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Öğe Artificial neural networks modeling of combustion parameters for a diesel engine fueled with biodiesel fuel(PERGAMON-ELSEVIER SCIENCE LTD, 2022) Can, Özer; Baklacıoğlu, Tolga; Öztürk, Erkan; Turan, ÖnderIn the present study, numerous artificial neural networks were employed to predict the combustion characteristics of a four-stroke, single-cylinder, naturally aspirated diesel engine, including multilayer perceptron (MLP), adaptive neuro-fuzzy interference system (ANFIS) and radial basis function network (RBFN). The actual data derived from measurements and calculations were applied in model training, cross-validation, and testing. Biodiesel fuel ratio, engine load, air consumption, and fuel flow rate data were considered as model-input parameters, which are related to main engine operating variables and also affect the combustion characteristics. These kinds of model-input data were especially preferred due to being commonly direct measurable with the main engine sensors or found in engine maps/look-up tables managed by the electronic control unit (ECU). The main parameters obtained from the direct analysis of the measured in-cylinder pressure data and the heat release analysis results were also determined as model-output parameters. Equally, to ensure a more accurate, straightforward and practical approach to prediction, in every category of neural networks, three training algorithms were adopted, including Levenberg-Marquardt (LM), back propagation (BP) and conjugate gradient (CG). Moreover, a sensitivity analysis was accomplished by assessing the strengths of the links between input and output parameters for every topology. As such, the researcher revealed that all proposed neural networks could predict maximum heat release rate (HRRmax), ignition delay (ID), maximum cylinder pressure (P-max), maximum cylinder pressure location (qP(max)), maximum in-cylinder pressure rise rate (dP(max)), indicated mean effective pressure (IMEP), crank angle of center heat release rate (CA50), and combustion duration (CD), with a high accuracy rate. Results of model-output parameters are also important parameters in the combustion diagnostics which are influential on engine thermal efficiency and pollutant formation process. In addition, it is necessary to note that MLP architectures that incorporated the LM algorithm presented superior results. With regards to the optimal ANN model, the linear coefficient values: 0.999848, 0.999847, 0.999955, 0.999780, 0.999378, 0.999929, 0.999766, and 0.999216, were found for ID, HRRmax, P-max, qP(max), dP(max), IMEP, CA50 and CD, respectively.Öğe Effects of design parameters on thermal parameters for an adaptive cycle turbofan(Springer Science and Business Media B.V., 2023) Aygun, Hakan; Ekmekçi, İsmail; Turan, ÖnderIn this study, effects of high-pressure compressor pressure ratio (HPC PR) and bypass ratio (BPR) regarding adaptive cycle turbofan (ACT) engine on performance parameters and second law parameters of thermodynamics involving Carnot, Curzon–Ahlborn, Caputo, thermal and exergy efficiencies are dealt with. For this aim, HPC PR changes between 4 and 6, and bypass ratio ranges between 0.3 and 0.6. At same altitude of 10,000 m, comparative analysis is performed for efficiency behavior of ACT engine at military mode (MM) and afterburner mode (ABM). Better understanding of performance improvements of a military aircraft can be possible by investigating these efficencies for different design variables. Based on these computations, environmental and irreversibility parameters involving specific irreversibility production and environmental effect factor regarding ACT engine are dealt with at both modes. According to performance outcomes, SFC of the ACT engine decreases by 7.66% at MM, whereas it increases by 0.34% at ABM due to higher BPR. Moreover, it diminishes by 4.98% at MM and decreases by 0.42% at ABM with influence of the elevated HPC PR. As for efficiency analyses, exergy efficiency of ACT engine increases from 20.04 to 21.7% at MM, whereas it decreases 17.43 to 17.37% at ABM with effect of raised BPR. The higher HPC PR leads to increase from 20.32 to 21.38% at MM and from 17.39 to 17.46% at ABM. Among the components, the combustor has the lowest exergy efficiency, which is favorably affected from both variables at MM. Finally, environmental effect factor of the ACT becomes lower thanks to the higher BPR and HPC PR at MM. However, at ABM, to increase these variables do not result in lower EEF. Therefore, considering design parameters according to operation modes could lead in finding more meaningful outcomes. It is thought that this study helps in analyzing of thermodynamic parameters with respect to different design parameters.Öğe 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, ÖnderNowadays, 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.