排序方式: 共有12条查询结果,搜索用时 10 毫秒
1.
Zirwes Thorsten Zhang Feichi Habisreuther Peter Hansinger Maximilian Bockhorn Henning Pfitzner Michael Trimis Dimosthenis 《Flow, Turbulence and Combustion》2021,107(2):517-517
Flow, Turbulence and Combustion - The article Quasi-DNS Dataset of a Piloted Flame with Inhomogeneous Inlet Conditions written by Thorsten Zirwes, Feichi Zhang, Peter Habisreuther, Maximilian... 相似文献
2.
Numerical investigation of the thermal partial oxidation process of Methane in porous media based reformer is performed. A finite volume based CFD code, including radiation modeling, in combination with a detailed chemical kinetics scheme is used to perform the numerical simulation. A heterogeneous approach for the heat transport modeling in porous media (separate coupled energy equations for the gas and solid phases) was used. Validation of the model with experimental data is also performed. The model was able to predict the temperature behavior in the reformer reasonably well. However, the concentrations of H2 and CO were under predicted while the H2O concentration was over predicted. 相似文献
3.
Franziska Hunger Björn Stelzner Dimosthenis Trimis Christian Hasse 《Flow, Turbulence and Combustion》2013,90(4):833-857
An experimental and numerical investigation of a confined laminar inverse diffusion flame (IDF) with pure oxygen as oxidizer and carbon dioxide diluted methane as fuel with a global stoichiometry of partial oxidation processes (equivalence ratio of 2.5) is presented. The present burner setup allows studying both the flame and the post-flame zone in a simplified geometry considering typical operating conditions as found in large-scale gasifiers. This partial oxidation flame setup is characterized by very high temperatures close to the stoichiometric oxidation zone due to oxy-fuel combustion, whereas lower temperatures and slow endothermic post-flame conversion reactions with long residence times are found in the fuel rich post-flame region. The scope of this paper is to investigate different modeling approaches suitable for both regimes by comparing the simulation results to detailed experimental data. Planar OH laser-induced fluorescence (OH-LIF) was performed for measuring the hydroxyl radical in the reaction zone and the results are compared to CFD calculations. Based on this comparison, the necessary level of detail of diffusion flux modeling, which includes Soret and Dufour effects, is analyzed and established. Finally, steady and unsteady non-premixed flamelet approaches based on a single mixture fraction are used in order to study their applicability for both the oxidation and post-flame zone. Significantly different time scales are obtained using different flamelet paths. Their influence on the results is investigated in the steady flamelet and the Lagrangian flamelet approach. 相似文献
4.
Prabal Talukdar F. V. Issendorff D. Trimis C. J. Simonson 《Heat and Mass Transfer》2008,44(6):695-704
Interaction of conduction and radiation in 3D enclosures is carried out with a gray participating media. Application of block
structured grid is shown with the finite volume method (FVM). Radiation modeling is performed with the FVM and is coupled
with an ‘in-house’ code to solve the set of transport equations. The detailed numerical results are presented for a cubical
and a cylindrical enclosure as these results are not available in the literature. The numerical simulation for the cylindrical
enclosure is performed using a block-structured ‘O’ grid. Two additional geometries are considered in order to show the applicability
of the present work. Results of temperature, radiative heat flux and total heat flux distributions are presented for different
optical thicknesses, scattering albedoes, emissivities and conduction–radiation parameters. The 3D results are validated with
the available 2D results or results with pure radiation problems as limiting cases. 相似文献
5.
Research and development work carried out to provide a method to measure accurately instantaneous flow rates in periodically operating injection systems is summarized. The instantaneous flow rate is reconstructed from axial velocity time series measured by a laser Doppler anemometer on the center-line of a capilary pipe flow. The theoretical background, on which the evaluation of the instantaneous flow rate is based is provided. It is shown that the axial mean velocity is sufficient to reconstruct the periodically varying flow rate and the pressure gradient. The application of the proposed method is described and an instrument is suggested that can be employed in many fields where fast, periodically varying flow rates occur and instantaneous information is needed.List of Symbols
C
j
complex Fourier coefficients
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C.C.
complex conjugate of different variables
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D
inner diameter of pipe
-
f
0
repetition frequency of valve motion
-
i
complex unit
-
J
0
Bessel function of zeroth order
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J
l
Bessel function of first order
-
L
distance between valve and measuring volume
-
m
integrated fluid mass within one period
- P/z
mass flow rate
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P/z
pressure gradient along the pipe axis
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p
0,p
n
normalized amplitude of the complex pressure gradient
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r
radial position
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R
pipe radius
-
Re
Reynolds number
-
t
time
-
T
time of the period of the repetition valve opening
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Ta
Taylor number
-
U
axial velocity
-
V
integrated fluid volume within one period
-
instantaneous volumetric flow rate
-
viscosity
-
kinematic viscosity
-
fluid density
-
normalized open valve time
-
angular velocity of Fourier modes 相似文献
6.
