Fuels and Combustion in Engineering Journal 53 Numerical Investigation of the Effects of Air/Fuel Ratio on Combustion in a Spark Ignition Engine (original) (raw)
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Simulation of Combustion in Spark Ignition Engine
—In an Internal Combustion Engine cyclic variations in the combustion process result into varied air fuel mixture within the cylinder, particularly in the vicinity of spark plug. These leads to incomplete burning of fuel, thus reducing the combustion efficiency and responsible for knocking. Monitoring of air fuel ratio may help in improving combustion conditions leading to engine efficiency. In the present work simulation studies are carried out on the in-cylinder conditions of a four stroke single cylinder spark ignition engine using the combustion model in ANSYS Fluent. The Simulation is confined to phases between IVC to EVO to reduce the computational time. The physical running conditions of the engine are recorded and used as input parameters for modeling the simulation. The simulation is run for a particular air fuel ratio by defining the mean mixture fraction and variance. The Equivalence Ratio of the engine is calculated based on its running condition, using this equivalence ratio simulation has been carried out and the peak temperature and pressure are evaluated. These pressure and temperature are compared with the real time values.
A Case Study of Combustion Modeling in a Spark Ignition Engine Using Coherent Flame Model
2014
In this study, a computer simulation was performed, to visualize fluid flow and combustion characteristics of a single cylinder spark ignition engine. The complete engine cycle process (inlet, compression, expansion and exhaust strokes) in gasoline engine model was investigated using RANS (Reynolds Averaged Navier-Stokes) and CFM (Coherent Flame Model) approaches offered by Star-CD/es-ice. Simulations were done for the compression ratio 8:1 and 1200 rpm engine speed. C8H18 (iso-octane) was used as the engine fuel. In the numerical simulations to model turbulent flow field, k - e RNG turbulence model was selected with Angelberger wall functions. Static spark advance was set at 20 CA bTDC during the simulations. Fluid flow in the cylinder was observed during all the engine strokes. Especially, just before the exhaust valve open, some numerical abnormal situations were detected. It was observed that the pressure and temperature gradients between cylinder and exhaust port caused these a...
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.
A mathematical and simulation model has been developed to simulate a spark ignition engine operation cycle. The programme written from this simulation model and modified so can be used to assist in the design of a spark ignition engine for alternative fuels as well as to study many design parameters such as the effect of engine design parameter like stroke and diameter of the cylinder on the performance and exhaust emissions of spark ignition engines. In this paper, the description of three type of engines design parameters according to (stroke/diameter) which are called under square, square and over square engines using three type of fuel (gasoline, LPG, CNG) singly have been taken. The variations of power output, thermal efficiency, specific fuel consumption, ignition delay, temperature of exhaust gases, heat loss and the exhaust emissions (CO2, CO, NO, O2) by volume, were calculated for each type of engine and then comparing the results to investigate how to increase engine efficiency and reduce exhaust emissions. The accuracy of the present model is confirmed by comparison with experimental result that have established by previous literatures and the results were agreement with literatures. The main results obtained from the present study shows that, the square engines (S/D=1) can be considered as most efficient, modern and suitable design for engines running by gasoline and alternative fuels like LPG and CNG, because of higher power output due to the suitable piston area for pressure distribution. The area of flame front which may create higher combustion qualities and higher thermal efficiency through faster burning and lower overall chamber heat loss, also, the potential of the square engines (S/D=1) for indicate specific fuel consumption was 4% improved.
Simulation studies of combustion in spark ignition engine using OpenFOAM
FME Transactions, 2020
The open source Field Operation and Manipulation (OpenFOAM) software was used to investigate the performance of a fully premixed, modern highperformance 4-valve, iso-octane, dual overhead cam (DOHC) engine with quasi-symmetric pent roof combustion chamber running at 1500 revolutions per minute. The peak pressure occurred at the TDC and had a value of about 30 bar. The results from this study show that the maximum combustion temperature occurred at approximately 95 degrees crank angle ATDC and has a volume averaged value of about 2700 K ° , whereas the actual computed peak temperature was found to be about 3000oK and it occurred at grid point 12630. The other temperatures which were found to be higher than the volume averaged temperature were found to be in the range 2968.81 2974.01 K to K ° ° and correspond to grid point positions 12630 to 12633.The flame-wrinkling factor, / t u S S = Ξ was found to be in the range 1.0 ≤ Ξ ≤ 3.8. The dynamics of the regress variable b was accurately...
Depletion of fossil fuels and environmental pollution concern has led researchers to develop alternate fuels. Alcohols are promising alternative. Ethanol can be blended in gasoline without modification in engine to improve performance characteristics. Since, field testing is expensive and time consuming and moreover it is difficult to maintain favourable condition throughout the experiment. Hence it is easy and convenient to carry out the simulation study in MATLAB environment. This paper put emphasis on the study of engine performance characteristics with ethanol-gasoline blend, a cylinder by cylinder model is designed in MATLAB/Simulink. Whole model is built in the form of blocks which are differential and empirical formulas of engine parameters. These formulas are describing the engine behaviour with respect to crank angle. The pressure inside the cylinder is predicted with another line of information of heat input. Heat input needs data from the mass flow and burn characteristics of combustible fuel which is described by Weibe function. Pressure obtained will be converted to mean effective pressure by subtracting frictional losses. Finally the brake mean effective pressure is calculated. The parameters calculated are brake power, brake specific fuel consumption, fuel consumed, brake thermal efficiency, burn duration and exhaust gas temperature. In this study it is found that ethanol blend with gasoline increases brake power and brake thermal efficiency by lowering the exhaust gas temperature.
Considering the energy crises and pollution problems today, investigations have concentrated on decreasing fuel consumption by using renewable alternative fuels and on lowering the concentration of toxic components in combustion products. A simulative model for establishing the performance parameters of spark ignition engines fueled with a range of fuels (gasoline, ethanol, or hydrogen) and their mixture is presented. The incidence of pre-ignition and its relative intensity as well as cyclic variations are also accounted for. The 2-zone incorporates a procedure for deriving an estimate of the effective duration of combustion and the associated mass burning rate for various operating conditions and fuels. A system of first-order ordinary differential equations was obtained for the pressure, mass, volume, temperature of the burned and unburned gases, heat transfer from the burned and unburned zone, mass flow into and out of crevices, and the composition of combustion products. The mathematical and simulation model has been developed, tested, and verified against the experimental data to simulate a 4-stroke cycle of a spark ignition engine fueled with gasoline, ethanol, or hydrogen as a single fuel or their mixture. The results obtained from the present study have shown the capability of the model to predict satisfactorily the performance and emissions including the incidence of pre-ignition at various engine-operating conditions. A good agreement was obtained between the results of the present model and the experimental results.
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 ...