🔍 Key Concepts
• Study how a Roots-type blower moves air: pockets of air are trapped between the rotor lobes and the casing, then carried around the outside from suction to discharge.
• At the suction side, rotor tips move away from each other at the port, increasing volume. At the discharge side, rotor tips move toward each other, decreasing volume and forcing air out.
• Use the given numbers: rotors 1 and 2 are gear‑driven in opposite directions, and areas 3 and 4 must be one suction and one discharge based on how air would logically flow.
đź’ Think About
• Look at the top opening (area 4) between the rotors. If rotor 1 turns clockwise, what happens to the space at that opening? Does the volume between the lobes there increase (suction) or decrease (discharge)?
• Now imagine rotor 1 turning the opposite way. Which combination of directions for rotors 1 and 2 allows continuous pockets of air to move smoothly from the top opening to the side chambers labeled 3, without trapping or blocking air?
• Once you know where air is being picked up and where it is being pushed out, match that with the answer choices that label area 3 and area 4 as suction or discharge.
âś… Before You Answer
• Verify which rotor directions do not cause the lobes to collide; the rotors must always rotate so the lobes pass close but never hit.
• Confirm at the port you decide is suction, the rotor tips are moving apart, creating more space; at the discharge port, they should move together, squeezing the air out into that passage.
• Before selecting an option, double‑check that the chosen rotor rotation provides a continuous path for air from the suction port around the casing to the discharge port.