Influence of Engine like Conditions on Macroscopic as well as Microscopic Spray Behavior of GDI Injector Using Isooctane and Alcohols

Use of bio fuels in a regular spark ignition engine is becoming common in several countries to reduce the dependence on fossil fuels and overall generation of green house emissions. Alcohols such as methanol and ethanol are blended with gasoline when SI engines are considered. Advanced direct injection stratified charge engine technology has gained lot of interest due to its merits over conventional port fuel injection engine. Since the technology is significantly spray controlled, fuel injection and spray behavior under different thermodynamic conditions plays a very important role in successful engine operation. Present work was carried out to understand the spray behavior of isooctane and three alcohols under engine-like pressure and temperature conditions. Selected alcohols were ethanol, isobutanol and n-butanol. A six holes solenoid injector was used for this study. Experiments were conducted in high pressure and temperature spray chamber to determine the liquid penetration length, overall spray cone angle and overall Sauter mean diameter (SMD) of the different fuels under engine relevant conditions. Selected chamber conditions were a) 1.5 bar, 329 K, b) 2.5 bar, 371 K and c) 6.0 bar, 453 K. Mie scattering principle was used to determine the liquid penetration and spray cone angle of the fuels, whereas droplet diameter information was obtained using single component Phase Doppler Particle Analyzer (PDPA). Results showed that thermo-physical properties of the fuel such as vapour/liquid equilibrium, surface tension, density, viscosity and latent heat of vaporization have significant effect on the spray characteristics. Due to its lower latent heat of evaporation, isooctane evaporated faster and hence resulted in the shortest liquid penetration length. The penetration lengths of alcohols were higher due to their comparatively higher latent heat of evaporation. SMD data from the experiments supported this observation.