The Experts below are selected from a list of 294 Experts worldwide ranked by ideXlab platform
Tianfeng Lu - 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 iii reaction kinetic model of jp10
Combustion and Flame, 2018Co-Authors: Rui Xu, Tianfeng Lu, Ashkan Movaghar, Fokion N. Egolfopoulos, Kun Wang, Jiankun Shao, Sarah Johnson, Ji Woong Park, Kenneth Brezinsky, David F DavidsonAbstract:Abstract The Hybrid Chemistry (HyChem) approach has been proposed previously for combustion Chemistry modeling of real, liquid Fuels of a distillate origin. In this work, the applicability of the HyChem approach is tested for single-component Fuels using JP10 as the model Fuel. The method remains the same: an experimentally constrained, lumped single-Fuel model describing the kinetics of Fuel pyrolysis is combined with a detailed foundational Fuel Chemistry model. Due to the multi-ring molecular structure of JP10, the pyrolysis products were found to be somewhat different from those of conventional jet Fuels. The lumped reactions were therefore modified to accommodate the Fuel-specific pyrolysis products. The resulting model shows generally good agreement with experimental data, which suggests that the HyChem approach is also applicable for developing combustion reaction kinetic models for single-component Fuels.
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Multi-dimensional CFD Simulations of Knocking Combustion in a CFR Engine
Journal of Energy Resources Technology-transactions of The Asme, 2018Co-Authors: Yunchao Wu, Tianfeng Lu, Alexandra Le MoineAbstract:A numerical approach was developed based on multidimensional computational fluid dynamics (CFD) to predict knocking combustion in a cooperative Fuel research (CFR) engine. G-equation model was employed to track the turbulent flame front and a multizone model was used to capture auto-ignition in the end-gas. Furthermore, a novel methodology was developed wherein a lookup table generated from a chemical kinetic mechanism could be employed to provide laminar flame speed as an input to the G-equation model, instead of using empirical correlations. To account for Fuel Chemistry effects accurately and lower the computational cost, a compact 121-species primary reference Fuel (PRF) skeletal mechanism was developed from a detailed gasoline surrogate mechanism using the directed relation graph (DRG) assisted sensitivity analysis (DRGASA) reduction technique. Extensive validation of the skeletal mechanism was performed against experimental data available from the literature on both homogeneous ignition delay and laminar flame speed. The skeletal mechanism was used to generate lookup tables for laminar flame speed as a function of pressure, temperature, and equivalence ratio. The numerical model incorporating the skeletal mechanism was employed to perform simulations under research octane number (RON) and motor octane number (MON) conditions for two different PRFs. Parametric tests were conducted at different compression ratios (CR) and the predicted values of critical CR, delineating the boundary between “no knock” and “knock,” were found to be in good agreement with available experimental data. The virtual CFR engine model was, therefore, demonstrated to be capable of adequately capturing the sensitivity of knock propensity to Fuel Chemistry.
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toward accommodating realistic Fuel Chemistry in large scale computations
Progress in Energy and Combustion Science, 2009Co-Authors: Tianfeng LuAbstract:The need and prospect of incorporating realistic Fuel Chemistry in large-scale simulations of combustion phenomena and combustor performance are reviewed. The review first demonstrates the intricacies of chemical kinetics in homogeneous and diffusive systems, and emphasizes the essential importance of the comprehensiveness of chemical fidelity for mechanisms at the detailed and reduced levels. A systematic approach towards developing detailed reaction mechanisms is then outlined, followed by an extensive discussion on the development of reduced mechanisms and the associated strategies towards facilitated computation. Topics covered include skeletal reduction especially through directed relation graph; time-scale reduction based on the concepts of quasi-steady species enabled through computational singular perturbation; the lumping of isomers and of species with similar diffusivities; on-the-fly stiffness removal; the relative merits of implicit versus explicit solvers; and computation cost minimization achieved through tabulation and the judicious re-sequencing of the computational steps in arithmetic evaluations. Examples are given for laminar flames and direct numerical simulations of turbulent combustion to demonstrate the utility of the integrated strategy and the component methods in incorporating realistic Chemistry of practical Fuels in large-scale simulations, recognizing that the detailed mechanisms of these Fuels may consist of hundreds to thousands of species and thousands to tens of thousands of reactions. Directions for further research are suggested.
