Skeletal Kinetic Modeling for the Combustion of Endothermic Hydrocarbon Fuel in Hypersonic Vehicle

2021 ◽  
pp. 1-24
Author(s):  
Hui-Sheng Peng ◽  
Bei-Jing Zhong
Keyword(s):  
Surrogate Model ◽  
Laminar Flame ◽  
Combustion Process ◽  
Hydrocarbon Fuel ◽  
Kinetic Mechanism ◽  
Chemical Kinetic ◽  
Vital Role ◽  
Reacting Flow ◽  
Combustion Properties ◽  
Endothermic Hydrocarbon Fuel

Abstract Chemical kinetic mechanism plays a vital role in the deep learning of reacting flow in practical combustors, which can help obtain many details of the combustion process. In this paper, a surrogate model and a skeletal mechanism for an endothermic hydrocarbon fuel were developed for further investigations of the combustion performance in hypersonic vehicles: (1) The surrogate model consists of 81.3 mol% decalin and 18.7 mol% n-dodecane, which were determined by both the composition distributions and key properties of the target endothermic hydrocarbon fuel. (2) A skeletal kinetic mechanism only containing 56 species and 283 reactions was developed by the method of “core mechanism​ sub mechanism”. This mechanism can be conveniently applied to the simulation of practical combustors for its affordable scale. (3) Accuracies of the surrogate model and the mechanism were systematically validated by the various properties of the target fuel under pressures of 1-20atm, temperatures of 400-1250K, and equivalence ratios of 0.5-1.5. The overall errors for the ignition and combustion properties are no more than 0.4 and 0.1, respectively. (4) Laminar flame speeds of the target fuel and the surrogate model fuel were also measured for the validations. Results show that both the surrogate model and the mechanism can well predict the properties of the target fuel. The mechanism developed in this work is valuable to the further design and optimization of the propulsion systems.

Chemical Reactor Network Application to Emissions Prediction for Industial DLE Gas Turbine

2006 ◽  
Author(s):  
I. V. Novosselov ◽  
P. C. Malte ◽  
S. Yuan ◽  
R. Srinivasan ◽  
J. C. Y. Lee
Keyword(s):  
Gas Turbine ◽  
Chemical Reactor ◽  
Kinetic Mechanism ◽  
Chemical Kinetic ◽  
Operating Conditions ◽  
Reacting Flow ◽  
Ongoing Research ◽  
Chemical Reactor Network ◽  
Reaction Zones ◽  
Reactor Network

A chemical reactor network (CRN) is developed and applied to a dry low emissions (DLE) industrial gas turbine combustor with the purpose of predicting exhaust emissions. The development of the CRN model is guided by reacting flow computational fluid dynamics (CFD) using the University of Washington (UW) eight-step global mechanism. The network consists of 31 chemical reactor elements representing the different flow and reaction zones of the combustor. The CRN is exercised for full load operating conditions with variable pilot flows ranging from 35% to 200% of the neutral pilot. The NOpilot. The NOx and the CO emissions are predicted using the full GRI 3.0 chemical kinetic mechanism in the CRN. The CRN results closely match the actual engine test rig emissions output. Additional work is ongoing and the results from this ongoing research will be presented in future publications.

scholarly journals Impact of Boundary Condition and Kinetic Parameter Uncertainties on NOx Predictions in Methane-Air Stagnation Flame Experiments

2021 ◽  
Author(s):  
Antoine Durocher ◽  
Jiayi Wang ◽  
Gilles Bourque ◽  
Jeffrey M. Bergthorson
Keyword(s):  
Boundary Conditions ◽  
High Pressures ◽  
Laminar Flame ◽  
Combustion Process ◽  
Industrial Applications ◽  
Parameter Uncertainties ◽  
Nox Formation ◽  
Important Species ◽  
Spectral Expansions ◽  
Combustion Properties

