Review on modelling approaches based on computational fluid dynamics for biomass combustion systems

2019 ◽  
Vol 9 (1) ◽  
pp. 129-182 ◽  
Author(s):  
Andrea Dernbecher ◽  
Alba Dieguez-Alonso ◽  
Andreas Ortwein ◽  
Fouzi Tabet
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Biomass Combustion ◽  
Combustion Systems ◽  
Modelling Approaches

Computational Modelling of Self-Excited Combustion Instabilities

2000 ◽  
Author(s):  
Steve J. Brookes ◽  
R. Stewart Cant ◽  
Iain D. J. Dupere ◽  
Ann P. Dowling
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Heat Release ◽  
Large Scale ◽  
Computational Modelling ◽  
Combustion Efficiency ◽  
Design Tool ◽  
Premixed Combustion ◽  
Combustion Instabilities ◽  
Combustion Systems

It is well known that lean premixed combustion systems potentially offer better emissions performance than conventional non-premixed designs. However, premixed combustion systems are more susceptible to combustion instabilities than non-premixed systems. Combustion instabilities (large-scale oscillations in heat release and pressure) have a deleterious effect on equipment, and also tend to decrease combustion efficiency. Designing out combustion instabilities is a difficult process and, particularly if many large-scale experiments are required, also very costly. Computational fluid dynamics (CFD) is now an established design tool in many areas of gas turbine design. However, its accuracy in the prediction of combustion instabilities is not yet proven. Unsteady heat release will generally be coupled to unsteady flow conditions within the combustor. In principle, computational fluid dynamics should be capable of modelling this coupled process. The present work assesses the ability of CFD to model self-excited combustion instabilities occurring within a model combustor. The accuracy of CFD in predicting both the onset and the nature of the instability is reported.

A Computational Study of a Biomass Cookstove With Forced Secondary Air Injection

2020 ◽  
Author(s):  
Liam Cassidy ◽  
Nordica MacCarty
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Air Quality ◽  
Thermal Efficiency ◽  
Air Flow ◽  
Air Injection ◽  
Biomass Combustion ◽  
Secondary Air Injection ◽  
Forced Draft ◽  
Secondary Air

Abstract The use of solid biomass as a primary energy source for cooking is common to nearly half of the world’s population. Household air pollution as a byproduct of biomass combustion creates powerful negative health impacts related to air quality and a strong influence on our global radiative balance. Despite efforts to improve biomass-fueled cooking technology, many current designs still fail to meet WHO guidelines for air quality and consume excessive fuel. One promising method to improve in both of these areas is through introduction of forced primary or secondary air to the combustion process to increase turbulence, mixing, and velocity. Incorporating computational fluid dynamics to the design process for this forced draft air flow can provide insights into the complex and interconnected thermophysical relationships which, otherwise, would require extensive experimentation. The objective of this work is to provide a preliminary computational fluid dynamics study of a secondary air forced draft biomass cookstove. Thermal efficiency and emissions concentrations are investigated relative to various combinations of secondary air flow rates and injection angles. The results from the case study suggest that thermal efficiency of the cookstove is a function of secondary air injection angle, with optimal angle being a function of the specific air-fuel ratio. Additionally, a design trade-off is evident when comparing the pollutant concentration data and thermal efficiency data. Lastly, analysis of the computational results suggests that large pressure gradients about secondary air vortices in the combustion chamber lead to improved thermal efficiency and more complete combustion. The continued development of this work into an open-source computational fluid dynamics tool is underway.

scholarly journals Computational fluid dynamics analysis of cyclist aerodynamics: Performance of different turbulence-modelling and boundary-layer modelling approaches

2010 ◽  
Vol 43 (12) ◽  
pp. 2281-2287 ◽  
Author(s):  
Thijs Defraeye ◽  
Bert Blocken ◽  
Erwin Koninckx ◽  
Peter Hespel ◽  
Jan Carmeliet
Keyword(s):  
Fluid Dynamics ◽  
Boundary Layer ◽  
Computational Fluid Dynamics ◽  
Turbulence Modelling ◽  
Dynamics Analysis ◽  
Computational Fluid Dynamics Analysis ◽  
Modelling Approaches

Integrated Approach to Multiphase Flow Regime Prediction Through Computational Fluid Dynamics CFD

2021 ◽  
Author(s):  
Matt Straw ◽  
Ravindra Aglave ◽  
Rodolfo Piccioli
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Multiphase Flow ◽  
Case Studies ◽  
Cfd Simulation ◽  
Process Systems ◽  
Computational Fluid Dynamics Cfd ◽  
And Performance ◽  
Modelling Methods ◽  
Modelling Approaches

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.

Computational Modeling of Self-Excited Combustion Instabilities

2001 ◽  
Vol 123 (2) ◽  
pp. 322-326 ◽  
Author(s):  
S. J. Brookes ◽  
R. S. Cant ◽  
I. D. J. Dupere ◽  
A. P. Dowling
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Heat Release ◽  
Large Scale ◽  
Combustion Efficiency ◽  
Design Tool ◽  
Premixed Combustion ◽  
Combustion Instabilities ◽  
Lean Premixed Combustion ◽  
Combustion Systems

It is well known that lean premixed combustion systems potentially offer better emissions performance than conventional non-premixed designs. However, premixed combustion systems are more susceptible to combustion instabilities than non-premixed systems. Combustion instabilities (large-scale oscillations in heat release and pressure) have a deleterious effect on equipment, and also tend to decrease combustion efficiency. Designing out combustion instabilities is a difficult process and, particularly if many large-scale experiments are required, also very costly. Computational fluid dynamics (CFD) is now an established design tool in many areas of gas turbine design. However, its accuracy in the prediction of combustion instabilities is not yet proven. Unsteady heat release will generally be coupled to unsteady flow conditions within the combustor. In principle, computational fluid dynamics should be capable of modeling this coupled process. The present work assesses the ability of CFD to model self-excited combustion instabilities occurring within a model combustor. The accuracy of CFD in predicting both the onset and the nature of the instability is reported.

Comparison of Modelling Approaches for Bump-Type Foil Thrust Bearings Operating With CO2

2018 ◽  
Author(s):  
Kan Qin ◽  
Daijin Li ◽  
Kai Luo ◽  
Zhansheng Tian ◽  
Ingo H. Jahn
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Rotational Speed ◽  
Temperature Increase ◽  
Reynolds Equation ◽  
Structural Deformation ◽  
Viscous Heating ◽  
Thrust Bearings ◽  
Dynamics Method ◽  
Modelling Approaches

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.

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