Detailed imaging of n-dodecane and ethanol sprays injected in a constant-ﬂow, high-pressure, high-temperature optically accessible chamber was per-formed. High-speed, diﬀused back-illuminated long-distance microscopy was used to resolve the spray structure in the near-nozzle ﬁeld. The eﬀect of injection and ambient pressures, as well as fuel temperature and composition have been studied through measurements of the spray penetration rates, hy-draulic delays and spreading angles. Additional information such as transient ﬂow velocities have been extracted from the measurements and compared to a control-volume spray model. The analysis demonstrated the inﬂuence of outlet ﬂow on spray development with lower penetration velocities and wider spreading angles during the transients (start and end of injection) than during the quasi-steady period of the injection. The eﬀect of fuel com-position on penetration was limited, while spreading angle measurements showed wider sprays for ethanol. In contrast, varying fuel temperature led to varying penetration velocities, while spreading angle remained constant during the quasi-steady period of the injection. Fuel temperature aﬀected injector performance, with shorter delays as fuel temperature was increased. The comparisons between predicted and measured penetration rates showed diﬀerences suggesting that the transient behavior of the spreading angle of the sprays modiﬁed spray development signiﬁcantly in the near-ﬁeld. The reasonable agreement between predicted and measured ﬂow velocity at and after the end of injection suggested that the complete mixing assumptions made by the model were valid in the near nozzle region during this period, when injected ﬂow velocities are reduced.
Mendeley saves you time finding and organizing research
Choose a citation style from the tabs below