The Fuel Spray Structure of High Pressure Direct Swirl Injector for Gasoline Injection System

This paper presents an investigation into global spray behavior and characteristics of injected spray from a High pressure Direct Swirl Injector (HDSI) at ambient conditions. Three types of swirler were designed at the initial development stage and they were used to analyze the relationship between tangential swirl port angle and spray characteristics. The swirler of the HDSI was designed based on these experimental results; being finalized with design of the valve seat and body. Using the “forward scattering image” method for visualization, the fuel and air mixing characteristics were assessed and laser diffraction was used to measure droplet size. Preliminary results regarding spray development showed that mixing increases with injection pressure. It was also found that the design of the swirler influences initial spray angle, and penetration length. Final analysis indicated spray characteristics of HDSI with mean droplet size below 20μm, about 70° of spray angle, wide dynamic flow range and low end linearity. Vibration and operating endurance testing were performed to verify the injector performance.