Comparative Assessment and Parametric Optimisation of Large Marine Two-Stroke Engines with Exhaust Gas Recirculation and Alternative Turbocharging Systems

Abstract

Although the exhaust gas recirculation (EGR) technology has been proven effective to decrease the marine engine’s nitrogen oxides (NOx) emissions, it is associated with a considerable fuel consumption increase and challenges to the engine–turbocharger matching. This study aims to parametrically optimise the EGR and turbocharging system settings of a large marine two-stroke engine with the objective of obtaining the highest engine efficiency whilst ensuring compliance with the prevailing NOx emissions limits. Two typical configurations of the investigated engine (baseline and alternative) are modelled in the GT-SUITE software. Parametric simulations are performed with EGR rates up to 40% along with cylinder bypass rates up to 50%, and the simulation results are analysed to quantify the impact of the engine operation with EGR on the performance and NOx emissions parameters. For the baseline engine configuration, the EGR rate increase considerably deteriorates the brake specific fuel consumption (BSFC), which is attenuated by opening the cylinder bypass valve. The optimal combinations of the EGR and cylinder bypass rates for each operating point are identified for both configurations. Following the comparative assessment between the two engine configurations, recommendations for the engine operating modes are proposed, leading to BSFC improvement in the region of 0.7 to 2.9 g/kWh. This study provides insights for the operational settings optimisation of two-stroke engines equipped with EGR systems, contributing towards the reduction of the associated environmental carbon footprint.

The future of ship engines: Renewable fuels and enabling technologies for decarbonization

“…Advanced turbocharging systems are 93 optimized for large (24.4 MW), two-stroke marine diesel engines and a two-stage turbocharging sequential ratio (30:70) using various rates of EGR and cylinder bypass. 97 A comparative assessment between the two engine configurations shows BSFC improvements in the region of 0.7-2.9 g/kWh.…”

Design and Implementation of a Linear Active Disturbance Rejection Control-Based Position Servo Control System of an Electromotive Valve for Exhaust Gas Recirculation

“…(3) When the engine is under a low load, especially when idle, the introduction of exhaust gas will cause unstable combustion or even lead to misfiring. Therefore, the EGR rate should be dynamically adjusted according to the temperature and load state of the engine to find the optimal solution between optimal engine performance and NOx emission [ 5 , 6 , 7 , 8 ]. Moreover, to reduce the complexity of the engine multi-parameter tuning process, the EGR valve’s own position servo control is decoupled from the exhaust gas intake demand control under the engine multi-parameter operating parameters.…”