Gas turbine engine control system

#The invention relates to an apparatus and method for controlling a gas turbine engine.

#It is conventional to use various non-dimensional parameter groups in the characterisation and control of gas turbine engine performance. The use of such dimensionless groups reduces the large number of parameters which determine gas turbine engine performance to a smaller number of dimensionless parameter groups.

#An important dimensionless parameter group relates to the engine speed. This “corrected” speed is commonly used for indication and control of engine power or thrust on some engines; and for controlling engine variable geometry features, such as variable compressor stator vanes.

#An embodiment of the invention will be described for the purpose of illustration only with reference to the accompanying drawings in which:—

#FIG. 1 is a diagrammatic sectional view of a conventional ducted fan gas turbine engine;

#FIG. 2 is a diagrammatic sectional view of a turbofan engine incorporating control apparatus according to a first embodiment of the invention;

#With reference to FIG. 1, a gas turbine engine generally indicated at 10 comprises, in axial flow series, an air intake 12, a propulsive fan 14, an intermediate pressure compressor 16, a high pressure compressor 18, combustion equipment 20, a high pressure turbine 22, an intermediate pressure turbine 24, a low pressure turbine 26 and an exhaust nozzle 28.

#The gas turbine engine 10 works in the conventional manner so that air entering the intake 12 Is accelerated by the fan 14 to produce two airflows, a first airflow into the intermediate pressure compressor 16 and a second airflow which provides propulsive thrust. The intermediate pressure compressor 16 compresses the airflow directed into it before delivering the air to the high pressure compressor 18 where further compression takes place.

#The compressed air exhausted from the high pressure compressor 18 is directed into the combustion equipment 20 where it is mixed with fuel and the mixture combusted. The resultant hot combustion products then expand through and thereby drive the high, intermediate and low pressure turbines 22, 24 and 26 before being exhausted through the nozzle 28 to provide additional propulsive thrust. The high, intermediate and low pressure turbines 22, 24 and 26 respectively drive the high and intermediate pressure compressors 16 and 18 and the fan 14 by suitable interconnecting shafts.