The increasing demand for higher efficiency and lower emissions in aircraft gas turbines motivates investigation of alternative thermodynamic cycle architectures. This study assesses the performance and nitrogen oxides (NOx) emission behavior of a triple-spool, separate-exhaust turbofan engine equipped with an interstage turbine burner (ITB). A baseline engine representative of the RB211 Trent 892 is first modeled at maximum takeoff, sea-level static conditions and verified against publicly available takeoff reference data. The cycle is then modified by introducing an isobaric secondary combustion process between the high-pressure and intermediate-pressure turbines. The effects of fan pressure ratio, bypass ratio, overall pressure ratio, high-pressure turbine inlet temperature, and ITB exit temperature are examined using two-parameter response surface sweeps. Main combustor NOx is estimated using an RQL-type cycle correlation, while the ITB contribution is represented using an engineering source–sink model accounting for new NOx formation and partial reburning of upstream NOx. The baseline model predicts specific thrust, thrust-specific fuel consumption (TSFC), and NOx emission index (EINOx) within ±8% of reference values. At a selected ITB operating point, specific thrust increases by 1.98%, TSFC increases by 9.84%, thermal efficiency decreases by 2.56%, and the adopted engineering source–sink model predicts a 20.03% reduction in fuel flow-weighted EINOx. The corresponding takeoff-mode NOx-per-thrust indicator decreases by approximately 12.1%. These results indicate that ITB integration introduces a coupled performance–emissions trade-off and should not be evaluated solely as a thrust augmentation method.

Public aircraft-engine certification data provide a reproducible basis for emissions modeling when proprietary combustor geometry, engine-cycle data, and detailed operating histories are unavailable. This study develops a physically constrained framework based on the International Civil Aviation Organization (ICAO) Aircraft Engine Emissions Databank for modeling gaseous emissions from civil aircraft gas-turbine engines over the landing-and-take-off (LTO) cycle. The analysis uses variables available directly from the ICAO Aircraft Engine Emissions Databank, together with derived LTO quantities, to construct combustor-aware reduced-order correlations for LTO-averaged emission indices of nitrogen oxides (NO_x), carbon monoxide (CO), and hydrocarbons (HC), denoted by EINO_xLTO, EICO_LTO, and EIHC_LTO, respectively. High-bypass-ratio (HBPR) turbofan engines are grouped by representative combustor technology, including conventional/single-annular combustor (Conventional/SAC), double-annular combustor (DAC), twin-annular premixing swirler (TAPS), Rolls–Royce TALON lean-burn combustor, low-emissions combustor (LEC), and Unknown categories. For each pollutant and combustor group, two-predictor quadratic response surfaces and power-law correlations are fitted using public engine-level predictors such as overall pressure ratio, bypass ratio, rated thrust, and total LTO fuel consumption. The results show that combustor-aware grouping substantially improves interpretability and that no single global predictor pair represents all pollutants or combustor technologies. For EINO_xLTO, overall pressure ratio appears in most selected predictor pairs, consistent with the pressure- and temperature-sensitive nature of NO_x formation. For EICO_LTO, robust group-specific correlations are obtained for several combustor classes, whereas EIHC_LTO is more sensitive to zero and near-zero values, making percentage-based errors and log-space power-law fits less reliable. The quadratic models generally provide stronger within-dataset descriptive fits, while the power-law models provide compact non-negative scaling relations when their errors are acceptable.The proposed framework is suitable for emissions-trend analysis, preliminary comparative assessment, and interpretation of public certification data, but it should not be used as a substitute for certification testing, detailed combustor simulation, or off-design mission-level prediction without additional validation.

