Analysis of Cylinder to Cylinder Variations in a Turbocharged Spark Ignition Engine at lean burn operations 2022-32-0044

In recent years, the improvement in the fuel efficiency and reduction in CO2 emission from internal combustion engines has been an urgent issue. The lean burn technology is one of the key technologies to improve thermal efficiency of SI engines. However, combustion stability deteriorates at lean burn operations. The reduction in cycle-to-cycle and cylinder-to-cylinder variations is one of the major issues to adapt the lean burn technique for production engines. However, the details of the causes and mechanisms for the combustion variations under the lean burn operations have not been cleared yet. The purpose of this study is to control cylinder to cylinder combustion variation. A conventional turbocharged direct injection SI engine was used as the test engine to investigate the effect of engine control parameters on the cylinder to cylinder variations. The engine speed is set at 2200 rpm and the intake pressure is set at 58, 78, 98 kPa respectively. In-cylinder pressure, intake pressure, and exhaust pressure are measured in each cylinder by the piezoelectric and piezo-resistive pressure transducers. The ignition timing and fuel injection timing is varied as experimental parameters to investigate the effects of the combustion phase and the fuel distribution on combustion stability. At 78 kPa condition, it was seen that the tendency of COV of IMEP was slightly different in each cylinder Also, it was seen a few cycles of sudden decline IMEP in the third cylinder at lean burn operation. So, COV of IMEP was different in each cylinder and COV of IMEP of first cylinder lower than the third cylinder. Moreover, combustion phase was different in each cylinder when ignition timing was same. Therefore, it is considered that optimized ignition timing and fuel injection timing is different in each cylinder.