Proceedings of the Combustion Institute最新文献

{"title":"Impact of particle diameter and thermal radiation on the explosion of dust layers","authors":"Swagnik Guhathakurta ,&nbsp;Ryan W. Houim","doi":"10.1016/j.proci.2022.10.011","DOIUrl":"https://doi.org/10.1016/j.proci.2022.10.011","url":null,"abstract":"<div><p><span>Numerical simulations were performed to study the impact of thermal radiation and particle diameter on layered coal-dust explosions. The geometrical setup considered the interaction of a primary explosion with a thin layer of coal dust inside of a closed channel. The simulations solved the compressible reacting Navier–Stokes equations coupled to an Eulerian granular multiphase model. Thermal radiation was included by solving the radiation transfer equation using the filtered spherical harmonics approximation. The results show that the impact of radiation on the dust explosion is situation specific. Radiation can promote, inhibit, or have little impact on the explosion depending on the particle diameter. Radiation has a slight inhibiting effect on dust layers comprised of 30 and 100 </span><span><math><mrow><mi>μ</mi></mrow></math></span>m-diameter coal particles. Radiation quenched the explosion when particles were 5 <span><math><mrow><mi>μ</mi></mrow></math></span>m in diameter. Radiation promoted stable burning for larger 150 <span><math><mrow><mi>μ</mi></mrow></math></span>m-diameter coal particles, while simulations excluding radiation for 150 <span><math><mrow><mi>μ</mi></mrow></math></span><span>m-diameter coal particles produced a failed explosion. The influence of particle diameter on the dispersibility characteristics of dust layers has a significant impact on the explosion. Small 5 </span><span><math><mrow><mi>μ</mi></mrow></math></span>m-diameter coal particles are dispersed poorly by the leading shock and are too highly concentrated to burn. Large 150 <span><math><mrow><mi>μ</mi></mrow></math></span>m-diameter particles disperse higher into the channel and show improved mixing, but have large thermal time scales that inhibit vigorous reaction. Cases with 30 and 100 <span><math><mrow><mi>μ</mi></mrow></math></span>m-diameter particles show a good compromise between dispersibility, mixing, and thermal time scales which produce stable combustion with or without the inclusion of thermal radiation in the model.</p></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"39 3","pages":"Pages 2905-2914"},"PeriodicalIF":3.4,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"3460681","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An analysis of the in-cylinder soots generated from the main- and post-injection combustion in diesel engines","authors":"Wei Zhang ,&nbsp;Chenyang Fan ,&nbsp;Gang Lyu ,&nbsp;Yunqiang Li ,&nbsp;Ye Liu ,&nbsp;Chenxi Wang ,&nbsp;Chonglin Song","doi":"10.1016/j.proci.2022.07.216","DOIUrl":"https://doi.org/10.1016/j.proci.2022.07.216","url":null,"abstract":"<div><p><span><span>In modern diesel engines, the exhaust soot primarily comes from the main-injection combustion and post-injection combustion. Therefore, to reduce the diesel soot emissions, it is essential to better understand the soots generated from the main-injection combustion (main-soot) and from the post-injection combustion (post-soot). This work focused on the properties of the main-soot and post-soot during the </span>combustion process, including the primary particle size, </span>nanostructure<span> and soot mass. The in-cylinder soot samples were obtained using a self-developed total cylinder sampling system, and the primary particle size and nanostructure were determined using high-resolution transmission electron microscopy. The isolation of the post-soot was achieved by adding dimethyl ether to the intake gas instead of the real main-injection to create a simulated main-injection combustion environment for post-soot formation. Combustion analysis and numerical simulation results showed that the simulated combustion environment for post-soot formation generated by the DME combustion was very similar to that generated by the real main-injection combustion. During the combustion process, although the main-soot and post-soot exhibit similar variations in the primary particle size, the maximum primary particle size of the post-soot is smaller than that of the main-soot (23.38 nm for the main-soot and 20.51 nm for the post-soot). The main-soot and post-soot show almost the same trends in the nanostructure, as characterized by the fringe length, separation and tortuosity, throughout the combustion process. The introduction of the post-injection accelerates the reduction of the primary particle size of the main-soot and the increase in the structural order of the main-soot. Because a large number of the main-soot particles are oxidized during the post-injection combustion, the post-soot accounts for a considerable proportion in the engine-out soot (i.e., 42%).