Roots Blower Working Principle: Step-by-Step Mechanical Guide

Understanding the Roots Blower Working Principle is fundamental for process engineers selecting equipment for aeration, gas boosting, or material transport. A Roots blower operates as a positive displacement rotary lobe machine.

Step 1: Suction Phase

As the two synchronized rotors rotate in opposite directions inside the figure-eight casing, air or gas enters through the inlet port into the volume between the rotor lobes and the casing wall.

Step 2: Isochoric Transport (No Internal Compression)

Unlike screw or reciprocating compressors, a Roots blower does not compress gas internally. As the lobes rotate past the suction opening, a fixed volume of air is trapped and carried around the perimeter to the discharge port without changing its volume (isochoric transfer).

Step 3: External Backpressure Discharge

When the rotor lobe uncovers the discharge port, the trapped gas meets the system backpressure in the discharge piping. Gas rushes back into the pocket, equalizes pressure, and is forced out by the advancing rotor lobe.

The Role of Precision Timing Gears

High-precision hardened timing gears mounted on shaft ends synchronize the two rotors so that they maintain microscopic clearances without ever touching each other or the casing. Because there is no metal-to-metal contact inside the air chamber, no internal lubrication is required, delivering 100% oil-free air.

Twin Lobe vs Tri Lobe Working Principle

In a Twin Lobe Blower, air is discharged 4 times per shaft revolution. In a Tri Lobe Blower, air is discharged 6 times per revolution, which drastically reduces discharge pressure pulsations and acoustic noise.

Have questions about flow calculations? Speak with our technical engineers.