scholarly journals Mathematical Modeling of Non-Premixed Laminar Flow Flames Fed with Biofuel in Counter-Flow Arrangement Considering Porosity and Thermophoresis Effects: An Asymptotic Approach

Energies ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2945 ◽  
Author(s):  
Mehdi Bidabadi ◽  
Peyman Ghashghaei Nejad ◽  
Hamed Rasam ◽  
Sadegh Sadeghi ◽  
Bahman Shabani
Keyword(s):  
Laminar Flow ◽  
Solid Phase ◽  
Medical Systems ◽  
Safe Operation ◽  
Counter Flow ◽  
Thermophoretic Force ◽  
Mass Fractions ◽  
Premixed Laminar ◽  
Organic Particles ◽  
Flame Sheet

Due to the safe operation and stability of non-premixed combustion, it can widely be utilized in different engineering power and medical systems. The current paper suggests a mathematical asymptotic technique to describe non-premixed laminar flow flames formed in organic particles in a counter-flow configuration. In this investigation, fuel and oxidizer enter the combustor from opposite sides separately and multiple zones including preheating, vaporization, flame and post-flame zones were considered. Micro-sized lycopodium particles and air were respectively applied as a biofuel and an oxidizer. Dimensionalized and non-dimensionalized mass and energy conservation equations were determined for the zones and solved by Mathematica and Matlab software by applying proper boundary and jump conditions. Since lycopodium particles have numerous spores, the porosity of the particles was involved in the equations. Further, significant parameters such as lycopodium vaporization rate and thermophoretic force corresponding to the lycopodium particles in the solid phase were examined. The temperature distribution, flame sheet position, fuel and oxidizer mass fractions, equivalence ratio and flow strain rate were evaluated for the counter-flow non-premixed flames. Ultimately, the thermophoretic force caused by the temperature gradient at different positions was computed for several values of porosity, fuel and oxidizer Lewis numbers.

Mathematical modeling of the production of magnetic nanoparticles through counter-flow non-premixed combustion for biomedical applications

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Shahin Akbari ◽  
Nima Hasanvand ◽  
Sadegh Sadeghi ◽  
Mehdi Bidabadi ◽  
Qingang Xiong
Keyword(s):  
Magnetic Nanoparticles ◽  
Large Scale ◽  
Flame Temperature ◽  
Combustion Process ◽  
Premixed Combustion ◽  
Counter Flow ◽  
Content Type ◽  
Thermophoretic Force ◽  
Mass Fractions ◽  
Carrier Gases

Purpose The widespread usage of magnetic nanoparticles (MNPs) requires their efficient synthesis during combustion process. This study aims to present a mathematical model for the oxidation of MNPs in a counter-flow non-premixed combustion system to produce MNPs, where the key sub-processes during the oxidation reaction are involved. Design/methodology/approach To accurately describe structure of flame and determine distributions of temperature and mass fractions of both reactants and products, equations of energy and mass conservations were solved based on the prevailing assumptions that three regions, i.e. preheating, reaction and oxidizer zones exist. Findings The numerical simulation was first validated against experimental data and characteristics of the combustion process are discussed. Eventually, the influences of crucial parameters such as reactant Lewis numbers, strain rate ratio, particle size, inert gas and thermophoretic force on structure of flame and combustion behavior were examined. The results show that maximum flame temperature can achieve 2,205 K. Replacing nitrogen with argon and helium as carrier gases can increase flame temperature by about 27% and 34%, respectively. Additionally, maximum absolute thermophoretic force was found at approximately 9.6 × 10–8 N. Originality/value To the best of authors’ knowledge, this is the first time to numerically model the preparation of MNPs in a counter-flow non-premixed combustion configuration, which can guide large-scale experimental work in a more effective way.

An asymptotic analysis for detailed mathematical modeling of counter-flow non-premixed multi-zone laminar flames fueled by lycopodium particles

2019 ◽  
Vol 30 (4) ◽  
pp. 2137-2168 ◽  
Author(s):  
Mehdi Bidabadi ◽  
Sadegh Sadeghi ◽  
Pedram Panahifar ◽  
Davood Toghraie ◽  
Alireza Rahbari
Keyword(s):  
Mathematical Modeling ◽  
Asymptotic Method ◽  
Flame Temperature ◽  
Laminar Flames ◽  
Counter Flow ◽  
Content Type ◽  
Front Position ◽  
Mass Fractions ◽  
Premixed Laminar ◽  
Fuel Particles

