Predicting chemical species in spark-ignition engines (original) (raw)
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Thermodynamic Modeling for Analysing the Performance and Emissions of Spark-Ignition Engines
Journal of Engineering and Sustainable Development, 2020
A thermodynamic modeling for the simulation of a spark ignition engine running on gasoline fuel and other alternate hydrocarbon fuel is presented. This paper aims to develop a simple, fast and accurate engine simulation model by using MATLAB (GUI) program. The model is based on the classical two-zone approach, wherein parameters like the first law of thermodynamics, equations for energy, mass conservation, equation of state and mass fraction burned, heat transfer from the cylinder. Curve-fit coefficients are employed to simulate air and fuel data along with frozen composition and practical chemical equilibrium routines. The mathematical model has the ability to predict the cumulative heat release, cylinder pressure, cylinder gas temperature, heat transfer from the gases to cylinder wall and work done for hydrocarbon fuels using a Zero-dimensional combustion model. In addition, the program has the ability to predict engine performance and exhaust emissions at any condition of engine....
This paper presents a computer-based air-fuel model of spark-ignition (SI) internal combustion engines. The model can be used to analyse the engine's performance with conventional and alternative fuels. The paper describes the mathematical formulation of the model and outlines the main features of its computer code. The model is verified against published results of earlier fuel-inducted air-fuel models and then used to analyse the performance of a SI engine with ethanol and ethanol-gasoline mixture. The engine's efficiency and indicated mean effective pressure are evaluated at different engine speeds, compression ratios and equivalence ratios.
Effects of Various Prevalent Fuels on Spark-Ignition Engines Operation
In order to make the engine operate in a high performance and more environmentally friendly process, other fuels can be used instead of gasoline. In this paper, a comparison among six prevalent fuels, Methanol, Ethanol, Gasoline, Methane, Ethan, and Propane, in a spark ignition internal combustion engine is studied. A computational code is prepared to model spark ignition internal combustion engines. Knowledge of thermodynamic properties in each stroke is prerequisite, thus, firstly, calculation of thermodynamic properties is concerned and then with the assistance of calculated properties, thermodynamic process of each stroke is investigated. This comparison lead us to study important parameters in engines operation such as pollutants (exhaust CO and CO2), indicated power, indicated specific fuel consumption, indicated thermal efficiency and indicated mean effective pressure. The efficient fuel for each calculated parameter is designated by investigation of output data. The results ...
Environmental science & …, 2003
A spark ignition engine is used to determine the influence of fuel composition and air/fuel equivalence ratio on the exhaust emissions of regulated pollutants. Two specific fuel matrices are used: the first contains eight hydrocarbons and the second contains four oxygenated compounds. A specific experimental design is used for these tests. Fuel aromatics increase the exhaust CO, HC, and NO x at stoichiometry, lean and rich conditions. Lambda is more important than fuel composition in the case of CO and HC. At stoichiometry, the addition of oxygenated compounds can decrease exhaust CO, HC, and NO x up to 30%, 50%,and 60%, respectively. Under these conditions, the addition of 5% of 2-propanol is the most effective for the reduction of CO, the addition of 20% of ethanol for the reduction of HC, and this of 5% of methyl tributyl ester (MTBE) for the NO x . The addition of oxygenated compounds can decrease CO by 30% at lean conditions, while no decrease is observed at rich ones; HC and NO x can decrease up to 30% and 80%, respectively, under lean conditions and 50% under rich ones. At all lambda tested, exhaust NO x increases with the addition of 20% of 2-propanol. ES026321N FIGURE 7. Influence of fuel H/C and O/C ratios on the emission of CO and HC. All fuels used for the five λ.
Numerical Simulations and Validation of Engine Performance Parameters Using Chemical Kinetics
IntechOpen eBooks, 2022
Use of detailed chemistry augments the combustion model of a three-dimensional unsteady compressible turbulent Navier-Stokes solver with liquid spray injection when coupled with fluid mechanics solution with detailed kinetic reactions. Reduced chemical reaction mechanisms help in the reducing the simulations time to study of the engine performance parameters, such as, in-cylinder pressure in spark ignition engines. Sensitivity analysis must be performed to reduce the reaction mechanism for the compression and power strokes utilizing computational singular perturbation (CSP) method. To study a suitable well-established surrogate fuel, an interface between fluid dynamics and chemical kinetics codes must be used. A mesh independent study must be followed to validate results obtained from numerical simulations against the experimental data. To obtain comprehensive results, a detailed study should be performed for all ranges of equivalence ratios as well as stoichiometric condition. This gives rise to the development of a reduced mechanism that has the capability to validate engine performance parameters from stoichiometric to rich mixtures in a spark ignition engine. The above-mentioned detailed methodology was developed and implemented in the present study for premixed and direct injection spark ignition engines which resulted in a single reduced reaction mechanism that validated the engine performance parameters for both engine configurations.
