Performance and emissions of a heavy-duty diesel engine fuelled with diesel and LNG (liquid natural gas)

This paper presents the effects of liquid natural gas on a heavy-duty diesel engine. Natural gas was used as primary fuel, while a pilot amount of diesel was used as an ignition source. The amount of each fuel was adjusted to obtain comparable brake torque and power output from the dual engine operation, while no knocking was observed. The engine performance and emissions from the diesel and dual fuel engine tests were conducted over the engine speed range between 1100 and 1900 rpm. The engine performance included torque, power, specific fuel consumption (SFC), volume efficiency, and thermal efficiency. The emissions tested were total hydrocarbon (THC), nitrogen oxides (NO_x), carbon dioxide (CO₂) and carbon monoxide (CO) emissions. The results showed that the maximum portion of natural gas in the dual fuel engine operation was up to 77.90% at 1300 rpm. Compared to the diesel operation, the dual fuel operation showed less specific fuel consumption, thermal efficiency, and volumetric efficiency. The emissions of THC and CO from the dual fuel engine operation were higher, while the emissions of NO_x and CO₂ were lower.