Proceedings of the Combustion Institute最新文献_第8页

In-Situ Adaptive Manifolds for soot evolution in non-adiabatic turbulent reacting flows 非绝热湍流反应流中烟尘演化的原位自适应流形

IF 5.2 2区工程技术 Q2 ENERGY & FUELS

Proceedings of the Combustion Institute

Pub Date : 2025-01-01 DOI: 10.1016/j.proci.2025.105824

Matthew X. Yao, Israel J. Bonilla, S. Trevor Fush, Michael E. Mueller

To reduce the computational cost of simulations of turbulent reacting flows, manifold-based combustion models are often employed. In these models, the thermochemical state is projected onto a low-dimensional manifold, which can be computed separately from the flow solver. Traditionally, the model involves the pretabulation of solutions to a set of manifold equations, which are obtained a priori. The inclusion of soot and emissions introduces additional physics due to the importance of radiation heat losses. To account for the effects of heat loss, the number of table dimensions necessarily increases. Consequently, these tables can become very memory intensive and include many thermochemical states that may not even be accessed during the simulation. To reduce this memory burden, the concept of In-Situ Adaptive Manifolds (ISAM) has recently been proposed. Within this framework, necessary manifold solutions are computed on-the-fly and stored for lookup using In-Situ Adaptive Tabulation (ISAT). In this work, ISAM is coupled to a soot model based on the Hybrid Method of Moments (HMOM) model. To incorporate heat losses, the manifold equations are augmented with an equation for the heat loss parameter

H

, which is also evolved in the LES flow solver. The manifold equations are formulated based on a quasi-steady assumption, and a model heat loss source term is multiplied by a constant

Ω

to account for varying magnitudes of radiation heat losses from the gas-phase and soot. During runtime, the

H

field from the LES must be matched by ISAM to produce the correct thermochemical state. An iterative procedure is developed to obtain the correct value of

Ω

to ensure consistency of the heat loss parameter between LES and ISAM. The model is demonstrated on the Sandia Sooting Flame. Compared to traditional precomputed tables, ISAM is shown to provide significant memory savings at a minor increase in the computational cost, which is sensitive to the initial guesses for the iterative approach for matching

H

.

为了减少紊流反应流模拟的计算成本，通常采用基于流管的燃烧模型。在这些模型中，热化学状态被投射到一个低维流形上，它可以与流求解器分开计算。传统上，该模型涉及一组流形方程的解的预制式，这些解是先验获得的。由于辐射热损失的重要性，烟尘和排放物的包含引入了额外的物理。为了考虑热损失的影响，表尺寸的数量必然增加。因此，这些表可能会占用大量内存，并且包含许多在模拟过程中甚至可能无法访问的热化学状态。为了减少这种内存负担，最近提出了原位自适应流形（ISAM）的概念。在这个框架内，必要的流形解被实时计算并存储，以便使用原位自适应制表（ISAT）进行查找。在这项工作中，ISAM与基于混合矩量法（HMOM）模型的煤烟模型相耦合。为了考虑热损失，流形方程中增加了热损失参数H的方程，该方程也在LES流求解器中演化。流形方程是基于准稳定假设而制定的，模型热损失源项乘以常数Ω来考虑气相和煤烟辐射热损失的变化幅度。在运行期间，来自LES的H场必须与ISAM匹配以产生正确的热化学状态。为了保证LES和ISAM热损失参数的一致性，建立了求解Ω的迭代过程。该模型在桑迪亚煤烟火焰上进行了验证。与传统的预计算表相比，ISAM在计算成本小幅增加的情况下提供了显著的内存节省，这对匹配H的迭代方法的初始猜测很敏感。

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引用次数: 0

Exploring discrepancies among theoretical and experimental data for NH2 + CH4 ⇌ NH3 + CH3 探讨NH2 + CH4 + NH3 + CH3的理论与实验数据的差异

IF 5.2 2区工程技术 Q2 ENERGY & FUELS

Proceedings of the Combustion Institute

Pub Date : 2025-01-01 DOI: 10.1016/j.proci.2025.105809

Ella C. Kane , Joe Lee , Jonathan M. Pankauski , Rodger E. Cornell , Michael P. Burke

