scholarly journals Review on Modelling Approaches Based on Computational Fluid Dynamics for Biomass Pyrolysis Systems

Author(s):  
Przemysław Maziarka ◽  
Frederik Ronsse ◽  
Andrés Anca-Couce
Energy ◽  
2021 ◽  
Vol 214 ◽  
pp. 118839
Author(s):  
Shiliang Yang ◽  
Ruihan Dong ◽  
Yanxiang Du ◽  
Shuai Wang ◽  
Hua Wang

2021 ◽  
Author(s):  
Matt Straw ◽  
Ravindra Aglave ◽  
Rodolfo Piccioli

Abstract This paper presents recent advances in multiphase modelling methods in Computational Fluid Dynamics (CFD). It uses case studies to show how integration of advanced multiphase modelling approaches can improve the fidelity and realism of simulation of separation and process systems; helping improve design and performance. CFD has been widely used to aid the design and operational performance of many separation and multiphase production and process systems; often providing significant insight and performance improvement. Traditionally, numerous compromises or simplifications must be made when simulating complex multiphase flows and their transitions within production and separation systems using CFD. For example, the modelling methods applicable to capture gas-liquid or liquid-liquid interface behaviour are not suitable (or practical) to also capture gas columns, liquid films or liquid entrainment phenomena, that may be important to quantifying overall system performance. To accommodate different multiphase phenomena and flow regimes, multiple CFD simulations or approaches have often been required. This can limit the insight or fidelity of a given simulation or, in some cases, mean overall performance cannot be fully quantified (even though useful performance indicators may still be identified). Here, the authors present advances in hybrid multiphase modelling and how integration of multiphase modelling approaches enables multiple multiphase flow regimes and their transition to be captured through CFD simulation. The paper will demonstrate how these advances enables simulation of more complex behaviours with increased fidelity. Examples, case studies and validation cases are presented demonstrating phenomena including bulk liquid interface break-up, liquid film formation and entrainment of droplets plus their break—up and deposition. The examples will be presented in the context of the improvements possible in simulation fidelity and realism, of multiphase systems, and how this can impact the insight and value gained from CFD simulation in this complex field. The work presented shows how new developments and evolution of CFD-based predictions can advance how the industry uses this approach and the value that can be obtained. It highlights how integration of the most advanced modelling approaches and methods is key to the next stage of application of CFD to enable better representation of the full range of fluid mechanics that are critical to many separation and multiphase system designs and performance.


Author(s):  
Kan Qin ◽  
Daijin Li ◽  
Kai Luo ◽  
Zhansheng Tian ◽  
Ingo H. Jahn

Different forms of Reynolds equation are widely used to predict the performances of foil thrust bearings for air cycle machines. When analyzing bearings operating with highly dense CO2, computational fluid dynamics yields more accurate results, particularly at the high rotational speed. In addition, the structural deformation of the top and bump foils are also considered. For some applications, the high temperature increase caused by the viscous heating effect are also modelled in literature. The multi-physics effects within foil bearings, including the fluid flow, structural deformation and viscous heating create challenges and modelling complexity to accurately predict its performances. The aim of this paper is to review and compare different modelling approaches for foil thrust bearings with CO2 at a range of operating conditions, including loads and rotational speed. For steady state performances, results from turbulent Reynolds equation and computational fluid dynamics are in close agreement for foil thrust bearings operating with low load (large rotor to top foil separations). However, considerable differences exist between turbulent Reynolds equation and computational fluid dynamics method at high loads (small rotor to top foil separation). Here the computational fluid dynamics method must be employed, as the centrifugal inertia effect becomes significant. The top foil deflection need to be considered as the corresponding deformation is significant compared to the initial separation between the rotor and the top foil. At the rotational speed larger than 30000 rpm, the results from the fully fluid-structure-thermal simulations differ from other modelling approaches. The additional deformation caused by temperature increase largely alters the separation between the rotor and top foil. For dynamic performance, the top foil deflection again must be considered as the equivalent stiffness and damping are influenced by bump foil structures. This work provides recommendations for the selection of the suitable modelling approaches for bump-type foil thrust bearings operating with supercritical CO2.


2017 ◽  
Vol 5 (4) ◽  
pp. 2783-2798 ◽  
Author(s):  
Qingang Xiong ◽  
Yang Yang ◽  
Fei Xu ◽  
Yaoyu Pan ◽  
Jingchao Zhang ◽  
...  

Sign in / Sign up

Export Citation Format

Share Document