1,721,030 research outputs found
A Methodology for the Comparative Analysis of Hybrid Electric and All-Electric Power Systems for Urban Air Mobility
Full text linkThe present investigation addresses the topic of Urban Air Mobility with particular reference to the air-taxi service with electrified power systems. A new and detailed methodology is proposed for the simplified design and energy analysis of conventional, hybrid-electric, and full-electric power systems for this application. The original contributions to the scientific literature on UAM are the detailed modeling approach, the evaluation of CO2 emissions with a Well-to-Wing approach as a function of the electricity Emission Intensity factor, and the comparison with road vehicles performing the same route in different driving conditions. The comparison demonstrates the advantages of a full electric air-taxi with today’s technology versus a hybrid-electric road taxi, especially in cases involving low emission intensity and unfavorable driving conditions (congested traffic, aggressive driving style, and high circuity factor values). In the case of 2035 technology, the comparison with a referenced fully electric road vehicle is detrimental to the air taxi but the values of Well-to-Wheel/Wing CO2 with the expected Emission Intensity of 90 g/kWe for the European Union are still quite low (67 g/km). The investigation also quantifies the negative effect of battery aging on the consumption of the air taxi and on the number of consecutive flights that can be performed without fully charging the battery
Energy consumption and environmental impact of Urban Air mobility
Full text linkUrban Air Mobility (UAM) is a recent concept proposed for solving urban mobility problems, such as urban traffic pollution, congestion, and noises. The goal of this investigation is to develop a backward model for an electric aerial taxi in order to estimate the electric consumption and the indirect emissions of carbon dioxide in a specified mission. The model takes as input the time histories of speed and altitude and estimates the power at the rotor shaft during the mission with a quasi-static approach. The shaft power is used as input for the electric drive where the motor is modelled with an efficiency map and a transfer function while an equivalent circuit model which includes aging effects is used for the battery. The emissions of CO 2 are calculated as a function of the Greenhouse emission intensity and compared with that of a hybrid electric taxi performing the same mission with the same payload. A plug-in Toyota Prius modelled through the software ADVISOR is considered for the comparison. The results show that the air taxi behaves better than the road taxi not only in terms of trip time but also from the environmental point of view if the charging of the battery is performed with the emission intensity factory expected to be reached in Europe in 2025
Numerical Investigations on the Working Cycle of a Hydraulic Breaker: Off-Design Performance and Influence of Design Parameters
No full text
Supply Chain Resilience in Hydrogen Valleys: Addressing Challenges and Opportunities in Green Hydrogen Ecosystems
No full textThe transition to sustainable energy systems is increasingly dependent on the resilience of supply chains, particularly in the emerging field of Hydrogen Valleys, which serve as integrated hubs for hydrogen production, storage, and distribution. Despite the promise of hydrogen as a clean energy carrier, supply chain disruptions and vulnerabilities pose significant challenges to large-scale implementation. This study addresses these challenges by developing a comprehensive framework of resilience indicators tailored to Hydrogen Valleys. The objective of the research is to evaluate how these energy ecosystems can withstand and adapt to external disruptions while contributing to long-term sustainability goals. To achieve this, the study employs a systematic literature review combined with an indepth analysis of key hydrogen projects. The review identified gaps in current resilience strategies and examined the application of concepts such as flexibility, redundancy, and management of risks across the hydrogen value chain. The project analysis provided practical insights into the challenges and opportunities faced in real-world applications of hydrogen infrastructure. The findings highlight the critical role of technological innovation, stakeholder collaboration, and regulatory consistency in enhancing supply chain resilience. The study demonstrates that although significant progress has been made in hydrogen production technologies, unresolved financial and regulatory barriers continue to hinder the scalability of Hydrogen Valleys. This research contributes to the ongoing discourse on energy resilience by offering a structured approach for evaluating and strengthening the resilience of hydrogen supply chains and provides actionable recommendations for policymakers and industry leaders aiming to foster sustainable energy transitions
FUEL CELL BASED-ON POWERTRAIN TO HYBRIDIZE SMALL UNMANNED AERIAL VEHICLES
No full textThe proposed investigation aims at increasing the
endurance of a small unmanned aerial vehicle (UAV) where the
power request for propulsion can be satisfied by means of a
battery and a fuel cell. The hybrid configuration allows the
required power to be obtained at take-off and the fuel cell to
support the battery in order to maintain the state of charge (SOC)
in the other phases of flight. This operating mode avoids deep
discharging, when the battery SOC falls down a suitable
threshold, and overcharging, which exposes to risk of explosion in
case of lithium batteries. The cost of adding different capacity
batteries was evaluated in terms of the increase of mass and
consequently decrease of endurance. The power split was
conveniently defined at take-off to prevent from excessive
hydrogen consumption and to maximize the endurance with
respect to the non-hybrid configuration in which the only fuel cell
is used
The pyrolysis and gasification pathways of automotive shredder residue targeting the production of fuels and chemicals
