Effects of the Ambient Conditions on the Spray Structure and Evaporation of the ECN Spray G

The use of Gasoline Direct Injection (GDI) continuouslyincreases due to the growing demand of efficiency andpower output for i.c. engines. The optimization of thefuel injection process is essential to prepare an air-fuel mixturecapable to promote efficient combustion, reduced fuelconsumption and pollutant emissions. Good spray atomizationfacilitates fuel evaporation in i.c. engines thus contributingto the fuel economy and lowering the emissions. Oneof the key features of a multi-hole injector is to provide anoptimal spray pattern in the combustion chamber and a goodmixture homogenization considering the engine-specificcharacteristics such fuel mass-flow rate, cylinder geometry,injector position, and charge motion.This work aims to investigate the injection processes ofan eight-hole direct-injection gasoline injector from theEngine Combustion Network (ECN) effort on gasoline sprays(Spray G, serial #19).The main objective is to evaluate both liquid and vapor phaseenvelope to extend the dataset for the Spray G covering a broaderoperating range. The tests were conducted fluxing iso-octane ina heated constant-volume pressurized vessel. A hybrid opticalsetup, Z-type schlieren and Mie scattering, using a high-speedC-Mos camera as detector, allowed the acquisition of both thevapor and the liquid phases. A customized image-processingprocedure, developed in C# environment, was used for theoutline of both the fuel phases. Different morphologies of the fuelspray were studied as function of the injection pressure, theambient temperature, and the backpressure in the vessel, throughthe measurement of the spray penetrations, areas, and cone angles.Results indicate that global spray parameters such asliquid and vapor penetration as well as spray angle are largelyaffected by charge gas conditions (mainly density). The influencesof ambient and injection conditions were of particularinterest providing fundamental physics insight regarding fuelpenetration and vaporization.