This article describes the performance of carbon fibre brush seals for high pressure applications whilst addressing the importance of the robustness of the brush seal structure. Brush seals are usually manufactured through crimping of the fibre pack between two annular aluminum fine structures. The simplicity of this setup and low bulk compromise however the life service of the brush seal because of uprooting. Here, assembled brush seals with a non-conventional arrangement, with the fibre pack being oriented against the flow direction, could be tested for the first time at differential pressures up to 10 bar. They exhibited remarkably low air consumption. This was however achieved at the expense of high friction, whose effects have to be mitigated to avoid seal destruction. Brush seals were also submitted to endurance testing under lubricated conditions at low pressures, and after 300 hours, the performance degradation was negligible. The brush seal adapted assembly successfully prevented uprooting arising to fibre friction combined to high rotational speed, and renews promising prospects in the use of carbon fibres for challenging sealing conditions.

Hybrid rocket engines (HREs) are a category of chemical rocket propulsion systems in which the two propellants are stored in different states of matter. They have been often overlooked due to their lower performance with respect to conventional liquid rocket engines, and increased complexity over solid rocket motors. Recently, HREs are gaining new momentum for small launcher applications, as their performance is coupled with intrinsic safety, throttle-ability, flexibility and low cost, promising advantages when aiming to build a cost-effective space transportation system. Taking advantage of a hybrid rocket slab burner, an experimental HRE where a two-dimensional solid fuel grain is tested in a combustion chamber with optical access, the combustion behavior of paraffin wax with oxygen has been investigated, measuring the regression rate of the fuel and acquiring high-speed video recordings of the combustion. Multiple tests have been performed under different oxidizer mass flux and combustion chamber pressure conditions, grouped into four main experimental campaigns, providing insights into the fuel regression rate dependence on these parameters, allowing to trace the experimental correlation between oxidizer mass flux and fuel regression rate. Then, taking advantage of the video recordings of the combustion, phenomena such as liquid droplets entrainment have been visualized, as well as a qualitative description of the combustion behavior at different combustion chamber pressure and oxidizer mass flux. The effect of the oxidizer mass flux on the regression rate of the paraffin slab has been assessed, and the experimental data proved to be in accordance with the predictions coming from literature, as an increase in mass flux correlates with an increase in the measured regression rate. The effect of pressure at low mass fluxes, however, has not been clearly assessed in the study, and further investigations are required for future studies.

The Wallonia region of Belgium aims to transition to a modern hydrogen infrastructure. Given the relatively low density of hydrogen gas, it is important to understand its nature and behavior during transport through pipelines. This study aims to observe the pressure loss in pipelines due to surface roughness with H2 and other singular losses to find a solution to minimize the amount of pressure loss that occurs during transportation. This study involves numerical methods and gas equation models to determine the pressure loss. This analysis includes the properties of hydrogen gas, the pipeline material used, the friction factor, pipeline efficiency, and other relevant properties of hydrogen and pipelines. To address this challenge, the study integrates numerical fluid dynamics methods with structural modelling of pipeline walls. It accounts for long-term friction effects, erosion over several years, radial pressure gradients (mixing pressure drop), acceleration effects, and gravity influences, considering the non-ideal behavior of gaseous hydrogen (GH2). This study provides a systematic comparison between AGA-based analytical models and CFD simulations using a scaled pipeline approach, enabling reliable estimation of pressure losses in long-distance hydrogen pipelines. The proposed methodology integrates scaling, numerical validation, and CFD simulation to compute pressure losses in a hydrogen pipeline.

