It has been demonstrated that natural gas as a fuel has the potential to produce very low exhaust emissions in vehicle applications. In addition, the widespread availability of natural gas has made it a leading alternative to conventional fuels. However, concern over the adverse health and environmental effects of air pollution has resulted in increasingly stringent vehicle emissions standards.To maintain performance specifications while meeting federal emissions regulations, closed loop operation of a lean burn, medium-duty natural gas engine is being investigated.
The current experimental setup consists of a Hercules GTA 3.7 liter, 4 cylinder, turbocharged engine which was converted from diesel operation by the redesign of the combustion chamber and intake manifold for use with compressed natural gas(CNG). A Gaseous Fuel Injection (GFI) Compuvalve® provides fuel metering and ignition control, while an Altronic high energy ignition system fires the spark plugs upon command from the Compuvalve®. A PC-based data acquisition and control system is used to gather data and provide a closed loop control link between the NGK universal exhaust gas oxygen (UEGO) sensor and the fuel metering valve.
Engine output is measured using a Mustang eddy current dynamometer. Engine exhaust is routed to a full scale dilution tunnel from which samples are supplied to Rosemount analyzers to quantify selected exhaust species.
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Several of the papers published from this research have been reprinted here with permission of the Society of Automotive Engineers (SAE). Visit their site for a wealth of transportation-related information! To view a paper, make sure you have the Adobe Acrobat Reader. |
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"Development of a Closed Loop Fuel Management System for a Lean Burn Natural Gas Engine", Clark, et al., Proceedings of the 1994 Automotive Technology Development Contractors' Coordination Meeting, SAE P-289, 1994.
"Closed Loop Engine Control for Turbocharged Lean-Burn Natural Gas Engine Operation", Mott, et al., Proceedings of the 1995 ASME Fall Technical Conference, 1995.
"Effect of Fuel Composition on the Operation of a Lean-Burn Natural Gas Engine", Clark, et al., SAE Paper 952560, 1995.
"Closed Loop Fueling Control for a Lean Burn Natural Gas Engine", Clark, et al., Proceedings of the 1996 Windsor Workshop on Alternative Fuels, 1996.
"Hydrocarbon Speciation of a Lean Burn Spark Ignited Engine", Nine, et al., SAE Paper 972971, 1997.
Presently, the effect of substituting exhaust gas recirculation(EGR) for the normal excess air of the lean burn engine is being studied. EGR has already proven useful in reducing oxides of nitrogen(NOX) in engines using a stoichiometric mixture. It is hoped that this technique will be able to reduce further the lowered emissions of the lean burn engine without a significant loss of performance. For this effort a special valve, pictured here, was constructed at WVU which provides the necessary EGR flow while permitting precise control of the flow rate.
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