Cryogenic Hydrogen Research Articles

Cryogenic hydrogen fuel for controlled inertial confinement fusion (formation of reactor-scale cryogenic targets)

In inertial fusion energy research, considerable attention has recently been focused on low-cost fabrication of a large number of targets by developing a specialized layering module of repeatable operation. The targets must be free-standing, or unmounted. Therefore, the development of a target factory for inertial confinement fusion (ICF) is based on methods that can ensure a cost-effective target production with high repeatability. Minimization of the amount of tritium (i.e., minimization of time and space at all production stages) is a necessary condition as well. Additionally, the cryogenic hydrogen fuel inside the targets must have a structure (ultrafine layers—the grain size should be scaled back to the nanometer range) that supports the fuel layer survivability under target injection and transport through the reactor chamber. To meet the above requirements, significant progress has been made at the Lebedev Physical Institute (LPI) in the technology developed on the basis of rapid fuel layering inside moving free-standing targets (FST), also referred to as the FST layering method. Owing to the research carried out at LPI, unique experience has been gained in the development of the FST-layering module for target fabrication with an ultrafine fuel layer, including a reactor- scale target design. This experience can be used for the development of the next-generation FST-layering module for construction of a prototype of a target factory for power laser facilities and inertial fusion power plants.

Injection barrel with a tapered structure for a low speed and small size cryogenic hydrogen pellet in medium-sized plasma fusion devices.

An injection barrel was designed and fabricated for a small size 0.8 mm cryogenic pellet with a low speed of 200-300 m/s in medium-sized plasma fusion devices. Pellet injection with pneumatic acceleration was examined using a conventional in situ technique. A tapered structure was applied in the downstream side of the injection barrel to satisfy the requirement of pellet speed reduction by expansion of the propellant gas. Shadowgraph and light gate measurements show that the intact pellets have speeds of 260 ± 30 m/s and a typical size of 1.1-1.2 mm. The pellet ablation code based on a neutral gas shielding model shows that the penetration depth of the measured pellet parameters does not cross the plasma center, even in medium-sized plasma devices such as the Heliotron J helical device. The injection barrel with a tapered structure developed in this study is feasible for low speed pellet injection.

Release and dispersion modeling of cryogenic under-expanded hydrogen jets

In the present work performed within the framework of the SUSANA EC-project, we address the release and dispersion modeling of hydrogen stored at cryogenic temperatures and high pressures. Due to the high storage pressures the resulting jets are under-expanded. Due to the low temperatures the choked conditions can be two-phase. For the release modeling the homogeneous equilibrium model (HEM) was used combined with NIST equation of state for hydrogen. For the dispersion modeling the 3d CFD methodology was used combined with a) a notional nozzle approach to bridge the expansion to atmospheric pressure region that exists near the nozzle, b) the ideal gas assumption for hydrogen and air and c) the standard (buoyancy included) k–ε turbulence model. Predicted release choked mass fluxes are compared against 37 experiments from literature. Predicted steady state hydrogen concentrations along the jet axis are compared against five dispersion experiments from literature as well as the Chen and Rodi correlation and the behavior of the proposed release and dispersion modeling approaches is assessed.

Efficient synthesis for large-scale production and characterization for hydrogen storage of ligand exchanged MOF-74/174/184-M (M = Mg2+, Ni2+)

A semitechnical route (optimized by BASF SE) to synthesize MOF-74/174-M (M = Mg2+, Ni2+) efficiently in ton-scale production is presented with the goal of mobile and stationary gas storage applications especially for hydrogen as future energy carrier. In addition, a new member of these series of materials, MOF-184-M (M = Mg2+, Ni2+) is introduced using ligand exchange strategy in order to produce a more porous analogue (possessing large aperture) without loss of crystallinity. This family comprising MOF-74/174/184 are characterized systematically for hydrogen adsorption properties by volumetric measurements with a Sieverts’ apparatus. Replacing the linker by a longer one results in an increase of the BET area from 984 to 3154 m2/g and an enhancement of the excess cryogenic (77 K) hydrogen storage capacity from 1.8 to 4.7 wt%. The heat of adsorption of linker exchanged MOF-174/184 (as a function of uptake) shows similar values to the parent MOF-74, indicating successful construction of expanded MOFs in large scale production. Finally, a usable capacity of these MOFs is investigated for mobile application, revealing that the increasing surface area without strong binding metal sites through longer linker exchange is one of important parameters for improving usable capacity.

