Semester

Summer

Date of Graduation

2010

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Mechanical and Aerospace Engineering

Committee Chair

Hailin Li

Abstract

Hydrogen (H2) has long been recognized as a carbon-free fuel having excellent combustion characteristics compared to hydrocarbon fuel. 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 (BTE), cylinder pressure, combustion process, and exhaust emissions of Oxides of Nitrogen (NOx), Particulate 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 to 1800 RPM.;The addition of H2 to a 1999 Cummins ISM370ESP engine and a 2004 Mack MP7 355E engine was shown to reduce substantially the emissions of PM, CO, and CO2. In comparison, the effect of H2 addition on the emissions of HC was relatively small. When operated at 30 to 70%, the addition of H2 (3-6.5%) enhanced the NOx emissions of the 1999 Cummins ISM370ESP engine. The emissions of NOx at 70% load increased almost linearly from 3.34 to 4.66 g/bhp-hr with the addition of 6% H2. However, the addition of H2 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 (5-6.5%) at a very narrow low load operational range (10-20%). When operated at 10% load, the addition of 6% H2 to a 1999 Cummins ISM370ESP engine reduced NOx emissions from 5.23 to 0.54 g/bhp-hr.;The improvement to the BTE has been one of the main objectives of this engine research. The addition of a relatively large amount of H2 (3-7%) at the range from 20 to 100% load improved the BTE for both engines. When operated at 70% load, the BTE improved from 41.7 to 43.6% with the addition 6% H2 for 1999 Cummins ISM370ESP. In comparison, the addition of a relatively small amount of H2 (0-2%) lowered the BTE. When operated at 70% load, the BTE slightly reduced from 41.7 to 41.3% with the addition of 1% H2 for 1999 Cummins ISM370ESP. The addition of H2 at 10% load 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 30 to 70% load. However, the addition of H2 at 10 and 15% load was shown to slightly retard the combustion phasing and lower the peak cylinder pressure.

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