Search

This study explores the potential of hydrogen gas turbine engines for sustainable aviation, with a particular focus on their development for low subsonic to transonic flight regimes. Hydrogen offers notable advantages, including zero CO 2 emissions and high energy density. However, its widespread adoption is prevented by significant challenges in production, infrastructure, storage, aircraft design, and combustion technology. The limited availability of green hydrogen – the global production totaled only 127 kt in 2023, with 76% produced in China - raises concerns about the feasibility of a rapid shift to hydrogen-powered general aviation. Despite numerous pledges for hydrogen adoption in the Western world, major aircraft manufacturers have primarily engaged in marketing activities rather than substantial product innovation. To date, the only hydrogen aircraft demonstrator from this century is the 2012 Boeing Phantom Eye, which utilized modified hydrogen internal combustion engines rather than a gas turbine engine. The only hydrogen aircraft demonstrator with a gas turbine engine was the 1988 hybrid Tupolev Tu-155 which coupled one hydrogen gas turbine engine to other two jet fuel engines. This paper evaluates the current state of hydrogen gas turbine technology, comparing its combustion characteristics with traditional jet fuels and examining various NOx emission control techniques. It also investigates the potential of micro-mix lean combustion and staged combustion to achieve efficient and low-emission hydrogen combustion in gas turbines. Given the more extensive experience with terrestrial gas turbines compared to their aeronautical counterparts, the review includes insights from terrestrial power generation applications. Additionally, it considers hythane - a blend of hydrogen and natural gas - as a transitional solution for significantly reducing CO 2 emissions while progressing towards net-zero targets. The review underscores the urgent need for advancements in green hydrogen production, technology, and infrastructure to overcome existing barriers and enable a more sustainable aviation future powered by hydrogen. Importantly, the review emphasizes the need to move beyond mere virtue signaling and make tangible progress toward a hydrogen economy. [ABSTRACT FROM AUTHOR]

Computational models of turbofans that are oriented to assist the design and testing of innovative components are of fundamental importance in order to reduce their environmental impact. In this paper, we present an effective method for developing numerical turbofan models that allows reliable steady-state turbofan performance calculations. The main difference between the proposed method and those used in various commercial algorithms, such as GasTurb, GSP 12 and NPSS, is the use of neural networks as a multidimensional interpolation method for rotational component maps instead of classical β parameter. An additional aspect of fundamental importance lies in the simplicity of implementing this method in Matlab and the high degree of customization of the turbofan components without performing any manipulation of variables for the purpose of reducing the dimensionality of the problem, which would normally lead to a high condition number of the Jacobian matrix associated with the nonlinear turbofan system (and, thus, to significant error). In the proposed methodology, the component behavior can be modeled by analytical relationships and through the use of neural networks trained from component bench test data or data obtained from CFD simulations. Generalization of rotational component maps by feedforward neural networks leads to an average interpolation error up to around 1 % , for all variables. The resulting nonlinear system is solved by a combined genetic algorithm and least squares algorithm approach, instead of the standard Newton's method. The turbofan numerical model turns out to be convergent, and results suggest that the trend in overall turbofan performance, as flight conditions change, is in agreement with the outputs of the GSP 12 software. [ABSTRACT FROM AUTHOR]

In this study, the implementation of a solid oxide fuel cell–gas turbine hybrid engine for primary propulsion and electric power generation in aircraft is investigated. The following three parameters, which are crucial in attaining optimal performance at any point in the flight profile, were identified: the oxygen-to-carbon ratio of the catalytic partial oxidation reformer, the fuel utilization factor of the fuel cell, and the airflow split ratio at the outlet of the high-pressure compressor. The study assesses the impact of varying these parameters within specified ranges on the performance of the hybrid system. At the design point, the system yielded a total power output of 1.96 MW, with 102.5 kW of electric power coming from the fuel cell and 7.9 kN (1.86 MW) of thrust power coming from the gas turbine. The results indicate that varying the oxygen-to-carbon ratio affected the fuel cell's fuel utilization and resulted in a slight decrease in gas turbine thrust. The fuel utilization factor primarily affected the power output of the fuel cell stack, with a minor impact on thrust. Notably, varying the airflow split ratio showed the most significant influence on the overall system performance. This analysis provides insights into the system's sensitivities and contributes to the development of more sustainable aircraft energy systems. [ABSTRACT FROM AUTHOR]

In this study, thermodynamic analysis is implemented to the kerosene‐fuelled high by‐pass turbofan (HBP‐TF) engine to assess entropy, exergy, environmental, and sustainability metrics for different design variables such as pressure ratio of high‐pressure compressor (HPC‐PR) ranging from 7.5 to 8.5 and turbine inlet temperature (TIT) varying from 1400 to 1525 K considering variable needs in the aviation industry. As a novelty, entropic improvement potential (EIP) index for turbomachinery components and specific irreversibility production for the whole engine are calculated. Sustainability‐based parameters for different cases are compared with the baseline values of the HBP‐TF engine. The combustor has the highest entropy production of 44.4425 kW K−1 at the baseline. The higher TIT increases the entropy production of the combustor by 16.56%, whereas the higher HPC‐PR decreases it by 5.83%. The higher TIT and HPC‐PR favorably affect the sustainable efficiency factor of the engine, which is observed as 1.5482 at baseline and increases by 4.5% and 0.058% with the increment of TIT and HPC‐PR, respectively. The higher TIT and higher HPC‐PR results in lowering sustainability of the engine. The specific irreversibility production of the engine decreases by 3.78% and 0.1171% respectively, as TIT and HPC‐PR reach the highest point considered in the study. [ABSTRACT FROM AUTHOR]

