Fuel spray visualization and its impingement analysis on in-cylinder surfaces in a direct-injection spark-ignition engine

Experiments are performed to investigate the effects of fuel spray on in-cylinder mixture preparation and its impingement on cylinder walls and piston top inside a direct-injection spark-ignition engine with optical access to the cylinder. Novel image processing algorithms are developed to analyze the fuel impingement quantitatively on in-cylinder surfaces. The technique is useful to optimize the fuel pressure, injection timing and the number of injections to minimize the fuel impingement on in-cylinder surfaces. E85, which represents a blend of 85% ethanol and 15% gasoline (by volume) is used in this study. Two types of fuel injectors are used; (i) low-pressure production-intent injector with fuel pressure of 3 MPa, and (ii) high-pressure production injector with fuel pressures of 5 and 10 MPa. In addition, the effects of split injection are also presented by maintaining the same amount of fuel used in single injection. It is found that the split injection is an effective way to reduce the overall fuel impingement on in-cylinder surfaces while maintaining a reasonably good air-fuel mixture in the cylinder.