Antarctic research stations have historically relied on diesel-based generators, where the fuel is provided through a single annual delivery and whose combustion burdens one of the most sensitive ecosystems of the planet. The Mario Zucchelli Station (MZS), the Italian PNRA base, departs from the diesel-only paradigm. It operates a hybrid microgrid, joining photovoltaics, wind, battery storage, and a four-unit diesel plant, but a structured energy transition to 2035 must be outlined. This work provides the quantitative techno-economic and environmental counterpart to this roadmap. A modular, physically-based, in-house model resolves the station microgrid on an hourly basis over a full year, forced by measured meteorological data provided by real weather stations. Since the existing hybrid microgrid is taken as the reference case, the analysis performed in this work quantifies the incremental decarbonization of a partially-renewable system. Levelized costs, unserved energy, and avoided CO2 are treated as equal weight objectives, while an electrified vehicle fleet is added as a seasonal load. Over nine different transition scenarios, the lifecycle cost appears to be dominated by diesel fuel (for about 80%), highlighting the great advantage of a renewable solution. The decarbonization proves to be generation-led rather than storage-led, and photovoltaics emerges as the most cost-effective single increment at this coastal site, in contrast with the wind-dominated optima reported for inland Antarctic stations. The recommended pathway ranges from a robust rationalization of backup processes to a balanced configuration (LCOE 2.61 €/kWh, 20% CO2 cut) and a maximal decarbonization (38.8% CO2 cut, 8.1 M€ lifecycle saving).

The use of machine learning in marine engine optimization, control, and predictive maintenance has become increasingly valuable under variable environmental conditions. Predictive maintenance, supported by anomaly detection algorithms, enables early identification of potential failures and can reduce downtime and costs in practice. Environmental conditions strongly influence marine engine performance, yet this aspect is rarely addressed in the literature. This study investigates the association between ambient temperature and engine behavior using two artificial neural network (ANN) models trained on experimental data from a large-bore single-cylinder marine diesel engine. The experiments covered ambient temperature spanning 5-45 degrees C under non-climate-controlled, field-like conditions. The models were trained and evaluated with a 50%/25%/25% split at the sample (crank-angle) level, focusing on identifying temperature-associated patterns within the observed operating domain rather than extrapolating to unseen operating or thermal conditions. The first model (pressurebased) employs in-cylinder pressure signals; the second (accelerometer-based) uses a scalar magnitude from triaxial accelerometers with minimal preprocessing (approximate to 10 degrees CA moving average) as a low-cost alternative. Both models retrieve a slight decrease in delivered fuel flow at fixed injection commands as temperature increases, in line with the literature on the temperature dependence of fuel viscosity/atomization and injection hydraulics. The accelerometer-based ANN captures this trend with lower precision, requiring more conservative alert thresholds in practice. The pressure-based ANN also allows for testing other temperature-related trends, such as ignition timing advance at higher temperatures, consistent with expected combustion behavior.

Reducing the non-exhaust particle emissions has become the new challenge to pursue a more sustainable transport system. Understanding the characteristics of brake wear particles and the factors affecting their formation is essential for developing effective control measures.This study reports an experimental investigation on the particles emitted from a brake for automotive. A finite-difference thermal model of the disc and the pads was built on purpose starting from the experimental configuration. It was tuned and validated with the measurements performed at the test bench and then used to evaluate the brake thermal status under new testing cases. Experimental results demonstrated that the braking profiles strongly influence the particle number and size. At the same profile, the temperature plays a significant role on particle emissions as well. The model showed good potential in the prediction of the brake disc temperature and provided a simplified bi-dimensional distribution of the disc temperature.

