Hydrogen Blends Research Articles

Prediction of Efficiency, Performance, and Emissions Based on a Validated Simulation Model in Hydrogen–Gasoline Dual-Fuel Internal Combustion Engines

This study explores the performance and emissions characteristics of a dual-fuel internal combustion engine operating on a blend of hydrogen and gasoline. This research began with a baseline simulation of a conventional gasoline engine, which was subsequently validated through experimental testing on an AVL testbed. The simulation results closely matched the testbed data, confirming the accuracy of the model, with deviations within 5%. Building on this validated model, a hydrogen–gasoline dual-fuel engine simulation was developed. The predictive simulation revealed an approximately 5% increase in overall engine efficiency at the optimal operating point, primarily due to hydrogen’s combustion properties. Additionally, the injected gasoline mass and CO₂ emissions were reduced by around 30% across the RPM range. However, the introduction of hydrogen also resulted in a slight reduction (~10%) in torque, attributed to the lower volumetric efficiency caused by hydrogen displacing intake air. While CO emissions were significantly reduced, NOₓ emissions nearly doubled due to the higher combustion temperatures associated with hydrogen. This research demonstrates the potential of hydrogen–gasoline dual-fuel systems in reducing carbon emissions, while highlighting the need for further optimization to balance performance with environmental impact.

Numerical Investigation of CO and NO Production From Premixed Hydrogen/Methane Fuel Blends

Abstract There is significant interest in utilizing hydrogen as an energy carrier in a net-zero carbon energy economy. A variety of fundamental and practical issues associated with premixed hydrogen/methane combustion must be addressed, particularly flame flashback, combustion instabilities, and NOx emissions. Significantly less attention has been given to CO emissions from hydrogen blending. However, recent H2 blending engine tests have clearly noted major reductions in CO emissions, reductions which substantially exceed what would be expected based upon C atom mass balances in the fuel. Moreover, NOx, CO, and combustor operability always tradeoff with each other, and so, for example, these CO reductions can also enable operational or design modifications to reduce NOx emissions and/or wider operability windows. This paper addresses H2 blending effects on CO emissions, addressing both the direct influences on CO emissions, as well as how it influences NOx–CO tradeoffs. The paper presents computations that differentiate between the kinetic and equilibrium effects of H2 blending, as well as how H2 blending can lead to reductions in both NOx and CO by moving the Pareto front downward. Finally, this work suggests that H2 blending, in addition to its CO2 reductions, can also increase plant operational flexibility and so provide additional value propositions to an evolving electricity market.

Techno-economic analysis of green hydrogen integration into existing pipeline infrastructure: A case study of Wyoming

While green hydrogen production technologies like electrolysis have reached commercial scale, the primary challenge centers on efficient, and economically viable transportation of hydrogen. This study proposes an integrated geospatial techno-economic modeling approach to optimize hydrogen transportation through blending in existing pipelines. The simulations strategically locate green hydrogen production and blending points. The paper evaluates blending ratios, flow dynamics, and operating parameters to optimize hydrogen blending in natural gas pipelines. A techno-economic analysis quantifies costs and revenues across the supply chain, identifying the most economically viable hydrogen blending locations. The approach is validated through a case study in Wyoming, providing insights for industry stakeholders considering hydrogen-natural gas blending as a transition strategy. This integrated method offers a robust decision support tool for leveraging existing infrastructure to realize hydrogen's potential as a sustainable energy vector contributing to the broader goal of cleaner energy alternatives.

Gas Pipeline Leak Detection by Integrating Dynamic Modeling and Machine Learning Under the Transient State

This study focused on developing machine learning models to detect leak size and location in transient state conditions. The model was designed for an onshore methane–hydrogen blending gas pipeline in Canada. Base case simulations revealed significant effects on mass flow and pressure due to leaks, with the system taking approximately 6 h to reach a steady state from transient conditions. This made it essential to analyze the flow characteristics during the transient state. Trend data from the pipeline’s inlet and outlet were examined, considering the leak size and location. To better represent the data over time, a method was used to create two-dimensional images, which were then fed into a CNN (convolutional neural network) for training. The model’s accuracy was assessed using classification accuracy and a confusion matrix. By refining the data acquisition process and implementing targeted screening procedures, the model’s classification accuracy increased to over 80%. In conclusion, this study demonstrates that machine learning can enable rapid and accurate leak detection in transient state conditions. The findings are expected to complement existing leak detection methods and support operators in making faster, more informed decisions.

