Modified multipurpose reduced chemistry for ethanol combustion

2020 ◽  
Vol 215 ◽  
pp. 221-223 ◽  
Author(s):  
Alejandro Millán-Merino ◽  
Eduardo Fernández-Tarrazo ◽  
Mario Sánchez-Sanz ◽  
Forman A. Williams
Keyword(s):  
Reduced Chemistry ◽  
Ethanol Combustion

scholarly journals Reduced Chemistry for Butanol Isomers at Engine-Relevant Conditions

2016 ◽  
Vol 31 (1) ◽  
pp. 867-881 ◽  
Author(s):  
Xin Hui ◽  
Kyle E. Niemeyer ◽  
Kyle B. Brady ◽  
Chih-Jen Sung
Keyword(s):  
Reduced Chemistry

scholarly journals Influence of the diesel pilot injector configuration on ethanol combustion and performance of a heavy-duty direct injection engine

2021 ◽  
pp. 146808742110012
Author(s):  
Nicola Giramondi ◽  
Anders Jäger ◽  
Daniel Norling ◽  
Anders Christiansen Erlandsson
Keyword(s):  
Direct Injection ◽  
Engine Performance ◽  
High Load ◽  
Operating Conditions ◽  
Injection System ◽  
Injection Timing ◽  
Diesel Combustion ◽  
Heavy Duty ◽  
Pure Ethanol ◽  
Ethanol Combustion

Thanks to its properties and production pathways, ethanol represents a valuable alternative to fossil fuels, with potential benefits in terms of CO2, NOx, and soot emission reduction. The resistance to autoignition of ethanol necessitates an ignition trigger in compression-ignition engines for heavy-duty applications, which in the current study is a diesel pilot injection. The simultaneous direct injection of pure ethanol as main fuel and diesel as pilot fuel through separate injectors is experimentally investigated in a heavy-duty single cylinder engine at a low and a high load point. The influence of the nozzle hole number and size of the diesel pilot injector on ethanol combustion and engine performance is evaluated based on an injection timing sweep using three diesel injector configurations. The tested configurations have the same geometric total nozzle area for one, two and four diesel sprays. The relative amount of ethanol injected is swept between 78 – 89% and 91 – 98% on an energy basis at low and high load, respectively. The results show that mixing-controlled combustion of ethanol is achieved with all tested diesel injector configurations and that the maximum combustion efficiency and variability levels are in line with conventional diesel combustion. The one-spray diesel injector is the most robust trigger for ethanol ignition, as it allows to limit combustion variability and to achieve higher combustion efficiencies compared to the other diesel injector configurations. However, the two- and four-spray diesel injectors lead to higher indicated efficiency levels. The observed difference in the ethanol ignition dynamics is evaluated and compared to conventional diesel combustion. The study broadens the knowledge on ethanol mixing-controlled combustion in heavy-duty engines at various operating conditions, providing the insight necessary for the optimization of the ethanol-diesel dual-injection system.

Predicting Thermoacoustic Instability in an Industrial Gas Turbine Combustor: Combining a Low Order Network Model With Flame LES

2017 ◽  
Author(s):  
Y. Xia ◽  
A. S. Morgans ◽  
W. P. Jones ◽  
J. Rogerson ◽  
G. Bulat ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Acoustic Waves ◽  
Gas Turbine Combustor ◽  
Network Modelling ◽  
Weakly Nonlinear ◽  
Thermoacoustic Instability ◽  
Reduced Chemistry ◽  
Flame Describing Function ◽  
Industrial Gas Turbine ◽  
Low Order

The thermoacoustic modes of a full scale industrial gas turbine combustor have been predicted numerically. The predictive approach combines low order network modelling of the acoustic waves in a simplified geometry, with a weakly nonlinear flame describing function, obtained from incompressible large eddy simulations of the flame region under upstream forced velocity perturbations, incorporating reduced chemistry mechanisms. Two incompressible solvers, each employing different numbers of reduced chemistry mechanism steps, are used to simulate the turbulent reacting flowfield to predict the flame describing functions. The predictions differ slightly between reduced chemistry approximations, indicating the need for more involved chemistry. These are then incorporated into a low order thermoacoustic solver to predict thermoacoustic modes. For the combustor operating at two different pressures, most thermoacoustic modes are predicted to be stable, in agreement with the experiments. The predicted modal frequencies are in good agreement with the measurements, although some mismatches in the predicted modal growth rates and hence modal stabilities are observed. Overall, these findings lend confidence in this coupled approach for real industrial gas turbine combustors.

scholarly journals Validation of an Eulerian Stochastic Fields Solver Coupled with Reaction–Diffusion Manifolds on LES of Methane/Air Non-premixed Flames

2020 ◽  
Author(s):  
Paola Breda ◽  
Chunkan Yu ◽  
Ulrich Maas ◽  
Michael Pfitzner
Keyword(s):  
Transport Model ◽  
Reaction Diffusion ◽  
Passive Scalar ◽  
Scalar Dissipation ◽  
Combustion Model ◽  
Filtered Density Function ◽  
Detailed Chemistry ◽  
Stochastic Fields ◽  
Reduced Chemistry ◽  
Flame Behavior

