Experimental and Numerical Study of Water Spray Injection at Engine-Relevant Conditions

Water spray characterization of a multi-hole injector under pressures and temperatures representative of engine-relevant conditions was investigated for naturally aspirated and boosted engine conditions. Experiments were conducted in an optically accessible pressure vessel using a high-speed Schlieren imaging to visualize the transient water spray. The experimental conditions included a range of injection pressures of 34, 68, and 102 bar and ambient temperatures of 30 - 200°C, which includes flash-boiling and non-flash-boiling conditions. Transient spray tip penetration and spray angle were characterized via image processing of raw Schlieren images using Matlab code. The CONVERGE CFD software was used to simulate the water spray obtained experimentally in the vessel. CFD parameters were tuned and validated against the experimental results of spray profile and spray tip penetration measured in the combustion vessel (CV). With the validated CFD model, water spray injection into an engine in-cylinder configuration was simulated. The CV experimental results showed that collapsing spray plumes were observed for higher temperature of the charge, showing reduced spray tip penetration. The engine CFD results showed that water injection at 90° BTDC showed better vaporization and decreased the formation of liquid wall film on piston surface, cylinder head, and cylinder wall compared with those for 60° BTDC water injection.