Stringent legislation on exhaust emissions and economic fuel consumption have led to intensifiedefforts for the development of new strategies for fuel injection in spark ignition (SI) petrol engines. In-cylinder (direct) fuel injection is one of these strategies in which fuel is injected directly insidethe engine cylinder. In this study, direct fuel injection in an SI engine is investigated through a three-dimensional computer model for two phase flow. FLUENT software is used with appropriateboundary conditions to compute air-flow velocities for engine speeds of 1500 and 3000 rpm. Fuelspray injected inside the cylinder with a spray and of 22.7°, fuel droplets with initial diameter of 50microns at the injector tip, and initial droplet velocities for injector angles of 90° and 60° in x-zplane are used to study fuel spray distribution. Results show that the maximum air velocity is at thetip of the inlet valve. High turbulent domains on both sides of the inlet valve and a stagnantdomain below the valve face are observed. Positioning the fuel injector just above the valveshoulder with an offset angle of 30° results in a significant improvement in the fuel spraydistribution in the cylinder and reduced fuel impingement on the piston head. The abovepredictions have been verified in an experimental study by capturing the real time images of fuelspray directly injected inside the cylinder of a running engine using a fast response laser imagingsystem.Hakim A Abbass and Tariq MahmoodDepartment of Mechanical EngineeringInstitut Teknologi Brunei
