Time-resolved pulsed spray drop sizing at elevated pressures

An experimental program was conducted to measure drop sizes in pulsed sprays for diesel and fuel-injected spark ignition engine applications. A forward-scattering unit was designed with a high-speed data acquisition system to permit the measurement of drop sizes in sprays at 0.4-ms intervals. Data were taken at elevated pressures from 0.345 to 3.45 MPa with a 0-deg pintle nozzle. The Sauter Mean Diameter (SMD) and size distribution were calculated using a computational method that is independent of a predetermined distribution function. Results taken at the spray centerline indicate that for most elevated pressures, the SMD in the secondary injection region tended to increase as the pressure in the fuel line decreased and tended to increase with increasing environmental pressure, both suggesting an inverse relationship between drop size and the pressure drop across the nozzle. Also as the environmental pressure was raised, the distribution width decreased at a slower rate than the SMD increased, indicating a spreading of the drop sizes with injection time at elevated pressures. Significant cycle-to-cycle variation in both the SMD and distribution width indicate that cycle-to-cycle variations must be considered in pulsed sprays. In addition, more variation was seen between random rather than consecutive cycles. (Author)