What control system is used to operate gas turbine? What main parameter should be monitored in gas turbine?
How can I increase and decrease the load in gas turbine?

Can anyone help guide me to understand that? It will be most appreciated.

 

Hello, and welcome to control.com!

One of the best features of control.com is its 'Search' feature. It really is one of the best you'll find on any website on the Internet/World Wide Web for a forum of this kind. It accepts multiple word searches, which most Search functions completely choke on.

Over the last few years, the heavy duty gas turbine community (primarily GE-design units) has been growing nicely on control.com, meaning there is good deal of information available on a variety of gas turbine control-related topics that you can find by using control.com's Search function. Hopefully you've already been using the Search feature, and these are just questions that you haven't already found answers to.

Many people have found the threads in which a former contributor made comments and provided information to be very helpful; he usually "signed" each contribution with markvguy so if you use the Search function and just put in markvguy you will find a lot of threads.

Unfortunately, this site doesn't have a "Topic" for turbine-related posts and the originators of threads can choose to put their questions or requests in any Topic, which makes looking for specific information in topics kind of difficult since one can find completely un-related threads in any Topic. But, Topics are also a good place to look for turbine-related threads.

To your first question, a turbine control system is used to control a turbine. It can be a dedicated control system used solely for turbine control; it can be a PLC (programmable logic controller) configured to control a turbine and its auxiliaries; it can be a mechanical control system with very few electrical or electronic parts. But whomever assembled the control system of whatever components *MUST* know how a turbine and its auxiliaries are supposed to operate in order to be able to make the control system do what it should, which is control, monitor, and protect the turbine and its auxiliaries to protect the equipment, the personnel around the unit, and to ensure optimal parts life, longevity, and very importantly reliability.

GE uses a proprietary control system called Speedtronic to control, monitor, and protect their gas turbines and auxiliaries. There have been several generations of Speedtronic, called Mark I, Mark II, Mark IV, Mark V, Mark VI, and now there are even beginning to be some "hybrid" versions with "e"s and "M"s attached to the Roman numeral characters (like Mark VIe and Mark IVM). Some owners have contracted with some control system integrators to provide various PLCs as turbine controls to replace older Speedtronic turbine control panels. Some DCS manufacturers have adapted their control systems for gas turbine control applications. One turbine manufacturer, Solar, uses Allen-Bradley PLCs to control their turbines and auxiliaries; they call their control system TurboTronics. Siemens uses a hybrid version of their S7 PLC adapted for gas turbine controls; one recent thread called it a SPPA T3000. A company called Woodward Governor Co. makes all kinds of turbine and prime mover controls, through they don't make any prime movers (that I'm aware of at this time). So, there are lots of control systems in use for controlling gas turbines and their auxiliaries. But the same caveat applies: Whomever designs, builds and applies the control system has to know how the unit is to be controlled and protected for safety, longevity, and reliability. There are lots of control systems being used on gas turbines, but what sets the best ones apart from the rest are those that are reliable. And reliability encompasses many things including, but not limited to, safety and longevity; it also has to do with robustness and suitability for application, and the instruments and devices it must monitor and operate. And it must do all of this in a fashion that is understandable.

To your second question, the "main" parameter to be monitored in a gas turbine? As with all rotating machinery, speed is usually pretty critical, and overspeed protection for turbines is a primary concern and must constantly be monitored. Exhaust gas temperatures cannot exceed a certain limit (machine-specific) or the unit will literally "melt" and/or the parts life will be severely shortened. Vibration monitoring is also a primary consideration, as is adequate Lubricating (Lube) Oil pressure. There are many more parameters which must be closely monitored to protect the turbine and maintain optimal parts life; those are just a few.

As for increasing load on a gas turbine, gas turbines are really just what are called "prime movers": they provide torque to whatever equipment they may be "driving": a generator or a compressor or some other device which requires torque to produce some desired result. One increases the torque output of a prime mover by increasing the energy input to the prime mover. In the case of a gas turbine, that is done by increasing the fuel flow-rate; same for a diesel engine being used as a prime mover, or a reciprocating engine burning waste gas from a refinery or landfill. Increasing the steam flow-rate into a steam turbine will increase the torque produced by the steam turbine that can be transmitted to the load (the driven device: the generator or the compressor or ....) If the prime mover is driving a generator, the generator is a device for converting torque into electrical energy, amperes, or amps. The amps "produced" by the generator will be used by electric motors to do what motors do: convert electrical energy into torque. Amps can also be used to generate heat and light, or, in the case of computers, what I like to call "virtual torque" or information energy. In the case of a compressor, the increased torque will cause the compressor throughput to increase and usually an increase in the pressure output of the compressor, as well.

Again, welcome to control.com. Don't forget about other useful sites such as wikipedia.org and google.com--both very helpful for finding information for engineers, operators, just about anyone!

I hope some of the other contributors to these threads will chime in with their thoughts on your questions.

 

John,

I am not trying to be sarcastic.
What is tyre used on cars?

When you post a question of this type, be specific. For some one to give a useful answer you need to provide atleast following information:

Manufacturer, turbine type, model, etc.
Application.

 

You can use just about any PLC (PLC-5, Siemens S-7, GE-Fanuc) to control a gas turbine just as long as the program overall scan time is less than, say, 70mSec.

Parameters that you need to be concerned with are T5 (engine temp or 'turbine rotor inlet' temp {TRIT}) T7 (exhaust gas temp) NGp (or NGG. NGp = gas producer speed, NGG gas generator speed) NPt (power turbine speed in a 2 shaft machine) and then other things like driven equipment speed. e.g. generator frequency, pump or compressor head, boat speed, etc.

Usually, all these parameters are monitored using instrumentation with the parameter closest to its limit being the one that the controls the fuel input to the machine. e.g. speed may be controlled but as load is increased (speed tends to decrease so more fuel is added) until the amount of energy input increases engine temperature to some rated limit. At this point control of the fuel system will shift to, say, T5 or T7 control. Any further increase in load will be rejected by the machine or cause it to shutdown.

A turbine is a pretty complex thing to try and control. Its response differs at different speeds and loads. The driven equipment can profoundly affect the machine and, in any case, if the driven equipment parameter is being used to control the machine, its system response will also have to be catered for.

You'll probably need a pretty robust model of the equipment (which OEM's may well be reluctant to hand over). Apart from the usual P&I or P+I+D control, there may be a lead, lag, or lead/lag algorithm as well.

Good luck!

Phineas