High pressure effervescent atomization: effect of ambient pressure on spray cone angle

Cone angles of sprays formed by a high injection pressure effervescent atom izer were investigated as part of a study concerning the application of eff ervescent atomization to diesel fuel injection. Spray cone angles were stud ied in high ambient density environments that simulate conditions inside th e combustion chamber of a diesel engine at the end of compression. Cone hal f-angle is reported for different injection pressures (12.6-36.5 MPa; all p ressures reported in this work are absolute), atomizing gas-to-liquid ratio s by mass (GLR - 0.8-13.6%) and ambient pressures (0.27-5.5 MPa). Results s how that cone half-angle lies between 5.8 and 11.5 degrees over the entire range of independent parameters studied, and increases linearly with increa sing injection pressure or GLR at all ambient pressures. A more interesting result is that the cone angle first decreases when the ambient pressure in creases from 0.27 to 1.5 MPa, but then increases as ambient pressure rises from 1.5 to 5.5 MPa. This is thought to occur because the two-phase flow le aving the injector is under-expanded at low ambient pressures. The followin g correlation for cone angle is developed from the measured data: alpha /2 = (0.15GLR) + (0.039P(inj)) + (0.0451P(amb)(4) - 0.6211P(amb)(3) + 2.7551P( amb)(2) - 3.62P(amb)) + 7.0. (C) 2001 Elsevier Science Ltd. All rights rese rved.