Public aircraft engine certification data provide a reproducible basis for emissions modeling when the proprietary combustor geometry, engine cycle data, and detailed operating histories are unavailable. This study develops a physically constrained reduced-order framework based on the International Civil Aviation Organization (ICAO) Aircraft Engine Emissions Databank for modeling gaseous emissions from civil aircraft gas turbine engines over the landing and take-off (LTO) cycle. In this framework, physical constraints are introduced through combustor-aware grouping, physics-informed predictor selection, empirical domain restrictions, and physical admissibility checks on the fitted correlations. The analysis uses variables available directly from the ICAO Aircraft Engine Emissions Databank, together with derived LTO quantities, to construct combustor-aware reduced-order correlations for LTO-averaged emission indices, namely for nitrogen oxides (NO_x), carbon monoxide (CO), and hydrocarbons (HC), denoted by ${\mathrm{EINOx}}_{\mathrm{LTO}}$, ${\mathrm{EICO}}_{\mathrm{LTO}}$, and ${\mathrm{EIHC}}_{\mathrm{LTO}}$, respectively. High-bypass-ratio (HBPR) turbofan engines are grouped by representative combustor technology, including conventional/single-annular combustor (Conventional/SAC), double-annular combustor (DAC), twin-annular premixing swirler (TAPS), Pratt & Whitney TALON lean-burn combustor, low-emissions combustor (LEC), and an Unknown category. For each pollutant and combustor group, two-predictor quadratic response surfaces and power law correlations are fitted using public engine-level predictors such as the overall pressure ratio, bypass ratio, rated thrust, and total LTO fuel consumption. The results show that combustor-aware grouping improves interpretability and that no single global predictor pair represents all pollutants or combustor technologies. For ${\mathrm{EINOx}}_{\mathrm{LTO}}$, the overall pressure ratio appears in every selected predictor pair, consistent with the pressure- and temperature-sensitive nature of NO_x formation. For ${\mathrm{EICO}}_{\mathrm{LTO}}$, strong within-dataset group-specific correlations are obtained for several combustor classes, whereas ${\mathrm{EIHC}}_{\mathrm{LTO}}$ is more sensitive to zero and near-zero values, making percentage-based errors and log-space power law fits less reliable. The quadratic models generally provide stronger within-dataset descriptive fits, while the power law models provide compact non-negative scaling relations for groups where their errors are acceptable. The proposed framework is suitable for emissions trend analysis, preliminary comparative assessment, and the interpretation of public certification data, but it should not be used as a substitute for certification testing, detailed combustor simulation, or off-design mission-level prediction without additional validation.

The increasing demand for higher efficiency and lower emissions in aircraft gas turbines motivates investigation of alternative thermodynamic cycle architectures. This study assesses the performance and NOx emission behavior of a triple-spool, separate-exhaust turbofan engine equipped with an interstage turbine burner (ITB). A baseline engine representative of the RB211 Trent 892 is first modeled and verified against publicly available takeoff reference data. The cycle is then modified by introducing an isobaric secondary combustion process between the high-pressure and intermediate-pressure turbines. The effects of fan pressure ratio, bypass ratio, overall pressure ratio, high-pressure turbine inlet temperature, and ITB exit temperature are examined using two-parameter response-surface sweeps. Main-combustor NOx is estimated using an RQL-type cycle correlation, while the ITB contribution is represented using an engineering source–sink model accounting for new NOx formation and partial reburning of upstream NOx. The baseline model predicts specific thrust, TSFC, and EINOx within ±8% of reference values. At a selected ITB operating point, specific thrust increases by 1.98%, TSFC increases by 9.84%, thermal efficiency decreases by 2.56%, and the adopted engineering source–sink model predicts a 20.03% reduction in fuel-flow-weighted EINOx.

This study investigates the parametric cycle analysis of a triple-spool, separate-exhaust turbofan engine with inter-stage turbine burner (ITB). A typical conventional triple-spool, separate-exhaust turbofan engine has been selected as the baseline engine for this study. The baseline engine cycle is modified to introduce an isobaric inter-stage turbine combustion chamber which is placed in the transition duct between the high-pressure turbine (HPT) and the intermediate pressure turbine (IPT). Engine cycle design parameters such as compressor pressure ratio, fan pressure ratio, by-pass ratio, and HPT inlet temperature are varied parametrically. The main performance parameters of the modified engine cycle (specific thrust and thrust specific fuel consumption) are estimated and compared against those of the baseline engine cycle subject to design limitations due to maximum attainable component efficiencies, and maximum allowable turbine temperatures. The results showed that the implementation of ITB has significant effects on engine performance parameters, in addition to its potential to lower NOx emissions compared to the baseline engine.