Inlet Bleed Heating in DLN#1
- Thread starter KHEIBARY
- Start date
KHIEBARY,
IF YOU'RE WORKING ON A GE-DESIGN HEAVY DUTY GAS TURBINE WITH DLN COMBUSTORS, YOU SHOULD HAVE EASY ACCESS TO THE OPERATIONS & MAINTENANCE MANUALS AND DOCUMENTATON PROVIDED WITH THE EQUIPMENT. THERE ARE SYSTEM DESCRIPTIONS FOR EACH SYSTEM IN THE MANUAL (SOME ARE BETTER THAN OTHERS) AND THERE IS ALWAYS THE CONTROL SPECIFICATION DOCUMENT FOR THE MARK* AND THE PROGRAMMING IN THE MARK* WHICH CAN BE USED TO DETERMINE/PROVE WHAT'S SUPPOSED TO HAPPEN AND WHEN.
IF YOU'RE WORKING ON A GE-DESIGN HEAVY DUTY GAS TURBINE WITH DLN COMBUSTORS, YOU SHOULD HAVE EASY ACCESS TO THE OPERATIONS & MAINTENANCE MANUALS AND DOCUMENTATON PROVIDED WITH THE EQUIPMENT. THERE ARE SYSTEM DESCRIPTIONS FOR EACH SYSTEM IN THE MANUAL (SOME ARE BETTER THAN OTHERS) AND THERE IS ALWAYS THE CONTROL SPECIFICATION DOCUMENT FOR THE MARK* AND THE PROGRAMMING IN THE MARK* WHICH CAN BE USED TO DETERMINE/PROVE WHAT'S SUPPOSED TO HAPPEN AND WHEN.
IBH (Inlet Bleed Heating) is a very poor name for the function it provides. Using IBH allows a GE-design heavy duty gas turbine with DLN-I combustors to transfer into Premix Steady State (the lowest emissions mode) sooner than would otherwise be possible, AND it also allows the unit to remain in Premix Steady State longer when unloading. Without IBH, a GE-design heavy duty gas turbine with DLN-I combustors would transfer into Premix Steady State at about 80% of rated load, and remain in Premix Steady State up to Base Load. Without IBH, when unloading the unit while operating in Premix Steady State the unit will transfer out of Premix Steady state around 80% of rated load, sometimes a little lower. This means the operating range in the lowest emissions mode (Premix Steady State) is between approximately 80-100% of rated load--which for some applications and sites is a very narrow range of operation; some sites need to operate as low as 40-50% of rated load in Premix Steady State (the lowest emissions mode).
So, IBH was "invented." The designers of DLN-I knew that if the axial compressor inlet guide vanes could be closed below the compressor normal minimum operating angle (at rated speed) of 57 DGA (DeGrees Angle) that the turbine could operate in Premix Steady State in a wider range of load. The problem with closing the IGVs below 57 DGA is that the axial compressor can suffer some problems and even damage (sometimes severe) when the IGVs are closed below 57 DGA. The also knew that if a portion of the axial compressor discharge could be extracted before it entered the combustors this would help widen the Premix Steady State operating range. And, further, they knew that if they could decrease the density of air entering the axial compressor even by a little bit the axial compressor would be protected from some of the problems encountered when operating at rated speed with the IGVs closed below 57 DGA.
IBH extracts axial compressor discharge air (a portion of it) and recirculates it a manifold in the axial compressor inlet air duct where it exits the manifold and adds a couple of degrees of heat to the incoming, filtered air entering the axial compressor. This serves to help decrease the density of the air entering the axial compressor which helps to reduce possible damage to the axial compressor when the IGVs are closed below 57 DGA at rated speed. Extracting axial compressor discharge air also reduces the back-pressure on the axial compressor which helps to protect the compressor when the IGVs are closed below 57 DGA when at rated speed. And, recirculating the extracted axial compressor discharge air helps to reduce the energy lost by extracting axial compressor discharge air (which has been compressed by the axial compressor).
When IBH is enabled and active during the start-up of a GE-design heavy duty gas turbine with DLN-I the IGVs will be held to an angle of approximately 42 DGA when the unit reaches rated speed. And, as the unit is loaded the IGVs will be modulated (positioned) to an angle so as not to exceed the maximum allowable exhaust temperature. The net effect of keeping the IGVs closed during starting and initial loading is to reduce the air flow into the combustors, which will allow the unit to transition into Lean-Lean and then Premix Steady State sooner (at lower loads) than would otherwise be possible (that is: without IBH). Most DLN-I combustor-equipped units with IBH enabled and active can transfer into Premix Steady State at loads as low as approximately 40% of rated, and then as the unit continues to be loaded IBH will remain in operation until the IGVs reach approximately 62 DGA, at which time IBH will be deactivated (the IBH control valve will be closed).
