🔍 Key Concepts

• Examine the shape of the rotor lobes and how they must mesh without collision • Think about the direction of gas flow through the blower housing (from suction to discharge) as shown by the casing passages • Consider how counter-rotating gears normally drive paired rotors in a rotary (Roots-type) blower

💭 Think About

• If gas enters at the labeled inlet and exits at the outlet, which way must each rotor sweep the trapped pockets of gas along the casing? • Looking at the points where the two rotors nearly touch, in which rotation sense will the lobes roll past each other without intersecting? • Imagine turning rotor A clockwise: what must rotor B do (clockwise or counterclockwise) to keep the clearances the same at all contact points?

✅ Before You Answer

• Verify where the inlet (low-pressure side) and discharge (high-pressure side) are in the illustration • Trace one trapped pocket of gas between a lobe and the casing and follow it around the casing in the direction that moves it from inlet to outlet • Confirm that the chosen directions let the lobes mesh without crossing through each other anywhere in the rotation