GB1027937A - Improvements in and relating to screw rotor compressors - Google Patents

Abstract

1,027,937. Rotary compressors. SVENSKA ROTOR MASKINER A.B. Oct. 31, 1962, No. 41146/62. Heading F1F. In a positive displacement rotary compressor of the intermeshing screw type comprising a casing 14, Figs. 1 and 2 (not shown), closed at its ends by end walls 16, 18 and having a pair of intersecting bores mounting male and female rotors 10, 12 with the male lands being substantially convex and lying outside the p.c.d. and the female lands substantially concave and lying mainly inside the p.c.d., liquid is injected into the casing at the intersection of the bores through ducts 38 to seal and cool the compressor at a rate so that the mass flow of the liquid to the mass flow of the elastic fluid is at least in the ratio of 1À5 to 1 and the ratio increases in inverse proportion to changes in the tip speed of the rotor. The liquid is supplied through a valvecontrolled duct 34 and after passing through the ducts 38 passes between the rotors and hits a splash plate 42 and then passes around the casing wall. Increase in liquid supplies increases compressor efficiency, but at the same time increases cost of pumping equipment. Also, at high tip speeds with a large amount of liquid, churning occurs resulting in losses. A minimum ratio of 1À5 to 1À0 ensures that the operating temperatures, when hydrocarbon liquids are used, does not exceed the accepted safety standards.