Localization and reduction of accident consequences during deflagration and explosion

2021 ◽  
pp. 42-46
Author(s):  
Леонид Петрович Вогман ◽  
Иван Ардашевич Болодьян ◽  
Евгений Николаевич Простов ◽  
Дмитрий Александрович Бритиков
Keyword(s):  
High Speed ◽  
Residential Buildings ◽  
Combustion Process ◽  
Process Intensification ◽  
Fuel Mixture ◽  
Combustion Products ◽  
Fire Spread ◽  
Inert Gases ◽  
Industrial Facilities ◽  
Gas Dynamic

Ранее нами был рассмотрен вопрос о целесообразности более четкой дифференциации процессов горения горючих газо-, паро- и пылевоздушных смесей по показателям горения и критериям, характеризующим последствия аварий, сопровождающихся пожарами и взрывами, также было введено понятие «повышенная дефлаграция» («хлопк»). Такой подход может способствовать устранению коллизий в вопросах определения последствий аварий на объектах защиты, а также исключению различных толкований применимости как для промышленных объектов, так и для жилых зданий мероприятий по обеспечению их пожаровзрывобезопасности. В настоящей работе поставлена обратная задача: исследование закономерностей локализации роста давления при взрыве до критически приемлемых значений, представление средств и способов достижения минимизации последствий аварий и взрывов в зданиях и помещениях. In previously published work there was considered the question of reasonability of differentiation of the combustion processes of combustible mixtures according to combustion parameters and criteria characterizing the accident consequences of involving fires and explosions. The concept of enhanced deflagration (clap) was introduced. Such approach can help to eliminate conflicts in determining the accident consequences at objects of protection, as well as to exclude different interpretations of the applicability of fire and explosion safety measures for both industrial facilities and residential buildings. The task of this paper is to study the regularities of localization of pressure growth during an explosion to critically acceptable values, as well as to present the means and methods for achieving minimization of the accident consequences and explosions in buildings and premises. The flame spreads unevenly with acceleration or deceleration depending on the composition of the fuel mixture, gas dynamic conditions of combustion propagation and other factors. The combustion process intensification in closed volumes is caused by turbulization of the flame due to the influence of gas-dynamic disturbances of various nature on the flame front and is characterized by the coefficient of intensification or turbulization. Safety structures designed to prevent the propagation of explosive wave in a room are the following: glazing; easy-to-throw lightweight wall panels; lightweight coatings. The glazing is the most widely used as easy-to-throw structures both in housing and in industrial premises. The most practical and quite effective is the use of safety structures in the form of glazed window openings with design characteristics that reduce the excess pressure of the shock wave. These measures are not sufficient for industrial facilities. Such measures should include the following: space-planning and design solutions aimed at limiting the spread of fires and the consequences of explosions (for example, limiting the possibility of fire spread (explosion) to neighboring rooms and stairwells by installing vestibule locks); using equipment that prevents the spread of flames and combustion products along production lines; application of systems for combustion and explosion localization in equipment using high-speed devices, fire-prevention and check valves, fire barriers, means of supplying inert gases to it and to product pipelines, phlegmatizing additives or other technical means that prevent the formation of fire-explosive mixtures and their explosion in the presence of an initiation source; protection of equipment and industrial premises from destruction in explosion using explosion dischargers and easy-to-throw structures; use of equipment designed for explosion pressure.

scholarly journals Effect of Fuel and Air Dilution on Syngas Combustion in an Optical SI Engine

Energies ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1566 ◽  
Author(s):  
S.D. Martinez-Boggio ◽  
S.S. Merola ◽  
P. Teixeira Lacava ◽  
A. Irimescu ◽  
P.L. Curto-Risso
Keyword(s):  
Internal Combustion Engines ◽  
Combustion Process ◽  
Visible Spectrum ◽  
Propagation Speed ◽  
Fuel Mixture ◽  
Operating Conditions ◽  
Inert Gases ◽  
Pollutant Emissions ◽  
Si Engine ◽  
Lean Burn