Thorsten Zirwes Feichi Zhang Yiqing Wang Peter Habisreuther Jordan A. Denev Zheng Chen Henning Bockhorn Dimosthenis Trimis 《Proceedings of the Combustion Institute》2021,38(2):2057-2066
Flame particles (FP) are massless, virtual particles which follow material points on the flame surface. This work presents a tracking algorithm for FPs which utilizes barycentric coordinates. The methodology can be used with any cell shape in the computational mesh and allows computationally fast spatial interpolation as well as efficient determination of the intersection of FP trajectories with iso-surfaces. In contrast to previous flame particle tracking (FPT) approaches, the code is fully parallelized and can therefore be used in-situ during the simulation. It also includes fully parallelized computation of flame consumption speed by integrating reaction rates along a line normal to the flame surface at each FP position. Direct numerical simulations of laminar pulsating premixed hydrogen–air Bunsen flames serve as validation cases and showcase the added value of tracking material points for studying local flame dynamics. Exciting the inlet flow harmonically with frequencies equal to the inverse flame time scale leads to a pulsating mode where the flame front is corrugated. Ten times higher frequencies nearly resemble the steady state solution. The FPs are seeded along the flame surface and are used to track the unsteady diffusive, convective and chemical contributions at arbitrary points on the flame front over time. Their trajectories reveal a phase shift between the unsteady flame stretch rate and local flame speed of the order of 0.1 flame time scales for rich hydrogen flames. This is caused by a time delay between straining and stretch due to curvature. The reason is that diffusive processes follow the time signal of curvature while chemical processes are most strongly affected by the straining rate, which dominates the high Lewis number hydrogen flames investigated. This time history effect may help to explain the large scattering in the correlation of local flame speed with flame stretch found in turbulent flames. 相似文献
7.
Feichi Zhang Thorsten Zirwes Thomas Häber Henning Bockhorn Dimosthenis Trimis Rainer Suntz 《Proceedings of the Combustion Institute》2021,38(2):1955-1964
Highly-resolved numerical simulations employing detailed reaction kinetics and molecular transport have been applied to flame-wall interaction (FWI) of laminar premixed flames. A multiple plane-jet flame (2D) has been considered, which is operated with premixed methane/air mixtures at atmospheric conditions and with different equivalence ratios. Free flame (FF) and side-wall quenching (SWQ) conditions have been accomplished by defining one lateral boundary as either a symmetry plane for FF or a cold wall with fixed temperature for SWQ. An equidistant grid with a resolution of 20 µm is used to resolve the FWI zone. The GRI-3.0 mechanism is used for computing chemical reaction rates. The flame is tangentially compressed when approaching the cold wall, and elongated in the FF case, causing an inversion of the sign of the tangential strain rate Kas and a considerable decrease of the total stretch rate Katot for the SWQ flame. The flame consumption speed SL decreases with decreasing normal stretch due to curvature Kac while approaching the cold wall, but it increases with decreasing Kac for the FF case, leading to an inversion of the Markstein number Matot based on Katot from positive in FF to negative in the SWQ case. The results reveal a strong correlation of flame dynamics during transitions from FWI to freely propagating flames, which may bring a new perspective for modeling FWI phenomena by means of flame dynamics. To do this, the quenching effect of the wall may be reproduced by an inversion of the Markstein number from positive to negative in the FWI zone and applying the general linear Markstein correlation, leading to a decrease of the flame consumption speed. In addition, the quenching distance evaluated from SL has been found to be almost equal to the unstretched laminar flame thickness, which compares quantitatively well with measured data from literature. 相似文献
8.
本文对甲烷预混气在多孔介质中的火焰传播特性进行了实验研究,在开口竖直管中充填多孔介质,通过改变预混气氧含量使火焰在不同多孔介质中传播并测量火焰传播速度。预混气中氧含量最高达到29%。实验结果表明:多孔介质中甲烷可燃预混气火焰传播速度大于其层流火焰传播速度,可达到5倍以上(当量比的甲烷-空气预混气);多孔介质当量孔直径越大,或预混气层流火焰速度越高,则预混气火焰传播速度越高;多孔介质中可燃混气的火焰传播界限变小,当量孔直径大的多孔介质其界限值较大。实验结果与Babkin提出的多孔介质中的火焰传播机理相符。 相似文献
9.
10.
Prabal Talukdar D. Trimis 《Journal of Quantitative Spectroscopy & Radiative Transfer》2004,84(4):527-537
This paper deals with the heat transfer analysis of a 2-D rectangular porous radiant burner. Combustion in the porous medium is modelled as a spatially dependent heat generation zone. The gas and the solid phases are considered in non-local thermal equilibrium, and separate energy equations are used for the two phases. The solid phase is assumed to be absorbing, emitting and scattering, while the gas phase is considered transparent to radiation. The radiative part of the energy equation is solved using the collapsed dimension method. The alternating direction implicit scheme is used to solve the transient 2-D energy equations. Effects of various parameters on the performance of the burner are studied. 相似文献