An optical investigation of dual fuel and RCCI pilot ignition in a medium speed engine

Driven by the Paris agreement and tightening IMO regulations, marine sector is focusing on lowering engine emissions moving to low-carbon fossil or renewable fuel such as methane. The dual-fuel concept allows usage of methane main energy-source in diesel engines. A small pilot injection acts an ignition source for premixed It was investigated how NOx formation, mainly taking place during combustion fuel, could be minimized. To better understand process a engines, optical research has been performed medium speed dual engine. unique Bowditch 200 mm single cylinder setup enabled high recordings natural luminescence. Both Reactivity Controlled Compression Ignition (RCCI) Conventional Dual Fuel (CDF) investigated. RCCI created early injection, allowing long mixing time. CDF cases had late timing. In operation higher degree premixing recognized luminescence starting further away from injector, at varying location. diluted generated limited brightness. heat release profile Gaussian/bell-shaped, without typical peak. recorded images show that follows shape injector jet. showing strong initial peak, resembling peak known conventional combustion. This combustion, correlated emissions, absent mode.