Title: Liquid Sprays Characteristics in Diesel Engines
Description: Experimental measurements were carried out to estimate the liquid penetration length of a diesel fuel jet injected in an inert environment. The effects of the characteristic parameters, i.e. the nozzle diameter, discharge coefficient, injection pressure, and working fluid density were analyzed. The transient fuel injection process was recorded using optical access, and the liquid penetration length before the second break-up regime was measured using the ombroscopy technique. The aim of the present research is to generate a correlation that accurately predicts liquid penetration length at conditions typical of modern Heavy Duty common rail diesel engines operating with direct fuel injection. A statistical analysis of our experimental measurements suggests a power function correlation to model the liquid penetration length. The proposed model is in good agreement with experimental data and yields a correlation coefficient R2 = 93.3 %. Furthermore, the suggested correlation illustrates important details about how the main parameters affect the fuel injection process. The nozzle diameter has the greatest effect on liquid penetration length. A reduction in nozzle diameter yields a shorter penetration length because it causes an earlier start of the second break-up regime. Increasing the injection pressure provokes premature droplet break-up within the jet, which results mainly due to cavitation at the nozzle exit. If the working fluid density in the combustion chamber increases the penetration length is shorter and the second break-up regime is delayed due to the free-share flow between the working fluid and the fuel jet, which produces higher evaporation rates of droplets from the diesel jet. Finally, under the experimental conditions studied here, the discharge coefficient has a negligible effect on the liquid penetration length. However, the discharge coefficient influences the cavitation phenomenon at the nozzle exit and modifies the droplet velocity within the jet.