This study investigates the thermochemical energy recovery during butanol exhaust-gas-assisted fuel reforming in gasoline direct injection (GDI) engines. The production of hydrogen (H2) through catalytic reforming was studied in a full-scale reactor loaded with rhodium (Rh)-platinum (Pt) catalysts and integrated within the engine exhaust. Thermodynamic equilibrium analyses are conducted via ANSYS-CHEMKIN based on Gibbs energy minimisation. Both experimental and numerical studies revealed that butanol (in this case, blended in gasoline- B33%) promotes endothermic reactions in the reforming reactor, yielding higher H2 production with improved heat recovery by up to 11% compared to gasoline. Theoretical calculations of using the reformed gas in the engine for combustion as reformed exhaust gas recirculation (REGR) predicted fuel savings and a nearly 8% reduction in CO2. The work underlines the advantages of butanol reforming in enhancing fuel economy and reducing emissions in GDI engines and highlights the importance of the fuel properties in overall system efficiency.

The use of hydrogen in internal combustion engines is a promising solution for the decarbonisation of the transport sector. The current transition scenario is marked by the unavailability and storage challenges of hydrogen. Dual fuel combustion of hydrogen and gasoline in current spark ignition engines is a feasible solution in the short and medium term as it can improve engine efficiency, reduce pollutant emissions and contribute significantly in tank to wheel decarbonisation without major engine modification. However, new research is needed to understand how the incorporation of hydrogen affects existing engines to effectively implement gasoline-hydrogen dual fuel option. Understanding the impact of hydrogen on the combustion process (e.g. combustion speed) will guide and optimize the operation of engines under dual fuel combustion conditions. In this work, a commercial gasoline direct injection engine has been modified to operate with gasolinehydrogen fuels. The experiments have been carried out at various air-fuel ratios ranging from stoichiometric to lean combustion conditions at constant engine speed and torque. At each one of the 14 experimental points, 200-cycle in-cylinder pressure traces were recorded and processed with a quasi-dimensional diagnostic model and a combustion speed analysis was then carried out. It has been understood that hydrogen mainly reduces the duration of the first combustion phase. Hydrogen also enables to increase air excess ratios (lean in fuel combustion) without significantly increasing combustion duration. Furthermore, a correlation is proposed to predict combustion speed as a function of the fuel and air mixture properties. This correlation can be incorporated to calculate combustion duration in predictive models of engines operating under different fuel mixtures and different geometries of the combustion chamber with pent-roof cylinder head and flat piston head.

Direction Injection Dual-Fuel (DIDF) engines fueled with ammonia and diesel are identified as a promising solution for decarbonizing large-scale Compression Ignition (CI) engines. This study addresses the research gap of missing a parametric model for simulating the combustion process in DIDF CI engines using ammonia and diesel. Multi-objective optimization and genetic algorithms are applied to generate a parametric Multi-Wiebe Combustion (MWC) model based on experimental results from a NH3-diesel DIDF CI engine. The innovative approach supports one-dimensional engine modeling with NH3-diesel combustion in GT-Power, enhancing the understanding of direct injection timings, fuel interactions, and combustion dynamics. Key findings include the impact of dual-fuel injection timings and fuel ratios on ignition delay, individual combustion phase durations, and heat release rate, providing a quantitative description of combustion behavior under varying conditions. The validation results show that with injection timing variations from -17.5 to -10 CAD aTDC and NH3 energy ratios ranging from 40 % to 60 %, relative errors remain below 5 % for key performance indicators such as pressure and efficiency. This study proposes a methodology to generate an accurate combustion model - the MWC model - for one-dimensional dual-fuel engine simulation, aiding in calibrating scaled-up DIDF CI engines and guiding further engine designs.

