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    Energetic and exergetic metrics of a cargo aircraft turboprop propulsion system by using regression method for dynamic flight
    (Elsevier, 2024) Energetic and exergetic metrics of a cargo aircraft turboprop propulsion system by using regression method for dynamic flight; Kırmızı, Mehmet; Aygün, Hakan; Turan, Önder
    Nowadays, the development of aviation in line with sustainability goals is one of the current challenges. Being a source of environmental impact, aero-engines have been the main research and design object for achieving these aims. In this study, thermodynamic analysis involving exergy and sustainability computations is performed at different flight conditions where Mach varies between 0 and 0.7 and altitude changes between 0 and 7.7 km. Based on this analysis, modeling exergy parameters for each component are carried out with multiple regression approach. The exergy efficiency of turboprop engine at dynamic flight conditions varies between 15% and 25.9% whereas it is measured between 76 and 77% for the combustor and between 93 and 99% for gas turbine. Moreover, exergy destruction of the turboprop engine changes between 2.15 MW and 7.55 MW. Exergetic improvement potential rate (IPR) of the combustor resides between 0.4 MW and 1.21 MW throughout flight conditions whereas it is found at orders of 0.1 MW or less for other components. On the other hand, linear and quadratic modelings are performed for several parameters of turboprop engine components including exergy efficiency, exergy destruction and IPR under dynamic flight conditions. The determination coefficient (R2) of the models changes between 0.69 and 0.98 in linear modeling, whereas R2 in quadratic modeling improves to 0.97 and 0.99 ranges. It is thought that component-based modeling by considering different flight conditions could contribute to determining points where component efficiency is the highest.
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    Multi-objective optimization of a small turbojet engine energetic performance
    (Elsevier Ltd, 2023) Aygün, Hakan; Kırmızı, Mehmet; Kılıç, Ulaş; Turan, Önder
    Indexed keywords SciVal Topics Metrics Abstract Application fields of small turbojet engines (STJE) have been increasing day by day due to their superior features such as high power to weight ratio and reliability. In this study, parametric cycle analysis peculiar to STJE is implemented for different design variables such as compressor pressure ratio (CPR), turbine inlet temperature (TIT) as well as ambient temperature (T0). Based on these evaluations, several performance metrics of STJE are dealt with together by applying three different methods such as multi-objective genetic algorithm (MOGA), particle swarm optimization (MOPSO) and grey wolf optimization (MOGWO) under five analyses. According to performance analyses, net thrust of the STJE has improvement from 3.2 kN to 5.41 kN due to the increased TIT whereas it deteriorates from 4.87 kN to 4.67 kN due to the elevated CPR. However, with effect of the higher TIT, specific fuel consumption (SFC) of the STJE ascends from 42.96 g/kNs to 49.04 g/kNs while it diminishes from 39.57 g/kNs to 31.5 g/kNs owing to the higher CPR. The higher T0 leads net thrust to lower but the higher SFC. According to optimization findings at fourth analysis, the lower SFC is obtained with 31.51 g/kNs by MOGA than the other methods where SFC is 33.11 g/kNs whereas the higher net thrust is obtained with 6.209 kN by both MOPSO and MOGWO than the findings of MOGA where net thrust is 4.68 kN. When considering five optimization analyses, the findings of MOGA, MOGWO and MOPSO could be utilized depending on aircraft mission that turbojet engine requires to perform. It is thought that performing of multi-objective optimization could help in designing turbojet engines to the engineers.
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    Stage-based exergy analysis for a modern turboprop engine under various loading
    (Pergamon-Elsevier Science Ltd, 2024) Kırmızı, Mehmet; Aygün, Hakan; Turan, Önder
    Enhancements in propulsion systems have played a key role in promoting aircraft fuel efficiency, which serves to achieve global decarbonization goals. In particular, investigation by decoupling individual components of the whole engine explicitly provides insight about improvement potential. In this study, stage-based exergetic assessments of the turbomachinery components such as compressor and turbine for a large turboprop engine used in military cargo aircraft are performed for five different flight cases. As a novelty, a new index called specific irreversibility ratio (SIR) showing irreversibility per unit power is established. In this regard, exergy efficiency of compressor changes from 86.6 % to 96.3 % throughout the 14 stages whereas for whole compressor, it is measured as 89.3 %. On the other hand, exergy efficiency of gas turbine changes from 92.5 % to 91.8 % throughout 2 stages whereas, for power turbine, it varies from 89.1 % to 89.7 % throughout 2 stages. Moreover, SIR of air compressor diminishes from 12.94 % to 4.26 % throughout 14 stages whereas those of gas turbine and power turbine increase from 8.17 % to 8.84 % and from 11.52 % to 12.58 % along with two stages, respectively. As for effect of flight cases, exergy efficiency of whole compressor changes by 2 % whereas those of gas and power turbines vary by 0.2 % and 0.5 %, respectively throughout flight cases. However, improvement potential rate of air compressor experiences a change between 23.81 kW and 58.19 kW whereas it varies between 27.31 kW and 50.74 kW for gas turbine and between 26.24 kW and 36.23 kW for power turbine. It could be inferred that variation of exergetic metrics throughout stages is more apparent in comparison with those of flight cases. The methodology improved in this study could help in understanding stage-based efficiency of turbomachinery components at on-design and off-design conditions.