AbstractThe Eulerian stochastic fields (ESF) combustion model can be used in LES in order to evaluate the filtered density function to describe the process of turbulence–chemistry interaction. The method is typically computationally expensive, especially if detailed chemistry mechanisms involving hydrocarbons are used. In this work, expensive computations are avoided by coupling the ESF solver with a reduced chemistry model. The reaction–diffusion manifold (REDIM) is chosen for this purpose, consisting of a passive scalar and a suitable reaction progress variable. The latter allows the use of a constant parametrization matrix when projecting the ESF equations onto the manifold. The piloted flames Sandia D–E were selected for validation using a 2D-REDIM. The results show that the combined solver is able to correctly capture the flame behavior in the investigated sections, although local extinction is underestimated by the ESF close to the injection plate. Hydrogen concentrations are strongly influenced by the transport model selected within the REDIM tabulation. A total solver performance increase by a factor of 81% is observed, compared to a full chemistry ESF simulation with 19 species. An accurate prediction of flame F instead required the extension of the REDIM table to a third variable, the scalar dissipation rate.

scholarly journals Large Eddy Simulation of Premixed Combustion With a Thickened-Flame Approach

2009 ◽  
Vol 131 (6) ◽  
Author(s):  
Ashoke De ◽  
Sumanta Acharya
Keyword(s):  
Large Eddy Simulation ◽  
Laminar Flame ◽  
Flame Structure ◽  
Reaction Rates ◽  
Premixed Combustion ◽  
Efficiency Function ◽  
Modeling Approach ◽  
Eddy Simulation ◽  
Reduced Chemistry ◽  
Large Eddy

A thickened-flame (TF) modeling approach is combined with a large eddy simulation (LES) methodology to model premixed combustion, and the accuracy of these model predictions is evaluated by comparing with the piloted premixed stoichiometric methane-air flame data of Chen et al. (1996, “The Detailed Flame Structure of Highly Stretched Turbulent Premixed Methane-Air Flames,” Combust. Flame, 107, pp. 233–244) at a Reynolds number Re=24,000. In the TF model, the flame front is artificially thickened to resolve it on the computational LES grid and the reaction rates are specified using reduced chemistry. The response of the thickened-flame to turbulence is taken care of by incorporating an efficiency function in the governing equations. The efficiency function depends on the characteristics of the local turbulence and on the characteristics of the premixed flame such as laminar flame speed and thickness. Three variants of the TF model are examined: the original thickened-flame model, the power-law flame-wrinkling model, and the dynamically modified TF model. Reasonable agreement is found when comparing predictions with the experimental data and with computations reported using a probability distribution function modeling approach. The results of the TF model are in better agreement with data when compared with the predictions of the G-equation approach.

On adaptively reduced chemistry in large eddy simulations

2011 ◽  
Vol 33 (1) ◽  
pp. 1339-1346 ◽  
Author(s):  
Terese Løvås ◽  
Salvador Navarro-Martinez ◽  
Stelios Rigopoulos
Keyword(s):  
Large Eddy Simulations ◽  
Reduced Chemistry ◽  
Large Eddy

Numerical Modeling of Soot Production in Aero-Engine Combustors Using Large Eddy Simulations

2015 ◽  
Author(s):  
B. Franzelli ◽  
E. Riber ◽  
B. Cuenot ◽  
M. Ihme
Keyword(s):  
Numerical Simulations ◽  
Flame Structure ◽  
Precursor Chemistry ◽  
Turbulent Flames ◽  
Large Eddy Simulations ◽  
Reduced Chemistry ◽  
Tabulated Chemistry ◽  
Large Eddy ◽  
Aero Engine ◽  
Aero Engines

Numerical simulations are regarded as an essential tool for improving the design of combustion systems since they can provide information that is complementary to experiments. However, although numerical simulations have already been successfully applied to the prediction of temperature and species concentration in turbulent flames, the production of soot is far from being conclusive due to the complexity of the processes involved in soot production. In this context, first Large Eddy Simulations (LES) of soot production in turbulent flames are reported in the literature in laboratory-scale configurations, thereby confirming the feasibility of the approach. However numerous modeling and numerical issues have not been completely solved. Moreover, validation of the models through comparisons with measurements in realistic complex flows typical of aero-engines is still rare. This work therefore proposes to evaluate the LES approach for the prediction of soot production in an experimental swirl-stabilized non-premixed ethylene/air aero-engine combustor, for which soot and flame data are available. Two simulations are carried out using a two-equation soot model to compare the performance of a hybrid chemical description (reduced chemistry for the flame structure/tabulated chemistry for soot precursor chemistry) to a classical full tabulation method. Discrepancies of soot concentration between the two LES calculations will be analyzed and the sensitivity to the chemical models will be investigated.

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