Characteristics of a 2-phase injector for 4-stroke direct-injection stratified-charge(DISC) engine were studied. Constant volume chamber (CVC) was made for this study and spray characteristics were investigated using TV imaging system. First, air and fuel mass calibrations were carried out and their operating reliabilities were confirmed up to 6000rpm. Spray characteristics were explored varying operating conditions such as ambient air density, air supply pressure, air liquid ratio(ALR), and injected fuel mass. Lower ambient air density, higher air supply pressure and ALR, and less injected fuel mass produced better atomized sprays. At standard condition Sauter mean diameter(SMD) was about 13 ㎛. A SMD correlation to these variables was found. Most of drop-size distributions from the 2-phase injector sprays were found out to be similar regardless of varying experimental conditions or measured times and positions of sprays from which the log-Bolzman function was known to be the best fitting function. It was recognized that the secondary poppet bouncing appearing at last injection stage producing large droplets must be controlled.