Full text linkAutomotive shredder residue (ASR), also referred to as car fluff, is the 15-25% of end-of-life vehicle’s mass remaining after de-pollution, dismantling, shredding of the hulk and removal of metals from the shredded fraction. ASR typically consists of metals, plastics, rubber, textile, wood and glass, and is commonly landfilled. The use of ASR as a fuel in incineration processes is controversial since toxic pollutants can be generated as by-products if operational conditions and gas cleaning systems are not carefully controlled. Thermochemical treatment of ASR consists of advanced technology processes that convert ASR components liable to decomposition under the application of heat into liquids and/or gases and a solid residue containing metals. Within the thermochemical treatment options for ASR, pyrolysis and gasification are generally considered as the emerging technologies. The pyrolysis process uses medium temperatures (400-600°C) and an oxygen-free environment to decompose ASR chemically, thus producing minimum emissions and allowing metals to be recovered. Gasification is operated at higher temperatures (>700-800°C) and typically uses air as a gasification agent, which raises some issues in terms of emissions. Lab and pilot-scale plants fed with ASR have been built using both technologies, also considering a combination of them. The aim of this paper is the identification of the best conversion pathway for the production of transportation fuels, aviation fuels or chemicals (hydrogen, methanol, etc.) from ASR. The intermediate products from gasification and pyrolysis are used as feedstock in secondary processes for the production of the final products. The heterogeneous and complex composition
of ASR raises several challenges upon its thermochemical treatment, so that the second step of the conversion process is typically not even addressed. Instead, this further step is fundamental to obtain some valuable products that can directly replace fossil derived fuels or chemicals. The updated picture presented in this work should help identify the main advantages and drawbacks of the pyrolysis and gasification processes when considered part of an overall ASR to fuels or chemicals plant
Dielectric barrier discharge plasma actuator effect on unsteady aerodynamic behavior of a pitching airfoil
No full textAirfoils shelf life is strongly reduced by the application of unsteady loads, which can bring to fatigue phenomena and non-stable performance of the device. In this context, this paper carries out an evaluation of an unsteady application of Dielectric Barrier Discharge Plasma Actuator (DBD-PA) to reduce loads variability on a pitching airfoil, with the aim to increase the aerodynamic profiles durability and thus to increase airfoil stability. The comparison, in order to evaluate the effect of actuators dimensions, involves two different devices, with a high voltage electrode length one order of magnitude different
Neural nonlinear autoregressive model with exogenous input (Narx) for turboshaft aeroengine fuel control unit model†
Full text linkOne of the most important parts of a turboshaft engine, which has a direct impact on the performance of the engine and, as a result, on the performance of the propulsion system, is the engine fuel control system. The traditional engine control system is a sensor-based control method, which uses measurable parameters to control engine performance. In this context, engine component degradation leads to a change in the relationship between the measurable parameters and the engine performance parameters, and thus an increase of control errors. In this work, a nonlinear model predictive control method for turboshaft direct fuel control is implemented to improve engine response ability also in presence of degraded conditions. The control objective of the proposed model is the prediction of the specific fuel consumption directly instead of the measurable parameters. In this way is possible decentralize controller functions and realize an intelligent engine with the development of a distributed control system. Artificial Neural Networks (ANN) are widely used as data-driven models for modelling of complex systems such as aeroengine performance. In this paper, two Nonlinear Autoregressive Neural Networks have been trained to predict the specific fuel consumption for several transient flight maneuvers. The data used for the ANN predictions have been estimated through the Gas Turbine Simulation Program. In particular the first ANN predicts the state variables based on flight conditions and the second one predicts the performance parameter based on the previous predicted variables. The results show a good approximation of the studied variables also in degraded conditions
Active control of unsteady cavitating flows in turbomachinery
No full textA preliminary 2D numerical investigation of the active control of unsteady cavitation by means of one single synthetic jet actuator (SJA) is presented. The SJA has been applied to hinder the intrinsic instabilities of a cloud cavitating flow of water around a NACA 0015 hydrofoil with an angle of attack of 8° and ambient conditions. It has been placed inside the inception region at a distance of 16% of the chord from the leading edge. Concerning the numerical approach, a Eulerian homogeneous mixture/mass transfer model has been used, in combination with an extended Schnerr-Sauer cavitation model and a Volume of Fluid (VOF) interface tracking method. The synthetic jet has been modeled by means of a user-defined velocity boundary conditions based on a sinusoidal waveform. A sensitivity analysis has been first performed in order to evaluate the influence of the main control parameters, namely the momentum coefficient Cμ, the dimensionless frequency F+ and the jet angle αjet. By combining the cavitating vapor content and the impact on the hydrodynamic performance, the best performing SJA configuration has been retrieved. Then, a deeper analysis of the vapor cavity dynamics and the vorticity field has been conducted in order to understand the modification of the main flow produced by the synthetic jet. The best SJA configuration was observed at Cμ = 0.0002, F+ = 0.309 and αjet = 90°, which led to a reduction of both the average vapor content and the average torsional load in the measure of 34.6% and 17.8% respectively. A reduction of the average pulsation frequency of the pressure upstream confirmed the beneficial effect of the SJA. The analysis of the coupled dynamics between vapor cavity-vorticity and their POD-based modal structures highlighted that the benefit of the SJA lies on preventing the growth of a thick sheet cavity which tends to cause the development of the highly cavitating cloud dynamics after the cavity breakup. This is mainly due to an additional vorticity close to the hydrofoil surface just downstream the SJA, as well as a local pressure modification close the SJA during the blowing stroke
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