Ensuring non-excessive variation of gradients in auto-tuning a gas turbine engine

A method performed by a computing device having a processor and memory, the method for ensuring non-excessive variation of a gradient of an applied split bias versus firing temperature of a gas turbine engine, the method comprising:

• determining that an incremental split bias step is desired during automatic tuning of the gas turbine engine;
• identifying a current firing temperature of the gas turbine engine on a graph that plots a firing temperature versus a percentage of split;
• determining that a margin is unavailable for a first direction incremental split bias step associated with a split bias in a first direction but that the margin is available for a second direction incremental split bias step associated with a split bias in a second direction, wherein the first direction and the second direction correspond to higher temperatures or lower temperatures on the graph than the current firing temperature;
• calculating a first difference between a split schedule gradient and an applied split schedule gradient using plotted points on a split schedule curve and an applied split schedule curve corresponding to the second direction;
• calculating a second difference between the split schedule gradient and the applied split schedule gradient using plotted points on the split schedule curve and the applied split schedule curve that are directly adjacent and that are on both sides to points corresponding to the current firing temperature;
• and
• if at least one of the first difference or the second difference exceeds a predetermined limit, not allowing an incremental split bias step to be taken in the direction.

One or more computer-readable media that, when invoked by computer-executable instructions, perform a method for ensuring non-excessive variation of a gradient of an applied split bias versus firing temperature of a gas turbine engine, the method comprising:

• determining that an incremental split bias step is to be taken during automatic tuning of the gas turbine engine;
• identifying a current firing temperature of the gas turbine engine on a graph that plots a firing temperature versus a percentage of split, the resulting curves being a split schedule curve whose plotted points are set by a manual tuner and an applied split schedule curve that includes the split schedule plus bias for each point on the curve;
• determining whether there is available margin at one or more points on the split schedule curve directly adjustment to points corresponding to the current firing temperature;
• calculating a first split schedule gradient between two points on the split schedule curve that represent lower firing temperatures than the current firing temperature;
• calculating a first applied split schedule gradient between two points on the applied split schedule curve that represent the lower firing temperatures than the current firing temperature;
• determining a first difference between the first applied split schedule gradient and the first split schedule gradient;
• calculating a second split schedule gradient between two points on the split schedule curve that represent higher firing temperatures than the current firing temperature;
• calculating a second applied split schedule gradient between two points on the applied split schedule curve that represent the higher firing temperatures than the current firing temperature;
• determining a second difference between the second applied split schedule gradient and the second split schedule gradient;
• and
• determining whether to take the incremental split bias step, such that,
• (1) if the first difference exceeds a predetermined limit, not allowing the incremental split bias step to be taken in a direction associated with the lower firing temperatures;
• and
• (2) if the second difference exceeds a predetermined limit, not allowing the incremental split bias step to be taken in a direction associated with the higher firing temperatures.