Ammonia has been of great recent interest as a carbon-free fuel amidst growing concern around greenhouse gas emissions. Ammonia’s poor combustion characteristics have motivated exploration of co-combustion of ammonia and various co-fuels to yield more favorable combustion behavior. When the co-fuel is a hydrocarbon, the co-combustion kinetics can involve a host of reactions between nitrogen-containing species and carbon-containing species that are not otherwise important during combustion of either fuel when pure. Recent studies have highlighted hydrogen abstraction from hydrocarbons by NH

_{2}

as an important class of such C-N interaction mechanisms. However, even for NH

_{2}

+ CH

_{4}

⇌

NH

_{3}

+ CH

_{3}

, which is among the simplest and most studied reactions of this reaction class, there is significant disagreement among rate constants from various theoretical and experimental studies. Of particular note, two shock tube studies at high temperatures reported rate constant determinations that differ by a factor of

\sim

4. Interestingly, both studies use thermal decomposition of a precursor following the shock wave to form NH

_{2}

and then monitor NH

_{2}

time profiles, but they use different precursors—raising the possibility that secondary reactions unique to each precursor (methylamine or hydrazine) may contribute to the discrepancies. The disagreement between these experimental studies, along with similar disagreement among theoretical studies, makes this an interesting system for analysis using MultiScale Informatics (MSI), which has previously identified consistent explanations of apparently inconsistent data for other reactions. We find, however, that the data reported in one of the shock tube studies are not internally consistent. An MSI model based on the other experimental and theoretical data is found to be consistent with all other data (including for the methylamine precursor) and essentially upholds the other experimental determinations despite significant revisions to the secondary chemistry since the original analysis, including further insights into methylamine chemistry described herein.

在人们对温室气体排放日益关注的背景下，氨作为一种无碳燃料最近引起了人们的极大兴趣。氨的不良燃烧特性促使人们探索氨与各种共燃燃料的共燃，以获得更有利的燃烧行为。当共燃料为碳氢化合物时，共燃烧动力学可能涉及含氮物质和含碳物质之间的一系列反应，这些反应在纯燃料的燃烧过程中并不重要。最近的研究表明，NH2从碳氢化合物中提取氢是一类重要的碳氮相互作用机制。然而，即使是这类反应中最简单、研究最多的NH2 + CH4 + NH3 + CH3反应，其速率常数在各种理论和实验研究中也存在显著差异。特别值得注意的是，两项高温激波管研究报告的速率常数测定结果相差约4倍。有趣的是，这两项研究都使用了冲击波后前体的热分解来形成NH2，然后监测NH2的时间分布，但它们使用了不同的前体，这增加了每种前体（甲胺或肼）特有的二次反应可能导致差异的可能性。这些实验研究之间的分歧，以及理论研究之间的类似分歧，使得使用多尺度信息学（MSI）进行分析成为一个有趣的系统，该系统先前已经确定了其他反应的明显不一致数据的一致解释。然而，我们发现，其中一项激波管研究报告的数据在内部并不一致。基于其他实验和理论数据的MSI模型被发现与所有其他数据（包括甲胺前体）一致，并且基本上支持其他实验确定，尽管自原始分析以来对二级化学进行了重大修订，包括本文所述的对甲胺化学的进一步见解。

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引用次数: 0

Effect of water vapor on nitriding of stainless steel walls induced by ammonia flames 水蒸气对氨火焰诱导不锈钢壁渗氮的影响

IF 5.2 2区工程技术 Q2 ENERGY & FUELS

Proceedings of the Combustion Institute

Pub Date : 2025-01-01 DOI: 10.1016/j.proci.2025.105831

Yujian Xing, Minhyeok Lee, Yuji Suzuki

Ammonia is a promising candidate fuel for future carbon-free energy systems. However, significant interactions between ammonia flames and metal walls in combustors result in “unwanted” nitriding, compromising safe operation and shortening the lifespan of combustion systems. The substantial water vapor generated during ammonia combustion further influences this flame-wall interaction. This study examines the effect of water vapor on two interconnected processes: the heterogeneous decomposition of ammonia and the nitriding of stainless steel induced by ammonia flames. Ammonia conversion ratios due to heterogeneous decomposition on stainless steel surfaces were measured in a flow reactor under varying water vapor concentrations, and the mechanisms underlying the impact of water vapor on both surface reactivity and surface nitriding were examined. Additionally, the effect of water vapor on nitriding induced by ammonia flames was investigated. The findings confirm that the oxidation effect of water vapor reduces surface reactivity for heterogeneous ammonia decomposition, making it the primary factor behind the hindering effect on nitriding during ammonia combustion.

