Hi all!

I am a trainee engineer at a power generation facility which employs combined cycle. I would like to know what will be the effects of reduced water injection on gas turbines and in particular the overall efficiency of the gas turbine. The machine in question is the GE-6FA turbine.

 

Dani_p,

Welcome to the industry! Power generation, and the world of gas turbines is very exciting and filled with opportunities for someone with an inquisitive mind and ambition.

There are two types of water injection: that used for NOx emissions reduction (the most common type of water injection), and that used for power augmentation to increase the power output of the turbine-generator (the least common use).

Most F-class GE-design heavy duty gas turbines have DLN (Dry Low NOx) combustors, but not all, which can reduce NOx emissions without the use of water injection when burning natural gas (and some other gaseous fuels), but require water injection when burning liquid fuels. Units without DLN combustors may use water injection for NOx emissions reduction when burning any fuel.

But, in general, water injection is not required for normal operation--just for emissions reduction. So, reducing the water injection flow-rate should really have no impact on the turbine, and in fact increases efficiency <b>at part load.</b>

Water injection actually increases wear on hot gas path parts, so reducing it is usually better for parts life. But, if it's being used for emissions reduction then emissions are going to increase--and that could mean fines and/or jail in some parts of the world....

Without knowing more about the machine (type of combustors) and the fuel(s) being burned, and/or if water injection is being used for power augmentation it's difficult to say much more with any certainty.

Hope this helps--and we're here to answer questions and clarify things; there's a wealth of knowledge and experience available here for you. And again welcome to the industry. If you'll invest some personal time and effort in learning GE machines it will definitely be worth your while and can lead to a satisfying and profitable career.