Robust Fuel Injectors for Combustion Instability Reduction

Combustion instability is an ongoing concern for military propulsion systems such as augmented gas turbine engines. Augmentor screech can limit the performance of military aircraft and can cause durability issues or even catastrophic failure if it occurs. Modern augmentors have close-coupled fueling using simple round injectors to minimize manufacturing cost. In a “jet-in-crossflowâ€Â injector, liquid fuel issues from an orifice and the penetration of the fuel jet depends on the flow rate of fuel. Screech combustion instabilities are dependent on this static flame stability and thus dependent on the penetration and atomization of the fuel jet. The prevalence of screech in the lower corner of the flight envelope is directly related to over-penetration of the fuel jets at the high fuel flow rate. Screech instabilities can be largely mitigated if a fuel injector is developed that produces a robust, largely invariant fuel distribution with good fueling of the flameholder wake. We propose to develop novel fuel injectors that are insensitive to fuel flow rate and thus engine operating condition. These injectors will more homogeneously fuel the augmentor over the flight envelope, leading to more robust combustion stability and reduced susceptibility to screech, mitigating screech before instability can initiate and grow.