Abstract: The minimum fuel flow to a combustor of a gas turbine engine is limited in response to the engine inlet temperature T1 and x, an exponent dependent on engine configuration and engine entry pressure P1, in order to provide a fuel air ratio (FAR) limit which responds to both factors. This enables the fuel flow to be limited such that the FAR is set to avoid unintentionally extinguishing the combustor flame and the rate of deceleration is maximised, regardless of ambient temperature and engine altitude.

Abstract: The minimum fuel flow to a combustor of a gas turbine engine is limited in response to the engine inlet temperature T1 and x, an exponent dependent on engine configuration and engine entry pressure P1, in order to provide a fuel air ratio (FAR) limit which responds to both factors. This enables the fuel flow to be limited such that the FAR is set to avoid unintentionally extinguishing the combustor flame and the rate of deceleration is maximised, regardless of ambient temperature and engine altitude.

Abstract: The present application relates to fuel flow limit calculator (12) for use with a fuel control system (30) of an engine (10) comprising a fuel delivery means (28) and a compressor (16). The fuel control system (12) seeks to control the fuel/air ratio (FAR) near the weak extinction limit of the engine (10) as calculated by the fuel flow limit calculator (12). Both the static (PS3) and total (P3) pressure are measured at the exit of compressor (16). This enables a flow reference value (Q3) to be determined so that the air mass flow (W3) can be calculated and the limiting fuel/air ratio calculated. An advantage of the present invention is that it does not require stable combustion for satisfactory operation and allows the occurrence of preferential extinction within an annular combustor (22) to be beneficially utilised.

Abstract: The minimum fuel flow to a combustor of a gas turbine engine is controlled in response to the combustor inlet temperature T3 in order to provide a FAR stability margin which responds to the combustor inlet temperature. This enables the FAR stability margin to be reduced when the risk of flame out is low, for example when the combustor entry temperature is high, while increasing the FAR stability ratio when the combustor entry temperature is low, ie when the engine is idling or when water is ingested.