The twin-spool rotor-bearing system plays a crucial role in the aero-engine. The potential manufacturing defect, assembly error, and abnormal working loads in the rotor-bearing system can induce multiple rotor failures, such as bolt looseness and rub impact. However, the prediction of the fault rotor dynamic behavior for the aero-engine remains a difficult frontier in numerical modeling. We present a dynamic model of the twin-spool rotor-bearing system, the failure model of bearing seat loosening, and the failure model of rub impact by using second-type Lagrangian equations, finite element theory, and the Timoshenko beam theory. In particular, to improve the accuracy of the numerical model, the rotating speed control equation and the actual aero-engine parameter are taken into account. An analysis is conducted on the impact of critical failure parameters, such as looseness stiffness and rub impact initial gap, on the vibration behaviors of the essential components of the twin-spool rotor system and on the entire engine. Additionally, this paper examines the twin-spool rotor-bearing system affected by looseness–rub coupled failures. The obtained conclusions can serve as a theoretical foundation for optimizing the structure and diagnosing faults in the aero-engine rotor system. [ABSTRACT FROM AUTHOR]

Abstract In this study, thermodynamic analysis is implemented to the kerosene‐fuelled high by‐pass turbofan (HBP‐TF) engine to assess entropy, exergy, environmental, and sustainability metrics for different design variables such as pressure ratio of high‐pressure compressor (HPC‐PR) ranging from 7.5 to 8.5 and turbine inlet temperature (TIT) varying from 1400 to 1525 K considering variable needs in the aviation industry. As a novelty, entropic improvement potential (EIP) index for turbomachinery components and specific irreversibility production for the whole engine are calculated. Sustainability‐based parameters for different cases are compared with the baseline values of the HBP‐TF engine. The combustor has the highest entropy production of 44.4425 kW K−1 at the baseline. The higher TIT increases the entropy production of the combustor by 16.56%, whereas the higher HPC‐PR decreases it by 5.83%. The higher TIT and HPC‐PR favorably affect the sustainable efficiency factor of the engine, which is observed as 1.5482 at baseline and increases by 4.5% and 0.058% with the increment of TIT and HPC‐PR, respectively. The higher TIT and higher HPC‐PR results in lowering sustainability of the engine. The specific irreversibility production of the engine decreases by 3.78% and 0.1171% respectively, as TIT and HPC‐PR reach the highest point considered in the study.

Computational models of turbofans that are oriented to assist the design and testing of innovative components are of fundamental importance in order to reduce their environmental impact. In this paper, we present an effective method for developing numerical turbofan models that allows reliable steady-state turbofan performance calculations. The main difference between the proposed method and those used in various commercial algorithms, such as GasTurb, GSP 12 and NPSS, is the use of neural networks as a multidimensional interpolation method for rotational component maps instead of classical β parameter. An additional aspect of fundamental importance lies in the simplicity of implementing this method in Matlab and the high degree of customization of the turbofan components without performing any manipulation of variables for the purpose of reducing the dimensionality of the problem, which would normally lead to a high condition number of the Jacobian matrix associated with the nonlinear turbofan system (and, thus, to significant error). In the proposed methodology, the component behavior can be modeled by analytical relationships and through the use of neural networks trained from component bench test data or data obtained from CFD simulations. Generalization of rotational component maps by feedforward neural networks leads to an average interpolation error up to around 1%, for all variables. The resulting nonlinear system is solved by a combined genetic algorithm and least squares algorithm approach, instead of the standard Newton’s method. The turbofan numerical model turns out to be convergent, and results suggest that the trend in overall turbofan performance, as flight conditions change, is in agreement with the outputs of the GSP 12 software.

In this study, the implementation of a solid oxide fuel cell–gas turbine hybrid engine for primary propulsion and electric power generation in aircraft is investigated. The following three parameters, which are crucial in attaining optimal performance at any point in the flight profile, were identified: the oxygen-to-carbon ratio of the catalytic partial oxidation reformer, the fuel utilization factor of the fuel cell, and the airflow split ratio at the outlet of the high-pressure compressor. The study assesses the impact of varying these parameters within specified ranges on the performance of the hybrid system. At the design point, the system yielded a total power output of 1.96 MW, with 102.5 kW of electric power coming from the fuel cell and 7.9 kN (1.86 MW) of thrust power coming from the gas turbine. The results indicate that varying the oxygen-to-carbon ratio affected the fuel cell’s fuel utilization and resulted in a slight decrease in gas turbine thrust. The fuel utilization factor primarily affected the power output of the fuel cell stack, with a minor impact on thrust. Notably, varying the airflow split ratio showed the most significant influence on the overall system performance. This analysis provides insights into the system’s sensitivities and contributes to the development of more sustainable aircraft energy systems.