To mitigate the increasing concentration of carbon dioxide in the atmosphere, energy production processes must change from fossil to renewable resources. Bioenergy utilization from agricultural residues can be a step towards achieving this goal. Syngas (fuel obtained from biomass gasification) has been proved to have the potential of replacing fossil fuels in stationary internal combustion engines (ICEs). The processes associated with switching from traditional fuels to alternatives have always led to intense research efforts in order to have a broad understanding of the behavior of the engine in all operating conditions. In particular, attention needs to be focused on fuels containing relatively high concentrations of hydrogen, due to its faster propagation speed with respect to traditional fossil energy sources. Therefore, a combustion study was performed in a research optical SI engine, for a comparison between a well-established fuel such as methane (the main component of natural gas) and syngas. The main goal of this work is to study the effect of inert gases in the fuel mixture and that of air dilution during lean fuelling. Thus, two pure syngas blends (mixtures of CO and H2) and their respective diluted mixtures (CO and H2 with 50vol% of inert gases, CO2 and N2) were tested in several air-fuel ratios (stoichiometric to lean burn conditions). Initially, the combustion process was studied in detail by traditional thermodynamic analysis and then optical diagnostics were applied thanks to the optical access through the piston crown. Specifically, images were taken in the UV-visible spectrum of the entire cycle to follow the propagation of the flame front. The results show that hydrogen promotes flame propagation and reduces its distortion, as well as resulting in flames evolving closer to the spark plug. All syngas blends show a stable combustion process, even in conditions of high air and fuel dilution. In the leanest case, real syngas mixtures present a decrease in terms of performance due to significant reduction in volumetric efficiency. However, this condition strongly decreases pollutant emissions, with nitrogen oxide (NOx) concentrations almost negligible.

Investigation of Cycle-to-Cycle Variation of In-Cylinder Engine Swirl Flow Fields Using Quadruple Proper Orthogonal Decomposition

2017 ◽  
Vol 139 (7) ◽  
Author(s):  
Penghui Ge ◽  
David L. S. Hung
Keyword(s):  
Proper Orthogonal Decomposition ◽  
High Speed ◽  
Combustion Process ◽  
Flow Characteristics ◽  
Propagation Speed ◽  
Fuel Mixture ◽  
Flow Fields ◽  
Swirl Flow ◽  
Orthogonal Decomposition ◽  
Proper Orthogonal

It has been observed that the swirl characteristics of in-cylinder air flow in a spark ignition direct injection (SIDI) engine affect the fuel spray dispersion and flame propagation speed, impacting the fuel mixture formation and combustion process under high swirl conditions. In addition, the cycle-to-cycle variations (CCVs) of swirl flow often degrade the air–fuel mixing and combustion quality in the cylinder. In this study, the 2D flow structure along a swirl plane at 30 mm below the injector tip was recorded using high-speed particle image velocimetry (PIV) in a four-valve optical SIDI engine under high swirl condition. Quadruple proper orthogonal decomposition (POD) was used to investigate the cycle-to-cycle variations of 200 consecutive cycles. The flow fields were analyzed by dividing the swirl plane into four zones along the measured swirl plane according to the positions of intake and exhaust valves in the cylinder head. Experimental results revealed that the coefficient of variation (COV) of the quadruple POD mode coefficients could be used to estimate the cycle-to-cycle variations at a specific crank angle. The dominant structure was represented by the first POD mode in which its kinetic energy could be correlated with the motions of the intake valves. Moreover, higher order flow variations were closely related to the flow stability at different zones. In summary, quadruple POD provides another meaningful way to understand the intake swirl impact on the cycle-to-cycle variations of the in-cylinder flow characteristics in SIDI engine.

