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During the production or storage of a hydrogen gas in a confined space, the formation of an explosive mixture can occur in the event of an accidental leakage. Therefore, in order to ensure safety, it is necessary to create a room ventilation system that prevents the formation hazardous zones with an elevated content of combustible gases that can lead to a local explosion. The paper presents the results of calculations and experiments on hydrogen leakage with a constant flow rate into a ventilated room with a volume of 8 m3. In the experiments, the emergence of depressurized electrolyzer were simulated with various leakage rates. The dependence of the hydrogen volumetric content on the time in various points of the room was obtained. In order to test the prognostic capabilities of the calculation methodology, preliminary calculations were performed. Several approaches to the application of boundary conditions were investigated. The proposed calculation methodology is in the agreement with the experimental data.

Accidents involving the release of large amounts of combustible gases, such as hydrogen, methane, carbon monoxide, etc., are possible at nuclear power plants, as well as in chemical production facilities. Currently, calculation tools are used for substantiate explosion safety. To permit their validation, experimental data obtained from a prototype facility are required. RFNC–VNIITF has developed a two-chamber BM‑U facility disposing a total volume of 156 m3 for simulating emergency processes of leakages and combustion of hydrogen-containing vapor-gas mixtures. Inside this facility, equipment prototypes characteristic of the simulated object can be installed to account for their influence on the overall level of explosion safety. The BM‑U facility is additionally equipped with the necessary state-of-the-art measuring instruments. When the facility was put into operation, an experiment with the ignition of an air mixture with 6 vol % of hydrogen was conducted.

During the storage or production of a hydrogen gas within a limited space, a combustible mixture may form in the event of an emergency leakage. In order to ensure safety, it is necessary to develop a room ventilation system for preventing the formation of areas in which there is an increased content of combustible substances. The present article considers experiments on the leakage of a hydrogen gas in a ventilated room with a volume of 8 m3. Emergencies connected with the depressurization of electrolyzer or a high-pressure hydrogen vessel during the storage were simulated. The time-dependencies of the hydrogen content at various points of the room were obtained. Data on the combustion of the hydrogen-air mixture in the room with relief valves were obtained from experiments carried out with the ignition of the mixture.

Hydrogen-air mixtures are highly flammable. The acceleration of the flame and subsequent deflagration to detonation transition (DDT) can cause enormous damage to hydrogen energy infrastructure. Since leakage of hydrogen and its subsequent stratification according to the height of a room or structure is the most likely process to cause emergencies that arise at hydrogen energy facilities, studies of combustion and detonation in stratified hydrogen-air mixtures are of particular interest. The paper presents the results of the estimated flame front velocity and maximum overpressure in experiments involving the deflagration of a hydrogen-air mixture for vertical gradients of the hydrogen volume fraction in a closed channel with an annular blockage. This horizontally oriented channel has a square section of 0.6 × 0.6 m and a length of 12 m. The average hydrogen content of the gas used in the experiments varied in the range of 9–15 vol %.

Seal failure of equipment and compressed gas cylinders containing hydrogen and combustible gasses attendant in their production processes is one of the standard emergency scenarios at infrastructure facilities of hydrogen energy. CFD program codes are being increasingly used to predict the propagation of gas clouds through ventilated enclosures and the characteristics of their combustion taking into account the cluttering of the space. Experimental data are necessary for their verification. For this purpose, demonstration experiments were performed on the BM-LR stand – a container with volume 11 m3. Data on the propagation of a mixture of hydrogen and methane with air as well as the speed of the flame front were obtained in the experiments. Even though hydrogen mixtures with content >10 vol.% are highly buoyant such mixtures are more dangerous than methane even in slow defl agration regimes (front speed ≤ 100 m/sec).

During their initial development, passive autocatalytic hydrogen recombiners (PARs) were presumed to operate in a flameless mode. However, a series of independent experiments conducted in the 1990s observed hydrogen-air gas mixtures igniting as a result of PAR operation. This ignition was due to overheating of the catalyst, leading to the thermal ignition of hydrogen-air mixtures (termed “internal ignition”). Additionally, individual particles may become detached from the catalyst substrate and swept up by the gas stream to subsequently ignite the gas mixture outside the recombiner housing, a phenomenon known as “external ignition.” This article delves into the experimental findings concerning two mechanisms of hydrogen-air mixture ignition. Direct evidence for recombiner-induced external ignition was captured using the Schlieren method. It was confirmed that the concentration limits for external ignition differ from those for internal ignition. In order to ensure nuclear power plant safety, the development of a testing methodology for the technology used in manufacturing catalysts is essential.

Background Issues of hydrogen explosion safety are extremely relevant. Search for solutions requires both experimental and computational methods. Aim To experimentally study the turbulent combustion of hydrogen-air mixtures and to test the CABARET-COMBUSTION CFD calculation code using the obtained data. Materials and methods The study includes experiments conducted in a facility representing a large diameter pipe, as well as numerical simulation of deflagration combustion. Results The calculated data on the flame front propagation velocity and pressure dynamics at the shock wave front are consistent with experimental results. Conclusion The obtained results indicate the potential of using the CABARET-COMBUSTION CFD code in the numerical solution of hydrogen-air mixture combustion problems. This code and its testing on data obtained with high-quality diagnostics will increase the predictive capabilities of supercomputer simulation for the analysis of hypothetical accidents at a qualitatively new level.

The reaction of readily available N,N′ -diaryl-4-chloromethylimidazolium chlorides with thiols afforded 4-(alkyl)arylsulfanylmethyl- N,N′ -diarylimidazolium salts. The oxidation of these salts with hydrogen peroxide catalyzed by ammonium paramolybdate gave the previously unknown 4-(alkyl)arylsulfonylmethyl- N,N′ -diarylimidazolium salts. The synthesized imidazolium salts can be used as sources of N -heterocyclic carbenes (NHCs). The conditions were found for the selective palladation of these compounds involving the C(2) atom of the imidazole ring. Palladium complexes with NHC ligands functionalized with RSCH 2 and RSO 2 CH 2 groups were synthesized. The potential applicability of these complexes as catalysts for cross-coupling reactions was demonstrated.

A method for the synthesis of 1,3-diaryl-4-hydroxymethylimidazolium chlorides by selective hydrolysis of readily available 1,3-diaryl-4-chloromethylimidazolium chlorides upon heating in aqueous DMSO was proposed.

A new multicomponent reaction leading to the formation of an imidazole ring was discovered: N,N ′-diaryl-1,4-diazabuta-1,3-dienes reacted with trialkyl orthoformates, chloro(trimethyl)silane and water to give N,N ′-1,3-diaryl-4-oxoimidazolinium salts or their tautomers, 4-hydroxyimidazolium salts.