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The Role of Magnetic Field Orientation in Vegetable Oil Premixed Combustion 磁场取向在植物油预混燃烧中的作用
IF 0.7 Q3 ENGINEERING, CHEMICAL Pub Date : 2020-01-28 DOI: 10.1155/2020/2145353
D. Perdana, L. Yuliati, N. Hamidi, I. Wardana
This study observed the influence of magnetic field orientation on the premixed combustion of vegetable oil. The results show that the magnetic field increased the laminar burning velocity because the spin of electron became more energetic and changes the spin of hydrogen proton from para to ortho. The increase of flame speed became larger on vegetable oil with stronger electric poles. The attraction magnetic field gives the strongest effect against the increase of flame speed and makes flame stability limit wider toward lean equivalence ratio. This is because O2 with the paramagnetic nature is pumped more crossing flame from the south pole (S) to north pole (N) whereas the heat energy carried by H2O from the reaction product with the diamagnetic nature is pumped more crossing flame in the N pole to the S pole. This made the combustion close to Lewis number equal to unity, whereas in the repulsion magnetic poles, S-S, more O2 is pumped into the flame while more heat is pumped out of the flame, and thus, combustion in the flame is leaner and reactions are not optimal. Conversely, at N-N poles, more heat carried by H2O was pumped into the flame while more O2 was pumped out of the flame. As a result, combustion in the flame is richer and the reaction is also not optimal. As a consequence, the velocity of the laminar flame at the repelling poles is lower than that of attracting poles.
研究了磁场取向对植物油预混燃烧的影响。结果表明,磁场使氢质子的自旋从对位方向改变为正位方向,使电子的自旋能量增大,从而提高了层流燃烧速度。随着电线杆强度的增大,植物油的火焰速度增加幅度更大。吸引磁场对火焰速度的增加影响最大,使火焰稳定极限向lean等效比方向变宽。这是因为具有顺磁性质的O2从南极(S)向北极(N)输送了更多的交叉火焰,而具有反磁性质的反应产物中H2O携带的热能则从N极向S极输送了更多的交叉火焰。这使得燃烧接近路易斯数等于1,而在斥力磁极S-S中,更多的O2被泵入火焰,而更多的热量被泵出火焰,因此,火焰中的燃烧更稀薄,反应不是最优的。相反,在N-N极,更多的H2O携带的热量被泵入火焰,而更多的O2被泵出火焰。因此,火焰中的燃烧更丰富,反应也不是最优的。因此,层流火焰在排斥极处的速度低于吸引极处的速度。
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引用次数: 2
Numerical Study on the Required Surrounding Gas Conditions for Stable Autoignition of an Ethanol Spray 乙醇喷雾稳定自燃所需环境条件的数值研究
IF 0.7 Q3 ENGINEERING, CHEMICAL Pub Date : 2019-10-17 DOI: 10.1155/2019/1329389
H. Saitoh, K. Uchida, Norihiko Watanabe
This study deals with the development of controlled-ignition technology for high-performance compression ignition alcohol engines. Among the alcohol fuels, we focus on ethanol as it is a promising candidate of alternative fuels replacing petroleum. The objective of this study is to reveal the physical and chemical phenomena in the mixture formation process up to autoignition of an ethanol spray. In our previous numerical study, we showed the mixture formation process for gas oil and ethanol sprays in the form of spatial excess air ratio and temperature distributions inside a spray and their temporal histories from fuel injection. The results showed a good agreement with those of theoretical analysis based on the momentum theory of spray penetration. Calculation was also confirmed as reasonable by comparing to the experimental results. Through the series of our experimental and numerical studies, the reason for poor autoignition quality of an ethanol spray was revealed, that is, difficulty in simultaneous attainments of autoignition-suitable concentration and temperature in the spray mixture formation due to its fuel and thermal properties of smaller stoichiometric air-fuel ratio and much greater heat of evaporation compared to conventional diesel fuels. However, autoignition of an ethanol spray has not been obtained yet in either experiments or numerical analysis. As the next step, we numerically examined several surrounding gas pressure and temperature conditions to make clear the surrounding gas conditions enough to obtain stable autoignition. One of the commercial CFD codes CONVERGE was used in the computational calculation with the considerations of turbulence, atomization, evaporation, and detailed chemical reaction. Required surrounding gas pressure and temperature for stable autoignition with acceptable ignition delay of an ethanol spray and feasibility of the development of high-performance compression ignition alcohol engines are discussed in this paper.