Performance Testing of 5cc Glow-Ignition Four-Stroke Engine

2007 ◽  
Author(s):  
Toshinori Ogawa ◽  
Yasuo Kawaguchi
Keyword(s):  
Energy Density ◽  
High Speed ◽  
Combustion Process ◽  
Weight Ratio ◽  
Performance Testing ◽  
Fuel Mixture ◽  
Spark Ignition Engine ◽  
Power Sources ◽  
Ignition System ◽  
Stroke Engine

Although portable electric devices have become increasingly sophisticated and compact, the amount of energy required for their operation has increased and device performance may be restrained by the energy source in the near future. A small power source is also needed for mobile robots for home usage. Small, portable distributed power sources with higher energy density than the conventional battery are required. Since the energy density of hydrocarbon or hydrogen fuel is quite high compared to the battery, combustion micro engines that use these fuels are promising for this purpose. In this research, we focused on the small glow-ignition engine developed for model airplanes. Since the glow engine does not require an auxiliary electric circuit for ignition, it is suitable for lightweight miniature engines. However, unlike the spark-ignition engine, there is no equipment that controls the ignition timing. In the glow-ignition system, heat is supplied by the following three methods for ignition of the air-fuel mixture: (1) Heat produced from the compression of the air-fuel mixture; (2) Heat remaining in the element from the last explosion; and (3) Heat produced by the catalytic action of an ignition element. In such an ignition system, the combustion state may differ between cycles. In order to clarify the combustion process, a miniature pressure sensor was built into the cylinder head, and pressure fluctuation was measured. Analysis was conducted to detect cycle-to-cycle variation. The base engine used was a commercial glow-ignition four-stroke engine with a swept volume of 4.89 cc. This is a high-speed engine with a maximum engine speed exceeding 14,000 rpm. Although the nominal output was 368 W, the value measured by this research was much lower. Fuel consumption was measured by placing a fuel tank on an electronic balance. The fuel used for the experiment consisted of mainly methanol, nitromethane, and lubricant. Weight ratio of these components and air/fuel ratio were changed independently, and the effect on the combustion pressure was evaluated.

Investigation of Cycle-to-Cycle Variation of In-Cylinder Engine Swirl Flow Fields Using Quadruple Proper Orthogonal Decomposition

2016 ◽  
Author(s):  
Penghui Ge ◽  
David L. S. Hung
Keyword(s):  
Proper Orthogonal Decomposition ◽  
High Speed ◽  
Combustion Process ◽  
Propagation Speed ◽  
Fuel Mixture ◽  
Flow Fields ◽  
Swirl Flow ◽  
Orthogonal Decomposition ◽  
Fuel Spray ◽  
Proper Orthogonal

It has been observed that the swirl characteristics of in-cylinder air flow in a spark ignition direct-injection (SIDI) affect the fuel spray dispersion and flame propagation speed, impacting the fuel mixture formation and combustion process under higher conditions. In addition, the cycle-to-cycle variations of swirl flow often degrade the fuel spray mixing and combustion quality in the cylinder. In this study, the 2D flow structure along a swirl plane at 30 mm below the injector tip was recorded using high-speed particle image velocimetry in a four-valve optical SIDI engine under high swirl condition. Quadruple proper orthogonal decomposition (POD) was used to investigate the cycle-to-cycle variations of 200 consecutive cycles during the intake and compression strokes. The flow fields were analyzed by dividing the swirl plane into four zones along the measured swirl plane according to the positions of intake and exhaust valves in the cylinder head. Experimental results revealed that the coefficient of variation (COV) of the time coefficients of the quadruple POD mode coefficients could be used to estimate the cycle-to-cycle variations at a specific crank angle. The dominant structure was represented by the first POD mode in which its kinetic energy could be correlated with the motions of the intake valve. Moreover, the higher order flow variations were closely related to the flow stability at different zones. In summary, quadruple POD provides another meaningful way to understand the intake swirl impact on the cycle-to-cycle variations of the in-cylinder flow characteristics in SIDI engine.

scholarly journals Modeling of fuel combustion in boilers of large and small capacity to reduce the toxicity of combustion products

2020 ◽  
Vol 13 (3) ◽  
pp. 188-196
Author(s):  
E. S. Zheltukhina ◽  
M. V. Pavlova ◽  
M. G. Ziganshin
Keyword(s):  
Stokes Equations ◽  
Residential Buildings ◽  
Coal Dust ◽  
Combustion Process ◽  
Combustion Products ◽  
Hot Water ◽  
Atmospheric Pollutants ◽  
Household Waste ◽  
Navier Stokes ◽  
The Individual