An improved design of a hybrid solar system with pumped storage using pump-as-turbines is proposed through an innovative approach that introduces the pumped storage factor as a design criterion, while also utilizing the grid as an energy storage medium in a case study. This design aims to meet the operational demands of the transposition system known as the Tucuru & iacute; Locks and to operate the hydraulic system efficiently. The originality of the solution lies in the design of solar-pumped storage hybrid systems, in which a design factor is proposed to minimize energy costs. A design methodology is proposed to determine the best value of the pumped storage factor (beta) alongside the lowest Levelized Cost of Energy (LCOE). This factor represents the percentage of energy that can be stored by pumping, maintaining the balance of energy to meet the demand. The analysis incorporates performance curves in both direct and reverse modes, as well as energy purchase and sale costs and tariffs. Different numbers of pump/PaTs are evaluated. A combination of Yang's and Rossi's methods is employed to construct complete performance curves and assess technical feasibility, with validation using experimental data from the literature, providing a comprehensive analysis of the PaTs operating region. The methodology is applied and validated through a case study in Brazil. The results demonstrate that the best factor, beta = 34%, yields the lowest LCOE of 0.1133 $/kWh with a single PaT, using 11,520 m3 of water for operation, achieving a payback time of up to 2.6 years, and delivering superior performance compared to other projects of the same nature. This approach, therefore, presents an innovative solution to the energy storage challenge, offering crucial insights for researchers and decision-makers on a novel method for designing hybrid energy storage systems. Additionally, the methodology allows for extended application in other scenarios, with or without grid storage.

Water Supply and Distribution Networks (WSDNs) offer underexplored potential for energy recovery. While many studies confirm their technical feasibility, few assess the long-term operational compatibility and economic viability of such solutions. This study evaluates the energy recovery potential of the Brussels Capital Region’s WSDN using four years (2019–2022) of operational data. Rather than focusing on available technologies, the analysis examines whether the real behavior of the network supports sustainable energy extraction. The approach includes network topology identification, theoretical power modeling, and detailed flow and pressure analysis. The Brussels system, composed of a Water Supply Network (WSN) and a Water Distribution Network (WDN), reveals strong disparities: the WSN offers localized opportunities for energy recovery, while the WDN presents significant operational constraints that limit economic viability. Our findings suggest that day-ahead electricity markets provide more suitable valorization pathways than flexibility markets. Most importantly, the study highlights the necessity of long-term behavioral analysis to avoid misleading conclusions based on short-term data and to support informed investment decisions in the urban water–energy nexus.

The aviation industry poses a significant challenge to achieving the ambitious goals outlined by initiatives like the European Green Deal, aiming for net-zero greenhouse gas emissions by 2050 and stabilizing global temperatures at 1.5 °C above pre-industrial levels. In this context, Lighter-Than-Air (LTA) technologies emerge as promising solutions for decarbonization, providing a potential relief to the substantial emissions associated with traditional aviation practices. LTA vehicles, such as airships, leverage buoyancy to significantly reduce fuel consumption and emissions. Furthermore, modern technological advancements enable LTA technology to address pressing environmental concerns, including noise pollution, land use, and infrastructure requirements, all while ensuring heightened levels of safety and operational efficiency compared to previous initiatives. These advancements hold particular promise for critical sectors such as Intelligence, Surveillance, and Reconnaissance (ISR), monitoring, freight transport, and humanitarian aid. However, challenges such as weather-related operational constraints, scaling difficulties, and a notable lack of compelling and reliable data impede the development of current initiatives. Through a comparative analysis with conventional aviation technologies, this study underscores the potential of LTA technology to overcome existing operational limitations, while offering a more sustainable and environmentally friendly alternative.

Pumped storage is an environmentally friendly method for electricity storage that generates minimal CO2 emissions compared to alternative storage solutions. This paper focuses on the current state-of-the-art pumped storage penstocks, which serve as conduits for high-pressure liquid flow between vertical reservoirs. Examining the dynamic response of these penstocks reveals that the water hammer induced by the turbine inlet valve's (TIV) closure increases the equivalent stress on the penstock material. Notably, the water hammer effect is negligible in low head pumped storage scenarios. This study confirmed that utilizing seawater yields minimal disparities in the dynamic pressure response of the penstock element. Furthermore, the Mach number and velocity distribution exhibit no significant differences in the context of low-head pumps.