</span></p></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"39 1","pages":"Pages 939-947"},"PeriodicalIF":3.4,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"3460812","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Reactivity of boron carbide and metal oxide mixtures","authors":"Kyle Horiuchi,&nbsp;Andy Huynh,&nbsp;Joseph Kalman","doi":"10.1016/j.proci.2022.07.107","DOIUrl":"https://doi.org/10.1016/j.proci.2022.07.107","url":null,"abstract":"<div><p>Boron-based materials have high energy density making them suitable as additives in propulsion systems. However, the lack of prompt ignition, for example, creates a challenge in harnessing the energy. In this work, mixtures of boron carbide and four common metal oxides (CuO, MnO<span><math><msub><mrow></mrow><mn>2</mn></msub></math></span>, Bi<span><math><msub><mrow></mrow><mn>2</mn></msub></math></span>O<span><math><msub><mrow></mrow><mn>3</mn></msub></math></span>, Fe<span><math><msub><mrow></mrow><mn>2</mn></msub></math></span>O<span><math><msub><mrow></mrow><mn>3</mn></msub></math></span>) are studied as a way to increase the reactivity of boron-based materials. Both burning rate and thermal analysis are used to determine the response of mixtures to fast and slow heating rates, respectively. Mixtures with CuO or Bi<span><math><msub><mrow></mrow><mn>2</mn></msub></math></span>O<span><math><msub><mrow></mrow><mn>3</mn></msub></math></span> burned the fastest whereas Fe<span><math><msub><mrow></mrow><mn>2</mn></msub></math></span>O<span><math><msub><mrow></mrow><mn>3</mn></msub></math></span> mixtures would not ignite and MnO<span><math><msub><mrow></mrow><mn>2</mn></msub></math></span> samples had a burning rate approximately 15% that of the fastest mixtures. The thermal analysis determined that the gas produced from carbon oxidation was most influential on the combustion rate and not the thermal conductivity or oxygen release temperature of the oxide. Experimental observation indicates that the boron component is oxidized in the condensed phase despite the importance of gas generation. Spectroscopic evidence presented suggests gas generation aids in removing the molten boron oxide layer during combustion which can be utilized to improve the reactivity of boron-based additives in propulsion applications.</p></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"39 3","pages":"Pages 3313-3321"},"PeriodicalIF":3.4,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"3461278","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Opposed flame spread over folded PMMA plate with various internal angles","authors":"Tsuneyoshi Matsuoka ,&nbsp;Yuki Chiba ,&nbsp;Shinnosuke Okuno ,&nbsp;Hiroyuki Torikai ,&nbsp;Subrata Bhattacharjee ,&nbsp;Takuya Yamazaki ,&nbsp;Yuji Nakamura","doi":"10.1016/j.proci.2022.07.153","DOIUrl":"https://doi.org/10.1016/j.proci.2022.07.153","url":null,"abstract":"<div><p>The effect of the internal angle on downward flame spread over a thick folded plate is experimentally investigated in this study. The lateral side of a thermoplastic plate is cut at desired angles and two of these plates are welded to form a single folded sample. All the faces other than the front and two 5-mm areas of the front face from each side were coated to inhibit the combustion. Experiments are conducted for various folded plates of different angles, 60°, 90°, 120°, and 180°. Following ignition at the upper edge of the sample, the opposed flame spread on the front face is observed and the flame spread rate at various positions is quantified by image analysis. The flame spreads more rapidly at the folding edge, while the other parts then accelerate to catch up with the corner spread and, eventually, all the