Introduction of Common Mechanical Vapor Recompressor
The common vapor compressor mainly includes Roots compressor, axial flow compressor, centrifugal fan and centrifugal compressor. The Roots compressor is mainly used for small-flow working conditions, and the axial flow compressor is used for big-flow working conditions and commonly designed as the multi-stage system. The commonly used vapor compressor is the centrifugal fan and the centrifugal compressor. The centrifugal fan can be used for the working condition with a low compression ratio (maximum Π=1.25). The same as the centrifugal compressor, air enters the inlet of impellers along the axial direction and flows out along the radial direction under the action of centrifugal force. The impellers and the shell of the fan both have a welding plate structure and should be strengthened by reinforcing ribs if necessary. Because the needed rotary speed of the impellers can be realized by the driving system, the transmission gear box is unnecessary in general. The single-stage centrifugal compressor mainly features compact arrangement of overhung impellers, compressor and gear box. The motor, gear box and the compressor are arranged on the same foundation in general. The shell of the compressor adopts the casting or welding structure. Because the speed at the high impeller end is more than 400m/s, the impellers are highly stressed, and the impellers are made of high quality materials such as chromium-nickel steel or titanium alloy. The multi-stage centrifugal compressor is used for working conditions with big-flow and high-saturation vapor temperature rise. The multi-stage centrifugal compressor is formed by placing many stages of impellers on the same axis. After leaving one stage of impeller, air passes the channel between the diffuser and the stage of impeller and then enters the next stage of impeller. The impeller shaft rotates on a bearing in the shell and is driven by an independent bevel gear. In order to improve efficiency and avoid unbearable high temperature in the shell, water can be filled into the channels between the stages of impellers. In order to exceed the pressure ratio of Π=10, the single-stage machines can be connected in series. If the impellers are driven by a central driving device with a plurality of small gears, it can be called two-, three- or four-impeller compressor.