The blades are hollow and have air injected from where they attach to the outside edge and fin of the blade, so when it’s spinning the blade doesn’t contact the exhaust stream because it’s coated with a layer of relatively cold air. Same thing happens with your car pistons but using an inertial layer.
Image search for a turbine blade and you’ll understand as soon as you see it.
The reason you can’t shut the engine down or power off suddenly is because the blades and housing cool at different speeds, the clearance between the blade tips and housing is as close as possible.
To help with this, hot air from the turbine is sprayed onto the outside of the casing via a hot bleed air bypass when the ecm determines its necessary.
If you shut down suddenly the tips of the blades can contact the housing and best case rub, worst case break.
There’s another problem along these lines which really exemplifies how tight these tolerances are, on the a320, you need to do a bowed rotor procedure if you’ve been sitting with the engines off for 45 minutes before you restart. This involves turning the engine over with the apu to equalize the cooling throughout the engine because the core of the engine cools slower but there’s two shafts running through the middle. These shafts “bend” because the outside is cold but the middle is hot, they can then rub against each other ruining bearings etc.
Your china charger doesn't have clearances that tight.
Turbo timers are a legacy from the days when turbos were primarily oil cooled and synthetic oil wasn't common and shutting down a glowing hot turbo would tend to create sludge if done habitually.
This is amazing yet again that they can ingest rain and snow so the inside can be, what, close to 3000F yet you can come into land in Minneapolis when it's -30F and everything Just Works. Imagine how different aviation would be if in an alternate universe we had modern jet engines but under no circumstances could they ingest water?
Note that at cruising altitude it would be more like -80F. The engine would be more efficient at sea level at -30F as the mass flow rate would be higher. Ingesting water vapour actually improves things for the same reason. The downside is it can cause corrosion over time.
Image search for a turbine blade and you’ll understand as soon as you see it.
The reason you can’t shut the engine down or power off suddenly is because the blades and housing cool at different speeds, the clearance between the blade tips and housing is as close as possible.
To help with this, hot air from the turbine is sprayed onto the outside of the casing via a hot bleed air bypass when the ecm determines its necessary.
If you shut down suddenly the tips of the blades can contact the housing and best case rub, worst case break.
There’s another problem along these lines which really exemplifies how tight these tolerances are, on the a320, you need to do a bowed rotor procedure if you’ve been sitting with the engines off for 45 minutes before you restart. This involves turning the engine over with the apu to equalize the cooling throughout the engine because the core of the engine cools slower but there’s two shafts running through the middle. These shafts “bend” because the outside is cold but the middle is hot, they can then rub against each other ruining bearings etc.