Now, as the turbine is unloaded when IBH is enabled (but not yet active!) as the IGVs approached approximately 62 DGA IBH will become active again. As the unit continues to unload, to approximately 40% of rated load, the IGVs will continue to close (but never less than approximately 42 DGA) and the unit will transfer out of Premix Steady State into Lean-Lean. And eventually as unloading continues it will transfer out of Lean-Lean and into Primary mode.
When IBH is enabled during a START, it will be active when the unit reaches FSNL (Full Speed-No Load; rated speed). It will remain active until the IGVs reach approximately 62 DGA as the unit is loaded, and the unit will transfer into Premix Steady State at approximately 40% of rated load. When IBH is enabled during a unit shutdown while operating in Premix Steady State IBH will become active as the IGVs approach approximately 62 DGA angle and the unit will remain in Premix Steady State until the load drops below approximately 40% of rated. IBH will continue to remain active until the unit drops below rated speed.
I don't know if this will serve your purpose. But it's all I got; all I can offer. (No I can't email it to you, or text it to you. You can copy the text and print it.)
If you have Mark V or newer turbine control system, you can trend the operation of IGV angles, IBH control valve position, load, and combustion mode, and produce a very nice graph which will depict all of this very nicely. No words, but actionable data--and for your specific machine. For Mark V, the function is called Short Term Trending. For Mark VI and Mark VIe the function is called Trend Recorder or Trender.
Hope this helps! ('Please' and 'thank you' are good words to use when asking for help/information/assistance using the English language.... 'Doubt' IS NOT a good word to use when asking for help or clarification when using the English language.)
Finally, there is a 'Search' feature at the top of every Control.com webpage. It can be used to search all past posts and responses on Control.com. Every past post and response(s) are available using the 'Search' feature. And, this topic (IBH operation) has been covered MANY times before on Control.com.
So, IBH was "invented." The designers of DLN-I knew that if the axial compressor inlet guide vanes could be closed below the compressor normal minimum operating angle (at rated speed) of 57 DGA (DeGrees Angle) that the turbine could operate in Premix Steady State in a wider range of load. The problem with closing the IGVs below 57 DGA is that the axial compressor can suffer some problems and even damage (sometimes severe) when the IGVs are closed below 57 DGA. The also knew that if a portion of the axial compressor discharge could be extracted before it entered the combustors this would help widen the Premix Steady State operating range. And, further, they knew that if they could decrease the density of air entering the axial compressor even by a little bit the axial compressor would be protected from some of the problems encountered when operating at rated speed with the IGVs closed below 57 DGA.
IBH extracts axial compressor discharge air (a portion of it) and recirculates it a manifold in the axial compressor inlet air duct where it exits the manifold and adds a couple of degrees of heat to the incoming, filtered air entering the axial compressor. This serves to help decrease the density of the air entering the axial compressor which helps to reduce possible damage to the axial compressor when the IGVs are closed below 57 DGA at rated speed. Extracting axial compressor discharge air also reduces the back-pressure on the axial compressor which helps to protect the compressor when the IGVs are closed below 57 DGA when at rated speed. And, recirculating the extracted axial compressor discharge air helps to reduce the energy lost by extracting axial compressor discharge air (which has been compressed by the axial compressor).
When IBH is enabled and active during the start-up of a GE-design heavy duty gas turbine with DLN-I the IGVs will be held to an angle of approximately 42 DGA when the unit reaches rated speed. And, as the unit is loaded the IGVs will be modulated (positioned) to an angle so as not to exceed the maximum allowable exhaust temperature. The net effect of keeping the IGVs closed during starting and initial loading is to reduce the air flow into the combustors, which will allow the unit to transition into Lean-Lean and then Premix Steady State sooner (at lower loads) than would otherwise be possible (that is: without IBH). Most DLN-I combustor-equipped units with IBH enabled and active can transfer into Premix Steady State at loads as low as approximately 40% of rated, and then as the unit continues to be loaded IBH will remain in operation until the IGVs reach approximately 62 DGA, at which time IBH will be deactivated (the IBH control valve will be closed).