氨是未来无碳能源系统中很有前途的候选燃料。然而，在燃烧器中，氨火焰和金属壁之间的显著相互作用导致“不必要的”氮化，危及安全运行并缩短燃烧系统的寿命。氨燃烧过程中产生的大量水蒸气进一步影响了这种火焰-壁面相互作用。本研究考察了水蒸气对两个相互关联的过程的影响：氨的非均相分解和氨火焰引起的不锈钢氮化。在流动反应器中测量了不同水蒸气浓度下不锈钢表面非均相分解引起的氨转化率，并探讨了水蒸气对表面反应性和表面氮化的影响机制。此外，还研究了水蒸气对氨火焰致氮化的影响。研究结果证实，水蒸气的氧化作用降低了非均相氨分解的表面反应性，是氨燃烧过程中阻碍氮化的主要因素。

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引用次数: 0

On the performance of the joint velocity-scalar PDF method near walls 近壁节理速度-标量PDF法的性能研究

IF 5.2 2区工程技术 Q2 ENERGY & FUELS

Proceedings of the Combustion Institute

Pub Date : 2025-01-01 DOI: 10.1016/j.proci.2025.105838

Tin-Hang Un , Salvador Navarro-Martinez

Wall modelling of turbulent reacting flows is crucial for applications such as aero-engine simulations. The velocity-scalar probability density function (PDF) method has proven effective for modelling flames in complex combustion regimes, but its application near walls is computationally expensive due to the need for wall-resolving grids, even with the aid of adaptive mesh refinement. This study aims to reduce computational cost by employing a modern wall model in large eddy simulations (LES). We demonstrate that a simple subgrid model is sufficient for a wide range of wall distances, though modification to the stochastic forcing is needed to prevent spurious pressure formation near walls. The proposed wall-modelled stochastic fields framework significantly improves upon existing methods without wall modelling. It also highlights the potential for cost savings by using wall-modelled LES-PDF. For this purpose, the Eulerian stochastic fields framework is particularly suited as it can integrate with most existing LES wall models with minimal modifications.

紊流反应流动的壁面建模对于航空发动机模拟等应用至关重要。速度-标量概率密度函数（PDF）方法已被证明对复杂燃烧状态下的火焰建模是有效的，但由于需要壁面解析网格，即使借助自适应网格细化，其在壁面附近的应用计算成本也很高。本研究旨在通过在大涡模拟（LES）中采用现代壁面模型来降低计算成本。我们证明了一个简单的子网格模型足以适应大范围的壁面距离，尽管需要对随机强迫进行修改以防止壁面附近的虚假压力形成。所提出的壁面建模随机场框架显著改进了现有的无壁面建模方法。它还强调了使用壁式LES-PDF节省成本的潜力。为此，欧拉随机场框架特别适合，因为它可以与大多数现有的LES壁模型进行最小的修改。

引用次数: 0

Transported PDF and MMC modelling of local extinction in turbulent piloted NH3/H2/N2-air jet flames 湍流NH3/H2/ n2射流火焰局部熄灭的传输PDF和MMC模型

