A fuel injector has been designed with the capacity to change effective area and fuel placement by varying the swirl number. This gives more flexibility on fuel/air mixture control than current designs, allowing a potentially wide turndown to be achieved whilst maintaining low emissions at high power. The fuel injector utilises fluidic control, eliminating the need for mechanical moving parts in the hot region commonly found in current variable geometry fuel injector designs.
The concept was evaluated and showed promising improvement in stability compared to the baseline fuel injector. The control flow system, using fluidics, was developed in isolation. The concept and control systems were then combined and evaluated. Although variable swirl using fluidic control was achieved, it was not sufficiently optimised to separate the downstream outer and inner airflow as with the concept design. As such the observed improvement in stability was not as good as expected. However, the ability to control effective area, and fuel placement without the need for moving parts was proven.
It is therefore recommended that further work be performed to allow the optimisation of the device such that controllable improvements in stability performance can be achieved in line with the potential shown with concept testing.