Dynamic NOx Control and Statistical Robustness Assessment of Marine Diesel Engines Under Cyclic Loading

Abstract

In marine Diesel Engines, Selective Catalytic Reduction (SCR) is a primary technique to achieve IMO Tier III Nitric Oxide (NO_x) compliance, but dynamic engine-out variability, temperature sensitivity, transport delay, and oxygen normalization effects are introduced that steady-state analyses fail to capture due to the transient marine propulsion process. The study conducted various analyses, including time-domain, cross-correlation, Power spectral density (PSD) analysis, and thermal regression, while statistically applying time-resolved correction to 16% O₂, deterministic sensitivity mapping, and Monte Carlo uncertainty. The analysis results showed that a sustainable NOx reduction of approximately 79–80% is achieved with pre- and post-SCR concentrations fluctuating between 15–32 ppm and 3–7 ppm, respectively, and a transport delay of 8 seconds was quantified between upstream and downstream NO_x signals. PSD revealed substantial attenuation of highfrequency components. This integrated dynamic and statistical analysis conducted an advanced SCR evaluation toward a system-level transient characterization.