I'd point you to the wiki, but I (re)wrote it and even I don't understand it.Ooo
Ah, wait. Blade material *totally* matters. Tungestensteel blades with a small rotor is 10,000L/sec. Too much ?
I'm not at home so I apologize if all this is wrong.
For a small rotor, I think you just want to divide that number by 20 to get optimal flow. In this case, 500. Another way to get it is ToolSpeed (10) * SizeMultiplier (1) * 50 = 500.
So this might be an ideal rotor if you're producing 500 L/t steam (although there are probably "regular" rotors that also work at 500 L/t and would gain an efficiency bonus at the cost of durability)