本文研究了高性能压缩点火酒精发动机控制点火技术的发展。在酒精燃料中,我们重点关注乙醇,因为它是一个有前途的替代燃料替代石油。本研究的目的是揭示乙醇喷雾自燃前混合物形成过程中的物理和化学现象。在我们之前的数值研究中,我们以空间过剩空气比和喷雾内温度分布的形式展示了汽油和乙醇喷雾的混合形成过程以及燃油喷射的时间历史。结果与基于喷淋动量理论的理论分析结果吻合较好。通过与实验结果的对比,验证了计算的合理性。通过一系列的实验和数值研究,揭示了乙醇喷雾自燃质量差的原因,即与传统柴油相比,乙醇喷雾的燃料和热性质,其化学计量空燃比小,蒸发热大,难以同时达到喷雾混合物的自燃适宜浓度和温度。然而,无论是实验还是数值分析,都没有得到乙醇喷雾的自燃现象。下一步,我们数值测试了几种周围气体压力和温度条件,以明确周围气体条件足以获得稳定的自燃。计算中使用了商业CFD代码之一CONVERGE,考虑了湍流、雾化、蒸发和详细的化学反应。本文讨论了乙醇喷雾在可接受的点火延迟条件下稳定自燃所需的周围气体压力和温度,以及研制高性能压缩点火酒精发动机的可行性。
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引用次数: 0
Investigation of the Effects of Steam Injection on Equilibrium Products and Thermodynamic Properties of Diesel and Biodiesel Fuels 注汽对柴油和生物柴油平衡产物及热力学性质影响的研究
IF 0.7 Q3 ENGINEERING, CHEMICAL Pub Date : 2019-10-10 DOI: 10.20944/preprints201910.0108.v1
Jean Paul Gram Shou, M. Obounou, T. Kofané, Mahamat Hassane Babikir
The effects of steam injection on combustion products and thermodynamic properties of diesel fuel, soybean oil-based biodiesel (NBD), and waste cooking oil biodiesel (WCOB) are examined in this study by considering the chemical equilibrium. The model gives equilibrium mole fractions, specific heat of the exhaust mixtures of 10 combustion products, and adiabatic flame temperatures. The results show that the mole fractions of carbon monoxide (CO) and carbon dioxide (CO2) decrease with the steam injection ratios. Nitric oxide (NO) mole fractions decrease with the steam injections ratios for lean mixtures. The specific heat of combustion products increases with the steam injection ratios. The equilibrium combustion products obtained can be used to calculate the nonequilibrium values of NO in the exhaust gases using some existing correlations of NO kinetics.
从化学平衡的角度考察了蒸汽注入对柴油、大豆油基生物柴油(NBD)和废食用油生物柴油(WCOB)燃烧产物和热力学性质的影响。该模型给出了平衡摩尔分数、10种燃烧产物废气混合物的比热和绝热火焰温度。结果表明:随着注汽比的增大,一氧化碳(CO)和二氧化碳(CO2)的摩尔分数降低;稀薄混合物的一氧化氮(NO)摩尔分数随注汽比的增加而降低。燃烧产物比热随喷汽比的增大而增大。得到的平衡燃烧产物可以利用已有的NO动力学关系式来计算废气中NO的非平衡值。
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引用次数: 2
Evaluation of a 38 L Explosive Chamber for Testing Coal Dust Explosibility 38l煤尘爆炸试验箱的评价
IF 0.7 Q3 ENGINEERING, CHEMICAL Pub Date : 2019-09-02 DOI: 10.1155/2019/5810173
R. Eades, K. Perry
Coal dust explosions are the deadliest disasters facing the coal mining industry. Research has been conducted globally on this topic for decades. The first explosibility tests in the United States were performed by the Bureau of Mines using a 20 L chamber. This serves as the basis for all standardized tests used for combustible dusts. The purpose of this paper is to investigate the use of a new 38 L chamber for testing coal dust explosions. The 38 L chamber features design modifications to model the unique conditions present in an underground coal mine when compared to other industries where combustible dust hazards are present. A series of explosibility tests were conducted within the explosive chamber using a sample of Pittsburgh pulverized coal dust and a five kJ Sobbe igniter. Analysis to find the maximum pressure ratio and Kst combustible dust parameter was performed for each trial. Based upon this analysis, observations are made for each concentration regarding whether the explosibility test was under-fueled or over-fueled. Based upon this analysis, a recommendation for future explosibility testing concentrations is made.