This editorial piece emphasizes the importance of low-carbon, synthetic electro-fuels (e-fuels) in decarbonizing transport, which complements other decarbonization measures, including efficiency improvements, vehicle electrification and hybridization, as well as bio-based renewable fuels. Given the stringency of the emissions legislations worldwide, and the desire for many countries to achieve net-zero CO 2 emissions by 2050, synthetic electro-fuels, produced using renewable electricity, water and captured CO 2 , has the potential to deliver significant CO 2 reductions. When e-fuels are designed to be chemically similar to conventional fuels, they can be compatible with existing vehicles and infrastructure. Therefore, e-fuels can be a drop-in solution to facilitate an accelerated decarbonization of the existing legacy fleet as well as next generation IC engines. Furthermore, e-fuels could unlock greater penetration of renewable electricity into the transport sector by enabling international trade of renewable electricity in the form of liquid energy carriers. This is particularly useful for matching lower cost renewable electricity producers from regions with high solar irradiation and wind potential, with existing and growing energy demand centers globally that have limited renewable electricity generation potentials. The paper highlights the potential of several e-fuels: hydrogen, ammonia, e-gasoline, alcohols, DMC, paraffinic fuels, OMEx (DME), and their use in internal combustion engines, considering both spark-ignition and compression-ignition combustion, with an insight on dual-fuel and reactivity-controlled CI combustion modes. Advantages in terms of combustion efficiency and pollutant emissions are also comprehensively discussed, together with the challenges related to their use and production. Finally, the paper remarks the importance of Life-Cycle-Assessment (LCA) to assess the climate change mitigation potential of alternative fuels and powertrains. LCA studies reveal that there is no silver-bullet to decarbonizing transport, neither fuels nor powertrain technologies, since the CO 2 reduction potential of these technologies is highly dependent on how they are produced and operated throughout their entire life cycles.

Due to their reliability, high-performance characteristics, and potential for technological innovation, combustion engines powered by alternative fuels such as hydrogen can still represent a useful solution for achieving mobility with net zero emissions. The use of hydrogen in a dual-fuel engine with diesel (or other renewable and sustainable fuels) can reduce greenhouse gas emissions as well as particulate matter emissions while ensuring excellent performance. In this scenario, tests have been carried out on a dual-fuel single-cylinder research engine to analyse the combustion evolution of H2 in ultra-lean conditions via optical diagnostics. Under ultra-lean conditions (lambda = 3.8), hydrogen does not autoignite at the desired crank angle; thus, diesel has been used to ignite the hydrogen premixed charge. An operating point at 1500 rpm engine speed and at fixed load has been investigated. The in-cylinder pressure and related data have been analysed as indicators of combustion quality. 2D-digital cycle-resolved imaging has been performed in both ultraviolet (UV) and infrared (IR) wavelength ranges. Qualitative information about the development of diesel hydrogen dual fuel combustion has been gained. UV and IR cameras simultaneously acquired images of the diesel and hydrogen combustion and provided information on the flame onset and its development via the detection of OH* and low-and high-temperature reaction zones within the bowl, respectively. Results show that to efficiently control hydrogen combustion, it is necessary to properly phase the start of diesel combustion.

Small size engines feature several peculiarities that render them a challenge with respect to implementing measurements required for characterizing specific phenomena such as combustion evolution. Measuring in-cylinder pressure is well established as standard procedure for determining combustion characteristics, but in the case of small size units actually applying it can require alternative approaches. Fitting a crank angle encoder may be extremely difficult, as a consequence of the actual size of the power unit. Cost is another essential driver for small engine development that also influences how measurements are implemented. Within this context, the present work describes the development and implementation of a method that employs an algorithm that practically generates a ‘virtual’ encoder. Only a basic phasing signal is required, such as an inductive crankshaft position sensor output or that of an ignition pulser. The software was developed on an experimental engine with a crank angle encoder, that provided the reference case. Several configurations were under scrutiny, so as to identify the minimum requirements able to fulfill the intended task. Afterwards, it was tested for achieving crank angle resolution in-cylinder pressure measurements by applying time based data acquisition on up to 8 high speed channels (with a maximum sampling rate equivalent to 0.5 crank angle resolution at 6000 rpm). Measurements showed that the proposed method successfully fulfilled both requirements, i.e. high accuracy and cost effective data acquisition on two small size engines (one single cylinder 50 cc and the other 3 inline cylinders 600 cc). Simulations performed using the 0D/1D approach also confirmed the validity of the results. The only major drawback that was identified at this stage is that the proposed method requires the acquisition of data on one or two additional channels (for crank shaft position/ignition pulser signals) for ensuring correct implementation. Nonetheless, the benefits can be considered as more than sufficient for minimizing the effects of this shortcoming.