Ignition and flame characteristics of cryogenic hydrogen releases

In this work, under-expanded cryogenic hydrogen jets were investigated experimentally for their ignition and flame characteristics. The test facility described herein, was designed and constructed to release hydrogen at a constant temperature and pressure, to study the dispersion and thermo-physical properties of cryogenic hydrogen releases and flames. In this study, a non-intrusive laser spark focused on the jet axis was used to measure the maximum ignition distance. The radiative power emitted by the corresponding jet flames was also measured for a range of release scenarios from 37 K to 295 K, 2–6 barabs through nozzles with diameters from 0.75 to 1.25 mm. The maximum ignition distance scales linearly with the effective jet diameter (which scales as the square root of the stagnant fluid density). A 1-dimensional (stream-wise) cryogenic hydrogen release model developed previously at Sandia National Laboratories (although this model is not yet validated for cryogenic hydrogen) was exercised to predict that the mean mole fraction at the maximum ignition distance is approximately 0.14, and is not dependent on the release conditions. The flame length and width were extracted from visible and infra-red flame images for several test cases. The flame length and width both scale as the square root of jet exit Reynolds number, as reported in the literature for flames from atmospheric temperature hydrogen. As shown in previous studies for ignited atmospheric temperature hydrogen, the radiative power from the jet flames of cold hydrogen scales as a logarithmic function of the global flame residence time. The radiative heat flux from jet flames of cold hydrogen is higher than the jet flames of atmospheric temperature hydrogen, for a given mass flow rate, due to the lower choked flow velocity of low-temperature hydrogen. This study provides critical information with regard to the development of models to inform the safety codes and standards of hydrogen infrastructure.

Method of the phonon modulation of cryogenic hydrogen fuel structure in ITF targets

The possibility of spatial homogenization of the cryogenic hydrogen fuel structure in laser thermonuclear targets is considered. The results of a large cycle of experimental studies on low-temperature (T = 4.2 K) phonon modulation of the structure of solid hydrogen layers with various ortho-para compositions and its effect on the homogenization process rate are presented.

Combined energy production and waste management in manned spacecraft utilizing on-demand hydrogen production and fuel cells

Energy supply and waste management are among the most significant challenges in human spacecraft. Great efforts are invested in managing solid waste, recycling grey water and urine, cleaning the atmosphere, removing CO2, generating and saving energy, and making further use of components and products. This paper describes and investigates a concept for managing waste water and urine to simultaneously produce electric and heat energies as well as fresh water. It utilizes an original technique for aluminum activation to react spontaneously with water at room temperature to produce hydrogen on-site and on-demand. This reaction has further been proven to be effective also when using waste water and urine. Applying the hydrogen produced in a fuel cell, one obtains electric energy as well as fresh (drinking) water. The method was compared to the traditional energy production technology of the Space Shuttle, which is based on storing the fuel cell reactants, hydrogen and oxygen, in cryogenic tanks. It is shown that the alternative concept presented here may provide improved safety, compactness (reduction of more than one half of the volume of the hydrogen storage system), and management of waste liquids for energy generation and drinking water production. Nevertheless, it adds mass compared to the cryogenic hydrogen technology. It is concluded that the proposed method may be used as an emergency and backup power system as well as an additional hydrogen source for extended missions in human spacecraft.

Development of a cryogenic hydrogen microjet for high-intensity, high-repetition rate experiments.

The advent of high-intensity, high-repetition-rate lasers has led to the need for replenishing targets of interest for high energy density sciences. We describe the design and characterization of a cryogenic microjet source, which can deliver a continuous stream of liquid hydrogen with a diameter of a few microns. The jet has been imaged at 1 μm resolution by shadowgraphy with a short pulse laser. The pointing stability has been measured at well below a mrad, for a stable free-standing filament of solid-density hydrogen.

