Abstract
High pressure diesel injection has many advantages and currently values of up to about 230 MPa are used. The jets generated by these pressures are just subsonic at diesel engine conditions. It is important to examine the next highest range where the jets become supersonic. Using a special technique for experimental purposes only, diesel fuel jets with velocities in the range 600 to 2000 m/s have been generated. Their fundamental characteristics have been determined using shadowgraph visualization. Calculations show that the injection pressure range from 365 MPa to 4.70 GPa for the velocity range considered. While several different nozzle shapes have been considered, these are all smooth, single-hole types.
Cavitating nozzles more similar to the multi-hole types used in diesel engines now need to be tested. Also, as jet penetration at these velocities is likely to be quite high, the jet attenuation needs to be studied. Initial estimates given in this paper indicate that such high pressures may be most beneficial in large engines.