FSR Startup Temperature

S

Thread Starter

saha

I have gone through the BBL of Start up FSR FSRSUV1. I noticed the startup (FSRSU) is calculated as a function of the axial compressor airflow temperature (CQTC).

I want to know how the compressor discharge temperature can affect the FSRSU?
 
saha,

Please follow the CQTC signal from the input to the FSRSUV1 block back to where it is calculated and I believe you will find that it a value that is derived from the axial compressor <i>inlet</i> temperature, not from the axial compressor discharge temperature. If I recall correctly, CQTC is a temperature-corrected speed signal--and the temperature used for the correction is axial compressor inlet temperature, not axial compressor discharge temperature.

If the ambient temperature (which is roughly equal to axial compressor inlet temperature, especially at start-up) is low then the density of the air is higher than the machine's nameplate ambient temperature, and a little more fuel is usually required to ensure flame is established during starting. If the ambient temperature is higher than nameplate, then a little less fuel is necessary to establish flame--which reduces the thermal stresses on the hot gas path parts during starting.

This is the reason for the temperature bias--to help ensure flame is established during starting, warm-up, and acceleration--and to reduce thermal stresses to help prolong hot gas path parts life.

But--please research how CQTC is calculated and write back to let us know what you find. Your unit may be different, and that would be interesting, and a good thing to know.
 
Dear CSA,

Yes, you are right; CQTC (Compressor Air flow Temperature correction) is calculated from the compressor INLET temperature as follows:
CQTC = MED SEL (CQKTC MX,(CQTC RT)/(CQTIM<C>+460),CQKTC MN)

Where:
CQKTC MX: Compressor Temperature Maximum =1.25
CQKTC MN: Compressor Temperature Minimum =0.9
CQTC RT: compressor temperature ratio =540°F
CTIM: max comp. inlet flange temperature in °F
 
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