US 5,687,564 A · Low rotor vibration avoidance in aircraft gas turbine engines

Abstract

Corrected fan speed (N1C2) and engine pressure ratio (EPR) are controlled, by controlling exhaust nozzle area (EA) according to a schedule or map so that as altitude increases (P2 decreases) the axial forces on the low rotor are sufficient to minimize low rotor vibrations. The altitude band (critical load region) is determined that produces loading levels in which vibrations appear. As this band is approached, conventional control of N1C2 and EPR is automatically over-ridden. N1C2 is decreased with altitude and exhaust area is reduced, thereby increasing the axial force (load) on the low rotor. When the upper limit of the band is reached, conventional control of N1C2 and EPR is automatically resumed, resulting in crossing the critical load region rapidly over a narrow altitude band.

Claims4

Dependent claims

A gas turbine engine having a low pressure rotor system characterized by:

means for providing a first plurality of altitude signals below a first engine operating altitude and a second plurality of altitude signals above said first altitude;
means for controlling engine exhaust pressure in response to an exhaust area signal;
signal processing means for providing said exhaust area signal and for controlling low pressure rotor speed, said signal processing means comprising means for storing a first schedule for providing said exhaust area signal to increase engine exhaust pressure with altitude in response to said first plurality of altitude signals and to decrease engine exhaust pressure with altitude in response to said second plurality of altitude signals;
and for storing a second schedule for decreasing low pressure rotor speed with altitude in response to said first plurality of altitude signals and increase low pressure rotor speed with altitude in response to said second plurality of altitude signals.

1 more element

Dependencies are inferred from the claim text.

Low rotor vibration avoidance in aircraft gas turbine engines

Life of this patent

Low rotor vibration avoidance in aircraft gas turbine engines

Life of this patent

Abstract

Claims4