I'm sure GE considers any pics of almost anything proprietary, I would too if it were one of my engines. Probably not a good idea to post much of anything unless you get permission. Yea, as the air goes thru the compression process it heat up pretty quickly in the higher speed stages. Folks think of temperature as being added in the combustor, but the air leaving the compressor in these high pressure ratio engines is generally above between 1,000 to 1300 F, and the materials in the back of the compressor are generally very high temperature alloys that you would generally think of as a turbine alloys. If there is enough moisture in the core flowpath you will go thru a temperature range where icing can occur and provided you have enough water in the flowpath you can go through a range where ice could form.. Given that you have to go through that temperature range, it kinda surprises me that we haven't seen more of this specific problem before. As with everything else there are limits. Engine guys have been pushing up bypass ratios with every generation of engines to improve fuel consumption since bypass ratio is the biggest driver for specific fuel consumption. With the architecture that GE is using, the LP compressor gets lower tip speeds and that simply lowers the amount of work and temperature gain in the LP compressor. For that reason they push the diameter of the LP compressor up, and this sticks the LP up to a diameter that is even bigger than the fan hub and you get a situation where pretty much anything that passes thru the first third of the fan diameter is going to go through the core. Couple that with the lower speeds and lower temperature rise and there may just be a limit as to how far you can go with a given architecture. As I said the RR engine has a higher speed IP since it isn't connected to the fan and can run at much higher rpm. This results in higher pressure ratio in the first stage of the IP and I would guess that they can get through the icing range in one stage. The Pratt geared fan has the same advantage in that their LP compressor is running at higher speed and that lets them bring down the diameter, and do the same thing. Here is picture of the RR Trent. Draw an imaginary line along the fan spinner and you can see that it pretty much intersects with the splitter leading edge. Add the fact that there are no vanes between the fan and the splitter and it is pretty obvious that most anything that is not vapor is going to get centrifuged out of the fan duct. That means that any water droplets or ice crystals are going out the fan duct. That approach tends to preclude problems like this although it's probably not impossible. Engine manufactures also want lower FOD and less stuff going into the core is pretty much goodness. Image Unavailable, Please Login