The discretization modeling methodology is proposed for dynamic analysis of Hybrid Wave-Tidal Energy Converters (HWTEC). By integrating the Pseudo Real-Time Wave (PRTW) simulation method based on random wave theory, it effectively reflects the actual random ocean waves characteristics and addresses the nonlinear response, without relying on continuous inputs. The discretization modeling method precisely determines and calculates the nonlinear dynamic response during the overrunning phase, enabling direct numerical solutions for nonlinear input and output parameters in the time domain, and eliminating the need for complex manual judgments. Validation through re-simulation of previous work shows an acceptable error of approximately 5 % in input and 0.5 % in output, demonstrating reliability. The proposed hybrid wave-tidal energy converter, based on the Non-Linear Motions Rectification and Coupling Device (NLMRCD), converts reciprocating wave motion into one-way motion and couples it with tidal rotation to enhance power output. It leverages the complementary and asynchronous distribution of wave and tidal energies, resulting in more stable output. Simulations reveal the impact of key parameters on output power and efficiency, achieving an average output power of 206.2 W and an efficiency of 40.8 %. The overrunning phase increases output power by 54.0 %, significantly enhancing output stability.

As hydrogen (H2) gains attention as a clean alternative to conventional fuels, understanding its effect on engine processes becomes necessary. This is especially challenging in dual-fuel applications combining H2 and carbon- based fuels so that flexibility in combustion can be extended to emissions control. In this study, the real-driving conversion efficiency of CO and HC in Pt and Pt/Pd oxidation catalysts is investigated in the presence of H2 applying an experimental-computational approach. The analysis of the experimental data drives to propose a reaction mechanism that accounts for alternative pathways for CO and HC oxidation when H2 is present. This mechanism is then implemented in a one-dimensional model for dual-layer washcoat honeycomb catalytic converters. Firstly, the model is calibrated against experimental temperature-ramp tests to assess the sensitivity of CO and HC light-off temperature and selectivity to O2 and H2 depending on the catalytic formulation. Then, the H2 effects on the conversion efficiency are analysed under real driving conditions considering a wide range of H2 content. Finally, the changes in the catalyst response and the differences between Pt and Pt/Pd samples as a function of a variety of simple post-injection strategies are discussed in terms of cumulative conversion efficiency benefits against H2 consumption.

All diesel-only trains in the UK will be phased out by 2040. Hydrogen and ammonia emerge as alternative zero-carbon fuel for greener railway. Solid Oxide Fuel Cells (SOFCs) provide an alternative prime mover option, which efficiently convert zero-carbon fuels into electricity without emitting nitrogen oxides (NOx), unlike traditional engines. Superior to Proton Exchange Membrane Fuel Cells (PEMFCs) in efficiency, SOFCs fulfil MW-scale power needs and can use ammonia directly. This study investigates innovative strategies for integrating SOFCs into hybrid rail powertrains using hydrogen or ammonia. Utilizing an optimization framework incorporating Particle Swarm Optimization (PSO), the study aims to minimize operational costs while considering capital and replacement expenditures, powertrain performance, and component sizing. The findings suggest that hybrid powertrains based on ammonia-fueled SOFCs may potentially reduce costs by 30% compared to their hydrogen counterparts, albeit requiring additional space for engine compartments. Ammonia-fueled SOFCs trains also exhibit a 5% higher efficiency at End-of-Life (EoL), showing less performance degradation than those powered by hydrogen. The State of Charge (SoC) of the batteries in range of 30–70% for both cases is identified as most cost-effective.

The combustion of hydrogen (H2) as a fuel is attractive due to its zero-carbon nature and combustion-enhancing properties when used to supplement other fuels. However, the challenge of using H2 as a fuel for transportation applications is the difficulty of onboard storage. One solution to this is to crack onboard stored ammonia (NH3) into H2 which can be supplied to the combustion chamber. However, the reforming process is not always 100 % efficient which can lead to the presence of NH3 in the combustion process. The presence of NH3 can influence engine performance, combustion and emissions. Therefore, this experimental study reports the differences in engine performance between H2 and NH3 reformate mixtures (H2/NH3/N2) added to gasoline in a dual-fuel engine setup under both stoichiometric (λ=1.0) and lean-burn (λ>1.0) operating conditions in a spark ignition (SI) engine. In this study, gasoline was used as the main fuel, with the H2 and NH3 reformate blends studied having energy substitution ratios ranging from 0% to 23%. The results showed that the use of H2 and NH3/H2/N2 mixtures reduced carbon-based emissions. However, there was an increase in nitrogen-based emissions compared to gasoline with increased H2 and NH3 content.

