High-Speed/High-Resolution Imaging of Fuel Sprays from Various Injector Nozzles for Direct Injection Engines

A high-speed/high-resolution imaging technique and analysis were applied to study fuel injector spray timed evolution in ambient air and in a motored single-cylinder engine. Alcohol fuel was injected from a mid-pressure injection system into the engine cylinder at shaft speed of 1,000 rpm. The fuel injection system with various nozzles was designed for use in the EPA/NVFEL program to develop clean and efficient engines that use alternative fuels.

A 15W copper vapor laser with a fiber optic delivery system synchronized with a high-speed drum streak camera was utilized to expose films at 5,000 frames per second (fps). The spray characteristics were investigated at 15.0 MPa injection pressure and injection duration range of 3-5 ms. A sequence of successive frames was selected from the films to examine the influence of the injector parameters and the valve lift on the atomization process. The spray penetration was quantified by analyzing the high-speed films. The mean droplet size distributions from the injector nozzles were measured by using the Malvern particle sizer. The results presented are from an ongoing investigation to obtain information on the transient spray properties from several advanced fuel injector technologies for direct injection engine applications.