Investigation of Fuel Deposition in an Aviation Fuel Injector Under Controlled Conditions Using a Last-Chance Screen

Abstract Aviation jet engines often encounter anomalies in the fuel injector system that result in inefficiencies and lifetime reduction of the overall propulsion system. One of the primary causes of these anomalies is the thermal degradation of jet fuel when exposed to high temperatures at relevant engine conditions. This thermal decomposition can lead to the formation of carbon deposits that build up over time in atomizer passages, subsequently affecting injector spray patterns to the combustor and decreasing combustion efficiency. Hence, a “last chance” screen is used at the inlet of the injector to filter out unwanted solid particles from the degraded fuel. However, without proper maintenance a screen can experience deposit adhesion or fouling. To mitigate this issue, novel frangible-coated screens serve to slough-off deposits from surfaces by reducing the strength of adhesion forces. An experimental apparatus was developed to investigate the occurrence and causes of deposits on a screen. This tool also allows us to test coated screens that offer the ability to delay clogging of an injector. The apparatus simulates jet engine conditions in a controlled environment, allowing for the effect of flow rate, pressure, and temperature on fuel decomposition to be studied. This paper presents the results of coking experiments conducted over a realistic range of pressure and temperature and demonstrates the effectiveness of an advanced coating technology for mitigating carbon deposition.