The issues related to the emission of atmospheric pollutants during the provision of energy supply services and the circulation of household waste in settlements are considered. The ways of air pollution of the residential area with toxic compounds, which are form by the existing methods of heat treatment of waste and during the operation of individual sources of heat supply for residential buildings, are analyzed. The issues of reducing the content of toxic emissions in combustion products are studied based on a numerical experiment using Computational Fluid Dynamics (CFD). Furnace processes in the energy boiler TP-14A (E 220/100) and the individual hot water boiler Vitocrossal 200 VIESSMANN are considered. The appropriate boundary conditions for the processes of aerodynamics, heat exchange and combustion of gas fuel have been defined. Numerical researches were carried out based on the Reynolds-averaged Navier-Stokes equations (RANS), with the closure of the equations using the two-parameter k-ε model. The combustion process was modeled as the transport of reactants Species Transport. The combustion calculations were performed using the Eddy-dissipation model. The scheme of a one-stage oxidation reaction to the final products of CO2 and H2O, the initial gaseous fuel — methane for the VIESSMANN Vitocrossal 200 boiler, and the products of coal dust gasification for the TP-14A boiler was used. The temperature, velocity and concentration fields in the boiler fireboxes have been determined. Based on the results of the calculations performed, the formation of chemical underburning and nitrogen oxides is predicted. The possibilities of numerical modeling of such processes are shown based on new directions in Chemkin modeling technology and the application of the ISAT algorithm. It is noted that they are also promising for modeling the kinetics of combustion processes using household waste as a fuel, but in this area of research, their application is still strongly limited by the computing power of available processors.

scholarly journals Gas dynamic calculation of detonation in constant-cross-section ducts

2019 ◽  
Vol 18 (3) ◽  
pp. 48-58
Author(s):  
A. V. Grigoriev ◽  
O. A. Rudakov ◽  
A. V. Solovieva
Keyword(s):  
Shock Wave ◽  
Cross Section ◽  
Initial Conditions ◽  
Fuel Mixture ◽  
Combustion Products ◽  
Computational Method ◽  
Clear Correlation ◽  
Gas Dynamic ◽  
Uniform Cross Section ◽  
Specific Speed

The paper presents a computational method with the use of gas-dynamic functions of parameters of detonation in a one-dimensional subsonic flow of ideal gas behind the shock wave propagating in chemically active air-and-fuel mixture in a uniform-cross-section duct, where the resultant of normal pressure forces acting on its side surface is equal to zero. Stabilization of the shock wave is provided by the onset of thermal crisis with the air-and-fuel mixture combustion heat supply to the gas behind the wave. In this case the value of the specific speed of the combustion products is equal to the critical one. The solution of the total-impulse equation considering the above mentioned peculiarities of the flow in a uniform-cross-section duct establishes clear correlation of the specific speed of the stabilized shock wave to the rate of rise of the temperature of the gas behind it, which gives an opportunity to determine all detonation parameters. The shock wave can be initiated by the detonation of an explosive substance and carries a huge amount of energy. It is shown that the shock wave can be obtained only if the source of small disturbances itself moves at the supersonic speed. It is shown that total pressure behind the shock wave decreases significantly and the entropy increases due to the wave losses, whereas the static pressure increases significantly. An explanation of this effect is given. A formula for calculating the rate of gas temperature rise was derived as a function of the specific speed of the shock wave, the air-and-fuel mixture heat value and the heat availability factor that designates the dissociation of the combustion products and heat loss through the duct wall under specified initial conditions. The reliability of the method of calculating detonation was experimentally substantiated. The work is currently important for the evaluation of the detonation engine efficiency.

