Hydrogen is seen as one of the important energy carriers of the future with potential to reduce local as well as global
warming. The main by-product of the combustion of hydrogen in air is water vapor and trace quantities of oxides
of nitrogen. An experiment was conducted to study the impact of hydrogen/natural gas blends on performance,
thermodynamic efficiency and exhaust gas emissions in a reciprocating four stroke cycle engine. For this purpose a
four-stroke, 4.2 L, V-6 naturally aspirated natural gas engine was used. This engine was coupled to an eddy current
wet type dynamometer. First, the engine was tested with natural gas to develop a baseline for comparison with
hydrogen/natural gas fuel blends. A test matrix was used to that included variation of engine load and air-to-fuel
ratio. The engine was tested at throttle openings of 50% and 100% and equivalence ratios of 1.0 (stoichiometric)
and 0.9 (lean) for hydrogen percentages of 10%, 20% and 30% by volume. The test results showed a reduction in
NOx and CO for most of the cases. The engine power and torque slightly decreased when the hydrogen concentration
was increased. This paper fully describes the test setup, the test matrix, and the test procedures. The results are fully
analyzed and presented to illustrate the impact of hydrogen-enhanced natural gas fuel blends on engine performance
and emissions.