Pusat Pengajian Kejuruteraan Aeroangkasa - Tesis

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Browsing Pusat Pengajian Kejuruteraan Aeroangkasa - Tesis by Author "Fu, Wei"

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    Experimental and numerical study of Fuel mixing mechanism for Scramjet Engines.
    (2026-07)
    Fu, Wei
    Hydrocarbon-fuelled scramjets demand highly efficient fuel-air mixing within extremely short flow residence times. However, the breakup and mixing behaviour of liquid kerosene injected into a supersonic crossflow remains complex because of strong aerodynamic shear, shock interactions, and rapid atomisation. This thesis addressed the lack of experimental visualisation and validated numerical modelling of kerosene jet injection into a Mach 2 crossflow, with particular focus on breakup stages, penetration behaviour, and the influence of geometric and aerodynamic parameters. An integrated methodology combining high-speed shadowgraph and schlieren imaging with a Detached-Eddy Simulation coupled to a Discrete Phase Model, using a Kelvin-Helmholtz/Rayleigh-Taylor breakup formulation, was developed to characterise the coupled gas-liquid dynamics. The experimental diagnostics captured bow-shock formation, surface-wave development, jet bending, rapid atomisation, and a downstream transition toward uniform atomisation. The numerical model reproduced the same dominant flow structures observed experimentally and additionally provided pressure, density, vorticity, and velocity field information that could not be measured directly, while exhibiting trends consistent with the experimental observations. Quantitatively, increasing the liquid-gas dynamic pressure ratio raised the jet penetration height by approximately 40% across the tested range, while reducing the nozzle diameter from 0.38 mm to 0.3 mm decreased the mean Sauter Mean Diameter (SMD) by approximately 25% and shifted atomisation toward a finer, more uniform spray. Comparison between experimentally measured penetration trajectories and the xxiv numerical predictions showed agreement within ±5%, confirming the fidelity of the integrated experimental-computational framework. The findings demonstrated that nozzle diameter and liquid-to-gas dynamic pressure ratio exert strong effects on jet penetration, breakup mode, flow-field structure, and atomisation pattern. Larger nozzles produced thicker jet columns and stronger near-field blockage, whereas smaller nozzles accelerated deformation and yielded finer atomisation. Variations in the dynamic pressure ratio also affected jet deflection, the extent of the surface-wave zone, and the intensity of shock interactions. Overall, this work advances the understanding of kerosene jet breakup and mixing in supersonic crossflow and establishes a validated experimental-computational basis for refining fuel-injection strategies in hydrocarbon-fuelled scramjet combustion systems.