The Proceedings of the International symposium on diagnostics and modeling of combustion in internal combustion engines, 2001
/ Owing to continuing air pollution problems, stringent regulations are being enforced to reduce unburned hydrocarbon (HC) emissions from spark ignition engines. A number of attempts have been reported on the sources of HC emissions. The crevices are a major source of unburned HC emissions in spark ignition engines. The largest of crevice regions is the piston-ring crevice, however head-gasket, spark plug, and valve seat crevices are not insignificant. After the end of primary engine combustion, some of unburned HCs from crevices are oxidized upon mixing with hot burned gases during the expansion and exhaust processes. The others are emitted to the exhaust port or retained in the cylinder with the residual gases to be recycled in the next cycle. Some of unburned HCs that leave the cylinder are oxidized at the exhaust port. The oxidation process is considered as the dominant HC removal process during engine start-up and warm-up periods. Therefore, quantifying the HC oxidation in the cylinder is potentially important, but a systematic investigation of the HC oxidation has not been conducted due to the difficulties and limitations of engine experiments. A 3-dimensional simulation was developed to predict the oxidation rate of unburned HCs in combustion chamber of a propane-fueled spark ignition engine with consideration of flow, mixing, and heat transfer. The computational moving mesh with the piston and head-gasket crevices was constructed for a commercial 4-valve spark ignition engine. A FAE premixed turbulent combustion model and a flame wall quenching model were applied to simulate flame propagation. In order to predict the unburned HC oxidation, a 4-step oxidation model was used. The mixing, oxidation, and exhausting of unburned HCs are examined, and the relative importance of different crevices was studied. 68.1% of fuel from the crevices are oxidized during the expansion and exhaust processes, and ethylene corresponding 17.8% of oxidized fuel are produced by the fuel oxidation. Head-gasket crevice HCs are exhausted early from blowdown period, on the other side, highly concentrated piston crevice HCs are mainly emitted in the end of the exhaust process. Different locations of crevices influence the oxidation rates, exhaust timings and exhaust degrees. The THC oxidation rate of the piston and the head-gasket crevices are 61.3% and 68.8% respectively. Consequently, the piston crevice contributes to 82.4% and head-gasket crevice does to 17.6% of the engine-out THC emissions relatively. The relative importance of different crevices must be evaluated by considering their shapes, positions, movements, exhaust processes, and engine operating condition as well as volumes, even though crevice size is considered as the most important respect.
2017
Combustion is one of the main research areas of internal combustion engines. To reduce the air pollution from internal combustion engines, it is required to increase combustion efficiency. In this study, effects of air/fuel ratio were investigated numerically. An axisymmetrical internal combustion engine was modeled in order to simulate in-cylinder engine flow and combustion. Two dimensional transient continuity, momentum, turbulence, energy and combustion equations were solved. k-ε turbulence model was employed. Fuel mass fraction transport equation was used for modeling of the combustion. For this purpose a computational fluid dynamics code was developed by using finite volume method with using FORTRAN programming code. The moving mesh was utilized to simulate the piston motion. The code developed simulates four strokes of engine continuously. In the case of laminar flow combustion, Arrhenius type combustion equations were employed. In the case of turbulent flow combustion eddy br...
Fuel, 2021
Recent research has proven that computational fluid dynamics (CFD) modeling in combination with a genetic algorithm (GA) algorithm is an effective methodology to optimize the design of internal combustion (IC) engines. However, this approach is time consuming, which limits the practical application of it. This study addresses this issue by using a quasi-dimensional (QD) model in combination with a GA to find optimal fuel composition in a spark ignition (SI) engine operated with CH 4 /H 2 /CO fuel blends. The QD model for the simulation of combustion of the fuel blends coupled with a chemical kinetics tool for ignition chemistry was validated with respect to measured pressure traces and NO x emissions of a small size single-cylinder SI engine operated with CH 4 /H 2 blends. Calibration was carried out to assess the predictive capability of the QD model, and the effect of hydrogen addition on the lean limit extension of the methane fueled engine was studied. A GA approach was then used to optimize the blend composition and engine input parameters based on a fitness function. The QD-GA methodology was implemented to simultaneously investigate the effects of three input parameters, i.e., fuel composition, air-fuel equivalence ratio and spark timing on NO x emissions and indicated thermal efficiency (ITE) for the engine. The results found indicated that this approach could provide optimal fuel blends and operating conditions with considerable lower NO x emissions together with improved thermal efficiencies compared to the methane fueled engine. The presented computationally-efficient methodology can also be used for other fuel blends and engine configurations.
Proceedings of the Combustion Institute, 2002
Intake, mixing, and combustion processes are simulated in a direct-injection gasoline engine for three substantially different running conditions, including two full loads with homogeneous charge combustion and a part load with stratified charge combustion. The turbulent Flame Speed Closure (FSC) model is implemented into the FIRE code for the three-dimensional simulations of the combustion processes, which is the focus in the present paper. To take local mixture properties into account, a complex chemistry mechanism consisting of 100 species and 475 reactions is used to calculate the laminar flame speeds and chemical timescales required by the model. A large range of equivalence ratios, pressures, and temperatures are investigated and the combustion limits are determined. The FSC model is extended to capture the postflame oxidation between excess fuel from the rich mixture and excess air from the lean mixture. The modeling of the flow field, mixture composition, and combustion is compared with optical and pressure measurements in a test-rig engine showing good agreement. The simulation of the stratified charge combustion indicates that the major part of the unburned fuel after the combustion originates from the lean mixture. The calculated amount of unburned fuel is in good agreement with the measured HC emissions.