The present article offers a detailed analysis of helium jet velocity and vorticity intensity distribution using the particle image velocimetry (PIV) technique. A gaseous fuel injector featuring an interchangeable tip was implemented. The test campaign involved the use of three nozzle patterns characterized by different orifices shape and orientations. The helium was injected into a constant volume chamber (CVC) and the delivery pressure varied, as well as that inside the chamber, in order to obtain pressure ratios (PRs) ranging from 2 to 20. The synchronization system was set to record two consecutive frames at different time-instants after the start of energizing (aSOE). Green light from a dual cavity Nd:YAG laser was used for illumination and a 4-megapixel PIV-camera for image capture. Vegetable oil particles were seeded into the chamber to trace the helium jet structure and cross-correlation methodology employed to measure their instantaneous displacements. The role of orifices size and orientations has been deeply scrutinized and related to the morphological outcomes. The least-oriented nozzle (first) exhibited the highest values of jet penetration and well-defined vortex structures. In contrast, the more the orifices are oriented, the wider the regions interacting with surrounding environment. Specifically, geometry with smaller orifice sizes (third) returned an overall absence of localized significant vortex structures. This deficiency is counterbalanced by a large distribution of small vortices that were observed to replace the main rings for each condition examined.

Energy and mobility are currently powered by conventional fuels, and for the specific case of spark ignition (SI) engines, gasoline is dominant. Converting these power-units to hydrogen is an efficient and cost-effective choice for achieving zero-carbon emissions. The use of this alternative fuel can be combined with a circular-economy approach that gives new life to the existing fleet of engines and minimizes the need for added components. In this context, the current work scrutinizes specific aspects of converting a small-size passenger car to hydrogen fueling. The approach combined measurements performed with gasoline and predictive 0D/1D models for correctly including fuel chemistry effects; the experimental data were used for calibration purposes. One particular aspect of H2 is that it results in lower volumetric efficiency compared to gasoline, and therefore boosting requirements can feature significant changes. The results of the 0D/1D simulations show that one of the main conclusions is that only stoichiometric operation would ensure the reference peak power level; lean fueling featured relative air–fuel ratios too low for ensuring the minimum value of 2 that would allow mitigating NOx formation. Top speed could be instead feasible in lean conditions, with the same gearbox, but with an extension of the engine speed operating range to 7000 rpm compared to the 3700 rpm reference point with gasoline.

The utilization of hydrogen in low-temperature Proton Exchange Membrane Fuel Cells (PEMFCs) stands out as a compelling prospect for driving a widespread shift towards green industry practices. Despite significant advancements, a comprehensive understanding of water behaviour and dynamics within PEMFCs remains crucial for their extensive integration in propulsion applications. Striking a delicate balance between flooding and drying conditions poses a challenge for achieving stable and efficient PEMFC operation. In this study, a preliminary experimental investigation was conducted focusing on carbon-paper Gas Diffusion Layer (GDL) and gas channel walls. The static, advancing and receding contact angles were measured and utilized as boundary conditions for simulations. The influence of membrane humidity was also examined during the experimental campaign. 3D CFD simulations were performed on a straight portion of a PEMFC channel with a selected domain length of 5 mm and a section of 1x1 mm. Two classes of droplets (0.05 mm3 and 0.075 mm3) were deposited in the middle of the channel and in double contact conditions between the GDL and the wall. To account for the significant difference in contact angles, the relative boundary condition for the GDL was set equal to the experimental static angle (128°), while a User Defined Function (UDF) for dynamic contact angle was implemented based on observed contact angle hysteresis (45° / 55°) and literature correlations. The droplet behaviour was studied under constant 10 m/s inlet velocity and atmospheric pressure outlet. The research results contribute valuable insights into water management within gas channels. The mixing contact angle condition highlighted the differences in motion behaviour on the two surfaces: droplets tend to roll on the GDL, while the high wettability of the walls leads to slug/film formation.

