The Experts below are selected from a list of 13617 Experts worldwide ranked by ideXlab platform
Hai Wang - One of the best experts on this subject based on the ideXlab platform.
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a physics based approach to modeling real fuel Combustion chemistry v nox formation from a typical jet a
Combustion and Flame, 2020Co-Authors: Chiara Saggese, Rui Xu, Craig T Bowman, Jiwoong Park, Tianfeng Lu, Hai WangAbstract:Abstract Real transportation fuels are complex mixtures of a variety of Hydrocarbon components. Predicting NOx formation in practical combustors burning real fuels is usually made with the assumption that the NOx submodels developed and tested for small Hydrocarbon Combustion are applicable to mixtures of large Hydrocarbons as found in real fuels. Additionally, NOx data are scarce for flames of real fuels. The aims of the current study are (i) to provide reliable NOx data in flames of a typical jet fuel, and (ii) to test our capability to predict these data by combining a recently proposed HyChem reaction model of jet A Combustion (Xu et al., 2018) with the NOx submodel of Glarborg (2018). Specifically, NOx concentrations were measured in stretch-stabilized premixed flames of methane and Jet A (POSF10325) from fuel lean to rich conditions and of ethylene at a fuel-rich equivalence ratio. This range of stoichiometries allows both thermal NO and prompt NO pathways to be tested. The results show reasonably good agreement between the experimental data and model predictions for all flames tested, although the model appears to underpredict NOx concentrations in the Jet A flames under fuel rich conditions. Sensitivity analyses were conducted to illustrate the influence of the reaction pathways and flame boundary conditions on NOx predictions. The analyses also suggest that additional prompt NO reaction pathways may play a role in flames of large Hydrocarbons.
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Combustion kinetic modeling using multispecies time histories in shock tube oxidation of heptane
Combustion and Flame, 2011Co-Authors: David A Sheen, Hai WangAbstract:Abstract Recently, species time histories have been measured during n -heptane oxidation behind reflected shock waves [D.F. Davidson, Z. Hong, G.L. Pilla, A. Farooq, R.D. Cook, R.K. Hanson, Combust. Flame 157 (2010) 1899–1905]. The highly precise nature of these measurements is expected to impose critical constraints on chemical kinetic models of Hydrocarbon Combustion. In this paper, we apply the Method of Uncertainty Analysis using Polynomial Chaos Expansions (MUM-PCE) [D.A. Sheen, X. You, H. Wang, T. Lovas, Proc. Combust. Inst. 32 (2009) 535–542] to demonstrate how the multispecies measurement may be utilized beyond simple model validation. The results show that while an as-compiled, prior reaction model of n -alkane Combustion can be accurate in its prediction of the detailed species profiles, the kinetic parameter uncertainty in the model remains to be too large to obtain a precise prediction of the data. Constraining the prior model against the species time histories within the measurement uncertainties led to notable improvements in the precision of model predictions against the species data as well as the global Combustion properties considered. Lastly, we show that while the capability of the multispecies measurement presents a step-change in our precise knowledge of the chemical processes in Hydrocarbon Combustion, accurate data of global Combustion properties are still necessary to predict fuel Combustion.
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Weakly bound carbon-Carbon bonds in acenaphthene derivatives and hexaphenylethane
Journal of Physical Chemistry A, 2010Co-Authors: Enoch Dames, Baptiste Sirjean, Hai WangAbstract:A class of acenaphthene derivatives is shown to contain weak central carbon-carbon bonds that may be easily cleaved at high temperatures or even at ambient conditions to yield persistent free diradicals. To demonstrate the weak C-C bond strength, density functional theory calculations were carried out at several levels of theory for both the parent molecules and the diradicals resulting from the C-C bond cleavage. To assess the accuracy of the calculations, hexaphenylethane was chosen as a model compound due to its similarity with the molecules studied here, its great resonance stabilization, and long-standing history within the chemistry community. The C-C bond dissociation energy of hexaphenylethane was determined to be 11.3 +/- 1.4 kcal/mol using a combination of isodesmic reactions and calculations at the M06-2X/6-31+G(d,p) level of theory. The types of molecules presented here are proposed as strong possibilities for the natural existence of free radicals ill Young and Mature Soot formed in Hydrocarbon Combustion.
