Very good evening to everybody. I would like to explain to me some of the doubts that I have.

1.What the relation between the compressor discharge pressure (CPD) and allowable spread in Gas turbine?

2.If the CPD is less compare to the actual reading, what does it mean?

3.What the relation between the inlet guide vane (IGV) and compressor discharge pressure (CPD)?

4.What is the relation between the compressor discharge pressure (CPD) and exhaust temperature?

thanks

 

Doubts are not good things; please read the Oxford English Dictionary definition of doubt to understand why.

Questions and curiosity we can handle; doubts are out.

I would ask you to tell us how you view each relationship, and we can work from there.

 

Reposting, I suspect first reply didn't go through.

I think there is no relationship between CPD and allowable temp. But IGV opening will affect CPD. However, there is relationship between CPT ( compressor discharge temp) and allowable as follow:
Here is what is happening:
Allowable spread is calculated as:

(TTXM*0.08 +30 - CTD*0.145)

Anytime following things take place a bias of 150 is added ( for 60 secs) to this calculation in seeing forthcoming abnormalities instead of disabling exhaust spread monitor algorithm, and when conditions return to normal allowable spread calculated result ramps back slowing to normal. This reading is median selected in between 30 and 120.Again, CPT is median select, if transmitter goes bad, this median select gate gets default reading for calculation.

1.Fuel transfer taking place (NG or C4 selected). In our case C4 is stand by fuel.

2.Load is lowered or raised manually or/otherwise due to auto for two or more seconds.

In one of the case set point for PRESET was 71 and whenever it drips ± around set point, GTG automatically lowers or raises the load for more then 2 second and a bias is added.

Thanks
Let me know if this is enough info.

 

1.What the relation between the compressor discharge pressure (CPD) and allowable spread in Gas turbine?

The allowable spread is calculated using the formula. At present i am taking this from a frame 6 machine , the constants given this formula will vary depending on the machine and site.

TTXSPL = ( -CTD*0.08) + (TTXM*0.12) + 47 + (150 - (150*e^-0.01t))

where t is the time from L83SPMB signal goes high.

though the formula does not have the CPD term in it , there is a indirect effect of CPD on the TTXSPL. for a constant load , with the increase in the CPD the CTD increases while the TTXM decreases , the exact formula for the relation is not known , it is given as a characteristic curve for each machine. perhaps a combustion expert may have a complex non linear differential equation which will represent the relation between CTD and CPD , but control engineers hardly have to worry about it lol.


if the CPD is less compare to the actual reading, what does it mean?

er ... though the question is not clear i am assuming the following. you calculated the required cdp from the characteristic graphs after applying the corrections for temperature, humidity/density, load, frequency, igv opening and you find that the cdp in your machine is low? well the problem could be

a. fouled compressor
b. choked inlet air filter which is reducing the inlet air flow
c. difference in the IGV opening to the actual one

3.What the relation between the inletguide vane (IGV) and compressor discharge pressure (CPD)?

The IGV increases or deceases the air flow into the turbine. for a constant load and frequency , as the IGV increases in opening the cdp also increases due to increased air flow and vice versa.


4.What is the relation between the compressor discharge pressure (CPD) and exhaust temperature?

again for a constant load and frequency as the CDP increases the exhaust decreases and vice versa.

all the above can be checked and the values for any operating point calculated from the characteristic curves given by ge.