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Repairing Combustion Chamber 2

The first item to receive some TLC is Combustion Chamber 2. This chamber (along with chamber 6) contains an ignitor.

The chamber was already loose due to an inspection, after removing it fully we found out why!

Combustion Chamber 2 removed

Chamber 2 removed from the engine

 

Combustion Chamber 2

The complete combustion chamber

In this picture you can see the fuel injector and air-ramp assembly at the left, the flame tube and liner in the middle and the exit with metal sealing rings to the right. The stubby pipe sticking out the side allows pressure-compensation between the flame cans and allows combustion to spead from the two cans with the igniters to the other cans.

The metal sealing rings are essentially the same as piston rings and were siezed solid. A local engineering firm removed them for me without damaging the groove.

Combustion chamber 2 liner

A view of the can liner, the injector and swirl vanes are visible to the back

With the can removed we could now see into the nozzle ring box and we found the reason why the chamber hadn't been re-attached very well (and probably why the engine was scrapped).

Damaged Nozzle Guide Vanes in Ring Box

Damaged Nozzle Guide Vanes

These fixed vanes ensure the airflow from the can impinges on the turbine wheel at the correct angle. The center vanes have been badly overheated and have lost a lot of material to ablation.

This is likely caused by cokeing of the fuel injector, resulting in a stream or onion shaped spray pattern rather than the usual cone. This abnormal injection of fuel has resulted in the combustion occuring in the wrong part of the can and overheating the NGVs.

 

The paint was peeling from the chamber lid so I decided to re-spray it. Apart from improving the look this gives it some corrosion protection so it's worth doing.

First the lid was bead-blasted back to bare metal:

And then sprayed matt black using some VHT Ultra High Temperature paint (pricey but worth it).

 


Previous page: New parts
Next page: Injector Repair


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