High Speed Combustion Imaging in a Large Bore Gas Engine: The Relationship Between Pre- and Main Chamber Heat Release

2013 ◽  
Author(s):  
Jeudi Duong ◽  
Rikard Wellander ◽  
Jari Hyvönen ◽  
Öivind Andersson ◽  
Mattias Richter ◽  
...  
Keyword(s):  
Heat Release ◽  
Combustion Chamber ◽  
Flame Propagation ◽  
High Speed ◽  
Combustion Process ◽  
Fuel Mixture ◽  
Video Camera ◽  
Main Chamber ◽  
Lean Burn ◽  
Combustion Heat

An experimental study is carried out to investigate the combustion process in a Wärtsilä 34SG spark-ignited lean burn four-stroke large bore engine (bore 340 mm) by means of optical diagnostics when operating on natural gas. The main focus of this work is to gain knowledge about in-cylinder combustion phenomena when igniting a lean air/fuel mixture with pre-combustion chamber induced jets. Especially the origin of cyclic variability is of interest. The flame propagation process in a single cycle was captured using a high speed video camera. The analysis is based on apparent heat release rates in the pre-combustion chamber and main chamber, in order to find correlations with the imaged phenomena. The results show that the flame propagation inside the main chamber starts at the end of the pre-chamber combustion heat release and that variation in main chamber heat release does not correlate with variations in the pre-combustion chamber.

EMISSION OF POLYCYCLIC AROMATIC HYDROCARBONS CONTAINED IN COMBUSTION PRODUCTS OF GASOLINE ENGINES

2018 ◽  
Vol 62 (3) ◽  
pp. 341-346 ◽  
Author(s):  
M. Assad ◽  
V. V. Grushevski ◽  
O. G. Penyazkov ◽  
I. N. Tarasenko
Keyword(s):  
Polycyclic Aromatic Hydrocarbons ◽  
Aromatic Hydrocarbons ◽  
High Speed ◽  
Internal Combustion Engines ◽  
Catalytic Converter ◽  
Combustion Products ◽  
Chromatography Method ◽  
Exhaust Gases ◽  
Polycyclic Aromatic ◽  
Load Mode

The concentration of 16 polycyclic aromatic hydrocarbons (PAHs) in the gasoline combustion products emitted into the atmosphere by internal combustion engines (ICE) has been measured using the gas chromatography method. The concentrations of PAHs in the exhaust gases sampled behind a catalytic converter has been determined when the ICE operates in five modes: idle mode, high speed mode, load mode, ICE cold start mode (engine warm-up) and transient mode. Using 92 RON, 95 RON and 98 RON gasoline the effect of the octane number of gasoline on the PAHs content in the exhaust gases has been revealed. The concentration of the most carcinogenic component (benzo(α)pyrene) in the exhaust gases behind a catalytic converter significantly exceeds a reference value of benzo(α)pyrene in the atmospheric air established by the WHO and the EU for ICE in the load mode.

scholarly journals Modeling the Excess Velocity of Low-Viscous Taylor Droplets in Square Microchannels

Fluids ◽  
2019 ◽  
Vol 4 (3) ◽  
pp. 162 ◽  
Author(s):  
Thorben Helmers ◽  
Philip Kemper ◽  
Jorg Thöming ◽  
Ulrich Mießner
Keyword(s):  
High Speed ◽  
Process Intensification ◽  
Continuous Phase ◽  
Channel Cross Section ◽  
Optimization Approach ◽  
Mean Flow ◽  
Bypass Flow ◽  
Wall Film ◽  
Proposed Model ◽  
The Mean

Microscopic multiphase flows have gained broad interest due to their capability to transfer processes into new operational windows and achieving significant process intensification. However, the hydrodynamic behavior of Taylor droplets is not yet entirely understood. In this work, we introduce a model to determine the excess velocity of Taylor droplets in square microchannels. This velocity difference between the droplet and the total superficial velocity of the flow has a direct influence on the droplet residence time and is linked to the pressure drop. Since the droplet does not occupy the entire channel cross-section, it enables the continuous phase to bypass the droplet through the corners. A consideration of the continuity equation generally relates the excess velocity to the mean flow velocity. We base the quantification of the bypass flow on a correlation for the droplet cap deformation from its static shape. The cap deformation reveals the forces of the flowing liquids exerted onto the interface and allows estimating the local driving pressure gradient for the bypass flow. The characterizing parameters are identified as the bypass length, the wall film thickness, the viscosity ratio between both phases and the C a number. The proposed model is adapted with a stochastic, metaheuristic optimization approach based on genetic algorithms. In addition, our model was successfully verified with high-speed camera measurements and published empirical data.

Sign in / Sign up

Export Citation Format

Share Document