Optimization Of Start Of Combustion Timing For Methanol And Petrol As Two Alternative Fuels For A Single Cylinder Spark Ignition Engine

This paper presents the comparative results for optimization of the start of combustion timings for methanol and petrol as two alternative fuels for a single cylinder spark ignition engine. The results were generated by the computational thermodynamic investigations in the professional internal combustion simulation software AVL BOOST. The results were computed at the maximum engine speed of 6000rpm under rich mixture conditions for both methanol and petrol corresponding to the possible development of maximum power. The software uses the basic conservation laws of mass, energy and momentum for computing the values of thermodynamic and gas dynamic variables in all the components of the modeled engine. The values of the thermo-dynamic and gas dynamic variables are computed throughout the four stroke cycle on crank angle basis. The software uses the numerical finite volume method for solving the conservation equations for mass and energy and momentum in the manifolds for computing the properties of air and exhaust gas. The thermodynamic simulations in the engine cylinder are based on solving the first law of thermodynamics for open and closed cycles.

First the modeled engine was run in petrol mode and the results were simulated for engine performance and emissions characteristics. The result was also computed for the octane demand of the engine under variable start of combustion timing operation. The computational investigations were repeated with methanol as an alternative fuel to petrol.

The current spark ignition engine design is based on the octane ratings of the commercial spark ignition engine fuels. The results of the computational investigations on the basis of start of combustion timing, which follows the spark timing of the engines, show how the performance and emission characteristics of the spark ignition engines can be changed or optimized further. Keywords: Start of Combustion Timing, Spark Ignition, Internal Combustion Engine, Methanol, Petrol, Octane Requirement, Performance and Emissions.