Effects of diesel injector nozzle angle and split diesel injection strategy on combustion and emission characteristics of an ammonia/diesel dual-fuel engine

Pre-injection can effectively improve combustion and thermal efficiency while reducing unburned ammonia (uNH3) and N2O emissions in ammonia/diesel dual-fuel engines. Nevertheless, the pre-injected diesel often impacts the cylinder liner or piston pinch area, adversely affecting combustion and emissions. In this study, various narrow injector nozzle angles (90°/60°) of diesel fuel are applied on investigating engine performance and emissions. Experiments are conducted at 1200 r/min, IMEP 1.2 MPa, and AEF (ammonia energy fraction) 50 %, consisting of varying INA (injector nozzle angle) of 145°/90°/60°, PIR (pre-injection ratio) from 20 %–80 %, PIT (pre-injection timing) from −70 °CA ATDC to −30 °CA ATDC, and sweeping MIT (main injection timing). Results show that larger INA prefer a lower PIR and delayed PIT to reduce the pre-injected fuel hitting the liner, and smaller INA prefer a higher PIR to reduce the main-injected fuel hitting the piston wall. ITE of INA145° peaks at a moderate PIR and delayed PIT while ITE of INA90° and INA60° peaks at a high PIR and early PIT. Decreasing INA combined with high PIR and early PIT helps to reduce uNH3, N2O, and GHG emissions, at the cost of a slight decrease in ITE.