| Micro-machined diesel injector nozzles have been developed and used with commercially produced diesel injection systems in the study of spray dynamics. Such a system, properly designed, may have the capability to improve the spray behavior in DI diesel engines due to the improved atomization and fuel-air mixing.; In this work, fourteen micro-planar orifice nozzles were fabricated using the LIGA technique (deep X-ray lithography and electroplating technology). The nozzles are made of permalloy, a 78% nickel and 22% iron alloy. The circular orifice diameters were varied from 40 to 260 microns and the number of orifices was varied from one to 169. Three nozzles with non-circular orifices were also fabricated. These nozzles were then attached to commercial injectors and the associated injection systems were used for the spray experiments.; Given these novel injection systems, jet spray characteristics of micro-planar orifice nozzles were investigated experimentally using optical diagnostic techniques, at room temperature and under quiescent gas conditions, in a pressurized constant volume cylindrical chamber. Current test results show expected qualitative trends in spray kinematics and drop sizes, but the quantitative magnitudes of the behavior are less dependent on orifice geometry than first anticipated. Coalescence droplet collisions among adjacent sprays were apparent for the multiple orifice nozzles because all the orifices in the micro-planar nozzles were aligned in the same direction with limited spacing.; To overcome the possible effects of orifice spacing and a planar spray, a novel MEMS fabrication technique was developed. A new set of micro-hemispherical nozzles were developed using this modified LIGA technique to minimize coalescence and improve fuel-air mixing among adjacent sprays. |