Pump As Turbine (PAT) utility represents a major advance in the field of hydraulic engineering. This work aims to improve the PAT performance characteristics. The sharp impeller leading edge (original impeller) was revealed by flow analysis as exhibiting negative effects on the PAT performances due to flow separation and flow misalignment. The performances of rounded and original impeller leading edge were studied by Computational Fluid Dynamic (CFD) method carried out on ANSYS CFX. Although impeller leading edge rounding has notably improved the performances in off design conditions, the difference of efficiency between the both impeller types was decreasing when increasing the discharge. The hydraulic head generated by the rounded impeller leading edge was also slightly higher at part load conditions, but when increasing the discharge, the difference between the both heads became negligible. It appeared from numerical simulations that the impeller leading edge rounding allows to decrease the hydraulic losses of the individual sub-domains except the outlet pipe. For the seek of a comprehensive analysis, the significant losses were computed for the two impeller geometries. It was observed that the shock losses and swirling losses of the rounded impeller leading edge were lower at part load conditions, but when increasing the discharge, the both losses were lower for the original impeller geometry. The rounded impeller leading edge exhibited as well lower wall frictional losses for the entire operating range of discharge.

Hydrokinetic Banki turbines present an affordable, technically feasible, environmentally friendly technology. Their construction without requiring more expensive structures like diversion weirs, canals, forebay, and penstock, makes their initial investment much lower than commonly used horizontal Banki turbine of the same capacity. The possibility to install in the existing canals for Ultra Low Head applications is the additional motivating factor for this research. The system studied includes two Banki runners without internal shafts mounted vertically side by side surrounded by nozzle and diffuser structures. In the first scenario, Nozzle and then the Nozzle-diffuser augmented structures were separately studied to enhance the output of the runner for ultra-low head application, and the effects of each on the speed, pressure, and power output were analyzed. For the case of commonly used Banki, without nozzle and diffuser augmentation the speed for Ultra Low Head was minimum and determined to be 344rpm, which is far below the recommended value of 800rpm for safe operation at a flow rate of 1m3/s. In view of this, in the present study the enhanced speed on account of improvement was found to be 850rpm and 1025rpm for the design without and with diffuser assemblies respectively. Besides, the performance is seen to be improved by 7.6% with the diffuser as compared with the one without diffuser assembly. Detailed simulation results are presented and discussed: 3D ANSYS-FLUENT optimization result provided optimum number of blades for each runner to be 19 and with the optimum throat width in both cases as 202mm. On account of the lack of any results reported so far for this innovative geometry, validation of the simulated results was carried out with reported results for the dual horizontal axis Banki turbines with good agreement.

Seawater pumped storage consists of pumping water from the sea to an upper reservoir to store electricity. The use of seawater as the fluid results in an erosion mechanism due to the presence of solid particles. In this paper, we study the effect of the fluid content on the performance of low-head pumps in the blade-to-blade section. The loss of blade thickness may cause damage due to the water pressure applied to the blade section. From our study, we conclude that the resulting erosion depends on the absolute velocity distribution whereas the thickness loss depends on the particle size, density, and velocity. For hydraulic pumps, erosion of the blades is more likely to occur at their trailing edge. A reduction of the blade orthogonal thickness to 10

Interest of Pump as Turbine (PAT) is growing with diverse applications in engineering. Usually, the data of PATs are not available in the hands of pump manufacturers. Therefore, performance prediction methods appear as an important research area of PATs. The current prediction methods reposed on expensive, inaccurate and time consuming experimental methods. In the scope of this work, a generic and robust prediction method is built up for a centrifugal impeller PAT. The most significant hydraulic losses were derived in PAT mode, these are namely, the shock losses at the impeller inlet, the swirling losses at the impeller outlet and the impeller wall frictional losses. The Euler head, the available total head and the hydraulic efficiency were computed as well. The global efficiency was computed taking into account the machine mechanical and volumetric efficiencies, enabling therefore to perform comparison of the new prediction method with experimental, computational fluid dynamic (CFD), Rossi and Perez performances prediction methods. From where it resulted a good agreement between the given prediction methods for the entire range of operation, confirming the robustness and the applicability of the developed prediction method. The relative difference between the new prediction method and CFD data and between the new prediction method and experimental data remained higher for lower discharge conditions, notably for extreme part load conditions, where a small error could result in very high relative difference.

