GasTurb-Based Analysis of Turbine Inlet Temperature, Cooling Demand, and Design-Space Matching in a Low-Bypass Mixed-Flow Turbofan

Increasing turbine inlet temperature (TIT) changes cooling demand and engine matching, but its effect on fuel consumption under a fixed thrust requirement is not determined by temperature alone. This study examined a cooled, two-spool, low-bypass mixed-flow turbofan across six TIT conditions under common thrust and turbine-metal-temperature constraints. Adaptive random design searches varied bypass ratio, fan and high-pressure compressor (HPC) pressure ratios, nozzle area ratio, and corrected inlet flow while recalculating four turbine cooling fractions. At each TIT, 1024 converged solutions near the thrust target were retained and classified into low-, mid-, and high-SFC groups. Across the investigated TIT range, the median cooling fraction rose by approximately 1.46 percentage points, core flow fell by approximately 3.9%, and bypass flow rose by approximately 12.6%, while median SFC increased by approximately 0.15%. The lower-SFC groups combined higher HPC pressure ratios with higher cooling demand, and similar thrust and SFC occurred with different nozzle-matching states. Local constant-thrust BPR rematching reduced the TIT-dependent SFC sensitivity by approximately 85–86% relative to fixed-BPR calculations, although the matched SFC slope remained positive. Nominal off-design calculations also showed that design-point SFC rankings were not preserved at every flight condition. These results identify coupled compression, cooling, and exhaust-matching responses under the specified constraints.