[Exe]

Hello, nice to greet you.
I am writing to ask for help/advice.
I am working on my thesis, validating the design of a microturbine by finite elements. The goal is to find the best performing operating point and evaluate improvements.
For simulation, simplify into three domains, distributor, rotor and discharge tube.
I'm having trouble with the results.
By using mesh motion and giving it different rotation speeds, I obtain positive torques in the range of [0-90 r/s] and [90 - +140r/s] negative torques. I understand that in positive values, the flow does work on the turbine and in negative values, the turbine does work on the flow (it works as a pump). And at the point of zero torque is the point of optimal operation. It's right?
On the other hand, is there a possibility of calculating the torque based on the flow rate and thus obtaining the torque on the shaft, as seen in the last image?