About the fire hazard of transport hydrotunnels

В статье рассмотрена достаточно новая проблема, связанная с появлением и развитием перспективной транспортной инфраструктуры – гидротоннелей. Показано, что ввиду большой пожарной нагрузки, которую представляют собой проходящие по гидротоннелю суда (пассажирские, сухогрузы, контейнеровозы. танкеры) возможно возникновение пожаров, угрожающих как самим судам и их экипажам, так и конструкции гидротоннеля – обрушение его свода из-за экстремальных тепловых нагрузок. Проведено компьютерное моделирование с использованием полевой модели пожара, подтвердившее факт быстрого роста температуры и концентрации токсичных продуктов горения, а также «тоннельный эффект» - прохождение высокотемпературного потока газов к одному из торцов тоннеля. Даны предложения по действиям персонала судов в гидротоннеле и пожарных кораблей по тушению пожара и спасению людей. Показана необходимость оборудования некоторых гидротоннелей дренчерными системами пожаротушения. Сделан вывод о необходимости дальнейших исследований в части пожарной безопасности транспортных гидротоннелей и разработке соответствующего нормативного документа. The article considers a fairly new problem associated with the emergence and development of a promising transport infrastructure – hydrotunnels. It is shown that due to the large fire load, which is represented by vessels passing through the hydrotunnel (passenger, dry cargo, container ships. tankers) there may be fires that threaten both the ships themselves and their crews, and the structure of the hydrotunnel – the collapse of its arch due to extreme thermal loads. A computer simulation was carried out using a field model of a fire, which confirmed the fact of a rapid increase in temperature and concentration of toxic combustion products, as well as the "tunnel effect" - the passage of a high-temperature gas flow to one of the ends of the tunnel. Suggestions are given on the actions of the personnel of vessels in the hydrotunnel and fire ships to extinguish the fire and rescue people. The necessity of equipping some hydrotunnels with drencher fire extinguishing systems is shown. The conclusion is made about the need for further research in terms of fire safety of transport hydraulic tunnels and the development of an appropriate regulatory document.

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DISPERSED PHASE VELOCITY IN A HIGH-TEMPERATURE GAS FLOW

High Temperature Material Processes An International Quarterly of High-Technology Plasma Processes ◽

10.1615/hightempmatproc.2019030506 ◽

2019 ◽

Vol 23 (4) ◽

pp. 319-328

Author(s):

Dmitry V. Nesterovich ◽

Oleg G. Penyazkov ◽

Yu. A. Stankevich ◽

M. S. Tretyak ◽

Vladimir V. Chuprasov ◽

...

Keyword(s):

High Temperature ◽

Phase Velocity ◽

Gas Flow ◽

Dispersed Phase ◽

High Temperature Gas

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Comparative Study of GaN Growth Process by MOVPE

MRS Proceedings ◽

10.1557/proc-572-463 ◽

1999 ◽

Vol 572 ◽

Author(s):

Jingxi Sun ◽

J. M. Redwing ◽

T. F. Kuech

Keyword(s):

High Temperature ◽

Comparative Study ◽

Gas Phase ◽

Residence Time ◽

Gas Flow ◽

Flow Sheet ◽

Flow Zone ◽

High Quality ◽

Phase Temperature ◽

High Temperature Gas

ABSTRACTA comparative study of two different MOVPE reactors used for GaN growth is presented. Computational fluid dynamics (CFD) was used to determine common gas phase and fluid flow behaviors within these reactors. This paper focuses on the common thermal fluid features of these two MOVPE reactors with different geometries and operating pressures that can grow device-quality GaN-based materials. Our study clearly shows that several growth conditions must be achieved in order to grow high quality GaN materials. The high-temperature gas flow zone must be limited to a very thin flow sheet above the susceptor, while the bulk gas phase temperature must be very low to prevent extensive pre-deposition reactions. These conditions lead to higher growth rates and improved material quality. A certain range of gas flow velocity inside the high-temperature gas flow zone is also required in order to minimize the residence time and improve the growth uniformity. These conditions can be achieved by the use of either a novel reactor structure such as a two-flow approach or by specific flow conditions. The quantitative ranges of flow velocities, gas phase temperature, and residence time required in these reactors to achieve high quality material and uniform growth are given.

