Compound Port Fuel Injector Nozzle Droplet Sizes and Spray Patterns

The goal of this research was to determine an empirical method of relating the droplet sizes and the spray patterns to the parameters and the geometries of the compound nozzles. Two different types of compound nozzles were studied, the compound silicon micro machined nozzle and the compound metal disk nozzle. Several different orifice geometries of each nozzle type were examined. The injector components upstream of the compound nozzle of two different types of injectors were also studied. A nondimensional characterization of the droplet sizes and the mass flow rates was proposed.

The results of this study show that there exists optimum geometric features that will produce sprays with the minimum steady state and dynamic Sauter mean diameter. The spray of a compound nozzle can be characterized by the atomization efficiency and the discharge coefficient. Nozzle testing results show that many flow characteristics are developed in the compound nozzle. The compound silicon micro machined nozzles produce similar droplet sizes in both of the injectors studied. The compound metal disk nozzles produce sprays with droplet sizes similar to the compound silicon micro machined nozzles. The spray pattern is determined by the direction of the velocity vectors developed inside the compound nozzle. A split spray can be produced by controlling the direction of these velocity vectors and enhanced with modifications to the cavity geometry.