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detailed and simplified kinetic models of n dodecane oxidation the role of fuel cracking in aliphatic Hydrocarbon Combustion
Proceedings of the Combustion Institute, 2009Co-Authors: Xiaoqing You, Fokion N Egolfopoulos, Hai WangAbstract:Abstract A detailed kinetic model is proposed for the Combustion of normal alkanes up to n -dodecane above 850 K. The model was validated against experimental data, including fuel pyrolysis in plug flow and jet-stirred reactors, laminar flame speeds, and ignition delay times behind reflected shock waves, with n -dodecane being the emphasis. Analysis of the computational results reveal that for a wide range of Combustion conditions, the kinetics of fuel cracking to form smaller molecular fragments is fast and may be decoupled from the oxidation kinetics of the fragments. Subsequently, a simplified model containing a minimal set of 4 species and 20 reaction steps was developed to predict the fuel pyrolysis rate and product distribution. Combined with the base C 1 -C 4 model, the simplified model predicts fuel pyrolysis rate and product distribution, laminar flame speeds, and ignition delays as close as the detailed reaction model.
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Combustion chemistry of propane: A case study of detailed reaction mechanism optimization
Proceedings of the Combustion Institute, 2000Co-Authors: Zhiwei Qin, Scott G Davis, Vitali V. Lissianski, H. Yang, William C. Gardiner, Hai WangAbstract:Detailed chemical reaction mechanisms describing Hydrocarbon Combustion chemistry are conceptually structured in a hierarchical manner with H2 and CO chemistry at the base, supplemented as needed by elementary reactions of larger chemical species. While this structure gives a logical organization to Combustion chemistry, the degree to which this organization reflects actual reactive fluxes in flames is not known. Moreover, it has not been tested whether sets of rate parameters derived by optimizing fits to small-Hydrocarbon Combustion data are secure foundations upon which to optimize the rate parameters needed for modeling the Combustion of larger Hydrocarbons. In this work, a computer modeling study was undertaken to discover whether optimizing the rate parameters of a 258-reaction C3 Combustion chemistry mechanism that was added to a previously optimized 205-reaction C3 mechanism would provide satisfactory accounting for C3 flame speed and ignition data. The optimization was done with 21 optimization targets, 9 of which were ignition delays and 12 of which were atmospheric pressure laminar flame speeds; 2 of the ignition delays and 2 of the flame speeds, all for methane fuel, had served as optimization targets for the C3 rate parameters. It was found in sensitivity studies that the coupling between the C3 and the C3 chemistry was much stronger than anticipated. No set of C3 rate parameters could account for the C3 Combustion data as long as the previously optimized (against C3 optimization targets only) C3 rate parameters remained fixed. A reasonable match to the C3 targets could be obtained, without degrading the match between experiment and calculation for the C3 optimization targets, by reoptimizing six of the previously optimized and three additional C3 rate parameters.
Tej S Choksi - One of the best experts on this subject based on the ideXlab platform.
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insights and comparison of structure property relationships in propane and propene catalytic Combustion on pd and pt based catalysts
Journal of Catalysis, 2021Co-Authors: Anchih Yang, Verena Streibel, Tej S Choksi, Hassan Aljama, Baraa Werghi, Simon R BareAbstract:Abstract Hydrocarbon Combustion is crucial in emission control applications. Developing efficient catalysts where noble metal use is optimized is imperative in this field. Hydrocarbons with varying molecular structures provide different challenges in this process. In this work, propane and propene were chosen as model compounds to compare the active site requirements for their oxidation on Pd- and Pt-based catalysts. A library of uniform Pd/Pt catalysts prepared from colloidal nanoparticle precursors were used to study several important variables including Pd/Pt composition, support, and phase. The effects of these parameters on activity and stability in the presence of steam were carefully evaluated. Our results show that Pt-rich catalysts perform best for both reactions. However, opposite general trends in rate orders, active phase and stability after aging treatments were observed. These differences arise from the distinct rate-limiting steps and coverage between the two reactions, with propene strongly adsorbing on the noble metal surface, while propane has weaker interactions, resulting in different dominating activation steps. Experimental observations were supported by density functional theory calculations, where the activation barriers to crucial elementary steps were found to be different for the two reactions. The results point to different catalytic requirements to activate the two compounds, highlighting the need to optimize catalysts based on contrasting elements. These findings provide insights that can help engineer efficient catalysts for Hydrocarbon Combustion and optimize the use of precious noble metals.
