Date of Graduation
Statler College of Engineering and Mineral Resources
Mechanical and Aerospace Engineering
Nigel N. Clark.
Dual fuel pilot-injected diesel natural gas engines offer significant potential to reduce oxides of nitrogen (NOx) and particulate matter (PK emissions while maintaining diesel-like efficiency. A 1994 Navistar T444E turbocharger V-8 diesel engine was converted to dual fuel diesel and compressed natural gas (CNG). In an attempt to reduce the overall cost and complexity of conversion, the engine was left completely original, including the diesel fuel injection system. Also, for the sake of simplicity, the method of intake manifold fumigation through an IMPCO, Inc. electronic natural gas control valve was chosen to deliver the CNG. A microprocessor-based electronic control unit was developed to manage the hydraulically-actuated, electronically-controlled unit injectors (HEUI). Pilot injection parameters (start of injection, injection duration, and injection pressure) were varied along with the CNG flowrate to minimize NOx production while still considering hydrocarbon (HC), carbon dioxide (CO2) carbon monoxide (CO), and PM limits. Thermal efficiency and diesel fuel replacement ratio were noted as well. In-cylinder pressure data was collected and used to calculate run-time combustion parameters such as indicated mean effective pressure (IMEP), heat release rate (HRR) and to observe the ignition delay period. Comparative diesel and dual fuel tests were completed at intermediate load (1500 rpm, 335 N-m) and high load (1500 rpm, 580 N-m) operating conditions to determine the emissions benefits of the dual fuel conversion. Compared to diesel operation, optimized dual fuel operation at intermediate load produced a 32% decrease in NOx and a 57% decrease in PM. Dual fuel operation at high load produced a 19% decrease in NOx and a 72% decrease in PM. However, these reductions came with an increase in HC and CO emissions over standard diesel operation.
Park, Talus, "Dual fuel conversion of a direct-injection diesel engine" (1999). Graduate Theses, Dissertations, and Problem Reports. 953.