Methodologies for Flame Propagation Velocity Determination in Spark Ignited Engines

Fossil fuels and biofuels usage in internal combustion engines are the main source for vehicular propulsion. This justifies the intense worldwide research and development to comply with the challenges of increasing efficiency and emissions reduction. The modeling of commercial fuels and engine combustion processes presents great challenges. There is also the need to better understand how different fuel components interact and influence engine combustion and performance parameters. In previous works, components selection and engine dynamometer tests were done to identify representative surrogate fuels for commercial Brazilian gasoline. It was concluded that formulations with n-heptane, iso-octane, toluene and ethanol can be used to model oxygenated gasolines. Methodologies were implemented to evaluate the influence of the fuel components on fuel properties and several engine combustion and performance parameters. The potentials of each component and corresponding chemical group were identified. In the present work, the same surrogate fuels were used to develop a methodology to calculate the in-cylinder flame propagation velocity in a commercial engine, using in-cylinder pressure measurements. Further, mathematical modeling was developed to calculate this combustion parameter, based on fuel laminar flame velocity at standard condition. The mathematical relations were designed considering the intake Reynolds number, temperature and pressure of the unburned gases inside the cylinder. The results put together information and methodologies that can contribute to the simulation of the combustion process in spark ignited engines.