The gas turbine-based propulsion systems were responsible for the emission of pollutants that damage the ecosphere. Commercial aviation represented a large portion of carbon emissions within the aviation industry, so this study focused on novel aircraft propulsion systems for large commercial aircraft. Electric propulsion was considered to be an alternative to conventional propulsion systems. Therefore, this report analyzed the various electric aircraft concepts within the aerospace industry to see whether they have environmental benefits. A flying wing aircraft was compared to a conventional tube-and-wing aircraft using Computational Fluid Dynamics to determine which aircraft requires more power. The lift forces acting on the conventional aircraft and flying wing at cruise speed were 269,110 N and 10681 N, while the drag forces acting on the conventional aircraft and Flying Wing Aircraft at cruise speed were 260,940N and 7679N, respectively. More electric aircraft approach has allowed the older power subsystems to be replaced by electrical systems within modern aircrafts such as the Boeings, airbus, etc. This has increased fuel efficiency. The result of the lift power requirement should be a boost for battery companies to develop FWA.Conclusively, the result inferred that the Flying Wing Aircraft is more aerodynamic and, therefore, would improve aircraft efficiency and emit less emission.

The subject matter of this article is the process of subsonic air intake shaping for high-bypass ratio turbofan at the airplane preliminarily designing stage. The goal was to improve a mathematical model of V. I. Polikovskii method of subsonic air intake shaping for high-bypass ratio turbofan. The tasks are to consider the presence of cant of inlet cross-section, required to perform effective operation at airplane cruising angle-of-attacks; to increase the radius of curvature of the air intake lip to provide air flow near it without flow separation, which was definitely determined and could not be increased in the existing method; to improve constant length velocity gradient law (used in this method) so that too large duct expansion angles near the air intake outlet cross-section can be avoided; to consider the engine inlet spinner presence. The methods used are analytical and digital mathematical methods, implemented in MathCAD and Microsoft Visual Studio systems. The following results were obtained: based on the proposed method, new calculation module for the Power Unit software version 11.8 has been developed (С-language Win32 UNICODE application) with a friendly user interface. Conclusions. The scientific novelty of the results obtained is as follows: 1) mathematical model (algorithm and its program implementation) for circular turbofan air intake shaping has been improved considering cant of the inlet cross-section, air intake lip rounding with two radiuses, presence of engine inlet spinner, and zero expansion angles in the diffuser outlet cross-section; 2) adequacy of calculation results using the improved mathematical model is shown using comparison with shapes of circular turbofan air intakes, developed by the leading aviation companies.

Turbofan engines are the primary propulsion units of commercial aviation today. Weight Turbofan engines are the primary propulsion units of commercial aviation today. Weight prediction of turbofan engines is an important step in the engine design. There are several models available in the literature with statistical and component-based approaches. In this study, a statistical multiple linear regression analysis-based approach was used for the estimation of engine weight with a targeted error margin of ±10%. Novel weight estimation equations were obtained in five different thrust intervals of turbofan engines available in market. The model was shown to have higher accuracy than most statistical models available in literature. The novel weight estimation equations are developed as a set of five formulas and correlates the engine weight by four engine design parameters which are bypass ratio, total pressure ratio, air mass flow rate, and thrust. Since those four parameters can be obtained easily from literature, the novel weight estimation equations do not require any proprietary engine data (geometry, component dimensions etc.) and simple to use with a ±10% accuracy. [ABSTRACT FROM AUTHOR]

The twin-spool rotor-bearing system plays a crucial role in the aero-engine. The potential manufacturing defect, assembly error, and abnormal working loads in the rotor-bearing system can induce multiple rotor failures, such as bolt looseness and rub impact. However, the prediction of the fault rotor dynamic behavior for the aero-engine remains a difficult frontier in numerical modeling. We present a dynamic model of the twin-spool rotor-bearing system, the failure model of bearing seat loosening, and the failure model of rub impact by using second-type Lagrangian equations, finite element theory, and the Timoshenko beam theory. In particular, to improve the accuracy of the numerical model, the rotating speed control equation and the actual aero-engine parameter are taken into account. An analysis is conducted on the impact of critical failure parameters, such as looseness stiffness and rub impact initial gap, on the vibration behaviors of the essential components of the twin-spool rotor system and on the entire engine. Additionally, this paper examines the twin-spool rotor-bearing system affected by looseness–rub coupled failures. The obtained conclusions can serve as a theoretical foundation for optimizing the structure and diagnosing faults in the aero-engine rotor system.

Presented herein is a comparative performance analysis of a novel turbofan engine with an auxiliary combustion chamber, nicknamed the TurboAux engine, against a turbojet engine, and a low bypass ratio turbofan engine with an afterburner is presented. The TurboAux engine is an adaption of the low-bypass ratio turbofan engine, but with secondary combustion in an auxiliary bypass annular combustion chamber for thrust augmentation. The TurboAux engine is envisioned with the desire to facilitate clean secondary burning of fuel at temperatures higher than in the main combustion chamber with air exiting the low-pressure compressor. The comparative study starts by analyzing the turbojet engine and its performance with and without an afterburner segment attached. In parallel, the conventional turbofan and its mixing counterpart are analyzed, also with and without an afterburner segment. A simple optimization analysis of a conventional turbofan is performed to identify optimal 'fan' pressure ratios for a series of low-bypass ratios (0.1 to 1.5). The optimal fan pressure ratios and their corresponding bypass ratios are adapted to demonstrate the comparative performance of the varying configurations of the TurboAux engine. The formulation and results are an attempt to make a case for charter aircrafts and efficient close-air-support aircrafts. The results yielded increased performance in thrust augmentation, but at the cost of a spike in fuel consumption. This trade-off requires more in-depth investigation to further ascertain the TurboAux's utility. [ABSTRACT FROM AUTHOR]

