Spinning reserve with inlet throttling and compressor recirculation

1,151,200. Gas turbine plant. GENERAL ELECTRIC CO. Nov. 9, 1966 [Dec. 15, 1965], No.50171/66. Heading F1G. A method of operating a gas turbine-generator set in standby reserve comprises driving the turbine 3 using the generator 4 as a motor, throttling inlet air to the compressor 1, and extracting compressor air from a higher pressure point and recirculating it through a line 14 to a lower pressure point, to thus reduce the air-flow to the combustion chamber 2 and turbine. The method enables the turbine inlet temperature to be maintained at a high value ready for instant power generation without thermal shock, with minimum fuel supply to the combustion chamber and without surging of the compressor. A valve 15 controls the degree of recirculation which may be between 20 and 45% of the total air-flow through the compressor. The throttle valve 13 in the inlet conduit 6 reduces the compressor inlet pressure to between “ and 1/ 5 atmospheric pressure. In modifications, the turbine 3 is connected to generator 4 through a reduction gear or the generator is connected to a separate turbine in flow series with the compressor driving turbine.