- #1

guss

- 248

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Let's say I have a precisely designed axial compressor, comprising of stages of rotor and stator wheels, that resembles something like this:

Such a compressor, driven by a certain torque at a certain RPM, will deliver a certain air mass per time at a certain pressure. Now, what happens if the compressor is scaled down, so that the diameter is half of what it used to be but all other angles, etc. remain the same? The RPM will be such that the speed of the blade tips is the same in both compressors, i.e. the RPM will be higher in the smaller engine.

My intuition and some quick calculations tell me that the pressure ratio will remain the same, the mass flow will be divided by 4 (since cross sectional area is divided by 4), and the torque will be divided by 8 (since I think power will be divided by 4 and RPM will be doubled). But, again, I'm not sure, and I'd like to be. Can anyone help? Thanks!

Such a compressor, driven by a certain torque at a certain RPM, will deliver a certain air mass per time at a certain pressure. Now, what happens if the compressor is scaled down, so that the diameter is half of what it used to be but all other angles, etc. remain the same? The RPM will be such that the speed of the blade tips is the same in both compressors, i.e. the RPM will be higher in the smaller engine.

My intuition and some quick calculations tell me that the pressure ratio will remain the same, the mass flow will be divided by 4 (since cross sectional area is divided by 4), and the torque will be divided by 8 (since I think power will be divided by 4 and RPM will be doubled). But, again, I'm not sure, and I'd like to be. Can anyone help? Thanks!

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