Investigation on oxidation deposition characteristics and its inhibition tactics in aero-engine swirl nozzle

•Oxidation deposition characteristics of jet fuel in swirl nozzle were explored.•The numerical method for predicting deposition in swirl nozzles was proposed.•The reason for carbon deposition in each nozzle component was explained.•The anti-coking effect of TiN coating on swirl nozzle was evaluated. As a hidden danger of modern aircraft, the problem of nozzle carbon deposition must be addressed. Carbon deposition prediction and suppression methods for aviation nozzles still need further study. In this study, fouling experiments of the aero swirl nozzle were conducted to analyze the deposition characteristics of each component, and the deposit distribution of nozzle under different working conditions was predicted by numerical simulation. Finally, the anti-coking effect of the TiN coating on swirl nozzle was evaluated. The results showed that the buoyancy force could lead to an uneven distribution of deposits in the fuel feed arm. High inlet temperature fuel carries more precursors and results in a swirler surface covered with deposits, whereas for low inlet temperature fuel, deposits accumulate on the boss near passages inlet. The reaction species content, local velocity and temperature determined this. The deposition layer on the nozzle orifice surface is the densest owing to the high temperature and oxygen-rich environment. The TiN coating was applied to the inside and outside of the nozzle by chemical vapor deposition (CVD). The coating protection on fuel feed arm and swirler was inconspicuous. However, it exhibited the best anti-coking effect on the orifice surface. In this study, the causes of carbon deposition in swirl nozzles were determined and the protective effect of TiN inert coating was evaluated for the first time.