Turbo compressor sizing

[dilbert]

I think there is an error in what I have said, previously.

I would have thought that the compressor inlet is large and it's outlet small, whereas the turbine inlet would be small, and it's outlet large.

As the exhaust gas flows past the turbine blisk, it imparts energy to the turbine, whilst expanding and cooling. Because the gas flows past the blisk for a finite distance, but the the blisk has a uniform angular velocity, the gas tract must expand, or the less energetic gasses would upset the free flowing nature of the turbine.

The reverse is true for the compressor.

I'd have thought that the the ratio of inlet and outlet tract sizes is fixed by the design of the blisk it's self. Surely this is why a turbo compressor is a one shot rotor and stator that are designed to go together.

I can't even see interchangability of blisks working, it's not just the size of the inlet and outlet, it's the size of the tract for it's whole length.

I could be wrong. I don't really know anything about tubine engines.