High resolution x-ray Thomson scattering measurements from cryogenic hydrogen jets using the linac coherent light source.

We present the first spectrally resolved measurements of x-rays scattered from cryogenic hydrogen jets in the single photon counting limit. The 120 Hz capabilities of the LCLS, together with a novel hydrogen jet design [J. B. Kim et al., Rev. Sci. Instrum. (these proceedings)], allow for the ability to record a near background free spectrum. Such high-dynamic-range x-ray scattering measurements enable a platform to study ultra-fast, laser-driven, heating dynamics of hydrogen plasmas. This measurement has been achieved using two highly annealed pyrolytic graphite crystal spectrometers to spectrally resolve 5.5 keV x-rays elastically and inelastically scattered from cryogenic hydrogen and focused on Cornell-SLAC pixel array detectors [S. Herrmann et al., Nucl. Instrum. Methods Phys. Res., Sect. A 718, 550 (2013)].

Demonstration of a single-crystal reflector-filter for enhancing slow neutron beams

The cold polycrystalline beryllium reflector-filter concept has been used to enhance the cold neutron emission of cryogenic hydrogen moderators, while suppressing the intermediate wavelength and fast neutron emission at the same time. While suppressing the fast neutron emission is often desired, the suppression of intermediate wavelength neutrons is often unwelcome. It has been hypothesized that replacing the polycrystalline reflector-filter concept with a single-crystal reflector-filter concept would overcome the suppression of intermediate wavelength neutrons and thereby extend the usability of the reflector-filter concept to shorter but still important wavelengths. In this paper we present the first experimental data on a single-crystal reflector-filter at a reflected neutron source and compare experimental results with hypothesized performance. We find that a single-crystal reflector-filter retains the long-wavelength benefit of the polycrystalline reflector-filter, without suffering the same loss of important intermediate wavelength neutrons. This finding extends the applicability of the reflector-filter concept to intermediate wavelengths, and furthermore indicates that the reflector-filter benefits arise from its interaction with fast (background) neutrons, not with intermediate wavelength neutrons of potential interest in many types of neutron scattering.

Cryogenic adsorption hydrogen storage with enhanced heat distribution – An in-depth investigation

A numerical model for a cryogenic adsorption hydrogen storage with enhanced heat distribution structure is presented and validated by experiments. The investigations cover charging, discharging and dormancy at cryogenic conditions. Metal foam was implemented as heat distribution enhancement structure. The prediction of the effective thermal conductivity, keff_foam, over the entire storage working range was carried out using an experimentally validated unit cell approach. An increase of keff_foam by +33% was observed by lowering the temperature from 295 K to 77 K, given keff_foam = 4.87 W/(m·K). The novel 2D axis-symmetric storage model developed applies two energy equations, one for the storage bed and one for the foam. Further, important thermal effects such as hydrogen isomer conversion were considered in the model. The storage model predictions were within the measurement uncertainties. A 95% storage filling was measured after 300 s charging. The enhanced heat transfer in the storage allowed highly transient charging. The volumetric and gravimetric storage capacity increased after 300 s charging by 21.5% and 9.3%, respectively. This behavior compensated for the volume and mass penalties for the implemented foam structure. However, further storage material improvements and a storage optimized heat distribution structure, including cooling fluid piping, are foreseen to meet overall storage requirements.

A risk matrix analysis method based on potential risk influence: A case study on cryogenic liquid hydrogen filling system

A risk matrix analysis framework is proposed for risk assessment and prioritization based on potential risk influence (PRI). First, a new principle for risk level assignment considers the potential impacts of risk, including controllability, criticality, manageability and uncertainty, is established. Next, the impacts of potential risk are divided into two risk influence factors in risk matrix: probability and consequence influence factor. A fuzzy probability method is used to calculate the failure probability of basic events when appropriate reliability data is unavailable. To take the dependence of basic events into account, Bayesian belief network models established to calculate the likelihood of failure. Finally, to demonstrate the validity of the proposed method, a risk assessment and a risk ranking process are performed for a cryogenic liquid hydrogen filling system (CLHFS). The results of the case study confirmed that the proposed methodology successfully manages risk level inconsistency, and is altogether a feasible and reasonable tool for risk management.

