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Micron‐sized dry water particles assembled from gaseous silica and deionized water were prepared by physical dispersion method, and the effects of two chemical components on the microstructure and fire extinguishing efficiency of dry water materials were analyzed. Three different filling pressures were selected to study their effect on dry water extinguishing efficiency of wood crib fire. The effect of dry water on fire extinguishing efficiency of wood crib was studied by building wood crib of different sizes. The results show that the larger filling pressure inhibits the fire more obviously, but the dry water structure is easy to be damaged. Dry water can adhere to the inside of the wood crib structure and exert its role of cooling and isolating oxygen to inhibit its smoldering under a certain release pressure. With the increase of the size of wood crib, the suppression efficiency of dry water materials on wood crib fire gradually decreases with increasing extinguishing time. The fire extinguishing efficiency of dry water with sodium acetate is improved, but its structure is not stable. By comparing and analyzing the critical combustion rate and oxygen concentration of wood crib, it was found that continuous cooling to reduce the combustion rate and smoldering is the dominant mechanism of dry water on wood crib fire. [ABSTRACT FROM AUTHOR]

Using the ANSYS finite element analysis software to analyze the modal of the case and its modules by the substructure method,the natural frequency and mode shape of the equipment are obtained. Synthesizing the results of the modal analysis,the comprehensive structure improvements recommendations are proposed. And the substructure method has important reference value for the large-scale electronic equipments.

Epoxy resin and carbon fiber were used as the reinforcement to modify phenolic resin. Phenolic epoxy resin was prepared by physical blending, and carbon fiber was introduced into the resin matrix, and meanwhile the curing agent was added. The flame retardancy and thermal stability of the samples were evaluated, and the mechanical performance of the samples was characterized to investigate the overall performance. The flame retardancy of phenolic epoxy resin decreased slightly with epoxy resin of 5 wt%. The oxygen index was decreased by 6.3%, the ignition time was shortened by 66 s, and the peak heat release rate was increased by 8.9%. The tensile strength and elastic modulus were increased by 46% and 26.1%, respectively. The flame retardant and mechanical properties of phenolic epoxy resin were improved the most with short carbon fiber of 0.5 wt%. The oxygen index was increased by 4.6%, the ignition time was delayed by 35 s, the peak heat release rate was reduced by 18.9%, the carbon residue rate at 800℃ was increased by 60.4%, the apparent activation energy was increased by 11.3%, and the tensile strength and elastic modulus were improved by 90.4% and 87.9%, respectively. [ABSTRACT FROM AUTHOR]

Few investigations have systematically addressed the porosity effects of upward flame spread over fabric fuels, although the porosity is a special property for fabric fuels. The present paper studies the porosity and area density effects on upward flame spreading using 160.0 cm tall and 8.0 cm wide flax fabric samples with various porosities and area densities. The flame shape, flame length, flame spread rate, ignition time, standoff distance and surface temperature distribution are obtained and analyzed. The major findings are summarized as follows: as the porosity increases and corresponding area density declines, the flame spread rate and flame length increase, whereas the ignition time decreases, which is because the oxygen can reach the fuel surface in the pyrolysis region more easily and, subsequently, the heat flux received by the virgin fuels increases. The two parameters of flame standoff distance and surface temperature in the preheating region can be applied to characterize the heat flux received by the virgin fuels. Generally, when the porosity increases and the corresponding area density decreases, the flame standoff distance and the surface temperature at the same distance from pyrolysis front increase, which reveals that the heat flux received by the virgin surface increases. [ABSTRACT FROM AUTHOR]

In this paper, a series of upward flame spreading experiments were conducted on thin flax fabric with various widths ranging from 3.0 to 8.0 cm and length of 1.6 m. Symmetric ignition at the entire bottom edge of samples led to two-sided upward flame growth initially. A very interesting behavior of flame blown off was observed in upward flame spreading and an explanation was provided based on the increased buoyancy-induced velocity at the flame base. When the sample width is 6 cm or less, the flame length increases to a critical value and, correspondingly, the buoyancy-induced velocity reaches the blow off velocity, which results in a flame being blown off on one side. The remaining flame on the other side would shrink in length and propagate to the end of the sample with an asymptotically constant length and steady spread rate. For samples wider than 6 cm, the two-sided flame continues to spread to the end of samples and the self-induced blow off phenomenon is not observed. Moreover, the width effects on the flame height, flame thickness and flame spread rate are analyzed and explained in this paper. The results of this study may help advance better understanding of flame blow off behaviors over solid surfaces and have implications concerning fire control of flame spread over solid fuels. [ABSTRACT FROM AUTHOR]