parts across the width achieve the same flame spread rate as the folding edge. This result indicates that the flame spread rate at the folding edge is the characteristic value which represents the steady-state of the system of interest. A simple model is developed considering change of heated volume against the flame and change of the induced flow velocity due to the geometry. The former effect is formulated from geometrical consideration in the vicinity of the edge, while the latter is formulated based on an experimental fact that the flame height is inversely proportional to the internal angle. A prediction formula of the flame spread rate at the folding edge is established by modifying the conventional one for the flat plate. The calculated flame spread rate shows reasonably good agreement with the experimental data. This study helps fundamental understanding of the flame spread behavior of practical combustibles such as pillars or rods with various cross-sectional shapes.</p></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"39 3","pages":"Pages 3805-3812"},"PeriodicalIF":3.4,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"2821717","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Laminar flame propagation of acetone and 2-butanone at normal to high pressures: Insight into fuel molecular structure effects of ketones","authors":"Jianguo Zhang,&nbsp;Wei Li,&nbsp;Bowen Mei,&nbsp;Yuyang Li","doi":"10.1016/j.proci.2022.07.009","DOIUrl":"https://doi.org/10.1016/j.proci.2022.07.009","url":null,"abstract":"<div><p><span><span>This work reports an experimental and kinetic modeling investigation on the laminar flame propagation of </span>acetone<span> and 2-butanone at normal to high pressures. The experiments were performed in a high-pressure constant-volume cylindrical combustion vessel at 1–10 atm, 423 K and equivalence ratios of 0.7–1.5. A kinetic model of acetone and 2-butanone combustion was developed from our recent pentanone model [Li et al., Proc. Combust. Inst. 38 (2021) 2135–2142] and validated against experimental data in this work and in literature. Together with our recently reported data of 3-pentanone, remarkable fuel molecular structure effects were observed in the laminar flame propagation of the three C</span></span>₃<img>C₅ ketones. The laminar burning velocity increases in the order of acetone, 2-butanone and 3-pentanone, while the pressure effects in laminar burning velocity reduces in the same order. Modeling analysis was performed to provide insight into the key pathways in flames of acetone and 2-butanone. The differences in radical pools are concluded to be responsible for the observed fuel molecular structure effects on laminar burning velocity. The favored formation of methyl in acetone flames inhibits its reactivity and leads to the slowest laminar flame propagation, while the easiest formation of ethyl in 3-pentanone flames results in the highest reactivity and fastest laminar flame propagation. Furthermore, the LBVs of acetone and 3-pentanone exhibit the strongest and weakest pressure effects respectively, which can be attributed to the influence of fuel molecular structures through two crucial pressure-dependent reactions CH₃ + H (+M) = CH₄ (+M) and C₂H₄ + H (+M) = C₂H₅ (+M).</p></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"39 2","pages":"Pages 1709-1720"},"PeriodicalIF":3.4,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"2821720","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Burning structures and propagation mechanisms of nanothermites","authors":"Suyong Kim ,&nbsp;Averitt A. Johns ,&nbsp;John Z. Wen ,&nbsp;Sili Deng","doi":"10.1016/j.proci.2022.07.113","DOIUrl":"https://doi.org/10.1016/j.proci.2022.07.113","url":null,"abstract":"<div><p><span>Nanothermites demonstrate attractive combustion characteristics such as tunable reactivity and high energy density. There is however a lack of fundamental understanding on their burning structures and reaction mechanisms due to the multi-scale complexity associated with the material and reaction heterogeneities. This gap in turn hinders the optimization of nanothermite design with desirable microstructures and controllable burning properties. In this work, a high-speed microscopy imaging system was used to reveal the burning structure of Al/CuO nanothermites and