Now, as the turbine is unloaded when IBH is enabled (but not yet active!) as the IGVs approached approximately 62 DGA IBH will become active again. As the unit continues to unload, to approximately 40% of rated load, the IGVs will continue to close (but never less than approximately 42 DGA) and the unit will transfer out of Premix Steady State into Lean-Lean. And eventually as unloading continues it will transfer out of Lean-Lean and into Primary mode.
When IBH is enabled during a START, it will be active when the unit reaches FSNL (Full Speed-No Load; rated speed). It will remain active until the IGVs reach approximately 62 DGA as the unit is loaded, and the unit will transfer into Premix Steady State at approximately 40% of rated load. When IBH is enabled during a unit shutdown while operating in Premix Steady State IBH will become active as the IGVs approach approximately 62 DGA angle and the unit will remain in Premix Steady State until the load drops below approximately 40% of rated. IBH will continue to remain active until the unit drops below rated speed.
I don't know if this will serve your purpose. But it's all I got; all I can offer. (No I can't email it to you, or text it to you. You can copy the text and print it.)
If you have Mark V or newer turbine control system, you can trend the operation of IGV angles, IBH control valve position, load, and combustion mode, and produce a very nice graph which will depict all of this very nicely. No words, but actionable data--and for your specific machine. For Mark V, the function is called Short Term Trending. For Mark VI and Mark VIe the function is called Trend Recorder or Trender.
Hope this helps! ('Please' and 'thank you' are good words to use when asking for help/information/assistance using the English language.... 'Doubt' IS NOT a good word to use when asking for help or clarification when using the English language.)
Finally, there is a 'Search' feature at the top of every Control.com webpage. It can be used to search all past posts and responses on Control.com. Every past post and response(s) are available using the 'Search' feature. And, this topic (IBH operation) has been covered MANY times before on Control.com.
Very elaborate...
Thank you for this..
But in my plant, the IBH is deactivated because the incoming air is dry and less dense ...it's a temperate region...
The IBH has a manual and pneumatic valve which are permanently closed and over riden and as such they're not permissives for a start up.
It's a frame 9e gas turbine with mark VI control system with compression ratio of 1:12.6
Dan Raye,
The unit must probably operate at or near Base Load most of the time?
That seems an odd reason to "deactivate" IBH (because the incoming air is dry and less dense). I presume the ambient air temperature must never get too much below the ISO temperature rating (on the turbine nameplate) or too much above the nameplate temperature rating.
Again, for DLN-I systems, the primary purpose of IBH is to provide a wider load range while in Premix Steady State (the lowest emissions mode). So, if you're not using IBH, then it's more likely that you're not interested in the "turndown" (as it's called--reducing the lower load range limit (which really isn't a load limit; it's a function of air flow and firing temperature reference) with the unit at your site.
Anyway, glad you found the information useful!
The unit must probably operate at or near Base Load most of the time?
That seems an odd reason to "deactivate" IBH (because the incoming air is dry and less dense). I presume the ambient air temperature must never get too much below the ISO temperature rating (on the turbine nameplate) or too much above the nameplate temperature rating.
Again, for DLN-I systems, the primary purpose of IBH is to provide a wider load range while in Premix Steady State (the lowest emissions mode). So, if you're not using IBH, then it's more likely that you're not interested in the "turndown" (as it's called--reducing the lower load range limit (which really isn't a load limit; it's a function of air flow and firing temperature reference) with the unit at your site.
Anyway, glad you found the information useful!
Dan Raye and CSA,
CSA has given a very descriptive and informative explanation of IBH operation.
I will, however, stay on topic for a moment. KHEIBARY will not find the document he seeks. The document does not exist. As CSA pointed out, the CSP (Control Sequence Program) contains the data and constants that control CHBIROUT signal.
A hypothesis proposes a tentative explanation or prediction. ... A theory, on the other hand, is a substantiated explanation for an occurrence. Theories rely on tested and verified data, and scientists widely accepted theories to be true, though not unimpeachable.
I have a hypothesis regarding IBH ON or OFF. I have found that in areas where the turbines are meant to be operated remotely without any operating personnel on site. These turbines have IBH turned OFF.
IBH ON can be a demanding during cold winter conditions. IBH is air operated valve subject to freezing. If the IBH does not fully open at 14HS and synch is in AUTO; problems may occur if IBH does not respond correctly. If one is lucky, lean-lean operations will be the result. Don't forget the air operated gas xfer valves, they too can mess your DLN transfer up.
IBH ON does not try to recover DLN at the higher 80% load after failure during startup, therefore operator intervention is required. A Master Reset is required.
