United Kingdom
Optimal Hydrogen Infrastructure Planning for Heat Decarbonisation
Feb 2024
Publication
Energy decarbonisation is essential to achieve Net-Zero emissions goal by 2050. Consequently investments in alternative low-carbon pathways and energy carriers for the heat sector are required. In this study we propose an optimisation framework for the transition of heat sector in Great Britain focusing on hydrogen infrastructure decisions. A spatially-explicit mixed-integer linear programming (MILP) evolution model is developed to minimise the total system’s cost considering investment and operational decisions. The optimisation framework incorporates both long-term planning horizon of 5-year steps from 2035 to 2050 and typical days with hourly resolution. Aiming to alleviate the computational effort of such multiscale model two hierarchical solution approaches are suggested that result in computational time reduction. From the optimisation results it is shown that the installation of gas reforming hydrogen production technologies with CCS and biomass gasification with CCS can provide a cost-effective strategy achieving decarbonisation goal. What-if analysis is conducted to demonstrate further insights for future hydrogen infrastructure investments. Results indicate that as cost is highly dependent on natural gas price Water Electrolysis capacity increases significantly when gas price rises. Moreover the introduction of carbon tax policy can lead to lower CO2 net emissions.
Case Study: Quantitative Risk Assessment of Hydrogen Blended Natural Gas for an Existing Distribution Network and End-use Equipment in Fort Saskatchewan, Alberta
Sep 2023
Publication
In a first-of-its-kind project for Alberta ATCO Gas and Pipelines Ltd. (ATCO) began delivering a 5% blend of hydrogen (H2) in natural gas into a subsection of the existing Fort Saskatchewan natural gas distribution system (approximately 2100 customers). The project was commissioned in October 2022 with the intention of increasing the blend to 20% H₂ in 2023. As part of project due diligence ATCO in partnership with DNV undertook Quantitative Risk Assessments (QRAs) to understand any risks associated with the introduction of blended gas into its existing distribution system and to its customers. This paper describes key findings from the QRAs through the comparison of risks associated with H2 blended natural gas at concentrations of 5% and 20% H₂ and the current natural gas configuration. The impact of operating pressure and hydrogen blend composition formed a sensitivity study completed as part of this work. To provide context and to help interpret the results an individual risk (IR) level of 1 × 10-6 per year was utilised as a reference threshold for the limit of the ‘broadly acceptable’ risk level and juxtaposed against comparable risk scenarios. Although adding hydrogen increases the IR of ignited releases from mains services meters regulators and end user appliances the ignited release IR was always well below the broadly acceptable reference criterion for all operating pressures and blend cases considered as part of the project. The IR associated with carbon monoxide poisoning dominates the overall IR and the results demonstrate that the reduction in carbon monoxide poisoning associated with the introduction of H₂ blended natural gas negates any incremental risk associated with ignited releases due to H₂ blended gas. The paper also explains how the results of the QRA were incorporated into Engineering Assessments as per the requirements of CSA Z662:19 [1] to justify the conversion of existing natural gas infrastructure to H₂ blended gas infrastructure.
Mitigating Risks in Hydrogen-powered Transportation: A Comprehensive Risk Assessment for Hydrogen Refuelling Stations, Vehicles, and Garages
Oct 2024
Publication
Hydrogen is increasingly seen as a viable alternative to fossil fuels in transportation crucial to achieving net-zero energy goals. However the rapid expansion of hydrogen-powered transportation is outpacing safety standards posing significant risks due to limited operational experience involvement of new actors and lack of targeted guidelines. This study addresses the urgent need for a tailored comprehensive risk assessment framework. Using Structured What-If (SWIFT) and bowtie barrier analysis the research evaluates a hypothetical pilot project focusing on hydrogen refuelling stations vehicles and garages. The study identifies critical hazards and assesses the adequacy of current risk mitigation measures. Key findings reveal gaps in safety practices leading to 41 actionable steps and 5 key activities to help new actors manage hydrogen risks effectively. By introducing novel safety guidelines this research contributes to the development of safe hydrogen use and advances the understanding of hydrogen risks ensuring its sustainable integration into transportation systems.
Coupling Green Hydrogen Production to Community Benefits: A Pathway to Social Acceptance?
