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| 1 | Analyses of surrogate models for calculating thermophysical properties of aviation kerosene RP-3 at supercritical pressures显示文摘Aviation kerosene is commonly used in combustion and regenerative engine cooling processes in propulsion and power-generation systems,including rocket,scramjet,and advanced gas turbine engines.In this paper,many surrogate models proposed in the open literature are examined for their applicability and accuracy in calculating thermodynamic and transport properties of the China aviation kerosene RP-3 at supercritical pressures,based on the extended corresponding-states methods.The enthalpy change from endothermic decomposition and low heating value from combustion of the jet fuel are also evaluated.Results from a number of simple and representative surrogate models,which contain species components ranging from 1 to10,are analyzed in detail.Data analyses indicate that a surrogate model with four species is the best choice for thermophysical property calculations under the tested conditions,with fluid temperature up to 650 K at various supercritical pressures.The surrogate model is particularly accurate in predicting the pseudo-critical temperature of aviation kerosene RP-3 at a supercritical pressure.A simple surrogate model containing the n-decane species and a surrogate model containing 10 species are the other two acceptable options.The work conducted herein is of practical importance for theoretical analyses and numerical simulations of various physicochemical processes at engine operating conditions. | XU KeKe MENG Hua | 2015 | Science China(Technological Sciences)2015，58，3： | 6 |
| 2 | Large eddy simulation of hydrogen/air scramjet combustion using tabulated thermo-chemistry approach显示文摘Large eddy simulations(LES) have been performed to investigate the flow and combustion fields in the scramjet of the German Aerospace Center(DLR). Turbulent combustion is modeled by the tabulated thermo-chemistry approach in combination with the presumed probability density function(PDF). A b-function is used to model the distribution of the mixture fraction, while two different PDFs, d-function(Model I) and b-function(Model II), are applied to model the reaction progress. Temperature is obtained by solving filtered energy transport equation and the reaction rate of the progress variable is rescaled by pressure to consider the effects of compressibility. The adaptive mesh refinement(AMR) technique is used to properly capture shock waves,boundary layers, shear layers and flame structures. Statistical results of temperature and velocity predicted by Model II show better accuracy than that predicted by Model I. The results of scatter points and mixture fraction-conditional variables indicate the significant differences between Model I and Model II. It is concluded that second moment information in the presumed PDF of the reaction progress is very important in the simulation of supersonic combustion. It is also found that an unstable flame with extinction and ignition develops in the shear layers of bluff body and a fuelrich partially premixed flame stabilizes in the central recirculation bubble. | Cao Changmin Ye Taohong Zhao Majie | 2015 | Chinese Journal of Aeronautics2015，28，5： | 5 |
| 3 | Large eddy simulation of unconfined turbulent swirling flow显示文摘Large eddy simulations(LES) were performed to study the non-reacting flow fields of a Cambridge swirl burner. The dynamic Smagorinsky eddy viscosity model is used as the sub-grid scale turbulence model. Comparisons of experimental data show that the LES results are capable of predicting mean and root-mean-square velocity profiles. The LES results show that the annular swirling flow has a minor impact on the formation of the bluff-body recirculation zone. The vortex structures near the shear layers, visualized by the iso-surface of Q-criterion, display ring structures in non-swirling flow and helical structures in swirling flow near the burner exit. Spectral analysis was employed to predict the occurrence of flow oscillations induced by vortex shedding and precessing vortex core(PVC). In order to extract accurately the unsteady large-scale structures in swirling flow, a three-dimensional proper orthogonal decomposition(POD) method was developed to reconstruct turbulent fluctuating velocity fields. POD analysis reveals that flow fields contain co-existing helical and toroidal shaped coherent structures. The helical structure associated with the PVC is the most energetic dynamic flow structure. The latter toroidal structure associated with vortex shedding has lower energy content which indicates that it is a secondary structure. | ZHANG HongDa HAN Chao YE TaoHong ZHANG JiMin CHEN YiLiang | 2015 | Science China(Technological Sciences)2015，58，10： | 5 |
