Date of Graduation


Document Type


Degree Type



Statler College of Engineering and Mineral Resources


Mechanical and Aerospace Engineering

Committee Chair

Derek Johnson

Committee Co-Chair

Andrew Nix

Committee Member

Gregory Thompson


In the natural gas industry, approximately 27 million horsepower is used for transmission and storage, necessary to transport natural gas to its respective destinations. Engine technologies in operation dating back to the 1940's are still in use today. Within this array of prime-movers, exist compressors powered by large bore 2-stroke, lean-burn, natural gas engines. Reduction of exhaust emissions without negative impacts on engine performance is the main focus for operators. Research regarding engine fuel delivery, ignition techniques, and post-combustion techniques show potential improvements in engine performance and exhaust emissions. However, research pertaining to spark plug design and exhaust gas recirculation on this class of engines is limited. The goal of this study was to examine the effects, of such parameters, on engine performance and exhaust gas emissions. The test platform was a single cylinder AJAX E-42 engine, common to the natural gas gathering and compression sector. The engine was operated at 525 RPM and 400 ft. -- lbs. of torque for all test scenarios. The spark plug type recommended by the engine manufacture was analyzed to determine engine performance and exhaust gas emissions. Four additional spark plug configurations were examined for their effects engine performance and exhaust gas emissions and compared to those of the manufacture specified spark plug. The effects of ignition timing were also examined for increased efficiency and improved exhaust emissions for each spark plug configuration. Reductions of 32% for CO and 89% for VOCs were found for a fine center electrode side-gap style spark plug compared to a conventional j-gap center electrode style. The spark plug configuration with the highest performance, based on fuel consumption and emissions, was examined with the effect of EGR. Increases in engine stability and fuel economy of 15% were found, in addition to reductions in NOx formation up to 16%. Formaldehyde formation was also reduced up to 3%, the magnitude of all improvements varied depending on ignition timing and EGR level.