Patent ID: 8740548

Claim:
A gas turbine engine compressor variable stator vane arrangement comprising: a gas turbine engine including: a gas turbine engine compressor; a compressor rotor, a compressor casing, and at least one stage of variable stator vanes, the at least one stage of variable stator vanes being pivotally mounted in the compressor casing, an actuating arrangement arranged to rotate stator vanes of the at least one stage of variable stator vanes, a control arrangement comprising a first speed sensor arranged to measure a rotational speed of the compressor rotor, a temperature sensor to measure an inlet temperature of the gas turbine engine, a first pressure sensor to measure an outlet pressure of the gas turbine engine compressor, a second pressure sensor to measure an ambient pressure at an inlet of the gas turbine engine, a third pressure sensor to measure a total inlet pressure of the gas turbine engine, a processor configured to determine a current operating point of the gas turbine engine compressor from a measured rotational speed of the compressor rotor and a measured outlet pressure of the gas turbine engine compressor, and a comparator to compare the current operating point of the gas turbine engine compressor with a target operating line of the gas turbine engine compressor, and the processor further configured to adjust an angle of the at least one stage of variable stator vanes if the comparator determines that the current operating point of the gas turbine engine compressor is not on the target operating line of the gas turbine engine compressor, such that the current operating point of the gas turbine engine compressor is moved nearer towards or onto the target operating line of the gas turbine engine compressor, wherein, at idle conditions, the gas turbine engine compressor is simultaneously operating at the minimum required outlet pressure of the gas turbine engine compressor and at the minimum required rotational speed of the compressor rotor, wherein the target operating line corresponds to a ratio between the rotational speed and the outlet pressure of the gas turbine engine compressor, the target operating line including a point comprising the minimum required rotational speed and a minimum required outlet pressure.