Studies of a Split Injection Strategy in a Gasoline Engine via High-Speed Particle Image Velocimetry

摘要

An ongoing challenge with Gasoline engines is achieving rapid activation of the three-way catalyst during cold starts in order to minimize pollutant emissions. Retarded combustion is an effective way in achieving rapid light-up of the three-way catalyst and can be facilitated by stratified charge using late fuel injection. This, however, provides insufficient time for fuel entrainment with air, resulting in locally fuel-rich diffusion combustion. Employing a split injection strategy can help tackle these issues. The effects of a split injection strategy, using a high-pressure Solenoid injector, on the in-cylinder charge formation are investigated in the current study. The studies are performed inside an optical Gasoline engine using high-speed particle image velocimetry (PIV) in the central tumble and Omega tumble planes, by means of a high-speed laser and camera operating at a repetition rate of 10 kHz. The engine's operating conditions were representative of a low-load operation. The results revealed that a small split ratio of 1:3, with both injections in the intake stroke, was effective at generating a flow field with high turbulence levels close to the spark plug when compared to the 3:1 split ratio. The injection coupled with intake valve opening(IVO) generated strong tumble charge motion, which was preserved throughout the compression stroke. This provides favorable conditions for fast flame propagation. The fuel injection timings that maximized interactions with the piston's surface were detrimental for mixture formation due to heavy surface impingement. The findings from the study helped determine the optimum split injection properties that can generate a turbulent flow field towards the end of the compression stroke.