Patent GB-977324-A (GB)
Title: Improvements relating to supercharges
IPC: F02B37/18
Filed: 1961-01-03
Abstract: 977,324. Charging four-stroke engines; regulating gas-turbine plant. GARRETT CORPORATION. Jan. 3, 1961 [Jan. 4, 1960], No. 268/61. Headings FIB and F1G. [Also in Division G3] An engine 1, Fig. 1, e.g. a diesel engine, is supercharged by a compressor 5 driven by an exhaust-gas actuated turbine 7 across which is bypass 13, 14 embodying a valve 15 controlled by a device 18 subjected to the compressor inlet and outlet pressures supplied to ports 22 and 19, respectively, to control the compressor pressure-ratio. Within the device 18 are diaphragms 32, 33, Fig. 2, defining chambers 34, 35 and 36, the latter housing an evacuated bellows 37 connected between the device housing 31 and the outer diaphragm 33. The inner diaphragm 32, which is guided for axial movement without rotation by a finger 44 on a cup 42, is connected by a stem 47 to a control valve 48 seating on the inner end of a passage 51; a resilient bellows 53, which normally urges the valve 48 onto its seat, has its interior open to the passage 51 whereby the fluid forces on the valve 48 are balanced. The control valve 48 connects through a passage 56 with the chamber 34 in turn leading to the port 22 via a passage 57 also connected to the chamber 35 through a restriction 58; the chamber 36 is open to the port 19 by a passage 61. At the opposite end of the device 18 are two further diaphragms 62, 63 forming chambers 64, 65, and 66, the latter communicating with the passage 51 via a further passage 69; a spring 72, which abuts the closed end of a cup member 67 attached to both diaphragms 62, 63, urges the bypass valve 15 to the closed position, the stem 16 of this valve being attached to the member 67. Chamber 64 is fed directly from the port 19; chamber 66 is connected to the passage 61 by a restriction 73 and chamber 65 is open to the port 22 via a restriction 74. With the engine at rest the bypass and control valves are spring-urged to their seats; when the engine is running the compressor outlet pressure appears directly in chamber 64 and since the valve 48 is closed this pressure passes through the restriction 73 and builds up in chamber 66 but since diaphragm 63 is of greater effective area than diaphragm 62 the net result is an increase in the closing force on the bypass valve 15 in opposition to the exhaust gasses in conduit 13 acting directly on the valve and tending to open it. The diaphragm 33 is urged rightwardly by the pressure differential on the bellows 37, and leftwardly by the compressor outlet pressure in chamber 36 acting on the diaphragm; when the compressor ratio has reached such a value that the latter force predominates, the diaphragm 33 moves to left and forces diaphragm 32 in the same direction so unseating the valve 48 and opens chamber 66 to the port 22 whereupon the bypass valve opens under the combined forces of the exhaust gas acting directly thereon and the compressor outlet pressure in chamber 64. The turbine speed reduces until the compressor ratio reaches a given low value when the diaphragm 33 moves to close the valve 48 to re-establish the previous pressure conditions in the various chambers and close or tend to close the bypass valve 15. Continued operation of the bypass valve maintain the compressor ratio constant. The device 18 is arranged to provide fail-safe conditions should any of the diaphragms rupture; the bypass valve acts as a relief valve upon loss of compressor outlet pressure.