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WORKING OF ROOTS BLOWER

Rotary positive displacement machines are generally uncooled and the compression is largely adiabatic. These are two types :

Roots blower and vane -type compressor.

ROOTS BLOWER :



Roots blower is an extension of the idea of a gear pump, popular in engines for pumping oil. There are two lobes on each rotor, and their shape is of cycloidal or involute form. One of the lobes is connected to the drive and the second is gear driven from the first , the two rotating in opposite directions. Very small clearances between lobes and between the casing and the lobes are provided to prevent leakages and to reduce wear. Four times the volume between the casing and one side of the rotor will be displaced in each revolution of the driving shaft. As each side of each lobe faces it side of casing a volume of gas V, at pressure p1, is displaced towards the delivery side at constant pressure. A further rotation of the rotor opens this volume to the receiver, and the gas flows back from the receiver, since this gas is at high pressure. The gas induced is compressed irreversibly by that from the receiver to the pressure p2, and then delivery begins. The process is carried out four times per revolution of the driving shaft. 




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