Fuel Injector 127-8222 127-8216 127-8205 0r-8682 0r-8461 for Caterpillar 3116 3114 Engine

Cavitation Inside High-Pressure Optically Transparent Fuel Injector Nozzles (PART 3)

How the device was sealed, and how the plates were held in place, was not included in the published results. Two forms of string cavitation were observed: one which formed in the vortices attached to the part of the geometry designed to mimic the needle, and another which formed in a vortex that connected two orifice holes.

Badock et al. achieved elevated injection pressures using acrylic nozzles, although much like Arcoumanis et al, the piece was significantly larger than the original injector nozzle[4]. Studying primary breakup of a spray in such a nozzle is impossible due to the lensing effect of the surface of the drilled reliefs which fix the length of the nozzle orifice passages.

Blessing et al. achieved injection pressures of 800 bar using an acrylic injector nozzle with a single off-axis orifice[5]. The design was compact enough to allow the primary breakup of the spray emitting from the nozzle orifice to be studied simultaneously with the in-nozzle orifice cavitation.

Unfortunately, no further information regarding the design, such as dimensions or sealing mechanism, was provided. Another effort which deserves mention is the recent study by Butcher et al[6]. The group constructed a quartz nozzle in order to study flash boiling sprays relevant to spark-ignition engines and even installed a modified needle to reduce the stress concentration in the nozzle from the force of the needle seating. Their injection pressures were limited to 40 bar.

The most recent study that achieved elevated injection pressures is that of Mitroglou et al[7]. The authors examined the cavitation structures inside an optically transparent VCO geometry with six orifice holes. They reached 400 bar, but due to slow flaw growth and the desire to collect enough data to build ensemble averaged images of cavitation structures, the injection pressure was limited to 300 bar. Cavitation was observed on both sides of the orifice, as in the earlier study of Arcoumanis. In this study, string cavitation was observed only during the opening phase of the needle valve, and corresponded to the location of a vortex attached to the injector needle face.