Assessment of Water Injection in a SI Engine using a Fast Running Detailed Chemistry Based Combustion Model

Water injection is investigated for turbocharged spark ignition engines to limit knock probability and therefore enable higher engine efficiency. This work presents an integrated simulation-based optimization process to assess water injection. The fast running quasi-dimensional stochastic reactor model is coupled with tabulated chemistry to account for water effects on laminar flame speed and combustion chemistry. The increase of the compression ratio and the shift of the spark timing to earlier crank angles are most beneficial for fuel consumption. Wherefore, the limitation of the compression ratio and the shift of the retarded spark timing are better for low knock probability. Overall, the water presence shows a decrease of fuel consumption and knock probability at the same time. The application of the quasi-dimensional stochastic reactor model with tabulated chemistry reduces the computational costs and is suitable for multi-objective optimizations.