Yazar "Kirmizi, Mehmet" seçeneğine göre listele

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    Application of exergetic analysis to inverted Brayton cycle engine at different flight conditions
    (Elsevier, 2023) Karabacak, Mustafa; Kirmizi, Mehmet; Aygun, Hakan; Turan, Onder
    The aviation sector has continued to be modernized by overcoming technological challenges involving strict constraints for mission requirements. In this context, the great attention to newly proposed methods which the requirements satisfied has been drawn in the related aviation field. As a novelty, performance and exergy an alyses of inverted Brayton cycle engine (IBCE) are investigated at supersonic speed (2.5 M) by comparing it with a conventional afterburning turbojet engine (CATE) in this study. Moreover, exergy analysis is performed solely for the IBCE at 5 M where only the IBCE could generate thrust. According to performance findings, specific fuel consumption (SFC) of the CATE changes from 57.97 g/kNs and 71.72 g/kNs whereas it raises from 51.76 g/kNs and 56.57 g/kNs for the IBCE due to variation of turbine inlet temperature (TIT) and afterburner exit temper ature (AET) at 2.5 M. Also, thermal efficiency of the CATE varies approximately between 32.97% and 46.73% while that of IBCE changes between 50.72% and 58.43% for IBCE at 2.5 M. At hypersonic speed, SFC of the IBCE is measured to vary between 71.34 g/kN and 85.49 g/kN at 5 of Mach. Lastly, the exergy efficiency of IBCE changes between 23.73% and 27.70% at same conditions. Where the higher TIT leads to lowering it whereas the higher AET provides increment of exergy efficiency. This study shows that thanks to cycle change, gas turbine engines could provide more advantages for new generation aircraft compared with conventional ones.
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    Performance and energy analysis of turboprop engine for air freighter aircraft with the aid of multiple regression
    (Elsevier, 2023) Kirmizi, Mehmet; Aygun, Hakan; Turan, Onder
    In this study, performance and energy analyses of a turboprop engine (TPE) are determined for an air freighter aircraft. For this aim, influences of different design variables involving turbine inlet temperature (TIT) ranging 1200 K and 1400 K, pressure ratio of compressor (CPR) ranging 16 and 20 and propeller efficiency (PE) ranging from 0.7 to 0.98 are elaborately searched, which helps in observing changes of specific fuel consumption (SFC), thrust force, engine power and overall efficiency related to the turboprop engine at an altitude of 6.7 km and 0.59 Mach. Based on this analysis, relations of these parameters with the mentioned design variables are researched with multiple regression method. In the light of performance results, SFC of the TPE changes from 0.2449 kg/kW.h to 0.1844 kg/kW.h due to rising PE and diminishes from 0.2263 kg/kW.h to 0.2159 kg/kW.h owing to rising TIT. On the other hand, overall efficiency of the TPE increases from 21% to approximately 40% due to rising PE and enhances from 26.3% to 28.12% due to rising TIT whereas it decreased from 27.6% to 23.5% due to increasing the CPR. Finally, the linear modeling of both SFC and overall efficiency regarding TPE with pairs of TIT and CPR variables results in about 0.97 of coefficient of determination (R2 ) whereas it is improved to more than 0.99 of R2 by using quadratic modeling. Moreover, for the modeling involving PE variable, R2 is computed as 0.99 with linear equations. Therefore, quadratic modeling enables R2 to slightly increase. It is thought that this analysis could benefit in knowing how much design parameters are effective on turboprop performance indicators.
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    Propeller effects on energy, exergy and sustainability parameters of a small turboprop engine
    (Elsevier Ltd, 2022) Aygun, Hakan; Kirmizi, Mehmet; Turan, Onder
    Turboprop engines have been commonly adopted for several applications such as unmanned aerial vehicle and commuter aircraft. In this study, the effects of propeller efficiency (PEF) with various compressor pressure ratio (CPR) are examined for energetic, exergetic, environmental and sustainability indicators of a small turboprop engine (S-TPE) at sea level. For this aim, PEF of the S-TPE has the range varying between 0.7 and 0.95 whereas its CPR has boundary changing between 10 and 12.5. According to performance results, thrust of the S-TPE changes from 5.11 kN to 6.88 kN due to rising PEF and from diminishes from 5.9 kN to 5.68 kN due to rising CPR whereas overall efficiency of the S-TPE alters from 22.1% to 29.7% owing to the PEF effect and from 24.7% to 25.5% owing to the CPR effect. On the other hand, exergetic parameters of the components of the engine remain constant with the PEF effect whereas both effects (PEF and CPR) are observed on exergetic metrics of the whole engine. In this context, exergy efficiency of the combustor increases from 84.83% to 86.7% due to only the CPR effect. Moreover, exergy efficiency of the S-TPE experiences the increase from 21.39% to 28.77% due to rising PEF while it raises from 23.99% to 24.71% due to rising CPR. Finally, specific wasted exergy of the S-TPE decreases from 0.7566 MW/kN to 0.5624 MW/kN with the effect of PEF whereas it drops from 0.6751 MW/kN to 0.6540 MW/kN with the effect of CPR. These findings show that a small change in design variables reflects on energetic and exergetic performance of the engine at different degrees.
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    Stage-based exergy analysis for a modern turboprop engine under various loading
    (Pergamon-Elsevier Science Ltd, 2024) Kirmizi, Mehmet; Aygun, Hakan; Turan, Onder
    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.