Effect of Injection Timing, Premixed Equivalence Ratio and EGR on Combustion Characteristics of an HCCI-DI Combustion Engine Using In-Cylinder Dual Injection Strategy

A single cylinder direct injection (DI) diesel engine is modified to run in HCCI-DI mode using a novel in-cylinder dual injection strategy. In this present investigation effect of 2^nd injection timing, premixed equivalence ratio and exhaust gas recirculation (EGR) on combustion and emission behavior is studied. Based on the characteristics of combustion, performance and emission behavior, 2^nd injection timing is optimized at a constant split ratio (80%) and engine speed (1500 rev/min). Premixed equivalence ratio was varied (up to 0.38) at the optimized 2^nd injection timing condition. It is identified that 2^nd injection timing and premixed equivalence ratio play an important role in controlling the occurrences of all combustion parameters of HCCI-DI combustion. EGR was introduced in the cylinder to understand its effect on various combustion parameters and emission behavior. External cooled EGR showed a promising way of suppressing peak cylinder pressure (PCP) and peak pressure rise rate (PRR). EGR also retards all combustion parameters which in turn help in extending the load range of HCCI-DI combustion.