Abstract A comprehensive understanding of uncertainty sources in experimental measurements is required to develop robust thermochemical models for use in industrial applications. Due to the complexity of the combustion process in gas turbine engines, simpler flames are generally used to study fundamental combustion properties and measure concentrations of important species to validate and improve modelling. Stable, laminar flames have increasingly been used to study nitrogen oxide (NOx) formation in lean-to-rich compositions in low-to-high pressures to assess model predictions and improve accuracy to help develop future low-emissions systems. They allow for non-intrusive diagnostics to measure sub-ppm concentrations of pollutant molecules, as well as important precursors, and provide well-defined boundary conditions to directly compare experiments with simulations. The uncertainties of experimentally-measured boundary conditions and the inherent kinetic uncertainties in the nitrogen chemistry are propagated through one-dimensional stagnation flame simulations to quantify the relative importance of the two sources and estimate their impact on predictions. Measurements in lean, stoichiometric, and rich methane-air flames are used to investigate the production pathways active in those conditions. Various spectral expansions are used to develop surrogate models with different levels of accuracy to perform the uncertainty analysis for 15 important reactions in the nitrogen chemistry and the 6 boundary conditions (ϕ, Tin, uin, du/dzin, Tsurf, P) simultaneously. After estimating the individual parametric contributions, the uncertainty of the boundary conditions are shown to have a relatively small impact on the prediction of NOx compared to kinetic uncertainties in these laboratory experiments. These results show that properly calibrated laminar flame experiments can, not only provide validation targets for modelling, but also accurate indirect measurements that can later be used to infer individual kinetic rates to improve thermochemical models.

Validated F-T Fuel Surrogate Model for Simulation of Jet-Engine Combustion

2010 ◽  
Author(s):  
Chitralkumar V. Naik ◽  
Karthik V. Puduppakkam ◽  
Abhijit Modak ◽  
Cheng Wang ◽  
Ellen Meeks
Keyword(s):  
Laminar Flame ◽  
Laboratory Data ◽  
Kinetic Mechanism ◽  
Chemical Kinetic ◽  
Reduction Techniques ◽  
Auto Ignition ◽  
Wide Range ◽  
Fuel Behavior ◽  
Detailed Kinetics ◽  
Surrogate Fuel

Validated surrogate models have been developed for two Fisher-Tropsch (F-T) fuels. The models started with a systematic approach to determine an appropriate surrogate fuel composition specifically tailored for the two alternative jet-fuel samples. A detailed chemical kinetic mechanism has been assembled for these model surrogates starting from literature sources, and then improved to ensure self-consistency of the kinetics and thermodynamic data. This mechanism has been tested against fundamental laboratory data on auto-ignition times, laminar flame-speeds, extinction strain rates, and NOx emissions. Literature data used to validate the mechanism include both the individual surrogate-fuel components and actual F-T fuel samples where available. As part of the validation, simulations were performed for a wide variety of experimental configurations, as well as a wide range of temperatures and equivalence ratios for fuel/air mixtures. Comparison of predicted surrogate-fuel behavior against data on real F-T fuel behavior also show the effectiveness of the surrogate-matching approach and the accuracy of the detailed-kinetics mechanisms. The resulting validated mechanism has been also reduced through application of automated mechanism reduction techniques to provide progressively smaller mechanisms, with different degrees of accuracy, that are reasonable for use in CFD simulations employing detailed kinetics.

Numerical study on the combustion characteristics in a porous-free flame burner for lean mixtures

2019 ◽  
Vol 234 (4) ◽  
pp. 935-945 ◽  
Author(s):  
Seyed Amin Ghorashi ◽  
Seyed Mohammad Hashemi ◽  
Seyed Abdolmehdi Hashemi ◽  
Mahdi Mollamahdi
Keyword(s):  
Porous Medium ◽  
Numerical Study ◽  
Combustion Process ◽  
Experimental Tests ◽  
Kinetic Mechanism ◽  
Chemical Kinetic ◽  
Numerical Results ◽  
Flame Stability ◽  
Porous Burner ◽  
Flame Burner

The present work implements a numerical simulation to investigate the combustion process in a porous-free flame burner. The non-equilibrium thermal condition is performed, and discretization and solving of the governing equations are conducted in a two-dimensional axisymmetric model. In order to simulate the combustion process, a reduced chemical kinetic mechanism of GRI 3.0, which includes 16 species and 41 reactions, is used. In order to prove the precision of the numerical method, some experimental tests are carried out and the numerical results are in a good agreement with the experimental measurements. The numerical results demonstrate that the porous-free flame burner has a higher flame stability compared to the conventional porous burner and the radiative efficiency of the porous-free flame burner is less than the porous burner. In addition, an increase in thermal conduction of the porous medium leads to an extension in the flame stability. In addition, the results show that with decreasing the pore density of porous medium, the flame stability is extended.