Effects of hydrogen blending ratios and CO2 on hydrogen embrittlement of X65 steel in high-pressure offshore hydrogen-blended natural gas pipelines

In this study, the effects of hydrogen blending ratios and high CO2 content on hydrogen embrittlement (HE) of offshore natural gas X65 pipeline steel were investigated. In high-pressure hydrogen gas, the impact of hydrogen content on yield strength and tensile strength was minimal. However, the effect on elongation was more significant, with the area decreasing and the HE index increasing until the hydrogen-blended ratio approached 30%, at which point the HE index reached 8.94%. Introducing CO2 into high-pressure hydrogen-rich gas further increased the HE index with high CO2 content. At 40% CO2, the HE index was 2.42 times higher than in high-pressure hydrogen-blended mixtures (30% H2). Additionally, the local fracture morphology transitions from ductile to quasi-cleavage fracture with the addition of CO2 and H2.

Laminar burning characteristics of ammonia and hydrogen blends at elevated initial pressures up to 2.5 MPa

Ammonia is a highly promising alternative fuel, and blending it with hydrogen can mitigate its poor combustion performance. However, the combustion mechanism of ammonia-hydrogen mixtures requires further validation through measurements of laminar burning velocity, particularly under high-pressure conditions relevant to practical combustors. Experimental data at high initial pressures (>1.0 MPa) are notably scarce. In this study, experiments were conducted using an outwardly propagating spherical flame in a high-pressure, high-temperature, constant-volume combustion chamber to determine the laminar burning velocities of ammonia-hydrogen blends at elevated initial pressures. The effects of different equivalence ratios (0.6 ∼ 1.4), volumetric hydrogen ratios (0.1 ∼ 0.6), and initial pressures (0.1 ∼ 2.5 MPa) were evaluated. Chemical kinetics of ammonia and hydrogen combustion was investigated at high pressures. The experimental results were compared with the simulation results under a wide range of conditions using several existing mechanisms to evaluate their applicability. The results show that the laminar burning velocity increases first and then decreases as the equivalence ratio (ϕ) increases and reaches a maximum value around ϕ of 1.1. The laminar burning velocity increases non-linearly with the volumetric hydrogen ratio, with more pronounced acceleration at higher hydrogen ratios. In contrast, the laminar burning velocity decreases non-linearly with the increasing initial pressure, and this reduction becomes progressively slower as the initial pressure rises. The predictive performance of the mechanisms by Okafor et al. and Gotama et al. is relatively satisfactory under certain conditions, but further optimization based on experimental data is necessary. Additionally, reaction pathway analysis of ammonia-hydrogen combustion indicates that introducing hydrogen increases the concentration of active radicals such as OH, O, and H, thereby enhancing ammonia combustion. Sensitivity analysis of the laminar burning velocity identified the critical elementary reactions across varying pressures, providing strong support for optimizing ammonia-hydrogen chemical kinetics models and developing simulation models for practical combustion systems.

Experimental and Statistical Assessment for Hydrogen-Powered Dual-fuel Diesel Engine Using a Novel Biodiesel Blend at Variable Injection Pressure

Hydrogen has been proven to be a potential fuel alternative in the area of field of transportation and power generation. The study aimed to improve the efficiency of a dual-fuel engine running on a blend of biodiesels and hydrogen by optimizing operating parameters. This involved varying the injection pressure of pilot fuel (220, 240, and 260 bar) and adjusting engine load (ranging from 20% to 100% in increments of 20% in five steps). The results indicate that maximum brake thermal efficiency of 28.11 % and liquid fuel substitution by 85% when the injection pressure of pilot fuel was set to 240 bar at 100 % engine load. At 100% load, setting the injection pressure of fuel to 240 bar resulted in a substantial drop in the emissions of carbon monoxide and hydrocarbons by 9.27% and 47.61%, respectively. The response surface methodology specified that the optimized value of the engine load and pilot fuel injection pressure was found to be 55.93% and 242.731 bar, respectively for achieving optimum results of response variables from the engine.

