The compressor is the front half of the gas turbine. "Online washing" is done while the turbine is running - i.e. the wash fluid goes through the engine and is burned up - as compared to "offline washing" where the machine is on barring gear and the wash fluid goes to drain. Offline washing typically uses a more concentrated cleaning solution.
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If we learn from our mistakes I'm getting a great education!
GTstartup, I would like to know where could I get an example of that calculation?, as you know ambient temperature and others have more influence than washing the compresor in MW.
Get the correction curves - Ambient temp, Humidity, Barometric Pressure, etc from the GT manufacturer.
To do the actual energy balance calculation is a whole different kettle of fish and is probably overkill to evaluate a water wash - you probably don't have the required instrumentation installed. (My last post notwithstanding
The best way to evaluate its effectiveness is in the change in compressor efficiency and in air passing capability. Lok up the definition of "polytropic efficiency" in Marks handbook and monitor the process conditions leaving as many stages as possible, and compute before and after efficiency.
Secondly , I heard that one of the major CTG vendors has internally discoverd that their online washing proceudre and equipment may be the primary cause of compressor blade cracking, but they willnot publically admit this due to warranty issues etc.
Online Compressor Washing can be evaluated by analyzing the Gas Turbine Output and Compressor Efficiency both before and after the washing. Be advised that this net gain is only temporary and will depend on many factors as to the effectiveness of inlet filtration, the operating environment, washing schedule and wash solution.
Offline Water Washing can be more effective than Online Water Washing as Online Washing tends to move the dirt from the front of the compressor to the back of the compressor in some cases causing compressors to loose efficiency and approach Stall Margins quicker.
If you have the time I would recommend Offline Washing wherever possible.
Crushed rather than ground - they're supposed to be abrasive to the surface contamination while harmless to the compressor blades. They burn up in the power turbine.
Wonder if they make the flue gas smell nice?
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If we learn from our mistakes I'm getting a great education!
On-Line washing causing cracks is not hearsay - its Fact! There is a very famous case of a user who on-line washed for two long and it was a major factor in blade liberation of the first stage blade.
I won't go into detail, but it cause lots of problems for lots of people, not least as the design was upgraded as a result, which turned out to cause more problems than it solved!! But that's another story.....
I think the answer given by 'GTSTARTUP' is the most practical approach, i.e. was for 20 minutes or so and the ambients will not have changed by much and do a compare of the results, even correcting will not be necessary in this instance, as long as you look at gross power. Finally, its important to on-line wash regularly after a compressor clean (either off-line or hand clean), as once the dirt is adhered to the blade and vanes for too long, on-line washing has minimal affect.
One warning about walnut shells (or rice hulls or whatever); they are solids and solid particles get into bleed air and devices that work off of compressor or bleed pressure. The precaution is to close off all bleeds possible and in some cases, if certain bleeds can't be isolated, the use of solid cleaners is questionable. It is one reason that online water washing came into vogue.
Walnut shells and rice and so forth are no longer recommended (though they work well). My experience with on-line washing is that you don't see an immediate change following the wash. On-line washing slows the performance degradation due to compressor fouling.
Off-line washing, on the other hand, restores the performance lost from compressor fouling.
If you had two turbines side-by-side and only on-line washed one of them, you'd see a difference in compressor fouling rate.
![[lol]](/data/assets/smilies/lol.gif "[lol] [lol]")
