Search Results (65)

Urban integrated energy systems (UIESs) play a critical role in facilitating low-carbon and high-efficiency energy transitions. However, existing scheduling strategies predominantly focus on energy quantity and cost, often neglecting the heterogeneity of energy quality across electricity, heat, gas, and hydrogen. This paper presents an exergy-enhanced stochastic optimization framework for the optimal scheduling of electricity–hydrogen urban integrated energy systems (EHUIESs) under multiple uncertainties. By incorporating exergy efficiency evaluation into a Stochastic Optimization–Improved Information Gap Decision Theory (SOI-IGDT) framework, the model dynamically balances economic cost with thermodynamic performance. A penalty-based iterative mechanism is introduced to track exergy deviations and guide the system toward higher energy quality. The proposed approach accounts for uncertainties in renewable output, load variation, and Hydrogen-enriched compressed natural gas (HCNG) combustion. Case studies based on a 186-bus UIES coupled with a 20-node HCNG network show that the method improves exergy efficiency by up to 2.18% while maintaining cost robustness across varying confidence levels. These results underscore the significance of integrating exergy into real-time robust optimization for resilient and high-quality energy scheduling. Full article

Hydrogen–gasoline dual-fuel spark ignition (SI) engines represent a promising transitional solution toward cleaner combustion and reduced carbon emissions. In a previous study, a predictive engine model was developed to simulate the performance and combustion characteristics of such systems; however, its accuracy was constrained by the use of estimated combustion parameters. This study presents an experimental validation based on high-resolution in-cylinder pressure measurements performed on a naturally aspirated SI engine operating with a 20% hydrogen energy share. The objectives are twofold: (1) to refine the combustion model using empirically derived combustion metrics, and (2) to evaluate the feasibility of moderate hydrogen enrichment in a stock engine configuration. To facilitate a more accurate understanding of how key combustion parameters evolve under different operating conditions, Vibe function was fitted to the ensemble-averaged heat release rate curves computed from 100 consecutive engine cycles at each static full-load operating point. This approach enabled the extraction of stable and representative metrics, including the mass fraction burned at 50% (MFB50) and combustion duration, which were then used to recalibrate the predictive combustion model. In addition, cycle-to-cycle variation and combustion duration were also investigated in the dual-fuel mode. The combustion duration exhibited a consistent and substantial reduction across all of the examined operating points when compared to pure gasoline operation. Furthermore, the cycle-to-cycle variation difference remained statistically insignificant, indicating that the introduction of 20% hydrogen did not adversely affect combustion stability. In addition to improving model accuracy, this work investigates the occurrence of abnormal combustion phenomena—including backfiring, auto-ignition, and knock—under enriched conditions. The results confirm that 20% hydrogen blends can be safely utilized in standard engine architectures, yielding faster combustion and reduced burn durations. The validated model offers a reliable foundation for further dual-fuel optimization and supports the broader integration of hydrogen into conventional internal combustion platforms. Full article

Gas turbines are widely used in power generation due to their reliability, flexibility, and high efficiency. As the energy sector transitions towards low-carbon alternatives, hydrogen and ammonia are emerging as promising fuels. This study investigates the thermodynamic and combustion performance of a GE LM6000 gas turbine fueled by methane/hydrogen and methane/ammonia fuel blends under varying levels of oxygen enrichment (21%, 30%, and 40% $O_2$ by volume). Steady-state thermodynamic simulations were conducted using Aspen HYSYS, and combustion modeling was performed using ANSYS Chemkin-Pro, assuming a constant thermal input of 102 MW. Results show that increasing hydrogen content significantly raises flame temperature and burning velocity, whereas ammonia reduces both due to its lower reactivity. Net power output and thermal efficiency improved with higher fuel substitution, peaking at 43.46 MW and 42.7% for 100% $N{H}_3$. However, $N{O}_{\mathrm{x}}$ emissions increased with higher hydrogen content and oxygen enrichment, while $N{H}_3$ blends exhibit more complex emission trends. The findings highlight the trade-offs between efficiency and emissions in future low-carbon gas turbine systems. Full article

