Diesel sprays through multi-hole micro-nozzles.

摘要

The current work attempts to experimentally determine the effects of multi-hole micro-nozzles fabricated using the MEMS-LIGA method. Spray behavior is quantified by SMD measurements using Malvern Spraytec system and cone angle, penetration length through use of a digital high-speed camera.; MEMS-LIGA based method was chosen as the method of fabrication for its ability to fabricate diameters below the EDM capability with a known and high-precision for nozzle diameter and length. The advantage of the LIGA method is quality of the nozzle cross-section and the ability to maintain very close tolerances in diameter and nozzle-to-nozzle distance. A total of 17 planar (2D) and 8 curved (3D) nozzles were tested at different injection pressures.; The experimental setup was devised in such a way that SMD and high speed movies could be taken simultaneously in a newly setup HEUI system.; This current work documents the effects of Injection (Rail) Pressure, number of micro-nozzles and nozzles' placement. The results suggest that the multi-hole micro nozzle behavior is to some extent similar to that of a single hole nozzle but additional variables like number of nozzles, solid cone angle and placement play a critical role and are specific to the multi-hole behavior.; The SMD seemed to increase almost linearly for the 2D nozzle with increase in number of nozzles, but almost remained a constant for the 3D nozzle for a few number of nozzles and then it appears the SMD values starts to increase steeply. For small number of nozzles, it was found within the present experimental condition and nozzle diameter-to-diameter distance that the nozzle placement had almost no effect on SMD values but the penetration was noticeably affected by nozzle placement. The spray structures of the 3D and the 2D nozzles were quite different; it was also found that spray interaction exists even for a 3D nozzle having just 2 holes.; The current work will help in better understanding the multi-hole nozzle behavior and motivate future work on the other aspects of multi-hole behavior in both cold and hot environments.