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Browsing FE - DCA | Documentos por Auto-Depósito by Sustainable Development Goals (SDG) "07:Energias Renováveis e Acessíveis"
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- How different are conventional and biofuel sprays applied to aviation? An infodynamic comparative analysisPublication . Ferrão, Inês Alexandra dos Santos ; Panão, Miguel Rosa Oliveira; Mendes, Miguel; Moita, Ana Sofia Oliveira Henriques; Silva, André Resende Rodrigues daThe transition from fossil to sustainable and alternative fuels is imperative to address environmental concerns and meet energy requirements. Thus, the implementation of alternative fuels requires a deeper investigation of spray behavior. This study explores conventional jet fuel (Jet A-1) and hydrotreated vegetable oil (HVO) in terms of breakup length and spray dynamics over a wide range of operating conditions. The normalized mean breakup length was measured, and an empirical correlation was developed based on the experimental data. Focusing on the droplet sizes in fuel sprays, which are critical for optimizing combustion, an informational perspective for comparative analysis was explored. The terms informature, infotropy, and infosensor were introduced to quantify and capture the non-deterministic nature of physical systems. The results revealed similar drop size distributions for HVO and Jet A-1, with the Gamma function effectively characterizing the distributions. Both fuels exhibit spray evolution toward higher complexity states, emphasizing the role of aerodynamic forces and minimum development distance in atomization. The new lexicon of infodynamics views sprays as networks of information flow, with infotropy indicating that both fuels produce sprays with similar degrees of transformation. HVO is endorsed as a viable alternative with broader implications for sustainable aviation solutions and understanding complex engineering processes.
- Splashing correlation for single droplets impacting liquid films under non-isothermal conditionsPublication . Rodrigues, Daniel de Almeida Vasconcelos ; Barata, Jorge Manuel Martins ; Silva, André Resende Rodrigues daThe droplet impact phenomenon onto liquid films is predominant in a variety of modern industrial applications, including internal combustion engines and cooling of electronic devices. These are characterised by heat and mass transfer processes, such as evaporation, condensation and boiling. However, studies regarding droplets and liquid films under non-isothermal conditions are scarce in the literature and do not explore temperature-dependent phenomena. Due to this, the main objective of this work is to evaluate the influence of temperature on the splashing occurrence of single droplets impinging onto liquid films under the presence of a heat flux. The crown evolution is evaluated qualitatively to provide insight regarding breakup mechanisms. Water, n-heptane and n-decane are the fluids considered for the current study, as these provide a wide range of thermophysical properties and saturation temperatures. The splashing dynamics are evaluated by varying the droplet impact velocity and dimensionless temperature of the liquid film. Qualitative results show that an increase in the liquid film temperature leads to the transition from spreading to splashing, which is less evident for fuels in comparison with water. For water and n-heptane, the formation of cusps on the crown rim is promoted, which is associated with ligament breakup. For n-decane, the crown rims are relatively homogeneous in terms of shape and size, whereas the atomisation process varies a function of the liquid film temperature. Visually, the secondary droplets exhibit a greater size in comparison with lower temperatures. Transitional regimes display some irregularities, such as splashing suppression/reduction, which require further attention. In terms of splashing correlation, the authors propose to develop a non-splash/splash boundary for both iso- and non-isothermal conditions. Results show that the splashing threshold is dependent on the thermophysical properties and the dimensionless temperature of the liquid film.
- Sustainable Aviation Fuels and their impact in commercial airport operationPublication . Magalhães, Leandro; Santos, Luis; Ferreira, Ana Filipa; Silva, André Resende Rodrigues daWith global air traffic projected to grow annually by approximately 3.8%, the aviation sector faces increasing pressure to implement effective strategies for mitigating its environmental impact, particularly with respect to greenhouse gas emissions. Sustainable Aviation Fuels represent a critical pathway for decarbonizing aviation by offering a lower-emission alternative to conventional jet fuels. This study evaluates the environmental impact of SAFs on specific operational phases of flight, with a focus on the landing and take-off cycle. A case study was conducted at Lisbon Airport using real aircraft movement data over a one-week period. Emissions were calculated by correlating aircraft engine types with data from the ICAO Engine Exhaust Emissions Databank. The analysis identifies the most emission-intensive flight phase, the most polluting fleet, and evaluates the potential GHG reductions achievable through the use of various SAF pathways. Additionally, operational alternatives for reducing emissions during the taxi phase, including APU management strategies, are examined. The results provide actionable insights into the role of SAFs in reducing airport-level emissions and support targeted interventions for more sustainable airport operations.
- Thrust force assessment of a MFC-actuated tail-like robotic fish using Unsteady Panel MethodPublication . Silva, Maíra Martins da ; Camacho, Emanuel António Rodrigues ; Silva, André Resende Rodrigues da ; Marques, Flávio D.Fish-like robots are used in various fields, such as environmental monitoring and underwater exploration. These devices are designed to emulate the motion of a real fish. They can have flexible bodies to mimic body/caudal-based locomotion patterns or fins to mimic median/paired fin-based locomotion patterns. Standard propulsion methods include oscillating fins, flapping tails, and body undulations. This work investigates a robotic fish with a flexible tail actuated by a Macro-Fiber Composite (MFC) pair in a bi-morph configuration. This device is designed to mimic body/caudal-based locomotion patterns; therefore, it should present propulsion capabilities due to its body undulations. These propulsion capabilities are assessed using the Unsteady Panel Method for different sinusoidal inputs. This method requires the device’s kinematics, which is derived using an analytical model based on the Euler–Bernoulli beam theory, considering the electro-mechanical coupling of the actuators. The mean thrust force derived using the Unsteady Panel Method is compared with the actual mean thrust acquired during an experimental campaign. The experimental and numerical results indicated that higher thrust forces can be achieved when the device is excited in its second resonance frequency. These results are in line with Lighthill’s findings.