The global emphasis on clean energy has increased interest in producing hydrogen from petroleum reservoirs through in situ combustion-based processes. While field practices have demonstrated the feasibility of co-producing hydrogen and oil, the question of which offers greater economic potential, oil, or hydrogen, remains central to ongoing discussions, especially as researchers explore ways to produce hydrogen exclusively from petroleum reservoirs. This study presents the first integrated techno-economic model comparing oil and hydrogen production under varying injection strategies, using CMG STARS for reservoir simulations and GoldSim for economic modeling. Key technical factors, including injection compositions, well configurations, reservoir heterogeneity, and formation damage (issues not addressed in previous studies), were analyzed for their impact on hydrogen yield and profitability. The results indicate that CO₂-enriched injection strategies enhance hydrogen production but are economically constrained by the high costs of CO₂ procurement and recycling. In contrast, air injection, although less efficient in hydrogen yield, provides a more cost-effective alternative. Despite the technological promise of hydrogen, oil revenue remains the dominant economic driver, with hydrogen co-production facing significant economic challenges unless supported by policy incentives or advancements in gas lifting, separation, and storage technologies. This study highlights the economic trade-offs and strategic considerations crucial for integrating hydrogen production into conventional petroleum extraction, offering valuable insights for optimizing hydrogen co-production in the context of a sustainable energy transition. Additionally, while the present work focuses on oil reservoirs, future research should extend the approach to natural gas and gas condensate reservoirs, which may offer more favorable conditions for hydrogen generation. Full article

The use of hydrogen as a fuel for piston engines enables environmentally friendly and efficient operation. However, several challenges arise in the combustion process, limiting the development of hydrogen engines. These challenges include abnormal combustion, the high burning velocity of hydrogen-enriched mixtures, increased nitrogen oxide emissions, and others. A rational organization of hydrogen combustion can partially or fully mitigate these issues through the use of advanced methods such as late direct injection, charge stratification, dual injection, jet-guided operation, and others. However, mathematical models describing hydrogen combustion for these methods are still under development, complicating the optimization and refinement of hydrogen engines. Previously, we proposed a mathematical model based on Wiebe functions to describe premixed and diffusion combustion, as well as relatively slow combustion in lean-mixture zones, behind the flame front, and near-wall regions. This study further develops the model by accounting for the combined influence of the mixture composition and engine speed, mixture stratification, and the effects of injection and ignition parameters on premixed and diffusion combustion. Special attention is given to combustion modeling in an engine with single injection and jet-guided operation. Full article

Ammonia (NH₃) and hydrogen (H₂) are considered promising fuels for the power sector’s decarbonization. Their combustion is capable of producing energy with zero direct CO₂ emissions, and ammonia can act as a stable energy H₂ carrier. This study numerically investigates the design and implementation of staged combustion of a mixture of NH₃/H₂ by means of CFD simulations. The investigation employed the single-phase flow RANS governing equations and the eddy dissipation concept (EDC) combustion model, with the incorporation of a detailed kinetic mechanism. The combustion chamber operates under the RQL (rich–quench–lean) combustion regime. The first stage operates under rich conditions, firing mixtures of ammonia in air, enriched by hydrogen (H₂) to enhance combustion properties in a swirl and bluff-body stabilized burner. The secondary stage injects additional air and hydrogen to mitigate unburnt ammonia and NO_x emissions. Simulations of the first stage were performed for a thermal input ranging from 4 kW to 8 kW and flames with an equivalence ratio of 1.2. In the second stage, additional hydrogen is injected with a thermal input of either 1 kW or 2 KW, and air is added to adjust the global equivalence ratio to 0.6. Full article

This study utilizes a zero-dimensional, constant-pressure, perfectly stirred reactor (PSR) model within the Cantera framework to examine the combustion characteristics of hydrogen, methane, methanol, and propane, both singly and in hydrogen-enriched mixtures. The impact of the equivalence ratio (ϕ = 0.75, 1.0, 1.5), fuel composition, and residence duration on temperature increase, heat release, ignition delay, and emissions (NO_x and CO₂) is methodically assessed. The simulations are performed under steady-state settings to emulate the ignition and flame propagation processes within pre-chambers and primary combustion zones of internal combustion engines. The results demonstrate that hydrogen significantly improves combustion reactivity, decreasing ignition delay and increasing peak flame temperature, especially at short residence times. The incorporation of hydrogen into hydrocarbon fuels, such as methane and methanol, enhances ignition speed, improves thermal efficiency, and stabilizes lean combustion. Nevertheless, elevated hydrogen concentrations result in increased NO_x emissions, particularly at stoichiometric equivalence ratios, due to higher flame temperatures. The examination of fuel mixtures at varying hydrogen concentrations (10–50% by mole) indicates that thermal performance is optimal under stoichiometric settings and diminishes in both fuel-lean and fuel-rich environments. A thermodynamic model was created utilizing classical combustion theory to validate the heat release estimates based on Cantera. The model computes the heat release per unit volume (MJ/m³) by utilizing stoichiometric oxygen demand, nitrogen dilution, fuel mole fraction, and higher heating values (HHVs). The thermodynamic estimates—3.61 MJ/m³ for H₂–CH₃OH, 3.43 MJ/m³ for H₂–CH₄, and 3.35 MJ/m³ for H₂–C₃H₈—exhibit strong concordance with the Cantera results (2.82–3.02 MJ), thereby validating the physical consistency of the numerical methodology. This comparison substantiates the Cantera model for the precise simulation of hydrogen-blended combustion, endorsing its use in the design and development of advanced low-emission engines. Full article