Purpose This study aims to present a basic mathematical model for investigating the structure of counter-flow non-premixed laminar flames propagating through uniformly-distributed organic fuel particles considering preheat, drying, vaporization, reaction and oxidizer zones. Design/methodology/approach Lycopodium particles and air are taken as biofuel and oxidizer, respectively. Dimensionalized and non-dimensionalized forms of mass and energy conservation equations are derived for each zone taking into account proper boundary and jump conditions. Subsequently, to solve the governing equations, an asymptotic method is used. For validation purpose, results achieved from the present analysis are compared with reliable data reported in the literature under certain conditions. Findings With regard to the comparisons, although different complex non-homogeneous differential equations are solved in this paper, acceptable agreements are observed. Finally, the impacts of significant parameters including fuel and oxidizer Lewis numbers, equivalence ratio, mass particle concentration, fuel and oxidizer mass fractions and lycopodium initial temperature on the flame temperature, flame front position and flow strain rate are elaborately explained. Originality/value An asymptotic method for mathematical modeling of counter-flow non-premixed multi-zone laminar flames propagating through lycopodium particles.

An Investigation of Steady Wall-Ceiling and Partial Enclosure Fires

1984 ◽  
Vol 106 (1) ◽  
pp. 221-228 ◽  
Author(s):  
C.-P. Mao ◽  
A. C. Fernandez-Pello ◽  
J. A. C. Humphrey
Keyword(s):  
Numerical Model ◽  
Laminar Flow ◽  
Radiation Transport ◽  
Turbulent Transport ◽  
Qualitative Description ◽  
Significant Discrepancy ◽  
Fire Hazards ◽  
First Case ◽  
Flame Sheet ◽  
Prediction Approach

A numerical model has been developed to: (a) study the buoyancy-driven combusting flows of partial enclosure fires and (b) to help assess the fire hazards of different burning materials. The calculations provide the flow patterns and distributions of velocity, temperature, species concentration, and flame location in the flow. The model assumes steady laminar flow and makes use of the flame sheet approximation to describe the gas-phase chemical reaction. In corresponding experiments, photographic determinations of flame location were made. Two different cases were studied: (i) a fire occurring in a wall-ceiling configuration with variable pyrolyzing length (of PMMA material); and (ii) a partial enclosure fire with variable soffit and pyrolyzing lengths (the latter of PMMA or POM materials). Good agreement was obtained between measurements and calculations of the flame location for the first case. However, a significant discrepancy was found for the second case and is attributed to the neglect of turbulence and radiation transport in the model. Notwithstanding these limitations, it is found that a simple laminar flow model provides a correct qualitative description of the evolution of partial enclosure fires. For example, stratified (layered) motions, recirculation zones and the so-called “firewind” are correctly predicted as a function of pyrolysis and soffit lengths. The present approach, of incorporating physico-chemical parameters and boundary conditions of practical systems into a numerical model for assessing fire hazards, is very attractive due to its relative ease of execution. The accuracy of the numerical prediction approach can be improved by including radiation and turbulent transport.

Laminar flow and heat transfer in a quasi-counter flow parallel-plate membrane channel (QCPMC)

2015 ◽  
Vol 86 ◽  
pp. 890-897 ◽  
Author(s):  
Si-Min Huang ◽  
Minlin Yang ◽  
Baiman Chen ◽  
Runhua Jiang ◽  
Frank G.F. Qin ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Laminar Flow ◽  
Parallel Plate ◽  
Membrane Channel ◽  
Counter Flow ◽  
Flow And Heat Transfer

scholarly journals In situ TDLAS measurement of absolute acetylene concentration profiles in a non-premixed laminar counter-flow flame

2012 ◽  
Vol 107 (3) ◽  
pp. 585-589 ◽  
Author(s):  
S. Wagner ◽  
M. Klein ◽  
T. Kathrotia ◽  
U. Riedel ◽  
T. Kissel ◽  
...  
Keyword(s):  
Concentration Profiles ◽  
Counter Flow ◽  
Premixed Laminar

scholarly journals Context-aware medical technologies - relief or burden for clinical users?

2018 ◽  
Vol 4 (1) ◽  
pp. 119-122
Author(s):  
Thomas Neumuth ◽  
Max Rockstroh ◽  
Stefan Franke
Keyword(s):  
Working Environment ◽  
Context Aware ◽  
Medical Systems ◽  
Enabling Technology ◽  
Safe Operation ◽  
Clinical Routine ◽  
Medical Technologies ◽  
Open Research ◽  
Biomedical Systems ◽  
Research Questions

AbstractThe open, cross-vendor interoperability of medical devices is an enabling technology for the implementation of context-aware biomedical systems in daily clinical routine. The surgical working environment is both a valuable field of application and a particular challenge. A design of context-aware medical technologies that shows intelligent behaviour and ensures safe operation is demanding; thus implementations are yet limited to prototypes and specific surgical use cases. Many open research questions need to be addressed to empower context-aware medical systems to be a relief and not a burden for the clinical user.

