Compressors, continuous-flow centrifugal

Continuous-flow compressors. a. Centrifugal compressors h. Axial flow compressors... 

Compressors A compressor is a device that pressurizes the air in a gas turbine. It transfers energy by dynamic means from a rotating member to the continuously flowing air. The two types of compressors used in gas turbines are axial and centrifugal. Figures 29-25 and 29-26 depict typical industrial gas turbines. 

In much the same manner as pumps, compressors are classified as one of two general classes positive displacement or dynamic (see Figure 3-68) [23]. These two general classes of compressors are the same as that for pumps. The positive displacement class of compressors is an intermittent flow device, which is usually a reciprocating piston compressor or a rotary compressor (e.g., sliding vane, screws, etc.). The dynamic class of compressor is a continuous flow device, which is usually an axial-flow or centrifugal compressor (or mix of the two). 

Centrifugal fans, blowers, and compressors are widely used in chemical processes because they produce a continuous flow, are relatively small, and are free of vibration. Because gases are compressible, the temperature difference between the compressed gas and the feed gas is significant at even moderate compression ratios and may limit the compression ratio possible in a single stage. However, the need for multiple stages in centrifugal compressors is usually dictated instead by impellor rotation-rate limitations, which limit the compression ratio that can be achieved. 

The slurry flows continuously into the first gas-phase reactor (GPR) (3). Reactor gas is circulated at high speed by a centrifugal compressor through a distribution grid. A cooler on the circulation gas... 

For a dynamic compressor, a continuous totfUtng element (rotor) js used to increase gas velocity. Then, gas velocity is converted to static pressure at compressor outlet. Dynamic compressor is classified as centrifugal or axial compressor. For centrifugal compressor, the rotating element is an impeller, and gas flow is in either radial or mixed flow direction. For axial compressor, the rotating element is a bladed rotor and gas flow is in the axial directioa... 

The symptoms of surge are pulsating pressure, rapid flow reversals, a drop in motor current and a jump in turbine speed. Continuous, rapid flow reversals can cause severe damage to the compressor. In axial compressors the blades may touch, resulting in instant destruction. However, centrifugal compressors are more mgged, and only seal damage results [15]. 

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