Did a search on compressor washes, but only came up with plane spotter type info.
Can anyone give a link to the procedure for a compressor wash on a med to large turbofan engine. ie how its conncected, where, how it cleans the blades and removes what I would think was baked on contaminants.
Was asked a question today about it and couldnt give more than a basic answer.
An aditional question from myself is, to large jet engines have a gallery fitted as part of the engine for such compressor washes. I did notice a compresor was clip on youtube that showed a Citation with a hose pointed at the N1 fan.
Can one overdo compressor washes, ie if you did one after each flight, can it actually damage the engine.
Also, does any one know if this is fact or fiction. years ago I was told that the for the Mirage 3, several kilos of crushed walnut shells was thrown down the intake as the engine was dry spun. The shells being abrasive enough to remove the contaminants, but soft enough to do damage.
We use it for the Trent and GE90 engines and it does work! It cleans the compressor improving the efficiency resulting in a reduced fuel burn and recovering EGT margin. It works simply by the fact of the blades paddling around in a water flow (bit like a washing machine!). No special gallery, but we use a rig that clips behind the fan that sprays (hot) water directly into the compressor section during a dry motor. The only additional work is to disconnect some of the sense lines to the FAEC/EEC to prevent water contaminating the electronics/bellows. Nothing to be gained by doing it after every flight.
...I was told that the for the Mirage 3, several kilos of crushed walnut shells was thrown down the intake as the engine was dry spun. The shells being abrasive enough to remove the contaminants, but soft enough to do damage.
Not so sure about doing that with an axial flow compressor, but a centrifugal compressor could certainly be cleaned that way.
The average plane spotter might well know more about compressor washes than I do. All I know is what I have seen in a documentary on engine maintenance at Lufthansa Technik's on DVD. It shows a bloke lowering what I think is a compressor casing into a basin. Reading from a manual, he eplains they were applying some alkaline rust remover for 15 to 60 minutes to remove "Zunderpartikel" (cinder particles?). The part was washed and then immersed in potassium permanganate to turn oil carbon into manganese oxides.
Fan engines are more diicult to clean than non-fan turbojets.
The spinning fan acts as a centrifugal separator and throws most of the water and junk outward away from the core as intended by the design for rain and hail (that's another story)
The means of overcoming this in ground operation is to position the nozzles just outboard of the spinner to remove spinner bounce-off effects and to adjust the fan speed and water nozzels so that the water velocity has a chance to pass through the fan into the core compressors. all this falls under Newtonian physics, a law available for free to everybody (patent applications may disagree)
Not just for large turbofans, compressor washes used to be carried out on the L1011 Tristar APU regularly too. Detergent/water mix was introduced via a connector on the compressor inlet plenum by means of a stirrup pump during a dry cycle and then left to soak. A full start and run would then be done. Performance recovery tended to vary, especially on "tired" units. The procedure seemed to be unique to the L1011 at that time (late 80's to early 90's), can't remember doing anything similar on contemporary aircraft.
There used to be a cleaning agent id'd B&B3100 - a petroleum-base cleaner - that we used on small engines. Spray it in while cranking, let it soak static for a time, then rinse with clear de-ionized water.
We did some tests to evaluate the soak time - up to 12 hours. Sometimes it helped, sometimes not.
I believe its use was discontinued re environmental concerns.
I worked nearly 14 years in an engine overhaul facility but somehow or other failed to witness a single compressor wash. But it was commonly used in the test cell. Often post refurbishment, an engine might be a bit marginal. A simple compressor wash was often enough to restore the EGT margin and get the engine through the test. Sometimes the difference was remarkable.
Years ago when I flew helicopters off shore, (1969/70), we had to do a compressor wash after each flight with water, to get rid of any salt contamination. It was on the WS55/III Whirlwind with a single Gnome engine and a rig was used that fitted over the 'bullet', I think about once a week we did a 'wet' wash, i.e. engine running at idle and the wash was part water part kerosene, but I'm not certain about that last part.
We used to do engine washes on our 737-200s. Disconnecting the generator cooling duct and tying a plastic bag over the genny intake was the worst part. Them max dry motor and a bloke would stand about 3ft in front of the intake and blast it with a high pressure water hose. Only ever did it in the summer when the over night temp was warm enough. Leave it for a few hours to drain, reconnect the gen and light it up. No idea if it did any good as we were never privy to the figures before and after.
I am confused- you're saying that doing a compressor wash on a refurb engine improved it? Did they clean the parts on disassembly?
Ah, good point. I should have clarified. Not every engine going through a refurbishment is completely disassembled and rebuilt. There are different levels of refurbishment. Parts of the engine may be taken apart and go through the full process. Other parts my receive no more than a visual inspection, borescoping etc.
Also with modular engines, the customer may only need a specific module worked on. The others only receiving a visual.
So you're not always going to get a complete newly rebuilt and cleaned engine heading to the test cell. Hence the marginal results.
So it's not a case of shoddy maintenance from the company concerned. If anything it was the opposite. There was a tendency to exceed their brief with a subsequent impact on turnaround times and profits. But they're still in business so they're doing something right.
Most turbine engines require compressor washing at times.
I've been involved with the following engines and procedures:
Rolls Royce Dart - Crushed walnut shells with engine running. Quite spectacular at night with all the sparks out of the exhaust.
P & W PT-6 - detergent wash with engine running followed by water wash.
Allison 250-B17 - water wash with engine turned by starter motor.
General Electric CF-6 - Crushed coke running at flight idle. This required standing about 15 feet in front of the engine with a lance to direct the flow of coke into the core compressor. A bit scary the first time you do it even with a safety harness on.