High-Temperature Fuel Coking Mitigation Frangible Coatings for Fuel Nozzles and Screens

Increasing heat loads projected for advanced aircraft of the near future will lead to higher fuel system temperatures. Fuel deposit issues currently prevent long-term fuel system operation at temperatures over ~300-400 F. Thermal fuel decomposition is expected to have the highest negative impact in the vicinity of the fuel injectors, which are wetted by fuel with the highest time-at-temperature exposure. Of specific concern are the "last-chance screens", positioned immediately upstream of the fuel injectors, because the screen openings comprise some of the smallest fuel passages in the entire system. Blockage of these passages can have serious consequences in terms of aircraft propulsion control with these issues exacerbated by the copper contamination of the fuel. In Phase 1 of the project PCI developed and proof-of-concept demonstrated a frangible coating for last-chance screens capable of sloughing off carbonaceous depositions from hot fuel.  In Phase 2 of the project, we will evaluate the coating properties at the larger scale with particular emphasis on fuel system flow conditions and geometries expected in a real aircraft fuel system. Multiple iterations will be executed to reach the 5X MTBO (defined as time to 80 % blockage of the screen) lifetime as predicted from the Phase1 proof-of-concept data. The coating composition and procedure will be applied to other components of interest in the refueling system especially the fuel nozzles under the same test and operating conditions. Prototype coated screens and nozzles will be fabricated and delivered to the Navy for additional testing.