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The potential for existing small natural gas-fueled engines to meet the demands of commercial cogeneration applications was demonstrated. Six small engines, ranging in size from 6 to 35 kW electrical output, modified for operation on natural gas were evaluated for performance, durability, serviceability, and reliability through extended engine operation. Initially performance of both engines and generators was measured, followed by extended durability runs. Maintenance was performed as needed, and engine and component wear were monitored. The major barriers which limit engine durability and reliability were identified. Engine improvements were made, where possible, and evaluated for their effectiveness. Results indicate that some small gas-fueled engines can achieve 4,000-hour service intervals and 20,000-hour engine life. Engine reliability and life are largely dependent on the detailed design of the engine.

Durability of a current production rotary engine was evaluated while operating on natural gas. Through regular scheduled teardown inspections, wear data was gathered on critical engine components and used to develop component wear trends. Wear trends were used to predict the usable life of the engine before requiring a major rebuild. Preliminary results indicate apex seal wear rates and trochoid wear rates low enough to achieve 20,000 hours of engine operation. Areas requiring further durability improvement include the ignition system and optimization of the oil injection. Advanced knowledge of current engine component durability will be used to accelerate the development of novel gas fueled rotary engines currently under development in the United States.