Pulsed Hydrogen Scramjet CFD Analysis

Scramjet propulsion is an advanced air-breathing propulsion concept in which combustion takes place while the incoming airflow remains predominantly supersonic. Unlike conventional gas-turbine engines, a scramjet does not rely on subsonic combustion within the combustor, resulting in very short residence time for fuel injection, penetration, mixing, ignition and heat release. Therefore, effective fuel–air mixing and flame stabilization are major challenges in the design of a scramjet combustor. A strut-based combustor introduces fuel into the supersonic airstream while also generating shock waves and a downstream wake or recirculation region. These flow structures can enhance fuel penetration and mixing and provide favourable regions for flame stabilization. However, the interaction between shocks, turbulence, fuel injection and heat release can also produce unsteady pressure and combustion behaviour. Hydrogen is considered suitable for scramjet applications because of its high chemical reactivity, high diffusivity and favourable ignition characteristics. Nevertheless, the behaviour of hydrogen injection under transient operating conditions requires further investigation. Continuous fuel injection provides an approximately steady fuel supply, whereas pulsed injection introduces controlled temporal variation in the fuel supply. Such periodic forcing may modify vortical structures, fuel penetration, mixing and heat-release behaviour. Depending on the operating condition, it may either improve mixing and combustion or generate undesirable pressure oscillations. The proposed project therefore investigates combustion instability in a strut-based scramjet combustor using pulsed hydrogen fuel injection. A continuous hydrogen-injection case will first be established as the baseline. Controlled pulsed-injection cases will then be analysed using transient CFD to determine the influence of pulse conditions on hydrogen distribution, mixing, combustion behaviour, pressure fluctuations and total-pressure loss. The study aims to identify the relationship between pulsed fuel injection and combustion instability and to establish a suitable numerical operating range for further research.