Enhancing safety in hydrogen storage: Understanding the dynamic process in hydrogen-methane mixtures during the pressurized leakage

Using natural gas pipelines for hydrogen-doped transportation represents a cost-effective solution for large-scale and long-distance hydrogen transport. However, concerns have been raised regarding the potential for leakage under high-pressure conditions, which could result in the spontaneous combustion of the leaking hydrogen. It is, therefore, imperative to understand the gas dynamics involved in methane-hydrogen mixtures during high-pressure leaks to ensure the safety of hydrogen storage. In the present work, the release process and the spontaneous ignition of hydrogen/methane mixtures with a hydrogen blending ratio from 0.1 to 1.0 from pressurized storage containers (20 MPa) have been numerically studied upon validated models. The findings indicate that spontaneous ignition occurs in the mixtures with any hydrogen blending ratios under the releasing pressure of 20 MPa, but the methane component is not involved in the initial combustion if the hydrogen blending ratio is less than 0.5. As the hydrogen blending ratio increases, more combustible components are involved in the initial ignition, and the location of the initial ignition turns closer to the leakage port. Meanwhile, as the hydrogen blending ratio rises from 0.1 to 1.0, the shockwave propagation is accelerated with the moment the shockwave first reflects is advanced from 58 to 60 μs to 22–24 μs, and the maximum temperature in the early leakage will exceed 3000 K. Furthermore, a higher hydrogen blending ratio leads to a more rapid pressure rise in the external space (reaching peak pressure at 191 μs for pure hydrogen) and forming a Mach disk structure with higher Mach numbers (around 7). These findings provide critical insights for understanding the combustion behavior of hydrogen/methane mixtures in high-pressure pipelines and offer valuable guidance for developing safety protocols and infrastructure designs.

Research on aerodynamic performance of centrifugal compressors for hydrogen-mixed natural gas.

Natural gas-doped hydrogen transportation has been widely used in industrial engineering. The change of the physical parameters of the conveying medium affects the working performance of the centrifugal compressor. This study aims to explore the aerodynamic performance of centrifugal compressors for hydrogen mixed natural gas, including the effects of hydrogen blending ratio (HBR) and inlet temperature on the pressure ratio and isentropic efficiency of compressors. The numerical simulation method is used and the results are compared with the experimental results to determine the reliability of the numerical simulation method. The results show that the pressure ratio decreases with the increase of HBR where the inlet temperature and rotation speed are constant. The pressure ratio and efficiency of the compressor are the highest when the conveying medium is pure natural gas (HBR = 0). The maximum pressure ratio reduction is 4.8% when the HBR is 5% and the inlet temperature is increased by 20 K. In summary, when the conveying medium of the compressor changes from pure natural gas to hydrogen-mixed natural gas, the working range and efficiency of the compressor will be reduced. Therefore, it is necessary to increase the rotation speed of the compressor or redesign the centrifugal compressor for hydrogen-mixed natural gas in order to achieve a constant flow rate at the outlet of the compressor.

Hydrogen enriched natural gas-fueled solid oxide fuel cells supported by Ni-Cu co-doping CeO2-δ catalyst-modified finger-like pore anode

Hydrogen blending in natural gas pipelines is one of the key technologies to realize the long-distance hydrogen transmission, which facilitates the large-scale hydrogen utilization. Solid oxide fuel cells can directly use hydrogen enriched natural gas (HENG, with 20 % H2) to generate electricity without separating and purifying the hydrogen, which enables the efficient conversion of hydrogen energy. In this work, finger-like pore anodes and Ni0.05Cu0.05Ce0.9O2-δ (NCCO) catalyst are prepared to address the need for anode performance and stability with hydrogen-doped natural gas fuels. The results show that NiCu@CeO2 precipitates NiCu nano-alloys on the surface after reduction treatment, which is beneficial for the anode activity. With NCCO catalyst, the maximum power densities of the single cells are 970 mW cm−2 and 700 mW cm−2 at 750 °C under wet H2 and HENG fuel atmospheres, respectively. At 750 °C, the methane conversion is as high as 46 %. More importantly, the single cell can run smoothly for 150 h, with the constant voltage (0.8 V) discharge and HENG as fuel gas. Our results confirm that the synthesized NCCO catalysts have excellent ability to catalyze CH4 and carbon resistance.

