Thermochemical Data for Combustion Calculations

Burcat, Alexander

doi:10.1007/978-1-4684-0186-8_8

Cited by 119 publications

(65 citation statements)

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“…We consider a total of 176 uncertain parameters, 153 of which are A factors for the forward reaction rates of each elementary reaction, and 23 are enthalpies of formation ( H f ), which are calculated using NASA polynomials [13]. The reaction rates are expressed in standard Arrhenius form using units of cm 3 mol −1 s −1 for second-order rate constants.…”

Section: Premixed Methane Flame Modelmentioning

confidence: 99%

A global sensitivity study of sulfur chemistry in a premixed methane flame model using HDMR

Ziehn

Tomlin

2008

Int J of Chemical Kinetics

112

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The use of complex mechanisms is increasing within models describing a range of important chemical processes, including combustion. Parameters describing chemical reaction rates and thermodynamics can often be very uncertain. Highlighting the main parameters contributing to predictive uncertainty is an important part of model development. However, due to the computational cost of the models and their nonlinearity, traditional methods for sensitivity analysis are often not suitable. The high-dimensional model representation (HDMR) method was developed to express the input-output relationship of a complex model with a high-dimensional input space. A fully functional surrogate model can be constructed with low computational effort. First-and second-order sensitivity indices can then be calculated in an automatic way, over large input parameter ranges. These provide an importance ranking for the input parameters. An extension to the existing set of HDMR tools is developed in this work, where the number of HMDR component functions can be reduced to explore large dimensional input spaces very efficiently. The HDMR tools are demonstrated for a case study of a one-dimensional low-pressure premixed methane flame model doped with trace sulfur and nitrogen species. Uncertainties in rate constants and thermodynamic data are considered, leading to a study of 176 input parameters. Using the new HDMR tools, the use of screening methods such as the Morris method, which aim to identify unimportant parameters beforehand, can generally be avoided. However, in certain cases, a combination of a screening method and HDMR is computationally more efficient than using HDMR alone. The final ranking of important parameters is shown to be critically dependent on the uncertainty ranges chosen due to the nonlinearity of the model. The study demonstrates that the proposed HDMR method provides a powerful tool for general application to global sensitivity analysis of complex chemical mechanisms.

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Section: Premixed Methane Flame Modelmentioning

confidence: 99%

A global sensitivity study of sulfur chemistry in a premixed methane flame model using HDMR

Ziehn

Tomlin

2008

Int J of Chemical Kinetics

112

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“…The algorithm used to compute them is based on Chapman-Enskog collision theory, Lennard-Jones potentials, and the Wilke semiempirical formulae. The enthalpy and specific heat for each species are calculated using the polynomial curve fits compiled by Burcat [19]. The secondary diffusion effects and thermal radiation are neglected in the present study.…”

Section: Mathematical Modelmentioning

confidence: 99%

Structure of Unsteady Partially Premixed Flames and the Existence of State Relationships

Aggarwal

2009

International Journal of Spray and Combustion Dynamics

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In this study, we examine the structure and existence of state relationships in unsteady partially premixed flames (PPFs) subjected to buoyancy-induced and external perturbations. A detailed numerical model is employed to simulate the steady and unsteady two-dimensional PPFs established using a slot burner under normal and zero-gravity conditions. The coflow velocity is parametrically varied. The methane-air chemistry is modeled using a fairly detailed mechanism that contains 81 elementary reactions and 24 species. Validation of the computational model is provided through comparisons of predictions with nonintrusive measurements. The combustion proceeds in two reaction zones, one a rich premixed zone and the other a nonpremixed zone. These reaction zones are spatially separated, but involve strong interactions between them due to thermochemistry and scalar transport. The fuel is mostly consumed in the premixed zone to produce CO and H 2 , which are transported to and consumed in the nonpremixed zone. The nonpremixed zone in turn provides heat and H-atoms to the premixed zone. For the range of conditions investigated, the zero-g partially premixed flames exhibit a stable behavior and a remarkably strong resistance to perturbations. In contrast, the corresponding normal-gravity flames exhibit oscillatory behavior at low coflow velocities but a stable behavior at high coflow velocities, and the behavior can be explained in terms of a global and convective instabilities. The effects of coflow and gravity on the flames are characterized through a parameter V R , defined as the ratio of coflow velocity to jet velocity. For V R ≤ 1 (low coflow velocity regime), the structures of both 0-and 1-g flames are strongly sensitive to changes in V R , while they are only mildly affected by coflow in the high coflow velocity regime (V R > 1). In addition, the spatio-temporal characteristics of the 0-and 1-g flames are markedly different in the first regime, but are essentially similar in the second regime. A more significant difference in the first regime between these flames is the presence of a flow instability that manifests itself through the self-excited oscillations of the 1-g flame and the concomitant flickering of the nonpremixed reaction zone. For V R ≤ 1, as the coflow velocity is increased, the oscillation amplitude decreases and the oscillation frequency increases, both of which are in accord with previous experimental and International journal of spray and combustion dynamics · Volume . 1 · Number . 3 . 2009 -pages 339-364 339 1 email: ska@uic.edu computational results concerning 1-g jet diffusion flames. The modified conserved scalar approach is found to be effective in characterizing the flame structure and developing state relationships for both steady and unsteady partially premixed flames. This is demonstrated by the fact that the temperature as well as the major and minor species profiles follow similar state relationships in terms of the modified mixture fraction for the 0-and 1-g flames, even though ...

