Patent GB-464475-A (GB)
Title: Improvements in rotary engines
IPC: F01C21/00
Filed: 1935-10-16
Abstract: 464,475. Meshing-screw engines; gas turbines. AKTIEBOLAGET MILO. Oct. 16, 1935, Nos. 28615, 28616,'and 28617. Convention dates, Oct. 16, 1934, Oct. 16, 1934, and Feb. 12,1935. [Classes 110 (ii) and 110 (iii)] The engine or compressor comprises two or more screws 12, 14, one rotor 12 of a pair having threads which extend into helical recesses in the smaller rotor 14, there being no contact between the rotors, which are not lubricated. The pitch circle coincides with the outer circle of the rotor 14. The rotor shafts are geared together at the delivery end by gears 42, 46, which, preferably, have helical teeth. The L.P. end of the apparatus (when used as a compressor) is sealed by labyrinth packing rings 58, to which fluid from the H.P. end is led by way of an inlet 66. This fluid exerts a pressure to the right on a disc 60, to counter-balance the axial thrust on the delivery end of the rotor. A similar packing and balancing arrangement 113, is provided on the suction end of the second rotor. Oil throwing rings 48, 50, at the L.P. end, and 54, 56, at the H.P. end, prevent leakage of lubricant supplied to the bearings. Similar rings are attached to the second rotor shaft. Cooling liquid for the rotors enters tubes 76, 118, by way of nozzles 84, 86, flows to the left-hand end, and returns outside the tubes to a space 94 having an outlet 96. The space 94 is screened from the bearings 40, and gearing, by a partition 97. The casing has a cooling jacket 124. Fluid under pressure (after being cooled) is led through a tube 122, to the space 120, to prevent heated delivery fluid from leaking in from the compressor. Fig. 5 shows the rotors provided with triple threads of a constant pitch, but the latter may diminish towards the outlet to secure compression. Means to secure compression in the compressor illustrated, Figs. 5, 6, comprises a narrowing down of the outlet orifice by inserted plates 142, 144, which may be slid by spindles 150, 160, to alter the outlet area. Inset pieces 164, 162, prevent turbulence of the fluid passing to the outlet 130. For packing purposes radial and peripheral ribs are formed on the end faces of the rotors, and the top of the thread may have a number of ribs arranged upon it. In a second arrangement, conical-shaped rotors are fixed to shafts which incline towards one another at the delivery end. To allow for expansions due to heat, the housing of the bearing at the delivery end, may be supported on radial pegs screwed in the casing. Plain bearings may be used for the rotor shafts, in addition to ball and roller bearings. The profiles of cross-sections of the two meshing threads on the rotors are built up of arcs of circles with centres lying on the inner and outer circles of the two rotors. Fig. 17 shows an arrangement in which the rotor 410 has three approximately circular-cross-sectioned threads, and the second rotor has corresponding recesses. Inlet and outlet ports 462, 464, respectively are provided. The inlet is extended by cutting the casing to the dotted lines 510, 514, 512. In order to counteract the effect of an increase in pressure being given to the fluid from the commencement of opening to the complete opening of the delivery port, the outlet section is designed for a delivery pressure which is slightly lower than that desired finally. Fig. 15 shows a compressor 326 according to the invention, which is driven by a gas turbine 342. Air is sucked in at 348 and delivered through a pipe 350 to a combustion chamber 352 into which fuel is supplied by way of nozzles 354, 356. After combustion the gases are led through conduits 358, 360 to the turbine 342, and a second turbine 362 which drives an electric generator 366. The combustion chamber and conduits 358, 360, are double walled, so that a portion of the compressed air may be passed around the combustion chamber and the conduits. In a modified plant, an engine and a compressor may both be of the meshing screw type according to the invention the engine having expanding spaces through the threads. An outlet may be provided for fluid trapped by a thread entering a recess in the second rotor. Specifications 464,493 and 464,494 are referred to.