i have question please. we have two type of frame size turbine frame 5 and 7 . in the exhaust there are 13 thermocouple in frame 5 and 18 thermocouple why the different in number of thermocouple?

also why not to take one thermocouple instead of them?

Thank i hope to get answer when you stand question by sharing?

 

The exhaust frame of the frame 7 is larger and there are more combustion cans than on the frame 5. The thermocouples are essentially averaged (on older controls they were averaged) by using the median temperature for control. Also, the thermocouples are compared to adjacent ones to calculate spreads that are used to determine combustion problems.

A single thermocouple would not be as reliable, nor could you be sure you were getting a representative temperature reading.

Note, the frame 7FA and 9FA have 31 exhaust thermocouples.

 

in frame 7 has 10 cans only not above. i think more than 10 cans in frame 9

 

There are more than 10 cans in the 9F - either 12 or 14. Since I haven't worked directly on gas turbine controls for more than 20 years, and when I did I mainly worked on frame 3 and frame 5 mechanical drives, my memory is a little fuzzy there. My recent work has been on combined cycle controls, mainly on 9F projects.

It's also possible the 7F has less than 31 exhaust thermocouples, but it is more than 18.