Thermodynamic and thermoeconomic analyses and energetic and exergetic optimization of a turbojet engine
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Thermodynamic and thermoeconomic analyses and energetic and exergetic optimization of a turbojet engine Arman Ekrataleshian1 · Fathollah Pourfayaz1 · Mohammad Hossein Ahmadi2 Received: 11 June 2020 / Accepted: 24 September 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract In this study, a thermal model for a turbojet engine is proposed. Besides the engine’s performance, the cost flow rate of each component is evaluated by performing the energetic, exergetic and exergoeconomic analyses. The compressor pressure ratio (πAC), flight Mach number (Ma) and turbine inlet temperature (TIT) are three operating variables, which affect the performance of the whole system. Therefore, a sensitivity analysis is carried out to survey the effect of these variables on objective functions (i.e., energy efficiency, exergy efficiency, and exergy destruction). It is found that there are some contradictions between exergy efficiency and exergy destruction, which by increment in TIT energy efficiency increases, while the exergy destruction decreases. Therefore, an optimization should be applied on the presented system. The results show that the highest exergy destruction, unit exergy cost, and cost rate are 34.96 GJ h−1, 34.85 US$ GJ−1 and 437.37 US$ h−1 occur in the combustion chamber, compressor’s outlet flow and combustion chamber outlet stream, respectively. The energetic and exergetic optimization solution is obtained as the Pareto frontier. Final decision-making methods such as TOPSIS, LINMAP are employed for choosing the optimal solution. Design points of LINMAP and TOPSIS having 65.86%, 66.95% thermal efficiency and 12.51 GJ h−1, 12.65 GJ h−1 exergy destruction, respectively. Keywords Energy · Exergy · SPECO · Exergoeconomic · Sensitivity analysis · Genetic algorithm List of symbols ACC Annual capital cost rate (US$ h−1) c Unit exergy cost (US$ GJ−1) c1 Air inlet speed of system cp Specific heat capacity (kJ kg−1 K−1) C Cost rate (US$ h−1) CRF Capital recovery factor ̇ Exergy rate (GJ h−1) Ex IP Improvement potential f Exergoeconomic factor F Ċ Fuel cost rate (US$ h−1) h0 Specific enthalpy at initial state (kJ kg−1) h Specific enthalpy(kJ kg−1) * Fathollah Pourfayaz [email protected] * Mohammad Hossein Ahmadi [email protected] 1
Department of Renewable Energy and Environment, Faculty of New Sciences and Technologies, University of Tehran, Tehran, Iran
Faculty of Mechanical Engineering, Shahrood University of Technology, Shahrood, Iran
2
k Specific heat ratio LHV Lower heating value of fuel (kJ kg−1) m Mass flow rate (kg s−1) n Lifetime of the system (year) P Pressure (kPa) PEC Purchased equipment cost (US$) PR Fuel sell price (US$ kg−1) PVF Present value factor PW Present worth (US$) Q̇ Heat transfer rate (kW) R Universal gas constant (kJ kg−1 K−1) s Specific entropy (kJ kg−1 K−1) s0 Specific entropy at initial state (kJ kg−1 K−1) SV Salvage value (US$) T0 Total temperature ratio Ż Hourly levelized capital cost rate (US$ h−1) Greek symbols π Compression ratio ψ E
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