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Dal Belo Takehara, M., Umeki, K. & Gebart, R. (2024). Investigation of oxygen-enriched biomass flames in a lab-scale entrained flow reactor. Fuel, 366, Article ID 131343.
Open this publication in new window or tab >>Investigation of oxygen-enriched biomass flames in a lab-scale entrained flow reactor
2024 (English)In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 366, article id 131343Article in journal (Refereed) Published
Abstract [en]

Oxygen-enriched air combustion of pulverized biomass fuel is an effective method to improve char combustion and improve flame stability. Moreover, understanding the impact of O2 addition is an important step toward oxyfuel combustion, one of the most promising technologies for bioenergy with carbon capture and storage (BECCS). Our previous studies focused on flow manipulation methods, e.g., swirling co-flow and acoustic forcing, to enhance particle dispersion during biomass combustion and gasification. This work aims to extend the understanding of the effect of different manipulation methods on oxygen-enriched combustion at different levels in a lab-scale entrained flow reactor. This methodology combines the analysis of visible flame characteristics, CO and NO gas emissions, and coarse particle emissions characterization with thermogravimetric analysis and particle size distribution by dynamic imaging. The results indicated that oxygen-enriched combustion leads to lower liftoff distance and higher flame brightness. Moreover, oxygen-enriched combustion presented coarse particle emissions with finer particle size distribution and lower carbon content. The acoustic forcing further decreased the flame liftoff and decreased CO emissions, increasing combustion efficiency under conditions with similar equivalence ratios and lower momentum flux at the secondary air.

Place, publisher, year, edition, pages
Elsevier, 2024
Keywords
Pulverized fuel, Biomass, Acoustic excitation, Oxygen-enrichment, Combustion
National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-104555 (URN)10.1016/j.fuel.2024.131343 (DOI)2-s2.0-85186518924 (Scopus ID)
Funder
Swedish Energy Agency, 47485-1The Kempe Foundations, SMK-1632
Note

Validerad;2024;Nivå 2;2024-04-02 (joosat);

Full text: CC BY License

Available from: 2024-03-12 Created: 2024-03-12 Last updated: 2024-04-02Bibliographically approved
Gebart, R. (2024). Thermal runaway criterion for thick polymer composites. Composites. Part A, Applied science and manufacturing, 182, Article ID 108187.
Open this publication in new window or tab >>Thermal runaway criterion for thick polymer composites
2024 (English)In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 182, article id 108187Article in journal (Refereed) Published
Abstract [en]

An analytical solution has been developed for the curing of thick polymer composite laminates that shows how the temperature profile responds to arbitrary changes to the material properties and process parameters and that curing with slow reactions and a low exotherm temperature is impossible if the Damköhler number is above a well-defined limit. The thermal runaway criterion can be recast as a criterion for the maximum allowable thickness of the laminate. The thermal runaway criterion was found to agree well with some results for thick laminates from the literature, but the peak temperature in the laminate was underpredicted for stable conditions. The model has a constant that can be adjusted to improve the peak temperature prediction, but more validation data is needed before the model can be optimized to simultaneously predict the peak temperature and thermal runaway with high accuracy.

Place, publisher, year, edition, pages
Elsevier, 2024
Keywords
Thermosetting resin, Cure behavior, Analytical modeling, Transport phenomena analysis
National Category
Materials Engineering Physical Sciences
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-105017 (URN)10.1016/j.compositesa.2024.108187 (DOI)
Note

Validerad;2024;Nivå 2;2024-04-08 (hanlid);

Full text license: CC BY 4.0

Available from: 2024-04-08 Created: 2024-04-08 Last updated: 2024-04-08Bibliographically approved
Pignatelli, F., Derafshzan, S., Sanned, D., Papafilippou, N., Szasz, R. Z., Chishty, M. A., . . . Subash, A. A. (2023). Effect of CO2 dilution on structures of premixed syngas/air flames in a gas turbine model combustor. Combustion and Flame, 255, Article ID 112912.
Open this publication in new window or tab >>Effect of CO2 dilution on structures of premixed syngas/air flames in a gas turbine model combustor
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2023 (English)In: Combustion and Flame, ISSN 0010-2180, E-ISSN 1556-2921, Vol. 255, article id 112912Article in journal (Refereed) Published
Abstract [en]