IF 5.2 2区工程技术 Q2 ENERGY & FUELS

Proceedings of the Combustion Institute

Pub Date : 2025-01-01 DOI: 10.1016/j.proci.2025.105843

Lu Tian , Andrew P. Wandel , R.P. Lindstedt

Ammonia is a potential alternative fuel for decarbonising hard-to-abate sectors. Practical utilisation is hindered by unfavourable combustion properties that include slow chemical kinetics, low flame speeds and high nitrogen oxide emissions. These challenges are further exacerbated by local extinction in turbulent flames driven by turbulence–chemistry interactions. This study uses the joint-scalar transported probability density function (JPDF) and Multiple Mapping Conditioning (MMC) frameworks, both of which inherently provide a closed chemical source term treatment, to investigate such interactions in two turbulent ammonia–hydrogen–nitrogen–air flames exhibiting local extinction. The flames have been experimentally characterised and correspond to 59.2% (Flame D) and 88.9% (Flame F) of the blow-off velocity. The performance of JPDF methods, featuring Modified Curl’s (JPDF-MC) and Euclidean Minimum Spanning Tree (JPDF-EMST) closures for transport in scalar space, is evaluated alongside the MMC-based MMC-MC and MMC-IEM models for predicting local extinction. All four models provide generally good predictions for Flame D, but show noticeable differences for Flame F, particularly where local extinction is extensive. The JPDF-EMST closure predicts the least amount of local extinction, followed by MMC-IEM, with JPDF-MC and MMC-MC providing closer agreement with experimental data. The presence of NH₃ containing fluid in fuel lean regions for Flame F is related to local extinction events with computed results found to be sensitive to very minor changes (

≃ 1 %

) in the fuel jet exit velocity. The MMC-MC formulation improves predictions of temperature PDFs in fuel-rich regions and OH PDFs in fuel-lean regions due to the enforced localness of transport in scalar space.

对于难以减排的行业来说，氨是一种潜在的替代燃料。化学动力学慢、火焰速度低、氮氧化物排放高等不利的燃烧特性阻碍了实际应用。湍流-化学相互作用驱动的湍流火焰局部灭绝进一步加剧了这些挑战。本研究使用联合标量传递概率密度函数（JPDF）和多重映射条件（MMC）框架，这两个框架都提供了一个封闭的化学源项处理，来研究两种具有局部熄灭的氨-氢-氮-空气湍流火焰中的这种相互作用。火焰经过实验表征，对应于吹出速度的59.2%（火焰D）和88.9%（火焰F）。采用修正旋度（JPDF- mc）和欧几里得最小生成树（JPDF- emst）闭包的JPDF方法在标量空间中的传输性能，与基于mmc的MMC-MC和MMC-IEM模型一起用于预测局部灭绝。所有四种模型对火焰D的预测总体上都很好，但对火焰F的预测却存在明显差异，特别是在局部灭绝范围广泛的情况下。JPDF-EMST闭合预测的局部灭绝量最小，其次是MMC-IEM， JPDF-MC和MMC-MC与实验数据更接近。火焰F燃料稀薄区域含NH3流体的存在与局部熄灭事件有关，计算结果发现燃料射流出口速度的微小变化（≈1%）很敏感。由于标量空间中输运的局域性，MMC-MC公式改进了富燃料区域的温度pdf和贫燃料区域的OH pdf的预测。

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引用次数: 0

Semi-empirical lumped models of polymer pyrolysis for poly(methyl methacrylate) and polyoxymethylene 聚甲基丙烯酸甲酯和聚甲醛聚合物热解的半经验集总模型

IF 5.2 2区工程技术 Q2 ENERGY & FUELS

Proceedings of the Combustion Institute

Pub Date : 2025-01-01 DOI: 10.1016/j.proci.2025.105807

Tim J. Mallo, Adam Dumas, Phillip R. Westmoreland

Quantitative lumped-kinetics models are constructed for pyrolysis of poly(methyl methacrylate) (PMMA) and polyoxymethylene (POM) by using known reaction classes to describe mass loss (volatiles loss) by purely 1st-order decomposition rates, averting the need for molar- or number-based concentrations. These semi-empirical models will aid in establishing fundamental kinetics of polymer decomposition for solid rocket fuels and thermal recycling. Simultaneous thermogravimetric analysis and differential scanning calorimetry (TGA-DSC) are applied to measure mass-loss and heat-consumption rates and the influences of heating rate, sample size, and end groups as a basis for modeling. This combination of rate data and products is useful for proposing pathways and establishing mechanisms. PMMA and POM homopolymers were selected for base-case pyrolysis studies due to their relatively simple structures and their tendencies to yield primarily monomer. For comparison, kinetics was also measured for POM copolymer, where -CH₂CH₂O- units are interspersed among the -CH₂O- units.