Hai Wang - One of the best experts on this subject based on the ideXlab platform.
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Joint probability distribution of Arrhenius parameters in reaction model optimization and uncertainty minimization
Proceedings of the Combustion Institute, 2018Co-Authors: Hai WangAbstract:Abstract The method of uncertainty minimization by polynomial chaos expansions is extended to Arrhenius prefactor and activation energy co-optimization and uncertainty minimization. A covariance matrix is formulated to describe the joint probability distribution of the reaction rate parameters. The method is tested on a recently proposed foundational Fuel Chemistry model using 60 H2 and H2/CO flame speeds as the targets. The results show that co-optimizing A and Ea did not produce appreciable improvements in the ability of the reaction model to better predict the flame targets. It does yield reduction in the temperature-dependent uncertainty band of the rate coefficients of several key reactions. The importance of additional experimental and theoretical studies needed for the CO+OH→CO2+H, HO2+H→H2+O2 and HO2+H→2OH reactions is highlighted.
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including real Fuel Chemistry in les of turbulent spray combustion
Combustion and Flame, 2018Co-Authors: Anne Felden, Lucas Esclapez, Eleonore Riber, Benedicte Cuenot, Hai WangAbstract:Abstract Large Eddy Simulation (LES) is progressively becoming a crucial design tool for the next generation of aeronautical combustion chambers. However, further improvements of the predictive capability of LES is required especially for predictions of pollutant formation. In general, the exact description of real Fuel combustion requires to take into account thousands of unique chemical species involved in complex and highly non-linear chemical reaction mechanisms, and the direct integration of such Chemistry in LES is not a viable path because of excessive computational demands and numerical stiffness. Modeling of real aeronautical transportation Fuel is further complicated by the fact that kerosenes are complex blends of a large number of hydrocarbon compounds and their exact composition is very difficult to determine. In this work, we propose a new framework relying upon the Hybrid Chemistry (HyChem) approach and Analytically Reduced Chemistry (ARC) to allow a direct integration of real Fuel Chemistry in the compressible LES solver AVBP. The HyChem-ARC model is coupled with the Dynamically Thickened Flame LES model (DTFLES) and a Lagrangian description of the spray to investigate the turbulent two-phase flow flame in a lean direct injection combustor, Fueled with Jet-A. The LES results are compared to experimental data in terms of gas velocity, temperature and species (CO2, H2O, CO, NO) mass fractions. It is found that the proposed methodology leads to very satisfying predictions of both the flow dynamics and the NOx levels. Additionally, the refined level of Chemistry description enables to gain valuable insights into flame/spray interactions as well as on the NOx formation mechanism in such complex flame configurations. To improve further the results, a more detailed experimental characterization of the liquid Fuel injection should be provided.
Ethan Eagle - One of the best experts on this subject based on the ideXlab platform.