Fabrication and characterization of thin polymer targets for laser-driven ion acceleration

Polymer foils with thicknesses 150 nm to around 1 µm were manufactured using the process of spincoating. Varying the concentration of the polymer solution was found to be the most efficient way to control resulting foil thickness. Both interferometric microscopy and energy loss of alpha particles were used for characterization and found to yield agreeing results. For an experiment on laser-driven ion acceleration, these films were used as targets and as substrates for cryogenic hydrogen targets.

In-situ formation of solidified hydrogen thin-membrane targets using a pulse tube cryocooler

An account is given of the Central Laser Facility's work to produce a cryogenic hydrogen targetry system using a pulse tube cryocooler. Due to the increasing demand for low Z thin laser targets, CLF (in collaboration with TUD) have been developing a system which allows the production of solid hydrogen membranes by engineering a design which can achieve this remotely; enabling the gas injection, condensation and solidification of hydrogen without compromising the vacuum of the target chamber. A dynamic sealing mechanism was integrated which allows targets to be grown and then remotely exposed to open vacuum for laser interaction. Further research was conducted on the survivability of the cryogenic targets which concluded that a warm gas effect causes temperature spiking when exposing the solidified hydrogen to the outer vacuum. This effect was shown to be mitigated by improving the pumping capacity of the environment and reducing the minimum temperature obtainable on the target mount. This was achieved by developing a two-stage radiation shield encased with superinsulating blanketing; reducing the base temperature from 14 ± 0.5 K to 7.2 ± 0.2 K about the coldhead as well as improving temperature control stability following the installation of a high-performance temperature controller and sensor apparatus. The system was delivered experimentally and in July 2014 the first laser shots were taken upon hydrogen targets in the Vulcan TAP facility.

CFD study on Taconis thermoacoustic oscillation with cryogenic hydrogen as working gas

Taconis oscillation is a kind of typical self-excited thermoacoustic oscillation, the study of which is of great significance to reveal the thermoacoustic conversion effect and find ways to suppress self-excited oscillation in cryogenic systems. Based on computational fluid dynamics (CFD) method, the onset process of Taconis oscillation with low temperature hydrogen at atmospheric pressure as working gas is first simulated. It is shown that a standing-wave acoustic field operating at 91Hz starts spontaneously and finally develops to a saturation state in the Taconis tube with length and inner diameter of 1m and 0.01m respectively. Parametric variations in both axial and radial directions of thermoacoustic field are then studied in detail. By combining the computational results with Rott’s theory, the spatial distributions of viscous dissipation, thermal relaxation dissipation, and source/sink terms of Taconis thermoacoustic oscillation are obtained quantitatively. The dissipation and source terms are found to be mainly brought forth by the traveling-wave and standing-wave components of the acoustic field, respectively.

Experimental and numerical investigation of the cryogenic hydrogen storage processes over MOF-5

The processes of hydrogen charging to and discharging from a 3-L cryogenic tank have been studied experimentally and numerically. This study investigated the impacts of factors such as mass flow rate, outlet opening time, bed density, and heating power on the hydrogen charging and discharging processes. For charging, it was found that the flow-through cooling technique could remove the adsorption heat in the process, but some issues such as channeling phenomenon and large thermal mass of the system need to be addressed. Low initial bed temperature is beneficial for hydrogen storage in terms of the efficiency of charging operation. When the bed density of metal organic framework-5 (MOF-5) is increased from 164 kg/m3 to 174 kg/m3, the total storage of hydrogen within the tank increases accordingly. It is found that pressure is the major factor that determines the storage of hydrogen, which increases significantly with the pressure within the tank. For discharging, high pressure in the storage tank can be used to release hydrogen for a certain period of time without heating. However, in order to maintain the desired hydrogen discharge rate, a heat source is eventually needed. This heat must be supplied in order to desorb the additional hydrogen from the system. To deal with the channeling phenomenon in the charging process, cyclic charging was tested and adopted.