Deep learning-based surrogate models have received wide attention for efficient and cost-effective predictions of fluid flows and combustion, while their hyperparameter settings often lack generalizable guidelines. This study examines two different types of surrogate models, convolutional autoencoder (CAE)-based reduced order models (ROMs) and fully connected autoencoder (FCAE)-based ROMs, for emulating hydrogen-enriched combustion from a triple-coaxial nozzle jet. The performances of these ROMs are discussed in detail, with an emphasis on key hyperparameters, including the number of network layers in the encoder (l), latent vector dimensionality (dim), and convolutional stride (s). The results indicate that a larger l is essential for capturing features in strongly nonlinear flowfields, whereas a smaller l is more effective for less nonlinear distributions, as additional layers may cause overfitting. Specifically, when employing CAE-based ROMs to predict the spatial distribution for H₂ ($X_{H_2}$) with weak nonlinearity, the reconstruction absolute average relative deviation (AARD) from the two-layer model was marginally higher than that of three- and four-layer models, whereas the prediction AARD was approximately 5% lower. A smaller dim yields better performance in weakly nonlinear flowfields but may increase local errors in some cases due to excessive feature compression. A CAE-based ROM with a dim = 10 achieved a notably lower AARD of 4.01% for $X_{H_2}$ prediction. A smaller s may enhance the spatial resolution yet raise computational costs. Under identical hyperparameters, the CAE-based ROM outperformed the FCAE-based ROM in both cost-effectiveness and accuracy, achieving a 35 times faster training speed and lower absolute average relative deviation in prediction. These findings provide important guidelines for hyperparameter selection in training autoencoder (AE)-based ROMs for hydrogen-enriched combustion and other similar engineering design problems. Full article

To reduce dependence on fossil fuels, gas turbine plants using hydrogen/methane blends provide a crucial solution for decarbonizing thermal power generation and promoting a sustainable energy transition. In this context, the development of fuel-flexible burners is fundamental. This work reports the development of a novel burner geometry for gas turbines that can operate with natural gas and hydrogen mixtures (HENG, hydrogen-enriched natural gas) over a wide range of hydrogen content while maintaining low NO_x emissions. The methodology used in this work is multidisciplinary, incorporating (i) CFD numerical simulations to determine the burner’s geometry, (ii) mechanical design for prototype construction (not discussed in the article), and (iii) experimental tests to assess its hydrogen content capacity, stabilization, and pollutant emission characteristics. The geometry was initially optimized through several RANS simulations to enhance reactant mixing and minimize flashback risks. Additionally, some LES simulations were conducted under specific conditions to achieve more accurate predictions and investigate potential combustion dynamics issues. The proposed solution was then transferred into a prototype. Through experimental testing, the burner prototype was characterized in terms of four key performance indicators: (1) the ability to operate with HENG mixtures with more than 20% ${\mathrm{H}}_2$ content, showing a technological trend exceeding 50%; (2) the ability to operate with low ${\mathrm{NO}}_{\mathrm{x}}$ (<25 ppm) and CO emissions within the 30–70% hydrogen volume range; (3) the ability to ignite HENG mixtures with ${\mathrm{H}}_2$ in the 30–70% hydrogen volume range; and (4) the ability to operate with a fluctuating hydrogen content, ±15% over time, while still complying with ${\mathrm{NO}}_{\mathrm{x}}$ and CO emission limits. Full article

