864,526. Gas turbine plant. RICHARDSONS WESTGARTH & CO. Ltd. July 10, 1957 [July 12, 1956; Aug. 9, 1956; Sept. 3, 1956], Nos. 21603/56, 24435/56 and 26947/56. Class 110(3). A gas turbine installation having a turbinedriven main compressor system and, in addition, a reversible gas turbine drive comprising two turbines connected to the same shaft, one for driving the shaft in one direction and the other for driving the shaft in the other direction, is such that one of the turbines acts as a compressor or blower when the other turbine is supplying the driving power and the turbine employed as a compressor or blower has its discharge connected to the other turbine of the reversible drive or to the compressor system to augment their gas flow. In the arrangement shown, Fig. 1, compressed air from a compressor 14 is heated by the turbine exhaust gases in a heat-exchanger 16 before passing to a combustion chamber 18 supplying combustion gas to turbines 12, 22, 24 arranged.in parallel. The turbine 12 drives the compressor 14. The turbine 22 drives the propeller 28 in the ahead direction and the turbine 24 in the astern direction. The gas for driving the turbines 22, 24 is controlled by the valves 32, 34. In the position shown the valve 32 admits gas to the turbine 22 which drives the ship ahead. At the same time, the turbine 24 acts as a compressor or blower and delivers part of the exhaust gas from the turbine 22 through the valve 34 and sea water cooler 36 into an intermediate stage of the compressor 14. When it is desired to drive the ship astern, the positions of the valves 32, 34 is reversed and the valve 38 opened. The turbine 24 then drives the propeller and the turbine 22 acts as a blower which discharges to atmosphere through the valve 38. In the arrangement shown in Fig. 2, the astern turbine 24 is preferably designed for efficient operation as a compressor. The gas delivered by the turbine 24 when it acts as a compressor is admitted to an intermediate stage of the turbine 22. The combustion chamber has two fuel supplies 40, 42. The supply 42 is controlled by a valve 45 actuated by a governor 44 which also operates a throttle valve 46 in the air supply to the combustion chamber. To obtain high efficiency, the compressors 48 and 52 are maintained at constant speed and under full load by the governor 44. When the speed of the ahead turbine is reduced by opening the by-pass valve 56, the governor 44 will shut down the valves 45, 46. This causes the discharge pressure of the compressor 52 to rise and lift the spring- loaded valve 58 so that air is passed to are. cuperation turbine 60. The supply to and discharge from the turbines 22, 24 is controlled by rotary valves 64, 66. The pipe leading from the valve 66 to the intermediate stage of the turbine 22 may be provided with a non-return valve or with a valve or throttling device automatically controlled by the pressure of the air delivered by the turbine 24, or the pressure of the air in the intermediate stage of the turbine 24, or the difference of these pressures or the speed of the turbine shaft. Instead of providing two fuel nozzles in the combustion chamber 18 a second combustion chamber 70 may be provided between the turbines 54, 22. In a modification, Fig. 5 (not shown), the invention is applied to a closed circuit gas turbine plant, heated by oil or a gas-cooled nuclear reactor or other device supplying heat by atomic reaction or fusion. In this arrangement, the air from the astern turbine 24 acting as a compressor is fed through a non-return valve to the recuperation turbine 60.