Development of Micro-Diesel Injector Nozzles via MEMS Technology and Initial Results for Diesel Sprays

We have developed and used micro-machined injector nozzles with commercially produced diesel injection systems that 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-diesel injector nozzles, and micro-systems technology was also employed in our macro-instrumentation.

Fourteen different circular plates (nickel-iron alloy) were fabricated with deep X-ray lithography and electroplating technology. Five plates that have a single orifice were fabricated to investigate the effect of orifice diameter on spray characteristics; i.e., 40 to 260 microns. The spacing between multiple orifices was also varied; e.g., two plates that each had 41 orifices and 169 orifices, respectively, with a diameter of 40 microns. Finally, three plates with non-circular orifices were also made to examine the effect of orifice shape on spray characteristics. One plate has a cross shape orifice and the others have triangular shape orifices. These nozzles were then attached to a Lucas injector and its associated injection system was used for the spray experiments.

Given this novel injection system, diesel fuel spray characteristics of selected micro-machined diesel nozzles were investigated experimentally. The nozzles were also structurally analyzed for integrity for multiple injections as well as spray simulations were performed to compare to the observed data with the KIVA spray code. Our design and fabrication process and preliminary spray results are described in this paper with comparative analytical results.