Quench Sensitivity and Continuous Cooling Precipitation Diagrams

2019 ◽  
Author(s):  
Olaf Kessler ◽  
Benjamin Milkereit ◽  
Christoph Schick
Keyword(s):  
Phase Transformations ◽  
Solid Phase ◽  
Secondary Phase ◽  
Scanning Calorimetry ◽  
Technical Application ◽  
Continuous Cooling ◽  
Quench Sensitivity ◽  
Heating And Cooling ◽  
Physically Based ◽  
Mass Fractions

The application properties of metallic materials are frequently adjusted by heat treatments utilizing controlled microstructural changes—i.e., solid–solid phase transformations like nondiffusional martensitic transformation or diffusional secondary phase precipitation and/or dissolution. For technical application, knowledge about the characteristic temperatures and times but moreover about their time dependence (kinetics) is required. As the relevant solid–solid phase transformations all show a heat effect (e.g., precipitation → exothermic; dissolution → endothermic), one outstanding measurement technique to follow these phase transformations is calorimetry, particularly differential scanning calorimetry (DSC). Appropriate combinations of DSC methods and devices to cover nine orders of magnitude in heating and cooling rates (10−4–105 K/s) will be introduced, using dissolution and precipitation reactions in aluminum alloys as examples. Basically, these techniques allow one to record time–temperature transformation (or precipitation/dissolution) diagrams for various materials during heating, isothermal annealing, and even during continuous cooling, making DSC a very powerful tool for the investigation of solid–solid phase transformations. Nowadays, physically based models verified with DSC results moreover allow one to predict precipitation volume fractions and solute mass fractions.

scholarly journals Hygroscopicity of organic surrogate compounds from biomass burning and their effect on the efflorescence of ammonium sulfate in mixed aerosol particles

2017 ◽  
Author(s):  
Ting Lei ◽  
Andreas Zuend ◽  
Yafang Cheng ◽  
Hang Su ◽  
Weigang Wang ◽  
...  
Keyword(s):  
Growth Factors ◽  
Humic Acid ◽  
Relative Humidity ◽  
Ammonium Sulfate ◽  
Biomass Burning ◽  
Solid Phase ◽  
Aerosol Particles ◽  
Diameter Growth ◽  
Hydroxybenzoic Acid ◽  
Mass Fractions

Abstract. Hygroscopic growth factors of organic surrogate compounds representing biomass burning and mixed organic-inorganic aerosol particles exhibit variability during dehydration experiments depending on their chemical composition, which we observed using a hygroscopicity tandem differential mobility analyzer (HTDMA). We observed that levoglucosan and humic acid aerosol particles release water slightly in the range of 90–5 % relative humidity (RH). 4-Hydroxybenzoic acid aerosol particles, however, remain in the solid state without diameter growth and even slightly shrinking at higher RH compared to the dry size. The measurements were accompanied by RH-dependent thermodynamic equilibrium calculations using the AIOMFAC and the E-AIM models, the ZSR relation, and a fitted hygroscopicity expression. We observed several effects of organic components on the hygroscopicity behavior of mixtures containing ammonium sulfate (AS) in relation to the different mass fractions of organic compounds: (1) a shift of efflorescence relative humidity (ERH) of ammonium sulfate to higher RH due to the presence of 25 wt % levoglucosan in the mixture. (2) There is a distinct efflorescence transition at 25 % RH for mixtures consisting of 25 wt % of 4-hydroxybenzoic acid compared to the ERH at 35 % for organic-free AS particles. (3) There is indication for a liquid-to-solid phase transition of 4-hydroxybenzoic acid in the mixed particles during dehydration. (4) A humic acid component shows no significant effect on the efflorescence of AS in mixed aerosol particles. In addition, relatively good measurement-model agreement in the case of the AIOMFAC and E-AIM models is mainly due to composition-dependent consideration of crystallization of AS in the model prediction. The use of the ZSR relation leads to good agreement with measured diameter growth factors of aerosol particles containing humic acid and ammonium sulfate. A similarity of the hygroscopicity parameter ĸ for organic surrogate compounds mixed with ammonium sulfate for different mass fractions during the different seasonal periods in the Amazon is observed. The RH-dependent hygroscopicity parameter ĸ measured at sub-saturated is consistent with kappa values for observations in the central Amazon Basin at the same environment, which suggests the similar O : C ratios and ammonium sulfate mass fraction in the laboratory and field observation conditions.

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