Visualization and Measurements of Sub-Millisecond Transient Spray Dynamics Applicable to Direct Injection Gasoline Engine : Part 2:PDA Measurements and Analysis of Instantaneous Spray Patterns

Abstract

A high-pressure swirl type spray has been experimentally analyzed by using a phase Doppler anemometer(PDA). The experiment was performed with an injection pressure of 5 MPa and an injection frequency of about 46 Hz. The PDA data was obtained in a two-dimensional plane and arranged with the injection phase angle. The arranged data of mean velocity, Sauter mean diameter, and droplet number density were visualized by using commercial software. In this paper, the data were compared with the results of visualization. It is indicated by the experiment that the large velocity and large size droplets initiated from the injector with small spray angle at the beginning of the valve opening duration. This stage was called core jet. In the next stage called quasi umbrella spray, the spray developed with large spray angle. After closing the valve, the spray remains increasing its velocity and diameter. This was caused by the "post injection". Using PDA, the detailed feature of the spray can be discussed with high temporal resolution.