Assessing the Effectiveness of Terpenes as Blending Agents in a Diesel Engine

Abstract The pursuit of sustainable fuel alternatives with favorable physicochemical characteristics, cost-effective large-scale production, reliance on accessible feedstocks, and compatibility with current infrastructure is critical for mitigating global carbon emissions. Even under the most optimistic scenarios for future energy systems, liquid fuels are expected to remain essential due to their superior energy density, ease of storage and transport, and adaptability across diverse applications. Terpenes, a broad class of hydrocarbon molecules derived from plant biomass and microbial processes, are fundamentally composed of isoprene (C5H8) units and categorized into monoterpenes (C10), sesquiterpenes (C15), and diterpenes (C20). Their structural variations in carbon chain length, functional groups, and bond configurations influence their combustion properties and engine compatibility. By employing artificial neural network-based predictive modeling, several terpenes are identified as promising alternative fuels. Three terpene-based fuels—farnesene (mixed isomers), sabinene/β-pinene, and bisabolene (mixed isomers)—were subsequently acquired for experimental testing. Combustion and emissions testing was conducted on a Kohler KD440 single-cylinder diesel engine in a generator configuration. The findings suggest that terpenes can serve as viable substitutes for conventional fossil fuels without substantial compromises in engine performance in terms of combustion dynamics and emissions.