CNG-Gasoline Mixture Combustion Simulation in a Spark Ignition Engine Using a Two-Zone Model

The use of numerical methods to predict thermodynamics of combustion has been longestablished, especially in studies related to internal combustion engines. In the present work, a computational code has been developed to simulate the combustion of CNG-gasoline mixture as an alternative fuel in a spark ignition engine. The use of a zerodimensional, two-zone combustion model in this study, leads us to reducing the computational time and achieving results with acceptable accuracy. The compression, combustion and expansion processes are simulated sequentially. The ideal gas state equation, and conservations of mass and energy are solved as the main equations for each simulation step and in each zone. The Woschni’s heat transfer model is used to estimate the heat transfer rate between the cylinder gases and its wall. The pressure and temperature variations as well as the burnt mass fraction variation are predicted as a function of the crank angle. The calculated pressure and temperature are validated by experimental data. Finally, an exponential curve in the form of Wiebe function is fitted on the burnt mass fraction using the least squares method in order to estimate a new set of Wiebe’s empirical constants. Such predictions will be useful to study the effects of some other engine variables on its combustion behavior.

CNG-Gasoline Mixture Combustion Simulation in a Spark Ignition Engine Using a Two-Zone Model Keywords:

spark ignition engine , two-zone model , Wiebe function , alternative fuels