This experimental study investigates the palladium/ rhodium based three-way catalyst (TWC) in a hydrogen-gasoline dual-fuel spark ignition (SI) engine under stoichiometric and lean conditions. The work focused on lean-burn engine operating conditions with the aim of reducing nitrogen oxides (NOx) emissions during the combustion process, where the TWC is not effective, while improving the thermal efficiency of the engine. Under these lean- burn engine conditions, the combustion promoting properties of hydrogen allowed for maintained engine combustion stability as determined by the cycle-to-cycle variation (COVimep) imep ) values even up to ultra lean conditions (lambda= lambda= 2.0). It was found that by reducing the combustion temperature through the application of lean conditions, engine-out NOx emissions could be reduced or even eliminated, while under these conditions the TWC was effective in reducing engine-out carbon-based gaseous emissions.

The Joule cycle Linear Engine Generator (LEG) is a promising power generation technology with the potential to achieve zero carbon emissions. However, the LEG expander valve actuation system presents unique challenges due to its lack of a traditional crankshaft, the need for swift valve lift and reversal, and variable lift. This paper presents a Linear Variable Valve Actuation (LVVA) system for a LEG prototype. The LVVA system is powered by voice coil motors. Rigorous experimental investigations were conducted to analyze crucial performance factors, including energy consumption, force balance, energy flow distribution, and the relationship between valve lift duration and energy consumption. The results show that the LVVA system can achieve the desired valve lift and timing, as well as very small variations in LEG performance compared to the model using an ideal lift curve. The LVVA accounts for approximately 3.59 % of the LEG power output. The energy consumption of 1.607 J per valve stroke provides a slight advantage over traditional actuation systems. The obtained optimal lift curves were used to refine the LEG model. The influence of valve lift curves on LEG performance was evaluated which reveals rapid valve openings and relatively short duration contributing to improved LEG performance.

Addressing climate change demands, energy security and resilience has necessitated replacing conventional fossil-based fuels with zero and carbon-neutral fuels/energy carriers. The most immediate solution is the partial and progressive substitution of conventional fuels in transportation. The effects of partially substituting gasoline with ammonia/hydrogen (NH3/H2) mixtures in a spark ignition (SI) engine are investigated in this paper. The utilization of NH3/H2 mixtures is a promising avenue of research since they can be produced from on-board NH3 reforming, utilising heat energy that is recovered from hot exhaust gases. Experimental results indicate that adding NH3/H2 enabled stable engine operation at lean conditions (lambda = 1.4), resulting in reduced carbon-based emissions due to the non-carbon nature of NH3/H2. Utilising an integrated approach that combined a hemispherical flame geometry model with a thermodynamic model, has revealed that the introduction of NH3/H2 significantly enhanced the combustion speed during the initial phase and further improved combustion efficiency. However, nitrogen-based emissions such as NO and NO2 increased. This work also assessed the performance of a conventional three-way catalyst (TWC) and a double-function ammonia slip catalyst (ASC) in mitigating emissions. The TWC effectively controlled carbon-based emissions and NO under stoichiometric conditions but exhibited reduced efficiency under lean conditions, especially with NH3 present. The ASC demonstrated high NH3 conversion efficiency even at low temperatures, making it suitable for engine start-up and warm-up phases. Under steady-state conditions with artificially increased NH3/NOX ratios, a significant reduction in NOx emission was achieved with the ASC. However, high NH3/NOX ratios increased nitrous oxide (N2O) formation and NH3 slip.

This experimental work investigates oxygenated bio-fuel component blends of butanol, pentanol and cyclopentanone with diesel on the combustion characteristics, gaseous emissions and particulate matter (PM). Furthermore, PM characteristics, including size distributions, morphology and nanostructure are investigated. The oxygen content on the sustainable fuel blend components (bio-alcohols and bio-ketone) and the lower cetane number leading to a longer ignition delay, larger premixed combustion phase and high mean peak combustion temperature reduced the total number of particle concentration by up to 91%. Characterisation of particles demonstrated morphological and nanostructural alterations, such as the reduction in primary particle size that would lead to greater particle oxidation reactivity. Furthermore, the combustion of oxygenated blends showed a reduction in the total hydrocarbon emissions and an increase in NO2 concentration. This research provides new knowledge to understand the effects of fuel properties on gaseous and particle emissions formation and characteristics. Overall this work demonstrates bio-alcohols and bio-ketones as low carbon fuels in unveiling strategies for vehicular emissions abatement.