Thermal performance of foam/MLI for cryogenic liquid hydrogen tank during the ascent and on orbit period

This paper developed one quasi-steady state model to investigate the thermal performances of foam and MLI for a cryogenic liquid hydrogen tank during the ascent and on-orbit process. The corresponding parameters of MLI were calculated with temperature range from 55 K to 700 K, and pressure range between 10−6 Pa and 105 Pa during the whole process. Changes of physical properties with the flight height or the flight cycle were fully considered. The present developed model was validated by the experimental results and turned out to have high prediction ability. Iterated from outside to inside of the MLI layer with the dichotomy method, three main heat transfer forms were specially investigated and compared. Thermal resistance distributions of foam and MLI were compared in detail, and their contributions to reduce the heat leakage were analyzed thoroughly. Some valuable conclusions were of significance to optimize the design of foam/MLI for cryogenic storage tanks.

Modeling of cryo-adsorption of hydrogen on MOF-5 pellets: Effect of pellet properties on moderate pressure refueling

Refueling of a single MOF-5 pellet with cryogenic hydrogen at moderate pressures is modeled in this work. A MOF-5 pellet in a discharged state is placed in a hydrogen atmosphere at refueling conditions of 80 K temperature and 30 bar pressure. The absolute adsorption isotherm for hydrogen on MOF-5 is described by the Unilan model, hydrogen is modeled as a real gas, and properties of the compressed MOF-5 pellet are obtained from polynomial fits to low temperature experimental data. Pellet properties change due to the addition of expanded natural graphite (ENG) and various levels of compaction. A parametric study is performed using COMSOL® Multiphysics 4.2 to understand the effect of ENG and pellet compaction on refueling behavior of a single pellet. Specifically, the role of permeability and thermal conductivity, and the effect of anisotropic thermal conductivity are investigated using a two-dimensional axisymmetric model. The variation in pellet refueling time with varying pellet sizes is studied in order to determine the “optimal” pellet size for fast refueling. Results show that both stick-like geometry (h/d≫1) and flat hockey-puck geometry (h/d≪1) provide fast refueling. Conversely, pellets with h/d≈0.5 show the longest refueling times and are therefore not recommended for use in a packed bed design.

Measurements and modelling of wall heat fluxes in rocket combustion chamber with porous injector head

A rocket combustion chamber with a porous injector head, which is a new concept for injecting propellants, is tested. The hot-fire tests are carried out using cryogenic oxygen and hydrogen at the mass ratio of oxidizer to fuel of 6 and at pressure of 80 bar. Pressures, wall temperatures, and wall heat fluxes are measured along the axis of the chamber. The wall heat fluxes are determined by the calorimetric method. The wall heat flux has a maximum at a distance of 50–100 mm from the injector plate. To interpret the experimental results, numerical simulations are performed using the commercial CFD code ANSYS CFX. The turbulent flow is modelled by the Favre-averaged Navier–Stokes equations and the shear-stress transport model. The turbulent combustion is modelled using two different models: the extended eddy-dissipation model and the extended coherent flame model. Results obtained with the different models are compared both with experimental data and with each other. The numerical results agree with the experimental data. The extended eddy-dissipation model gives the very good agreement which is achieved by applying additional parameters (‘Flame Temperature’ and ‘Extinction Temperature’) dependent on the mixture fraction.

Pressure and temperature fluctuation simulation of J-PARC cryogenic hydrogen system

The J-PARC cryogenic hydrogen system provides supercritical cryogenic hydrogen to the moderators at a pressure of 1.5 MPa and temperature of 18 K and removes 3.8 kW of nuclear heat from the 1 MW proton beam operation. We prepared a heater for thermal compensation and an accumulator, with a bellows structure for volume control, to mitigate the pressure fluctuation caused by switching the proton beam on and off. In this study, a 1-D simulation code named DiSC-SH2 was developed to understand the propagation of pressure and temperature propagations through the hydrogen loop due to on and off switching of the proton beam. We confirmed that the simulated dynamic behaviors in the hydrogen loop for 300-kW and 500-kW proton beam operations agree well with the experimental data under the same conditions.