Analysis on Behaviors of Swirl Nozzle Spray and Slit Nozzle Spray in Relation to DI Gasoline Combustion

Behavior of sprays formed by slit nozzle as well as swirl nozzles with the spray cone angle in the range of 40° ∼110 ° were studied in a constant volume N₂ gas chamber. The fuels used are iso-pentane, n-heptane, benzene and gasoline. The ambient pressure and temperature were raised up to 1.0 MPa and 465 K, respectively. The injection pressure was mainly set at 8 MPa. Spray penetrates at an almost constant speed for a while after injection start and begins to decelerate at a certain point. This point was judged as breakup point, based on a momentum theory on spray motion, the observation of spray inside and the analysis of the spray front reacceleration which occurs under highly volatile condition. A simple breakup model was proposed taking into consideration the above analysis, and the equation which represents the breakup condition was introduced as the relation among the non-dimensional functions including such factors as spray cone angle, fuel property, injection pressure, ambient pressure and ambient temperature. Based on this relation, the experimental formulas including major design factors were established for breakup condition.