THE EFFECTS OF HYDROGEN ADDITION ON A SPARK-IGNITED COMPRESSED NATURAL GAS VEHICLE

Open Access
Author:
Clark, Jamie Michael
Graduate Program:
Energy and Geo-Environmental Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
April 04, 2008
Committee Members:
  • Andre Louis Boehman, Thesis Advisor
Keywords:
  • engine testing
  • combustion
  • HCNG
  • chassis dynamomter
Abstract:
The “Freedom Car” Initiative enacted by the Bush Administration has placed significant emphasis on the development of a hydrogen economy in the United States. While hydrogen fuel-cell vehicles have been the focus of recent media attention, near term implementation of hydrogen as a combustion enhancer is a more reliable pathway for wide-scale hydrogen utilization within the next ten years. Through combustion analysis, hydrogen addition to natural gas has shown to increase thermal efficiency and reduce CO, NO and hydrocarbon emissions (UHC) in studies on stationary test cell engines. On-road vehicle studies testing hydrogen-natural gas blends show emissions benefits and increase in fuel economy. However, on-road tests lack exhaustive combustion analysis to explain what is occurring in the cylinder. In this study, the effect of a 33 percent volumetric blend of hydrogen (HCNG) on natural gas combustion was investigated in a 5.4L spark-ignited engine in a Ford E-250 van. In-cylinder combustion analyses were performed and untreated exhaust emissions were measured at 15 and 30 mph with road loads of 10, 20 and 30 horsepower. Hydrogen increased the flame speed reducing time for flame kernel development and combustion duration. However, the hotter burn lost more heat to the surroundings and thermal efficiency of HCNG was lower than natural gas. Increasing engine speeds magnified reduction in combustion duration created by hydrogen. As load on the engine increased, hydrogen-influenced reduction on burn time was reduced. Heat and throttling losses reduced the thermal efficiency of the combustion. More complete combustion with hydrogen reduced carbon-based emissions and bulk cylinder temperature increase drove increased NO formation.