Effect of start of combustion timing on the octane requirement, performance and emission characteristics of A V6 TCI bi-turbo spark ignition engine using petrol and methane as alternative fuels

This paper presents the variable start of combustion timing based computational research investigations on a V6 TCI BI-TURBOspark ignition engineusing petrol and methane as alternative fuels. The research investigations are done to explore the octane number requirements of petrol and methane for successfully turbo-charging the spark ignition engines needed for power generation with above mentioned alternative fuels.

The investigations were done by using the professional thermodynamic simulation software named as AVL BOOST. This software uses thermodynamic models for combustion, heat transfer, pollutants formation, frictional power and octane number requirement for fuels. The software also uses the laws of conservation of mass and energy for computing results in the engine cylinders. For thermodynamic calculations in both intake manifold and exhaust manifold the above two laws are supplemented by the law of conservation of momentum. The partial differential equations involved in the simulations are solved by using numerical methods.

First the model for a V6 TCI BI-TURBO spark ignition engine was selected for the above mentioned research investigations.

The model was run in the petrol mode under variable start of combustion timings and results were computed for octane number requirement of the petrol over the entire range of the start of combustion timing. The performance and emissions characteristics of the engine were also studied under the same conditions. The speed and air-fuel ratio were considered corresponding to the condition for maximum power generation

The computational investigations were repeated with the methane version of the same engine. Again the octane ratings needed for methane were computed under variable start of combustion timings. The performance and emission characteristics of the engine were also investigated in the methane mode. The speed and air-fuel ratio were selected corresponding to condition for maximum power generation in the methane mode.

It was observed that for successful commercialization of the multi-cylinder turbo-charged spark ignition engines the octane rating of the petrol needs to be upgraded. This will further help in choosing the start of combustion timing and therefore optimum spark timing of these engines which will help in boosting the power and torque of these engines using the concept of turbo-charging.