AN INVESTIGATION OF HYDROGEN SUPPLEMENTATION ON COMBUSTION AND EMISSIONS OF HEAVY-DUTY DIESEL ENGINES

ABSTRACT
Hydrogen (H2) has long been recognized as a carbon-free fuel having excellent combustion characteristics suitable for application in internal combustion (IC) engines. This research investigated the effects of H2 addition on the performance, combustion, and emission characteristics of two turbocharged heavy-duty diesel engines. The effects of H2 addition, engine load, engine speed, and diesel fuel flow rate on the brake thermal efficiency, cylinder pressure, combustion process, and exhaust emissions of Nitrogen Oxide (NOx), Particular Matter (PM), Carbon Monoxide (CO), Unburned Hydrocarbon (HC), and Carbon Dioxide (CO2) were explored. The engine load was varied from 10% to 100% with H2 concentration in the intake mixture (H2/(H2+Air), vol.) varied from 0 to 7.5%. Engine speed was varied from 1200 rpm to 1800 rpm.
The addition of H2 to a 1999 Cummins ISM370 engine and a 2004 Mack MP7 355E engine was shown to reduce substantially the emissions of PM, CO and CO2. When operated at medium to high load, addition of H2 enhanced the NOx emissions of the 1999 Cummins ISM370 engine but had mild effect on the NOx emissions of the 2004 Mack MP7 355E. The substantial reduction of NOx emissions was only observed with the addition of relatively large amounts of H2 at a very narrow low load operational range. In comparison, the effect of H2 addition on the emissions of HC was relatively small.
The improvement to the brake thermal efficiency has been one of the main objectives of engine research. The addition of a relatively large amount of H2 at medium and high load improved the brake thermal efficiency of both engines. In comparison, the addition of a relatively small amount of H2 lowered the brake thermal efficiency. The addition of H2 at low load (10%) was found to reduce the brake thermal efficiency for the range of data measured. The combustion analysis demonstrated the significant effect of H2 addition in enhancing the heat release process and increasing the peak cylinder pressure when operated at medium to high load. However, the addition of H2 at low load was shown to slightly retard the combustion phasing and lower the peak cylinder pressure.
Research Advisor: Dr. Hailin Li
Committee Members: Dr. Nigel Clark and Dr. Benjamin Shade

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