Preliminary Investigation of Propane Spray Structure in an Optically Accessible Direct-Injection, Spark-Ignition Engine

摘要

Liquefied petroleum gas (LPG) has attained a significant positionin various markets throughout the world, as it has numerousbenefits as an automotive fuel in spark-ignition (SI) engines.Fuelling a direct injection (DI) engine with LPG, rather thanconventional, liquid fuels, has the potential to improve fuel efficiencyand emissions output. However, there is little informationpertaining to the operation of LPG in such vehicles. Therefore,this study aims to begin to characterise DI propane sprays,acting as a surrogate for LPG, in a DISI engine at injection timingscorresponding to both an early, homogeneous strategy anda late, stratified strategy. Fuel spray structures are imaged usinga production DISI engine modified to have optical accessthrough a fused silica cylinder liner. Using Mie-scattering toresolve the liquid phase injection, propane sprays are observedto be heavily flash-boiling at both injection conditions. Thisis in contrast to heavier, liquid fuels where flash-boiling generallyoccurs only for chamber conditions well below atmosphericpressure.