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Effects of Water-Enriched Intake Air on Performance and NOx Emissions of Small Marine Diesel Engines: A Full Factorial Analysis
Mustafa Tuti, Abdullah Türk, Murat ÖzkökDepartment of Naval Architecture and Marine Engineering, Karadeniz Technical University, Trabzon, TurkeyThe efficiency and emission control of internal combustion engines have become increasingly important in recent years. In this context, the present study examines the effects of adding water into the intake manifold on the performance characteristics and NOx emissions of diesel engines used in small marine vessels by employing empirical correlations. A full factorial design of experiments was applied to systematically analyze the influence of engine speed (|S|), water ratio (|WR|), and load (|L|).
The computational results demonstrate that introducing water into the intake air leads to a substantial reduction in NOx emissions, achieving up to 48.3% decrease at higher water ratios. In terms of performance parameters, the brake specific fuel consumption (BSFC) shows a variation of –3.6% to +4.2%, depending on the interaction between speed and water ratio. Additionally, effective efficiency (EE) exhibits changes of up to ±2.1%, with the most notable effects observed at mid-range speeds. Among the factors examined, engine speed is identified as the most influential parameter affecting performance, while load exhibits minimal impact.
Furthermore, a new empirical formula is proposed to estimate NOx emissions as a function of speed, load, and water ratio, showing strong statistical significance supported by three-way ANOVA analyses (p < 0.05). Interaction plots confirm that higher water ratios combined with lower engine speeds result in the largest NOx reduction without severely compromising performance.
In summary, this preliminary study provides quantitative insights into the potential of water-assisted intake air strategies to optimize engine behavior and mitigate NOx emissions in small marine vessels, thereby offering a scientific basis for future experimental research in this field.
Manuscript Language: English