The impact of CO2 dilution on combustion of syngas (a mixture of H2, CO, and CH4) was investigated in a lab-scale gas turbine model combustor at atmospheric pressure conditions. Two mild dilution levels of CO2, corresponding to 15% and 34% of CO2 mole fraction in the syngas/CO2 mixtures, were experimentally investigated to evaluate the effects of CO2 dilution on the flame structures and the emissions of CO and NOx. All experiments were performed at a constant Reynolds number (Re = 10000). High-speed flame luminescence, simultaneous planar laser-induced fluorescence (PLIF) measurements of the OH radicals and particle image velocimetry (PIV) were employed for qualitative and quantitative assessment of the resulting flame and flow structures. The main findings are: (a) the operability range of the syngas flames is significantly affected by the CO2 dilution, with both the lean blowoff (LBO) limit and the flashback limit shifting towards fuel-richer conditions as the CO2 dilution increases; (b) syngas flames exhibit flame-pocket structures with chemical reactions taking place in isolated pockets surrounded by non-reacting fuel/air mixture; (c) the inner recirculation zone tends to move closer to the burner axis at high CO2 dilution, and (d) the NOx emission becomes significantly lower with increasing CO2 dilution while the CO emission exhibits the opposite trend. The flame-pocket structure is more significant with increased CO2 dilution level. The low NOx emissions and high CO emissions are the results of the flame-pocket structures.

Place, publisher, year, edition, pages
Elsevier Inc., 2023
Keywords
CO2 Dilution, Emissions, Flame pocket, Gas turbine model combustor, OH-PLIF, PIV, Swirl-Stabilized flames, Syngas combustion
National Category
Energy Engineering Atom and Molecular Physics and Optics
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-99428 (URN)10.1016/j.combustflame.2023.112912 (DOI)001034431300001 ()2-s2.0-85163852805 (Scopus ID)
Funder
Swedish Research CouncilSwedish Energy AgencyKnut and Alice Wallenberg Foundation, KAW COCALD project
Note

Validerad;2023;Nivå 2;2023-08-10 (joosat);

Licens fulltext: CC BY License

Funder: Siemens Energy AB (44120-1); Centre for Combustion Science and Technology (CECOST, 22538)

Available from: 2023-08-10 Created: 2023-08-10 Last updated: 2023-11-02Bibliographically approved
Papafilippou, N., Chishty, M. A. & Gebart, R. (2023). Systematic Assessment of the Two-Step, One-Way Coupled Method for Computational Fluid Dynamics. ASME Open Journal of Engineering, 2, Article ID 021020.
Open this publication in new window or tab >>Systematic Assessment of the Two-Step, One-Way Coupled Method for Computational Fluid Dynamics
2023 (English)In: ASME Open Journal of Engineering, E-ISSN 2770-3495, Vol. 2, article id 021020Article in journal (Refereed) Published
Abstract [en]

This paper assesses the validity of the Two-Step, One-Way (TSOW) coupled method for computational fluid dynamics, which splits a complicated geometry into an upstream and a downstream part. The problem is solved in two steps: first, the upstream part using approximate downstream boundary conditions, followed by a solution of the downstream flow where the inlet boundary conditions are extracted from the upstream solution. The method is based on two assumptions: first, the solution for the upstream part should be identical in the common domain to a complete solution. Second, the solution for the downstream part should be identical in the common domain to a complete solution. The resulting agreement between the upstream solution and the full solution was excellent, except in the vicinity of the outflow boundary. For the assessment of the second assumption, the downstream flow was simulated with two sets of boundary conditions, one that was extracted from the full simulation, and one that came from the upstream part solution. The two solutions in the downstream geometry with slightly different boundary conditions agreed excellently with each other but exhibited small differences from the full solution. Overall, the difference to the full solution is judged to be acceptable for many engineering design situations. The solution time for the TSOW method was about 23 h faster than the full solution, which took about 85 h on the same hardware. For additional design iterations, where the same upstream geometry can be used, a 30-h gain would be obtained for each step.

Place, publisher, year, edition, pages
ASME Press, 2023
Keywords
complex flows, computational fluid dynamics (CFD), design optimization, turbulence modeling
National Category
Fluid Mechanics and Acoustics
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-96494 (URN)10.1115/1.4062111 (DOI)
Funder
Swedish Energy Agency, 34721-3Swedish Research Council, 2016-07213
Note

Godkänd;2023;Nivå 0;2023-04-14 (hanlid);