To understand the jet flow characteristics of turbofan separate exhaust system, a parametric design method based on the initial Class Shape Transformation function was developed. HBPR and UHBPR turbofan separate exhaust systems were designed. Furthermore, the jet flow characteristics of the HBPR turbofan exhaust system under take-off condition with zero angle of attack were studied based on numerical simulation. The jet flow characteristics of the HBPR and UHBPR turbofan exhaust system under take-off condition with high angle of attack were also simulated. The effects of angle of attack and bypass ratio on the jet flow characteristics were investigated and the related flow mechanisms were analyzed. Results show that the axisymmetric plumes of the HBPR turbofan exhaust system are distributed around the engine axis under take-off condition with zero angle of attack. With the plug wake as the center, the core flow, the fan/core shear layer, the fan flow, the fan/free stream shear layer and the free stream are wrapped around the plug wake from inside out. Vortexes appear in the lee area at the back of the cowl and jet flow under take-off condition with high angle of attack. These vortexes cause cross sectional secondary flow and expose the high-velocity core flow to the low-velocity free stream. The contact area and velocity gradient in the mixing region among the free stream, fan flow and core flow increase. Therefore, the mixture among jet flow and free stream strengthens. So the high-velocity region, the high-vorticity region, and the high turbulence kinetic energy region shorten by 55.1%, 47.7% and 50.9% respectively. The vorticity values and turbulence kinetic energy level peak on the upper side of the exhaust plumes increase by about 30% and 87% respectively. Relative to these parameters from the HBPR turbofan exhaust system, the jet velocity peak value of UHBPR turbofan decreases by 5.5% under take-off condition with high angle of attack. The vorticity values and turbulence kinetic energy level reduce due to decreased velocity gradient in shear layers downstream of the nozzle exit plane. The turbulence kinetic energy level peak on the upper side of the exhaust plumes decreases by 29.3%. The reasons are that the contact area between high-velocity core flow and the free stream decreases due to thicker fan flow and the velocity gradient in the core flow and free stream mixing region decreases because of the lower core flow velocity.

Copyright of Dokuz Eylul University Muhendislik Faculty of Engineering Journal of Science & Engineering / Dokuz Eylül Üniversitesi Mühendislik Fakültesi Fen ve Mühendislik Dergisi is the property of Dokuz Eylul Universitesi Muhendislik Fakultesi Fen ve Muhendislik Dergisi and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Aircraft must have reliable and sustainable sources of power systems and must use energy efficiently. Aircraft engine advances have dramatically improved aircraft fuel efficiency. Variable cycle engine (VCE) has been promising in both civil and military areas in the last decades. An important challenge for energy saving regarding the engine is to find optimum flight conditions. For this aim, this study investigated energetic and exergetic off-design performance modeling of the variable cycle turbofan engine with respect to flight conditions and potentially energy benefits for a new-generation combat aircraft. Current analysis mainly focused on how to simplify off-design performance model of the VCE in terms of thrust, specific fuel consumption (SFC), overall and exergy efficiencies with the aid of enhanced least-squares estimation-based genetic algorithm (LSEGA) in flight phases. According to analyses, the results show that the proposed method is capable of modeling all the thermodynamic off-design parameters with root mean square error values of as low as 0.000162 for exergy efficiency, 0.000311 for overall efficiency, 1.007 for thrust and 0.0763 for SFC. It is observed from the study that the proposed LSEGA algorithm has successfully converged into optimal solutions for all indexes and flight regimes and all the off-design performance models of the VCE energetic indexes are obtained with high accuracy. [ABSTRACT FROM AUTHOR]

To understand the jet flow characteristics of turbofan separate exhaust system, a parametric design method based on the initial Class Shape Transformation function was developed. HBPR and UHBPR turbofan separate exhaust systems were designed. Furthermore, the jet flow characteristics of the HBPR turbofan exhaust system under take-off condition with zero angle of attack were studied based on numerical simulation. The jet flow characteristics of the HBPR and UHBPR turbofan exhaust system under take-off condition with high angle of attack were also simulated. The effects of angle of attack and bypass ratio on the jet flow characteristics were investigated and the related flow mechanisms were analyzed. Results show that the axisymmetric plumes of the HBPR turbofan exhaust system are distributed around the engine axis under take-off condition with zero angle of attack. With the plug wake as the center, the core flow, the fan/core shear layer, the fan flow, the fan/free stream shear layer and the free stream are wrapped around the plug wake from inside out. Vortexes appear in the lee area at the back of the cowl and jet flow under take-off condition with high angle of attack. These vortexes cause cross sectional secondary flow and expose the highvelocity core flow to the low-velocity free stream. The contact area and velocity gradient in the mixing region among the free stream, fan flow and core flow increase. Therefore, the mixture among jet flow and free stream strengthens. So the high-velocity region, the high-vorticity region, and the high turbulence kinetic energy region shorten by 55.1%, 47.7% and 50.9% respectively. The vorticity values and turbulence kinetic energy level peak on the upper side of the exhaust plumes increase by about 30% and 87% respectively. Relative to these parameters from the HBPR turbofan exhaust system, the jet velocity peak value of UHBPR turbofan decreases by 5.5% under take-off condition with high angle of attack. The vorticity values and turbulence kinetic energy level reduce due to decreased velocity gradient in shear layers downstream of the nozzle exit plane. The turbulence kinetic energy level peak on the upper side of the exhaust plumes decreases by 29.3%. The reasons are that the contact area between high-velocity core flow and the free stream decreases due to thicker fan flow and the velocity gradient in the core flow and free stream mixing region decreases because of the lower core flow velocity. [ABSTRACT FROM AUTHOR]

