Abstract
In diesel engines, fuel mixing is an important process in determining the combustion efficiency and emissions level. One of the measures used to achieve fuel mixing is controlling the nature and behavior of the fuel spray by shaping the injection rate. The mechanism underlying the behavior of the spray with varying injection rates before the start of combustion is not fully understood. Therefore, in this research, the fuel injection rate shape is investigated to assess the spraying and mixing behavior. Diesel sprays with different ambient temperatures and injection pressures are modeled using the CONVERGE-CFD software. The validation is performed based on experimental data from an Engine Combustion Network (ECN). The verified models are then used to analyze the characteristics of the diesel spray before and after the end-of-injection (EOI) with four fuel injection rate shapes, including a rectangular injection rate shape (RECT), a quick increase gradual decrease injection rate shape (QIGD), a gradual increase gradual decrease injection rate shape (GIGD), and a gradual increase quick decrease injection rate shape (GIQD). The spray vapor penetrations, liquid lengths, evaporation ratios, Sauter mean diameter (SMDs), distributions of turbulence kinetic energy, temperatures, and equivalence ratios were compared under different injection rate shapes. The results show that the QIGD injection rate shape can enhance mixing during injection, while the GIQD injection rate shape can achieve better mixing after the EOI.
Highlights
Diesel engines find widespread applications in many industries, including transportation, agriculture, and power generation, among others
Dezhi Zhou et al [12] found that higher boot injection velocity and shorter boot injection duration resulted in shorter ignition delay and more fuel burning at the premixed combustion stage
This suggests that a higher injection pressure will often lead to a better spraying process, that this is one of the most effective ways to meet the efficiency requirements, and that this process has a potential benefit in diesel engine performance [13,14,15]
Summary
Diesel engines find widespread applications in many industries, including transportation, agriculture, and power generation, among others. Dezhi Zhou et al [12] found that higher boot injection velocity and shorter boot injection duration resulted in shorter ignition delay and more fuel burning at the premixed combustion stage This suggests that a higher injection pressure will often lead to a better spraying process, that this is one of the most effective ways to meet the efficiency requirements, and that this process has a potential benefit in diesel engine performance [13,14,15]. Injection rate parameters, such as injection velocity, injection mass quantity, and injection duration, have a significant influence on the fuel mixing and combustion process [18] Many of these investigations considered how the diesel spray mixing process behavior can increase mixing efficiency by studying the effect of the injection rate shape. The results of this study are expected to provide useful insights for developing an effective fuel injection rate design for future diesel engines
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