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Modelling ignition probability with pairwise mixing-reaction model for flame particle tracking

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Chinese Journal of Aeronautics 2021年第5期34卷 523-534页

作者： Qing XIE zhuyin ren Ke WANG School of Aerospace Engineering Tsinghua UniversityBeijing 100084China Institute for Aero Engine Tsinghua UniversityBeijing 100084China Aero Engine Academy of China Beijing 101300China

Reduced order models for ignition analysis can offer insights into ignition processes and facilitate the combustor *** this study,a Pairwise Mixing-Reaction(PMR)model is formulated to model the interaction between the flame particle and the surrounding cell mixture during Lagrangian flame particle ***,the model accounts for the two-way coupling of mass and energy between the flame particle and the surrounding shell layer by modelling the corresponding turbulent mixing,chemical reaction and evaporation process if *** state of a flame particle,e.g.,burnt,hot gas or extinguished,is determined based on particle *** model can properly describe the ignition process with a spark kernel being initiated in a nonflammable region,which is of practical importance in certain turbine engines and has not been rigorously accounted for by the existing models based on the estimation of local Karlovitz *** model is integrated into an ignition probability analysis platform and is demonstrated for a methane/air bluff-body flame with the flow and fuel/air mixing characteristics being extracted from a non-reacting *** results show that for the spark location being at the extreme fuellean outer shear layer of the recirculation zone,PMR can yield ignition events with a significant number of active flame *** mechanisms for the survival of the initial flame particles and the entrainment of the survived flame particles into the recirculation zone are *** results also show that the ignition probability map from PMR agrees well with the experimental observation:a high ignition probability in the shear layer of the recirculation zone near the mean stoichiometric surface,and low ignition probabilities inside the recirculation zone and the top stagnation region of the recirculation *** parametric study shows that the predicted shape of the ignition progress factor and ignition probability is in general inse

关键词： Bluff-body stabilized flame Igniting process Ignition probability Lagrangian particle tracking Pairwise mixing-reaction

Modeling turbulent transport effects on kernel formation and ?ame propagation in an ignition process

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Chinese Journal of Aeronautics 2019年第4期32卷 895-905页

作者： Linghan KONG zhuyin ren Lingyun HOU School of Aerospace Engineering Tsinghua University

Reliable relighting is crucial for advanced low-emission aero-engine combustors. For forced ignition under highly-turbulent conditions, eddies of sizes being smaller than the flame kernel can affect its formation through penetrating and modifying the kernel structure. In this study, a one-dimensional model for small-scale turbulence on kernel formation is developed through the incorporation of turbulence-induced diffusion in governing equations. With given flow conditions,the spatial and time-dependent turbulent diffusivity is modeled using the idea of residual eddy viscosity. One-dimensional spherical flames of premixed pre-vaporized n-dodecane/air mixtures under high-altitude conditions are simulated to investigate the effects of turbulence. It is revealed that the range of the equivalence ratio for successful turbulent ignition is much narrower than that for laminar ignition. The range decreases with an increased turbulent intensity, and this effect is more pronounced for a low spark energy. In addition, turbulent transport has more pronounced effects on rich mixtures. An analysis on energy budget and species profiles shows that turbulence-induced diffusion enhances the heat loss at the very beginning of the kernel formation process that could lead to ignition failure. After the flame kernel is established, turbulent transport broadens the flame front, enhances the heat release rate, and thereafter increases the flame propagation speed.

关键词： Flame kernel Flame propagation High-altitude ignition Kernel formation probability Turbulence-induced diffusion

A numerical study on flame and large-scale flow structures in bluff-body stabilized flames

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Chinese Journal of Aeronautics 2019年第7期32卷 1646-1656页

作者： Jing CHEN Hua ZHOU zhuyin ren Center for Combustion Energy Tsinghua UniversityBeijing100084China School of Aerospace Engineering Tsinghua UniversityBeijing100084China

Large Eddy Simulations(LES) in conjunction with the Flamelet Progress Variable(FPV) approach have been performed to investigate the flame and large-scale flow structures in the bluff-body stabilized non-premixed flames, HM1 and HM3. The validity of the numerical methods is first verified by comparing the predicted velocity and composition fields with experimental measurements. Then the evolution of the flame and large-scale flow structures is analyzed when the flames approach blow-off. The analysis of instantaneous and statistical data indicates that there exists a shift of the control mechanism in the recirculation zone in the two flames. In the recirculation zone, HM1 flame is mainly controlled by the mixing effect and ignition mainly occurs in the outer shear layer. In HM3 flame, both the chemical reactions and mixing are important in the recirculation zone. The Proper Orthogonal Decomposition(POD) results show that the fluctuations in the outer shear layer are more intense in HM1, while the flow structures are more obvious in the outer vortex structure in HM3, due to the different control mechanism in the recirculation *** further shows that the flow structures in HM1 spread larger in the intense mixing zone due to higher temperature and less extinction.