The acceleration performance of turbofan engine is mainly limited by the surge boundary of high-pressure compressor (HPC). A certain amount of surge margin (SM) is reserved between the boundary and the acceleration schedule (AS) of acceleration control to avoid the risk caused by intake distortion, etc. However, the performance improvement by low SM design is the requirement for advanced engines. Hence it must execute a fault-tolerant strategy for the impact of sensor error, fuel metering error, etc. This paper proposes a method by adopting four ASs for weighted average to replace the single AS. The weights are altered by the multi-layer perceptron with reference to the real-time fuel results from four ASs, intake condition and rotor speed. For safety and accuracy, an exponential Gumbel loss function is introduced into the model training. The simulation results demonstrate that the method can significantly tolerate the impact of a single fault and the normal deviations of other factors without causing SM of HPC to be less than 3.6%. These also indicate that the acceleration time on the ground does not exceed acceptable 5 s, with a median that is 0.34 s less than the minimum method of two ASs within the flight envelope. • The method can tolerate a single fault without the surge and sharp performance drop. • The four dissimilar acceleration schedules are used for the total estimation accuracy. • An asymmetric loss function is introduced to balance the safety and performance. [ABSTRACT FROM AUTHOR]

Hybridized engines have become the focus of research nowadays in order to update the existing engines in different transportation sectors. This paper presents a hybridized aircraft engine consisting of a molten carbonate fuel cell system and a commercial turbofan system. The MCFC units are connected to a steam reforming and a water gas shift system. Also, five clean fuels are selected, such as dimethyl ether, hydrogen, ethanol, methane, and methanol, which are combined with different mass ratios to form five different fuel blends. The hybridized aircraft is investigated using three approaches: exergy analysis, exergoeconomic analysis, and exergoenvironmental analysis. It is found that the proposed engine has an average exergetic efficiency of 88% and an average exergy destruction ratio of 12%. The specific exergetic cost of electricity of the engine has an average value of 710 $/GJ for the high-pressure turbine and 230$/GJ for the intermediate and low-pressure turbines, as well as 50 $/GJ for the MCFC. The average specific exergoenvironmental impact of electricity is 14 mPt/MJ for turbines and 4 mPt/MJ for the MCFC. In addition, a blend of ethanol and hydrogen appears to be a viable option economically and environmentally. [Display omitted] • Five alternative fuels are chosen with different concentrations. • Hybridized MCFC-aircraft has 86%–89% high exergetic efficiency. • Hybridized MCFC-aircraft engine has 15% exergy destruction ratio. • The total annual levelized investment of the hybridized system is 76 k $/h. • The total component-related environmental impact rate is less than 40 mPt/h. [ABSTRACT FROM AUTHOR]

The analysis of complex systems typically requires a large and diverse ensemble of models to confront the richness and complexity of the problem. Nevertheless, a common development and validation process of each individual model can be rigorous and time consuming. Because of limited time and resources, it is sometimes unrealistic to model every individual object in the population to capture the complex phenomena of the system. One such challenge arises in aerospace engineering when only a very limited number of aircraft performance models can be built to cover the aircraft fleet of the world for the environmental impact modeling of air transportation system. This paper considers the problem of selecting a small proportion of representative models to sufficiently cover and represent the population for more efficient and accurate systems analysis. At the intersection of unsupervised data mining and high-dimensional data analysis, the proposed methodology uses minimax and multi-criteria considerations to select a representative model portfolio at each budget level. Applying on the case study of representative aircraft models for environmental impact modeling, the benefits of the proposed method are demonstrated through both data visualization and quantitative metrics in multiple experiments. Potential limitations, extensions, and broader impacts of the method are also thoroughly discussed. [ABSTRACT FROM AUTHOR]

Mode transition (MT) is critical for adaptive cycle engine (ACE) to achieve mission adaptability. There are many constraints for the MT, making the control law difficult to design. At present, most design methods require manual analysis by researchers. When the design parameters of an engine are changed, it takes a lot of time to redesign the control law. What is more, most control laws need to adjust not only the mode selection valve (MSV), but also many other variable geometry components (VGCs) simultaneously, which makes the control system design complex and difficult. In this study, a general design method based on the particle swarm optimization method and the sensitivity calculation method is presented. This method can derive the control law for the MT without manual analysis, improving the efficiency of the design process. At most, one VGC needs to be adjusted during the change of state of the MSV, simplifying the control system. The fluctuation of thrust and airflow is less than 2%, and the surge margin of the compressors is higher than 10%, leading to a safe and stable MT. This method can adapt to the adjustment of the cycle parameters of the engine and the deviation of component performance, making it suitable for the engine performance design stage. It can also be applied to the design for other types of ACEs. [ABSTRACT FROM AUTHOR]

