An Experimental Investigation of Exhaust Emissions of a 1999 Cummins ISM370 Diesel Engine Supplemented with H_2

摘要

Hydrogen (H_2) has long been recognized as a carbon-free energy carrier having excellent combustion characteristics suitable for application in internal combustion (IC) engines. The burning of H_2 in a compression ignition (CI) engine using a dual fuel combustion mode can obtain higher brake thermal efficiencies of the engine with a more flexible requirement of the quality and quantity of H_2 or H_2 containing syngas. Extensive researches have been conducted using small single cylinder diesel engines and light-duty multi-cylinder diesel engines with the emissions of particulate matter (PM) measured using a smoke meter and the emissions of nitric of oxide (NO_x) reported in ppm. There is recent interest in examining the effects of H_2 addition on the emissions characteristics of heavy-duty diesel engines with PM and NO_x emissions reported in g/bhp-hr. This research investigated the emission characteristics of a 1999 on-road turbocharged heavy-duty diesel engine converted to operate on a H_2-diesel dual fuel mode. The effects of the addition of H_2 and engine load on the exhaust emissions of NO_x, PM, carbon moNO_xide (CO), unburned hydrocarbon (HC), and carbon dioxide (CO_2) were explored. The engine load was varied from 10% to 100% with the addition of H_2 up to 6.5% into the intake mixture. Also, the effect of the addition of H_2 on the exhaust emissions were also investigated using the 13-mode ESC cycle with the addition of H_2 at 2% and 4% H_2, respectively. The addition of H_2 to this heavy-duty diesel engine was shown to reduce substantially the emissions of PM. However, the addition of H_2 at medium to high load was shown to increase substantially the emissions of NO_x especially when a relatively large amount of H_2 was added. In comparison, the addition of a relatively small amount of H_2 at low load was shown to have negligible effect on NO_x emissions. The substantially reduction in NO_x emissions was only observed with the addition of large amount of H_2 at low load, which was usually accompanied with deteriorated brake thermal efficiency of the diesel engine. It was evident that it was infeasible to reduce substantially the emissions of NO_x through the substitution of diesel fuel with the supplementation of high quality H_2 fuel. As expected, the addition of H_2 was shown to reduce the emissions of PM, CO and CO_2. In comparison, the addition of H_2 at low load was shown to increase slightly the exhaust emissions of HC. When operated at medium to high load, the addition of H_2 had negligible effect on the emissions of HC.