Gas density and rail pressure effects on diesel spray growth from a heavy-duty common rail injector

Formation of nonevaporating sprays from diesel fuel injection through a realistic heavy duty multihole common rail injector is studied in a newly developed high-pressure, high-temperature cell, using digital highspeed shadowgraphy at 4500 frames/s. Gas pressure was varied from 13 to 37 bar (corresponding to densities of 15-42 kg/m3, using N2 at room temperature) and rail pressure from 750 to 1500 bar. The nozzle is carefully characterized and all injection data are analyzed by the method as described in previous work (Klein-Douwel, R. J. H.; et al. Fuel, 2007, 86, 1994-2007). Time evolution of the spray angle and penetration and possible dependences of these two variables on gas density and rail pressure are studied. It is found that after an exponential decay the spray angle reaches equilibrium values between 25° and 31°, which slightly depend on gas density. For spray penetration the dependences on gas density (power of -0.38 ± 0.01) and rail pressure (power of 0.4-0.6) are more pronounced. By using a reference length and time with which penetration data is scaled, it is shown that all data, independent of injection conditions, collapses very well onto a single line which increases as time to the power 0.56 ± 0.01