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

Abstract

Micro-machined diesel injector nozzles have been designed, fabricated and used with commercially produced diesel injection systems in the study of spray dynamics. Such a system, properly designed, may improve spray behavior in DI diesel engines due to improved atomization and fuel-air mixing. In this work, fourteen micro-planar orifice nozzles were fabricated using the MEMS (Micro-Electro-Mechanical-Systems) technique. Circular orifice diameters were varied from 40 to 260 microns and the number of orifices was varied from one to 169. Three plates with noncircular 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-planar orifice nozzles were investigated experimentally using optical diagnostic techniques in a pressurized constant volume cylindrical chamber. Local drop sizes were measured by the laser diffraction technique, and average drop sizes of the whole sprays were measured by the light extinction * Corresponding author : Address : 295 Roger Adams Laboratory, Box C-3, 600 South Mathews Avenue, Urbana, IL 61801, USA Tel: +1-217-333-5233 E-mail address: sbaik@scs.uiuc.edu 1 technique. Current test results show expected qualitative trends in spray kinematics and drop sizes, but quantitative magnitudes of the behavior are less dependent on orifice geometry than first anticipated. Droplet coalescence among adjacent sprays were apparent for the multiple orifice nozzles because all the orifices were aligned in the same direction with limited spacing. Non-planar configurations are under development and may show improved performance.