Computational study of diesel injection strategies for methane-diesel dual fuel engine

Methane-diesel dual fuel engine is an effective solution for partial replacement of conventional diesel fuel and pollutant reduction in compression ignition engine. However, it has several challenges from the large scale market acceptability perspective such as low combustion and thermal efficiency and high hydrocarbon (HC) and carbon monoxide (CO) emission. These problems can be addressed with the optimization of injection strategies of diesel fuel. The present work explores the effect of diesel injection strategies on combustion, performance and emission characteristics of methane-diesel dual fuel engine. Firstly, injection timing of diesel fuel is varied for single injection case. After that split injection strategy is explored with varying pilot mass amount (15%, 30% and 45%) and varying pilot injection timing (12°bTDC to 30°bTDC) at fixed main fuel injection timing (8°bTDC). The results revealed that 8°bTDC injection timing is obtained as optimum injection timing for single injection case for methane-diesel dual fuel engine from enhanced performance, combustion and reduced emissions point of view. In case of split injection, advancement of pilot injection (SOI1) timing till 24°bTDC decreased the methane slip, HC and CO emissions. SOI1 timing earlier to 24°bTDC increased the methane slip, HC and CO emissions for all pilot mass injections (15, 30 and 45%). Higher pilot mass injection resulted in higher methane slip, HC and CO emission in SOI1 range of 24–30°bTDC. SOI1 timing exhibited different trends of soot and NO_x emission with different pilot mass injection. GTE reduced with advanced SOI1 injection timing. Overall, with split injection technique, 24°bTDC is optimum pilot injection (SOI1) timing, and 15% pilot mass amount is optimum amount and 8°bTDC is optimum main injection (SOI) timing for methane-diesel dual fuel engine.