An Investigation of Combustion Properties of Butanol and its Potential for Power Generation

2017 ◽  
Author(s):  
Torsten Methling ◽  
Sandra Richter ◽  
Trupti Kathrotia ◽  
Marina Braun-Unkhoff ◽  
Clemens Naumann ◽  
...  
Keyword(s):  
Ignition Delay ◽  
Laminar Flame ◽  
Cone Angle ◽  
Transformation Method ◽  
Chemical Kinetic ◽  
Reaction Model ◽  
Ignition Delay Times ◽  
Combustion Properties ◽  
Delay Times ◽  
Reaction Models

Over the last years, global concerns about energy security and climate change have resulted in many efforts focusing on the potential utilization of non-petroleum-based, i.e. bio-derived, fuels. In this context, n-butanol has recently received high attention because it can be produced sustainably. A comprehensive knowledge about its combustion properties is inevitable to ensure an efficient and smart use of n-butanol if selected as a future energy carrier. In the present work, two major combustion characteristics, here laminar flame speeds applying the cone-angle method and ignition delay times applying the shock tube technique, have been studied, experimentally and by modeling exploiting detailed chemical kinetic reaction models, at ambient and elevated pressures. The in-house reaction model was constructed applying the RMG-method. A linear transformation method recently developed, linTM, was exploited to generate a reduced reaction model needed for an efficient, comprehensive parametric study of the combustion behavior of n-butanol/hydrocarbon mixtures. All experimental data were found to agree with the model predictions of the in-house reaction model, for all temperatures, pressures, and fuel-air ratios. On the other hand, calculations using reaction models from the open literature mostly overpredict the measured ignition delay times by about a factor of two. The results are compared to those of ethanol, with ignition delay times very similar and laminar flame speeds of n-butanol slightly lower, at atmospheric pressure.

A Detailed and Reduced Reaction Mechanism of Biomass-Based Syngas Fuels

2010 ◽  
Vol 132 (9) ◽  
Author(s):  
Marina Braun-Unkhoff ◽  
Nadezhda Slavinskaya ◽  
Manfred Aigner
Keyword(s):  
Reaction Mechanism ◽  
Laminar Flame ◽  
Chemical Kinetic ◽  
Laminar Flame Speed ◽  
Predictive Capability ◽  
Kinetic Reaction ◽  
Auto Ignition ◽  
Combustion Properties ◽  
Detailed Chemical ◽  
Good Agreement

In the present work, the elaboration of a reduced kinetic reaction mechanism is described, which predicts reliably fundamental characteristic combustion properties of two biogenic gas mixtures consisting mainly of hydrogen, methane, and carbon monoxide, with small amounts of higher hydrocarbons (ethane and propane) in different proportions. From the in-house detailed chemical kinetic reaction mechanism with about 55 species and 460 reactions, a reduced kinetic reaction mechanism was constructed consisting of 27 species and 130 reactions. Their predictive capability concerning laminar flame speed (measured at T0=323 K, 373 K, and 453 K, at p=1 bar, 3 bars, and 6 bars for equivalence ratios φ between 0.6 and 2.2) and auto ignition data (measured in a shock tube between 1035 K and 1365 K at pressures around 16 bars for φ=0.5 and 1.0) are discussed in detail. Good agreement was found between experimental and calculated values within the investigated parameter range.

An Investigation of Fundamental Combustion Properties of the Oxygenated Fuels DME and OME1

2020 ◽  
Author(s):  
John M. Ngugi ◽  
Sandra Richter ◽  
Marina Braun-Unkhoff ◽  
Clemens Naumann ◽  
Uwe Riedel
Keyword(s):  
Gas Turbines ◽  
Fossil Fuels ◽  
Laminar Flame ◽  
Chemical Kinetic ◽  
Transport Sector ◽  
Renewable Energy Resources ◽  
Fuel Blend ◽  
Design And Optimization ◽  
Elevated Pressures ◽  
Combustion Properties

