An Analysis of Swirl Injector Spray Properties under High Injection Pressure Using the PIV Method

The flow velocity fields of swirl injector sprays for direct-injection gasoline engines were measured by using the PIV method. This method made it possible to measure not only transient and complicated spray droplet velocities but also the surrounding air velocity caused by spray formation and to analyze the mechanism of spray formation. In this study, two nozzles with different spray angles were used to analyze the effects of injection pressure and ambient pressure on spray properties and the results made clear the mechanism of spray formation. It was observed in particular that under a condition of high injection pressure (20 Mpa) with high ambient pressure, spray penetration after the injection period was longer than that obtained under low injection pressure (10 Mpa). This is attributed to both the higher spray velocity and the greater surrounding air velocity.