Effect of flexible camshaft technology on dual-fuel engine performance using phenomenological combustion model

The objective of the current study is to investigate the effect of tunable valve timings on the performance and emissions of a dual-fuel marine engine. A simulation model was developed in MATLAB to simulate the valvetrain mechanism. The model generates different valve lift curves depending on the input conditions, and after that, it tests them against any possible collision with the piston. The valid valve lift curves were exported to a two-zone combustion model in AVL CRUISE-M platform. The combustion model depends on the fractal principle and aims to predict the in-cylinder parameters. In addition, it contains sub-models to calculate the ignition delay and emissions formation. Model results were compared against experimental data, as the latter were obtained from a heavy-duty, medium-speed, single-cylinder research engine, which employs natural gas as a main fuel. The results showed good agreement and the model was used for further investigations with other cam pairs. It has been found that the fractal combustion model can effectively represent the combustion behavior in the dual-fuel engine. Furthermore, valve timing has a significant influence on the engine performance and exhaust emissions. Results also revealed that applying Miller cycle can reduce the nitrogen oxides emissions, while the higher valve overlap period had a negative effect on methane slip.