Abstract Demands of energy will increase worldwide. The use of alternative and renewable energy resources is an attractive option to counteract climate change connected with the burning of fossil fuels. Moreover, improvements in fuel flexibility are a pre-requisite to meet the challenge of a sustainable production of energy in the near future. Within this context, oxygenated molecules, in particular ethers are of high interest because they can be produced renewably. In addition, ethers are promising considerably reduced emissions of particles and soot. In future, ethers might play a role as an alternative fuel (blend) for power generation in gas turbines and in the transport sector. Dimethylether (DME: CH3OCH3) and oxymethylenether (OMEn: CH3O(CH2O)nCH3) are regarded as some of the most promising alternatives to fossil fuels, in particular in compression ignition engines. In this work, we report on a combined experimental and modeling study: The oxidation of mixtures of dimethylether as well as of the simplest oxymethylenether (OME1) was investigated. The focus was put on two fundamental combustion properties: (i) ignition delay times measured in a shock tube device, at ambient and elevated pressures up to 16 bar, for stoichiometric mixtures, and (ii) laminar flame speed data, at ambient and elevated pressures up to 6 bar, determined for OME1. The experimental data base was used for the validation of several detailed chemical-kinetic reaction mechanisms taken from literature. Sensitivity analysis was performed for the two selected targets to allow a better insight into the oxidation network within the envisaged wide parameter range. The findings of the present work will contribute to a better understanding of the combustion of these specific ethers, and to the design and optimization of burners and engines as well.

HEEDS Optimized HyChem Mechanisms

2017 ◽  
Author(s):  
Graham Goldin ◽  
Zhuyin Ren ◽  
Yang Gao ◽  
Tianfeng Lu ◽  
Hai Wang ◽  
...  
Keyword(s):  
High Temperature ◽  
Ignition Delay ◽  
Laminar Flame ◽  
Chemical Kinetic ◽  
Flame Speed ◽  
Cfd Simulations ◽  
Transportation Fuels ◽  
Ignition Delay Times ◽  
Combustion Properties ◽  
Fuel Pyrolysis

Transportation fuels consist of a large number of hydrocarbon components and combust through an even larger number of intermediates. Detailed chemical kinetic models of these fuels typically consist of hundreds of species, and are computationally expensive to include directly in 3D CFD simulations. HyChem (Hybrid Chemistry) is a recently proposed modeling approach for high-temperature fuel oxidation based on the assumptions that fuel pyrolysis is fast compared to the subsequent oxidation of the small fragments, and that, although their proportions may differ, all fuels pyrolyse to similar sets of these fragment species. Fuel pyrolysis is hence modeled with a small set of lumped reactions, and oxidation is described by a compact C0-4 foundation chemistry core. The stoichiometric coefficients of the global pyrolysis reactions are determined to match experimental or detailed mechanism computational data, such as shock-tube pyrolysis products, ignition delays and laminar flame speeds. The model is then validated against key combustion properties, including ignition delays, laminar flame speeds and extinction strain rates. The resulting HyChem model is relatively small and computationally tractable for 3D CFD simulations in complex geometries. This paper applies the HEEDS optimization tool to find optimal pyrolysis reaction stoichiometric coefficients for high-temperature combustion of two fuels, namely Jet-A and n-heptane, using a 47 species mechanism. It was found that optimizing on experimental ignition delay and laminar flame speed targets yield better agreement for ignition delay times and flame speeds than optimizing on pyrolysis yield targets alone. For Jet-A, good agreement for ignition delays and flame speeds were obtained by using both ignition delay and flame speeds as targets. For n-heptane, a trade-off between ignition delay and flame speed was found, where increased target weights for ignition delay resulted in worse flame speed predictions, and visa-versa.

Prediction of Premixed Laminar Flame Structure and Burning Velocity of Aviation Fuel-Air Mixtures

2001 ◽  
Author(s):  
A. G. Kyne ◽  
P. M. Patterson ◽  
M. Pourkashanian ◽  
C. W. Wilson ◽  
A. Williams
Keyword(s):  
Reaction Mechanism ◽  
Laminar Flame ◽  
Burning Velocity ◽  
Flame Structure ◽  
Kinetic Mechanism ◽  
Chemical Kinetic ◽  
Aviation Fuel ◽  
Measured Temperature ◽  
Premixed Laminar ◽  
Increasing Temperature

The structure of a rich burner stabilised kerosene/O2/N2 flame is predicted using a detailed chemical kinetic mechanism where the kerosene is represented by a mixture of n-decane and toluene. The chemical reaction mechanism, consisting of 440 reactions between 84 species, is capable of predicting the experimentally determined flame structure of Douté et al. (1995) with good success using the measured temperature profile as input. Sensitivity and reaction rate analyses are carried out to identify the most significant reactions and based on this the reaction mechanism was reduced to one with only 165 reactions without any loss of accuracy. Burning velocities of kerosene-air mixtures were also determined over an extensive range of equivalence ratios at atmospheric pressure. The initial temperature of the mixture was also varied and burning velocities were found to increase with increasing temperature. Burning velocities calculated using both the detailed and reduced mechanisms were essentially identical.

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