PPRuNe Forums - A quick question on compressors

Quote:

Also variable pitch stators need a large gap between rotor and stator blades (to allow them to alter pitch). I'm certainly no expert, but I'd have thought that that gap is less than ideal. Surely you'd want the stator and rotor blades as close as mechanically possible?

If you look at an engine cut-a-way you will see that both the stators and the rotor disk blades are cantilevered or fixed at one end.

In a compressor surge the blades and partly the rim of the disk bounce forward and can clip the back of the stationary vanes if there is not enough clearance for this phenomena.

Then again the stationary vane assembly innards features may deflect fore and aft due to thermals or vibratory modes. Thus the need for suitable gaps