The PhD topic focuses the attention on the internal flow path analysis of a hypersonic demonstrator equipped with a scramjet engine, which will fly in a 10-second experimental operation. The work is part of a project funded both by the national program PRORA, and ASI, by means of an agreement between CIRA and ASI on hypersonics. The combustion is non-premixed and the fuel chosen is hydrogen which is injected by multistage strategy in two different stages. Engine performance and parameters such as combustion efficiency are analyzed through nose-to-tail CFD analysis both in fuel-off and fuel-on conditions. An important result is the achievement of a high combustion efficiency by the conclusion of the engine cycle with stochiometric hypotheses and single step reaction. Future studies will examine the performance of the scramjet using more detailed chemical models and varying the injection strategy while also evaluating the effect of the air-fuel ratio. Finally, the numerical results will be possibly validated with experimental measurements.