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A fuel control system for a gas turbine engine having a staged combustor includes apparatus and methods to operate the combustor during pilot operation, staged operation, and transition between the two modes of operation. Various construction details are developed which provide a fuel control having

A fuel control system for a gas turbine engine having a staged combustor includes apparatus and methods to operate the combustor during pilot operation, staged operation, and transition between the two modes of operation. Various construction details are developed which provide a fuel control having a switch with built in hysteresis for determining the transition points between operating modes. In one embodiment, the combustor is switched from pilot to staged operation at a thrust level greater than the thrust level at which the combustor is switched from staged to pilot operation. During transitions between operating modes, the changes in fuel flows are limited by a plurality of rate limits to prevent combustor fuel spikes and blow-outs from occurring. During engine starts, the fuel lines to the main combustor are pre-filled to provide responsiveness during the transition from pilot to staged operation.

대표청구항 ▼

A method to transition from a pilot mode to a staged mode of a multi-stage combustor for a gas turbine engine, the method including the steps of: sensing the fill status of the main combustor fuel lines; reducing the %pilot flow to the pilot zone; and flowing the excess fuel into the lines of the ma

A method to transition from a pilot mode to a staged mode of a multi-stage combustor for a gas turbine engine, the method including the steps of: sensing the fill status of the main combustor fuel lines; reducing the %pilot flow to the pilot zone; and flowing the excess fuel into the lines of the main zone; wherein the step of reducing the %pilot flow includes the steps of: (a) rate limiting the reduction of the %pilot flow by a first rate limit value RL1 if the main combustor fuel lines are not full; (b) rate limiting the reduction of the %pilot flow by a second rate limit value RL2 for a predetermined amount of time subsequent to an indication that the main combustor fuel lines are full; and (c) controlling the %pilot flow as a function of thrust demand thereafter.