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“…Assuming that the minimum and maximum values of rate parameters correspond to 3σ deviations from the recommended values on a logarithmic scale [19], the uncertainty factor can be converted [4] to the variance of the logarithm of the rate coefficient using the equation σ 2 (ln k j ) = ((f j ln 10)/3) 2 . Thermodynamic data compilations of gas kinetic modeling relevance [20][21][22][23][24][25][26][27][28][29][30][31] contain not only the enthalpy of formation of the species but also frequently quote their uncertainty. This uncertainty corresponds to 2σ .…”

Section: Uncertainty Analysismentioning

confidence: 99%

“…In this work, the same uncertainty factors were used to the kinetic and thermodynamic parameters of N-atom-free reactions and species, respectively, as in our former articles [4,7]. As a first step in the extension of these studies to NO x systems, uncertainties had to be assigned to the enthalpies of formation of all N-containing species by processing thermodynamic data collections [12,[14][15][16][17][20][21][22][23][24][25][26][27][28][29]. In most cases, the variances recommended in the databases were in agreement.…”

Section: No Formation In Combustion Systemsmentioning

confidence: 99%

Uncertainty analysis of NO production during methane combustion

Zsély

Zádor

Turányi

2008

Int J of Chemical Kinetics

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Local and Monte Carlo uncertainty analyses of NO production during methane combustion were carried out, investigating the effect of uncertainties of kinetic parameters and enthalpies of formation. In Case I, the original Leeds methane oxidation mechanism with the NO x reaction block was used, but the enthalpies of formation of all species were updated. In Case II, the NCN-containing reactions of the prompt NO formation route were added and the rate parameters of several reactions were also updated. The NO production was examined at the conditions of the Bartok et al. experiments (PSR, T = 1565-1989 K, ϕ = 0.8-1.2, residence time 3 ms). The Monte Carlo analysis provided the approximate probability density function and the variance of the calculated NO concentration, and also its attainable minimum and maximum values. Both mechanisms provided similarly good to acceptable agreement with the experimental results for lean and stoichiometric mixtures, whereas only mechanism Case II could reproduce the experimental data for rich mixtures after a realistic tuning of the parameters. Local uncertainty analysis was used to assess the contribution of the uncertainty of each parameter to the uncertainty of the calculated NO concentration. Enthalpies of formation of NNH and HCCO, and rate parameters of 20 reaction steps cause most of the uncertainty of the calculated NO concentrations at all conditions. The relative importance of the four main NO formation routes was investigated via the inspection of the reaction rates, embedded in the Monte Carlo analysis. NO formation in rich mixtures was dominated by the prompt route, whereas in leaner mixtures the share of the NO formation routes depended very much on the values of rate parameters, when varied within the uncertainty limits of kinetic data evaluations.

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Thermochemical Data for Combustion Calculations

Cited by 119 publications

References 50 publications

A global sensitivity study of sulfur chemistry in a premixed methane flame model using HDMR

A global sensitivity study of sulfur chemistry in a premixed methane flame model using HDMR

Structure of Unsteady Partially Premixed Flames and the Existence of State Relationships

Uncertainty analysis of NO production during methane combustion

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