Design optimisation of axisymmetric scramjets for access-to-space

Shape optimisation of an axisymmetric scramjet has been performed for two operating conditions at Mach 8 and 12, aiming at the application of hypersonic airbreathing propulsion for efficient access-to-space. The scramjet geometry, which is represented by a set of design variables, has been optimised for a single objective, namely maximum net thrust, by means of an advanced design optimisation capability based on evolutionary algorithms coupled with a CFD (computational fluid dynamics) solver for inviscid flowfields with premixed fuel (hydrogen) and air. Considerable improvement of the engine efficiency has been achieved by optimisation in both operating conditions, owing to cooperative contributions from respective scramjet components. The robustness of the optimised geometries has been demonstrated by cross-evaluating the performance of the optimum shapes under off-design operating conditions.