To enhance the understanding of design characters, which have prominent influences during the fan blade out event, a simplified geometrical and dynamic analysis method was derived, and a typical 2-shaft high bypass ratio turbofan engine was selected and modeled. Based on analytical deriving and engineering experience learned from the real engine failure case, three determinative impact actions were recognized from the fan blade out process. The transient trajectories of these impact actions were researched in analytical method, and then thickness of acoustic lining, quantity of fan blades and threshold load of structural fuse were analyzed as key design characters. 36 serialized fan blade out transient dynamic simulations were conducted by using the 2-shaft high bypass ratio turbofan engine model within different combinations of the three key design factors. The results from geometrical and dynamic analysis matched mainly well with the results from simulations. Characteristic phenomenon in simulation can be explained theoretically. Five conclusions can be summarized from these results. (1) If thickness fan acoustic lining was thinner, the deviation between simplified analytical calculation and simulation were not outstanding to predict Blade-Casing the first impact time and angular position. (2) An appropriate thickness of acoustic lining could make a lower impact stress of fan casing at the first impact. (3) Different thickness of acoustic linings leaded to two impact modes for blade 2, which were tip impact and root impact. (4) Different impact conditions between blade 1 and blade 2 caused remarkable speed components distinction of blade 1, and leaded to a wide range of transient trajectory of blade 1 during FBO event. (5) Thicker acoustic lining in this research can usually find the porper threshold loads setting, which can give a satisfactory outbound vibration. Two details were raised for further research, which were impact behavior of composite material fan blade and honeycomb and influences of wider FBO threshold load ranges in design cases with thinner acoustic lining. [ABSTRACT FROM AUTHOR]

This study focuses on for a PW4000 high-bypass turbofan engine using energy, exergo-sustainable and performance viewpoint. For this aim, irreversibility and performance analyses are firstly performed for five main engine components at ≈260 kN maximum take-off thrust force. Besides, overall efficiency of the turbofan is determined to be 33 %, while propulsive and thermal efficiency of the turbofan are 72 % and 46 % respectively at 0.8 M and 288.15 K flight conditions. Secondly, calculation component-based exergetic assessment is carried out using exergetic indicators. According to the calculation, the exergetic efficiency of the engine is 32 %, while its waste exergy ratio is 0.678. Furthermore, exergetic sustainability measure is obtained as 0.473, while enviromental effect factor is 2.112. These indicators are also anticipated to help comprehend the connection between engine performance parameters and worldwide dimensions such as environmental effect and sustainable growth. [ABSTRACT FROM AUTHOR]

Large Eddy Simulation is performed using the NASA Source Diagnostic Test turbofan at approach conditions (62% of the design speed). The simulation is performed in a periodic domain containing one fan blade (rotor-alone configuration). The aerodynamic and acoustic results are compared with experimental data. The dilatation field and the dynamic mode decomposition (DMD) are employed to reveal the noise sources around the rotor. The trailing-edge radiation is effective starting from 50% of span. The strongest DMD modes come from the tip region. Two major noise contributors are shown, the first being the tip noise and the second being the trailing-edge noise. The Ffowcs Williams and Hawkings’ (FWH) analogy is used to compute the far-field noise from the solid surface of the blade. The analogy is computed for the full blade, for its tip region (outer 20% of span) and for lower 80% of span to see the contribution of the latter. The acoustics spectrum below 6 kHz is dominated by the tip part (tip noise), whereas the rest of the blade (trailing-edge noise) contributes more beyond that frequency.

The emphasis on increased turbofan fuel efficiency requires advanced turbofan designs that will integrate higher engine bypass ratios and shorter nacelles. The resulting acoustic signature of these designs will have a more broadband character as well as a smaller available area for liner installation. This two-fold impact compels a need for an improvement in the state of the art in liner technology. Increasing the acoustic absorption efficacy over a broader frequency range is a means to address this need. NASA investigated over-the-rotor acoustic liners for turbofan applications as a potential solution. This type of liner represents a significant advance over traditional liners due to placement in close proximity to the rotor. An advantage of placing treatment in this region is a modification of the acoustic near field, thereby inhibiting noise generation mechanisms. This can result in higher attenuation levels than could be achieved by the conventional sound absorption means. In addition, there is potential to integrate the liner with fan rub-strip and containment components, reducing engine components and thus weight, enabling a systematic enhancement in noise reduction and engine performance. This article reviews the development and evaluation process of three unique over-the-rotor concepts focusing on the discrete tests conducted across the Technology Readiness Level span. [ABSTRACT FROM AUTHOR]

The emphasis on increased turbofan fuel efficiency requires advanced turbofan designs that will integrate higher engine bypass ratios and shorter nacelles. The resulting acoustic signature of these designs will have a more broadband character as well as a smaller available area for liner installation. This two-fold impact compels a need for an improvement in the state of the art in liner technology. Increasing the acoustic absorption efficacy over a broader frequency range is a means to address this need. An acoustic liner development and optimization process was conceived and employed to achieve and demonstrate an improved broadband liner design concept. A series of increasing technology readiness level liner studies were conducted to enhance the optimization methodology while validating the concept. This progression spanned several NASA Aeronautics Research Mission Directorate programs/projects due to its relevance. This article reviews the development and evaluation process of the multi-degree-of-freedom liner technology concept from formation through simple experimental models to a flight test over an approximate 10-year period, focusing on the discrete tests comprising the development. [ABSTRACT FROM AUTHOR]

Presented herein is a comparative performance analysis of a novel turbofan engine with an auxiliary combustion chamber, nicknamed the TurboAux engine, against a turbojet engine, and a low bypass ratio turbofan engine with an afterburner is presented. The TurboAux engine is an adaption of the low-bypass ratio turbofan engine, but with secondary combustion in an auxiliary bypass annular combustion chamber for thrust augmentation. The TurboAux engine is envisioned with the desire to facilitate clean secondary burning of fuel at temperatures higher than in the main combustion chamber with air exiting the low-pressure compressor. The comparative study starts by analyzing the turbojet engine and its performance with and without an afterburner segment attached. In parallel, the conventional turbofan and its mixing counterpart are analyzed, also with and without an afterburner segment. A simple optimization analysis of a conventional turbofan is performed to identify optimal ‘fan’ pressure ratios for a series of low-bypass ratios (0.1 to 1.5). The optimal fan pressure ratios and their corresponding bypass ratios are adapted to demonstrate the comparative performance of the varying configurations of the TurboAux engine. The formulation and results are an attempt to make a case for charter aircrafts and efficient close-air-support aircrafts. The results yielded increased performance in thrust augmentation, but at the cost of a spike in fuel consumption. This trade-off requires more in-depth investigation to further ascertain the TurboAux’s utility.

