Study the ship engine speed limiter effect with testbed experiment and on-board measurement, and comparative analysis with testbed propeller cycle responses

Transient ship manoeuvring introduces coupled speed-load dynamics that are inadequately represented by conventional propeller-law-based load models. This study examines the impact of engine speed-slope limiters (r min⁻ 1 s⁻ 1 ) on transient load tracking, fuel consumption, and emissions using a combined experimental and analytical approach. Experiments were conducted on a six-cylinder turbocharged marine diesel engine, and complemented with reanalysed on-board measurements from (i) a tanker and (ii) a cargo vessel, classified according to equivalent acceleration regimes. Testbed results show that low acceleration rates (≈ 4–22 r min⁻ 1 s⁻ 1 ) enable near-complete load tracking (≈ 92–100% of full load), whereas higher rates (up to 260 r min⁻ 1 s⁻ 1 ) reduce load attainment to ∼ 56% of full load, indicating pronounced transient load lag. This lag leads to increased brake specific fuel consumption (BSFC), particularly at low loads. Emission characteristics are strongly dependent on acceleration severity: rapid transients increase PM 1 and particle number emissions, while slower rates lead to higher NO x due to improved load realisation. On-board data from the cargo ship demonstrate substantial variability under comparable loads, with NO x ranging from ∼ 30 to 44 g kg⁻ 1 fuel and CO from ∼ 10 to 30 g kg⁻ 1 fuel and elevated emissions. Constant-speed operation reduces NO x but increases CO (up to ∼ 25 g kg⁻ 1 fuel), PM 1 (up to ∼ 2.5 g kg⁻ 1 fuel), and particle number (up to ∼ 3 × 10 1 ⁶ # kg⁻ 1 fuel). Comparison with propeller-law-based modelling demonstrates that load-only approaches fail to capture transient emission variability, particularly under low-load and manoeuvring conditions. Integration of a control-based acceleration framework with both testbed experiments and real-world ship emission data results in highlighting the importance of incorporating speed change rate (r min⁻ 1 s⁻ 1 ) effects into marine engine modelling and control strategies for improved emission prediction and optimisation.