Fire behaviors along timber linings affixed to tunnel walls in mines

Timber linings are applied as primary supports in the tunnel fault and fracture zones of mines. These linings are essential to prevent broken rock from falling during the occurrence of exogenous fires. In this study, experiments and numerical simulations were carried out using a fire dynamics simulator to investigate the flame-spread rate, flame characteristics, smoke movement, and spread process of timber-lining fires under different wind speeds of 0, 0.25, 0.5, and 0.75 m/s. It was found that cross-section flame spreading follows the three-stage sidewall-ceiling-sidewall pattern. Moreover, the average flame-spread rate increases along the vertical flame-spreading direction and decreases when the flame reaches the timber-lining corners. Moreover, the flame lengths underneath the timber-lining ceiling in the x-direction are longer than those in the y-direction. As the wind speed increases, the normalized flame lengths R(f) in the two directions decrease, and the maximum temperature underneath the ceiling decreases. In addition, the maximum temperature in the three tunnel sections of interest is first recorded in the tunnel cross-section in the initial fire stage. Higher wind speeds correspond to farther distances of the maximum-temperature points of the three timber-lining sections from the fire source.

Gas fuel combustion and related problems

Combustion, as it is well known, is based on chemical reactions. If we look at a clear scientific definition of the term “combustion”, then combustion will be a process of rapid high-temperature oxidation, combining physical and chemical phenomena. Combustion consists of a large number of elementary redox processes leading to the redistribution of valence electrons between atoms of interacting substances.Modern theories of combustion relate flame spreading in gases to chemical chain reactions[1]. Nowadays, in a view of the wide spread of gas, understanding of a ship fuel and analysis of gas related problems of combustion are more and more critical. Gas itself is not able to ignite in a combustion chamber as a conventional fuel just because of compression and temperature rising. It requires a strong and efficient source of fire. The article is focused on analyzing igniting, flame spreading and detonation in a combustion chamber. The detonation condition was assessed in case of using gas as ships fuel.

Thermonuclear X-ray bursts from 4U 1636 − 536 observed with AstroSat

ABSTRACT We report results obtained from the study of 12 thermonuclear X-ray bursts in six AstroSat observations of a neutron star X-ray binary and well-known X-ray burster, 4U 1636 − 536. Burst oscillations (BOs) at ∼ 581 Hz are observed with 4–5σ confidence in three of these X-ray bursts. The rising phase BOs show a decreasing trend of the fractional rms amplitude at 3σ confidence, by far the strongest evidence of thermonuclear flame spreading observed with AstroSat. During the initial 0.25 s of the rise a very high value ($34.0\pm 6.7{{{\ \rm per\ cent}}}$) is observed. The concave shape of the fractional amplitude profile provides a strong evidence of latitude-dependent flame speeds, possibly due to the effects of the Coriolis force. We observe decay phase oscillations with amplitudes comparable to that observed during the rising phase, plausibly due to the combined effect of both surface modes, as well as the cooling wake. The Doppler shifts due to the rapid rotation of the neutron star might cause hard pulses to precede the soft pulses, resulting in a soft lag. The distance to the source estimated using the photospheric radius expansion bursts is consistent with the known value of ∼6 kpc.

Effect of Foaming Temperature on Microstructure, Mechanical Properties and Flame Spread Rate in PET–PEN Copolymer

Polymer foams are expanding their applications into functional materials. Partial foam structure has been fabricated in polyethylene terephthalate–polyethylene naphthalate (PET–PEN) copolymer by solid state foaming. Through SEM image analyses, a potential to fabricate gradient foam structures with micropores and unfoamed skin layers has been identified. The post-foaming temperature Tf tune the pore size distribution. Radial distribution of micromechanical properties, indentation hardness and elastic modulus were measured for the partial foam and their values were around 0.12 GPa and 2.0 GPa, respectively, for the outer foamed region. Foaming temperature affects the glass transition temperature Tg, the coefficient of thermal expansion and the flame spreading rate. For the range of Tf ≤ 60°C, thermal expansion coefficients for T > Tg are about 0.5 m/m°C (steep expansion group, SEG). When Tf is above 80 °C, they are around 0.02 m/m°C (mild expansion group, MEG). The burning rate of SEG is 2.8 times higher than that of MEG.

Effect of Cyclotriphosphazene-Based Curing Agents on the Flame Resistance of Epoxy Resins

Epoxy resins are characterized by excellent properties such as chemical resistance, shape stability, hardness and heat resistance, but they present low flame resistance. In this work, the synthesized derivatives, namely hexacyclohexylamino-cyclotriphosphazene (HCACTP) and novel diaminotetracyclohexylamino-cyclotriphosphazene (DTCATP), were applied as curing agents for halogen-free flame retarding epoxy materials. The thermal properties and combustion behavior of the cured epoxy resins were investigated. The obtained results revealed that the application of both derivatives significantly increased flame resistance. The epoxy resins cured with HCACTP and DTCATP exhibited lower total heat release together with lower total smoke production compared to the epoxy materials based on conventional curing agents (dipropylenetriamine and ethylenediamine). Comparing both derivatives, the HCACTP-cured epoxy resin was found to provide a higher flame resistance. The designed novel class of epoxy materials may be used for the preparation of materials with improved flame resistance properties in terms of flame spreading and smoke inhibition.

COMPARATIVE ANALYSIS OF THE RUSSIAN MARITIME SHIPPING REGISTER REQUIREMENTS AND THE RUSSIAN RIVER REGISTER REQUIREMENTS FOR COMBUSTIBLE MATERIALS

Comparative analysis results applicable the requirements of the Russian Maritime Register of Shipping Rules and Russian River Register Rules to structural fire protection (combustible materials) of river-sea-going ships are presented. The study purpose is to compare the safety standard levels laid down in the Rules of these classification societies for river-sea-going ships operating in similar areas and navigation conditions. As a research method, we used a point-by-point analysis of the requirements and approaches of these classification societies, as well as international and national regulatory documents on the basis of which they were developed. It is shown that the approach to classifying materials based on their test results, given in the rules of the River and Sea Registers, is generally the same, but there are fundamental differences in methods of testing materials and criteria for evaluating their results (combustibility tests, flame spreading, flammability, combustion products toxicity, smoke-forming capacity). Comparative analysis results are presented and directions for improving and harmonizing the regulatory and technical framework for mixed navigation vessels in relation to methods of testing materials and criteria for evaluating their results are outlined. The information presented in this article can be used for developing the Russian River Register Rules requirements, and also by design engineering organizations for developing technical documentation (analysis of compliance with the Rules requirements) necessary for a vessel transfer into River or Sea Registers classes.