed in molecular dynamics simulations of force-driven liquid flows

2017 ◽  
Vol 19 (16) ◽  
pp. 10317-10325 ◽  
Author(s):  
Jafar Ghorbanian ◽  
Ali Beskok
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Md Simulations ◽  
Heat Fluxes ◽  
Temperature Profiles ◽  
Non Equilibrium Molecular Dynamics ◽  
Dynamics Simulations ◽  
Liquid Flows ◽  
Non Equilibrium

This paper concentrates on the unconventional temperature profiles and heat fluxes observed in non-equilibrium molecular dynamics (MD) simulations of force-driven liquid flows in nano-channels.

scholarly journals Comparative Study of Mixture Model and Eulerian Model Used in Hydrocyclone with the Help of CFD Simulation

2020 ◽  
Author(s):  
Indrashis Saha ◽  
Tathagata Mukherjee
Keyword(s):  
Fluid Flow ◽  
Mixture Model ◽  
Particle Motion ◽  
Numerical Study ◽  
Research Work ◽  
Tangential Velocity ◽  
Volume Of Fluid ◽  
Slight Variation ◽  
Multiphase Model ◽  
Eulerian Model

Due to the accuracy of numerical calculation of fluid flow inside a hydrocyclone can be obtained using Computational Fluid Dynamics (CFD), highly modified super computers are used to simulate the fluid flow and track particle motion inside a hydrocyclone. This paper deals with the numerical study using three multiphase models viz. Volume of fluid, Mixture and Eulerian model. The dimensions of the hydrocyclone taken into consideration for numerical analysis is same as considered by Rajamani. Validation of axial and tangential velocities at different strategically decided axial stations, RMS axial and tangential velocity profiles of the hydrocyclone is done using Reynolds Stress Model (RSM). The hydrocyclone model has been designed in Creo 3.0 using the same dimensions which later was imported to CFD for meshing. Fine hexagonal mesh numbering up to 5 lacs were constructed to obtain optimum results. Fluid flow was allowed to be developed in ANSYS FLUENT 16.2. Entire simulation took 96 hours to generate results and track particle movements inside the hydrocyclone. The particle tracking has been done using three multiphase model. The first being the volume of fluid was used for validation purposes and the comparison of the Mixture and Eulerian model are the basic focus of this research work. Conclusive results indicate that usage of different multiphase model does not result in variation in particle motion. The slight variation in grade efficiency values are hardly noticeable. The Mixture model and Eulerian model predict lower separation efficiency as compared with Volume of fluid multiphase model.

Multiphase modeling study for storm water solids treatment in experimental storm water settling chamber

2011 ◽  
Vol 63 (12) ◽  
pp. 3020-3026 ◽  
Author(s):  
Jungseok Ho
Keyword(s):  
Reference Frame ◽  
Particle Motion ◽  
Coupled Model ◽  
Storm Water ◽  
Computational Time ◽  
Settling Chamber ◽  
Multiphase Model ◽  
Coupled Models ◽  
Eulerian Model ◽  
Discrete Phase

This study tests four different types of multiphase models to determine the most appropriate model for predicting the behaviors of various types of storm water solids in a settling chamber. The Lagrangian reference frame discrete phase models of uncoupled and coupled models based on the interaction between the discrete phase and the continuous phase were tested. The rigid moving objects model providing six degrees of freedom particle motion was also tested to model non-spherical particle motion. The fourth model was a sediment transport model using the Eulerian reference frame model. This study tested five different storm water solids consisting of bulk, gross, coarse, sediment and fine which are classified by particle size and settling characteristics. Particle settling efficiency and computational time were considered in determining the most appropriate multiphase model. The coupled model provided better solid settling than the uncoupled model, but required 8.2% more computational time in this study. The Eulerian model matched settling efficiency for the high density finer solids. Although the Eulerian model showed reliable settling prediction, the Lagrangian coupled model can be an effective alternative requiring significantly reduced computational time.

Experimental studies of ignition behaviour and combustion reactivity of pulverized fuel particles

Fuel ◽  
1992 ◽  
Vol 71 (11) ◽  
pp. 1239-1246 ◽  
Author(s):  
Dong-ke Zhang ◽  
Terry F. Wall ◽  
David J. Harris ◽  
Ian W. Smith ◽  
Jianyuan Chen ◽  
...  
Keyword(s):  
Experimental Studies ◽  
Pulverized Fuel ◽  
Fuel Particles ◽  
Combustion Reactivity

Diphasic transfer of oxygen in vertical flow filters: a modelling approach

2011 ◽  
Vol 64 (1) ◽  
pp. 109-116 ◽  
Author(s):  
A. Petitjean ◽  
A. Wanko ◽  
N. Forquet ◽  
R. Mosé ◽  
F. Lawniczak ◽  
...  
Keyword(s):  
Multiphase Model ◽  
Vertical Flow ◽  
Treatment Efficiency ◽  
Two Phase ◽  
Convection Diffusion ◽  
First Order ◽  
First Order Kinetics ◽  
First Results ◽  
Diffusion Phenomena ◽  
Modelling Approach

Oxygen renewal, as a prominent phenomenon for aerobic bacterial activity, deeply impacts vertical flow constructed wetland (VFCW) treatment efficiency. The authors introduce a multiphase model able to simulate oxygen transfer in VFCWs. It is based on a two-phase flow module, and a transport module. The transport module is able to deal with convection/diffusion phenomena, inter-phase (air–water) mass exchange, and first-order kinetics. The first results displayed for the air phase allow us to draw the following ideas on the design of vertical filters. The ponding phenomenon is more efficient for oxygen renewal than non-ponding batch loading: it provides a higher value, sooner, and deeper in the filter. In non-colonised filters and for standard batch loading, oxygen convection in the air phase is predominant for oxygen renewal. The seepage front limits oxygen renewal through the bottom of the filter and leads to an insufficient oxygen concentration on the lowest part of the filter.

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