Feb 2024
Publication
Hydrogen energy technologies are forecasted to play a critical supporting role in global decarbonisation efforts as reflected by the growth of national hydrogen energy strategies in recent years. Notably the UK government published its Hydrogen Strategy in August 2021 to support decarbonisation targets and energy security ambitions. While establishing techno-economic feasibility for hydrogen energy systems is a prerequisite of the prospective transition social acceptability is also needed to support visions for the ‘hydrogen economy’. However to date societal factors are yet to be embedded into policy prescriptions. Securing social acceptance is especially critical in the context of ‘hydrogen homes’ which entails replacing natural gas boilers and hobs with low-carbon hydrogen appliances. Reflecting the nascency of hydrogen heating and cooking technologies the dynamics of social acceptance are yet to be explored in a comprehensive way. Similarly public perceptions of the hydrogen economy and emerging national strategies remain poorly understood. Given the paucity of conceptual and empirical insights this study develops an integrated acceptance framework and tests its predictive power using partial least squares structural equation modelling. Results highlight the importance of risk perceptions trust dynamics and emotions in shaping consumer perceptions. Foremost prospects for deploying hydrogen homes at scale may rest with coupling renewable-based hydrogen production to local environmental and socio-economic benefits. Policy prescriptions should embed societal factors into the technological pursuit of large-scale sustainable energy solutions to support socially acceptable transition pathways.
Nuclear Enabled Hydrogen CO-generation: Safety and Regulatory Insight
Sep 2023
Publication
National Nuclear Laboratory (NNL) is aiming to demonstrate through a research and development programme that nuclear enabled hydrogen can be used to support future clean energy systems. Demonstrating the safe operation of hydrogen facilities co-generating with a nuclear reactor will be key to enabling the deployment and success of nuclear enabled hydrogen technologies in the future. During the deployment continuity of supply will be paramount and possibly requires inter-seasonal storage. Co-generation is a means of using a source of energy in this case a nuclear reactor to efficiently produce power and thermal energy. Since a great deal of the heat energy is lost to the environment in a power plant making use of wasted energy for other useful output like the production of hydrogen and direct heating would be advantageous to plant economics and energy system flexibility. The civil nuclear industry is regulated around the world. This approach ensures that all the activities related to the production of power from nuclear and the hazards associated with ionising radiation are controlled in a manner which protects workers members of the public property and the environment. Nuclear safety assessments follow a rigorous process and are required as part of the Nuclear Site Licence. A fundamental requirement which is cited in the UK legislation is that the risks associated with all activities at the licensed site be reduced to As Low As Reasonably Practicable (ALARP). The principle places a requirement on duty holders to implement measures to reduce risk where doing so is considered reasonable and proportionate. The inclusion of risks for hazardous materials associated with the hydrogen production facilities need to be considered and this requires harmonisation of two different safety and regulatory governance regimes which have not previously interacted in this way. The safety demonstration for nuclear facilities is provided through the Safety Case.
An Overview of Application-orientated Multifunctional Large-scale Stationary Battery and Hydrogen Hybrid Energy Storage System
Dec 2023
Publication
The imperative to address traditional energy crises and environmental concerns has accelerated the need for energy structure transformation. However the variable nature of renewable energy poses challenges in meeting complex practical energy requirements. To address this issue the construction of a multifunctional large-scale stationary energy storage system is considered an effective solution. This paper critically examines the battery and hydrogen hybrid energy storage systems. Both technologies face limitations hindering them from fully meeting future energy storage needs such as large storage capacity in limited space frequent storage with rapid response and continuous storage without loss. Batteries with their rapid response (90%) excel in frequent short-duration energy storage. However limitations such as a selfdischarge rate (>1%) and capacity loss (~20%) restrict their use for long-duration energy storage. Hydrogen as a potential energy carrier is suitable for large-scale long-duration energy storage due to its high energy density steady state and low loss. Nevertheless it is less efficient for frequent energy storage due to its low storage efficiency (~50%). Ongoing research suggests that a battery and hydrogen hybrid energy storage system could combine the strengths of both technologies to meet the growing demand for large-scale long-duration energy storage. To assess their applied potentials this paper provides a detailed analysis of the research status of both energy storage technologies using proposed key performance indices. Additionally application-oriented future directions and challenges of the battery and hydrogen hybrid energy storage system are outlined from multiple perspectives offering guidance for the development of advanced energy storage systems.
