Enhancement of the precooling system performance for aviation engines by volatile liquid injection

Water injection precooling in aviation engines is a promising technique that can enhance performance, improve efficiency, and reduce emissions, especially at high altitudes and Mach numbers. However, its implementation in aviation engines requires careful engineering and design considerations due to the restricted space available for installation and operation, as well as the challenges posed by high inlet air velocities. Therefore, the present study experimentally and numerically evaluates the effectiveness of spray precooling for jet engines and introduces novel insights into optimizing droplet dynamics and nozzle configurations in short, narrow spray ducts under high inlet air temperature and velocity. The impact of water spray cooling on the uniformity of inlet air is also investigated for nonuniform air temperature conditions, which has yet to be mentioned in previous research. An experimental configuration has been devised and implemented to investigate water injection precooling within a rectangular spray duct. The evaporative cooling process through the spray duct and the injected droplet trajectories were predicted using an Eulerian-Lagrangian computational fluid dynamics (CFD) model. The CFD model was verified using the present experiments, and there is a strong correlation between the experimental data and simulation findings, with an average discrepancy of less than 7%. The effectiveness of the water injection system is investigated at different operating parameters such as nozzle arrangements, coolant type, droplet size, and variable velocities. The results showed that sprays characterized by small mean diameters and high initial droplet velocity significantly enhance spray cooling performance. Changing the nozzle configurations impacts spray cooling performance considerably, with the cross-outside case providing the best results. Notwithstanding its advantageous evaporation rate, introducing methanol via injection does not yield significant enhancements. Water injection is crucial in achieving a more homogeneous temperature distribution by reducing temperature disparities and promoting mixing and evaporation.