to investigate the propagation mechanism of its flame front at micron and sub-millimeter scales which have not been studied. An Al/CuO nanothermite film was fabricated as a model structure. First, the previously proposed reactive sintering was confirmed as a micron-scale burning characteristic. Then, at the sub-millimeter scale, it was demonstrated that the non-uniform burning propagation of nanothermite films is featured with distinguishable roles of the active burning sites and the pre-ignition sites. The active burning sites are clusters of reactive sintering particles and the pre-ignition sites appear in the preheating regions where Al and CuO particles have not yet participated in the reaction due to insufficient ignition energy. These pre-ignition sites form randomly and are subsequently ignited by heat transferred from the adjacent active burning sites, resulting in an active burning propagation tangentially along the propagation front. At the same time, as the thermite reaction of </span>nanoparticles in the unburnt region is initiated, the propagation front advances in the normal direction. This experimental work reveals that the burning propagation mechanism of nanothermite films is governed by active burning propagation in both tangential and normal directions of the propagation front. Although the rates of these two modes are on the same order of magnitude, the tangential propagation of active burning is slightly faster, implying that pre-ignition sites are readily ignited with lower ignition energy.</p></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"39 3","pages":"Pages 3593-3604"},"PeriodicalIF":3.4,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"2821870","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ignition limit and shock-to-detonation transition mode of n-heptane/air mixture in high-speed wedge flows","authors":"Hongbo Guo ,&nbsp;Yong Xu ,&nbsp;Hongtao Zheng ,&nbsp;Huangwei Zhang","doi":"10.1016/j.proci.2022.08.082","DOIUrl":"https://doi.org/10.1016/j.proci.2022.08.082","url":null,"abstract":"<div><p>In this work, oblique detonation of <em>n</em><span><span><span><span>-heptane/air mixture in high-speed wedge flows is simulated by solving the reactive Euler equations with a two-dimensional (2D) configuration. This is a first attempt to model complicated hydrocarbon fuel oblique </span>detonation waves (ODWs) with a detailed chemistry (44 species and 112 reactions). Effects of </span>freestream<span> equivalence ratios and velocities are considered, and the abrupt and smooth transition from oblique shock to detonation are predicted. Ignition limit, ODW characteristics, and predictability of the transition mode are discussed. Firstly, homogeneous constant-volume ignition calculations are performed for both fuel-lean and stoichiometric mixtures. The results show that the </span></span>ignition delay<span> generally increases with the wedge angle. However, a negative wedge angle dependence is observed, due to the negative temperature coefficient effects. The wedge angle range for successful ignition of </span></span><em>n</em><span>-heptane/air mixtures decreases when the wedge length is reduced. From two-dimensional simulations of stationary ODWs, the initiation length generally decreases with the freestream equivalence ratio, but the transition length exhibits weakly non-monotonic dependence. Smooth ODW typically occurs for lean conditions (equivalence ratio &lt; 0.4). The interactions between shock/compression waves and chemical reaction inside the induction zone are also studied with the chemical explosive mode analysis. Moreover, the predictability of the shock-to-detonation transition mode is explored through quantifying the relation between ignition delay and chemical excitation time. It is demonstrated that the ignition delay (the elapsed time of the heat release rate, HRR, reaches the maximum) increases, but the excitation time (the time duration from the instant of 5% maximum HRR to that of the maximum) decreases with the freestream equivalence ratio for the three studied oncoming flow velocities. Smaller excitation time corresponds to stronger pressure waves from the ignition location behind the oblique shock. When the ratio of excitation time to ignition delay is high (e.g., &gt; 0.5 for </span><em>n</em>-C₇H₁₆, &gt; 0.3 for C₂H₂ and &gt; 0.2 for H₂, based on the existing data compilation in this work), smooth transition is more likely to occur.