This paper focuses on the optimal sizing and management of a hybrid energy storage system for an electric public transportation bus. In this study, the energy flows between the battery pack and the supercapacitor module are managed by employing a strategy, based on the exponentially weighted moving average of the current required by the electric drive. In addition, a multi-objective optimization approach is proposed to define the size of the supercapacitor module and the decay factor of the management strategy, with the pursued objective to enhance the battery pack service life and simultaneously improve the energy utilization of the high-power module. Then, an appropriate power architecture and a PWM control strategy for the DC/DC converter are selected, on the base of the resulting energy flows. In this way, the proposed hybrid storage system, in terms of performance in a real-world operating scenario, is compared with an equivalent battery electric bus. In the end, the results on the hybrid storage system demonstrate a significant reduction in both battery peak power demand and C-rate, contributing to an extended battery lifespan.

Water removal from Proton Exchange Membrane (PEM) Fuel Cell (FC) mainly involves two phenomena: some of the emerging droplets will roll on the Gas Diffusion Layer (GDL), others may impact channel walls and start sliding along the airflow direction. This different behaviour is linked to the hydrophobic/hydrophilic nature of the surface the water is moving on. In this paper, the walls of the channel of a FC were characterized by applying optical techniques. The deposition of droplets on the channel wall led to an evaluation of the proper range for Contact Angle Hysteresis (CAH = 55° - 45°), and due to the high wettability of the surface, droplets dimension was defined with a dimensionless parameter B/H. Under high crossflow condition (15 m/s) a sliding behaviour was observed. The channel features determined through image processing were used as boundary conditions for a 2D CFD two phase simulation employing the Volume of Fluid (VOF) model to keep track of the fluids interface. A droplet was initialized on the wall and its behaviour was observed under 15 m/s airflow. Starting from the values observed experimentally, three different contact angle strategies were adopted to manage the liquid-solid-gas interface: static contact angle, quasi-dynamic contact angle and dynamic contact angle. The calculated sliding velocity was validated against experimental data. The static contact angle led to an overestimation of water removal capability. The quasi-static approach improved the accuracy of the simulation, but only the dynamic contact angle consistently falls inside the error bars of experimental measurements. Moreover, bigger droplets show higher sensitivity to contact angle boundary conditions.

<div class="section abstract"><div class="htmlview paragraph">In the perspective of a reduction of emissions and a rapid decarbonisation, especially for compression ignition engines, hydrogen plays a decisive role. The dual fuel technology is perfectly suited to the use of hydrogen, a fuel characterized by great energy potential. In fact, replacing, at the same energy content, the fossil fuel with a totally carbon free one, a significant reduction of the greenhouse gases, like carbon dioxide and total hydrocarbon, as well as of the particulate matter can be obtained. The dual fuel with indirect injection of gaseous fuel in the intake manifold, involves the problem of hydrogen autoignition. In order to avoid this difficulty, the optimal conditions for the injection of the incoming mixture into the cylinder were experimentally investigated. All combustion processes are carried out on a research engine with optical access. The engine speed has is set at 1500 rpm, while the EGR valve is deactivated. The purpose of this work is to research the minimum amount of diesel fuel, which allows efficient and controlled hydrogen ignition. Starting from the dual fuel conditions investigated in previous works with two injections per cycle, one of the diesel injections was removed. Subsequently, the shift of the start of injection and the reduction of the energizing time of the diesel injection as well as the increase in the delivered mass of hydrogen are analysed. The final aim is to obtain an indicated mean effective pressure equal to the one previously analysed avoiding backfiring phenomena in the manifolds or abnormal engine operation. All the analysed tests are in ultra lean combustion conditions with premixed ratio higher than 95% and equivalence ratio higher than 0.32. From the investigated cases, it can be found that the best combustion efficiency is determined with a diesel start of injection around 10 before top dead centre, while the lowest amount of diesel corresponds to an energizing time of the injector equal to 209μs. Regarding the hydrogen injection in the intake manifold, a dependency on the intake valve timing is highlighted. Hydrogen was prevented from being thrown into the exhaust by starting its supply after the valve crossing; on the other hand, to avoid backfiring phenomena, it is noted that the hydrogen injection has to end prior to the compression phase commences. This information is of particular interest to fulfil engine decarbonisation optimizing the use of hydrogen in compression ignition engines and facilitating CFD analysis of hydrogen combustion in ultra lean conditions.</div></div>