Hydrogen has been presented as a promising energy vector in decarbonized economies. Its singular properties can affect important aspects of industrial flames, such as the temperature, emissions, and radiative/convective energy transfer balance, thus requiring in-depth studies to optimize combustion processes using this fuel isolate or in combination with other renewable alternatives. This work aims to conduct a detailed numerical analysis of temperatures and gas emissions in the combustion of biomethane enriched with different proportions of hydrogen, with the intent to contribute to the understanding of the impacts of this natural gas surrogate on practical combustion applications. RANS k-$\omega$ and k-$ϵ$ turbulence models were combined with the GRI Mech 3.0, San Diego, and USC mechanisms using the ANSYS-Fluent 2024-R2 softwareto evaluate its performance regarding flame prediction. The Moss–Brookes model was adopted to predict soot formation for the methane flames by solving transport equations for normalized radical nuclei concentration and the soot mass fraction. The Discrete Ordinates (DOs) method with gray band model was applied to solve the Radiation Transfer Equation (RTE). The results of the experiments and numerical simulations highlight the importance of carefully selecting turbulence and chemical kinetics models for an accurate representation of real-scale industrial burners. Relative mean errors of 1.5% and 6.0% were registered for temperature and pollutants predictions, respectively, with the USD kinetics scheme and k-$omega$ turbulence model presenting the most accurate results. The operational impacts of hydrogen enrichment of biomethane flames were accessed for a practical combustion system. With 15% of hydrogen blending, the obtained results indicate a 73% penalty in CO emissions, an increase of 6% in NO emissions, and a 34 K flame temperature increase. Also, a reduction in flame radiation due to hydrogen enrichment was observed for hydrogen concentrations above 20%, a behavior that can affect practical combustion systems such as those in glass and other ceramics industries. Full article

This study explores the potential of hydrogen-enriched internal combustion engines (H2ICEs) as a sustainable alternative to fossil fuels. Hydrogen offers advantages such as high combustion efficiency and zero carbon emissions, yet challenges related to NO_x formation, storage, and specialized modifications persist. Machine learning (ML) techniques, including artificial neural networks (ANNs) and XGBoost, demonstrate strong predictive capabilities in optimizing engine performance and emissions. However, concerns regarding overfitting and data representativeness must be addressed. Integrating AI-driven strategies into electronic control units (ECUs) can facilitate real-time optimization. Future research should focus on infrastructure improvements, hybrid energy solutions, and policy support. The synergy between hydrogen fuel and ML optimization has the potential to revolutionize internal combustion engine technology for a cleaner and more efficient future. Full article

Methane–hydrogen–air mixtures present a viable alternative to conventional fuels, reducing CO₂ emissions while maintaining high energy density. This study numerically investigates their combustion characteristics in millimeter-scale reactors, focusing on flame stabilisation and combustion dynamics in confined spaces. A species transport model with volumetric reactions incorporated a detailed kinetic mechanism with 16 species and 41 reactions. The simulations employed a laminar flow model, second-order upwind discretisation, and SIMPLE algorithm for pressure–velocity coupling. The key parameters analysed include equivalence ratio, hydrogen volume fraction, inlet velocity, and gas pressure and their impact on fuel conversion efficiency and heat release was evaluated. The results indicate that hydrogen enrichment enhances flame stability and combustion efficiency, with optimal performance over 40% hydrogen content. Additionally, increased outlet pressure raises flame temperature by 15%, while larger reactor diameters reduce heat losses, improving combustion efficiency by 20%. Emissions of CO decrease significantly at higher hydrogen fractions, demonstrating the potential for cleaner combustion. These findings support the integration of methane–hydrogen mixtures into sustainable energy systems, providing insights for designing efficient, low-emission micro-combustors. Full article

