1433467 Gas turbine engines-control GENERAL MOTORS CORP 25 July 1974 [6 Aug 1973] 32821/74 Heading F1G The invention relates to a gas turbine plant comprising a compressor 3, an air pre-heater 6, combustion equipments 8, and a turbine 12 which drives the compressor and an output shaft 15, the arrangement being such that the compressor may alternatively be driven by the output shaft. A valve 34 is disposed in the line 4 between the compressor and the air pre-heater, the valve being normally closed but being openable so that air passes directly from the compressor to the combustion equipment. The valve 34 is opened when the fuel supply is reduced so that unheated air passes to the combustion equipment and turbine. Alternatively or in addition a similar valve 36 is connected in line 37 leading to atmosphere whereby upon opening of the valve 36 air from the compressor is discharged directly to atmosphere. The plant shown is suitable for use in a road vehicle, the fuel supply being controlled by pedal 30; thus when the pedal is released and the turbine speed is above a predetermined value, the link 32 acts to close a contact 43, the contact 44 also being closed by a speed-responsive device 47 whereby the solenoids 39, 40 are energized to open the valves 34, 36. The power shaft may alternatively be driven by a separate power turbine but means are then provided to connect the power turbine to the compressor so that the compressor acts as a brake for example when the vehicle is descending an incline and the output shaft is being driven by the road wheels. The object of the invention is to reduce immediately the power of the turbine when the fuel supply is reduced to idling power since normally air would continue to flow through the air pre-heater and the heated air passing to the turbine would continue to generate power.
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