This experimental study investigates the palladium/rhodium based three-way catalytic converter (TWC) in a H2 - gasoline dual-fuel spark ignition (SI) engine under stoichiometric and lean conditions. The work focused on lean-burn engine operating conditions with the aim of reducing NOX emissions during the combustion process, where the TWC is not effective, while improving the thermal efficiency of the engine. Under these lean-burn engine conditions, the combustion promoting properties of H2 allowed for maintained engine combustion stability as determined by the COVimep values even up to ultra lean conditions (λ=2.0). It was found that by reducing the combustion temperature through the application of lean conditions, engine out NOX emissions could be reduced or even eliminated, while under these conditions the TWC was effective in reducing engine-out carbon-based gaseous emissions.

Hollow fibre (HF)-based technologies for emission control, as an alternative to the traditional monolithic technology, offers a promising route to the uptake of non-PGM catalytic systems. In this work, a series of Cu-doped LaCoO3 perovskites were investigated as potential non-PGM Diesel Oxidation Catalysts (DOC). Two HF-based modules, comprising single-channel (i.e., 1CM) and four-channel (i.e., 4CM) HFs respectively, were impregnated with the best catalyst candidate, and their performance was tested under real exhaust gas conditions, using a single-cylinder diesel engine. Compared to the 1CM, the 4CM demonstrated enhanced CO conversion, and reduced performance towards Total Hydrocarbon (THC) conversion. Overall, these findings reveal the influence of HF morphology on catalytic performance, and in turn, will contribute towards the refinement of HF-based technology for emission control, as well as enabling the transition towards non-PGM catalytic systems.

This work presented the influence of metal oxides as the support for silver-supported catalysts on the catalytic oxidation of diesel particulate matter (DPM). The supports selected to be used in this work were CeO2 (reducible), ZnO (semiconductor), TiO2 (reducible and semiconductor), and Al2O3 (acidic). The properties of the synthesized catalysts were investigated using XRD, TEM, H2-TPR, and XPS techniques. The DPM oxidation activity was performed using the TGA method. Different states of silver (e.g., Ag° and Ag+) were formed with different concentrations and affected the performance of the DPM oxidation. Ag2O and lattice oxygen, which were mainly generated by Ag/ZnO and Ag/CeO2, were responsible for combusting the VOCs. The metallic silver (Ag°) formed primarily on Ag/Al2O3 and Ag/TiO2 was the main component promoting soot combustion. Contact between the catalyst and DPM had a minor effect on VOC oxidation but significantly affected the soot oxidation activity.

Hydrogen is a promising future energy carrier due to its potential for production from renewable resources. It can be used in existing compression ignition diesel engines in a dual-fuel mode with little modification. Hydrogen's unique physiochemical properties, such as higher calorific value, flame speed, and diffusivity in air, can effectively improve the performance and combustion characteristics of diesel engines. As a carbon-free fuel, hydrogen can also mitigate harmful emissions from diesel engines, including carbon monoxide, unburned hydrocarbons, particulate matter, soot, and smoke. However, hydrogen-fueled diesel engines suffer from knocking combustion and higher nitrogen oxide emissions. This paper comprehensively reviews the effects of hydrogen or hydrogen-containing gaseous fuels (i.e., syngas and hydroxy gas) on the behavior of dual-fuel diesel engines. The opportunities and limitations of using hydrogen in diesel engines are discussed thoroughly. It is not possible for hydrogen to improve all the performance indicators and exhaust emissions of diesel engines simultaneously. However, reformulating pilot fuel by additives, blending hydrogen with other gaseous fuels, adjusting engine parameters, optimizing operating conditions, modifying engine structure, using hydroxy gas, and employing exhaust gas catalysts could pave the way for realizing safe, efficient, and economical hydrogen-fueled diesel engines. Future work should focus on preventing knocking combustion and nitrogen oxide emissions in hydrogen-fueled diesel engines by adjusting the hydrogen inclusion rate in real time.