This paper investigates the emission characteristics of hydrogen-enriched gasoline (95G5H₂) under dynamic driving situations in order to fulfill the growing need for cleaner and more efficient automobile fuels. This study aimed to investigate the impact of hydrogen addition on pollutant-specific emissions, including CO, CO₂, HC, and NO_x, using a Nissan Qashqai that ran on both pure gasoline (100G) and 95G5H₂. Emission statistics were obtained by computer simulations of the Worldwide Harmonized Light Vehicles Test Cycle (WLTC) applied using AVL CRUISE software. The paper presents a method of comparing the characteristics of pollutants emitted by the combustion engine and comparing the pollutants emitted when powered by regular fuel and fuel with hydrogen. The tests were performed in real conditions, and the presented method shows the amount of pollutants emitted when the vehicle is directly in motion, which allows for effective comparison of the amount of pollutants emitted for different fuels. 95G5H₂ sharply reduces CO-, CO₂-, and HC-specific emissions by 22.19%, 14.55%, and 35.46%, respectively, when compared to 100G. However, NO_x-specific emissions increased by 20.17%, suggesting a compromise between higher combustion efficiency and higher burning temperatures. The study shows that 95G5H₂ fuel performs better in urban driving cycles, including plenty of acceleration and deceleration, which usually results in incomplete combustion. Although additional refinement is needed to cut NO_x-specific emissions, the results demonstrate that hydrogen-enriched fuels have considerable potential to lower vehicle-specific emissions. The significant conclusions of the study on the advantages of hydrogen-enriched fuels, both practically and environmentally, will help in the future development of environmentally friendly transportation solutions. Full article

Industrial development and population growth have significantly escalated worldwide energy demand; in addition, the heightened consumption of primary energy sources such as hydrocarbons has profoundly impacted the atmospheric environment. Among all potential fuels, hydrogen provides the most significant advantages for energy supply and environmental sustainability. Nonetheless, the combustion of pure hydrogen has challenges related to its production, storage, and utilization. A more effective approach to improve combustion is to utilize hydrogen as an addition to fossil fuels. Hydrogen possesses numerous characteristics that render it a compelling fuel alternative. It possesses high energy density, offering triple the energy compared to liquefied petroleum gas. This indicates that hydrogen is able to deliver equal power output with reduced fuel usage, thus decreasing the fuel used and, consequently, greenhouse gasses linked to combustion. In this study, practical experiments and computer simulations were adopted to predict the behavior of some characteristics of the combustion of Iraqi liquefied petroleum gas, such as flame temperature and laminar burning velocity, in addition to the effect of changing the equivalence ratio and hydrogen enrichment at rates ranging between 5 and 20% at a constant atmospheric pressure and temperature. In the practical aspect, a counter-flow burner was developed at the Training and Workshops Center, University of Technology, Iraq, for the purpose of performing practical experiments. In addition, a MATLAB R2023b program code was developed based on flame front image frames to analyze data and measure flame parameters, i.e., laminar burning velocity, flame temperature, and flame front diameter. While the commercial CFD Ansys Fluent version 17.2 program was used to numerically simulate the premixed counter-flame, the steady laminar flame (SLF) was used. Also, in order to implement the continuity of the numerical simulation, the momentum and energy equations of the counter-flow burner were solved. The results showed that increasing the hydrogen percentage caused an increase in the laminar burning velocity as well as the flame temperature; when the hydrogen percentage in the mixture was 20%, the increasing percentages in the practical experiments were about 25% and 19.6%, respectively, and the percentages in the numerical simulation were about 22.6% and 20.5%, respectively. Also, changing the equivalence ratio from 0.4 to 1.4 had an effect on the shape, color, and method of flame spread, where at the higher percentage, the shape changed and the color concentration increased, meaning that the temperature rose and the method of spread changed to an irregular one. Additionally, several recommendations are suggested for future endeavors in this domain. Full article

Mixtures of hydrogen with common hydrocarbon fuels are considered viable for reducing carbon footprint in modern industry, power production, and transportation. The addition of hydrogen alters the kinetics and thermophysical properties of the mixtures, as well as the composition and properties of combustion products, requiring detailed research into the features of flame propagation in hydrogen-enriched hydrocarbon–air mixtures. Of particular interest are also the safety aspects of such fuels. In this paper, experimental results are presented on the premixed laminar flame propagation in channels formed by two closely spaced plates (Hele-Shaw cell), with the internal straight walls forming a diverging (diffuser) channel with the opening angles between 5 and 25 degrees. Methane–hydrogen–air mixtures with the hydrogen relative contents of 0%, 25%, and 50% and global equivalence ratio of unity were ignited by a spark near the closed narrow end of the channel. Experiments were performed with the gap width of 3.5 mm; video recordings were processed in order to determine the quantitative features of the flame front propagation (leading and trailing point coordinate, coordinates of the cusps, cell sizes and shapes). The main features of flame propagation (fast initial expansion, development of cellular flame, self-induced longitudinal oscillations) are obtained and compared to clarify the effect of hydrogen contents in the fuel and channel geometry (gap width, opening angle). Full article