Performance Optimization of Marine Large-Bore Low-Speed Engine Based on One-Dimensional and Three-Dimensional Coupled Simulation

The marine large-bore low-speed engines face challenges such as complex testing and large computational workload. A feasible solution is to adopt a combined optimization approach using one-dimensional performance simulation and three-dimensional computational fluid dynamics (CFD) simulation. This paper utilizes a one-dimensional full-cycle simulation model of a marine large-bore low-speed engine with a complete scavenging and combustion coupling process. Combined with the Non-dominated Sorting Genetic Algorithm II (NSGA-II), it conducts multi-objective optimization based on the controlled variables such as the closing time of the exhaust valve, the injection timing, and the injection duration. Within a short period of time, it obtains the optimized boundary conditions. In the three-dimensional CFD simulation, the indicated thermal efficiency was increased by 1.139% and 1.264% respectively, and the maximum error compared with the one-dimensional simulation results was 1.33% and in the three-dimensional CFD simulation, the CO2 emissions were reduced by 2.2052% and 2.4886% respectively, with a maximum error of 1.69% compared to the one-dimensional simulation results. Ultimately, the results of the one-dimensional optimization were consistent with those of the three-dimensional CFD simulation. Moreover, the computing time required was significantly less than that of the traditional optimization based on three-dimensional CFD simulation.