Remote operations generally have very little information to allow interaction. Generally a simple start, stop, raise load, lower load, etc. come from a remote transmission unit (RTU) is all that is supplied.
Perhaps, some folks will respond and let my thoughts become a theory.
CSA has given a very descriptive and informative explanation of IBH operation.
I will, however, stay on topic for a moment. KHEIBARY will not find the document he seeks. The document does not exist. As CSA pointed out, the CSP (Control Sequence Program) contains the data and constants that control CHBIROUT signal.
A hypothesis proposes a tentative explanation or prediction. ... A theory, on the other hand, is a substantiated explanation for an occurrence. Theories rely on tested and verified data, and scientists widely accepted theories to be true, though not unimpeachable.
I have a hypothesis regarding IBH ON or OFF. I have found that in areas where the turbines are meant to be operated remotely without any operating personnel on site. These turbines have IBH turned OFF.
IBH ON can be a demanding during cold winter conditions. IBH is air operated valve subject to freezing. If the IBH does not fully open at 14HS and synch is in AUTO; problems may occur if IBH does not respond correctly. If one is lucky, lean-lean operations will be the result. Don't forget the air operated gas xfer valves, they too can mess your DLN transfer up.
IBH ON does not try to recover DLN at the higher 80% load after failure during startup, therefore operator intervention is required. A Master Reset is required.
Remote operations generally have very little information to allow interaction. Generally a simple start, stop, raise load, lower load, etc. come from a remote transmission unit (RTU) is all that is supplied.
Perhaps, some folks will respond and let my thoughts become a theory.
Curious_One,
Many units (particular non F-class units) do not have IBH even if they have DLN-I. Again, it's main purpose is to provide more "turndown" (a larger Premix Steady State operating range of load). A lot of unmanned sites are peakers--meaning they run at or near Base Load when they run (usually). So, turndown is not so important.
And because it's not unusual for a unit being started from a "cold iron" (ambient temperature) condition to sometimes fail to make a Lean-Lean-to-Premix transfer on the first start attempt with IBH ON this is another possible reason for turning IBH OFF.
GE sold, for a time, what was called "transfer-less DLN-I" (among other things!). And many of those units did NOT have the option to turn IBH off (because forcing a LOT of fuel during a Lean-Lean-to-Premix transfer at 80% load through only the secondary fuel passages was kind of risky and caused a screeching sound during the transfer which most people DID NOT like to hear). So, they made IBH "mandatory." And, on some units which were retrofitted with DLN-I and did not have the space or ability to install the IBH manifold in the inlet duct they sometimes sold transferless DLN-I--but not too often, mostly because of the screeching noise during the transfer.
Finally, some requisition engineers just "forgot" to unhide the button to the HMI to disable IBH (the standard is there is no standard when it comes to HMI screens, right?). And sometimes they just forgot to allow IBH to be turned ON or OFF in the CSP or application code. (Same standard.... There isn't one.)
Instrument air should be dry.... Most IBH control valves I've seen (and associated valves/devices) are supplied by an instrument air source, usually from the plant instrument air. Some units were sold with a separate instrument air compressor (though I only saw those in the Middle East, where they also use instrument air to blow down the self-cleaning inlet air filters when the unit is not running. Not so with gas fuel purge valves; that air often comes from CPD extraction--which should be filtered (by the PoroStone filter, and should have a pressure regulator with a bowl to remove entrained moisture, which rarely gets drained, if ever). The continuous blowdown of the PoroStone filter OFTEN gets plugged with rust; it is, after, all a cast steel vessel and moisture rusts steel... So, the blowdown stops working when it gets plugged. (I always recommend that plants with an instrument air source connect it to ALL turbine/auxiliary air-operated valves and devices, and only use the CPD extraction as a back-up to the instrument air. Dry instrument air prevents so many problems--as you suggest.
GE has a relatively new sequence to allow transfer from Extended Lean-Lean to Premix WITHOUT reducing load to Lean-Lean positive and then reloading the unit back into Premix Steady State. By most reports, it works pretty well.
And, I hear they are also selling/providing electric-actuated gas fuel purge valves now, too. Which I hear have been pretty reliable (eliminating the pneumatic actuators).
But, none of that is theory. It's fact. No scientific method needed.
Many units (particular non F-class units) do not have IBH even if they have DLN-I. Again, it's main purpose is to provide more "turndown" (a larger Premix Steady State operating range of load). A lot of unmanned sites are peakers--meaning they run at or near Base Load when they run (usually). So, turndown is not so important.
