Hello,

My query concerns the cooling of turbine. We have frame 6 gas turbines.

In the manual provided, it says that the 5th stage extraction from the compressor is also used to cool the wheelspace. But when a GT was under HGPI, i was not able to trace that line. The AE5 line is used only for bearing sealing.

Is it that different models have different cooling options?

I also want to know what parts of turbine does the discharge of exhaust frame blower cools. The discharge of 88TK connects at 2 points in the Turbine shell. Does the air from the discharge cools the 3rd stage nozzles also?

Does the air gets mixed in the air leaving the 3rd stage buckets?
I read elsewhere on internet that " The cooling air flow (of 88TK) splits, with part of the air passing along and cooling the turbine shell and the other portion flowing through the exhaust frame strut passages."

Strut passages is the same from where gases from 3rd buckets go to. Wont it lead to drop in the temperature of exhaust gases which would add to the losses and low input to the HRSG?

Please help!

 

Seeker,

Yes, The AE-5 is used for bearing sealing, also new model has AE-5 to supply the air for bearing sealing.

The 88TK is to supply the cooling air to turbine casing, exhaust casing and aft 3rd stage wheel. and there is no cooling air is supplied to cool 3rd stage nozzle, small portion of air to cool the wheel and buckets will mix with hot gas in the path even from beginning of turbine stage.Based on, construction, the 3rd stage bucket is designed without cooling air, only 1st and 2nd stage bucket.