煤尘爆炸是煤矿行业面临的最致命的灾难。几十年来,全球对这一主题进行了研究。美国的第一次爆炸试验是由矿产局使用20升燃烧室进行的。这是用于可燃粉尘的所有标准化测试的基础。本文的目的是研究一种新的38l燃烧室用于煤尘爆炸试验。与存在可燃粉尘危害的其他行业相比,38 L燃烧室的设计修改是为了模拟地下煤矿中存在的独特条件。使用匹兹堡煤粉粉尘样品和5kj Sobbe点火器在爆炸室内进行了一系列爆炸试验。对每次试验进行了最大压力比和Kst可燃粉尘参数分析。在此分析的基础上,对每个浓度的爆炸试验是否燃料不足或燃料过剩进行了观察。在此基础上,提出了未来爆炸试验浓度的建议。
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引用次数: 2
A Two-Fluid Conditional Averaging Paradigm for the Theory and Modeling of Turbulent Premixed Combustion 紊流预混燃烧理论与建模的两流体条件平均范式
IF 0.7 Q3 ENGINEERING, CHEMICAL Pub Date : 2019-08-07 DOI: 10.1155/2019/5036878
V. Zimont
This paper extends a recent theoretical study that was previously presented in the form of a brief communication (Zimont, C&F, 192, 2018, 221-223), in which we proposed a simple splitting method for the derivation of two-fluid conditionally averaged equations of turbulent premixed combustion in the flamelet regime, formulated more conveniently for applications involving unclosed equations without surface-averaged unknowns. This two-fluid conditional averaging paradigm avoids the challenge in the Favre averaging paradigm of modeling the countergradient scalar transport phenomenon and the unusually large velocity fluctuations in a turbulent premixed flame. It is a more suitable conceptual framework that is likely to be more convenient in the long run than the traditional Favre averaging method. In this article, we further develop this paradigm and pay particular attention to the problem of modeling turbulent premixed combustion in the context of a two-fluid approach. We formulate and analyze the unclosed differential equations in terms of the conditions of the Reynolds stresses τij,u, τij,b and the mean chemical source ρW¯, which are the only modeling unknowns required in our alternative conditionally averaged equations. These equations are necessary for the development of model differential equations for the Reynolds stresses and the chemical source in the advanced modeling and simulation of turbulent premixed combustion. We propose a simpler approach to modeling the conditional Reynolds stresses based on the use of the two-fluid conditional equations of the standard “k-ε” turbulence model, which we formulate using the splitting method. The main problem arising here is the appearance in these equations of unknown terms describing the exchange of the turbulent energy k and dissipation rate ε in the unburned and burned gases. We propose an approximate way to avoid this problem. We formulate a simple algebraic expression for the mean chemical source that follows from our previous theoretical analysis of the transient turbulent premixed flame in the intermediate asymptotic stage, in which small-scale wrinkles in the instantaneous flame surface reach statistical equilibrium, while the large-scale wrinkles remain in statistical nonequilibrium.