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RCCI Combustion Regime Transitions in a Single-Cylinder Optical Engine and a Multi-Cylinder Metal Engine
SAE International Journal of Engines, 2017Co-Authors: Gregory Roberts, Martin Wissink, Christine Mounaim Rousselle, M. Musculus, Scott Curran, Ethan EagleAbstract:Engine experiments were conducted on a heavy-duty single-cylinder engine to explore the effects of charge preparation, Fuel stratification, and premixed Fuel Chemistry on the performance and emissions of Reactivity Controlled Compression Ignition (RCCI) combustion. The experiments were conducted at a fixed total Fuel energy and engine speed, and charge preparation was varied by adjusting the global equivalence ratio between 0.28 and 0.35 at intake temperatures of 40oC and 60oC. With a premixed injection of isooctane (PRF100), and a single direct-injection of n-heptane (PRF0), Fuel stratification was varied with start of injection (SOI) timing, and injection pressure. Combustion phasing advanced as SOI was retarded between -140o and -35o, then retarded as injection timing was further retarded, indicating a potential shift in combustion regime. Peak gross efficiency was achieved between -60o and -45o SOI, and NOx emissions increased as SOI was retarded beyond -40o, peaking around -25o SOI. Optimal cases in terms of both gross efficiency and peak pressure rise rate (PPRR) were in the mid-range SOI timings centered about -50o SOI, while late SOI resulted in decreased gross efficiency, decreased combustion efficiency, and high NOx. To assess the effect of the premixed Fuel Chemistry on RCCI combustion, a representative reformed Fuel referred to as syngas (50% H2, 50% CO by volume), and methane were substituted for PRF100. A reference baseline PRF condition with an SOI timing of -50o at Tin = 40oC and ϕ = 0.30 was used for comparison purposes. Matching combustion phasing to the baseline case by adjusting the premixed percent or SOI timing resulted in reduced gross efficiency (ηg) and increased NOx emissions for both the syngas and methane cases. Matching the bulk heat release rate (HRR) characteristics by fixing the DI SOI quantity and duration and adding a premixed injection of n-heptane was able to regain most of the lost efficiency while decreasing NOx emissions close to the baseline level.
Markus Kraft - One of the best experts on this subject based on the ideXlab platform.
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an enhanced primary reference Fuel mechanism considering conventional Fuel Chemistry in engine simulation
Journal of Engineering for Gas Turbines and Power-transactions of The Asme, 2016Co-Authors: Dezhi Zhou, Hui An, Wenming Yang, Jing Li, Markus KraftAbstract:A compact and accurate primary reference Fuel (PRF) mechanism which consists of 46 species and 144 reactions was developed and validated to consider the Fuel Chemistry in combustion simulation based on a homogeneous charged compression ignition (HCCI) mechanism. Some significant reactions were updated to ensure its capabilities for predicting combustion characteristics of PRFs. To better predict the laminar flame speed, the relevant C2–C3 carbon reactions were coupled in. This enhanced PRF mechanism was validated by available experimental data references including ignition delay times, laminar flame speed, premixed flame species concentrations in jet stirred reactor (JSR), rapid compression machine (RCM), and shock tube. The predicted data was calculated by chemkin-ii codes. All the comparisons between experimental and calculated data indicated high accuracy of this mechanism to capture combustion characteristics. Also, this mechanism was integrated into kiva4–chemkin. The engine simulation data (including in-cylinder pressure and apparent heat release rate (HRR)) was compared with experimental data in PRF HCCI, partially premixed compression ignition (PCCI), and diesel/gasoline dual-Fuel engine combustion data. The comparison results implied that this mechanism could predict PRF and gasoline/diesel combustion in computational fluid dynamic (CFD) engine simulations. The overall results show this PRF mechanism could predict the conventional Fuel combustion characteristics in engine simulation.
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An Enhanced Primary Reference Fuel Mechanism Considering Conventional Fuel Chemistry in Engine Simulation
Journal of Engineering for Gas Turbines and Power, 2016Co-Authors: Dezhi Zhou, Hui An, Wenming Yang, Jing Li, Markus KraftAbstract:Copyright © 2015 by ASME. A compact and accurate primary reference Fuel (PRF) mechanism which consists of 46 species and 144 reactions was developed and validated to consider the Fuel Chemistry in combustion simulation based on a homogenous charged compression ignition (HCCI) mechanism. Some significant reactions were updated to ensure its capabilities for predicting combustion characteristics of PRF Fuels. To better predict laminar flame speed, the relevant C2-C3 carbon reactions was coupled in. This enhanced PRF mechanism was validated by available experimental data references including ignition delay times, laminar flame speed, premixed flame species concentrations in jet stirred reactor (JSR), rapid compression machine and shock tube. The predicted data was calculated by CHEMKIN-II codes. All the comparisons between experimental and calculated data indicated high accuracy of this mechanism to capture combustion characteristics. Also, this mechanism was integrated into KIVA4-CHEMKIN. The engine simulation data (including in-cylinder pressure and apparent heat release rate (HRR)) was compared with experimental data in PRF HCCI, partially premixed compression ignition (PCCI) and diesel/gasoline dual-Fuel engine combustion data. The comparison results implied that this mechanism could predict PRF and gasoline/diesel combustion in CFD engine simulations. The overall results show this PRF mechanism could predict the conventional Fuel combustion characteristics in engine simulation.