Hydrogen Sampling Systems Adapted to Heavy-duty Refuelling Stations' Current and Future Specifications - A Review
Sep 2024
Publication
To meet the new regulation for the deployment of alternative fuels infrastructure which sets targets for electric recharging and hydrogen refuelling infrastructure by 2025 or 2030 a large infrastructure comprising trucksuitable hydrogen refuelling stations will soon be required. However further standardisation is required to support the uptake of hydrogen for heavy-duty transport for Europe’s green energy future. Hydrogen-powered vehicles require pure hydrogen as some contaminants can reduce the performance of the fuel cell even at very low levels. Even if previous projects have paved the way for the development of the European quality infrastructure for hydrogen conformity assessment sampling systems and methods have yet to be developed for heavy-duty hydrogen refuelling stations (HD-HRS). This study reviews different aspects of the sampling of hydrogen at heavy-duty hydrogen refuelling stations for purity assessment with a focus on the current and future specifications and operations at HD-HRS. This study describes the state-of-the art of sampling systems currently under development for use at HD-HRS and highlights a number of aspects which must be taken into consideration to ensure safe and accurate sampling: risk assessment for the whole sampling exercise selection of cylinders methods to prepare cylinders before the sampling filling pressure and venting of the sampling systems.
Gas Storage in Geological Formations: A Comparative Review on Carbon Dioxide and Hydrogen Storage
Feb 2024
Publication
Carbon dioxide and hydrogen storage in geological formations at Gt scale are two promising strategies toward net-zero carbon emissions. To date investigations into underground hydrogen storage (UHS) remain relatively limited in comparison to the more established knowledge body of underground carbon dioxide storage (UCS). Despite their analogous physical processes can be used for accelerating the advancements in UHS technology the existing distinctions possibly may hinder direct applicability. This review therefore contributes to advancing our fundamental understanding on the key differences between UCS and UHS through multi-scale comparisons. These comparisons encompass key factors influencing underground gas storage including storage media trapping mechanisms and respective fluid properties geochemical and biochemical reactions and injection scenarios. They provide guidance for the conversion of our existing knowledge from UCS to UHS emphasizing the necessity of incorporating these factors relevant to their trapping and loss mechanisms. The article also outlines future directions to address the crucial knowledge gaps identified aiming to enhance the utilisation of geological formations for hydrogen and carbon dioxide storage.
Energy Efficiency of Hydrogen for Vehicle Propulsion: On- or Off-board H2 to Electricity Conversion?
Nov 2024
Publication
If hydrogen fuel is available to support the transportation sector decarbonization its usage can be placed either directly onboard in a fuel cell vehicle or indirectly off-board by using a fuel cell power station to produce electricity to charge a battery electric vehicle. Therefore in this work the direct and indirect conversion scenarios of hydrogen to vehicle propulsion were investigated regarding energy efficiency. Thus in the first scenario hydrogen is the fuel for the onboard electricity production to propel a fuel cell vehicle while in the second hydrogen is the electricity source to charge the battery electric vehicle. When simulated for a drive cycle results have shown that the scenario with the onboard fuel cell consumed about 20% less hydrogen demonstrating higher energy efficiency in terms of driving range. However energy efficiency depends on the outside temperature when heat loss utilization is considered. For outside temperatures of − 5 ◦C or higher the system composed of the battery electric vehicle fueled with electricity from the off-board fuel cell was shown to be more energyefficient. For lower temperatures the system composed of the onboard fuel cell again presented higher total (heat + electricity) efficiency. Therefore the results provide valuable insights into how hydrogen fuel can be used for vehicle propulsion supporting the hydrogen economy development.
A Novel LH2/GH2/Battery Multi-energy Vehicle Supply Station using 100% Local Wind Energy, Technical, Economic and Environmental Perspectives
Feb 2023
Publication
With the gradual maturity of wind power technology China’s wind power generation has grown rapidly over the recent years. However due to the on-site inconsumable electricity the phenomenon of large-scale “wind curtailment” occurs in some areas. In this paper a novel hybrid hydrogen/electricity refueling station is built near a wind farm and a part of the surplus wind power is used to charge electric trucks and the other part of the surplus power is used to produce “green hydrogen”. According to real-time load changes different amounts of liquid hydrogen and gas hydrogen can be properly coordinated to provide timely energy supply for hydrogen trucks. For a 400 MW wind farm in the western Inner Mongolia China the feasibility of the proposed system has been carried out based on the sensitivity and reliability analysis the static and dynamic economic modeling with an entire life cycle analysis. Compared to the conventional technology the initial investment of the proposed scheme (700.07 M$) decreases by 13.97% and the dynamic payback period (10.93 years) decreases by 25.87%. During the life cycle of the proposed system the accumulative NPV reaches 184.63 M$ which increases by 3.14 times compared to the case by conventional wind technology.