Two-, three-, and four-lumped-reaction parameterized models are presented for pyrolysis rates and yields from POM homopolymer, POM copolymer, and PMMA, respectively. The lumped reactions correspond to temperature regions that are dominated by a single type of first-order reaction, each with a mass fractional yield of volatiles, an Arrhenius pre-exponential factor, and an activation energy. The first, lowest-temperature lump may be pericyclic reactions to molecular intermediates, or the main chain or weakly bound end groups or side groups may homolytically scission. Polymer-radical fragments could be trapped by recombination and be too large to be volatile. If enough polymeric radicals are formed, beta-scission into monomers can be rate-limiting for volatiles formation, and at higher temperatures, homolytic scission would be rate-limiting. At highest temperatures, stages can be rate-limited by internal H-abstraction or termination via exothermic reactions to make strongly bound char residues.

本文建立了聚甲基丙烯酸甲酯（PMMA）和聚甲醛（POM）热解的定量集总动力学模型，通过使用已知的反应类别来描述纯一阶分解速率的质量损失（挥发物损失），避免了对摩尔或数字浓度的需要。这些半经验模型将有助于建立固体火箭燃料的聚合物分解和热回收的基本动力学。同时采用热重分析和差示扫描量热法（TGA-DSC）测量质量损失和热消耗率以及加热速率、样本量和端组的影响，作为建模的基础。这种速率数据和产物的结合对于提出途径和建立机制是有用的。选择PMMA和POM均聚物进行基础案例热解研究，是因为它们的结构相对简单，并且倾向于主要生成单体。为了比较，还测量了POM共聚物的动力学，其中- ch2ch2o -单元穿插在- ch2o -单元之间。分别建立了聚甲醛均聚物、聚甲醛共聚物和PMMA热解速率和产率的二、三、四集总反应参数化模型。集中反应对应于由单一类型的一阶反应主导的温度区域，每个温度区域都有挥发物的质量分数产率、阿伦尼乌斯指数前因子和活化能。首先，温度最低的团块可能是分子中间体的周环反应，或者主链或弱结合的端基或侧基可能均聚断裂。聚合物自由基碎片可能通过重组被捕获，并且太大而不挥发。如果形成了足够多的聚合自由基，裂解成单体对挥发物的形成是限速的，在较高的温度下，均裂裂解是限速的。在最高温度下，阶段可以通过内部h萃取或通过放热反应终止以产生强结合的炭残基来限制速率。

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引用次数: 0

NOx production in a canonical Micromix hydrogen flame 典型Micromix氢火焰中NOx的产生

IF 5.2 2区工程技术 Q2 ENERGY & FUELS

Proceedings of the Combustion Institute

Pub Date : 2025-01-01 DOI: 10.1016/j.proci.2025.105793

Zisen Li , Philippe Versailles , Martin Vabre , Evatt R. Hawkes , Bruno Savard

A direct numerical simulation (DNS) of two reactive hydrogen jets in an air crossflow at representative gas turbine conditions is performed. The thermochemical state nominally corresponds to a non-autoignitive, partially premixed turbulent flame. The analysis focuses on the instantaneous and conditional mean flame structures, and the NO

_{x}

production mechanism. The results show that the flame along the jet centerline plane features two branches, one stabilized on the leeward side and a second lifted above the jet trajectory. The former is located close to the jet exit where the advective velocity is low due to the recirculation zone and the boundary layer. The hot products of the leeward flame are transported downstream and interact with the windward non-premixed flame branch. An analysis of the flame index indicates that both, non-premixed and premixed, flames coexist and undergo strong interactions. Through reaction pathway analyses, it is demonstrated that the production of NO

_{x}

over the whole domain proceeds mainly through the thermal (Zel’dovich) route; this is the primary pathway in near-stoichiometric regions, while the N₂O and NNH routes are locally dominant in lean and rich premixed regions, respectively. Moreover, a post-flame (

T > 1850

K) residence time is used to track the time spent by fluid parcels in regions where thermal-NO prevails. This reveals that large quantities of NO produced through the thermal route near stoichiometry are transported in rich zones, resulting in a strong departure from 1D laminar reference cases.

