Experimental study on the spray atomization of a multi-hole injector for spark ignition engines fuelled by gasoline and n-butanol

Alcohols are largely used in spark-ignition (SI) engines as alternative fuels to gasoline. Particularly, the use of butanol meets growing interest due to its properties that are similar to gasoline, if compared with other alcohols. This paper aims to make a comparative analysis on the atomization process of gasoline and n-butanol fuel injected by a multi-hole injector nozzle for spark ignition engines. Phase Doppler Anemometry technique was applied to investigate the behavior of a spray emerging from a six-hole nozzle for direct injection spark ignition engine applications. Commercial gasoline and pure n-butanol were investigated. The fuels were injected at two pressures: namely at 5 and 10 MPa, in a test vessel at quiescent air conditions, ambient temperature and backpressure. Droplets diameter and velocity were estimated along the axis and on the edge direction of a jet through Phase Doppler Anemometry in order to provide useful information on the atomization process. Gasoline and n-butanol provided different results in droplets size and velocity. The higher viscosity and surface tension of n-butanol resulted in bigger droplets size and higher velocity along the jet axis at 10 MPa of injection pressure. The difference in size and velocity was lower by decreasing the injection pressure and for locations farther from the nozzle