Understanding Environmental Barrier Coating Lifetimes and Performance for Industrial Gas Turbines

Abstract Hydrogen or hydrogen blend fuels are expected to replace natural gas in land-based industrial gas turbines (IGTs) to support a greener power economy. Silicon carbide (SiC) base ceramic matrix composites (CMCs) are considered for replacement of Ni-based superalloys to facilitate future efficiency improvements. SiC CMCs require environmental barrier coatings (EBCs) to mitigate volatilization from high-temperature steam, thus making the EBC lifetime critical information for identifying CMC component lifetimes. The goal of this project is to determine the maximum bond coating temperature underneath the EBC for achieving an IGT component lifetime goal of 25,000 h, which is far greater than current CMC component lifetime requirements for aeroturbine applications. To provide data for the lifetime model, laboratory testing used atmospheric plasma-sprayed rare-earth silicate EBCs on monolithic SiC substrates with an intermediate Si bond coating. Specimens exposed to 1-h thermal cycles in flowing air–steam environments and reaction kinetics were assessed from 700 °C to 1350 °C by measuring the thickness of the thermally grown silica scales. The silica growth and phase transformation appear critical in predicting EBC lifetime and several strategies have been explored to reduce the oxide growth rate and improve EBC durability at elevated temperatures. Advanced characterization using Raman spectroscopy has helped clarify this system.

Accelerated corrosion by nitrate-reducing bacteria and gaseous hydrogen permeation of X80 steel

Effects of hydrogen gas and Nitrate-Reducing Bacteria (NRB) on the corrosion and hydrogen permeation dynamics of X80 steel in simulated pipeline condensate water was investigated. Weight-loss analysis and electrochemical tests show a direct correlation between NRB-induced corrosion of X80 steel and the presence of hydrogen gas, particularly evident with escalating hydrogen blending ratios. Notably, corrosion primarily manifested through the formation of localized pitting, exhibiting a positive correlation with hydrogen blending ratios. Furthermore, the hydrogen permeating results show there is a synergistic enhancement of hydrogen permeating facilitated by the coexistence of hydrogen gas and NRB. Quantitative assessments of hydrogen permeability parameters highlighted significant amplifications in hydrogen diffusion flux (J) and apparent hydrogen concentration (Capp) under the combined influence of hydrogen and NRB, underscoring the complex interplay between these factors.

Multi-period operation of integrated electricity and gas systems with hydrogen blending considering gas composition dynamics

Green hydrogen from renewable sources can be blended with natural gas and serves as a potentially feasible measure for contributing to the net zero energy sector. The time-varying nature of hydrogen injection, influenced by stochastic renewable generations, can result in fluctuations in gas concentrations in the entire network. It poses a potential threat to the secure regulation of integrated electricity and gas systems (IEGS). For managing the operating condition and guaranteeing the security of IEGS during operation, a multi-period operation framework with alternative gas (e.g., hydrogen) blending is developed. First, a convex gas security range is derived using the Dutton method. Then, the multi-period operation framework is devised to mitigate the impacts of alternative gas injection on gas security over the entire operational period. Both the dynamics from gas composition and gas flow are modelled, accurately describing the real-time travel of alternative gas concentrations. The dynamics in the gas mixture properties (e.g., relative density) are fully revealed with time-varying gas concentrations. To tackle the high non-convexities in the optimization problem, second-order-cone relaxation is well-tailored and firstly used in the case of varying gas compositions, making the motion equations and advective transport equations more tractable. An advanced second-order-cone sequential programming is devised to drive the relaxation tight more efficiently. Finally, our operation strategy is illustrated in IEEE and Belgium Electricity and Gas Systems. Results indicate that hydrogen concentrations take about 12.5 h to travel from the injection point to the end of the pipeline route in the Belgium gas system. By incorporating this unique characteristic into the model, operational scheduling and dispatch in IEGS can be more practical when integrating hydrogen in the future.