对具有代表性的燃气轮机条件下空气横流中两个反应氢射流进行了直接数值模拟。名义上，热化学状态对应于非自燃的、部分预混的湍流火焰。重点分析了瞬时和条件平均火焰结构，以及NOx的产生机理。结果表明，沿射流中心线平面的火焰具有两个分支，一个稳定在背风面，另一个上升到射流轨迹上方。前者靠近射流出口，由于再环流区和边界层的存在，平流速度较低。背风火焰的热产物被输送到下游，并与迎风的非预混火焰分支相互作用。火焰指数分析表明，非预混和预混两种火焰共存，且相互作用强。通过反应路径分析，表明整个区域NOx的生成主要通过热（Zel’dovich）途径进行；这是近化学计量区域的主要途径，而N2O和NNH途径分别在贫预混合区和富预混合区占局部优势。此外，火焰后（T>1850 K）停留时间用于跟踪流体包裹在热无盛行的地区所花费的时间。这表明，通过接近化学计量的热路径产生的大量NO在富区运输，导致与一维层流参考情况的强烈偏离。

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引用次数: 0

A-priori and a-posteriori studies of finite-rate chemistry based combustion models for turbulent spherical lean premixed hydrogen/air flames 基于有限速率化学的湍流球形稀薄预混氢/空气火焰燃烧模型的先验和后验研究

IF 5.2 2区工程技术 Q2 ENERGY & FUELS

Proceedings of the Combustion Institute

Pub Date : 2025-01-01 DOI: 10.1016/j.proci.2025.105815

Yiqing Wang, Chao Xu, Riccardo Scarcelli

Lean hydrogen combustion has emerged as a promising pathway to achieve high efficiency and low emissions in various energy and propulsion systems. However, the development of accurate turbulent combustion models for lean premixed hydrogen flames remains a significant challenge due to the complicated interplay between thermodiffusive instabilities and turbulence. In this study, the spherically expanding flame of a lean H

_{2}

/air mixture is simulated in a homogeneous isotropic turbulence environment at engine-relevant conditions using both direct numerical simulation (DNS) and large-eddy simulation (LES). These simulations enable both a-priori and a-posteriori evaluations of finite-rate chemistry (FRC) based turbulent combustion models within the LES framework, with the focus on their abilities to predict turbulent burning velocity (

S_{T}

). Two combustion models are investigated in particular: the well-stirred reactor (WSR) model and the thickened flame model (TFM). A-priori evaluation is first carried out for the WSR model based on DNS results. It is found that WSR tends to over-predict

S_{T}

, which can be reproduced from a 1-D twin-premixed stretched laminar flame at high stretch rates. This indicates that such over-prediction is resulted from the response of local reaction rates to the LES filtering operation, rather than turbulence. In contrast, the a-posteriori test through LES shows that

S_{T}

is significantly under-predicted by the WSR model. This is because the interactions between flame instabilities and turbulence are not sufficiently captured in LES/WSR, which leads to reduced flame wrinkling and stretching factors. The performance of the TFM model is also evaluated a-posteriori in LES. Results show that with flame thickening, the local flame reactivity is enhanced, while the flame wrinkling is reduced, resulting in limited improvement on the prediction of

S_{T}

by LES/TFM. By introducing a proper correction factor to the efficiency function, the prediction by TFM can be largely improved, but the instantaneous

S_{T}

is still not well reproduced. These findings highlight that caution needs to be taken when interpreting the a-priori analysis results for FRC-based turbulent combustion models. Results from this study further provide novel insights into potential pathways to improve turbulent combustion models such as TFM, especially in the context of turbulent lean premixed hydrogen flames.