</p></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"39 4","pages":"Pages 4771-4780"},"PeriodicalIF":3.4,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"3143203","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental investigation of low-temperature autoignition in turbulent premixed swirling flames","authors":"Wenjun Lin ,&nbsp;Wang Han ,&nbsp;Jinhua Wang ,&nbsp;Runze Mao ,&nbsp;Weijie Zhang ,&nbsp;Xiao Cai ,&nbsp;Zuohua Huang","doi":"10.1016/j.proci.2022.08.066","DOIUrl":"https://doi.org/10.1016/j.proci.2022.08.066","url":null,"abstract":"<div><p><span><span>The role of low-temperature chemistry/ignition (LTC/LTI) in aero engine-like combustors that feature confined bluff-body and </span>swirling flows inside has been studied in the present work. A series of CH</span><span><math><msub><mrow></mrow><mn>4</mn></msub></math></span>/DME/air mixtures were experimentally investigated at <span><math><mrow><mi>ϕ</mi><mo>=</mo><mn>0.65</mn></mrow></math></span> with the volume fraction of DME in the fuel blend (<span><math><msub><mi>α</mi><mtext>DME</mtext></msub></math></span>) ranging from 0% to 100% to take LTI into account. To this end, OH-PLIF and CH<span><math><msub><mrow></mrow><mn>2</mn></msub></math></span><span>O-PLIF measurements combined with PIV and thermocouple<span> methods are used to capture high-temperature and low-temperature flames (HTFs and LTFs) and the flow field and temperature in the outer recirculation zone (ORZ). It is found that adding DME into the lean CH</span></span><span><math><msub><mrow></mrow><mn>4</mn></msub></math></span><span>/air mixture has the potential to introduce LTF in the ORZ under certain conditions. There are three flame regimes in the bluff-body swirl burner in terms of DME enrichment (</span><span><math><msub><mi>α</mi><mtext>DME</mtext></msub></math></span>): (1) When <span><math><mrow><msub><mi>α</mi><mtext>DME</mtext></msub><mo>&lt;</mo><mn>50</mn><mo>%</mo></mrow></math></span>, neither of LTF and HTF exist in the ORZ, and only a V-shape HTF is observed between the inner shear layer (ISL) and inner recirculation zone (IRZ), denoted as regime I. (2) When <span><math><mrow><mn>50</mn><mo>%</mo><mo>≤</mo><msub><mi>α</mi><mtext>DME</mtext></msub><mo>≤</mo><mn>70</mn><mo>%</mo></mrow></math></span>, a stable LTF in the ORZ can co-exist with the above V-shape HTF, denoted as regime II. (3) When <span><math><mrow><msub><mi>α</mi><mtext>DME</mtext></msub><mo>&gt;</mo><mn>70</mn><mo>%</mo></mrow></math></span><span>, besides the V-shape HTF, the LTF in the ORZ and a new HTF front between the ORZ and outer shear layer (OSL) can exist intermittently, i.e., the LTF first occurs in the ORZ and then transitions to the new HTF between the ORZ and OSL, denoted as regime III. Furthermore, using an ignition Damköhler number (</span><span><math><mrow><mi>D</mi><msub><mi>a</mi><mtext>ig</mtext></msub></mrow></math></span><span>), defined as the ratio of maximum fluid residence time and evaluated shortest first-stage or second-stage ignition delay time in the ORZ, is able to reasonably classify the flame regimes. These results open up the possibility of employing LTI to extend the stability margin of lean swirling flames.</span></p></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"39 4","pages":"Pages 4801-4810"},"PeriodicalIF":3.4,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"3143204","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Analysis of model dimensionality, particle shrinkage, boundary layer reactions on particle-scale modelling of biomass char conversion under pulverized fuel combustion conditions","authors":"Hao Luo ,&nbsp;Xinyan Liu ,&nbsp;Lukasz Niedzwiecki ,&nbsp;Xiaoqin Wu ,&nbsp;Weigang Lin ,&nbsp;Bona Lu ,&nbsp;Wei Wang ,&nbsp;Hao Wu","doi":"10.1016/j.proci.2022.10.007","DOIUrl":"https://doi.org/10.1016/j.proci.2022.10.007","url":null,"abstract":"<div><p><span><span>In this work, the effects of model dimensionality, particle shrinkage, and boundary layer reactions on particle-scale modelling of biomass char conversion under pulverized fuel combustion conditions have been analysed by using six models: zero-dimensional models with constant particle size (0D_Cons) or