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On a composition of combustion products at a burning of methane-fluorinated hydrocarbon mixtures in air

Pozharnaia bezopasnost` ◽

10.37657/vniipo.pb.2020.43.68.005 ◽

2020 ◽

pp. 44-49

Author(s):

Алексей Юрьевич Шебеко ◽

Юрий Николаевич Шебеко

Keyword(s):

Combustion Products ◽

Hydrocarbon Mixtures ◽

Gaseous Mixtures ◽

Fire Extinguishing ◽

Simplified Method ◽

Room Volume ◽

Composition Of Combustion Products ◽

Fluorinated Hydrocarbons

Выполнена расчетная оценка равновесного состава продуктов горения околостехиометрических смесей вида метан - фторированный углеводород - воздух с использованием как программного комплекса Chemical Workbench, так и предложенной в настоящей работе упрощенной методики. Найдено, что основными продуктами горения являются CO, HO, CO, HF. При этом концентрации прочих продуктов горения имеют существенно более низкие значения. С помощью программного комплекса FDS выполнен расчет динамики концентраций опасных продуктов (СО, HF) в атмосфере модельного помещения объемом 12,6 м. Найдено, что для указанного помещения предельно допустимая концентрация CO достигается через 730 с после начала горения, а HF - практически мгновенно. Результаты работы могут быть полезны при применении фторированных углеводородов для пожаротушения и флегматизации горючих газовых смесей. Calculations of equilibrium compositions of combustion products at burning of near stoichiometric mixtures of methane-fluorinated hydrocarbon-air are presented. The program tool Chemical Workbench was used. Also a Simplified method was proposed. It was found that CO, HO, CO and HF are the main combustion products, and the concentration of other products are much more lower. The results of the calculations of the concentrations of the above mentioned products (CO, HO, CO and HF) by means of the simplified method are close to that obtained by the tool Chemical Workbench ones. The concentrations of CO and HF (the main hazardous products) as a function of time were determined for a typical room volume of 12, 6 m using the program tool FDS 6. It was found that a limiting allowable concentration of CO was reached after 730 s from the burning beginning, but at the case of HF this concentration was reached almost instantaneously. The results of this study can be used at an application of the fluorinated hydrocarbons for fire extinguishing and inertization of flammable gaseous mixtures.

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Проблема защиты высокостеллажных складов спринклерными автоматическими установками пожаротушения

Pozharnaia bezopasnost` ◽

10.37657/vniipo.2020.98.1.011 ◽

2020 ◽

Author(s):

Sergey Kopylov ◽

Leonid Meshman ◽

Leonid Tanklevsky ◽

Alexander Bondar

Keyword(s):

Early Stage ◽

Side Surface ◽

Spray Angle ◽

Stored Products ◽

Building Structures ◽

Fire Load ◽

Electric Cars ◽

Fire Extinguishing ◽

Start Up ◽

Irrigation Intensity

Рассмотрены вопросы обнаружения и тушения пожара при высокостеллажном складировании продукции, являющейся пожарной нагрузкой, с использованием пожарных извещателей и автоматических установок пожаротушения (АУП). Проанализированы различные схемы АУП и подачи огнетушащих веществ (ОТВ), их преимущества и недостатки. Исходя из особенностей пожара на стеллажных складах, показана необходимость скорейшего его обнаружения и подачи ОТВ. Сформулированы задачи, решение которых позволит добиться максимальной эффективности применения АУП на высокостеллажных складах.Currently, there is a tendency to equip objects (warehouses, shopping centers) with racks for storing various products. The stored products represent a significant fire load (combustible packaging, products themselves, etc.). Racks can be of a great height (more than 10 m), be located both in isolation and in groups, and even be load-bearing as a part of the power frame of the building. The technology of racks loading and unloading provides for the use of electric cars with special lifts (stacker). The result of a fire at an object with high-rack storage (HRS) is a large material damage due to the destruction of stored products and damage (collapse) of the building as well as risk to people and undesirable socio-psychological resonance. Due to rapid flame spread on a vertical in case of fire on the object with HRS, the most important condition for the effective use of automatic fire extinguishing systems is to minimize the time both of fire detection and of commencement of extinguishing agent supply by appropriate sprinklers. It can be achieved by means: a) of special heat-accumulating screens above the racks at a large distance from the top of the stored goods to the ceiling that ensure the speedy operation of heat detectors; b) of satellite detectors which provide a compulsory start-up of the sprinklers. For the purpose of selective operation each satellite fire detector is equipped with a deflector or diaphragm so that the field of view of the detector agrees with the irrigated area. To concentrate the fire extinguishing agent supply directly to the high-rise rack and to provide increased irrigation intensity at the border of the sprayed stream, the spray angle of the sprinkler is limited by the flow shaper. Most often, the sprayed water flow is supplied to the upper tier of the rack and its side surface. Thus, this article presents the features of effective fire fighting at objects with HRS of products that are a fire load at an early stage of fire ignition. Various schemes of automatic fire extinguishing systems and their start-up are analyzed. In the future, it is necessary to carry out a calculated justification of the sprinkler installation sites to ensure the fire extinguishing agent supply both to the upper part and side surface of the burning rack as well as to protect neighbour racks and building structures.