Cost Modelling-based Route Applicablity Analysis of United Kingdom Pasenger Railway Decarbonization Options
Jun 2024
Publication
The UK government plans to phase out pure diesel trains by 2040 and fully decarbonize railways by 2050. Hydrogen fuel cell (HFC) trains electrified trains using pantographs (Electrified Trains) and battery electric multiple unit (BEMU) trains are considered the main solutions for decarbonizing railways. However the range of these decarbonization options’ line upgrade cost advantages is unclear. This paper analyzes the upgrade costs of three types of trains on different lines by constructing a cost model and using particle swarm optimization (PSO) including operating costs and fixed investment costs. For the case of decarbonization of the London St. Pancras to Leicester line the electrified train option is more cost-effective than the other two options under the condition that the service period is 30 years. Then the traffic density range in which three new energy trains have cost advantages on different line lengths is calculated. For route distances under 100 km and with a traffic density of less than 52 trips/day BEMU trains have the lowest average cost while electrified trains are the most costeffective in other ranges. For route distances over 100 km the average cost of HFC trains is lower than that of electrified trains at traffic densities below about 45 trips/day. In addition if hydrogen prices fall by 26 % the cost advantage range of HFC trains will increase to 70 trips per day. For route distances under 100 km BEMU trains still maintain their advantages in terms of lower traffic density.
Integration of Renewable Energy Sources in Tandem with Electrolysis: A Technology Review for Green Hydrogen Production
Jun 2024
Publication
The global shift toward sustainable energy solutions emphasises the urgent need to harness renewable sources for green hydrogen production presenting a critical opportunity in the transition to a low-carbon economy. Despite its potential integrating renewable energy with electrolysis to produce green hydrogen faces significant technological and economic challenges particularly in achieving high efficiency and cost-effectiveness at scale. This review systematically examines the latest advancements in electrolysis technologies—alkaline proton exchange membrane electrolysis cell (PEMEC) and solid oxide—and explores innovative grid integration and energy storage solutions that enhance the viability of green hydrogen. The study reveals enhanced performance metrics in electrolysis processes and identifies critical factors that influence the operational efficiency and sustainability of green hydrogen production. Key findings demonstrate the potential for substantial reductions in the cost and energy requirements of hydrogen production by optimising electrolyser design and operation. The insights from this research provide a foundational strategy for scaling up green hydrogen as a sustainable energy carrier contributing to global efforts to reduce greenhouse gas emissions and advance toward carbon neutrality. The integration of these technologies could revolutionise energy systems worldwide aligning with policy frameworks and market dynamics to foster broader adoption of green hydrogen.
A Parametric Study on In-situ Hydrogen Production from Hydrocarbon Reservoirs - Effect of Reservoir and Well Properties
Jul 2024
Publication
Energy transition is a key driver to combat climate change and achieve zero carbon future. Sustainable and costeffective hydrogen production will provide valuable addition to the renewable energy mix and help minimize greenhouse gas emissions. This study investigates the performance of in-situ hydrogen production (IHP) process using a full-field compositional model as a precursor to experimental validation The reservoir model was simulated as one geological unit with a single point uniform porosity value of 0.13 and a five-point connection type between cell to minimize computational cost. Twenty-one hydrogen forming reactions were modelled based on the reservoir fluid composition selected for this study. The thermodynamic and kinetic parameters for the reactions were obtained from published experiments due to the absence of experimental data specific to the reservoir. A total of fifty-four simulation runs were conducted using CMG STARS software for 5478 days and cumulative hydrogen produced for each run was recorded. Results generated were then used to build a proxy model using Box-Behnken design of experiment method and Support Vector Machine with RBF kernel. To ascertain accuracy of the proxy models analysis of variance (ANOVA) was conducted on the variables. The average absolute percentage error between the proxy model and numerical simulation was calculated to be 10.82%. Optimization of the proxy model was performed using genetic algorithm to maximize cumulative hydrogen produced. Based on this optimized model the influence of porosity permeability well location injection rate and injection pressure were studied. Key results from this study reveals that lower permeability and porosity reservoirs supports more hydrogen yield injection pressure had a negligible effect on hydrogen yield and increase in oxygen injection rate corelated strongly with hydrogen production until a threshold value beyond which hydrogen yield decreased. The framework developed in the study could be used as tool to assess candidate reservoirs for in-situ hydrogen production.
