Miscellaneous Mechanical ComponentsDOE-HDBK-1018/2-93AIR COMPRESSORSThe rotary lobe-type, illustrated in FigureFigure 4 Rotary Lobe Air Compressor4, features two mating lobe-type rotorsmounted in a case. The lobes are geardriven at close clearance, but withoutmetal-to-metal contact. The suction to theunit is located where the cavity made bythe lobes is largest. As the lobes rotate,the cavity size is reduced, causingcompression of the vapor within. Thecompression continues until the dischargeport is reached, at which point the vaporexits the compressor at a higher pressure.The rotary liquid seal ring-type,illustrated in Figure 5, features a forwardinclined, open impeller, in an oblongcavity filled with liquid. As the impellerrotates, the centrifugal force causes theseal liquid to collect at the outer edge ofthe oblong cavity. Due to the oblong configuration of the compressor case, large longitudinalcells are created and reduced to smaller ones. The suction port is positioned where thelongitudinal cells are the largest, and for the discharge port, where they are smallest, thuscausing the vapor within the cell to compress as the rotor rotates. The rotary liquid sealcompressor is frequently used in specialized applications for the compression of extremelycorrosive and exothermic gasses and is commonly used in commercial nuclear plants as a meansof establishing initial condenser vacuum.Figure 5 Rotary Liquid Seal Ring Air CompressorRev. 0ME-05Page 5
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