This study explores the potentiality of low/zero carbon fuels such as methanol, methane and hydrogen for motor applications to pursue the goal of energy security and environmental sustainability. An experimental investigation was performed on a spark ignition engine equipped with both a port fuel and a direct injection system. Liquid fuels were injected into the intake manifold to benefit from a homogeneous charge formation. Gaseous fuels were injected in direct mode to enhance the efficiency and prevent abnormal combustion. Tests were realized at a fixed indicated mean effective pressure and at three different engine speeds. The experimental results highlighted the reduction of CO and CO2 emissions for the alternative fuels to an extent depending on their properties. Methanol exhibited high THC and low NOx emissions compared to gasoline. Methane and, even more so, hydrogen, allowed for a reduction in THC emissions. With regard to the impact of gaseous fuels on the NOx emissions, this was strongly related to the operating conditions. A surprising result concerns the particle emissions that were affected not only by the fuel characteristics and the engine test point but also by the lubricating oil. The oil contribution was particularly evident for hydrogen fuel, which showed high particle emissions, although they did not contain carbon atoms.

The need to cope with carbon dioxide abatement has prompted the development of innovative technologies for sustainable mobility. Meanwhile, these technologies consolidate, an important role will be played by internal combustion engines fed with non-fossil fuels such as hydrogen. Theoretically, the combustion of hydrogen should not produce carbon-based emissions. Nevertheless, particles can be found in the exhaust of hydrogen-fueled engines because of the lubricating oil. In this study, a thorough examination of the impact of the engine lubricant on the mechanisms leading to the formation of the particles and the high levels of hazardous pollutants was performed in this study. Experiments were carried out on a direct injection spark ignition engine fueled with hydrogen. The analysis was conducted at 2000 and 3000 rpm both low and full load. Number and size particle distribution were determined by means of on-line measurement on the diluted exhaust. Off-line chemical characterization through analytic techniques was realized on the condensed exhaust and on the particles collected on a filter. Experimental results pointed out that the extent of the particle size varies according to the engine speed and load, evidencing the different role of the oil ascribable to the environmental conditions. It was found that aromatic molecules and nanoparticles are present in the exhausts at all the investigated operating conditions, whereas soot aggregates are formed only at high engine speed.(c) 2023 The Author(s). Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC.This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/).