Assessing the Potential of Decarbonization Options for Industrial Sectors
Jan 2024
Publication
Industry emits around a quarter of global greenhouse gas (GHG) emissions. This paper presents the first comprehensive review to identify the main decarbonization options for this sector and their abatement potentials. First we identify the important GHG emitting processes and establish a global average baseline for their current emissions intensity and energy use. We then quantify the energy and emissions reduction potential of the most significant abatement options as well as their technology readiness level (TRL). We find that energy-intensive industries have a range of decarbonization technologies available with medium to high TRLs and mature options also exist for decarbonizing low-temperature heat across a wide range of industrial sectors. However electrification and novel process change options to reduce emissions from high-temperature and sector-specific processes have much lower TRLs in comparison. We conclude by highlighting important barriers to the deployment of industrial decarbonization options and identifying future research development and demonstration needs.
OIES Podcast - Key Energy Themes for 2024
Jan 2024
Publication
In this latest OIES podcast James Henderson talks to Bill Farren-Price the new Head of the Gas Programme about some of Key Themes identified by OIES research fellows for 2024. After a review of the outcomes from 2023 we look at the oil and gas markets and discuss a common theme around the contrast between the fundamental tightness in both markets compared with the relative softness of prices. We then move onto a number of energy transition issues starting with some of the key actions from COP28 that need to be implemented in 2024 and following with a review of the outlook for carbon markets hydrogen developments and offshore wind. We also consider the impact of emerging competition between regions over green industrial policy. Finally we consider some of the key geopolitical drivers for 2024 with the influence of China being the most critical. However in an election year for so many countries it will be critical to follow the key policy announcements of the main candidates and of most critically the outcome of the US election in November.
The podcast can be found on their website
The podcast can be found on their website
Technoeconomic, Environmental and Multi-criteria Decision Making Investigations for Optimisation of Off-grid Hybrid Renewable Energy System with Green Hydrogen Production
Jan 2024
Publication
The current study presents a comprehensive investigation of different energy system configurations for a remote village community in India with entirely renewable electricity. Excess electricity generated by the systems has been stored using two types of energy storage options: lithium-ion batteries and green hydrogen production through the electrolysers. The hybrid renewable energy system (HRES) configurations have been sized by minimising the levelised cost of energy (LCOE). In order to identify the best-performing HRES configuration economic and environmental performance indicators has been analysed using the multi-criteria decision-making method (MCDM) TOPSIS. Among the evaluated system configurations system-1 with a photovoltaic panel (PV) size of 310.24 kW a wind turbine (WT) size of 690 kW a biogas generator (BG) size of 100 kW a battery (BAT) size of 174 kWh an electrolyser (ELEC) size of 150 kW a hydrogen tank (HT) size of 120 kg and a converter (CONV) size of 106.24 kW has been found to be the best-performing system since it provides the highest relative closeness (RC) value (∼0.817) and also has the lowest fuel consumption rate of 2.31 kg/kWh. However system-6 shows the highest amount of CO2 (143.97 kg/year) among all the studied system configurations. Furthermore a detailed technical economic and environmental analysis has been conducted on the optimal HRES configuration. The minimum net present cost (NPC) LCOE and cost of hydrogen (COH) for system 1 has been estimated to be $1960584 $0.44/kWh and $22.3/kg respectively.
Hydrogen Import and Export: Unlocking the UK's Hydrogen Trade Potential
May 2024
Publication
Hydrogen trade is an emerging area of interest for hydrogen developers end-users traders and governments around the world. It can enhance system flexibility energy security and clean growth enabling decarbonisation at a lower cost and faster pace. Thanks to its competitive advantage in existing ports terminals and interconnectors the UK is well placed to be the European trade hub for hydrogen and its carriers. With its access to world leading offshore wind generation capacity and geological storage the UK will almost certainly be a net exporter of hydrogen in the future delivering economic value and creating jobs. However hydrogen trade will not be a one-way process. In order to best position the UK as a future hydrogen trade hub there could be value in investing in small scale hydrogen imports and exports to ‘wet the pipes’ and stimulate investment in infrastructure. Imports could also enhance our energy security as a part of a diverse energy mix and support demand whilst domestic production gets up to speed. Both imports and exports will be key to build supply chains and skills and enhance clean growth. With major European economies having established their hydrogen trade strategy there is growing uncertainty as to how the United Kingdom will capitalise on its competitive advantage and position itself in the global hydrogen market. This is the first qualitative report released by Hydrogen UK’s Import and Export Taskforce. This report aims to provide a high-level overview of Hydrogen UK’s vision and recommendations with subsequent reports exploring this topic in further detail.