shrinking particle size (0D_SPM), one-dimensional models with/without considering particle shrinkage (1D_Cons/1D_SPM), and 1D_Cons and 1D_SPM with considering boundary layer reactions (1D_Cons_BH and 1D_SPM_BH). A comparison with existing experimental data shows that the 1D_SPM_BH model with consideration of intra-particle heat and mass transfer, particle shrinkage, and boundary layer reactions is an appropriate model to describe biomass char conversion over a wide range of conditions. The 0D_Cons model is a good approximation for the conditions of small particle size (&lt; 1 mm) at 1273–1473 K, but overestimates the char conversion rate for larger biomass </span>char particle or at high temperatures (regime III). The 0D_SPM model gives a reasonable prediction on char conversion time but predicts a larger contribution of reaction between char and O</span>₂<span> as compared to the 1D_SPM_BH model. The consideration of intra-particle heat and mass transfer in particle-scale modelling (1D_Cons and 1D_SPM) is beneficial to improving the model prediction of char conversion time and the contributions of char oxidation<span> and gasification reactions. The boundary layer reactions have a significant effect on the prediction of char conversion for large particles (&gt; 1 mm) and high temperatures (&gt; 1473 K). An implication for the selection of a particle-scale model in CFD modelling is also given.</span></span></p></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"39 3","pages":"Pages 3529-3538"},"PeriodicalIF":3.4,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"3206929","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An experimental study on flame geometry and radiation flux of line-source fire over inclined surface","authors":"Yanli Miao,&nbsp;Yuhang Chen,&nbsp;Fei Tang,&nbsp;Xiaolei Zhang,&nbsp;Longhua Hu","doi":"10.1016/j.proci.2022.07.109","DOIUrl":"https://doi.org/10.1016/j.proci.2022.07.109","url":null,"abstract":"<div><p><span><span>An experimental study was performed on line-source fire over an inclined surface (ground) to simulate downhill fire spread behavior. The flame geometry and the thermal radiation<span> to both far-field surroundings and near-field inclined surface were investigated. As a basic configuration for wildland fire over a slope, the buoyancy induced natural convection flow along the inclined surface and the constraint of </span></span>air entrainment<span> by the inclined surface change the flame geometry as well as its radiation emission. Various surface (ground) inclination angles (from 0°-80°), fire source heat release rates and fuels were considered comprehensively with a total of 126 test conditions. Results showed that the flame perpendicular height decreased, while both the flame parallel length and base drag length along the inclined surface increased, with the increased inclination angle. A dimensional analysis was then performed based on the controlling mechanisms, with the dimensionless heat release rate, the density ratio of fuel vapor to air, along with sin</span></span><em>α</em> and cos<em>α</em><span> involved to represent the components in the parallel and perpendicular directions. The flame geometry parameters were well represented by the proposed dimensional analysis. Both the radiation fluxes to far-field surroundings and to near-field inclined surface decreased with the increased inclination angle. The far-field radiation was found to be well characterized by a model based on the soot volume fraction analysis according to single point source model. Concerning the near-field radiation to inclined surface, an inclined cuboid radiative modeling was developed. The predicting results by the proposed model and the experimental values showed good agreement. The present study has explained the controlling physics and proposed non-dimensional functions for flame geometry and modeling the downslope radiation of the line-source fire over the inclined surface, which facilitates the understanding of the wildland fire spread behavior over a slopping ground in the downhill direction.</span></p></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"39 3","pages":"Pages 3795-3803"},"PeriodicalIF":3.4,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"3273445","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}