In a context of growing concern for vehicle-related CO2 and pollutant emissions, non-conventional fuels like methanol (CH3OH) represent a valid alternative to fossil fuels to decarbonize the transport sector in a reasonable time. This is mainly due to its lower carbon content than conventional gasoline and diesel. Moreover, methanol can be obtained either from biomass or CO2 capture from the atmosphere, which makes the latter a renewable fuel. Given the possibility of being stored in liquid phase at standard temperature and pressure (STP), methanol is very suitable for Light Duty Vehicles (LDVs), in which the need to contain fuel tank dimensions is relevant. Regarding the deployment of methanol as a fuel, it is not very challenging, as it can be adopted in current production Internal Combustion Engines (ICEs) either in pure form or in blend with other fuels without any significant modifications. Within this context, the present work aims to assess, in both experimental and simulation environments, the benefits of pure methanol fueling of Spark Ignition (SI) engines. Particularly, a small single-cylinder production SI engine has been tested on the engine test bench at different speeds and air-fuel ratios, at unthrottled conditions. Besides the test campaign, a 1-D model of the engine under study has been developed, with a particular focus on the simulation of methanol combustion. Particularly, different correlations for the laminar flame speed, implemented in the combustion model, have been investigated to evaluate their effect on the prediction of performance, efficiency, and pollutant emissions. Combustion, heat transfer, and pollutant emissions sub-models have been tuned and validated based on the experimental data. Both experimental measurements and simulation results evidence that methanol fueling allows for improving engine efficiency, while reducing regulated pollutant emissions from a current production SI engine, if compared to conventional gasoline, especially under lean-burn operating conditions. This work is useful for future activities, which will concern the optimization of the Ignition Timing (IT), as well as the investigation of the knock tendency of methanol-fueled SI engines.

Vehicular emissions represent the main responsible of the deterioration of air quality in the urban area. In the attempt to reduce both gaseous emissions and particulates from internal combustion engines, increasingly stricter regulations were introduced from European Union in the last years. These limits have led to the improvement of emissions-reduction technologies as well as the vehicle hybridization and electrification. In this scenario, vehicle emissions due to other sources rather than the propulsion systems, such as brakes and tires, have taken a significant weight. In this regard, European Commission has proposed the introduction in the next EURO 7 standard of the first-ever limit on the particles emitted by vehicle brakes. This study is devoted to improving the knowledge on the particle characteristics due to the brake wear by means of laboratory experiments thus providing support to the definition of the new standards. An experimental layout was realized consisting in a box where a brake for light duty applications was enclosed. Particles were measured in the size range from 5.6-560 nm and 0.3-10 μm through an EEPS and an OPS, respectively. A section of the standardized cycle for brake emissions and a properly realized profile characterized by intense braking were tested. The impact of the inlet air flow on the measure of the particles was also discussed. The experimental results highlighted the role of braking profiles on the physical characteristics, number and size, of the particle emissions. Low concentration and large diameter particles were emitted under urban driving conditions. On the other hand, hard braking increased the number of particles especially in the small size range.

Battery Thermal Management systems are a key component for modern electric vehicles. Many systems use advanced models for temperature prediction and for the optimal cooling or heating strategies. Thermo-electric characterizations of cells and battery packs are performed inside the research labs to properly tune the models before uploading them to the on-board control units. However, these data depict the storage system under brand new conditions. Throughout the vehicle life, the battery pack behavior can change because of several factors related to the surrounding environment and operating conditions. Moreover, in the case of battery swap strategies, that consist in the pack replacement, the temperature model would be totally unsuitable for the new installed one. Therefore, an on-board, online procedure for the evaluation and update of the battery thermal behavior could be needed. This work presents a method for the evaluation of the battery thermal parameters on-board, during real driving cycles using data that are available in the vehicle control unit. The main novelty of this work consists in the solution to combine and assist the temperature model in the vehicle control units with an optimization algorithm which does not increase the computational load and provides reliable thermal parameters estimations. To demonstrate the potential of this methodology, the evaluated parameters are used in a short-term temperature model suitable for control strategies for battery thermal management systems. Concerning the first part, an optimization procedure is run for different driving cycles, recorded using a GPS system on a real vehicle. Finite-difference method is used to identify the convective heat transfer coefficient and the specific heat capacity of a single cell that composes the battery pack in laboratory tests. Then, the reliability of the estimated thermal parameters is analyzed reducing the number of source records and using the remaining cycles for the validation. Four worst cases have been identified and used to check the performance of the model prediction. Considering a temperature measure tolerance of 6 %, up to 93.75 % of the estimated values is reliable. Finally, the thermal parameters are used in a short-term temperature model for control strategies. The results highlight the good performance of the model in the estimation of the on-board battery temperature during a real driving cycle, simulating the future heat generation on the basis of the current load demand of the previous time step. The temperature predictions of the short-term model have been also tested in the worst cases denoting a good reliability; the maximum error is + 5 % in overestimation and 3 % in underestimation. Temperature predictions would help in the feed-forward control of battery thermal management systems for a smooth and safe operation of future electric vehicles. Moreover, this solution can be adopted for even more complex cooling methods, enhancing the update of the battery pack characteristics also in case of deterioration or battery swap.

