I had been working in Aviation for 20 years before my new career as an O&M started in the Power Industry. We can get our inlet air Temp down to about 46'f before the LP sprint switches to HP mode. For some reason I can't get my head around why. All the people I work around seem to think using the HP Sprint is a bad thing. I think that at higher power loads to inject water into the HP compressor would cool the compressor discharge and increase the volume of air going into the combustor. This might let the LM6000 run at higher loads not being in T-48 control. Where the controlling factor is the max TIT this runs the Lm at its hottest temperature. I just don't know enough about why they HP Sprint when they do.
I can sympathize with your frustration. The aviation industry demands--and gets--much better documentation about engines and auxiliaries. Aero-derivative engines packaged for land-based applications, which similar to those used for aviation purposes, don't get the same level of documentation. Mostly because the packagers aren't required to provide the same level of documentation, but mostly because the packagers of land-based turbines don't want to document their equipment and auxiliaries to the same level as other industries. (It's actually not peculiar to the power generation industry....) In fairness, it does cost money to produce good documentation--and to maintain it as products and processes change--and the power generation industry already SCREAMS about cost. So, the technicians are left to suffer.
Does this help at all?
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I'm not fond of nor very familiar with aero-derivative engines used for power generation applications. Most of that stems from bad experiences with aero-derivative units and a lot of exposure to heavy duty gas turbines.
I am aware that GE did, maybe still does, publish a document that describes exactly how aero-derivative turbines are to be controlled in land- and marine applications. I can't recall the name of that document, but it's pretty explicit--and very useful. Unfortunately, it just lists limits of operation, and doesn't tell packagers exactly how to implement those limits. But, for many functions it's very helpful. Hard to get a copy of, but very helpful.
Again, I just used my preferred Internet search engine to search for "LM SPRiNT" and this was one of the first search results to be displayed.
Hope this helps!
I find that I don't truly understand some concept until I can explain it to somebody else and help them understand it. (I copied that from a former colleague--who was right!) So, if you develop a good understanding of these concepts, please, write back to this thread and share what you've learned with us. There is a pretty good community of GE-design heavy duty gas turbine users here. And a lot of GE-design aero-derivative users who would like to get and share more information here on control.com.
Lastly, we like to say here: "The most important contribution is feedback!"(c) If you read some of the other gas turbine controls-related posts you will find that many of them include feedback from the original poster or others who have read the post(s) and found the information useful. That's the real value of forums like this: Helping MANY people instead of just one, by putting the answers to questions and problems in an accessible place--but more importantly by providing feedback to others reading the posts, sometimes years later, about whether the information was helpful, or not. It's the feedback that lets others know if they received information that was useful in understanding or resolving their question or problem.
i can tell you, only from my experience, that hp sprint give's less MW then LP sprint. we work with lp sprint all the time. the sprint first job is to give the air more density. the air in the HPC is too hot so the sprint can't give the requires density for more MW.
I repeat this is only from my own experience at the power plant that i work in.
I can tell you from experience that LP sprint is more effective than HP sprint as another user has said, but the only reason is that the injection schedule for HP sprint is far less than that of LP sprint. I like you and CSA wish that there was more documentation out there, and if you find anything in print that is shareable I know myself and others would love to read it.
What I say here is just my understanding of operation from the time when I used to operate a LM6000PC. I can say that GE did not like to use HP sprint, because of the small amount of time for full atomization, and the high temperature at the inlet to the HP compressor, compared to water temperature of sprint. They always much preferred to operate LP sprint to increase mass flow and lower inlet temperature.
As I am sure you are well aware injecting water into the turbine is not a good thing for turbine life. But the gain in output outweighs the negatives for sure. The unit I operated used steam injection for Nox abatement instead of water injection, and this greatly increased the life of the combustor as compared to water injected units.
So I know this did not really directly answer your question. My basic understanding is that the decision to run LP or HP sprint is mainly driven by inlet temperature. As your inlet temperature falls too low then I believe the concern for icing is the reason that the unit switches from LP sprint to HP spring injection. For the best output you need to be able to cool your inlet to the lowest temperature that still allows the unit to operate in LP spring mode.
Five years too late but I think LP SPRINT switches off at 46°F (ambient) in order to avoid the possibility of ice formation at compressor inlet. Increased air velocity at the inlet results in lower pressure which causes adiabatic cooling of the air. So the air at the compressor inlet can approach freezing when ambient air approaches 46°F.