Modeling and assessment of hydrogen-blended natural gas releases from buried pipeline

Blending hydrogen into natural gas pipelines for transportation reduces costs but increases safety risks. The main objective of this work is to explore the evolution of leakage hazards in hydrogen-blended natural gas pipelines and quantify these risks. To achieve this, multi-stage coupling numerical models are developed to explore the leakage hazards in hydrogen-blended natural gas transportation. The results show that the proposed model accurately predicts leakage rates of hydrogen-blended natural gas pipelines in various soil types. The gas diffusion pattern shifts from spherical to hemispherical, with the hazardous volume increasing linearly overall. The influence of pressure on leakage is amplified in the soil, while the impact of the leakage aperture is diminished. Although increasing the hydrogen blending ratio reduces the leakage rate, it also enhances the hazard evolution. Burial depth primarily affects alarm time, while an increase in leakage angle within 90–180° significantly delays the hazard evolution. Moreover, higher soil resistance not only mitigates the leakage diffusion but also reduces the pressure differential. The leakage aperture exhibits the highest correlation with the hazard evolution.

Fuel blend combustion for decarbonization

The utilization of fossil fuels is currently transforming to low-carbon or zero-carbon fuels, which is one of the solutions to global warming. Hydrogen and ammonia are regarded as promising zero-carbon fuels in power supply and transportation scenarios but the availability of hydrogen and their distinctly different chemical activity constrain their large-scale direct utilizations. Fuel blends with physical and chemical complementary are considered as the effective approaches in the utilization of hydrogen and ammonia because no significant modification to the existing end-user infrastructures is needed. This paper reports recent progress in the fundamental combustion behaviors of fuel blends, focusing on hydrogen-hydrocarbon blends and ammonia-hydrocarbon blends. Firstly, laminar flame behaviors, auto- and forced-ignition characteristics, and pollutant emissions of binary fuels containing hydrogen are reviewed, all of which are supplemented with a discussion on the governing hydrogen-enriched combustion chemistry. Subsequently, the hydrogen-enriched flame responses to the flow conditions are discussed, including the turbulent burning velocity and statistical structures, the flashback swirl flames, thermoacoustic instabilities, and the jet ignition characteristics; Furthermore, with the increasing concern over ammonia as a zero carbon fuel and its extremely weak reactivity, recent progress on combustion of fuel blends containing ammonia are also reviewed. The fundamental combustion chemistry studies including laminar burning velocity, the ignition delay times data collection, as well as the attempts for chemical kinetic modeling development for fuel blend with ammonia are presented. The literature reported ammonia containing blends of turbulent flame characteristics are presented. Finally, from an engineering point of view, examples using hydrogen blends in practical internal combustion engines and in gas turbines are introduced, including the topic of engine efficiency performance and pollutant emissions and different combustors for gas turbines. It is suggested that fuel blends with hydrogen or ammonia that potentially monitors the overall reactivity will be one realistic solution to de-carbonization, on the basis of current transportation and power generation systems.

Development of a Novel Correlation for Laminar Burning Velocity in Iso-Octane and Hydrogen Blends

Development of a Novel Correlation for Laminar Burning Velocity in Iso-Octane and Hydrogen Blends

Effects of hydrogen enrichment on the performance and emission characteristics of a diesel engine with the addition of Syzygium cumini (Jamun) biodiesel

ABSTRACT Biofuel made from Syzygium cumini, often known as Jamun, has the potential to be a low-cost, sustainable, and emission-free alternative. In this work, we experimentally explore the performance of a compression ignition (CI) engine that burns a blend of hydrogen and biodiesel. Hydrogen is pumped into the air intake manifold by means of a hydrogen gaseous supplement that, when exposed to atmospheric conditions, co-combusts with a pilot flame ignited by Jamun oil. To investigate the impact of hydrogen supplementation on performance and exhaust emission, a variety of hydrogen–Jamun fuel mixture proportions are provided to the engine. The research demonstrates that adding hydrogen improves the thermal efficiency (5%) of diesel engines whereas lowering specific energy fuel consumption (4%) at fixed Jamun flow rates. The gas emission data demonstrates that when hydrogen (HC) emission (12%) supplements decreases, NOx emission (10%) increases somewhat but opacity (8%) increases significantly. The experiment demonstrates that hydrogen and Jamun duel fuel in compression ignition engines burn smoothly.