Available from: 2023-04-14 Created: 2023-04-14 Last updated: 2023-11-02Bibliographically approved
Papafilippou, N., Chishty, M. A. & Gebart, R. (2022). Assessment of the two-step one way coupled method for CFD. In: Pär Jonsén; Lars-Göran Westerberg; Simon Larsson; Erik Olsson (Ed.), Svenska Mekanikdagar 2022: . Paper presented at Svenska Mekanikdagarna 2022, Luleå, Sweden, June 15-16, 2022. Luleå tekniska universitet
Open this publication in new window or tab >>Assessment of the two-step one way coupled method for CFD
2022 (English)In: Svenska Mekanikdagar 2022 / [ed] Pär Jonsén; Lars-Göran Westerberg; Simon Larsson; Erik Olsson, Luleå tekniska universitet, 2022Conference paper, Oral presentation with published abstract (Refereed)
Place, publisher, year, edition, pages
Luleå tekniska universitet, 2022
National Category
Fluid Mechanics and Acoustics
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-95090 (URN)
Conference
Svenska Mekanikdagarna 2022, Luleå, Sweden, June 15-16, 2022
Available from: 2022-12-30 Created: 2022-12-30 Last updated: 2023-09-05Bibliographically approved
Dal Belo Takehara, M., Llamas, A. D., Chishty, M. A., Umeki, K. & Gebart, R. (2022). Effect of acoustic perturbation on particle dispersion in a swirl-stabilized pulverized fuel burner: Cold-flow conditions. Fuel processing technology, 228, Article ID 107142.
Open this publication in new window or tab >>Effect of acoustic perturbation on particle dispersion in a swirl-stabilized pulverized fuel burner: Cold-flow conditions
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2022 (English)In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 228, article id 107142Article in journal (Refereed) Published
Abstract [en]

Inter-particle distance and particle dispersion during gasification of biomass have been found to significantly affect soot emission. Consequently, enhanced particle dispersion decreases energy losses and the risk for blockages of downstream equipment, increasing the efficiency and reliability of entrained flow reactors (EFRs). In this work, we investigated the interactions between imposed acoustic oscillations and particle dispersion under non-reacting conditions in a co-axial burner for a lab-scale EFR. A flow of air, laden with pulverized stem wood particles (Norwegian Spruce) of three different sizes (63–112 μm, 200–250 μm, and 500–600 μm), was forced axially through the burner center tube at Reynolds numbers ranged from 800 to 1700, and loading ratio of 0.7–4.2. The influences on particle dispersion from variations of the Strouhal number (0.12–0.6), the pressure amplitude at synthetic jet cavity (0.5–4.0 kPap-p), the swirl number (0–2.3), and the center jet velocity (1.9–3.9 m s−1) were investigated. Post-processed shadowgraph images revealed the influence of acoustic perturbations, which generate large structures with high particle concentration for both swirling and non-swirling conditions. Time-averaged contour maps showed a significantly higher particle dispersion, quantified as dispersion angle, for higher values of forcing amplitude and swirl numbers, with a stronger influence from the forcing amplitude, especially at lower Stokes number.

Place, publisher, year, edition, pages
Elsevier, 2022
Keywords
Biomass, Acoustic excitation, Particle-laden flow, Particle dispersion, Gas-particle coaxial jets
National Category
Fluid Mechanics and Acoustics
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-88606 (URN)10.1016/j.fuproc.2021.107142 (DOI)000749923000004 ()2-s2.0-85121808061 (Scopus ID)
Funder
Swedish Energy Agency, 47485-1The Kempe Foundations, SMK-1632
Note

Validerad;2022;Nivå 2;2022-01-01 (johcin)

Available from: 2021-12-29 Created: 2021-12-29 Last updated: 2023-09-05Bibliographically approved
Papafilippou, N., Chishty, M. A. & Gebart, R. (2022). On the Flame Shape in a Premixed Swirl Stabilised Burner and its Dependence on the Laminar Flame Speed. Flow Turbulence and Combustion, 108(2), 461-487
Open this publication in new window or tab >>On the Flame Shape in a Premixed Swirl Stabilised Burner and its Dependence on the Laminar Flame Speed
2022 (English)In: Flow Turbulence and Combustion, ISSN 1386-6184, E-ISSN 1573-1987, Vol. 108, no 2, p. 461-487Article in journal (Refereed) Published
Abstract [en]

