Patent GB-207779-A (GB)
Title: A process for the working of rotary compressor plant wherein the rotary compressor delivers into an intermediate receiver, and plant for carrying out the process
IPC: F04D27/02
Filed: 1923-04-19
Abstract: 207,779. Graemiger, B. Nov. 28, 1922. [Convention date]. Regulating.-In a rotary compressor plant delivering into an intermediate receiver a regulating apparatus is provided so arranged that it regulates with decreasing delivery volume to a lower pressure than the maximum pressure of the receiver so as to obviate uneconomical rise of pressure with decreasing volume and in the neighbourhood of the stability limit curve is automatically transposed so as to regulate according to a higher pressure. In apparatus shown diagrammatically in Fig. 2 a compressor A driven by a turbine B delivers into a receiver C through a non-return valve D. A throttle-valve K in the suction-pipe J of the compressor is actuated by a device L subjected through a pipe Q to the pressure in the receiver C. The turbine is supplied with motive fluid through a pipe 0 having a regulating valve M under the direct and indirect influence of a device N which is dependent on the pressure in the receiver C. A device H subject both to delivery pressure through the pipes E, S and also to the suction volume in the pipe J through a pipe T, actuates a blow-off valve G and when operating near the limit curve acts through a connection V to cause the device N to be adapted to a higher pressure. In the constructional form shown diagrammatically in Fig. 3 a device L for operating the throttle K comprises a piston 2, under the stress of a spring 3 and controlled through a pipe Q by the receiver pressure, and acting through connections on a distributing slide valve 7 enclosed by a sleeve 8 and having ports 10 - - 12, which sleeve moves in a casing 9 having passages 13 - - 15. The passages 13, 14 communicate with opposite sides of a servo-motor piston 19 operating the valve K and the passage 15 is connected to a pressure supply. When the delivery pressure increases the piston 7 is raised till at a certain point pressure is admitted through ports &c. 15, 12, 11, 13, to the space above the piston 19 which in descending moves the sleeve 8 through connections 25, 26 and opens the valve 7 further, causing the immediate, shutting of the valve K. An opposite sequence of events occurs when the pressure falls. The regulator N which acts on the turbine valve M comprises a centrifugal governor 31, a distributing valve 32 a servo-motor 33, and a relay lever 34 connected to the governor, the valve 32 and to a nut 37 mounted on a screw-threaded rod 38 on the servo-motor rod 39. The rod 38 is connected by spur gearing 40 - - 43 with an oil motor 44 the driving of which in one or the other direction effects the speed regulation. The driving of the motor 44 is regulated by an apparatus comprising a cylinder 45 in which is a spring-controlled piston 46 subjected' through a pipe R to the delivery pressure. The piston acts through a lever 50 to control a distributing valve 52 so that with increasing delivery pressure the oil motor 44 operates to reduce the supply of motive fluid and conversely. The regulating characteristic of the apparatus N is a straight line parallel to the volume axis, but when a point near to the stability curve is reached transposition of the regulation to a higher pressure is effected through the action of a piston 57 which shifts the fulcrum 53 of the lever 50. The piston rests normally in its lower position but is under the control of pressure communicated through pipes 78, 79 connected with the apparatus H which also actuates the blow-off valve G. This apparatus comprises a bell 62 dipping into liquid and connected by a pipe 63<1> to a volumeresponsive device 63 which in known manner produces a pressure in the pipe 63<1> proportional to the square of the suction quantity. A piston 64 is subjected to the delivery pressure through the pipe S and is connected to the bell 62 by rods 66, 67 and a lever 68 having a fixed fulcrum 69. The lever 68 is connected by a rod' 70 to a lerver 71 linked to a distributing-valve 72 and pivoted at 73 to the rod 74 of a servo-motor piston 75 acting on the blow-off valve G. At or just before the actuation of the blow-off valve the distributing valve 70 admits pressure through the pipe 79 to the underside of the piston 57 and thus effects the movement of the fulcrum 53 and the transposition before referred to. The space above the piston 46 may be connected by a pipe 200 to the. suction pipe beyond the throttle valve K so that on closure of the latter a partial vacuum is produced in the space above the piston with the same consequence in cutting off the motive fluid supply as would be effected by a rise of pressure. The effect produced by movement of the fulcrum 53 may also be produced by arranging the piston 57 to operate a valve connected with the space below the piston 46 to allow leakage therefrom when the critical point is reached. The regulating apparatus L and N may be combined so that a single piston effects the functions of the pistons 2 and 46. In a further modification the lever 50 is replaced by two levers connected by a link and interconnected with the sleeve of the speed governor 31 so as to produce a negative relay action, with the result that, until the neighbourhood of the stability curve is reached, there is a regulation corresponding to a fall of pressure with decrease of volume.