This report can be found on Hydrogen UK's website.
This report can be found on Hydrogen UK's website.
The Cost of Clean Hydrogen from Offshore Wind and Electrolysis
Feb 2024
Publication
The decarbonization of industry heating and transportation is a major challenge for many countries’ energy transition. Hydrogen is a direct low-carbon fuel alternative to natural gas offering a higher flexibility in the range of possible applications yet currently most hydrogen is produced using carbonintensive steam methane reforming due to cost considerations. Therefore this study explores the economics of a prominent low-carbon method of hydrogen production comparing the cost of hydrogen generation from offshore wind farms with and without grid electricity imports to conventional hydrogen production methods. A novel techno-economic model for offshore electrolysis production costs is presented which makes hydrogen production fully dispatchable leveraging geological salt-cavern storage. This model determines the lifetime costs aportioned across the system components as well as the Levelized Cost of Hydrogen (LCOH). Using the United Kingdom as a case study LCOH from offshore wind power is calculated to be €8.68 /kgH2 using alkaline electrolysis (AEL) €10.49 /kgH2 using proton exchange membrane electrolysis (PEMEL) and €10.88 /kgH2 with grid electricity to backup the offshore wind power. A stochastic Monte-Carlo model is used to asses the uncertainty on costs and identify the cost of capital electrolyser and wind farm capital costs and cost of electricity as the most important drivers of LCOH across the different scenarios. Reducing the capital cost to comparative levels observed on today’s wind farms alone could see AEL LCOH fall to €5.32 /kgH2 near competitive with conventional generation methods.
CFD Simulations of Hydrogen Tank Fuelling: Sensitivity to Turbulence Model and Grid Resolution
Dec 2023
Publication
CFD modelling of compressed hydrogen fuelling provides information on the hydrogen and tank structure temperature dynamics required for onboard storage tank design and fuelling protocol development. This study compares five turbulence models to develop a strategy for costeffective CFD simulations of hydrogen fuelling while maintaining a simulation accuracy acceptable for engineering analysis: RANS models k-ε and RSM; hybrid models SAS and DES; and LES model. Simulations were validated against the fuelling experiment of a Type IV 29 L tank available in the literature. For RANS with wall functions and blended models with near-wall treatment the simulated average hydrogen temperatures deviated from the experiment by 1–3% with CFL ≈ 1–3 and dimensionless wall distance y + ≈ 50–500 in the tank. To provide a similar simulation accuracy the LES modelling approach with near-wall treatment requires mesh with wall distance y + ≈ 2–10 and demonstrates the best-resolved flow field with larger velocity and temperature gradients. LES simulation on this mesh however implies a ca. 60 times longer CPU time compared to the RANS modelling approach and 9 times longer compared to the hybrid models due to the time step limit enforced by the CFL ≈ 1.0 criteria. In all cases the simulated pressure histories and inlet mass flow rates have a difference within 1% while the average heat fluxes and maximum hydrogen temperature show a difference within 10%. Compared to LES the k-ε model tends to underestimate and DES tends to overestimate the temperature gradient inside the tank. The results of RSM and SAS are close to those of LES albeit of 8–9 times faster simulations.
Flame Acceleration, Detonation Limit and Heat Loss for Hydrogen-Oxygen Mixture at Cryogenic Temperature of 77 K
Sep 2023
Publication
Experiments are performed in hydrogen-oxygen mixtures at the cryogenic temperature of 77 K with the equivalence ratio of 1.5 and 2.0. The optical fibers pressure sensors and the smoked foils are used to record the flame velocity overpressure evolution curve and detonation cells respectively. The 1st and 2nd shock waves are captured and they finally merge to form a stronger precursor shock wave prior to the onset of detonation. The cryogenic temperature will cause the larger expansion ratio which results in the occurrence of strong flame acceleration. The stuttering mode the galloping mode and the deflagration mode are observed when the initial pressure decreases from 0.50 atm to 0.20 atm with the equivalence ratio of 1.5 and the detonation limit is within 0.25-0.30 atm. The heat loss effect on the detonation limit is analysed. In addition the regularity of detonation cell is investigated and the larger post-shock specific heat ratio !"" and the lower normalized activation energy # at lower initial pressure will cause the more regular detonation cell. Also the detonation cell width is predicted by a model of = ($) ⋅ Δ# and the prediction results are mainly consistent with the experimental results.
No more items...