This paper presents the effect of compression ratio on the octane requirement, performance and emission characteristics of a V6 TCI BI-TURBOspark ignition engine, using petrol and methane as alternative fuels. The computational investigations were done in order to bring down the size of a spark ignition engine under turbocharged configuration. The aim was also to find out the requirement for mass commercialization of turbo-charged spark ignition engines with improved performance and emissions characteristics.
AVL BOOST, thermodynamic simulation software, was used to carry out these computational investigations. The computational investigations were governed by the laws of thermodynamics. Investigations in the manifolds were further supplemented by using the momentum equation. Models for combustion analysis, frictional power calculations, heat transfer analysis etc are used for assisting in analyzing the behavior of engine on personal computer based computations. The numerical methods are used for solving the equations involved.
A model for a V6 TCI BI-TURBO spark ignition engine was selected for the above mentioned research investigations. The model was first run in the petrol mode under varying compression ratio while keeping the other operating parameters constant corresponding to maximum power generation. The results were generated for the octane number requirement as well as performance and emissions characteristics. The investigations were repeated by using methane as an alternative fuel to petrol for the above engine. The computational investigations on the engine under consideration gave successful performance with both petrol and methane as fuels.
It was observed that by increasing the compression ratio of the engine the power and torque output of the engine increases in both petrol and methane modes. The brake specific fuel consumption of the engine also decreases with both the fuels under consideration. This however requires the octane number of both petrol and methane to be improved for commercial application of this research investigation. The petrol version of the engine gave better suitable results than the methane version of the same engine. It was found that the CO and NOx emissions decrease whereas the HC emissions increase by increasing the compression ratio of the engine for both petrol and methane.
Turbo-charged, Spark Ignition Multi-cylinder Engine, Petrol, Methane, Constant Speed, Variable Compression Ratio, Octane Requirement, Performance and Emissions
