Gas turbine engine fuel control system with enhanced relight capability.

摘要

A software-implimented relight fuel flow scheduler is disclosed which controls fuel flow to the combustor of a turbofan aeroengine during in-flight relight procedures. The schedule includes the following elements. A first fuel ramp F, whose slope decreases with increasing altitude, enables the combustor to light with minimum fuel flow for the altitude and thus helps to prevent overfueling. The fuel flow rate undergoes a step reduction at H, after detection of satisfactory combustion at G, to prevent compressor stall, but cannot drop below a predetermined level to guard against flameout. Ramp F is repeated if satisfactory combustion does not occur. The fuel ramp I-J is varied from flat to positive slope depending on the ratio of the rate of change of high pressure compressor speed to a datum level in order to prevent a hung start and accelerate the engine until normal acceleration control laws K take over at J min .