Model scale tunnel fire tests with longitudinal ventilation

Results from a series of tests in a model tunnel (1:23) are presented. Tests were carried out with longitudinal ventilation under different fire conditions. Wood cribs were used to simulate the fire source, which was designed to correspond to a scaled-down HGV (Heavy Goods Vehicle) fire load. The parameters tested were: the number of wood cribs, type of wood cribs, the longitudinal ventilation rate and the ceiling height. The heat release rate, fire growth rate, maximum gas temperature beneath the ceiling, temperature distribution, total heat flux at floor level, flame length, and back-layering length were investigated. Correlations for these parameters were investigated and proposed for longitudinal flow in tunnels.     

Model scale tunnel tests with water spray

A model scale study (1:23) was carried out in order to improve the basic understanding of water spray systems in longitudinal tunnel flow. The water spray system consisted of commercially available axial-flow hollow cone nozzles. Tests with both a deluge system made of 12 nozzles placed directly above the fire source and a water curtain system consisting of four nozzles placed either downstream or upstream of the fire source were carried out. A wood crib was used to simulate the fire source, which was designed to correspond to a HGV (heavy goods vehicle) fire load in large scale. A second wood crib was used as a target pile and was placed downstream the ignited wood crib. The parameters varied were the water flow rate and water pressure, the longitudinal ventilation rate and the arrangement of the nozzle system. Possible fire spread between wood cribs, with a free distance corresponding to 15 m in large scale, was investigated.     

Model scale railcar fire tests

A series of tests has been performed in a model of a typical passenger train compartment (railcar). The tests were carried out on a scale of 1–10. The main purpose of the tests was to investigate if it is possible to calculate the heat release rate for a flashed over train compartment with simple mathematical expressions derived for ordinary compartment fires. The combustion that takes place outside the windows was considered in the study. The parameters that were varied include: the ventilation, the fuel load and the type of interior surface material. In all tests, one door was open and the number of windows varied from all windows closed, to all windows opened. The ignition took place in the corner of the model compartment opposite the door opening.     

Structural and magnetic properties of (Cr1−x Mn x )5Al8 solid solution and structural relation to hexagonal nanolaminates

Electron microscopy is used to reveal the competitive epitaxial growth of bcc structure (Cr_1?x Mn _x )₅Al₈ and (Cr_1?y Mn _y )₂AlC [M _n+1AX _n (MAX)] phase during both magnetron sputtering and arc deposition. X-ray diffraction θ–2θ measurements display identical peak positions of (000n)-oriented MAX phase and (Cr_1?x Mn _x )₅Al₈, due to the interplanar spacing of (Cr_1?x Mn _x )₅Al₈ that matches exactly half a unit cell of (Cr_1?y Mn _y )₂AlC. Vibrating sample magnetometry shows that a thin film exclusively consisting of (Cr_1?x Mn _x )₅Al₈ exhibits a magnetic response, implying that the potential presence of this phase needs to be taken into consideration when evaluating the magnetic properties of (Cr, Mn)₂AlC.     

Correlation between temperatures and oxygen measurements in a tunnel flow

A correlation between measured oxygen concentrations and temperature measurements in a longitudinal tunnel flow has been validated. Such a correlation was first proposed by Newman [Experimental evaluation of fire-induced stratification. Combust Flame 1984;57:33–9] for use in mine and duct fires. Such correlations can be important when trying to estimate the heat release rate in tunnel fires where a lack of oxygen readings or technical problems with instruments forces one to find alternative solutions.     

Large Scale Tunnel Fire Tests with Large Droplet Water-Based Fixed Fire Fighting System

This paper presents the main results of six large scale fixed fire fighting system tests that were carried out in the Runehamar tunnel in September 2013. It describes the background and the performance of the system. The main fire load consisted of 420 standardized wood pallets and a target consisting of a pile of 21 wood pallets placed 5 m from the rear end of the main fire load. The purpose was to investigate possible fire spread. The water spray system is a deluge zone system delivering 10 mm/min in the activated zone. The detection system was simulated with use of thermocouple in the tunnel ceiling. The alarm was registered when the ceiling gas temperature was 141°C. After alarm was obtained the system was activated manually after a given delay time that was varied in the tests. The heat release rates in tests with fire suppression were reduced to 20–45 MW compared to 100 MW estimated for a free-burn test or 75 MW in test 6 with a failure of activation. Fire spread to the target was prevented after fire suppression.     

In-situ electrical characterization of ultrathin TiN films grown by reactive dc magnetron sputtering on SiO2

Ultrathin TiN films were grown by reactive dc magnetron sputtering on thermally oxidized Si (100) substrates. The electrical resistance of the films was monitored in-situ during growth in order to determine the minimum thickness of a continuous film. The coalescence thickness has a minimum of 1 nm at a growth temperature of 400 °C after which it increases with growth temperature. The minimum thickness of a continuous film decreases with increasing growth temperature from 2.9 nm at room temperature to 2.2 nm at 650 °C. In-situ resistivity measurements show that films grown at 500 °C and above are resistant to oxidation indicating high density. X-ray photoelectron spectroscopy and X-ray diffraction measurements show that the TiN grain stoichiometry and grain size increases with increasing growth temperature.     

Influence of MgO nano-crystals on the thermodynamics, hydrogen uptake and kinetics in Mg films

Hydrogen uptake in thin sputtered magnesium films covered with a Palladium layer was studied by resistance measurements. During growth, oxygen was introduced into the chamber in small amounts and the effect on the resistance, measured in situ, while growing, was monitored. This resulted in the formation of a mixture of MgO nanocrystals and layers in the Mg films. The measurements were made in situ in the sputtering chamber where the samples were grown. The aim of the study was to study the effect of oxygen contamination on hydrogen uptake in Mg films, as well as studying the uptake kinetics. Previous work on clean Mg films has shown that hydride formation at the surface reduces greatly the rate of hydrogen uptake further inside the film. These measurements show that the presence of oxygen contamination initially increases the rate of uptake greatly but decreases it when the Mg film is contaminated further with more oxygen.