本文扩展了先前以简短通信形式提出的最新理论研究(Zimont, C&F, 192, 2018, 221-223),其中我们提出了一种简单的分裂方法,用于推导小火焰状态下湍流预混燃烧的两流体条件平均方程,该方法更方便地用于涉及无表面平均未知量的非封闭方程的应用。这种双流体条件平均模式避免了Favre平均模式在模拟反梯度标量输运现象和湍流预混火焰中异常大的速度波动时所面临的挑战。这是一个更合适的概念框架,从长远来看可能比传统的Favre平均方法更方便。在本文中,我们进一步发展了这一范式,并特别关注在双流体方法的背景下模拟湍流预混燃烧的问题。我们根据雷诺应力τij,u, τij,b和平均化学源ρW¯的条件来制定和分析非封闭微分方程,这是我们的备选条件平均方程中唯一需要的建模未知数。在紊流预混燃烧的高级建模和模拟中,这些方程是建立雷诺应力和化学源模型微分方程所必需的。我们提出了一种更简单的方法来模拟条件雷诺应力,该方法基于标准“k-ε”湍流模型的双流体条件方程,我们使用分裂方法来表达。这里出现的主要问题是这些方程中出现了描述未燃烧和燃烧气体中湍流能量k和耗散率ε交换的未知项。我们提出一个近似的方法来避免这个问题。我们根据之前对瞬态湍流预混火焰在中间渐近阶段的理论分析,给出了平均化学源的简单代数表达式,其中瞬态火焰表面的小尺度褶皱达到统计平衡,而大尺度褶皱仍处于统计非平衡状态。
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引用次数: 1
Critical Velocity and Backlayering Conditions in Rail Tunnel Fires: State-of-the-Art Review 铁路隧道火灾的临界速度和背层条件:最新进展
IF 0.7 Q3 ENGINEERING, CHEMICAL Pub Date : 2019-05-28 DOI: 10.1155/2019/3510245
R. Haddad, C. Maluk, E. Reda, Z. Harun
The use of interurban and urban trains has become the preferred choice for millions of daily commuters around the world. Despite the huge public investment for train technology and mayor rail infrastructure (e.g., tunnels), train safety is still a subject of concern. The work described herein reviews the state of the art on research related to critical velocity and backlayering conditions in tunnel fires. The review on backlayering conditions includes the effect of blockages, inclination, and the location of the fire source. The review herein focuses on experimental and theoretical research, although it excludes research studies using numerical modeling. Many studies have used scaled tunnel structures for experimental testing; nevertheless, there are various scaling challenges associated with these studies. For example, very little work has been done on flame length, fire source location, and the effect of more than one blockage, and how results on scaled experiments represent the behaviour at real-scale. The review sheds light on the current hazards associated with fires in rail tunnels.
使用城际和城市列车已成为世界各地数百万日常通勤者的首选。尽管对列车技术和主要铁路基础设施(如隧道)进行了巨大的公共投资,但列车安全仍然是一个令人担忧的问题。本文所述的工作回顾了隧道火灾中临界速度和背层条件的研究现状。对背层条件的审查包括障碍物、倾斜度和火源位置的影响。本文的综述侧重于实验和理论研究,但不包括使用数值模拟的研究。许多研究都采用尺度隧道结构进行实验测试;然而,与这些研究相关的各种规模挑战。例如,关于火焰长度,火源位置,多个阻塞的影响,以及缩放实验的结果如何代表真实尺度的行为的研究很少。该报告揭示了目前与铁路隧道火灾有关的危险。
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引用次数: 15
Dynamic Simulation on Deflagration of LNG Spill LNG溢油爆燃的动态模拟
IF 0.7 Q3 ENGINEERING, CHEMICAL Pub Date : 2019-04-28 DOI: 10.1155/2019/7439589
Biao Sun, K. Guo, V. Pareek
The deflagration characteristics of premixed LNG vapour-air mixtures with different mixing ratios were quantitatively and qualitatively investigated by using CFD (computational fluid dynamics) method. The CFD model was initially established based on theoretical analysis and then validated by a lab-scale deflagration experiment. The flame propagation behaviour, pressure-time history, and flame speed were compared with the experimental data, upon which a good agreement was achieved. A large-scale deflagration fire during LNG bunkering process was conducted using the model to investigate the flame development and overpressure effects. Mesh independence and time scale were tested in order to obtain the suitable grid resolution and time step. Deflagration cases with two different LNG vapour volume fractions, i.e., 10.4% and 15.0%, were simulated and compared. The one with a volume fraction of 10.4% which was around stoichiometric mixing ratio had the highest flame propagating speed. High flame velocity observed in the simulation was coupled with the thin flame front where overpressure occurred. The CFD model could capture the main features of deflagration combustion and account for LNG fire hazard which could provide an in-depth insight when dealing with complicated cases.