Hydrogen is seen as a prime choice for complete replacement of gasoline so as to achieve zero-emissions energy and mobility. Combining the use of this alternative fuel with a circular economy approach for giving new life to the existing fleet of passenger cars ensures further benefits in terms of cost competitiveness. Transforming spark ignition (SI) engines to H2 power requires relatively minor changes and limited added components. Within this framework, the conversion of a small-size passenger car to hydrogen fueling was evaluated based on 0D/1D simulation. One of the methods to improve efficiency is to apply exhaust gas recirculation (EGR), which also lowers NOx emissions. Therefore, the previous version of the quasi-dimensional model was modified to include EGR and its effects on combustion. A dedicated laminar flame speed model was implemented for the specific properties of hydrogen, and a purpose-built sub-routine was implemented to correctly model the effects of residual gas at the start of combustion. Simulations were performed in several operating points representative of urban and highway driving. One of the main conclusions was that high-pressure recirculation was severely limited by the minimum flow requirements of the compressor. Low-pressure EGR ensured wider applicability and significant improvement of efficiency, especially during partial-load operation specific to urban use. Another benefit of recirculation was that pressure rise rates were predicted to be more contained and closer to the values expected for gasoline fueling. This was possible due to the high tolerance of H2 to the presence of residual gas.

Recirculation of the unconsumed anodic gas present in the exhaust stream of Proton Exchange Membrane Fuel Cells (PEMFC) represents a solution frequently used for improving the utilization efficiency of hydrogen. The design of an anodic recirculation system (ARS) can include an ejector that carries the recuperated hydrogen stream directly into the fuel supply line. Compared to pumps, ejectors have no moving parts and do not require power to work, thus increasing the overall efficiency of the cell. On the other hand, they are sensitive to load changes and need an attentive design process. Nozzle diameter and position, convergent and divergent angle, the ratio between nozzle and mixing chamber diameters are several parameters that are usually optimized by trial and error. In this work the development and validation of a 3D CFD model for an ejector to be used on a 5000 W PEMFC was performed. In addition, three new geometries of ejectors to be coupled with 3000 W, 1000 W and 300 W fuel cells were designed. Finally, the scalability and convenience of an ejector for different static power requests were assessed.

Shipping is one of the most efficient transportation modes for moving freight globally. International regulations concerning decarbonization and emission reduction goals drive rapid innovations to meet the 2030 and 2050 greenhouse gas reduction targets. The internal combustion engines used for marine vessels are among the most efficient energy conversion systems. Internal combustion engines dominate the propulsion system architectures for marine shipping, and current marine engines will continue to serve for several decades. However, to meet the aggressive goals of low-carbon-intensity shipping, there is an impetus for further efficiency improvement and achieving net zero greenhouse gas emissions. These factors drive the advancements in engine technologies, low-carbon fuels and fueling infrastructure, and emissions control systems. This editorial presents a perspective on the future of ship engines and the role of low-life cycle-carbon-fuels in decarbonizing the marine shipping sector. A selection of zero-carbon, net-zero carbon, and low-lifecycle-carbon-fuels are reviewed. This work focuses on the opportunities and challenges of displacing distillate fossil fuels for decarbonizing marine shipping. Enabling technologies such as next-generation air handling, fuel injection systems, and advanced combustion modes are discussed in the context of their role in the future of low-CO2 intensity shipping.