Injection Strategies for Operational Improvement of Diesel Dual Fuel Engines under Low Load Conditions

Diesel Dual Fuel (DDF) operation is a promising alternative engine operating mode. Previous research studies have reported a DDF engine operating under low load conditions suffers from high HC emissions, mostly Methane. The current study investigated the use of a multiple direct injection strategy for improvement of low-load DDF operation in a commonrail direct injection single-cylinder diesel engine. Natural gas was supplied at 70% of energy replacement ratio.

Results indicated that depending on engine conditions, a double-pulse injection had potential for combustion control and provided an effective way to reduce NO_x and methane emissions. Moreover, the double-pulse injection helped improve the combustion stability, reduce the pressure rise rate, and decrease the maximum cylinder pressure, compared to DDF operation with a single pulse injection. Under low load conditions, the tuned injection strategies demonstrated significant operational improvement comparing with a simple DDF conversion that used the same injection timings as that of conventional diesel operations.