关键词： Bluff-body stabilized flames Large Eddy Simulation(LES) Large-scale flow structures Proper Orthogonal Decomposition(POD)

Review of Lagrangian stochastic models for turbulent combustion

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Acta Mechanica Sinica 2021年第10期37卷 1467-1488,I0001页

作者： Tianwei Yang Yu Yin Hua Zhou zhuyin ren School of Aerospace Engineering Tsinghua UniversityBeijing100084China Institute for Aero Engine Tsinghua UniversityBeijing100084China

Predictive simulation of the combustion process in engine is crucial to understand the complex underlying physicochemical processes, improve engine performance, and reduce pollutant emissions. Key issues such as the physical modeling of the interaction between turbulence, chemistry and droplets, and the incorporation of the detailed chemistry in high-fidelity simulations of complex flows remain essential though challenging. This paper reviews the transported probability density function method for turbulent dilute spray flames in the dual-Lagrangian framework that shows potential to address some critical modeling issues. An overview is presented for the contributions made within the last decade or so for the three key ingredients for modeling the interaction between turbulence, chemistry and droplets, i.e., micro-mixing, subgrid dispersion and two-phase coupling. Then, various methods for detailed chemistry acceleration are reviewed to address the issue of high computational cost for its use in multidimensional simulations. Finally, some applications of the dual-Lagrangian method in both laboratory-scale and device-scale configurations are provided to demonstrate its capability as well as deficiency at the current stage. Some open modeling challenges are raised and recommended for further investigation.

关键词： Transported probability density function method Large eddy simulation Dual-Lagrangian framework Turbulent spray flames Detailed chemistry

Numerical simulation of turbulent combustion: Scientific challenges

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Science China(Physics,Mechanics & Astronomy) 2014年第8期57卷 1495-1503页

作者： ren zhuyin LU Zhen HOU LingYun LU LiuYan School of Aerospace Tsinghua University Center for Combustion Energy Key Laboratory for Thermal Science and Power Engineering of Ministry of Education Tsinghua University Department of Thermal Engineering Tsinghua University Sibley School of Mechanical & Aerospace Engineering Cornell UniversityIthaca NY 14853 USA GE Global Research Center One research circle Niskayuna NY 12309 USA

Predictive simulation of engine combustion is key to understanding the underlying complicated physicochemical processes,improving engine performance,and reducing pollutant *** issues as turbulence modeling,turbulence-chemistry interaction,and accommodation of detailed chemical kinetics in complex flows remain challenging and essential for highfidelity combustion *** paper reviews the current status of the state-of-the-art large eddy simulation(LES)/probability density function(PDF)/detailed chemistry approach that can address the three challenging modelling *** as a subgrid model for LES is formulated and the hybrid mesh-particle method for LES/PDF simulations is *** the development need in micro-mixing models for the PDF simulations of turbulent premixed combustion is *** the different acceleration methods for detailed chemistry are reviewed and a combined strategy is proposed for further development.

关键词： turbulence-chemistry interaction detailed chemistry probability density function mixing models large eddy simulations

A forced ignition probability analysis method using kernel formation analysis with turbulent transport and Lagrangian flame particle tracking

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Chinese Journal of Aeronautics 2021年第4期34卷 403-415页

作者： Qing XIE zhuyin ren Ke WANG Hongjun LIN Shoutang SHANG Wei XIAO School of Aerospace Engineering Tsinghua UniversityBeijing 100084China Institute for Aero Engine Tsinghua UniversityBeijing 100084China Aero Engine Academy of China Beijing 101300China AECC Shenyang Engine Research Institute Shenyang 110000China AECC Hunan Aviation Powerplant Research Institute Zhuzhou 412000China

A forced ignition probability analysis method is developed for turbulent combustion,in which kernel formation is analyzed with local kernel formation criteria,and flame propagation and stabilization are simulated with Lagrangian flame particle *** kernel formation,the effect of turbulent scalar transport on flammability is modelled through the incorporation of turbulenceinduced diffusion in a spherically outwardly propagating flame kernel *** dependence of flammability limits on turbulent intensities is tabulated and serves as the flammability criterion for kernel *** Lagrangian flame particle tracking,flame particles are tracked in a structured grid with flow fields being interpolated from a Computational Fluid Dynamics(CFD)*** particle velocity follows a Langevin model consisting of a linear drift and an isotropic diffusion *** Karlovitz number is employed for the extinction criterion,which compares chemical and turbulent *** integration of the above two-step analysis approach with non-reacting CFD is achieved through a general interpolation interface suitable for general unstructured CFD *** method is demonstrated for a methane/air bluff-body flame,in which flow and fuel/air mixing characteristics are extracted from a non-reacting *** show that the computed ignition probability map agrees qualitatively with experimental results.A reduction of the ignition probability in the recirculation zone and a high ignition probability on the shear layer of the recirculation zone near the mean stoichiometric surface are well *** tools can facilitate optimization of spark placement and offer insights into ignition processes.