High-speed video recordings of slab burner experiments were analyzed using a machine learning approach with convolutional neural networks in order to compute the regression rate of hybrid rocket fuels over time. Combustion tests of paraffin-based fuel grains performed in two different hybrid rocket slab burners were recorded with high-speed video cameras and the resulting image data are analyzed in order to determine the height of the fuel in each frame. To this end, a deep neural network with U-net architecture is trained in a supervised fashion to segment the shape of the fuel slab. It is demonstrated that this approach is more capable to segment combustion images in unsteady flow conditions than classical computer vision methods based on thresholding or edge detection. Furthermore, methods in the area of uncertainty quantification of neural networks are applied to estimate the errors in the neural network prediction to new previously unseen data. Finally, the regression rate of the fuel is computed as the rate of change of this height. This method enables automatic analysis of a large amount of video data, taking full advantage of the optical access capabilities of slab burners. Additionally, the method delivers not only the time and space average values of the fuel regression rate, but also quantifies its variation over time and over the length of the slab, providing deeper insights into the combustion mechanics of hybrid rockets.

This paper investigates the separation efficiency of modern aeroengine air/oil breathers, focusing on identifying configurations that enhance existing geometries. The study systematically varies parameters such as air flow rates and rotational speed, using well-known particle size distributions for testing different configuration. The experimental campaign involves various breathers with metallic grids of different geometries and mesh sizes, evaluating performance parameters such as pressure drops, oil consumption, and droplet cut-off size. The insertion of a metallic grid with a narrow mesh is found to offer a favorable trade-off in terms of pressure drops, oil consumption, and particle size at the separator exit. Results indicate that while increasing pressure drops of a reasonable amount, the selected geometries significantly reduce oil consumption and size of droplet at the exit of the breather.

As the demand for hydrogen is expected to increase in the coming years, infrastructure requirements for the transport and storage of hydrogen should follow this trend to reduce its cost for users. For example, the European Hydrogen Backbone (EHB) represents a milestone toward a more accessible hydrogen network of pipelines. New compressors will be necessary to feed those pipelines, and for the volumes of hydrogen considered, only centrifugal compressors would be an adequate solution. But centrifugal compressors for hydrogen are a complex matter. Many technical issues are still under ongoing research, such as leakage through bearings and seals or materials problems due to hydrogen embrittlement. This work introduces a method to optimize the preliminary design of a centrifugal compressor for hydrogen applications. This optimization is based on the variation of geometrical parameters of the impeller to minimize the energy required to power the compressor. This optimization can be applied for a steady state operation or for an unsteady set of operation. Furthermore, this optimization process of a centrifugal compressor stage extends to the optimization of multiple stages compressors, but also for the optimization of the arrangement in series and/or in parallel. This method is then applied to different case studies of a possible compression station pre-design for a hydrogen pipeline application. The compression station is tested under steady state conditions for a pressure ratio of 1.2 and a mass flow rate of 2.8 kg/s. Then it is tested on a transient flow, with variations of the mass flow rate of up to 10 percent.

Ice accretion poses substantial safety hazards for the manned and unmanned aviation industries. Its study is essential for icing events risk assessment and for the development of efficient ice protection systems. The existing ice accretion measurement techniques-casting, molding, and laser-scanning-are time-consuming, sometimes cumbersome to use, and highly expensive, while hand tracing is inexpensive, but has lower accuracy and time-consuming post-processing. This work presents two low-cost, fast, and easy-to-use measurement techniques for 2D ice accretion profiles. Both employ algorithms of automatic ice shape detection, one based on unmediated image-processing, another based on the processing of manual ice tracings. The techniques are applied to ice accretion experiments conducted in an icing wind tunnel at low Reynolds numbers, and their results are validated against ice thickness caliper measurements. A comparison of the results shows that both techniques accurately measure the leading-edge ice thickness and the 2D shape of the ice accretion profiles. One technique is faster, with higher measurement accuracy, but produces interrupted-line 2D ice profiles and requires good lighting conditions, while the other generates continuous-line 2D profiles and has no application restriction, but it is slower, with lower accuracy. A discussion is conducted, aiming to help one determine the best applications for each ice accretion measurement technique presented.

