An intercomparison of CFD models to predict lean and non-uniform hydrogen mixture explosions

The paper describes an exercise on comparison of Computational Fluid Dynamics (CFD) models to predict deflagrations of a lean uniform hydrogen–air mixture and a mixture with hydrogen concentration gradient. The exercise was conducted within the work-package “Standard Benchmark Exercise Problem” of the EC funded Network of Excellence “Safety of Hydrogen as an Energy Carrier”, which seeks to provide necessary quality in the area of applied hydrogen safety simulations. The experiments on hydrogen–air mixture deflagrations in a closed 1.5 m in diameter and 5.7 m high cylindrical vessel were chosen as a benchmark problem to validate CFD codes and combustion models used for prediction of hazards in safety engineering. Simulations of two particular experiments with approximately the same amount of hydrogen were conducted: deflagration of a uniform 12.8% vol. hydrogen mixture and deflagration of a non-uniform hydrogen mixture, corresponding to an average 12.6 % vol. hydrogen concentration (27% at the top of the vessel, 2.5% at the bottom of the vessel) with ignition at the top of the vessel in both cases. The comparison of the simulation results for pressure and flame dynamics against the experimental data is reported.     

An inter-comparison exercise on CFD model capabilities to simulate hydrogen deflagrations in a tunnel

In the frame of the European Commission co-funded Network of Excellence HySafe (Hydrogen Safety as an Energy Carrier, www.hysafe.org), five organizations with significant experience in explosion modelling have performed numerical simulations of explosions of stoichiometric hydrogen–air mixtures in a 78.5 m long tunnel. The five organizations are the Karlsruhe Research Centre, GexCon AS, the Joint Research Centre, the Kurchatov Institute Research Centre and the University of Ulster. Five CFD (Computational Fluid Dynamics) codes with different turbulence and combustion models have been used in this Standard Benchmark Exercise Problem (SBEP). Since tunnels are semi-confined environments, hydrogen explosions in tunnels can potentially be critical accident scenarios from the point of view of the accident consequences and CFD methods are increasingly employed to assess explosions hazards in tunnels. The objective of the validation exercise is to assess the accuracy of the theoretical and numerical models by comparisons of the simulation results with the experimental data. A very good agreement between experiments and simulations was found in terms of maximum overpressures.     

Permeable fiber filter materials. Part 2. Filtering parameters

Translated from Poroshkovaya Metallurgiya, No. 2(326), pp. 32–35, February, 1990.     

Structure and mathematical model of a filtering fibrous material

Translated from Poroshkovaya Metallurgiya, No. 6(318), pp. 47–49, June, 1989.     

Structure and properties of welded joints in large thick-wall structures made of 25L steel welded without preheating

The effect of welding without preheating is investigated and the effect of additional operations by the transverse hill method on mechanical properties and structure-welded joints in 25L steel is studied and compared with properties after welding with preheating and high-temperature tempering. It is shown that after welding without additional operations, the heat-affected zone is characterized by the formation of a structure of upper granular bainite resistant to brittle fracture. The impact and ductility properties of this structure are higher than the requirements imposed on the parent metal.