France

A set of original experiments is presented covering the topic of hydrogen-air mixture ignition by a hot surface. The hot surface is a 30 mm long/10 mm diameter heated coil which temperature is controlled by IR techniques. The coil is placed into the flowing stream of hydrogen air mixtures. The variable parameters are the composition of the flammable atmosphere (4 to 75% H2 v/v) the flow speed (from 0.5 m/s to 30 m/s) and its temperature (from -110°C to ambient). The experimental techniques and results are presented and a tentative interpretation is proposed based on ignition theories and highspeed video recordings. It is shown that the ignition temperature (600°C) is insensitive to flowing conditions which is a very unexpected result.

Hydrogen transport and trapping equations are implemented in a FE software using User Subroutines and the obtained tool is applied to get the diffusion fields in a metallic sheet submitted to a U-Bend test. Based on a submodelling process mechanical and diffusion fields have been computed at the polycrystal scale from which statistical evaluation of the risk of failure of the sample has been estimated.

In the event of a fire composite pressure vessels behave very differently from metallic ones: the material is degraded potentially leading to a burst without significant pressure increase. Hence such objects are when necessary protected from fire by using thermally-activated devices (TPRD) and standards require testing cylinder and TPRD together. The pre-normative research project FireComp aimed at understanding better the conditions which may lead to burst through testing and simulation and proposed an alternative way of assessing the fire performance of composite cylinders. This approach is currently used by Air Liquide for the safety of composite bundles carrying large amounts of hydrogen gas.

Some illustrations of the use of deuterium or tritium for isotopic tracing of hydrogen absorption transport and trapping in nuclear materials are presented. Isotopic tracing of hydrogen has been shown to be successful for the determination of the boundaries conditions for hydrogen desorption or absorption in a material exposed to a hydrogen source. Also the unique capabilities of isotopic tracing and related techniques to characterize H interactions with point defects and dislocations acting as moving traps has been demonstrated. Such transport mechanisms are considered to play a major role in some stress corrosion cracking and hydrogen embrittlement mechanisms.

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The EU’s hydrogen strategy consists of studying the potential for renewable hydrogen to help decarbonize the EU in a cost-effective way. Today hydrogen accounts for less than 2% of Europe’s energy consumption. It is primarily used to produce chemical products. However 96% of this hydrogen production is through natural gas leading to significant amounts of CO2 emissions. In this paper we investigated PV electrolysis H2 gas (noted H2(g)) production for mapping this resource at Europe’s scale. The Cordex/Copernicus RCPs scenarios allow for evaluating the impact of climate changes on the H2 -produced mass and the equivalent energy according to both extreme RCPs scenarios. New linear regressions are investigated to study the great dependence in H2(g) produced masses (kg·yr−1 ) and equivalent energies (MWh·yr−1 ) for European countries. Computational scenarios are investigated from a reference year (2005) to the end of the century (2100) by steps of 5 years. According to RCPs 2.6 (favorable)/8.5 (extreme) 31.7% and 77.4% of Europe’s area presents a decrease of H2(g)-produced masses between 2005 and 2100. For the unfavorable scenario (8.5) only a few regions located in the northeast of France Germany Austria Romania Bulgaria and Greece present a positive balance in H2(g) production for supplying remote houses or smart grids in electricity and heat energy.

Fueling and defueling of hydrogen composite tanks is an important issue for the safe handling of hydrogen. To prevent temperature rise during refuelling (maximum allowed T=+85°C) the rate of fueling must be carefully controlled. Using Computational Fluid Dynamics (CFD) we simulate the temperature and velocity distribution inside the tank during these processes including cases where thermal stratification occurs. Simulations of two tank configurations with tilted injectors are presented along with experimental data validation. A model is proposed to account for the thermal inertia of the thermocouples making it possible to compare more reliably CFD results with experimental measurements.

The goals of the long-term tests were to see the impact of blends of hydrogen and natural gas on the technical condition of the appliances and their performance after several hours of operation. To do so they were run through an accelerated test program amounting to more than 3000 testing hours for the boilers and more than 2500 testing hours for the cookers. The percentage of hydrogen in the test gas was 30% by volume. Three boilers and two cookers were tested by DGC and two boilers by GWI. This report describes the test protocol the results and analysis on the seven appliances tested.

This paper addresses the topic of the conceptual design of a regional aircraft with hybrid electric propulsion based on hydrogen fuel cells. It aims at providing an optimization-based method to design a hybrid propulsive system comprising two power sources (jet fuel and hydrogen) for the generation of the required propulsive power and at studying the impact of fuel cell technologies on the aircraft performances. Indeed by performing optimizations for two hybrid propulsive systems using either low temperature or high temperature Proton-exchange membrane fuel cells this study provides a preliminary assessment of the impact of the fuel cell operating temperature on the system design and the overall aircraft performance. First this paper gives a description of the baseline turboprop regional aircraft with a focus on its high speed and low speed flight performances which will serve as requirements for the design of the hybrid aircraft. Then the hybrid electric architecture and the sizing models of the propulsion system are presented. Finally optimizations are performed to design two parallel hybrid propulsive systems based on different fuel cells technologies and aimed at minimizing the block fuel per passenger over a mission of 200 nm. Results show how the proposed methodology and models lead to design two propulsive systems capable of reducing the fuel consumption per passenger by more than 30% compared to the baseline aircraft. The study also shows that the choice of fuel cell operating temperature has a first-order impact on the total mass of the propulsive system due to the higher cooling requirement of the low temperature fuel cells.

Although recent studies have shown the possibility of running ‘standard’ spark-ignition engines with 6 pure ammonia the operating range remains limited mainly due to the unfavorable characteristics of 7 ammonia for premixed combustion and often requires the addition of a complementary fuel such as H2 8 to extend it. As the best way to add H2 is to crack ammonia directly on-board this paper focuses on 9 the impact of the upstream cracking level of ammonia on the performance and emissions of a single 10 cylinder spark ignition engine. Experiments were performed over several equivalence ratios 11 dissociation rates and load conditions. It is confirmed that only a slight rate of ammonia dissociation 12 (10%) upstream of the combustion considerably enhances the engine's operating range thanks to a 13 better combustion stability. In terms of pollutant emissions the partial dissociation of ammonia 14 especially for slightly lean mixtures induces a very clear trade-off between high NOx and high 15 unburned ammonia level for high and low ammonia dissociation rates respectively. Therefore 16 cracking NH3 does not only improve the operating range of ammonia-fueled spark ignition engines but 17 can also help to reduce NH3. However to reach the same engine output work higher ammonia fuel 18 consumption will be necessary since the global system efficiency is lower using fuel dissociation. In 19 addition the global warming effect is increased with dissociation level since a higher level of N2O is 20 generated by the hydrogen contribution.

Hydrogen delivered at hydrogen refuelling station must be compliant with requirements stated in different standards which require specialized sampling device and personnel to operate it. Currently different strategies are implemented in different parts of the world and these strategies have already been used to perform 100s of hydrogen fuel sampling in USA EU and Japan. However these strategies have never been compared on a large systematic study. The purpose of this paper is to describe and compare the different strategies for sampling hydrogen at the nozzle and summarize the key aspects of all the existing hydrogen fuel sampling including discussion on material compatibility with the impurities that must be assessed. This review highlights the fact it is currently difficult to evaluate the impact or the difference these strategies would have on the hydrogen fuel quality assessment. Therefore comparative sampling studies are required to evaluate the equivalence between the different sampling strategies. This is the first step to support the standardization of hydrogen fuel sampling and to identify future research and development area for hydrogen fuel sampling.