The decrease in greenhouse gas emissions by passenger cars is one of the key factors for climate protection measures. Besides EU strategies for low-emission mobility, policy makers must consider the behavioural factors of buyers. This study aims to cover this gap by investigating the relation between the national cultural dimensions (Hofstede model) and car adoption by fuel type in EU countries. This could help car sellers to find better solutions for advertising cars with medium and low greenhouse gas emissions. To find better ways to increase the usage of medium- and low-emission cars using targeted advertising, correlations and a multiple regression analysis were used. The results show that the consumer preference for one type of fuel is correlated with at least one of Hofstede's six cultural dimensions: the power distance index; individualism versus collectivism; masculinity versus femininity; the uncertainty avoidance index; long-term orientation versus short-term normative orientation; indulgence versus restraint. The major conclusion of the study underlines that, with increases in the individualism versus collectivism and indulgence versus restraint scores, the usage of low- and medium-emission cars also increases, and with the increase in the power distance and uncertainty avoidance index, the usage of low- and medium emission cars decreases. At the same time, the driving preference for low- and medium-emission vehicles decreases with the tendency towards collectivism and restraint of EU countries.

This research explores the impact of the COVID-19 pandemic on consumer behavior and preferences related to household energy consumption through actions to fight climate change in Belgium, Romania, Italy, and Sweden. Using data from two Eurobarometer surveys conducted in 2019 and 2021, the study examines shifts in climate change perception, actions to combat climate change, and the influence of socio-economic and demographic variables on these actions. Depending on the country, the findings reveal significant pandemic-induced changes in public perceptions of climate change and personal actions to combat it. Age, gender, and education level were found to influence climate change actions. Financial constraints also significantly influenced the adoption of energy-efficient behaviors. Our research enriches existing knowledge by exploring the influence of the COVID-19 pandemic on climate change perceptions and actions across diverse European countries, shedding light on the interplay between global crises and sustainability. The research methodology, including chi-square tests, logistic regression, and effect size measurements, provides a robust framework for understanding how economic factors and consumer behaviors are contributing to the development of effective energy policies.

Energy imports and the transition to renewable energy sources are of critical importance in the current geopolitical context, which necessitates concrete actions to tackle the energy crisis at the European Union level. This study aimed to explore the impact of imported non-renewable energy resources on the EU-27 economy. It examined the correlations and causal relationships between the GDP, the GVA, R&D investments, and energy imports from 2000 to 2021. Data normality was assessed using the Shapiro–Wilk test, while Pearson’s test identified correlations between variables. Linear and multiple regression analyses were conducted to determine the effects of changes in independent variables on dependent variables. The study found a strong association between natural gas imports and the GDP, with increases in GDP leading to a more-than-fourfold rise in imports. Furthermore, a multiple regression analysis indicated that a 1% increase in R&D investments results in a 2.21% decrease in fossil fuel imports in 91.7% of cases. This suggests that R&D investments contribute to improved efficiency and the use of renewable energy sources.

While brush seals have been studied for almost forty years, carbon fibre brush seals have only recently drawn interest for their excellent leakage performance, combined with low friction. Their suitability for oil sealing applications has been acknowledged in the aeronautical field, specifically for civil aircraft gas turbine engines. This paper focuses on the endurance of optimally designed brush seals in an environment simulating the bearing chamber working conditions. They underwent a wide range of differential pressures and rotational speeds in long runs ranging from 100 to 300 h. A semi-empirical performance prediction model was developed based on these results, allowing estimation of the leakage performance beyond the recorded data. In addition, the presence of lubrication oil largely increases seal life, despite initial leakage performance degradation due to hydrodynamic lift. Finally, a visual inspection with a high precision microscope revealed uprooting of the carbon fibres. This phenomenon may well be the biggest cause of performance degradation, rather than fibre material losses, which were ultimately deemed unquantifiable.