Numerical Evaluation of Safety Wall Bending Strength during Hydrogen Explosion

The main aims of this study are to assess numerically the stress state of a solid wall which is installed at the hydrogen fueling station in order to protect personnel from the consequences of the accidental hydrogen explosion, define the bending stress values in the foot of the wall exposed to explosion wave pressure forces and located at different distances from explosion epicenter in order to choose appropriate construction material of the wall and assess the minimum thickness of the wall satisfying bending strength condition. A three-dimensional mathematical model of hydrogen-air mixture explosion is used to define the distribution of the maximum overpressure on the wall surface. To assess the bending stress state at the foot of the wall, the design scheme of a cantilever beam is considered. It is assumed that the maximum overpressure force field influences the wall at the same time to assess the worst possible scenario. Actually, the computer-based methodology of how to resolve a coupled problem of explosion gas dynamics and defense wall strength is suggested. This technique allows evaluating of the construction parameters of the wall, which protects the personnel against consequences of the explosion wave exposure, without the destruction of the wall.

Influence of Cavity Width on Attenuation Characteristic of Gas Explosion Wave

This study aimed to investigate the influence of cavity width on the attenuation characteristic of gas explosion wave. Attenuation mechanism of gas explosion wave through cavity was obtained by numerical simulation. The gas explosion shock wave energy can be greatly attenuated through the cavity structure in five stages, namely, plane wave, expansion, oblique reflection, Mach reflection, and reflection stack, to ensure that it is eliminated. Cavities with various width sizes, namely, 500 ∗ 300 ∗ 200, 500 ∗ 500 ∗ 200, and 500 ∗ 800 ∗ 200 (length ∗ width ∗ height, unit: mm), were experimented to further investigate the attenuation characteristics through a self-established large-size pipe gas explosion experimental system with 200 mm diameter and 36 m length. Results showed an evident attenuation effect on flame duration light intensity (FDLI) and peak overpressure with increasing cavity width. Compared with 300 mm, the overall FDLI decreased by 83.0%, and the peak overpressure decreased by 71.2% when the cavity width was 800 mm. The fitting curves of the FDLI and peak overpressure attenuation factors to width-diameter demonstrated that the critical width-diameter was 2.19 when the FDLI attenuation factor was 1. The FDLI attenuation factor sharply decreased at the width-diameter ratio range from 1.5 to 2.5 and basically remained steady at 0.17 at the width-diameter ratio range from 2.7 to 4.0. The peak overpressure attenuation factor gradually decreased with the increase of width-diameter ratio and changed from 0.93 to 0.28 with width-diameter ratio from 1.5 to 4.0. The research results can serve as a good reference for the design of gas explosion wave-absorbing structures.

REASONS OF MINE ACCIDENT OCCURING WITH DISASTROUS CONSEQUENCES

In the work it is proved that methane explosions with disastrous consequences have become after conversion to high-effective mining of extraction pillar during mining flat and steep coal seams at functioning extracting areas. It is established that during high-efficient mining of extracting areas, first combustion and methane explosions happen at worked space, where they are initiated with occurred and non-noticed places of coal self-ignition. From worked space burning methane outbursts by explosion wave from the cove to the working face and near workings where the explosion develops with coal dust presence. Technical solutions for prevention such accidents are proposed.

Optimasi desain rencana tanggul lepas pantai NCICD di Teluk Jakarta terhadap kemungkinan tsunami akibat letusan Gunung Anak Krakatau

The infrastructural plans in the Jakarta Bay to reduce risks of flooding in Jakarta city comprise a large sea dike that encloses a retention lake. Part of the planned dike has the shape of the iconic Garuda bird. This shape is based on NCICD Stage-B Master Plan, where the form shape has not been tested on hydraulic perspective. Therefore, testing of wave run-up has been investiagated to find the optimum form of the Garuda Shape. The simulation of wave run-up uses Hawassi Model, where the model is governed by Boussinesq wave equation with considering wave-wave interaction. This paper shows that if in the future an explosion of Anak Krakatau will occur with strength 1/4th of the original Karkatau 1883 explosion, wave crests of 11m and troughs of 6m may collide against the birds head. As an alternative example, a more optimized design of the dike is constructed that reduces the maximal wave effects considerably.

The use of the spatial characteristics technique with the view of estimating the explosion wave impact on the stuck drilling string zone / Wykorzystanie techniki charakterystyk przestrzennych do określania wpływu fali uderzeniowej na przychwyconą kolumnę przewodów wiertniczych

Studied here are the results of the asymmetric problem solution of the thick walled circular cylinder elasticity using the spatial characteristics technique. The practical implementation of the solution of the problem is based on the calculation of the stress-caused deformation state of the stuck drilling string zone affected by the explosion wave action upon the inner wall of the pipe. Suggested here is the technique for determining axual σz and circular σθ stress on the drill pipe wall as well as the radial displacements ur of the stuck drill pipe outer surface under the action of the explosion shock wave. The above technique enables to make a sound selection of the cylindrical explosive charge weight in order to avoid the residual strain during the drilling string shaping off and uncoupling the threaded joints or to prevent them from exceeding the admissible level.