| 4 | Vapor-liquid equilibria of CH_4, CO_2 and their binary system CH_4 + CO_2: A comparison between the molecular simulation and equation of state显示文摘An accurate knowledge about phase behaviors of CH4,CO2 and their binary mixture is crucial in fields of natural gas liquefaction and refrigeration applications.In this work,two all-atom force fields of Tra PPE-EH and EMP2 were used for the components CH4 and CO2,respectively.Then the vapor-liquid equilibria(VLE)of CH4,CO2 and their binary system were calculated via the NVT-and Np T Gibbs Ensemble Monte Carlo Simulations.Meanwhile the traditional method using Equation of State(Eo S)to correlate the VLE properties was also investigated.The Eo Ss considered in this work were three classic cubic RK,SRK,PR and another advanced molecular-based PC-SAFT equations.For pure components,both molecular simulations and the PC-SAFT Eo S could obtain satisfactory predictions for all the saturated properties.However,the saturated liquid densities calculated by the cubic Eo Ss were not so good.It was also observed that the Tra PPE-EH force field had a good representation for CH4 molecule,while the EMP2 force field was not enough accurate to represent CO2 molecules.For the mixture CH4+CO2,SRK and PR showed the best predictions for the saturated pressure-component property,while good results were also obtained via molecular simulations and PC-SAFT Eo S.It was suggested that special combining rules or binary interaction parameters were important to obtain enough accurate prediction of the mixed phase behavior.Compared with the cubic Eo S,the PC-SAFT and molecular simulation method showed better adaptabilities for both the pure and mixture systems.Besides,the accurate molecular parameters used in the PC-SAFT and molecular simulations could bring about direct and deep understanding about the molecular characteristics. | YANG Zhi GONG Mao Qiong ZHOU Yuan DONG Xue Qiang LI Xiao Dong LI Hui Ya WU Jian Feng | 2015 | Science China(Technological Sciences)2015，58，4： | 2 |
| 5 | Investigation of non-premixed flame combustion characters in GO_2/GH_2 shear coaxial injectors using non-intrusive optical diagnostics显示文摘Single-element combustor experiments are conducted for three shear coaxial geometry configuration injectors by using gaseous oxygen and gaseous hydrogen(GO2/GH2) as propellants. During the combustion process, several spatially and time- resolved non-intrusive optical techniques, such as OH planar laser induced fluorescence(PLIF), high speed imaging, and infrared imaging, are simultaneously employed to observe the OH radical concentration distribution, flame fluctuations, and temperature fields. The results demonstrate that the turbulent flow phenomenon of non-premixed flame exhibits a remarkable periodicity, and the mixing ratio becomes a crucial factor to influence the combustion flame length. The high speed and infrared images have a consistent temperature field trend. As for the OH-PLIF images, an intuitionistic local flame structure is revealed by single-shot instantaneous images. Furthermore, the means and standard deviations of OH radical intensity are acquired to provide statistical information regarding the flame, which may be helpful for validation of numerical simulations in future. Parameters of structure configurations, such as impinging angle and oxygen post thickness, play an important role in the reaction zone distribution. Based on a successful flame contour extraction method assembled with non-linear anisotropic diffusive filtering and variational level-set, it is possible to implement a fractal analysis to describe the fractal characteristics of the non-premixed flame contour. As a result, the flame front cannot be regarded as a fractal object. However, this turbulent process presents a self-similarity characteristic. | DAI Jian YU NanJia CAI GuoBiao | 2015 | Science China(Physics,Mechanics & Astronomy)2015，58，12： | 2 |
| 6 | Large eddy simulation of turbulent premixed and stratified combustion using flame surface density model coupled with tabulation method显示文摘Large eddy simulations(LESs) are performed to investigate the Cambridge premixed and stratified flames, SwB1 and SwB5, respectively. The flame surface density(FSD) model incorporated with two different wrinkling factor models, i.e., the Muppala and Charlette2 wrinkling factor models, is used to describe combustion/turbulence interaction, and the flamelet generated manifolds(FGM) method is employed to determine major scalars. This coupled sub-grid scale(SGS) combustion model is named as the FSD-FGM model. The FGM method can provide the detailed species in the flame which cannot be obtained from the origin FSD model. The LES results show that the FSD-FGM model has the ability of describing flame propagation, especially for stratified flames. The Charlette2 wrinkling factor model performs better than the Muppala wrinkling factor model in predicting the flame surface area change by the turbulence.The combustion characteristics are analyzed in detail by the flame index and probability distributions of the equivalence ratio and the orientation angle, which confirms that for the investigated stratified flame, the dominant combustion modes in the upstream and downstream regions are the premixed mode and the back-supported mode, respectively. | Zhou YU Hongda ZHANG Taohong YE Minming ZHU | 2018 | Applied Mathematics and Mechanics(English Edition)2018，39，12： | 1 |
| 7 | 拉伸层流预混火焰化学热力学建表方法研究显示文摘通过求解物理空间上简化的层流甲烷/空气对撞预混火焰面方程,获得不同当量比下考虑拉伸效应的火焰面高维数据。为更准确地描述流动与燃烧的相互作用,采用基于矩阵分析的主成分分析法(PCA)对火焰面高维数据进行分析,并选用分析出的前两个主成分作为新的建表特征标量,进而构建考虑拉伸效应的层流预混火焰化学热力学表。相比于已有的拉伸层流预混火焰面建表方法,使用PCA方法得到的两个建表特征标量之间不相关,无需条件概率密度信息。同时PCA方法具有一定的通用性,可以推广到不同燃料不同当量比下的拉伸层流预混火焰面建表中。 | 唐鹏 张宏达 叶桃红 于洲 | 2017 | 推进技术2017，38，5： | 0 |
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