Gas turbine engines, especially turbofan, have been famous for their fuel economy and reliability attributes. Therefore, these have continued to be manufactured by updating their features. Therefore, thermodynamic analyses related to turbofan engines have drawn great attention, providing deeper insight into potential improvements. New generation aircrafts have been conceived to draw bleed air as little as possible from their aero-engines so as to provide lower fuel consumption. In this study, influences of bleed air ratio (BAR) ranging from 1 % to 6 % on high by-pass turbofan (HBT) engine are handled by considering constant speed (CS) and constant thrust (CT) cases. Specific fuel consumption of HBT engine changes between 20.68 g/kN and 22.25 g/kN at CT whereas varies between 20.63 g/kN and 21.9 g/kN at CS owing to variation of BAR. Moreover, exergy efficiency of HBT resides between 26.92 % and 25.02 % at CT while changes 26.99 % and 25.43 % at CS. It shows that to maintain thrust constant could slightly penalty the engine performance in terms of fuel efficiency. On the other hand, the higher BAR leads to lower exergy efficiency of the combustor, which changes 80.95 %–82.33 % ranges at CT and varies 80.77 %–82.31 % intervals at CS. Finally, improvement potential rate for the combustor is found higher 1 MW and increases with elevated BAR whereas that for other five components is measured less than 0.04 MW. It could be underscored that adverse effect of BAR for both cases is observed. It is thought that this study helps in observing what extent the engine is affected from usage of bleed air in terms of thermodynamic metrics. • To perform performance analyses with respect to different bleed air ratios (BAR) under two cases. • To show how BAR affects exergetic metrics of six components under two cases. • To present influences of BAR on exergy-based sustainability parameters for the whole engine under two cases. [ABSTRACT FROM AUTHOR]

In a fan stage under windmilling conditions, the stator operates under negative incidence, leading to flow separation, which may present an unsteady behaviour due to rotor/stator interactions. An experimental study of the unsteady flow through the fan stage of a bypass turbofan in windmilling is proposed, using hot-wire anemometry. Windmilling conditions are reproduced in a ground engine test bed by blowing a variable mass flow through a bypass turbofan in ambient conditions. Time-averaged profiles of flow coefficient are independent of the mass flow, demonstrating the similarity of velocity triangle. Turbulence intensity profiles reveal that the high levels of turbulence production due to local shear are also independent of the inlet flow. A spectral analysis confirms that the flow is dominated by the blade passing frequency, and that the separated regions downstream of the stator amplify the fluctuations locked to the BPF without adding any new frequency. Phase-locked averaging is used to capture the periodic wakes of the rotor blades at the rotor/stator interface. A spanwise behaviour typical of flows through windmilling fans is evidenced. Through the inner sections of the fan, rotor wakes are thin and weakly turbulent, and the turbulence level remains constant through the stage. The rotor wakes thicken and become more turbulent towards the fan tip, where flow separation occurs. Downstream of the stator, maximum levels of turbulence intensity are measured in the separated flow. Large periodical zones of low velocity and high turbulence intensity are observed in the outer parts of the separated stator wake, confirming the pulsating motion of the stator flow separation, locked at the blade passing frequency. Space-time diagrams show that the flow is chorochronic, and a 2 D non-linear harmonic simulation is able to capture the main interaction modes, however, the stator incidence distribution could be affected by 3 D effects. [ABSTRACT FROM AUTHOR]

All rotating machines have vibrations and these vibrations have standard limits. The occurrence of various defects in the machines or non-observance of the permitted or standard values in repair works causes the amount of vibration to increase and consequently the parts to be damaged and cause irreparable damage. In this paper, the rotor and simulation of the rotor of a turbofan engine used in industry are investigated. The characteristics of this type of rotor are high performance, lightness, and low amplitude of vibrations. Various parameters such as rotational inertia, gyroscopic torque, rotational loading, the effects of mass imbalance, and instability in modeling have been investigated. Natural frequencies, critical velocity, and calculations have been used by Ansys software. The results of the numerical analysis and simulation were compared and there was a good agreement between these two modes of investigations, indicating the validity and accuracy of simulation assumptions. [ABSTRACT FROM AUTHOR]

The kinetic energy produced by a turbofan engine is inseparable from the unavoidable generation of waste heat dissipated into the environment and the chemical exergy of exhaust gases. However, exergoeconomic cost analyses of these propulsion systems have focused only on the formation process of the functional product and not the cost of residue formation. In this study, symbolic thermoeconomics was applied to evaluate the impact of residue formation on the production costs of a turbofan engine and analyze the effect of component malfunctions on the fuel impact formula for diagnosing anomalies. The GE90-115B high bypass turbofan engine under takeoff conditions and a thrust requirement of 510 kN was considered as a case study. The total exergoeconomic cost of the engine was 26,754.28 USD/h: 61.04% corresponded to external resources; 0.14% and 33.07% corresponded to waste heat dissipated from the bypass and core engine, respectively; 3.28% corresponded to the chemical exergy of the exhaust gases; 2.47% corresponded to capital and operating costs. A malfunction analysis revealed that a 1% reduction in the isentropic efficiency of the compressor reduced the total kinetic exergy by −0.77 MW, increased fuel consumption by 0.49 MW, and generated irreversibility and residue of 0.80 and 0.45 MW, respectively. [ABSTRACT FROM AUTHOR]