The use of alternative fuels, such as bio-alcohols, in advanced propulsion systems could a feasible strategy to address several of the current issues associated to the use of internal combustion engines fuelled by carbonaceous fossil fuels. Particularly, soot particles, are one of the key pollutants emitted from compression ignition engines. Therefore, the development of soot formation prediction models providing new understanding on the impact of alternative fuels combustion in compression ignition engines become essential for soot mitigation purposes.This study proposes a new semi-empirical model that predicts in-cylinder soot primary particle growth from an engine fuelled with alcohol-diesel fuel blends. The model uses macroscopic experimental measurements of engine parameters such as instantaneous in-cylinder pressure. Furthermore, an empirical correlation is presented predicting the mean soot primary particle size as a function of alcohol-diesel fuel blend properties and fuel/air ratio. The experimental measurement of primary soot particle mean size are obtained from High Resolution Transmission Electron Microscope (HT-TEM) micrographs obtained from soot particles collected via thermophoresis. Overall, the research findings presented in this work contributes to propose environmentally friendly fuel candidates for transportation.

Hydrogen (H2) appears as a fundamental alternative to conventional fuels to lead the decarbonization of the transportation sector based on internal combustion engine propulsion. Being well assumed that neat H2 combustion demands the analysis of the exhaust aftertreatment systems (ATS) requirements and performance, this is also very relevant when considering dual-fuel strategies. This work addresses the impact of H2 presence in the exhaust gases on the conversion efficiency of CO and THC in an oxidation catalyst operating under representative real driving conditions. A reaction mechanism is proposed to cover the main conversion paths of CO, HC, and H2, including the formation and consumption of high-energy surface reaction intermediates. The mechanism has been implemented into a faster-than-real-time reduced-order model for multi-layer washcoat honeycomb catalytic converters and validated against experimental data. The model is applied to analyze the influence of the H2 concentration on the CO and HC light-off time during a vehicle driving test cycle. A wide span of concentrations, ranging from expected amounts in the exhaust of a dual-fuel Diesel engine to post-injected H2 strategies, was considered. Post-injection interest is analyzed regarding the eventual tradeoff between light-off and cumulative conversion efficiency in driving cycles and increased energy consumption. Additionally, the benefits in light-off time and increased reactivity were also assessed as a potential for catalyst downsizing at the expense of stress on the reactor in terms of bulk mass transfer limitations and pressure drop increase.

Reduction of CO2 emissions is a prevalent subject in the transportation sector. Cylinder deactivation (CDA) provides a method to reduce CO2 emissions at part load. However, there is little consideration of how these strategies affect catalyst performance. Effects of two CDA strategies on catalyst performance were studied. The first strategy of open-loop lambda control CDA improved catalyst CO conversion to 100 % and prevented NH3 formation over the catalyst. There was a NOX penalty if the duration exceeded 5 seconds. The closed-loop CDA strategy increased catalyst temperature by 300 degrees C for durations of 60 seconds.Open-loop CDA can prevent NH3 formation and improve CO conversion. Closed-loop CDA strategy has potential to increase catalyst temperature and be effective at reducing light-off during cold starts without additional hardware. This gives the strategy an advantage over more complex heating options. Both strategies provide opportunities to help meet current and future emission regulations.

This study proposes 3D-printed diamond-based lattice substrates as catalytic converters in the automotive aftertreatment system to improve vehicle cold-start emissions. The study aimed to compare the influence of 3D-printed diamond-based catalyst structures on the light-off behaviour compared to the conventional 400 Cell Per Square Inch (CPSI) honeycomb catalyst design in a real exhaust gas environment. Moreover, the benefits of H-2 addition on the performance of advanced lattice structures are examined for the first time to further increase the low-temperature catalytic efficiency. Digital Light Processing (DLP) technology was effectively utilised to manufacture lattice structures with high cell density to allow a comparison between conventional and advanced geometry designs. Further, the 3D-printed substrates were catalyst coated, and their light-off behaviour was studied in a diesel exhaust environment. The results of the light-off showed a significant improvement in the light-off temperatures for CO, THC and NO in the 3D-printed lattice structures. Furthermore, H-2 presence additionally enhanced the low-temperature activity of the AM lattice structures. (c) 2023 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/).