Gas turbines for power generation are optimised to run with fossil fuels but as a response to tighter pollutant regulations and to enable the use of renewable fuels there is a great interest in improving fuel flexibility. One interesting renewable fuel is syngas from biomass gasification but its properties vary depending on the feedstock and gasification principle, and are significantly different from conventional fuels. This paper aims to give an overview of the differences in combustion behaviour by comparing numerical solutions with methane and several different synthesis gas compositions. The TECFLAM swirl burner geometry, which is designed to be representative of common gas turbine burners, was selected for comparison. The advantage with this geometry is that detailed experimental measurements with methane are publicly available. A two-stage approach was employed with development and validation of an advanced CFD model against experimental data for methane combustion followed by simulations with four syngas mixtures. The validated model was used to compare the flame shape and other characteristics of the flow between methane, 40% hydrogen enriched methane and four typical syngas compositions. It was found that the syngas cases experience lower swirl intensity due to high axial velocities that weakens the inner recirculation zone. Moreover, the higher laminar flame speed of the syngas cases has a strong effect on the flame front shape by bending it away from the axial direction, by making it shorter and by increasing the curvature of the flame front. A hypothesis that the flame shape and position is primarily governed by the laminar flame speed is supported by the almost identical flame shapes for bark powder syngas and 40% hydrogen enriched methane. These gas mixtures have almost identical laminar flame speeds for the relevant equivalence ratios but the heating value of the syngas is more than a factor of 3 smaller than that of the hydrogen enriched methane. The syngas compositions used are representative of practical gasification processes and biomass feedstocks. The demonstrated strong correlation between laminar flame speed and flame shape could be used as a rule of thumb to quickly judge whether the flame might come in contact with the structure or in other ways be detrimental to the function of the combustion system.

Place, publisher, year, edition, pages
Springer Nature, 2022
Keywords
Syngas combustion, Swirl, Laminar flame speed, Flame shape, Flamelet generated manifold (FGM)
National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-86380 (URN)10.1007/s10494-021-00279-6 (DOI)000668034700001 ()2-s2.0-85109196899 (Scopus ID)
Note

Validerad;2022;Nivå 2;2022-03-08 (hanlid);

Funder: Swedish Gasification Centre (SFC);

For correction, see: Papafilippou, N., Chishty, M.A. & Gebart, R. Correction to: On the Flame Shape in a Premixed Swirl Stabilised Burner and its Dependence on the Laminar Flame Speed. Flow Turbulence Combust (2021). https://doi.org/10.1007/s10494-021-00287-6

Available from: 2021-07-15 Created: 2021-07-15 Last updated: 2023-11-02Bibliographically approved
Dal Belo Takehara, M., Chishty, M. A., Umeki, K. & Gebart, R. (2022). Pulverized biomass flame under imposed acoustic oscillations: Flame morphology and emission characteristics. Fuel processing technology, 238, Article ID 107484.
Open this publication in new window or tab >>Pulverized biomass flame under imposed acoustic oscillations: Flame morphology and emission characteristics
2022 (English)In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 238, article id 107484Article in journal (Refereed) Published
Abstract [en]

Forced intermittent combustion with periodical variations of pressure, velocity, and air-fuel ratios is a promising method to increase efficiency and reduce emissions from combustion and gasification applications. In this work, flame characteristics and emissions from a pulverized biomass burner are investigated under oscillations induced by an acoustically-driven synthetic jet. Instantaneous images of incandescent light emitted from flame were captured using high-speed cameras. The images were analyzed to identify the liftoff distance, flame length, and shape. The flame liftoff distance decreased under excited conditions, notably at high forcing amplitude applied to small particle size distribution (63-112 μm). In such conditions, acoustic forcing increases particle dispersion as presented in the previous work, providing conditions for earlier ignition due to enhanced fuel-air mixing besides reducing CO emissions. Flue gas emissions were influenced mainly by the particle size distribution, from which the 63-112 μm particle size presented the lowest values of CO and highest levels of NO emissions. The results presented stable flame edge positions for the particle size of 63-112 μm, while wide range particle distributions (0–600, 0-400 μm) had strong fluctuations, indicating high flame instability. The experimental work adds new insights regarding acoustic excitation in swirl burners, which could be used to optimize pulverized fuel combustion.