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insights and comparison of structure property relationships in propane and propene catalytic Combustion on pd and pt based catalysts
Journal of Catalysis, 2021Co-Authors: Anchih Yang, Verena Streibel, Tej S Choksi, Hassan Aljama, Baraa Werghi, Simon R BareAbstract:Abstract Hydrocarbon Combustion is crucial in emission control applications. Developing efficient catalysts where noble metal use is optimized is imperative in the field. Hydrocarbons with varying molecular structures provide different challenges in this process. In this work, propane and propene were chosen as model compounds to compare the active site requirements for their oxidation on Pd- and Pt-based catalysts. A library of uniform Pd/Pt catalysts prepared from colloidal nanoparticle precursors were used to study several important variables including Pd/Pt composition, support, and phase. The effects of these parameters on activity and stability were carefully evaluated in the presence of steam. Our results show that Pt-rich catalysts perform best for both reactions. However, opposite general trends in rate orders, active phase and stability after aging treatments were observed. These differences arise from the distinct rate-limiting steps and coverage between the two reactions, with propene strongly adsorbing on the noble metal surface, while propane having weaker interactions, resulting in different dominating activation steps. Experimental observations were supported by DFT calculations, where the activation barriers of crucial elementary steps were found to be different for the two reactions. The results point to different catalytic requirements to activate the two compounds, thus highlighting the need for optimizing catalysts based on contrasting elements. These findings provide insights that can help engineer efficient catalysts for application in Hydrocarbon Combustion and optimize the use of precious noble metals.
Markus Kraft - One of the best experts on this subject based on the ideXlab platform.
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evolution of the soot particle size distribution along the centreline of an n heptane toluene co flow diffusion flame
Combustion and Flame, 2019Co-Authors: Jochen A H Dreyer, Maximilian Poli, Nick Eaves, Maria L Botero, Jethro Akroyd, Sebastian Mosbach, Markus KraftAbstract:Abstract A newly developed experimental set-up for studying liquid Hydrocarbon Combustion in the well-established Yale burner was used to investigate the correlation between fuel composition and its sooting propensity. Soot particle size distributions (PSDs) and flame temperatures along the centreline of an n-heptane/toluene co-flow diffusion flame are reported. The results are compared to soot temperature and volume fraction profiles obtained using colour ratio pyrometry. The addition of toluene (0, 5, 10, and 15 mol%) to heptane moved soot inception to lower heights above the burner (HAB). The earlier inception extended the soot growth zone in the toluene-laden flames, leading to larger soot primary and agglomerate particles. Toluene addition had little influence on the maximum soot number density, indicating that the observed increase in soot volume fraction can mainly be attributed to the increase in particle size. The reported PSDs inside a vapour-fed diffusion flame are the first of their kind and provide a comprehensive dataset for future studies of Combustion chemistry and soot particle models.
Jochen A H Dreyer - One of the best experts on this subject based on the ideXlab platform.
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effect of ammonia addition on suppressing soot formation in methane co flow diffusion flames
Proceedings of the Combustion Institute, 2020Co-Authors: Matthew J Montgomery, Jochen A H Dreyer, Yuan Xuan, Hyunguk Kwon, Charles S Mcenally, Lisa D PfefferleAbstract:Abstract Due to issues surrounding carbon dioxide emissions from carbon-containing fuels, there is growing interest in ammonia (NH3) as an alternative Combustion fuel. One attractive method of burning NH3 is to co-fire it with Hydrocarbons, such as natural gas, and in this case soot formation is possible. To begin understanding the influence of NH3 on soot formation when co-fired with Hydrocarbons, soot volume fractions and mole fractions of gas-phase species were computationally and experimentally interrogated for CH4 flames with up to 40% NH3 by volumetric fuel fraction. Mole fractions of gas-phase species, including C2H2 and C6H6, were measured with on-line electron impact mass spectrometry, and soot volume fractions were obtained via color-ratio pyrometry. The simulations employed a detailed chemical mechanism developed for capturing nitrogen interactions with Hydrocarbons during Combustion. The results are compared to findings in N2 CH4 flames, in order to separate thermal and dilution effects from the chemical influence of NH3 on soot formation. Experimentally, C2H2 concentrations were found to decrease slightly for the NH3 CH4 flames relative to N2 CH4 flames, and a stronger suppression of C6H6 was found for NH3 relative to N2 additions. The measured results show a strong suppression of soot with the addition of NH3, with soot concentrations reduced by over a factor of 10 with addition of up to 20% or more NH3 by mole fraction. The model satisfactorily captured relative differences in maximum centerline C2H2, C6H6, and soot concentrations with addition of N2, but was unable to match measured differences in NH3 CH4 flames. These results highlight the need for an improved understanding of fuel-nitrogen interactions with higher Hydrocarbons to enable accurate models for predicting particulate emissions from NH3/Hydrocarbon Combustion.