采用计算流体力学(CFD)方法,对不同混合比的LNG蒸汽-空气预混料的爆燃特性进行了定量和定性研究。在理论分析的基础上初步建立了CFD模型,并通过室内爆燃实验对模型进行了验证。将火焰传播特性、压力-时间历史和火焰速度与实验数据进行了比较,结果与实验数据吻合较好。利用该模型对液化天然气加注过程中发生的大规模爆燃火灾进行了火焰发展和超压效应研究。为了获得合适的网格分辨率和时间步长,对网格独立性和时间尺度进行了测试。模拟和比较了两种不同液化天然气蒸气体积分数(10.4%和15.0%)下的爆燃情况。当体积分数为10.4%时,在化学计量混合比附近,火焰传播速度最快。模拟中观察到的高火焰速度与发生超压的薄火焰锋面相耦合。该CFD模型能够捕捉爆燃燃烧的主要特征,并考虑到LNG的火灾危险,可以在处理复杂情况时提供深入的见解。
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引用次数: 1
Building Fire: Experimental and Numerical Studies on Behaviour of Flows at Opening 建筑火灾:开口流动特性的实验与数值研究
IF 0.7 Q3 ENGINEERING, CHEMICAL Pub Date : 2019-01-21 DOI: 10.1155/2019/2535073
Philippe Onguene Mvogo, R. Mouangue, Justin Tégawendé Zaida, M. Obounou, H. E. Ekobena Fouda
Compartment fire is conducted by complex phenomena which have been the topics of many studies. During fire incident in a building, damage to occupants is not often due to the direct exposition to flames but to hot and toxic gases resulting from combustion between combustibles and surrounding air. Heat is therefore taken far from the source by combustion products which could involve a rapid spread of fire in the entire building. With the intention of studying the impact of the opening size on the behaviour of fire, experimental and computational studies have been undertaken in a reduced scale room including a single open door. Owing to Froude modelling, the obtained results have been transposed into full scale results. In accordance with experiments, numerical studies enabled the investigation of the influence of the ventilation factor on velocities of incoming air and outgoing burned gases and on areas of the surfaces crossed by these fluids during full-developed fire. Comparison of the deduced mass flow rates with the literature reveals an approval agreement.
舱室火灾是由复杂的现象引起的,一直是许多研究的主题。在建筑物发生火灾时,对居住者的伤害通常不是由于直接暴露在火焰中,而是由于可燃物与周围空气之间燃烧产生的热有毒气体。因此,热量被燃烧产物从源头带走,这可能会导致整个建筑物的火势迅速蔓延。为了研究开口尺寸对火灾行为的影响,实验和计算研究已经在一个缩小的房间进行,包括一个单开的门。由于采用了弗劳德模型,得到的结果被转换成全尺寸的结果。根据实验,数值研究能够调查通风系数对进入空气和流出燃烧气体的速度的影响,以及在充分发展的火灾中这些流体穿过的表面面积的影响。将推导出的质量流率与文献进行比较,得到了一致的结果。
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引用次数: 5
Review of Oxidation of Gasoline Surrogates and Its Components 汽油替代物及其组分氧化研究进展
IF 0.7 Q3 ENGINEERING, CHEMICAL Pub Date : 2018-12-06 DOI: 10.1155/2018/8406754
J. Piehl, A. Zyada, L. Bravo, O. Samimi-Abianeh
There has been considerable progress in the area of fuel surrogate development to emulate gasoline fuels’ oxidation properties. The current paper aims to review the relevant hydrocarbon group components used for the formulation of gasoline surrogates, review specific gasoline surrogates reported in the literature, outlining their utility and deficiencies, and identify the future research needs in the area of gasoline surrogates and kinetics model.
