Fuel Control and Spark Optimization of a Propane Fuel System for an Engine-Generator System

As climate change drives the exploration into new and alternative fuels, biodiesel has emerged as a promising alternative to traditional diesel fuel. To further increase the viability of biodiesel, a unique system at the University of Kansas utilizes glycerin, the primary byproduct of biodiesel production, for power generation. This system converts glycerin into a hydrogen-rich gas (syngas) that is sent to an engine-generator system in one continuous flow process. The current setup allows for running the engine-generator system on pure propane, reformed propane, or reformed glycerin, with each fuel serving a unique purpose. This paper discusses upgrades in pure propane operation that serves the intent of preheating the engine prior to syngas operation and establishing the baseline energy requirement for fueling the system. The current upgrade to the fuel system incorporates an Electric Fuel Valve (EFV) as a replacement for a gaseous propane carburetor, providing the ability for Air-to-Fuel Ratio (AFR) adjustment of the engine at different generator loads. The use of EFV in a continuous fuel additive manner provides a solution to the carburetor’s inherent disadvantage: maintaining a constant AFR. Hence, this upgrade allows the system to adjust more accurately to different engine operating conditions and other unique fuels to be potentially tested (e.g., natural gas and biogas). Moreover, spark timing optimization accompanies the new fuel control in order to enhance engine performance and maximize fuel economy. Finally, in-cylinder pressure traces and associated performance parameters are reviewed and discussed in order to analyze the operation of the new EFV-based system.