Modelling of microbial fuel degradation in liquid fuels for a gas turbine engine application

• Bio-fAEG was developed to simulate microbial degradation of fuels in gas turbines.
• Hydrocarbon loss in fuels was between 0.37 mg L−1 and 1.48 mg L−1 per day.
• Initial microbial population, residence time & growth kinetics affect biodegradation.
• Bioavailable fraction of fuels was almost completely degraded within 20–60 days.

Microorganisms are important in fuel deterioration and consequently in engine performance. To assess the impact of fuel deterioration on gas turbines, a bio-mathematical model, Bio-fAEG, was developed to simulate microbial fuel degradation and estimate hydrocarbon loss. Simulation of four conventional diesel fuels and a biodiesel fuel estimated hydrocarbon loss between 0.37 mg/L per day (diesel-type fuel) and 1.48 mg/L per day (biodiesel-type fuel), with nearly complete degradation of the bioavailable fraction of the fuels within 20–60 days. Assuming biodegradation of these fuels is not impeded and conditions for growth remained constant, the Bio-fAEG model predicted that significant degradation begins in four months for a less degradable fuel and two months for a more degradable fuel. Analysis carried out with this model provides insight into cumulative biodegradation of engine fuels and the importance of microbial characteristics, initial microbial population and residence time. The integration of this model in engine performance and emission tools could provide further information on the effect of fuel degradation on engine systems. This is a first step in quantifiable assessment of microbial fuel degradation towards predictive condition monitoring in gas turbine fuels and fuel systems.