Direct Injection of Variable Gasoline/Methanol Mixtures: Injection and Spray Characteristics

The injection rate modulation and the spray characteristics are determining factors for the quality of mixture formation when applying GDI. Their variation with load and speed is a basic criterion for the adaptability of a type of injection system to an engine with known requirements. The increased interest for the utilization of regenerative fuels - such as methanol obtained from biomass - as well as the success of previous utilization scenarios of variable gasoline/methanol mixture using manifold injection formed the base of the present analysis: the paper describes the results concerning injection performances and spray characteristics when using gasoline/methanol mixtures with different ratios in a direct injection system with high pressure modulation. The results are compared for different parameters of the injection systems as follows: injection volume, injector opening pressure, needle lift, pintle/seat geometry. The injection performance and the time-related spray characteristics using a laser sheet technique were analysed for different gasoline/methanol ratios. The influence of mixture content on the injection parameters results as moderate. This is a valid argument for modeling and optimization of the internal mixture formation process using direct injection of gasoline/methanol mixtures.