ENGINE AIR/GAS FLOWPATH WASHING IS ONE OF THE MOST IMPORTANT CRITERIA OF ITS EFFICIENCY MAINTENANCE
Evgeny Vakhrushev
Engineer, Operation Department, Aviadvigatel OJSC
Gas turbine operation is connected with consumption of very large air volume. During operation the air necessary for operational cycle undergoes thorough cleaning. Nevertheless, the air contains particles of oil, sprays, soil, salts and organic substances, which adhere to engine air/gas flowpath parts - especially on compressor airfoils. As a result, compressor efficiency decreases, operating temperature and fuel gas consumption increase, engine output power declines, emission of harmful substances rises.
The necessity of compressor airfoils cleaning was recognized long ago. Today three basic methods of engine cleaning are applied. One of them is engine disassembly and teardown. This method is efficient, but it is expensive and involves engine removal and its transit to the plant. For a long time between shop repairs the engine will be operated with lowered operating parameters.
Fragment of engine inlet guide vanes before and after compressor washing. Gas turbine generating set of Prirazlomnoe oil and gas field.
Another method is connected with inlet of different abrasive materials into the running engine. Application of this method inevitably results in failure of barrier coating at compressor airfoils and components surfaces. That's why now this method is not used for modern engines. The best method of engine cleaning is its regular washing. It is a simple and quick procedure, during which washing solution and distilled water are injected under pressure to the engine air/gas flowpath by a special washing device. It should be noted that washing can be carried out both at running engine and during cold cranking. Both variants have their own advantages.
Washing at cold cranking is of higher quality. The washing solution stays longer on a cleared surface and larger inner surfaces of engine are cleared. The advantage of washing at a running engine is the quickness of this procedure. It is not necessary to stop the engine.
Washing efficiency important factors are its regularity, compliance with the procedure and washing liquids type. Time between washings is determined by different factors: region of operation, air pollution concentration, fuel quality and many others. But the main aspect is the acceptable level of engine power reduction.
Different types of washing liquids are applied for washing of engine air/gas flowpath parts. The variety of liquids offered for application is enormous.
Among dealers - mainly foreign manufacturers - there is a severe competition for the market. But not all liquids can be used without primary tests of washed item parts for corrosion resistance.
Certainly timely air/gas flowpath washing provided parameter recovery practically to log book values during 50,000 hours.
At the moment one of such engines is being tested at Perm Engine Company. The test results will be used to determine concrete liquids for washing of air/gas flowpath of gas turbines based on D-30 engine.
