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Controlling exhaust gas temperature in a dual-stage catalyst system improves by a factor of three (or more) its capability to tolerate air-fuel ratio (AFR) variability and maintain compliance with stationary engine emission standards enforced in CA. This system is ideally suited for combined heat and power (CHP) generating units, in which heat is intentionally extracted from the engine exhaust gases to improve overall system thermal efficiency. Engines fueled with low-pressure natural gas typically employ fumigation fuel delivery systems. When operated at stoichiometric AFR using typical feedback fuel metering strategies and a three-way catalyst (TWC), these systems cannot reliably achieve the fuel control precision required to satisfy stringent emission requirements. Small rich or lean deviations in AFR result in large increases in tailpipe CO (rich) or NOx (lean). In the 1980's, automobile OEMs employed dual-stage catalyst systems to address a similar issue.

A production hybrid-electric vehicle with gasoline internal combustion engine (ICE) has been modified to operate on hydrogen fuel and to demonstrate an advanced metal hydride fuel storage system. Fuel economy, range, performance, and emissions of the modified vehicle are similar to levels achieved with current fuel cell vehicles. This project was conceived and executed by Energy Conversion Devices, Inc. All vehicle modifications, engine and chassis dynamometer tests, and road tests were performed by Quantum Technologies, Inc. at their Lake Forest, CA facility. Project activities and test results are chronicled in this paper.