Imaging the ignition of dense, inhomogenous liquid fuel sprays at elevated temperatures and pressures

Abstract

This paper investigates the forced ignition of inhomogeneous, dense liquid fuel sprays. The fuel spray is pure n-Heptane, injected with a prototype gasoline direct injector designed by Delphi for the Engine Combustion Network's Spray G research. This spray is ignited by a laser spark, delivered by a custombuilt high precision laser traverse system. The spray ignition process is recorded with a high-repetition rate schlieren imaging system. The impact of changes in chamber pressure and temperature on ignition probability statistics are investigated. Ignition probability is reduced by increasing chamber pressure and promoted by increasing chamber temperature. At a constant laminar flame speed, the impact of chamber temperature increase is greater than that of chamber pressure increase.