Hi everybody (GE GT guys)

I would request Mr.CSA to come forward and explain me the TTRXV5 BBL rung no 17 temp control ref. in seq trb 3.src. mark V <I>

I am very eager to learn GT control system, in our site we are using MK 5 speedtronics with frame 9E. I am quite familiar with field and system architecture, signal flow, voting, communication and few control concepts of speedtronics.

It would be better for us if persons like CSA or MARK5GUY comes forward and explain in their own language in the control.com forum,

I have seen lot of posts from many experts in this forum and I admire with CSA and Mark5Guy answers.

thanks you

 

First of all you need to understand that TTRXV5 does not always occur at rung number 17 in SEQ_TRB3.SEC on every gas turbine. Every gas turbine will have an Exhaust Temperature Control BBL, but it will not always be in SEQ_TRB3.SRC, nor will it always be at rung number 17 as it seems to be in the CSP at your site.

I believe markvguy wrote extensively about exhaust temperature control in more than one thread with a Rahul P. Sharma, who still occasionally posts here on control.com but seems to confused about fogging, and his posts about Speedtronic-related issues have dwindled significantly. I believe Rahul P. Sharma ends most of his posts with 'Au revoir, Rahul P. Sharma' so if you search for his posts or through those of markvguy you will find some good information. In one of his posts, I believe he even "drew" a picture of the exhaust temperature reference curve as part of his attempt to explain to Rahul P. Sharma why exhaust temperature doesn't increase when load and fuel flow increase when the unit is operating on exhaust temperature control.

You could also read this thread for more info:

http://www.control.com/thread/1238502195

I will start out by saying that exhaust temperature control represents a <b>constant firing temperature</b> and that firing temperature refers to the temperature of the combustion gases exiting the first stage turbine nozzle of a Frame 9E (I believe all Frame 9Es have air-cooled first stage turbine nozzles). Because there are no sensors monitoring the temperature of the combustion gases exiting the first stage turbine nozzle of a Frame 9E (because they wouldn't last very long and if they failed and broke off the parts would be in the hot gas path of the rotating section of the turbine and would cause extensive damage.

Empirical data has shown that exhaust temperature and axial compressor discharge pressure can be plotted against firing temperature to develop a fairly linear relationship. In other words, for a given exhaust temperature at a particular compressor discharge pressure, the firing temperature can be estimated with a relatively high degree of accuracy. Or, for a specific firing temperature the corresponding exhaust temperature and compressor discharge pressure can be determined.

So, a GE-design heavy duty gas turbine uses thermocouples in the exhaust of the gas turbine along with pressure transmitters sensing the axial compressor discharge pressure. When the exhaust temperature reaches a certain value for a given compressor discharge pressure then the unit has reached the firing temperature "limit" and is producing the optimal amount of power for the given operating conditions (ambient pressure; ambient temperature; ambient humidity; inlet filter cleanliness; compressor cleanliness; hot gas path parts condition; exhaust back-pressure; etc.). This is called 'Base Load' and the unit is said to be operating on exhaust temperature control (specifically when operating on CPD-biased exhaust temperature control, which is what we're talking about right now). And because ambient temperature, -humidity, and -pressure can all vary throughout the course of a day, the amount of power produced when operating at Base Load will also vary throughout the course of a day. And because compressors get dirty (foul) and hot gas path parts degrade over time and inlet air filters get dirty and the air flow through them is reduced, so too will the power output of the gas turbine when operating at Base Load on exhaust temperature control.

TTRXV5 is the algorithm by which the Mark V monitors exhaust temperature and compressor discharge pressure and calculates the exhaust temperature reference, usually signal name TTRX (Turbine Temperature Reference - Exhaust). When the actual exhaust temperature (TTXM) equals TTRX then the unit is said to be at Base Load, or on exhaust temperature control.

The formula, in its most basic form is:

TTRXP = TTKn_I - ((CPD - TTKn_C) * TTKn_S), where TTRXP is the Primary Exhaust Temperature Control Reference. (There is a 'back-up' or secondary exhaust temperature control reference, also.)

I believe the thread recommended above will provide a lot of answers to your question. If not, keep asking here. There are a lot of good people here at control.com who can help with your understanding. And the 'Search' function is very helpful if you're willing to work at finding the right words/terms.

Write back if you need more information.

By the way, markvguy had to stop contributing to control.com a year or more ago. Thanks to the legal "profession", I think it was.

http://www.control.com/thread/1026235304

Feedback is the most important contribution.(c)

Makes sense to me.

 

Hi Mr.CSA

Thank you for your reply and links provided.

regards

 

What CSA has stated is quite true, in our csp, the temperature control reference is TTRXV6 at SEQ_TRB2 (rung number - 97)

For your information, the backup reference curve or the secondary reference curve is TTRXS = TTKn_I - ((FSR - TTKn_M) * TTKn_K