Place, publisher, year, edition, pages
Elsevier, 2022
Keywords
Pulverized solid biomass, Acoustic excitation, Swirl stabilized burner, Particle-laden flow, Flame
National Category
Other Mechanical Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-93053 (URN)10.1016/j.fuproc.2022.107484 (DOI)000893047000004 ()2-s2.0-85138799832 (Scopus ID)
Funder
Swedish Energy Agency, 47485-1The Kempe Foundations, SMK-1632
Note

Validerad;2022;Nivå 2;2022-09-15 (joosat);

Available from: 2022-09-15 Created: 2022-09-15 Last updated: 2023-09-05Bibliographically approved
Llamas, Á. D., Guo, N., Li, T., Gebart, R. & Umeki, K. (2022). Rapid change of particle velocity due to volatile gas release during biomass devolatilization. Combustion and Flame, 238, Article ID 111898.
Open this publication in new window or tab >>Rapid change of particle velocity due to volatile gas release during biomass devolatilization
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2022 (English)In: Combustion and Flame, ISSN 0010-2180, E-ISSN 1556-2921, Vol. 238, article id 111898Article in journal (Refereed) Published
Abstract [en]

Our earlier study showed significant differences in average particle velocity between simulation and experimental results for devolatilizing biomass particles in an idealised entrained flow reactor [N. Guo et al., Fuel, 2020]. This indicates that the simulations do not accurately describe the physicochemical transformations and fluid dynamic processes during devolatilization. This article investigates the reasons for these discrepancies using time-resolved analyses of the experimental data and complementary modelling work. The experiments were conducted in a downdraft drop-tube furnace with optical access, which uses a fuel-rich flat flame (CH4 O2 CO2) to heat the particles. Gas flow was characterized using particle image velocimetry, equilibrium calculations and thermocouple measurements. High-speed images of devolatilizing Norway spruce (Picea Abies) particles were captured and analysed using time-resolved particle tracking velocimetry methods. The data were used to estimate the balance of forces and fuel conversion. Thrust and “rocket-like” motions were frequently observed, followed by quick entrainment in the gas flow. Rocketing particles were, on average, smaller, more spherical and converted faster than their non-rocketing counterparts. These differences in conversion behaviour could be captured by a particle-size dependent, 0-D devolatilization model, corrected for non-isothermal effects. The results from this investigation can provide a basis for future modelling and simulation work relevant for pulverized firing technologies.

Place, publisher, year, edition, pages
Elsevier, 2022
Keywords
Biomass devolatilization, TR-PTV, In-situ measurements, Rocket effect, Non-isothermal modelling
National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-88625 (URN)10.1016/j.combustflame.2021.111898 (DOI)000735744600001 ()2-s2.0-85121437396 (Scopus ID)
Note

Validerad;2022;Nivå 2;2022-01-01 (johcin)

Available from: 2021-12-30 Created: 2021-12-30 Last updated: 2022-01-28Bibliographically approved
Chishty, M. A., Umeki, K., Risberg, M., Wingren, A. & Gebart, R. (2021). Numerical simulation of a biomass cyclone gasifier: Effects of operating conditions on gasifier performance. Fuel processing technology, 218, Article ID 106861.
Open this publication in new window or tab >>Numerical simulation of a biomass cyclone gasifier: Effects of operating conditions on gasifier performance
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2021 (English)In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 218, article id 106861Article in journal (Refereed) Published
Abstract [en]

In Nordic countries, biomass gasification in a cyclone gasifier combined with a gas engine has been employed to generate small scale heat and power. Numerical simulations were carried out to analyze the effect of different operating conditions on the functioning of the gasifier. Reynolds-Averaged Navier-Stokes equations are solved together with the eddy-break up combustion model in conjunction with a modified k − ϵ model to predict the temperature and the flow field inside the gasifier. Results were compared with the experimental measurements in a 4.4 MW cyclone gasifier constructed by Meva Energy AB at Hortlax, Piteå, Sweden. The predicted results were in good agreement with the experimental data and the model provides detailed information about the gas compositions, cold gas efficiency and temperature field. Furthermore, the model allows different operating scenarios to be examined in an efficient manner such as the number of inlets, fuel to air velocity difference (slip-velocity) and moisture content in the fuel feedstock. The cold gas efficiency, composition of product gases and outlet temperature were monitored for each test case. These findings help to understand the importance of geometry modification, feedstock contents and make it possible to scale-up the gasifier for future applications.

Place, publisher, year, edition, pages
Elsevier, 2021
Keywords
Biomass gasification, Cyclone gasifier, Computational fluid dynamics, Moisture content
National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-84143 (URN)10.1016/j.fuproc.2021.106861 (DOI)000652818800007 ()2-s2.0-85104752175 (Scopus ID)
Funder
The Kempe Foundations, SMK-1632Swedish Energy Agency, 34721–3
Note

Validerad;2021;Nivå 2;2021-05-21 (beamah)

Available from: 2021-05-05 Created: 2021-05-05 Last updated: 2023-09-05Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-6958-5508

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