Compressed hydrogen stored at cryogenic temperatures has a much higher density than room-temperature storage, which enables large-scale hydrogen storage and transport. An understanding of the release of cryogenic hydrogen from pressurized vessels is needed to evaluate the risk and safety concerns with the use of this fuel. The present work extends the analysis of previous experimental studies that measured the gas concentrations of cryo-compressed hydrogen jets and methane jets using a laser Raman scattering diagnostic system. Since the Raman signals are very small, a denoising algorithm was applied to significantly reduce the noise to enable statistical analysis of the data. The transient features of the turbulent jets were characterized by their concentration intermittencies and probability density functions (PDFs). A two-part PDF was developed to predict the bimodal features of the jet concentration distributions. Then, the flammability factors of the cryogenic jets were calculated based on the intermittency and the PDF.

Safety is a key element of today’s large-scale energy infrastructure and especially important for new energy technologies, such as hydrogen. As with any fuel, the attractive features of hydrogen energy technologies come with safety hazards. The diverse nature of hydrogen applications spanning production, delivery, storage, and end-use combined with the unique characteristics of hydrogen requires management of a varied safety landscape. In this chapter, we focus on large-scale infrastructure and the associated safety hazards of emerging hydrogen technologies. A brief introduction to hydrogen technologies is provided, including hydrogen production, delivery, storage, and end uses such as transportation, power and heating, and manufacturing. Hydrogen-safety research topics are then discussed with emphasis on (i) hydrogen behavior, (ii) hydrogen compatibility of materials, and (iii) quantitative risk assessment. A brief perspective on international codes and standards is also provided. Knowledge of hydrogen behavior provides a scientific foundation for hydrogen safety codes; research and key characteristics of dispersion of flammable concentrations, flame characteristics, and ignition parameters are discussed. Hydrogen compatibility of materials depends on materials, environmental and the mechanics (e.g., stresses) variables. Important trends of these variables are discussed in the context of managing structural integrity of hydrogen infrastructure. An overview of the various safety risk calculation methodologies used for quantitative risk assessment of hydrogen systems are also presented and discussed. The unique attributes of hydrogen behavior and its interaction with materials must be considered in evaluating and managing the risks of emerging hydrogen energy technologies. Scientific understanding provides the foundation for effective management of hydrogen safety, thus enabling deployment of transformational hydrogen energy solutions.

Underexpanded, cryogenic hydrogen and methane jets were measured using laser Raman scattering diagnostic. The jets were released from 1 mm to 1.25 mm orifices for the stag-nation pressure ranges of 2-6 bar and temperature ranges of 37-46 K (hydrogen) and 112-189 K (methane). Raman signals are inherently small, thus a denoising algorithm was developed to substantially reduce the noise hindering the statistical analysis of the data. The time-averaged concentration and temperature data were plotted to show a hyperbolic decay law along the jet centerline and a Gaussian distribution in the radial direction. The concentration fluctuations of the cryogenic jets are similar to those of warm jets, the centerline RMS mass fraction decays similarly to the mean mass fraction, and the highest radial concentration fluctuations appear in the shear layer. Thus, the self-similar charac-teristics of the cryogenic jets are comparable with room-temperature jets for the present test conditions.(c) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Previous research has provided strong evidence that CO2 and H2O gasification reactions can provide non-negligible contributions to the consumption rates of pulverized coal (pc) char during combustion, particularly in oxy-fuel environments. Fully quantifying the contribution of these gasification reactions has proven to be difficult, due to the dearth of knowledge of gasification rates at the elevated particle temperatures associated with typical pc char combustion processes, as well as the complex interaction of oxidation and gasification reactions. Gasification reactions tend to become more important at higher char particle temperatures (because of their high activation energy) and they tend to reduce pc oxidation due to their endothermicity (i.e. cooling effect). The work reported here attempts to quantify the influence of the gasification reaction of CO2 in a rigorous manner by combining experimental measurements of the particle temperatures and consumption rates of size-classified pc char particles in tailored oxy-fuel environments with simulations from a detailed reacting porous particle model. The results demonstrate that a specific gasification reaction rate relative to the oxidation rate (within an accuracy of approximately +/- 20% of the pre-exponential value), is consistent with the experimentally measured char particle temperatures and burnout rates in oxy-fuel combustion environments. Conversely, the results also show, in agreement with past calculations, that it is extremely difficult to construct a set of kinetics that does not substantially overpredict particle temperature increase in strongly oxygen-enriched N2 environments. This latter result is believed to result from deficiencies in standard oxidation mechanisms that fail to account for falloff in char oxidation rates at high temperatures.

We investigate the potential of liquid hydrogen storage (LH2) on-board Class-8 heavy duty trucks to resolve many of the range, weight, volume, refueling time and cost issues asso-ciated with 350 or 700-bar compressed H2 storage in Type-3 or Type-4 composite tanks. We present and discuss conceptual storage system configurations capable of supplying H2 to fuel cells at 5-bar with or without on-board LH2 pumps. Structural aspects of storing LH2 in double walled, vacuum insulated, and low-pressure Type-1 tanks are investigated. Struc-tural materials and insulation methods are discussed for service at cryogenic temperatures and mitigation of heat leak to prevent LH2 boil-off. Failure modes of the liner and shell are identified and analyzed using the regulatory codes and detailed finite element (FE) methods. The conceptual systems are subjected to a failure modes and effects analysis (FMEA) and a safety, codes, and standards (SCS) review to rank failures and identify safety gaps. The results indicate that the conceptual systems can reach 19.6% useable gravimetric capacity, 40.9 g-H2/L useable volumetric capacity and $174-183/kg-H2 cost (2016 USD) when manufactured 100,000 systems annually.(c) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

In order to better understand the complex pooling and vaporization of a liquid hydrogen spill, Sandia National Laboratories is conducting a highly instrumented, controlled experiment inside their Shock Tube Facility. Simulations were run before the experiment to help with the planning of experimental conditions, including sensor placement and cross wind velocity. This paper describes the modeling used in this planning process and its main conclusions. Sierra Suite’s Fuego, an in-house computational fluid dynamics code, was used to simulate a RANS model of a liquid hydrogen spill with five crosswind velocities: 0.45, 0.89, 1.34, 1.79, and 2.24 m/s. Two pool sizes were considered: a diameter of 0.85 m and a diameter of 1.7. A grid resolution study was completed on the smaller pool size with a 1.34 m/s crosswind. A comparison of the length and height of the plume of flammable hydrogen vaporizing from the pool shows that the plume becomes longer and remains closer to the ground with increasing wind speed. The plume reaches the top of the facility only in the 0.45 m/s case. From these results, we concluded that it will be best for the spacing and location of the concentration sensors to be reconfigured for each wind speed during the experiment.