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Роль декоративно-отделочных, облицовочных материалов стен и потолков, покрытий полов в развитии пожара и формировании его опасных факторов

Pozharnaia bezopasnost` ◽

10.37657/vniipo.2020.98.1.001 ◽

2020 ◽

Author(s):

Aleksey Shebeko ◽

Natalia Konstantinova ◽

Olga Krivoshapkina

Keyword(s):

Kinetic Parameters ◽

Building Materials ◽

Fire Hazard ◽

Fire Risk ◽

Point Of View ◽

Fire Load ◽

Technical Literature ◽

Wood Composition ◽

Heat Loads ◽

Facing Material

Проанализирована роль декоративно-отделочных, облицовочных материалов и покрытий полов в формировании опасных факторов пожара (ОФП). Проведены расчеты распространения ОФП в модельном помещении с учетом вклада облицовочного материала стен и потолка. Показана возможность применения рассмотренного подхода для моделирования условий (стандартных и нестандартных) испытаний строительных материалов и конструкций на пожарную опасность (например, фасадных систем) и гибкого нормирования при использовании декоративно-отделочных, облицовочных материалов и покрытий полов в зданиях и сооружениях.Article presents the study of the possibility to describe thermal decomposition and thermal oxidation processes of fire load finishing materials by means of the kinetic parameters. These parameters are defined by results of termogravimetric analysis for modeling the dynamics of fire development. Nowadays the problem of modeling the distribution of hazardous fire factors (HFF) in buildings and constructions has wide practical application, however techniques of HFF modeling do not take into account as fire load finishing and facing materials of building and construction premises in development of a fire, so they are not considered at an estimation of safe evacuation of people from buildings and constructions as well as at calculation of fire risk, too. When describing a seat of fire there are used fire hazard indicators having essential uncertainty according to the technical literature sources and experimental data while formation should be based on the possibility of their thermodestruction and thermooxidation under the influence of heat loads of various intensity. At the same time, the speed of the specified processes should be interconnected with values of heat loads. The presented work is of current importance because it is necessary to describe thermodestruction and thermooxidation processes of fire load material at modeling the dynamics of HFF distribution in buildings and constructions by means of kinetic parameters received as the results of thermogravimetric analysis. On the example of calcium silicate and wood composition there are carried out calculations of HFF distribution in a test premise taking into account the contribution of wall and ceiling facing material. There is shown the prevailing, in comparison with a seat of fire, contribution of wall and ceiling facing material to HFF formation at its initial stage which is especially important from the point of view of ensuring safe evacuation of people at fire in buildings and constructions. On the basis of the conducted analysis of research results there are developed proposals for applying the considered approach to model conditions for (standard and non-standard) tests of building materials and structures for fire hazard (for example, front systems) and flexible rationing of use of decorative - finishing and facing materials as well as floor coverings in buildings and structures.

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Process of Obtaining Chromium Nitride in the Combustion Mode under Conditions of Co-Flow Filtration

Processes ◽

10.3390/pr8091056 ◽

2020 ◽

Vol 8 (9) ◽

pp. 1056

Author(s):

Nikolay Evseev ◽

Mansur Ziatdinov ◽

Vladimir Romandin ◽

Alexander Zhukov ◽

Aidos Tolynbekov ◽

...

Keyword(s):

Gas Flow ◽

Combustion Process ◽

Combustion Products ◽

Chromium Nitride ◽

Gas Flow Rate ◽

Chromium Powder ◽

Burning Temperature ◽

Superadiabatic Heating ◽

Argon Mixture ◽

Flow Filtration

In this work, the combustion process of chromium powder in the co-flow filtration mode was studied. The effect of nitrogen-containing gas flow rate on the nitridation of combustion products is shown. The effect of the amount of argon in the nitrogen–argon mixture on the burning rate and the burning temperature of the chromium powder is shown. It was found that an increase in the percentage of argon in the nitrogen–argon mixture can lead to the formation of an inverse combustion wave. The actual burning temperature is higher than adiabatic burning temperature in the co-flow filtration mode, thus the phenomenon of superadiabatic heating is observed. The phase composition of the obtained combustion products was studied. It was shown that the forced filtration mode allows for synthesizing non-stoichiometric Cr2N nitride.

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