A hybrid-scheduling method, consisting of packing algorithm, genetic algorithm and priority promotion algorithm, was proposed for time-triggered CAN in this paper. We divided the basic cycles (BC) into synchronous phase for transmitting time-triggered messages and asynchronous phase for transmitting event-triggered messages. At the each end of BC, fault-tolerant windows were designed to improve the fault-tolerance. The First Fit Increasing and the genetic algorithm scheduled and optimized the transmission of time-triggered messages in the synchronous phase, and the priority promotion algorithm optimized the transmission of event-triggered messages in the synchronous phase. For the communication application of a TTCAN-based turbofan distributed control system, the new scheduling method improved the bandwidth utilization and arbitrary windows utilization to 99% and 9.3%. [ABSTRACT FROM AUTHOR]

The accurate evaluation of the lodging resistance of maize plants can provide a basis for the breeding of lodging-resistant cultivars and the regulation of cultivation measures. However, the traditional methods for evaluating maize lodging resistance in terms of plant morphology and stalk mechanical strength have certain limitations. The objective of this research was to develop a device for determining the critical wind speed of maize stalk breaking. The device was equipped with a centrifugal fan to supply airflow and was powered by a frequency conversion motor. The frequency converter adjusted the motor speed and thus adjusted the wind speed. The wind speed decreased first and then increased with increasing height above the outlet of the device, and maximum wind speed can reach 40 m/s. This device was convenient for transportation in the field, has a low cost, and can quickly, accurately, and objectively determine the lodging resistance. Field tests showed that the device ran stably for a long time. The coefficient of variation of three repeated measurements was between 1.5% and 4.8% for four maize cultivars. The new device can measure the critical wind speed of maize lodging and identify the lodging resistance for different maize cultivars, cultivation practices, and plant health conditions, and can thus overcome barriers to measuring the maize lodging resistance under natural wind conditions. [ABSTRACT FROM AUTHOR]

The problem of H ∞ control is investigated for turbofan systems with uncertain parameters and multiple disturbances in this paper. Some disturbances with partly known information are described via an external system, and other disturbances are assumed to be L 2 norm bounded. According to the disturbance-observer-based-control (DOBC) method and resilient H ∞ control technique, a robust resilient controller is designed to reject and attenuate the influence of these disturbances, and guarantees that closed-loop systems are asymptotically stable with H ∞ performance. Some solvable sufficient conditions are obtained based on the linear matrix inequality (LMI) technique and Lyapunov stability theory. Finally, a simulation is presented to show the robustness and effectiveness of the developed resilient anti-disturbance H ∞ control method. [ABSTRACT FROM AUTHOR]

Flow-mixing is common in technological processes, and both ejectors and turbofans can produce an interaction between flows with different energy potentials. Ejectors have been extensively used, and their analytical models have been widely presented. To the best of the authors' knowledge, there is a lack of studies exploring the efficiencies of turbofans. The goal of this paper is to compare thermodynamic processes in these devices. Their efficiencies are compared in terms of compression and entrainment ratios. A comprehensive one-dimensional subsonic thermodynamic models of the ejector and turbofan are presented. The quantitative indices are obtained for the same initial conditions expressed as the ratio of differences in enthalpies for ideal compression and ideal expansion. When initial conditions are equal to the numeric value of the combination of the isentropic efficiency of the evaluated components (numerical case 0.16), both devices have the same efficiencies; at lower initial conditions (numerical case 0.10), a turbofan's entrainment ratio is 1.5 times and compression efficiency 1.25 times higher; at higher values of initial conditions (numerical case 0.28), the ejector is more efficient. Such distinctive characteristics of turbofans and the nature of their variation may correspond to the specific application areas of technological equipment that require certain flow-mixing parameters. [ABSTRACT FROM AUTHOR]

Electronic Centralized Aircraft Monitoring (ECAM) parameters play a vital role in the operation of an aircraft to reduce the workload of the cockpit crew. A wide-body commercial aircraft with a triple-spool turbofan engine is examined within the scope of the study. This study is focused on the estimation of the ECAM primary engine parameters: Engine Pressure Ratio, Exhaust Gas Temperature, Fuel Flow, and Shaft Speeds without any additional measurement for data continuity. The recorded flight data obtained from a commercial aircraft is processed with machine learning methods, and the most suitable estimation method is tried to be determined. Correlation analysis is carried out for each data in the study to show strong predictor candidates. The modeling process is conducted by using MATLAB. Results indicate that the Fine Decision Tree is better at memorizing data, while the Wide Neural Network is better at generalizing data. Computational results show that the developed models are outstandingly precise and accurate to estimate aircraft's ECAM data to ensure flight safety for health and performance monitoring of an engine. Thus, when an unreliable situation occurs while performing the flight in practical conditions, the cockpit crew will be able to overcome this situation by Digital Twin. • Predicting the primary engine parameters using machine learning methods. • Creating the Digital Twin for Electronic Centralized Aircraft Monitoring (ECAM). • Proposing a software-based system for flight reliability and safety. • Providing health and performance monitoring for a turbofan engine. [ABSTRACT FROM AUTHOR]