Experimental and Numerical Study of Water Injection under Gasoline Direct Injection Engine Relevant Conditions 2023-01-0313

Water injection has been used to reduce the charge temperature and mitigate knocking due to its higher latent heat of vaporization compared to gasoline fuel. When water is injected into the intake manifold or into the cylinder, it evaporates by absorbing heat energy from the surrounding and results in charge cooling. However, the effect of detailed evaporation process on the combustion characteristics under gasoline direct injection relevant conditions still needs to be investigated. Therefore, spray study was firstly conducted using a multi-hole injector by injecting pure water and water-methanol mixture into constant volume combustion chamber (CVCC) at naturally aspirated and boosted engine conditions. The target water-fuel ratio was fixed at 0.5. Mie-scattering and schlieren images of sprays were analyzed to study spray characteristics, and evaluate the amount of water vaporization. The qualitative analysis of the water and water-methanol sprays demonstrated the inability of water to evaporate completely. Moreover, simulations of water spray injection were also performed under the framework of CONVERGE using the Eulerian-Lagrangian modeling approach. The amount of vaporized water, evaporation rate, temperature evolution, saturation ratio was analyzed and compared under different crank angles. The presented simulation scheme will provide informative support for the future design of water injection pattern in internal combustion engines.