DEVELOPMENT OF MICRO-DIESEL INJECTOR NOZZLES VIA MEMS TECHNOLOGY AND EFFECTS ON SPRAY CHARACTERISTICS

摘要

Micro-machined planar orifice nozzles have been developed and used with commercially produced diesel injection systems. Such a system may have the capability to improve the spray characteristics in DI diesel engines. The availability of a MEMS (Micro-Electro-Mechanical-Systems) processing sequence supported the construction of micro-planar orifice nozzles, and micro-systems technology was also employed in our macro-instrumentation. To demonstrate this process, fourteen MEMS nozzles were fabricated with deep X-ray lithography and electroplating technology. The nozzles are made of 78% nickel and 22% iron alloy. The circular orifice diameters were varied from 40 to 260 microns and the number of orifices varied from one to 169. Three plates with non-circular orifices were also fabricated to examine the effect of orifice shape on spray characteristics. 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-machined nozzles were investigated experimentally at two different injection pressures (around 25 MPa and 80 MPa). Local drop sizes were measured by the laser diffraction technique, and the average drop sizes of the whole sprays were measured by the light extinction technique. Current test results show expected qualitative trends in spray kinematics and drop size, but the quantitative magnitudes of the behavior are less dependent on geometry than first anticipated. The spray kinematics and drop sizes were found to depend primarily on the total mass flow area regardless of single or multi-hole or different orifice shape. Non-planar configurations are under development and may show improved performance.