在各种能源和推进系统中，稀氢燃烧已成为一种实现高效率和低排放的有前途的途径。然而，由于热扩散不稳定性与湍流之间复杂的相互作用，开发精确的稀预混氢火焰湍流燃烧模型仍然是一个重大挑战。在本研究中，采用直接数值模拟（DNS）和大涡模拟（LES）两种方法，对发动机相关条件下均匀各向同性湍流环境下稀薄H2/空气混合物的球形膨胀火焰进行了模拟。这些模拟可以在LES框架内对基于有限速率化学（FRC）的湍流燃烧模型进行先验和事后评估，重点是它们预测湍流燃烧速度（ST）的能力。重点研究了两种燃烧模型：均匀搅拌反应器（WSR）模型和增厚火焰模型（TFM）。首先基于DNS结果对WSR模型进行先验评价。发现WSR倾向于过度预测ST，这可以从一维双预混拉伸层流火焰在高拉伸速率下再现。这表明这种过度预测是由局部反应速率对LES滤波操作的响应造成的，而不是湍流。相比之下，通过LES进行的后验检验表明，WSR模型明显低估了温度。这是因为在LES/WSR中没有充分捕捉到火焰不稳定性和湍流之间的相互作用，从而降低了火焰的起皱和拉伸因素。在LES中，TFM模型的性能也进行了后验评估。结果表明，随着火焰增厚，局部火焰反应性增强，而火焰起皱减少，导致LES/TFM预测ST的改进有限。通过在效率函数中引入适当的校正因子，TFM的预测效果得到了很大的改善，但仍不能很好地再现瞬时温度。这些发现强调，在解释基于frc的湍流燃烧模型的先验分析结果时需要谨慎。这项研究的结果进一步为改进湍流燃烧模型（如TFM）的潜在途径提供了新的见解，特别是在湍流稀薄预混氢火焰的背景下。

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引用次数: 0

Interaction and ignition process of multiple injections of oxygenated fuels in an optical, heavy-duty diesel engine 光学重型柴油机多次注入含氧燃料的相互作用和点火过程

IF 5.2 2区工程技术 Q2 ENERGY & FUELS

Proceedings of the Combustion Institute

Pub Date : 2025-01-01 DOI: 10.1016/j.proci.2025.105820

Kaylyn Buchanan , Akash Dhotre , Daipayan Sen , Ales Srna , Rajavasanth Rajasegar

Poly-oxymethylene ethers (OMEs) are a class of highly oxygenated synthetic fuels that offer promising pathways for decarbonizing transportation and enhancing energy security. Their favorable ignition properties, high cetane number, and soot-free combustion characteristics make them attractive alternatives to conventional diesel. However, their lower energy density, weaker negative temperature coefficient (NTC) behavior, and rapid mixing due to fuel-bound oxygen introduce complex interactions during combustion, particularly under multiple-injection strategies common in modern diesel engines. This study investigates the ignition and combustion behavior of OMEs compared to a conventional non-oxygenated surrogate fuel (n-dodecane) under various pilot-main injection configurations using a heavy-duty, optical single-cylinder engine. A suite of diagnostics, including apparent heat release rate (AHRR) analysis and simultaneous planar laser-induced fluorescence (PLIF) imaging of formaldehyde (HCHO) and hydroxyl (OH), was employed to capture the low- and high-temperature combustion phases. Experiments were conducted across a matrix of pilot injection durations, dwell times, and EGR dilution levels to evaluate their influence on ignition delay (ID), flame structure, and heat release dynamics. Results show that OME requires longer pilot injections to overcome rapid lean-out and achieve comparable ignition assistance due to its low stoichiometric air–fuel ratio (AFR_ST) and reduced LTHR contribution. A critical minimum injection duration was identified for OME below which the pilot fails to ignite, a behavior not observed with n-dodecane. Despite this, OME displays rapid, volumetric ignition once combustion initiates, owing to favorable mixture stratification from fuel-bound oxygen. A conceptual model is proposed to distinguish ignition regimes based on pilot duration and fuel oxygenation level, explaining the interplay between entrainment-driven mixing, HTHR suppression, and reactive zone formation. The findings enhance understanding of the underlying physics governing multiple injections and provide guidance for optimizing pilot strategies when adapting diesel engines to oxygenated fuels like OME.

