Characteristics of Air Flow Surrounding Non-Evaporating Transient Diesel Sprays 2000-01-2789
Airflow characteristics surrounding non-evaporating transient diesel sprays were investigated using a 6-hole injector. Particle Image Velocimetry (PIV) was used to measure the gas velocities surrounding a spray plume as a function of space and time.
A hydraulically actuated, electronically controlled unit injector (HEUI) system was used to supply the fuel into a pressurized constant volume chamber at room temperature. The chamber gas densities in this study were 10 kg/m3, 20 kg/m3 and 30 kg/m3. The injection pressure was 96.5 MPa. Two frequency doubled (532 nm) Nd:YAG lasers were used to create coincident laser sheets to illuminate the test section at two instances after start of injection (ASI). The double exposed images of sprays and Al2O3 seed particles were developed and velocity vectors of the gas surrounding the transient diesel sprays were obtained using a numerical autocorrelation PIV method.
A conical control surface surrounding the spray plume was chosen as a representative entrainment surface. The maximum velocities normal and tangential to the conical control surface near the spray plume showed little variation with chamber density. Large differences between the speed of the spray tip and of the measured gas speed near the spray tip were observed. A comparison of the estimated volume of entrained gas from the sides of the spray to the entrained gas at the spray tip due to the overtaking spray indicated that a significant portion of the gas entrainment took place near the liquid spray tip.