A study on the spray characteristics of a piezo pintle-type injector for DI gasoline engines

We studied the spray flow initiated from a piezo pintle-type injector for DI gasoline engines in an environment supplied by a constant volume vessel by means of laser diagnostics. To fully grasp the effects of the characteristic parameters, including designed spray angle, needle lift, injection pressure (Pinj) and ambient pressure (Pb), on the spray atomization and mixture preparation, particle image velocimetry (PIV) and phase Doppler anemometry (PDA) are used in the experiment, respectively. The gas perpendicularly enters into the outer periphery of the conical spray injected through the pintle-type injector activated by piezo, which creates two large-scale vortices: the vortex A and vortex B. The velocity standard deviation of the spray field is introduced to analyze the gas flow motion in the vicinity of nozzle. The droplet information of spray field is also recorded by PDA in variable boundary conditions. The time dividing method is used to study the droplet characteristics in four parts of spray. The injector with 98° designed spray angle has smaller droplet mean diameter (D10 and D32), due to a larger spray distribution. When the droplet velocity of the spray field is close to 0 m/s, the D10 and D32 hold at around 10 μm and 20 μm, respectively, in atmospheric pressure condition, which are about 20 μm and 40 μm, respectively, at ambient pressure of 1.1 MPa.