scholarly journals Modelling of Self-Ignition in Spark-Ignition Engine Using Reduced Chemical Kinetics for Gasoline Surrogates

Fluids ◽  
2019 ◽  
Vol 4 (3) ◽  
pp. 157 ◽  
Author(s):  
Ahmed Faraz Khan ◽  
Philip John Roberts ◽  
Alexey A. Burluka
Keyword(s):  
Chemical Kinetics ◽  
Octane Number ◽  
Kinetic Mechanism ◽  
Spark Ignition ◽  
Chemical Kinetic ◽  
Spark Ignition Engine ◽  
Detailed Chemical Kinetics ◽  
Kinetic Predictions ◽  
Kinetic Mechanisms

A numerical and experimental investigation in to the role of gasoline surrogates and their reduced chemical kinetic mechanisms in spark ignition (SI) engine knocking has been carried out. In order to predict autoignition of gasoline in a spark ignition engine three reduced chemical kinetic mechanisms have been coupled with quasi-dimensional thermodynamic modelling approach. The modelling was supported by measurements of the knocking tendencies of three fuels of very different compositions yet an equivalent Research Octane Number (RON) of 90 (ULG90, PRF90 and 71.5% by volume toluene blended with n-heptane) as well as iso-octane. The experimental knock onsets provided a benchmark for the chemical kinetic predictions of autoignition and also highlighted the limitations of characterisation of the knock resistance of a gasoline in terms of the Research and Motoring octane numbers and the role of these parameters in surrogate formulation. Two approaches used to optimise the surrogate composition have been discussed and possible surrogates for ULG90 have been formulated and numerically studied. A discussion has also been made on the various surrogates from the literature which have been tested in shock tube and rapid compression machines for their autoignition times and are a source of chemical kinetic mechanism validation. The differences in the knock onsets of the tested fuels have been explained by modelling their reactivity using semi-detailed chemical kinetics. Through this work, the weaknesses and challenges of autoignition modelling in SI engines through gasoline surrogate chemical kinetics have been highlighted. Adequacy of a surrogate in simulating the autoignition behaviour of gasoline has also been investigated as it is more important for the surrogate to have the same reactivity as the gasoline at all engine relevant p − T conditions than having the same RON and Motored Octane Number (MON).

Quasidimensional Modeling of Diesel Combustion Using Detailed Chemical Kinetics

2017 ◽  
Vol 139 (8) ◽  
Author(s):  
Aron P. Dobos ◽  
Allan T. Kirkpatrick
Keyword(s):  
Diesel Engine ◽  
Heat Release ◽  
Chemical Kinetics ◽  
Computational Cost ◽  
Kinetic Mechanism ◽  
Chemical Kinetic ◽  
Detailed Chemical Kinetics ◽  
Air Mixing ◽  
Primary Reference ◽  
Detailed Chemical

This paper presents an efficient approach to diesel engine combustion simulation that integrates detailed chemical kinetics into a quasidimensional fuel spray model. The model combines a discrete spray parcel concept to calculate fuel-air mixing with a detailed primary reference fuel chemical kinetic mechanism to determine species concentrations and heat release in time. Comparison of predicted pressure, heat release, and emissions with data from diesel engine experiments reported in the literature shows good agreement overall, and suggests that spray combustion processes can be predictively modeled without calibration of empirical burn rate constants at a significantly lower computational cost than standard multidimensional (CFD) tools.

A Laminar Burning Velocity Correlation for Hydrogen/Air Mixtures Valid at Spark-Ignition Engine Conditions

2003 ◽  
Author(s):  
Sebastian Verhelst ◽  
Roger Sierens
Keyword(s):  
Chemical Kinetics ◽  
Laminar Flame ◽  
Burning Velocity ◽  
Spark Ignition ◽  
Flame Speed ◽  
Spark Ignition Engine ◽  
Laminar Flame Speed ◽  
Spark Ignition Engines ◽  
Laminar Burning Velocity ◽  
Velocity Correlation

During the development of a quasi-dimensional simulation programme for the combustion of hydrogen in spark-ignition engines, the lack of a suitable laminar flame speed formula for hydrogen/air mixtures became apparent. A literature survey shows that none of the existing correlations covers the entire temperature, pressure and mixture composition range as encountered in spark-ignition engines. Moreover, there is ambiguity concerning the pressure dependence of the laminar burning velocity of hydrogen/air mixtures. Finally, no data exists on the influence of residual gases. This paper looks at several reaction mechanisms found in the literature for the kinetics of hydrogen/oxygen mixtures, after which one is selected that corresponds best with available experimental data. An extensive set of simulations with a one-dimensional chemical kinetics code is performed to calculate the laminar flame speed of hydrogen/air mixtures, in a wide range of mixture compositions and initial pressures and temperatures. The use of a chemical kinetics code permits the calculation of any desired set of conditions and enables the estimation of interactions, e.g. between pressure and temperature effects. Finally, a laminar burning velocity correlation is presented, valid for air-to-fuel equivalence ratios λ between 1 and 3 (fuel-to-air equivalence ratio 0.33 < φ < 1), initial pressures between 1 bar and 16 bar, initial temperatures between 300 K and 800 K and residual gas fractions up to 30 vol%. These conditions are sufficient to cover the entire operating range of hydrogen fuelled spark-ignition engines.

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