In multiple vane type compressors, the axis of rotation coincides with the centre of the roller (O); however, it is eccentric with respect to the centre of the cylinder (O’) as shown in Figure 10.8. The rotor consists of a number of slots with sliding vanes. During the running of the compressor, the sliding vanes are held against the cylinder due to centrifugal forces. The number of compression strokes produced in one revolution of the rotor is equal to the number of sliding vanes, thus a four-vane compressor produces four compression strokes in one rotation.
Figure 10.8 Multiple Vane Type Rotary Compressor
In these compressors, sealing is required between the vanes and cylinder, between the vanes and the slots on the rotor and between the rotor and the end plate. However, since pressure difference across each slot is only a fraction of the total pressure difference, the sealing is not as critical as in fixed vane type compressor. This type of compressor does not require suction or discharge valves; however, check valves are used on discharge side to prevent reverse rotation during off-time due to pressure difference.
Leave a Reply