Aging analysis of alternative fuels and biofuels in a novel test rig

Abstract

Understanding aging phenomena of alternative fuels, such as fatty acid methyl esters (FAME), hydrogenated vegetable oil, or synthetic power-to-X products, has become a highly active research field since their introduction led to different aging-related phenomena. More alternative fuels lead to ever more fuel blend varieties that all need to undergo a usability assessment, implying plenty fuel aging experiments. Laboratory tests usually artificially age fuels at high temperatures to examine aging products. However, in this work, a novel test rig was designed to closely simulate the conditions encountered in practice. This way, knowledge gain and innovation can be achieved for fuel aging and concerning hardware and additive technology to decrease deposit buildup. Results from pure FAME revealed a discrepancy, in which it failed conventional fuel aging tests but performed well in this realistic setup due to the fuel's high polarity preventing deposit accumulation. Among the standardized fuel tests, thermal, spectroscopic, and chromatographic techniques used in this work, benchtop 1H Nuclear Magnetic Resonance (NMR) spectroscopy delivered insightful information with minimal effort and sample volume. The examined deposits mainly consist of (oxidized) FAME species (≈70%) interacting with aromatic compounds (≈5.5%). Moreover, only blends of conventional fuel and FAME lead to system failures and large quantities of deposits.