聚氧甲基醚（ome）是一类高氧合成燃料，为运输脱碳和增强能源安全提供了有前途的途径。其良好的点火性能，高十六烷值和无烟燃烧特性使其成为传统柴油的有吸引力的替代品。然而，它们较低的能量密度，较弱的负温度系数（NTC）行为，以及由于燃料结合氧导致的快速混合，在燃烧过程中引入了复杂的相互作用，特别是在现代柴油发动机中常见的多次喷射策略下。本研究使用重型光学单缸发动机，在不同的先导主喷射配置下，与传统的非含氧替代燃料（正十二烷）相比，研究了内燃机的点火和燃烧行为。采用一套诊断方法，包括表观热释放率（AHRR）分析和甲醛（HCHO）和羟基（OH）的同步平面激光诱导荧光（PLIF）成像，来捕捉低温和高温燃烧相。实验采用了中试喷射时间、停留时间和EGR稀释水平，以评估它们对点火延迟（ID）、火焰结构和热释放动力学的影响。结果表明，由于OME具有较低的化学计量空燃比（AFRST）和较低的LTHR贡献，因此需要更长的先导喷射时间来克服快速倾斜，并达到相当的点火辅助效果。确定了OME的临界最小喷射持续时间，低于该时间先导剂无法点燃，而正十二烷没有观察到这种行为。尽管如此，一旦燃烧开始，由于燃料结合氧形成有利的混合物分层，OME显示出快速的体积点火。提出了一个概念模型，根据中试时间和燃料氧合水平来区分点火模式，解释了夹带驱动混合、HTHR抑制和反应区形成之间的相互作用。这些发现加深了人们对多次喷射的基本物理原理的理解，并为柴油发动机适应含氧燃料（如OME）时优化试验策略提供了指导。

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引用次数: 0

Analysis of thermodiffusive instabilities and flame front wrinkling in a hydrogen-fueled engine 氢燃料发动机热扩散不稳定性及火焰前缘起皱分析

IF 5.2 2区工程技术 Q2 ENERGY & FUELS

Proceedings of the Combustion Institute

Pub Date : 2025-01-01 DOI: 10.1016/j.proci.2025.105884

Pedro Ye, Jannick Erhard, Cooper Welch, Hao Shi, Andreas Dreizler, Benjamin Böhm

This study investigates the interplay between thermodiffusive instabilities (TDI) and flame front wrinkling in a hydrogen-fueled internal combustion engine (ICE). High-speed planar laser-induced fluorescence (LIF) of the SO₂ tracer was employed to visualize flames in an optically accessible, spark-ignited ICE operating under a lean H₂ mixture at 400 rpm and 800 rpm. The results reveal that TDI cells are distinctly more pronounced at 400 rpm and in slower flames, while at 800 rpm, increased turbulence suppresses cell development and enhances overall flame wrinkling. A negative correlation between these two features indicates that TDI cells flourish in less disturbed conditions, whereas turbulence-driven wrinkling disrupts their formation. These findings suggest that at higher, more realistic engine speeds, TDI cell formation is significantly mitigated. However, other instability-driven effects, such as localized heat release variations, wall heat transfer, and flame quenching, may still play a crucial role in H₂ engine combustion. Understanding these interactions is essential for accurately modeling and optimizing hydrogen-fueled ICEs.

研究了氢燃料内燃机（ICE）中热扩散不稳定性（TDI）与火焰前缘起皱之间的相互作用。SO2示踪剂的高速平面激光诱导荧光（LIF）用于在光学可及的火花点燃ICE中观察火焰，该ICE在稀薄H2混合物下运行，转速为400 rpm和800 rpm。结果表明，TDI细胞在400转/分和较慢的火焰中明显更明显，而在800转/分时，增加的湍流抑制了细胞的发育并增强了整体火焰起皱。这两个特征之间的负相关表明TDI细胞在较少干扰的条件下繁殖，而湍流驱动的起皱破坏了它们的形成。这些发现表明，在更高、更现实的发动机转速下，TDI细胞的形成显著减轻。然而，其他不稳定性驱动的效应，如局部热释放变化、壁面传热和火焰淬火，可能仍然在H2发动机燃烧中起着至关重要的作用。了解这些相互作用对于准确建模和优化氢燃料ICEs至关重要。

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引用次数: 0