And because it's not unusual for a unit being started from a "cold iron" (ambient temperature) condition to sometimes fail to make a Lean-Lean-to-Premix transfer on the first start attempt with IBH ON this is another possible reason for turning IBH OFF.
GE sold, for a time, what was called "transfer-less DLN-I" (among other things!). And many of those units did NOT have the option to turn IBH off (because forcing a LOT of fuel during a Lean-Lean-to-Premix transfer at 80% load through only the secondary fuel passages was kind of risky and caused a screeching sound during the transfer which most people DID NOT like to hear). So, they made IBH "mandatory." And, on some units which were retrofitted with DLN-I and did not have the space or ability to install the IBH manifold in the inlet duct they sometimes sold transferless DLN-I--but not too often, mostly because of the screeching noise during the transfer.
Finally, some requisition engineers just "forgot" to unhide the button to the HMI to disable IBH (the standard is there is no standard when it comes to HMI screens, right?). And sometimes they just forgot to allow IBH to be turned ON or OFF in the CSP or application code. (Same standard.... There isn't one.)
Instrument air should be dry.... Most IBH control valves I've seen (and associated valves/devices) are supplied by an instrument air source, usually from the plant instrument air. Some units were sold with a separate instrument air compressor (though I only saw those in the Middle East, where they also use instrument air to blow down the self-cleaning inlet air filters when the unit is not running. Not so with gas fuel purge valves; that air often comes from CPD extraction--which should be filtered (by the PoroStone filter, and should have a pressure regulator with a bowl to remove entrained moisture, which rarely gets drained, if ever). The continuous blowdown of the PoroStone filter OFTEN gets plugged with rust; it is, after, all a cast steel vessel and moisture rusts steel... So, the blowdown stops working when it gets plugged. (I always recommend that plants with an instrument air source connect it to ALL turbine/auxiliary air-operated valves and devices, and only use the CPD extraction as a back-up to the instrument air. Dry instrument air prevents so many problems--as you suggest.
GE has a relatively new sequence to allow transfer from Extended Lean-Lean to Premix WITHOUT reducing load to Lean-Lean positive and then reloading the unit back into Premix Steady State. By most reports, it works pretty well.
And, I hear they are also selling/providing electric-actuated gas fuel purge valves now, too. Which I hear have been pretty reliable (eliminating the pneumatic actuators).
But, none of that is theory. It's fact. No scientific method needed.
CSA,
Thank you for sharing your vast experience. Others will hopefully learn about IBH and DLN 1+ from this post.
Notice I am using
Inlet Bleed Heating in DLN#1
in the text for a SEARCH function.
I will be sharing a Mark V problem soon. I want to get all the logs sorted first. This was a problem I have never seen or heard of before. Then again my Mark V systems are over two decades old.
Bravo Zulu CSA
Thank you for sharing your vast experience. Others will hopefully learn about IBH and DLN 1+ from this post.
Notice I am using
Inlet Bleed Heating in DLN#1
in the text for a SEARCH function.
I will be sharing a Mark V problem soon. I want to get all the logs sorted first. This was a problem I have never seen or heard of before. Then again my Mark V systems are over two decades old.
Bravo Zulu CSA
Curious_One,
There is a DLN-1+ system from GE. It uses a continuous emissions monitor system to provide information to the Mark*. I don't have any experience with it, but I hear it provides very low emissions levels (low single digits, I'm hearing). I don't anything more about it (unfortunately). I imagine it's still a staged combustion system (meaning that fuel is "moved" around between two combustion zones.
I don't understand the statement, "Notice I am using .... in the text for a Search function." Is it working, or not working, or ??? How would we know what Search term(s) you are using?
Two decades ago was nearly the end of the Mark V production life (in the USA), and the beginning of the testing/production of the Mark VI. Actually, as I think about my first Mark VI-based units, it was in early 2000/2001.
Anyway, get your logs in order.
There is a DLN-1+ system from GE. It uses a continuous emissions monitor system to provide information to the Mark*. I don't have any experience with it, but I hear it provides very low emissions levels (low single digits, I'm hearing). I don't anything more about it (unfortunately). I imagine it's still a staged combustion system (meaning that fuel is "moved" around between two combustion zones.
I don't understand the statement, "Notice I am using .... in the text for a Search function." Is it working, or not working, or ??? How would we know what Search term(s) you are using?
Two decades ago was nearly the end of the Mark V production life (in the USA), and the beginning of the testing/production of the Mark VI. Actually, as I think about my first Mark VI-based units, it was in early 2000/2001.
Anyway, get your logs in order.
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