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evolution of the soot particle size distribution along the centreline of an n heptane toluene co flow diffusion flame
Combustion and Flame, 2019Co-Authors: Jochen A H Dreyer, Maximilian Poli, Nick Eaves, Maria L Botero, Jethro Akroyd, Sebastian Mosbach, Markus KraftAbstract:Abstract A newly developed experimental set-up for studying liquid Hydrocarbon Combustion in the well-established Yale burner was used to investigate the correlation between fuel composition and its sooting propensity. Soot particle size distributions (PSDs) and flame temperatures along the centreline of an n-heptane/toluene co-flow diffusion flame are reported. The results are compared to soot temperature and volume fraction profiles obtained using colour ratio pyrometry. The addition of toluene (0, 5, 10, and 15 mol%) to heptane moved soot inception to lower heights above the burner (HAB). The earlier inception extended the soot growth zone in the toluene-laden flames, leading to larger soot primary and agglomerate particles. Toluene addition had little influence on the maximum soot number density, indicating that the observed increase in soot volume fraction can mainly be attributed to the increase in particle size. The reported PSDs inside a vapour-fed diffusion flame are the first of their kind and provide a comprehensive dataset for future studies of Combustion chemistry and soot particle models.
Simon R Bare - One of the best experts on this subject based on the ideXlab platform.
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insights and comparison of structure property relationships in propane and propene catalytic Combustion on pd and pt based catalysts
Journal of Catalysis, 2021Co-Authors: Anchih Yang, Verena Streibel, Tej S Choksi, Hassan Aljama, Baraa Werghi, Simon R BareAbstract:Abstract Hydrocarbon Combustion is crucial in emission control applications. Developing efficient catalysts where noble metal use is optimized is imperative in this field. Hydrocarbons with varying molecular structures provide different challenges in this process. In this work, propane and propene were chosen as model compounds to compare the active site requirements for their oxidation on Pd- and Pt-based catalysts. A library of uniform Pd/Pt catalysts prepared from colloidal nanoparticle precursors were used to study several important variables including Pd/Pt composition, support, and phase. The effects of these parameters on activity and stability in the presence of steam were carefully evaluated. Our results show that Pt-rich catalysts perform best for both reactions. However, opposite general trends in rate orders, active phase and stability after aging treatments were observed. These differences arise from the distinct rate-limiting steps and coverage between the two reactions, with propene strongly adsorbing on the noble metal surface, while propane has weaker interactions, resulting in different dominating activation steps. Experimental observations were supported by density functional theory calculations, where the activation barriers to crucial elementary steps were found to be different for the two reactions. The results point to different catalytic requirements to activate the two compounds, highlighting the need to optimize catalysts based on contrasting elements. These findings provide insights that can help engineer efficient catalysts for Hydrocarbon Combustion and optimize the use of precious noble metals.
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insights and comparison of structure property relationships in propane and propene catalytic Combustion on pd and pt based catalysts
Journal of Catalysis, 2021Co-Authors: Anchih Yang, Verena Streibel, Tej S Choksi, Hassan Aljama, Baraa Werghi, Simon R BareAbstract:Abstract Hydrocarbon Combustion is crucial in emission control applications. Developing efficient catalysts where noble metal use is optimized is imperative in the field. Hydrocarbons with varying molecular structures provide different challenges in this process. In this work, propane and propene were chosen as model compounds to compare the active site requirements for their oxidation on Pd- and Pt-based catalysts. A library of uniform Pd/Pt catalysts prepared from colloidal nanoparticle precursors were used to study several important variables including Pd/Pt composition, support, and phase. The effects of these parameters on activity and stability were carefully evaluated in the presence of steam. Our results show that Pt-rich catalysts perform best for both reactions. However, opposite general trends in rate orders, active phase and stability after aging treatments were observed. These differences arise from the distinct rate-limiting steps and coverage between the two reactions, with propene strongly adsorbing on the noble metal surface, while propane having weaker interactions, resulting in different dominating activation steps. Experimental observations were supported by DFT calculations, where the activation barriers of crucial elementary steps were found to be different for the two reactions. The results point to different catalytic requirements to activate the two compounds, thus highlighting the need for optimizing catalysts based on contrasting elements. These findings provide insights that can help engineer efficient catalysts for application in Hydrocarbon Combustion and optimize the use of precious noble metals.