关键词： Bluff-body stabilized flame Igniting process Ignition criterion Ignition probability Lagrangian particle tracking

Explore artificial neural networks for solving complex hydrocarbon chemistry in turbulent reactive flows

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Fundamental Research 2022年第4期2卷 595-603页

作者： Jian An Fei Qin Jian Zhang zhuyin ren Institte for Aero Engine Tsinghua UniversitBejing 100084China Seience and Technology on Combustion Internal Flow and Thermal-structure LaboratoryNorthwesterm Polytechnical UniversityXi'an 710072China

Global warming caused by the use of fossil fuels is a common concern of the world *** is of practical importance to conduct in-depth fundamental research and optimal design for modern engine combustors through However,complex hydrocarbon chemistry,an indispensable component for predictive modeling,is computahigh-fidelity computational fluid dynamics(CFD),so as to achieve energy conservation and emission *** demanding,Its application in simulation-based design optimization,although desirable,is quite *** address this challenge,we propose a methodology for representing complex chemistry with artificial neural networks(ANNs),which are trained with a comprehensive sample dataset generated by the Latin hypercube sampling(LHS)*** a given chemical kinetic mechanism,the thermochemical sample data is able to cover the whole accessible pressure/temperature/species space in various turbulent *** ANN-based model consists of two different layers:the self-organizing map(SOM)and the back-propagation neural network(BPNN).The methodology is demonstrated to represent a 30-species methane chemical *** obtained ANN model is applied to simulate both a non-premixed turbulent flame(DLR_A)and a partially premixed turbulent flame(Flame D)to validate its applicability for different *** show that the ANN-based chemical kinetics can reduce the computational cost by about two orders of magnitude without loss of accuracy,The proposed methodology can successfully construct an ANN-based chemical mechanism with significant ffciency gain and a broad scope of applicability,and thus holds a great potential for complex hydrocarbon fuels.

关键词： Chemical kinetics Turbulent combustion Artificial neural network Machine learning Numerical simulation

A Lagrangian-based flame index for the transported probability density function method

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Theoretical & Applied Mechanics Letters 2022年第1期12卷 30-34页

作者： Zhen Lu Hua Zhou zhuyin ren Yue Yang Hong G.Im State Key Laboratory for Turbulent and Complex Systems College of EngineeringPeking UniversityBeijing 100871China BIC-ESAT Peking UniversityBeijing 100871China Clean Combustion Research Center King Abdullah University of Science and TechnologyThuwal 23955-6900Saudi Arabia Institute of Aero Engine Tsinghua UniversityBeijing 100084China HEDPS-CAPT Peking UniversityBeijing 100871China

We propose a new flame index for the transported probability density function(PDF) method. The flame index uses mixing flux projections of Lagrangian particles on mixture fraction and progress variable directions as the metrics to identify the combustion mode, with the Burke-Schumann solution as a reference. A priori validation of the flame index is conducted with a series of constructed turbulent partially premixed reactors. It indicates that the proposed flame index is able to identify the combustion mode based on the subgrid mixing information. The flame index is then applied the large eddy simulation/PDF datasets of turbulent partially premixed jet flames. Results show that the flame index separate different combustion modes and extinction correctly. The proposed flame index provides a promising tool to analyze and model the partially premixed flames adaptively.

关键词： Flame index Transported probability density function Partially premixed combustion

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湍流燃烧机理和调控的活性子空间分析方法

航空学报 2021年第12期42卷 33-45页

作者：王娜娜解青苏星宇任祝寅清华大学航空发动机研究院北京100084 清华大学燃烧能源中心北京100084

高效、低排放等需求促使发动机燃烧趋于近极限燃烧组织,亟需在稳定可控燃烧方面取得突破。湍流燃烧机理复杂,影响湍流燃烧数值模拟预测的物理化学和初始/边界条件参数众多。但是在该高维映射关系中,预测目标量往往仅在输入参数空间中的... 详细信息

高效、低排放等需求促使发动机燃烧趋于近极限燃烧组织,亟需在稳定可控燃烧方面取得突破。湍流燃烧机理复杂,影响湍流燃烧数值模拟预测的物理化学和初始/边界条件参数众多。但是在该高维映射关系中,预测目标量往往仅在输入参数空间中的少数方向上梯度显著,称之为活跃方向。当活跃方向与空间基的方向不一致时,采用传统的全局敏感性方法难以高效地分析出主控参数以及后续的湍流燃烧机理。而活性子方法可以通过梯度的协方差矩阵特征分解得到上述活跃方向。本文综述了活性子空间方法理论及在湍流燃烧模拟中的应用:即探究海量输入参数空间中的活跃方向,构造低维活性子空间和低维响应面,从而高效地量化模拟不确定性、表征主控物理过程,从而揭示湍流燃烧机理。最后,进一步探讨了基于活性子空间分析方法的湍流燃烧调控。

关键词：活性子空间方法湍流燃烧参数降维主控机制不确定性分析