Transient operational behaviour and performance characteristics of a micro turbojet engine fuelled with titanium dioxide-doped Jet A-1 fuel

Nanoparticle-enhanced aviation fuels have attracted increasing attention as an alternative solution due to their potential to improve combustion characteristics, thermal efficiency, and operational performance in aviation propulsion systems. This study experimentally investigates the effects of titanium dioxide nanoparticle additives on the steady-state performance and transient stability of a micro turbojet engine used for unmanned aerial vehicle applications. Titanium dioxide nanoparticles with different average sizes (≈21 nm and < 100 nm) were dispersed into Jet A-1 at concentrations of 100 ppm and 200 ppm using mechanical stirring and ultrasonic homogenization. Density, viscosity, flash point, sulphur content, and chemical structure of resulting nanofuels were analysed. Engine tests were performed under seven operating regimes together with acceleration and deceleration conditions. The addition of titanium dioxide slightly increased density from 0.8183 to 0.8190 g/cm 3 and flash point from 39°C to 41°C while remaining within aviation fuel standards. At the lowest regime, specific fuel consumption decreased from 1744 g / ( k N ∙ h ) for Jet A-1 to 1676 g / ( k N ∙ h ) for the fuel blend including 200 ppm of 21 nm particles. Combustion temperature decreased by up to 30–50°C at low load and slightly increased at higher regimes, showing improved combustion behaviour. Operating line and transient analyses showed preserved steady-state stability and reduced pressure-ratio excursions for titanium dioxide-doped fuels. The results indicate that titanium dioxide nanoadditives having smaller particles are associated with improved combustion behaviour, reduced specific fuel consumption, and smoother transient response under the investigated operating conditions.