Lufthansa Technik (LHT) is planning to enhance engine wash processes by using dry ice instead of water.
Turbofan engines can be cleaned on-wing to improve compressor efficiency and reduce fuel consumption and emissions. Water is sprayed into the inner fan area while the engine spools up with bleed air, with no fuel being injected. The contaminated water can then be collected from the engine exhaust stream and cleaned.
German MRO provider LHT says that employing solid CO2 dry ice pellets not only significantly cuts process time and water consumption, but also permits powerplant washing in winter.
Water-based engine washings are not conducted in air temperatures below 5°C (41°F), to avoid residual water from freezing inside the engine core. This would not be an issue with the 3x6mm CO2 pellets, which evaporate on impact with the engine components, without residue.
LHT says that some contamination on blades and vanes is mechanically removed due to the pellets' kinetic energy. But the dry ice particles' low temperature of -78.5°C also makes dirt brittle and thus helps to remove it without affecting component surfaces.
The MRO provider claims that the new method halves wash times compared with it water-based "Cyclean" procedure, and cuts them by up to 90% versus comparable processes by engine manufacturers. This allows more frequent cleaning of engines, and also covers medium-range aircraft with shorter ground times, says LHT.
The MRO provider's engineers developed the technique of employing dry ice pellets for engine washing via a joint research project undertaken since 2009 with Darmstadt university and Frankfurt-based air equipment specialist Pneumo.
The project - which was supported with German government funding - has now been concluded, with patents being registered in Europe and the USA.
LHT is now planning a follow-up project to assess further alternative blast media for engine wash processes.