Effects of Water-Enriched Intake Air on Performance and NOX Emissions of Small Marine Diesel Engines: A Full Factorial Analysis

The literature identifies three principal techniques for incorporating water into diesel engines: diesel-water emulsions, direct WI, and addition of water into the intake air (WAIA) stream [14-16].Among these, WAIA is highlighted as a practical and efficient option, as it does not typically require major engine modifications and allows controllable water delivery.Whereas water-diesel emulsions require mixing apparatus and surfactants to achieve homogeneity due to differences in density and miscibility [17][18][19], and direct WI depends on auxiliary injectors and advanced control mechanisms [14,20], WAIA can be implemented AbstractThe efficiency and emission control of internal combustion engines have gained growing importance in recent years, particularly for small marine vessels.This study investigates the impact of adding water into the intake manifold on the performance characteristics and NO X emissions of diesel engines by employing empirical correlations.A full factorial experimental design was used to analyze the effects of engine speed (|S|), water ratio (|WR|), and load (|L|).The computational results show that introducing water into the intake air leads to a notable reduction in NO X emissions, reaching up to 48.3 percent at higher water ratios.In terms of performance, brake specific fuel consumption varies between -3.6 percent and +4.2 percent depending on the interaction between speed and water ratio.Effective efficiency changes up to ±2.1 percent, with the most significant variations observed at mid-range speeds.Engine speed emerges as the dominant factor influencing performance, while load shows limited impact.A new empirical equation is proposed to estimate NO X emissions as a function of speed, load, and water ratio, supported by statistically significant three-way ANOVA results (p