Öğe Multi-objective optimization of a small turbojet engine energetic performance(Elsevier Ltd, 2023) Aygün, Hakan; Kırmızı, Mehmet; Kılıç, Ulaş; Turan, ÖnderIndexed 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.Öğe Off-design analysis of the inverted Brayton cycle engine(Emerald Publishing, 2024) Karabacak, Mustafa; Turan, ÖnderPurpose: The purpose of this study is to perform an off-design analysis of the inverted Brayton cycle engine. Design/methodology/approach: The off-design analysis equations of the inverted Brayton cycle engine were first derived in this study and the control parameters of the inverted Brayton cycle engine were first determined and investigated. Findings: It is observed that by controlling the total temperature decrease in cooling section, it is possible to adapt the engine for low specific fuel consumption working conditions or high thrust working conditions. Specific fuel consumption is reduced by 27.1 % by stopping cooling in the cooling section and thrust is increased by 27.6 % by working with full load of the cooling section (500 K temperature decrease in cooling section). It is observed that thrust depending on the flight Mach number increases with an increase in flight Mach number and reaches a peak value at 5.21 flight Mach number and reduces by 80.8 % at 6 flight Mach number relative to the peak value. The specific fuel consumption increases rapidly as the Mach number increases, and the specific fuel consumption is 49.0 g/[kN.s] at Mach 1, reaches 70.4 g/[kN.s] at Mach 5 and increases to 412 g/[kN.s] at Mach 6. The specific fuel consumption increases from 68.1 to 73.0 g/(kN.s) and the thrust decreases from 16.5 to 13.3 kN as the total preburner exit temperature increases from 1,500 to 2,000 K. Specific fuel consumption decreases from 83.1 to 64.8 g/(kN.s) and thrust increases from 4.60 to 11.08 kN depending on afterburner exit total temperature increase from 1,800 to 2,500 K. Research limitations/implications: The cooling section reduces total temperature of the gas flow to lower values to increase the compressor total pressure ratio. The compressor increases the total pressure of the gas flow to the optimum total pressure ratios to increase the nozzle exit Mach number and gain more thrust. The afterburner increases the total temperature of the gas flow to increase the sound speed in the nozzle exit to increase thrust. The nozzle expands the gas flow to reduce the static pressure of the gas flow to near the optimum value, atmosphere pressure, to increase thrust and reduce specific fuel consumption. Practical implications: Hypersonic and supersonic air vehicles can use the current engine model for the its own propulsion systems. Social implications: After first heavier than air flight, aero engines was designed for only used for aero vehicle. Internal combustion engines were used for propelled propeller aircraft at the first term of aircraft. However, propeller-propelled aircrafts are not sufficient to increase aircraft velocity to supersonic Mach numbers due to the shock losses of propeller, so the supersonic era was only introduced by revolution in propulsion systems with new concept. A jet engine was developed to be candidate for supersonic flight. Originality/value: Off-design analysis equations of an inverted Brayton cycle engine were first derived in this study. Furthermore, the control parameters of the inverted Brayton cycle engine were first determined and investigated in this paper.Öğe Path planning based on unmanned aerial vehicle performance with segmented cellular genetic algorithm(Gazi Universitesi, 2024) Gezer, Ahmet; Turan, Önder; Baklacıoğlu, TolgaAn important part of UAV technological development consists of improvements in the scope of path planning. Different choices can be made in path planning according to operational priorities, it may be preferred to reach the destination as fast as possible or to increase the airtime by compromising speed. For every speed and altitude that the UAV can fly; fuel data of cruise, climb and descent phases are used in the path planning algorithm. Thus, economical and airtime-maximizing paths could be produced on the basis of performance characteristics compatible with the kinematic constraints customized for the UAV. In this study, Cellular (cGA) and Segmented Cellular Genetic Algorithm (scGA) are proposed. The novel overprotective algorithm which has a fixed initial population and segmented chromosome structure achieves a high convergence speed to optimal solution and can generate paths which have 5.2 times higher fitness value on average compared with a conventional Genetic Algorithm (GA). It has been seen that scGA improves the initial population in terms of the best solutions 1.9 times and the general population 5.8 times better compared with GA. © 2024 Gazi Universitesi. All rights reserved.
