• Energy Research

This volume contains the charts and backup material presented to the Atomic Energy Commission and Air Force on June 14, 1962 concerning General Electric's Nuclear Materials and Propulsion Operation (formerly the Aircraft Nuclear Propulsion Department), during its work on the development of a nuclear power plant for manned aircraft.

Abstract In recent years the concept of “more electric aircrafts” has established itself increasingly and the electrical power systems for aircrafts are in progress. In this context, fuel cells represent a valid source of electric power for the advantages in terms of pollution emissions, noise reduction and fuel consumptions. In this study, the authors analyzed the feasibility, from the specific energy point of view, in using a PEM fuel cell power system as APU unit in a more electrical aircraft with respect to a battery system installation. The proposed fuel cell system has a modular architecture and consists of fuel cell stacks, air compressors, heat exchangers, compressed hydrogen tanks and auxiliary batteries. The analysis has been performed by applying a design methodology based on an optimization procedure concerning the size and the efficiency of each power system component in order to reach the maximum specific energy (higher than 500 W h/kg). Moreover, a “black-box”-type model of the power system has been developed to support the optimization methodology in the evaluation of its performance in terms of electric power production, heat production, auxiliary systems consumption and hydrogen consumption. Results pointed out the advantages of the PEM fuel cell application in a more electric aircraft; as a matter of fact for assigned mission requirements, according to the specifications defined in the Long Endurance Demonstrator (LED) project promoted by CIRA (Italian Aerospace Research Centre), the specific energy of the designed power system results to be equal to 0.51 kW h/kg. This value is very interesting if compared to the specific energy of commercial LiPo batteries characterized by 0.2 kW h/kg.

As global warming intensifies, the world is increasingly concerned about carbon emissions. As an important industry that affects carbon emissions, the air transportation industry takes on the important task of energy saving and emission reduction. For this reason, major airlines have designed or will design different kinds of new-energy aircraft; however, each aircraft has a different scope of application according to its energy source. Biofuels have an obvious carbon emission reduction effect in the whole life cycle, which can offset the drawback of the high pollutant emission of traditional fossil fuels in the preparation and combustion stages. At the same time, a battery has zero emissions in the operating condition, while the low energy density also makes it more applicable to short-range navigation in small aircraft. In this paper, the development direction of a biofuel–electric hybrid aircraft is proposed based on the current development of green aviation, combining the characteristics of biofuel and electric aircraft.

This paper focuses on the estimation of the aircraft mass in ground-based applications. Mass is a key parameter for climb prediction. It is currently not available to groundbased trajectory predictors because it is considered a competitive parameter by many airlines. There is hope that the aircraft mass might become widely available someday, but in the meantime it is possible to estimate an equivalent mass from the data already available, assuming the thrust to be known (maximum or reduced climb thrust for example). In a previous paper, two mass estimation methods were compared using simulated data. In this paper, we compare these two mass estimation methods using Mode-C radar data. Both methods estimate the aircraft mass by fitting the modeled energy rate (i.e. the power of the forces acting on the aircraft) with the energy rate observed at several points of the past trajectory. The first method dynamically adjusts the weight parameter so as to fit the energy rate, using an adaptive sensitivity parameter to weight each observation. The second method, introduced in one of our previous publications, estimates the mass by minimizing the quadratic error on the observed energy rate, taking advantage of the polynomial expression of the modeled power when using the BADA model.The actual mass is unavailable in our radar data. However, we can use the estimated mass to compute a trajectory prediction. This prediction is then compared to the actual trajectory giving us some insight on the accuracy of the estimated mass. We have compared the obtained predictions with the ones obtained using the BADA reference mass. The root mean square error on the predicted altitude is reduced by 45 % using the least squares method. With the adaptive method this error is divided by two.

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.

This article presents a numerical model of an aeronautical hybrid electric propulsion system (HEPS) based on an energy method. This model is designed for HEPS with a total power of 100 kW in a parallel configuration intended for ultralight aircraft and unmanned aerial vehicles (UAV). The model involves the interaction between the internal combustion engine (ICE), the electric motor (EM), the lithium battery and the aircraft propeller. This paper also describes an experimental setup that can reproduce some flight phases, or entire missions, for the reference aircraft class. The experimental data, obtained by reproducing two different take-offs, were used for model validation. The model can also simulate anomalous operating conditions. Therefore, the tests chosen for the model validation are characterized by the EM flux weakening (“de-fluxing”). This model is particularly suitable for preliminary stages of design when it is necessary to characterize the hybrid system architecture. Moreover, this model helps with the choice of the main components (e.g., ICE, EM, and transmission gear ratio). The results of the investigation conducted for different battery voltages and EM transmission ratios are shown for the same mission. Despite the highly simplified model, the average margin of error between the experimental and simulated results was generally under 5%.

Deterioration of axial compressors is in general a major concern in aircraft engine maintenance. Among other effects, roughness in high-pressure compressor reduces the pressure rise and thus efficiency, thereby increasing the specific fuel consumption of an engine. Therefore, it is important to improve the understanding of roughness on compressor blading and their impact on compressor performance. To investigate the surface roughness of rotor blades of a compressors, different stages of an axial high-pressure compressor and a first-stage blisk (BLade–Integrated–dISK) of a regional aircraft engine is measured by a three-dimensional laser scanning microscope. Fundamental types of roughness structures can be identified: impacts in different sizes, depositions as isotropically distributed single elements with steep flanks and anisotropic roughness structures direct approximately normal to the flow direction. To characterise and quantify the roughness structures in more detail, roughness parameters were determined from the measured surfaces. The quantification showed that the roughness height varies through the compressor depending on the stage, position and the blade side. Overall complex roughness structures of different shape, height and size are detected regardless of the type of the blades.

Specific excess power (Ps) contours that can be obtained using the energy method; these are important contours that show the performance limits of the aircraft, allow the performance comparison of different aircraft, and help determine the trajectory corresponding to the minimum time to climb without the need for any mathematical operation. Due to the difficulties associated with obtaining Ps contours, there are not many studies on this subject. In order to overcome these difficulties, within the scope of this study, an estimation model was created that will easily predict the Ps contour depending only on flight altitude and Mach number. The data required for modeling are Ps contours obtained in a different study for B737-800 aircraft in 4 different flights. Although it is new, the cuckoo search algorithm (CSA) method, which has proven its success in many optimization problems, has been used for modeling and highly accurate results have been obtained. A different metaheuristic method, particle swarm optimization (PSO), was used to measure the accuracy of the model created. These models constitute the first attempt in the current literature; furthermore the datasets used include real Flight Data Recorder (FDR) values. © 2023 Elsevier Ltd