Abstract: A method is provided for evaluating stall/surge margin of a machine of interest. The method includes identifying a vital factor where each the vital factors corresponds to operation of the machine of interest. Raw data relating to the vital factor is provided. A contribution of the vital factor to the stall/surge margin is determined from at least the provided raw data. The contribution of the vital factor to the stall/surge margin is statistically analyzed. A stall/surge margin is allocated based on the statistical analysis of the contribution of the vital factor. An operating limit line is defined based on the allocation of the stall/surge margin.

Abstract: A gas turbine operational strategy is provided for the optimization of ISO-Day rated performance. The invention is realized by setting the nominal operating line equal to or slightly below the operating limit line, so that ISO full load performance is maximized. Thus, the first stage turbine nozzle throat area is sized such that, without inlet bleed heat addition, and at Base-Load pressure ratio and firing temperature, the compressor operates within its operational limits on a ISO day. As ambient conditions change, levels of inlet bleed heat and firing temperature are controlled and the inlet guide vane angle is set whereby the nominal operating line is equal to or slightly below the operating limit line.