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AN ENHANCED PRF MECHANISM CONSIDERING CONVENTIONAL Fuel Chemistry IN ENGINE SIMULATION
Journal of Engineering for Gas Turbines and Power-transactions of The Asme, 2015Co-Authors: Dezhi Zhou, Hui An, Wenming Yang, Jing Li, Markus KraftAbstract:A compact and accurate primary reference Fuel (PRF) mechanism which consists of 46 species and 144 reactions was developed and validated to consider the Fuel Chemistry in combustion simulation based on a homogenous charged compression ignition (HCCI) mechanism. Some significant reactions were updated to ensure its capabilities for predicting combustion characteristics of PRF Fuels. To better predict laminar flame speed, the relevant C2-C3 carbon reactions was coupled in. This enhanced PRF mechanism was validated by available experimental data references including ignition delay times, laminar flame speed, premixed flame species concentrations in jet stirred reactor (JSR), rapid compression machine and shock tube. The predicted data was calculated by CHEMKIN-II codes. All the comparisons between experimental and calculated data indicated high accuracy of this mechanism to capture combustion characteristics. Also, this mechanism was integrated into KIVA4-CHEMKIN. The engine simulation data (including in-cylinder pressure and apparent heat release rate (HRR)) was compared with experimental data in PRF HCCI, partially premixed compression ignition (PCCI) and diesel/gasoline dual-Fuel engine combustion data. The comparison results implied that this mechanism could predict PRF and gasoline/diesel combustion in CFD engine simulations. The overall results show this PRF mechanism could predict the conventional Fuel combustion characteristics in engine simulation.Copyright © 2015 by ASME
Anne Felden - One of the best experts on this subject based on the ideXlab platform.
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including real Fuel Chemistry in les of turbulent spray combustion
Combustion and Flame, 2018Co-Authors: Anne Felden, Lucas Esclapez, Eleonore Riber, Benedicte Cuenot, Hai WangAbstract:Abstract Large Eddy Simulation (LES) is progressively becoming a crucial design tool for the next generation of aeronautical combustion chambers. However, further improvements of the predictive capability of LES is required especially for predictions of pollutant formation. In general, the exact description of real Fuel combustion requires to take into account thousands of unique chemical species involved in complex and highly non-linear chemical reaction mechanisms, and the direct integration of such Chemistry in LES is not a viable path because of excessive computational demands and numerical stiffness. Modeling of real aeronautical transportation Fuel is further complicated by the fact that kerosenes are complex blends of a large number of hydrocarbon compounds and their exact composition is very difficult to determine. In this work, we propose a new framework relying upon the Hybrid Chemistry (HyChem) approach and Analytically Reduced Chemistry (ARC) to allow a direct integration of real Fuel Chemistry in the compressible LES solver AVBP. The HyChem-ARC model is coupled with the Dynamically Thickened Flame LES model (DTFLES) and a Lagrangian description of the spray to investigate the turbulent two-phase flow flame in a lean direct injection combustor, Fueled with Jet-A. The LES results are compared to experimental data in terms of gas velocity, temperature and species (CO2, H2O, CO, NO) mass fractions. It is found that the proposed methodology leads to very satisfying predictions of both the flow dynamics and the NOx levels. Additionally, the refined level of Chemistry description enables to gain valuable insights into flame/spray interactions as well as on the NOx formation mechanism in such complex flame configurations. To improve further the results, a more detailed experimental characterization of the liquid Fuel injection should be provided.
