The Effect of Elliptical Diesel Nozzles on Spray Liquid-Phase Penetration under Evaporative Conditions

Abstract

Elliptical diesel nozzles affect the fuel–air mixing process, and thus combustion and exhaust emissions. Experiments were conducted to study biodiesel spray liquid-phase behaviors for elliptical and circular nozzles through the Mie-scattering method under evaporative conditions. Based on the measurements, the results show that the elliptical nozzle spray liquid-phase penetration is smaller than the circular one under steady-state conditions. The deformation and the axis-switching behaviors of the elliptical jet are helpful in accelerating the breakup of the liquid core. Moreover, the injection pressure has little impact on the penetration of the liquid-phase spray for either geometrical orifice. Additionally, increasing the ambient temperature can reduce the penetration of liquid-phase spray, because an increase in temperature increases the rate of evaporation. The differences in steady liquid-phase penetration between circular and elliptical sprays decrease as the ambient temperature increases. Additionally, increasing the backpressure can decrease the liquid-phase penetration. The differences in steady liquid-phase penetration between circular and elliptical nozzles are reduced with the increase in backpressure, probably due to the axis-switching and deformation behaviors of the elliptical jet being restrained under high-backpressure conditions. Finally, the application of an elliptical orifice is beneficial for decreasing the spray liquid-phase penetration, and thus avoiding the fuel impingement in small engine combustion chambers. The lower liquid-phase penetration for elliptical spray indicated higher fuel and air mixture quality, which is helpful for reducing the diesel engine exhaust soot emissions.

Investigation on the effect of the flow passage geometry of diesel injector nozzle on injection process parameters and engine performances

“…Comparative analysis of nozzle internal flow and spray development between circular and elliptical nozzle orifices have been performed in a large number of works such as. [44][45][46][47][48] Spray development characteristics are not only sensitive to the average values of flow parameters at the nozzle orifice outlets and also to the distribution of these flow parameters at the nozzle orifice outlets. 45,47 The latter can be obtained only by computational fluid dynamics (CFD) simulations, which revealed that the turbulence subjected to cavitation induces a greater spreading angle in the major axis plane.…”

“…44,47 In comparison with circular orifices, the liquid jet of elliptical orifices is more unstable 44 and has a higher spray cone angle, especially in the major axis plane, and a shorter penetration. [46][47][48] Additionally, more elliptical nozzles produce a greater improvement of air entrainment. 47 Mohammadi et al 49 investigated the internal flow and spray behaviors for a mini-sac nozzle with the orifice, having a spiral rifling-like guide, by coupling the nozzle flow simulation with spray modeling.…”