CFM International have identified a potential problem with Leap-1A and Leap-1B engine, as used on the Boeing 737 MAX and Airbus A320neo aircraft, have been found to be suffering from coking of fuel nozzles at a much faster rate than anticipated.
What’s the problem 737 MAX and A320neo Engines facing?
Gas turbine engines are highly susceptible to a buildup of carbon, in a process known as coking. Deposits from evaporated fuel and other material create obstruction to the fuel nozzles,This obstruction can lead to uneven temperature flow within the combustion chamber and can cause hot spots to develop inside the high pressure turbine. These hotspots are responsible for premature wear and, potentially, to the failure of the engine.
Coke is the solid residue created when oil undergoes severe oxidative and thermal breakdown at extreme engine temperatures. The higher the temperature, the harder, blacker and more brittle the coke/deposit residue.
Coking classifications include: 1.Thin film 2.Mist/vapor 3.Puddles 4.Dynamic
Various factors and environmental conditions can contribute to coking happening, including the temperature of the engine at shutdown.The phenomenon is not about the nozzle design itself , it is caused by temperature-induced evaporation of unburned fuel, which leads to hard deposits of solid carbon being laid down in some parts of the engine, particularly the fuel nozzles spraying fuel into the combustor.