在模拟汽油燃料氧化性能的燃料替代物开发方面已经取得了相当大的进展。本文综述了用于汽油替代品配方的相关烃基组分,综述了文献中报道的特定汽油替代品,概述了它们的用途和不足,并确定了汽油替代品和动力学模型领域未来的研究需求。
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引用次数: 25
Coal and Biomass Combustion 煤与生物质燃烧
IF 0.7 Q3 ENGINEERING, CHEMICAL Pub Date : 2018-11-29 DOI: 10.1155/2018/9654923
H. Jin, K. Luo, O. Stein, H. Watanabe, X. Ku
Coal combustion is the largest source of global energy consumption and electricity generation worldwide now and will remain so in the foreseeable future, although coal is also one of the major sources of air pollution. Increasing the efficiency of coal-fired power plants across the world will greatly reduce air pollution and extend the lifetime of our coal resources. The combustion of solid biomass fuels as a renewable energy source has grown significantly in the last decade, principally because it can be used to replace fossil fuels (coal, oil, and natural gas). For this special issue of the Journal of Combustion, we have invited researchers to focus on the combustion of solid fuels and their related processes in power generation. The submitted papers cover a diversity of aspects reflecting the latest progress in the field. These include integrating the supercritical CO 2 Brayton cycle with the coal-fired circulating fluidized-bed boiler, coal and biomass cofiring systems, combustion kinetics of biomass materials, thermal improvement and combustion kinetics of enriched coal, and Computed Tomography of Chemiluminescence (CTC) for turbulent industrial flame reconstruction. Biomass appears to be a promising source of power generation and about half of the papers focus on the biomass related fields, including the combustion kinetic characteristics of wood powder and pellets, as well as the combustion process. Although some methods to utilize pure biomass have been developed (e.g., pyrolysis, gasification, and combustion), the coal and biomass cofiring system is still the most important technology for biomass energy conversion. In this special issue, both of the final published papers on biomass utilization pay attention to the coal and biomass cofiring process, implying that coal combustion is still difficult to be entirely replaced in energy generation. Regarding the methods used in the published research, both experimental and numerical methods show their advantages in different fields. In this special issue, the combustion kinetics of different materials were studied experimentally and numerical research was carried out to study the combustion processes. Computed Tomography of Chemiluminescence (CTC) for turbulent industrial flame reconstruction was also included in the current issue, which may become a useful tool for researchers and scientists for studying flame structure and evolution.
煤炭燃烧是目前全球能源消耗和发电的最大来源,在可预见的未来仍将如此,尽管煤炭也是空气污染的主要来源之一。提高全球燃煤电厂的效率将大大减少空气污染,延长煤炭资源的使用寿命。固体生物质燃料作为一种可再生能源的燃烧在过去十年中显著增长,主要是因为它可以用来取代化石燃料(煤、石油和天然气)。在本期《燃烧杂志》的特刊中,我们邀请了研究人员关注固体燃料的燃烧及其在发电中的相关过程。提交的论文涵盖了反映该领域最新进展的各个方面。其中包括将超临界co2布雷顿循环与燃煤循环流化床锅炉、煤和生物质共燃系统、生物质材料的燃烧动力学、富集煤的热改进和燃烧动力学以及用于湍流工业火焰重建的化学发光计算机断层扫描(CTC)相结合。生物质似乎是一种很有前途的发电来源,大约一半的论文集中在生物质相关领域,包括木粉和颗粒的燃烧动力学特性,以及燃烧过程。虽然已经开发了一些利用纯生物质的方法(如热解、气化和燃烧),但煤与生物质共燃系统仍然是生物质能源转化的最重要技术。在本期特刊中,最后发表的两篇关于生物质利用的论文都关注了煤与生物质共燃过程,这意味着在能源生产中,煤炭燃烧仍难以完全取代。在已发表的研究中使用的方法中,实验方法和数值方法在不同的领域都显示出各自的优势。本特刊对不同材料的燃烧动力学进行了实验研究和数值研究。本文还介绍了用于湍流工业火焰重建的化学发光计算机断层扫描技术(CTC),它可能成为研究人员和科学家研究火焰结构和演化的有用工具。
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引用次数: 2
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Journal of Combustion
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