Fundamental Approach to Investigate Pre-Ignition in Boosted SI Engines

Abstract

A comprehensive experimental and theoretical approach was undertaken to understand the phenomenon of pre-ignition and to assess parameters to improve or even eliminate it completely. Oil mixing with fuel was identified as the leading theory of self ignition of the fuel. End of compression temperature has to meet a minimum level for pre-ignition to take place. In this work a comprehensive list of parameters were identified that have a direct and crucial role in the onset of pre-ignition including liner wetting, injection targeting, stratification, mixture motion and oil formulation. Many secondary effects were identified including ring dynamics, ring tension, spark plug electrode temperature and coolant temperature. CFD has been extensively used to understand test results including wall film, A/F ratio distribution and temperature at the end of compression when looked at in the context of fuel evaporation and mixing. Consecutive high speed imaging and other optical measurements were implemented to capture and understand pre-ignition. Quantitative post-processing techniques have been used to convert video to quantifiable parameters. A 3-D comprehensive model of ring dynamics was created to understand the stochastic nature of oil intrusion into the combustion chamber.