How to calculate the maximum mass flow through a subsonic compressor?
 

When a throttle valve is fully opened, is the outlet static pressure necessarily equal to the ambient pressure?

I set the following BCs to calculate the maximum mass flow through a subsonic compressor.

Am I doing it right?

At inlet:
Total pressure 101,000 Pa
Total temperature: 286 K

At outlet:
Static pressure 101,000 Pa

I assume you mean the outlet of the throttle valve discharges into atmosphere through an open pipe end or similar.

In that case, assuming the end of the pipe is at the static pressure of ambient is usually a good approximation. If you want high accuracy or are concerned about end effects then you should model the outlet details and move the boundary to somewhere you know the conditions.

As for your proposed boundary conditions: You should set a reference pressure of 101kPa and then you have a total pressure inlet of 0 Pa and an outlet of 0 Pa.

But I think you will find a device with no pressure difference across it will have no flow, so it won't be a very interesting simulation.