A quick question on compressors
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?
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