Mathematical modeling for hydrogen blending in natural gas pipelines moving towards industrial decarbonization: Economic feasibility and CO2 reduction analysis

Hydrogen blending has proved to be a promising alternative to reduce CO2 emissions in current applications such as the industrial sector in which natural gas is the fuel source since it can mitigate GHG emissions and help to reach nation’s goal of decarbonization. This study explored the feasibility of different hydrogen blend compositions going from 1% to 30% hydrogen content (by volume) by computational simulations to determine the best performance of the system considering real operating conditions from Central Plant at UC Irvine. This work also performed an economic analysis as part of the implementation plan. It was determined that a blend of 19% H2 content could be implemented without any major renovation of utility infrastructure based on the operating conditions and change in the properties of the mixture. An addition of 30% H2 can reduce around 11% of the emissions produced by pure natural gas. This is equivalent to 1422 kg of CO2 in 1 h. It is evident that the higher the H2 content, the better the CO2 benefits that would be produced, but for the actual application of higher hydrogen content, there is a need for a better understanding of the effects of hydrogen in the current natural gas pipeline. Based on the CO2 savings, it was determined that a 30% blending of hydrogen may save about 22.2% of the economic cost compared to natural gas.

Towards hydrogen gas turbine engines aviation: A review of production, infrastructure, storage, aircraft design and combustion technologies

This study explores the potential of hydrogen gas turbine engines for sustainable aviation, with a particular focus on their development for low subsonic to transonic flight regimes. Hydrogen offers notable advantages, including zero CO2 emissions and high energy density. However, its widespread adoption is prevented by significant challenges in production, infrastructure, storage, aircraft design, and combustion technology. The limited availability of green hydrogen – the global production totaled only 127 kt in 2023, with 76% produced in China - raises concerns about the feasibility of a rapid shift to hydrogen-powered general aviation. Despite numerous pledges for hydrogen adoption in the Western world, major aircraft manufacturers have primarily engaged in marketing activities rather than substantial product innovation. To date, the only hydrogen aircraft demonstrator from this century is the 2012 Boeing Phantom Eye, which utilized modified hydrogen internal combustion engines rather than a gas turbine engine. The only hydrogen aircraft demonstrator with a gas turbine engine was the 1988 hybrid Tupolev Tu-155 which coupled one hydrogen gas turbine engine to other two jet fuel engines. This paper evaluates the current state of hydrogen gas turbine technology, comparing its combustion characteristics with traditional jet fuels and examining various NOx emission control techniques. It also investigates the potential of micro-mix lean combustion and staged combustion to achieve efficient and low-emission hydrogen combustion in gas turbines. Given the more extensive experience with terrestrial gas turbines compared to their aeronautical counterparts, the review includes insights from terrestrial power generation applications. Additionally, it considers hythane - a blend of hydrogen and natural gas - as a transitional solution for significantly reducing CO2 emissions while progressing towards net-zero targets. The review underscores the urgent need for advancements in green hydrogen production, technology, and infrastructure to overcome existing barriers and enable a more sustainable aviation future powered by hydrogen. Importantly, the review emphasizes the need to move beyond mere virtue signaling and make tangible progress toward a hydrogen economy.

Simulation of gas mixture dynamics in a pipeline network using explicit staggered-grid discretization

We develop an explicit staggered finite difference discretization scheme for simulating the transport of highly heterogeneous gas mixtures through pipeline networks. This study is motivated by the proposed blending of hydrogen into natural gas pipelines to reduce end use carbon emissions while using existing pipeline systems throughout their planned lifetimes. Our computational method accommodates an arbitrary number of constituent gases with very different physical properties that may be injected into a network with significant spatiotemporal variation. In this setting, the gas flow physics are highly location- and time- dependent, so that local composition and nodal mixing must be accounted for. The resulting conservation laws are formulated in terms of pressure, partial densities and flows, and volumetric and mass fractions of the constituents. We include non-ideal equations of state that employ linear approximations of gas compressibility factors, so that the pressure dynamics propagate locally according to a variable wave speed that depends on mixture composition and density. We derive compatibility relationships for network edge boundary values that are more complex than for a homogeneous gas. The simulation method is evaluated on initial boundary value problems for a single pipe and a small network, is cross-validated with a lumped element simulation, and used to demonstrate a local monitoring and control policy for maintaining allowable concentration levels.