S & C Thermofluids Ltd worked on a CDE project for thrust efficiency.

Steady flow thrust augmentation was observed to increase static thrust by 50%. The concept of this increases volume and weight of the package and therefore any advantages are nullified at even modest flight speeds.

Unsteady jet flow augmentation can be achieved by continuously moving the jet flow within the surroundings. The concept is to have the jet flow rapidly attaching and detaching (pulsing). The pulsing of the jet flow increases the mixing and results in an increase in the mass flow rate.

The pulsing worked well in the tens of Hertz range and showed up to 45% increase in mass flow even in the presence of an onset flow.

This CDE project was based on initial private venture work using CFD modelling. The aim was to provide proof of concept. To achieve this aim a physical hot gas model was constructed for tests as well as 3D full concept modelling.

This CDE project has allowed the feasibility of thrust efficiency improvements to be studied. With positive results achieved it could provide a basis for viable propulsion systems for future air systems.